Trends Sci. 2025; 22(6): 9592

Introduction

The global population seems to be increasing at the same time that industrialization and agriculture do. Uncontrolled uses of pesticides, herbicides, and chlorinated organic poisons, as well as organic hydrocarbon compounds that leak into the environment and contaminate water are some of the effects of this reality. Since nanoparticles molecular activity can have an impact on living things, the most notable aspect of nanotechnology is its application in biology and biological systems, despite the field’s apparent advancements in medicine being very amazing. Consequently, the potential for using nanoparticles in illness diagnosis and treatment has been made possible by their special qualities [1].

Nanotechnology in material science refers to the creation of nanoparticles with specific properties by the use of physical or chemical techniques. These materials have unique physical, chemical, thermal, and electrical properties allow them to be used in a broad range of fields, including electronics, agriculture, health care, and environmental management. Using various chemical materials, which are dangerous for people and the environment is one of the challenges in the production of metal oxide nanoparticles [2]. Greener synthesis and bio synthesis of nanoparticles is a significant development method in nanotechnology at the moment [3]. Numerous researchers have documented diverse methods for producing metal oxide nanoparticles using a range of biological sources, including fungi and bacteria [4]. One of the active areas of nano biotechnology study in the current world is the green chemistry approach of plant intermediation [5,6].

Plants are the best source of raw materials for creating metal oxide nanoparticles among the various bio-sources, due to their protein content, availability, simplicity, antioxidant capability, and non-toxicity. Variety of plant extracts can be used as stabilizing, capping, and reducing agents for the production of metal oxide nanoparticles. The application of plant extracts can prove to be highly advantageous as they can function as reducing agents throughout the production process and encourage the development of more biocompatible nanostructures [7,8]. It can be suggested that the application of green technology can reduce the usage of high-risk reagents and solvents [9], as well as increase the energy efficiency and materials in the chemical processes of improvement and design of non-toxic products [10], given that the reaction rate has been observed to be quite fast and that special conditions are not required in this procedure. It has been shown that using plant extracts is more advantageous method to prepare metal oxide nanoparticles [11]. It has long been believed that plants and crops are a rare and reasonably priced source for the synthesis of biological nanomaterials [12]. The MONP’s prepared from the green synthesis involves many advantages like enhanced properties (improved stability, bio compatibility), cost effective (inexpensive raw materials, simple synthesis), sustainability (renewable resources, less water) and have versatile application in all fields (Figure 1).

Metal oxides are ionic compositions that contain positively charged metal ions and negatively charged oxygen ions, which can function as conductors or semiconductors. One of the best multifunctional materials is semiconductor nanoparticles, which have remarkable physio-chemical properties including high chemical stability, high electrochemical coupling coefficient, broad radiation absorption range, and high light stability [13,14]. Due to this type of properties the researchers are seem to be interested towards nanosized semiconductor metal oxides which are very helpful in creating multifunctional nanoscale optoelectronic and electronic devices and they also mainly used for the gas sensing applications.

From the foregoing discussion, the production of metal oxide nanoparticles using green chemistry principles has gained popularity. The main objectives and alignment of this review about the preparation of metal oxide nanoparticles such as FeO, ZnO, CoO, NiO, CuO, TiO₂ and MgO by using variety of plant extracts and discussion about their biological applications in the fields of anti-cancer, anti-oxidant and others.

Figure 1 Contribution of MONPs in different field.

Metal oxides nanoparticles semiconductors (MONP’s)

The semiconductors are the materials which shows the property between the conductor and insulator. The semiconductor was normally an insulator until the electron crosses the valence band to conduction band. The distance between the bands is known as band gap. All semiconductors have a different band gap. Quantum dot semiconductor structures have been of the most motivating materials in optoelectronic devices due to their unique properties such as spiked density of state, low temperature sensitivity, high data transmission rate, low threshold current (Figure 2) [15]. The metal oxide nanoparticles (MONP’s) can be used as the semiconductors because of its adjustable band gap, MONPs can be used in a wide range of semiconductor applications. MONPs semiconductors have many advantages like low toxicity, cost effectiveness, bio compatibility, energy efficiency and scalability.

One of the best multifunctional materials is semiconductor nanoparticles, which have remarkable physio-chemical properties, which contains positively charged metal ions and negatively charged oxygen ions, which can function as semiconductors [13,14]. The developments of this metal oxide nanoparticles semiconductors will be focusing on the main aspects like refining of synthetic methods, improving the surface functions and by creating a hybrid materials like bimetal oxides, nanocomposites to enhance its efficiency. Nano scale semiconductors showed potent activity, by increasing its surface area, improving their electrical conductivity, and reducing their power consumption [16].

Figure 2 TEM images for the active region of QD samples [15].

This metal oxide nano particles offers unique properties like tunable band gap (very important character of the semiconductor), high surface area, size dependent behavior allows for the significant advancement in semiconductor industry. With the continued innovation and advancements leads to the production of efficient metal oxide nanoparticles semiconductors which dictates the future in the fields of semi conducting technologies, environmental remediation, energy applications, smart sensing systems and some biological applications.

Similarly, recent progress in QD lasers grown in silicon is reviewed, focusing on QD lasers in terms of threshold current density, output optical power, emission wavelengths, and operation temperatures. The future of QD lasers monolithically grown on Si-substrate and their application are also discussed in the literature [17,18]. The scope of III-V compound semiconductors heterogeneously integrated on Si substrates. The commercial success of massively produced integrated optical transceivers based on first-generation innovation is discussed [19].

For uses such as gas detection and catalysis, their huge surface area improves their reactivity and sensitivity. MONPs have special optical qualities that are helpful in optoelectronic devices, like photoluminescence. Recently air pollution grown to be a serious hazard to both people and the environment. Semiconductor metal oxide nanoparticles such as ZnO, TiO₂, CeO₂, SnO₂, In₂O₃, CuO, NiO, WO₃, and Fe₃O₄, are used in the sensing applications for the air pollution [20]. Researchers are seen to be interested towards nanosized semiconductor metal oxides because of their electrical and optical characteristics, which are very helpful in creating multifunctional nanoscale optoelectronic and electronic devices. This chapter highlights the production of metal oxides nanoparticles semiconductors produced form metal oxides in a greener way by using various plant extracts.

Advantages of using plant extracts in nanoparticle synthesis

With the objective to create harmless and environmentally beneficial nano assemblies to address issues impacting the environment or public health, green nanotechnology combines the concepts of green chemistry and ecological engineering. The toxicity and risk of nanoparticles remain a major worry despite significant advancements in the field of nanotechnology. Here, the concept of “green nanotechnology” progressively becomes apparent in order to address the potential risks associated with nanotechnology. Simple, affordable, environmentally safe, and easily accessible raw materials are used in the green synthesis process, which also uses fewer processes and no hazardous chemicals or byproducts (Figure 3). The goal of green nanotechnology is to completely remove any harmful materials from the production process. One noteworthy aspect of green nanotechnology is the application of plant-derived phytochemicals as stabilizing and reducing agents during the conversion of metal ions into metallic nanoparticles.

With the help of plant extracts, it is possible to control the synthesis of nanoparticles and obtain well-defined sizes and morphologies in a single step with a high yield. Several bioactive substances can be found in the seeds, leaves, and stems of medicinal plants. These discovered substances include flavonoids, amides, alkaloids, saponins, glycosides, terpenoids, and tannins. These materials serve as reducing and capping agents throughout the nanoparticle production process.

Figure 3 Advantages of green synthesis.

Plants are readily accessible and safe to handle, scientists have placed a great deal of attention on using plant extracts in the creation of nanoparticles. Applications for MONPs (Metal oxide Nanoparticles) are numerous and include drug delivery systems, catalysts, active food packaging materials, parts for nano-biosensor construction, gene transfer systems, antibiotics, antiseptics, disinfectants, and pathogen and pest control solutions, as well as nanoelectronic components. When using plant-mediated methods, biosynthesis proceeds at a faster pace than environmentally when using methods focused on microorganisms, and the resultant nanoparticles (NPs) are more stable and varied in size and shape. Because they are easy to use, inexpensive, and environmentally beneficial for producing large quantities of NPs in a short amount of time, plant extracts are frequently used in the green synthesis of metal-based NPs [21]. In order to create nanoparticles (NPs), extracted phytochemicals are added to metal salt solutions, where they lower the metal ions and connect to the NPs to serve as capping or stabilizing agents. These non-toxic capping agents stop NPs from aggregating. Furthermore, there is better control over the formation of NP crystals using biological methods due their kinetics are slower than those of chemical approaches [22-25].

Synthesis in sustainable chemistry

Plant-mediated green synthesis methods create metal oxide nanoparticles (NPs) of various sizes and shapes using various plant parts, including the seed, fruit, callus, bark, stem, flowers, and leaves [26]. During the creation of nanoparticles, a variety of metabolites included in plant extracts that function as stabilizing and reducing agents. The complexity of the bio reduction process is widely acknowledged. By giving the metal ions electrons, the biomolecules in the extract operate as a reducing agent, causing the metal ions to be reduced to the elemental metal. After the produced atoms function as a nucleation site, nearby smaller particles unite to form larger NPs during a growth phase. To this end, plant extracts can stabilize NPs during the last phase of synthesis, which in turn determines their desirable and energetically stable form. Additionally, a capping agent is added to prevent further growth and keep the particle in the nanoscale region. Therefore, the plant extract’s biomolecules can operate as reducing agents or double as capping agents and reducing agents [27,28] (Figure 4).

Figure 4 Schematic Synthesis of Metal Oxide from plant extract and its applications.

Synthesis and biological applications of some metal oxide nanoparticles

Iron oxide

Iron oxide has considerable changeable oxidation states, crystal structures, cheap cost, and magnetic properties. It has been one of the transition metal oxides, which has been studied the most [29,30]. In the biomedical fields iron nanoparticles used in magnetic recording media, nonlinear optical systems, magnetic shielding, immunoassays, magnetic targeted site-specific drug delivery, safe labeling of endothelial progenitor cells, environmental remediation, food analysis, microwave absorbers, and electromagnetic interference shielding [31-36]. Only limited studies in the antibacterial properties of iron oxide NPs have been published reported [37,38]. Devi et al. [39] explain the green aqueous phase production of iron oxide nanoparticles using Platanus orientalis leaf extract, which possessed good anti-microbial activity against Aspergillus niger and Mucor piriformis and M. piriformi. The green manufacture of magnetic iron oxide nanoparticles (Fe₃O₄ NPs) uses leaf extract from Euphorbia herita. In particular, polyphenols and alcoholic compounds are important phytochemicals in the production of magnetic iron oxide nanoparticles [40]. When the produced iron oxide nanoparticles were tested for antibacterial activity against a variety of bacterial and fungal pathogens, the results of the investigation were quite encouraging [40].

Iron oxide NP’s like FeO, magnetite (Fe₃O₄) is prepared by the green synthesis (plant extract) have some biological properties that conventionally synthesized FeO NP’s lacks. They have biological properties like, good biocompatibility because greenly produced IONPs are often non-toxic, which qualifies them for use in biological applications. Biological systems frequently tolerate these nanoparticles well, which lowers the possibility of negative effects.

Yusefi et al. used the plant peel extract of Punica Granatum for the preparation of FeONP’s and analyzed its anti-cancer activities in various cancer cell lines like colon (HCT116), breast (MCF7), cervical (HeLa) and lung (A549) cancer cell lines and 2 normal cell lines derived from human colon and kidney (CCD112 and HEK293) [41].

Manimaran et al. synthesized the FeONP from the Pleurotus citrinopileatus extract (mushroom extract) and evaluated its anti-bacterial and anti-cancer activity. It was discovered that the FeONPs anticancer efficiency (MG-65) was expressed by an IC₅₀ value of 55.63 µg/mL [42]. Sriramula et al. used the extract of Aegle marmelos for the synthesis of FeONP and studied their bacterial properties by using the NP against the bacteria like E. coli and S. aureus at and compared with Streptomycin and reported that these NP’s have good anti-bacterial property [43]. Abdullah et al. synthesized the Fe₂O₃, Fe₃O₄-NPs nanoparticles from the pheonix dactylifera leaf extract form the green synthesis and the compounds showed good anti-oxidant properties [44]. Ustun et al. used the Ficus Carica Leaf Extract for the green synthesis of FeO NP’s for the application of anti-oxidant studies [154]. Kuldeep Singh et al. used the leaf extract of Coriandrum sativum L. for the synthesis of FeONP’s and studied their anti oxidant property. From their research, iron oxide nanoparticles (50 - 250 mg) showed DPPH radical inhibitory activity from 32.54 to 84.28 %, outperforming ascorbic acid (28.25 to 81.41 %) [45].

Isik et al. studied the anti-microbial property of the FeONP derived from the leaf extract of Centaurea solstitialis leaves [151]. Devi et al. synthesized the FeO NPs from the P. orientalis leaf extract for the green synthesis of FeONP. They subjected this NP to the anti fungal activity against Fungi like A. niger and M. Piriformis which employed as model fungi. But interestingly it shows good anti fungal activity against the M. piriformis (later fungus) [46]. Sriramulu et al. used the leaf extract of Aegle marmelos for the synthesis of FeONP and studied their anti-fungal properties against the fungi like F. Solani (12 ± 0.53 mm) compared with fluconazole (7 ± 0.38) at 30 µg/mL and reported that they showed the good anti fungal activity [153]. From the above we revealed that the plant mediated synthesized iron oxide NPs possessed good biological activity.

Thakur et al. [47] developed magnetic iron nanoparticles from Chenopodium glaucum (CG) and it act as an efficient and recyclable heterogeneous catalyst for one-pot synthesis of xanthene derivatives, yielding products with high yields (up to 97 %) and excellent purity (crystalline form) within a short timeframe (6 min) using microwave irradiations (at 120 W) (Figure 5).

Figure 5 Schematic representation of development of magnetic iron nanoparticles from Chenopodium glaucum (CG) [47].

Zinc oxide nanoparticles (ZnONPs)

Zinc oxide nanoparticles (ZnO NPs) have garnered the most attention among all the metal oxides utilized to create nanoparticles (NPs) because of their appealing characteristics, extensive uses, and environmentally benign makeup [48,49]. Zinc oxide (ZnO) is a kind of semiconducting metal oxide that has garnered interest in the last 2 to 3 years because of its enormous potential for use in biomolecular, microelectronics, optics, biomedical systems, and antimicrobial agent manufacture [50,51]. The structure of bacterial cell membranes can be disrupted by these NPs adhering to them [52]. Because the chemical processes involved in the synthesis of nanomaterials produce a large number of hazardous by products, antibacterial agents produced using novel chemical or physical methods result in the direct absorption of several toxic chemical species onto the surface and may have poor consequences for therapeutic purpose [53,54]. Since green synthesis methods don’t require the use of hazardous chemicals, they are an economical and environmentally beneficial alternative to chemical procedures. In order to employ plants as antimicrobial agents and comprehend the underlying mechanisms of their antibacterial properties, numerous investigations on plants have been conducted [55]. Because of their biocompatibility, zinc oxide nanoparticles have been approved by the Food and Drug Administration (FDA) in the United States and are mostly utilized in the food industry for packaging purposes aimed at extending the shelf life of food [56]. ZnONPs have a high surface area to volume ratio, they are utilized in a number of agromedicinal applications, including those that are antibacterial, antifungal, anti-inflammatory, anti-cancerous, and antidiabetic [57].

The effectiveness of plant extracts in the biogenic synthesis of ZnONPs has been shown for a range of compounds that they include [58]. Nyctanthes arbor-tristis flower extract boosted antifungal and antibacterial properties of ZnONPs against 5 pathogenic fungus and many bacterial species, according to a study by Jamdagni et al. [59]. Given this, every plant extract listed in Tables 1 and 2 has been employed to improve the antibacterial or anticancer properties of these ZnONPs. One significant member of the Fabaceae family is Sutherlandia frutescens (Sf), often known as bush cancer tea [60-62]. It is a powerful and versatile medicinal plant native to Southern Africa. According to Kumar et al. [63], Justicia wynaadensis aqueous leaf extract was used in the biosynthesis of the hexagon-shaped wurtzite nanoparticles. ZnONPs that have been biosynthesized have been tested for their antimitotic qualities using Allium cepa. The findings show that treatment with ZnO-NPs increases chromosomal aberrations, which in turn reduces the number of dividing cells [63]. The green synthesis of ZnO NPs, and Ag/Ag2O/ZnO NCs using polar and apolar extracts of C. vulgaris offers a sustainable and versatile method for producing nanoparticles with customizable properties (Figure 6). The impact of the synthesis environment and the nanomaterials’ characteristics on cytotoxicity was evaluated by examining reactive species production and their effects on mitochondrial bioenergetic [64].

Figure 6 Scheme of the experimental activity involving green synthesis and characterization of metallic NPs using Chlorella vulgaris extracts, as well as tests on PC12 cells using spectrophotometric assays and respirometry analysis [64].

Various zinc oxide nanoparticles (ZnONPs) can be effectively synthesized using various plant extracts [65-67]. Hydroxyl groups can form complexes with zinc, which is one of the ways suggested by which these biomolecules may function in the production of nanoparticles [68]. Therefore, by choosing plant species that contain the proper kind and quantity of biomolecules, it is possible to hypothesize a green synthetic method to produce ZnONPs without having to worry about the negative effects that traditional synthetic procedures have on the environment. Anti-cancer and anti-oxidant activity of the zinc oxide nanoparticles prepared by using various plants were given in Tables 1 and 2.

Table 1 Antioxidant studies for ZnO Nanoparticals prepared from plant extract.

S. No	Plant extract	Assay	Concentration	References
1	Artocarpus gomezianus	DPPH	10.8 mg mL−1	[69]
2	Coccinia abyssinica	DPPH	127.74 µg mL−1	[70]
3	Polygala tenuifolia	DPPH	1 mg mL−1	[71]
4	Cassia fistula	DPPH	2853 µg mL−1	[72]
5	oat extract	DPPH	0.88 ± 0.03 µg mL−1	[73]
6	Myristica fragrans	ABTS, DPPH	400 µg mL−1	[74]
7	Aegle marmelos	ABTS, DPPH	5.75 - 6.78, 4.45 - 5.05 mg mL−1	[75]
8	Scutellaria baicalensis	DPPH	43 µgmL−1	[76]
9	Tecoma castanifolia	DPPH	100 µgmL−1	[77]
10	Trianthema portulacastrum	DPPH	500 µg mL−1	[78]

Table 2 Anticancer activity of ZnO Nanoparticals prepared from plant extract.

S. No	Plant extract	Cancer cell	IC50 value	References
1	Elaeagnus angustifolia	HUH-7 and HepG2	29.8 µg mL−1 21.7 µg mL−1	[79]
2	Anchusa italica	Vero cells	142 µg mL−1	[80]
3	Rosa canina	(A549) cells	> 0.1 mg mL−1	[81]
4	Citrullus colocynthis	3T3 cells	0.258 mg mL−1	[82]
5	Pongamia pinnata	MCF-7	50 µg mL−1	[83]
6	Ziziphus nummularia	HeLa	200 µg mL−1	[84]
7	Mangifera indica	A549 cell lines	25 µg mL−1	[85]
8	Costus pictus	DLA cells	50 µg mL−1	[86]
9	Anacardium occidentale	Hu02	50 µg mL−1	[87]
10	Gracilaria edulis	SiHa cells	35 µg mL−1	[88]

Cobalt oxide nanoparticles

By virtue of the participation of the 3^rd orbital, cobalt has various oxidation states and multi-electronic valences [89]. The most stable cobalt oxides are CoO and Co₃O₄, which are both stable at normal temperature [90]. Gas sensors, drug delivery, energy storage, solid-state sensors, electrochromic devices, magnetic resonance imaging, heterogeneous catalysts, solid-state sensors, and lithium batteries are only a few of the numerous applications [91,92]. In addition to the environmentally friendly synthesis of Co₃O₄ NPs and their biological uses, a number of chemical and physical approaches for their synthesis have been reported [93,94]. In this study, Co₃O₄ NPs were synthesized using the green approach, which is a simpler, more economical, and ecologically friendly method. The Co₃O₄ NPs were prepared by using Aspalathus linearis leaf extract, Punica granatum peel, and Calotropis procera latex [95,96]. The textile dye effluents were observed to exhibit photodegradation when tricobalt tetraoxide (Co₃O₄) was produced using Punica granatum (P. granatum) seed extract [97].

Abbasi et al. used the Rhamnus virgata leaves extract for the synthesis of CoONPs and subjected this NPs for anti cancer activity studies against the various human cancer cell lines. From this study they reported that CoONPs demonstrated potent anticancer activity against human hepatoma HUH-7 (IC₅₀: 33.25 μg/mL) and hepatocellular carcinoma HepG2 (IC₅₀: 11.62 μg/mL) cancer cells in their in vitro cytotoxic experiments [98]. Govindasamy et al. reported the green synthetic technique for the synthesis of CoONPs from the Psidium guajava Leaves Extracts, these NP from the P. guajava have reduced the cell viability of MCF 7 and HCT 116. MTT assay of P. guajava cobalt oxide nanoparticles showed an excellent cytotoxic effect against MCF 7 and HCT 116 cells compared to normal cells [99]. Shanmuganathan et al. used the seed extract of Curcuma longa for the synthesis of CoONPs and to find their anti-cancer potential. They have reported that CL-Cobalt oxide nanoparticles demonstrated anticancer activity against MDA-MB-468 cancer cell lines, with an IC₅₀ value of 150.8 μg/mL [100]. Their anti-bacterial potential in the gram-negative bacteria: Klebsiella pneumoniae, Escherichia coli and gram-positive bacteria: Bacillus subtilis, Staphylococcus aureus. Anupong et al., used the CoO prepared from the orange peel aqueous extract and studied their bacterial activity against the CoNPs showed exceptional antibacterial action against the following bacterial pathogens: Klebsiella pneumoniae, Staphylococcus aureus, Escherichia coli, and Bacillus subtilis and found that they have good anti-bacterial properties [101].

The synthesized CoONPs by using the plant extract acted as a good anti-fungal agent [10]. Anuradha and Raji synthesized the CoONP from the Senna auriculata flower extract to use them as a new anti-fungal agent [101]. Kavica et al. [102] synthesized the CoONP’s with the help of Ziziphus oenopolia leaf Extract as the anti-fungal agent and they proved it by using it as an anti-fungal agent against the fungi like Candida albicans, Candida vulgaris, Aspergillus niger and Aspergillus flavus. Various functional groups present in Psidium guajava leaf extracts are used to stabilize the synthesis of cobalt oxide nanoparticles (Figure 7). The anti-bacterial activity of was evaluated against Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli with a 7 to 18 mm inhibitory zone. The photocatalytic activity was evaluated using green synthesized P. guajava cobalt oxide nanoparticles and observed 79 % of dye degradation [45].

Khalil et al. [100] Sageretia thea (Osbeck) for the synthesis of CoO nano particles and subjected it to various biological studies includes anti-oxidant study. They reported that they have good scavenging activity against DPPH's capacity to scavenge free radicals, moderate lowering power and antioxidant capability.

Figure 7 Synthesis route of cobalt oxide nanoparticles using Psidium guajava leaf extracts [45].

Nickel oxide nanoparticles

Among the various nanomaterials available today are nickel oxide nanoparticles (NiONPs) are important one due to their remarkable stability, remarkable qualities, as well as their many uses—gas sensors, electrochromic devices, solar energy absorbers, and magnetic recording devices—have garnered them a lot of attention. In addition, compared to other metal oxide nanoparticles, NiONPs are extraordinarily affordable, non-toxic, and very stable conductive materials with a broad band gap of 3.6 - 4.0 eV. NiONPs have a significant role in environmental protection because of their efficacious removal of both organic and inorganic contaminants. In the biological field nickel oxide nanoparticles were used in magnetic resonance imaging (MRI) enhancement, magnetic storage data, ferro fluids for biological sample impurity elimination, medication administration, catalysis, pigments, and sensors [106,107]. Further they are acted in supercapacitors [108], magnetic [109], electrochemical performance [110], photocatalyst studies [111], antimicrobial studies [112], and water treatment [113]. Chemical precipitation [108], solvothermal [109], thermal-decomposition [110], precipitation-calcinations [111], and microwave-assisted hydrothermal procedures [112] are some of the techniques used to create NiO nanoparticles.

Uddin et al. [103] synthesized the NiONP’s from the native medicinal plant Berberis balochistanica (BB) leaf extract was used to create nickel oxide nanoparticles (NiONPs). In the production of BB@NiONPs, the extract from BB leaves has multi functions in the NiO synthesis as a potent reducing, stabilizing, and capping agent. Iqbal et al. [104] used the extract of Rhamnus triquetra for the synthesis of NiO nano particles and examine their biological character of the NiONPs. Raj et al. [105] used the leaf extract of Coriandrum sativum for the synthesis of NiONP’s but they used the micro wave assisted technique for this method. Lingaraju et al. [113] used the extract from the Euphorbia heterophylla (L.) as the reducing agent for the NiO synthesis. Through a green synthetic process, nickel oxide nanoparticles (NiO NPs) were created from an extract of E. heterophylla (L.) leaves that functioned as a capping and reducing agent.

Because of its inexpensive precursors and fast preparation time, the plant-extracted microwave method (MM) technique has garnered substantial interest in the fabrication of homogenous, nano-sized functional materials at this moment [114-116]. In addition to being an efficient photocatalyst for the removal of dyes and organic contaminants from waste water, NiO nanoparticles are well-known for their antibacterial activity against a variety of bacterial infections [117]. The green techniques for synthesizing NiONPs using Moringa oleifera plant extract were published by Ezhilarasi et al. [118] which showed potent antibacterial properties against bacterial pathogens and effective cytotoxic activities against HT-29 cancer cells. In the green synthesis of copper-doped nickel oxide nanoparticles using okra plant extract by the sol-gel process reported by the Ghazal et al. [119] which showed good biological activity.

Copper oxide

Due to their superior potentials and numerous uses in biology and medicine, copper oxide nanoparticles, or CuONPs, are of pronounced attention to humans [120-122]. CuONPs have been synthesized using a range of techniques, including the sol-gel method [123], hydrothermal method [124], chemical reduction method [125], precipitation method [121], and sonochemical method [122]. CuONPs simplicity and distinctive optical, electrical, and therapeutic qualities have made them extremely important [126]. When integrated into optical, sensors, electrical, plastics, coatings, textiles, and sensors, CuONPs operate as an antimicrobial, antibiotic, antifungal, and antifouling agent [127,128]. Numerous research publications on the green synthesis of CuONPs utilizing plant leaf extract, including those from Calotropis gigantea [133], Albizia lebbeck [132], Gloriosa superba L. [130], Garcinia mangostana [129], Eclipta prostrata [131], and Azadirachta indica [134], have been published.

Copper oxide nanoparticles (CuONPs) are synthesized at ambient temperature (27 °C) using leaf extracts from Acanthospermum hispidum and Eupatorium odoratum. CuONPs generated alone from Eupatorium odoratum extract showed a good anti-bacterial activity with S. aureus, B. cereus, and E. coli [135]. It has been investigated how biosynthesized CuONPs can limit the growth of gram-positive and gram-negative bacterial strains [136]. Tecoma castanifolia leaf extract was used to create phyto-synthesised CuONPs, which demonstrated consistent bactericidal efficacy and potential utility in biomedical applications [137]. Redox processes involving copper oxide NP can produce ROS such hydrogen peroxide (H₂O₂), superoxide anions (O₂•-), and hydroxyl radicals (•OH). Because of their high reactivity, these ROS have the ability to oxidatively damage lipids, proteins, and DNA in cells. Fenton-like reactions, in which hydrogen peroxide and copper ions combine to form hydroxyl radicals, can be catalyzed by copper. These highly reactive radicals have the potential to seriously harm biological components. Oxidative stress, which is brought on by the production of ROS, can interfere with regular cellular processes and ultimately cause cell lysis and death [138]. Copper oxide nano particles was used in the various biological applications [139], CuO-NiO nanocomposite through microwave–hydrothermal-assisted green synthesis offers several advantages [140] (Figure 8).

Figure 8 Synthetic method of CuO-NiO nanocomposites [140].

Titanium dioxide

Due to its exceptional surface chemistry, great chemical firmness, non-toxicity, and clean photocatalytic nature with excellent morphologies, titanium dioxide (TiO₂NPs) has proven to be a highly valuable material in a variety of fields, particularly in the biomedicine field [141-143]. TiO₂NPs are a substance that is environmentally friendly and has extraordinary biological activity, such as antibacterial [144], antioxidant [145], anti-parasitic [146], and anticancer [147] properties. TiO₂ usefulness is limited by 2 intrinsic properties: A large bandgap and quick electron-hole pair recombination [148,149]. TiO₂ is a stable, recyclable, non-toxic substance with strong catalytic qualities [150].

Goutam et al. used the leaf extract from Jatropha curcas L. for the synthesis of TiO₂NP’s. Here the leaf extract used as the reducing agent which reduces the metals and forms the respective metal oxide and also acts as capping and satbilixing agent in the process [151]. Pushpamalini et al. used the 4 different leaves extract for the synthesis of TiO₂NP’s to find which extract having the good photo catalytic applications. They used the extracts of Piper betel, Ocimum tenuiflorum, Moringa oleifera and Coriandrum sativum [152]. In the synthesis of TiO₂NP’s using the solgel process, the ethanolic extracts of Camellia sinensis, Syzygium aromaticum, and Equisetum arvense functioned as surfactants, altering the growth mechanism and stabilizing the nanoparticles. E. arvense produced the greatest results, resulting in the creation of high-quality, quasi-spherical, non-aggregated TiO₂ nanoparticles with a size range of 20 - 50 nm. The creation of structurally and morphologically uniform nanoparticles was made easier by these extracts [153]. Nevertheless, NaOH is a dangerous chemical compound. Currently, Cinnamomum tamala, Cicer arietinum L., and Carpobrotus acinaciformis can be used as an alternative for the manufacture of TiO₂ nanoparticles [160-162]. However, another plant from Indonesia called Averrhoa bilimbi can also be used to synthesize TiO₂ NPs. It has been specifically noted that Averrhoa bilimbi fruit has some phytochemical elements [163] that may function as a weak base source. From the literature we know that the titanium nanoparticles possessed good biological activity (Table 3). The green synthesis of TiO₂ NPs using non-toxic food-grade TiO₂ and blueberry extract proved cost-effective and aligned with sustainable practices. These TiO₂ NPs demonstrated remarkable photocatalytic activity, achieving approximately 94 % degradation of MG dye within 30 min under direct sunlight and complete degradation within 60 min (Figure 9) [164].

Figure 9 Schematic representation of the green synthesis protocol for TiO₂ NPs using blueberry (Vaccinium corymbosum) extract.

Table 3 Biological activity of TiO₂ Nanoparticles prepared from various plant extracts.

S. No	Plant extract used	Type of TiO2 NP prepared	Biological property	References
1	Acorus calamus	AA@TiO2 NP	Anti-microbial	[154]
2	Mentha arvensis	MA@TiO2 NP	Anti-microbial	[155]
3	Trigonella foenum-graecum	TFG@TiO2 NP	Anti-microbial	[156]
4	Luffa acutangula	LA@TiO2 NP	Anti-microbial	[157]
5	Cynodon Dactylon	CD@TiO2 NP	Anti-cancer	[158]
6	Coleus aromaticus	CA@TiO2 NP	Anti-cancer	[159]
7	Ledebouria revoluta	LR@TiO2 NP	Anti-cancer	[163]
8	Tulbhagia violacea	TV@TiO2 NP	Anti-cancer	[165]
9	Psidium guajava	PG@TiO2 NP	Anti-oxidant	[166]
10	Laurus nobilis	LN@TiO2 NP	Anti-oxidant	[167]
11	Malva parviflora	MP@TiO2 NP	Anti-oxidant	[168]
12	Wrightia tinctoria	WT@TiO2 NP	Anti-oxidant	[169]
13	Azadirachta indica	AI@TiO2 NP	Anti-bacterial	[170]
14	Lippia adoensis	LA@TiO2 NP	Anti-bacterial	[171]
15	Tinospora cordifolia	TC@TiO2 NP	Anti-bacterial	[172]
16	Morus alba	MA@TiO2 NP	Anti-bacterial	[173]
17	Caricaceae papaya	CP@TiO2 NP	Anti-fungal	[174]
18	Trianthema portulacastrum, Chenopodium quinoa	TP@TiO2 NP/CQ@TiO2 NP	Anti-fungal	[175]
19	C. pulcherrima.	CP@TiO2 NP/	Anti-fungal	[176]
20	juniperus phoenicea (L.)	JP@TiO2 NP	Anti-fungal	[177]

Magnesium oxide

MgONPs have drawn more attention because of their outstanding applicability, particularly in the biomedical field, remarkable nontoxicity, and great stability under hard conditions. In addition, MgONPs have a number of advantageous physicochemical properties, including a broad surface area, strong ionic character, oxygen vacancies, and an uncommon crystal shape that facilitates easy interaction with a variety of biological systems. Moreover, it has been applied in biomedicine to cure stomach discomfort, regenerate bone, relieve heartburn, and in several other therapeutic applications, including medications, coated capsules, bio labeling, blood collection vessels, and many more [178].

They have enhanced biocompatibility, biodegradability, high stability, cationic capacity, and redox capabilities in addition to MgONPs characteristics. As a result, they have developed into a compelling substance to fight bacteria and get around problems with removing microbial biofilms and antibiotic resistance [179,180]. The production of reactive oxygen species (ROS), direct interaction with the bacterial cell wall, and the start of intracellular abnormalities like macromolecular interactions (between proteins and DNA) are some of the ways by which it exhibits its antibacterial efficiency [181]. Regarding their synthesis, there are numerous physical and chemical methods for obtaining MgONPs. But in recent years, the greener synthesis has gained favor over the other techniques because the NPs it produces are more stable, safe for the environment, affordable, and non-toxic. Figure 10 provides an explanation of the primary biosources and synthesis methods [182].

Regarding this, Kumar et al. [181] showed how to create MgONPs by using an extract from Camellia sinensis (tea leaves) as a reducing agent. In this instance, the polyphenols required to support the reduction of the metal salt precursor are provided by the tea leaf extract. The produced nanoparticles (NPs) had an average particle size of 65 ± 5 nm and a spherical shape. Extracts from 4 different widely used plants, including Aloe vera, Echeveria elegans, Sansevieria trifasciata, and Sedum morganianum, were evaluated for their ability to facilitate the “green synthesis” of MgO nanoparticles [182]. Various biological activities of the plant mediated synthesized Magnesium oxide nanoparticles have discussed in Table 4 and the obtained data confirmed its biological activity.

Figure 10 Readily available plants used for the synthesis of MgONPs by the “green chemistry” method [182].

Table 4 Biological activity of MgO Nanoparticles prepared from various plant extracts.

S. No	Plant extract used	Type of MgO NP prepared	Biological property	References
1	Ocimum americanum	OA@MgO NP	Anti-microbial	[183]
2	Citrus aurantium	CA@MgO NP	Anti-microbial	[184]
3	Carica papaya	AP@MgO NP	Anti-microbial	[185]
4	Pisonia grandis R. Br.	PG@MgO NP	Anti-microbial	[186]
5	Costus pictus D. Don	CP@MgO NP	Anti-cancer	[187]
6	Caccinia macranthera	CM@MgO NP	Anti-cancer	[188]
7	Oryza sativa L. indica	OS@MgO NP	Anti-cancer	[189]
8	Andrographis paniculata	AP@MgO NP	Anti-cancer	[190]
9	Artemisia abrotanum Herba	AB@MgO NP	Anti-oxidant	[191]
10	Piper nigrum	PN@MgO NP	Anti-oxidant	[192]
11	Piper betle	PB@MgO NP	Anti-oxidant	[193]
12	Magnolia champaca	MC@MgO NP	Anti-oxidant	[194]
13	Pisidium guvajava (P. guvajava)/ Aloe vera (A. vera)	PG@MgO NP/AV@MgO NP	Anti-bacterial	[195]
14	Moringa oleifera	MO@MgO NP	Anti-bacterial	[196]
15	Mangifera indica, Azadirachta indica and Carica papaya	MI@MgO NP/AI@MgO NP/ CP@MgO NP	Anti-bacterial	[197]
16	Lawsonia inermis	LI@MgO NP	Anti-bacterial	[198]
17	Pisonia alba	PA@MgO NP	Anti-fungal	[199]

Conclusions

Form this chapter we can conclude that in what ways phytochemical mediated synthesized metal oxide nanoparticles semiconductors prove them as the efficient biological candidates. Researchers have been paying a lot of attention to nanotechnology lately, particularly in the field of materials science. Moreover, it was determined that there are numerous ways to synthesize NPs chemically and physically, they are also expensive, require high temperatures and pressures, and have an adverse effect on the environment. Among the various synthesis method, green synthesis method is renowned for producing nanoparticles in a fast, easy, safe, affordable, and environmentally friendly manner. The employment of non-toxic solvents and effective production techniques is a significant benefit of green synthesis. Furthermore, the green produced metal or metal oxide nanoparticles have been successfully used in a variety of biomedical applications, including drug delivery, tissue engineering, cancer therapy, and even bioimaging. Utilizing plants or plant extracts has a synergistic impact that is advantageous since it can reduce the amount of toxicity of the compounds.

Research on the factors is still necessary because the plant extracts have the potential to affect the produced materials polydispersity. Furthermore, the majority of these green synthesis methodologies are still in the research phase, necessitating the resolution of their remaining problems such as controlling crystal formation, shape, and size, as well as the stability and aggregation of nanoparticles. When it comes to metal nanoparticles, those made by plants and/or plant extracts are more stable than those made by other creatures.

While many investigations found that metal NPs were less dangerous when the right dosage, size, and distribution are used. However, the challenges like scalability, stability and environmental impact falls in the place, by addressing them and solving these metal oxide nano particles can be the best candidate for the biological applications. Thus, future research still needs to pay close attention to the ecologically sustainable synthesis of nanoparticles and their biological uses.

References

[1] P Pourali, M Baserisalehi, S Afsharnezhad, J Behravan, H Alavi and A Hosseini. Biological synthesis of silver and gold nanoparticles by bacteria in different temperatures (37 °C and 50 °C). Journal of Pure and Applied Microbiology 2012; 6(2), 757-763.

[2] RP Patil, D Sanaei, H Elhouichet, M Iqbal, M Ayyar and H Sharifan. Magnetically retrievable Nb₂O₅/CoFe₂O₄ photocatalysts for degradation of crystal violet dye pollutant under solar irradiation. Inorganic Chemistry Communications 2024; 169, 113073.

[3] CM Boominathan, S Pandiyarajan, SSM Manickaraj, M Ayyar, K Venkatesan, M Selvaraj and HC Chuang. Fabrication of M-type barium ferrite (BaFe₁₂O₁₉) grafted reduced graphene oxide (BF@rGO) nanocomposite using ethyl imidazolium lactate ionic-liquid: An effective electrode modifier for caffeic acid sensor. Ceramics International 2024; 50(11), 18708-18717.

[4] B Ünal, MA Almessiere, A Baykal, Y Slimani, MA Gondal, N Kian-Pour, SE Shirsath, A Manikandan and U Baig. Comprehensive analysis of Ni_0.4Cu_0.2Zn_0.4Fe_2-4xSn_3xO₄ nanospinel ferrites: Structural, electrical, and dielectric characterization through advanced techniques. Ceramics International 2024; 50, 30670-30682.

[5] P Elayarani, T Sumathi, G Sivakumar, S Pragadeswaran, S Suthakaran, S Sathiyamurthy, J Seshadhri, M Ayyar and MV Arularasu. Hydrothermal synthesis of zinc molybdates (α-ZnMoO₄) nanoparticles and its applications of supercapacitor and photocatalytic performances. Zeitschrift Für Physikalische Chemie 2024; 238(6), 1019-1042.

[6] P Kuppusamy, MM Yusoff, GP Maniam and N Govindan. Biosynthesis of metallic nanoparticles using plant derivatives and their new avenues in pharmacological applications - An updated report. Saudi Pharmaceutical Journal 2016; 24(4), 473-484.

[7] K Mohamed, K Zine, K Fahima, E Abdelfattah, SM Sharifudin and K Duduku. NiO nanoparticles induce cytotoxicity mediated through ROS generation and impairing the antioxidant defense in the human lung epithelial cells (A549): Preventive effect of Pistacia lentiscus essential oil. Toxicology Reports 2018; 5, 480-488.

[8] MA Nasseri, F Ahrari and B Zakerinasab. A green biosynthesis of NiO nanoparticles using aqueous extract of Tamarix serotina and their characterization and application. Applied Organometallic Chemistry 2016; 30(12), 978-984.

[9] P Singh, YJ Kim, D Zhang and DC Yang. Biological synthesis of nanoparticles from plants and microorganisms. Trends in Biotechnology 2016; 34(7), 588-599.

[10] FT Thema, E Manikandan, A Gurib-Fakim and M Maaza. Single phase Bunsenite NiO nanoparticles green synthesis by Agathosma betulina natural extract. Journal of Alloys and Compounds 2016; 657, 655-661.

[11] VV Makarov, AJ Love, OV Sinitsyna, SS Makarova, IV Yaminsky, ME Taliansky and NO Kalinina. “Green” nanotechnologies: Synthesis of metal nanoparticles using plants. Acta Naturae 2014; 6(1), 35-44.

[12] KB Narayanan and N Sakthivel. Green synthesis of biogenic metal nanoparticles by terrestrial and aquatic phototrophic and heterotrophic eukaryotes and biocompatible agents. Advances in Colloid and Interface Science 2011; 169(2), 59-79.

[13] K Athira, S Dhanapandian, S Suthakaran and M Ayyar. Facile hydrothermally grown CuO/Co₃O₄ nanocomposite as an effective electrode material for enhanced supercapacitor applications. Journal of Materials Science: Materials in Electronics 2024; 35, 268.

[14] P Rosaiah, P Divya, S Sambasivam, AM Tighezza, V Kalaiyarasi, A Muthukrishnaraj, M Ayyar, T Niyitanga and H Kim. Carbon based manganese oxide (MnO₂, MnO₂/MWCNT and MnO₂/rGO) composite electrodes for high-stability Li-ion batteries. Carbon Letters 2024; 34, 215-225.

[15] MS Al-Ghamdi, RZ Bahnam and IB Karomi. Study and analysis of the optical absorption cross section and energy states broadenings in quantum dot lasers. Heliyon 2022; 8(9), e10587.

[16] A Kumar, G Gupta, K Bapna and DD Shivagan. Semiconductor-metal-oxide-based nano-composites for humidity sensing applications. Materials Research Bulletin 2023; 158, 112053.

[17] RJ Hussin and IB Karomi. Progressing in III-V semiconductor quantum dot lasers grown directly on silicon: A review. Silicon 2024; 16, 5457-5470.

[18] R Koscica, Y Wan, W He, MJ Kennedy and JE Bowers. Heterogeneous integration of a III-V quantum dot laser on high thermal conductivity silicon carbide. Optics Letters 2023; 48(10), 2539-2542.

[19] D Liang and JE Bowers. Recent progress in heterogeneous III-V-on-silicon photonic integration. Light: Advanced Manufacturing 2021; 2(1), 59-83.

[20] N Babazadeh, A Ershad-Langroudi, SM Mousaei and F Alizadegan. Role of nano-dimensions and thin film structure. CRC Press, Boca Raton, Florica, 2024, p. 109-121.

[21] CB Lakshmi, SA Venus, S Velanganni, A Muthukrishnaraj, M Ayyar and M Henini. Structural, optical and photovoltaic properties of V₂O₅/ZnO and reduced graphene oxide (rGO)-V₂O₅/ZnO nanocomposite photoanodes for dye-sensitized solar cells. Carbon Letters 2024; 34, 13-24.

[22] V Simeyon, A Dinesh, D Deivatamil, R Thiruneelakandan, BC Meena, M Mathavi, G Padmapriya, M Durka, M Ayyar, AZ Ansarie, M Hashem and H Fouad. Bi₂O₃/ZnO heterostructured semiconductor nanocomposites: Synthesis, characterization and its visible light-induced degradation of methylene blue dye. Zeitschrift für Physikalische Chemie 2024; 238(3), 421-435.

[23] S Manjula, G Sivakumar, P Dhamodharan, A Dinesh, SK Jaganathan and M Ayyar. Hydrothermal synthesis of Cu₂CoSnS₄ nanoparticles: Characterization and their applications of electrochemical, antibacterial and photocatalytic performances. Zeitschrift für Physikalische Chemie 2024; 238(3), 437-457.

[24] M Anandan, S Dinesh, B Christopher, N Krishnakumar, B Krishnamurthy and M Ayyar. Multifaceted investigations of co-precipitated Ni-doped ZnO nanoparticles: Systematic study on structural integrity, optical interplay and photocatalytic performances. Physica B: Condensed Matter 2024; 674, 415597.

[25] A Roy, O Bulut, S Some, AK Mandal and MD Yilmaz. Green synthesis of silver nanoparticles: Biomolecule-nanoparticle organizations targeting antimicrobial activity. RSC Advances 2019; 9, 2673-2702.

[26] MY Al-darwesh, SS Ibrahim and MA Mohammed. A review on plant extract mediated green synthesis of zinc oxide nanoparticles and their biomedical applications. Results in Chemistry 2024; 7, 101368.

[27] AW Alshameri and M Owais. Antibacterial and cytotoxic potency of the plant-mediated synthesis of metallic nanoparticles Ag NPs and ZnO NPs: A review. Open Nano 2022; 8, 100077.

[28] GA Naikoo, M Mustaqeem, IU Hassan, T Awan, F Arshad, H Salim and A Qurashi. Bioinspired and green synthesis of nanoparticles from plant extracts with antiviral and antimicrobial properties: A critical review. Journal of Saudi Chemical Society 2021; 25(9), 101304.

[29] J Cai, S Chen, M Ji, J Hu, Y Ma and L Qi. Organic additive-free synthesis of mesocrystalline hematite nanoplates via two-dimensional oriented attachment. CrystEngComm 2014; 16(8), 1553-1559.

[30] ND Cuong, DQ Khieu, TT Hoa, DT Quang, PH Viet, TD Lam, ND Hoa and NV Hieu. Facile synthesis of α-Fe2O3 nanoparticles for high-performance CO gas sensor. Materials Research Bulletin 2015; 68, 302-307.

[31] G Chinnadurai, R Subramanian and P Selvi. Fish mucus stabilized iron oxide nanoparticles: Fabrication, DNA damage and bactericidal activity. Inorganic and Nano-Metal Chemistry 2021; 51(4), 550-559.

[32] C Wu, Q Zhuang, L Tian, Y Cui and X Zhang. Facile synthesis of Fe@Fe₂O₃ core-shell nanoparticles attached to carbon nanotubes and their application as high performance anode in lithium-ion batteries. Materials Letters 2013; 107, 27-30.

[33] C Gai, F Zhang, Q Lang, T Liu, N Peng and Z Liu. Facile one-pot synthesis of iron nanoparticles immobilized into the porous hydrochar for catalytic decomposition of phenol. Applied Catalysis B: Environmental 2017; 204, 566-576.

[34] PN Kirdat, PB Dandge, RM Hagwane, AS Nikam, SP Mahadik and ST Jirange. Synthesis and characterization of ginger (Z. officinale) extract mediated iron oxide nanoparticles and its antibacterial activity. Materials Today: Proceedings 2021; 43(4), 2826-2831.

[35] KR Reddy, W Park, BC Sin, J Noh and Y Lee. Synthesis of electrically conductive and superparamagnetic monodispersed iron oxide-conjugated polymer composite nanoparticles by in situ chemical oxidative polymerization. Journal of Colloid and Interface Science 2009; 335(1), 34-39.

[36] KR Reddy, KP Lee, JY Kim and Y Lee. Self-assembly and graft polymerization route to monodispersed Fe3O4@ SiO2 - Polyaniline core-shell composite nanoparticles: Physical properties. Journal of Nanoscience and Nanotechnology 2008; 8(11), 5632-5639.

[37] VT Trang, LT Tam, NV Quy, TQ Huy, NT Thuy, DQ Tri, ND Cuong, PA Tuan, HV Tuan, AT Le and VN Phan. Functional iron oxide-silver hetero-nanocomposites: Controlled synthesis and antibacterial activity. Journal of Electronic Materials 2017; 46, 3381-3389.

[38] R Prucek, J Tuček, M Kilianová, A Panáček, L Kvítek, J Filip, M Kolář, K Tománková and R Zbořil. The targeted antibacterial and antifungal properties of magnetic nanocomposite of iron oxide and silver nanoparticles. Biomaterials 2011; 32(21), 4704-4713.

[39] HS Devi, MA Boda, MA Shah, S Parveen and AH Wani. Green synthesis of iron oxide nanoparticles using Platanus orientalis leaf extract for antifungal activity. Green Processing and Synthesis 2019; 8(1), 38-45.

[40] W Ahmad, KK Jaiswal and S Soni. Green synthesis of titanium dioxide (TiO₂) nanoparticles by using Mentha arvensis leaves extract and its antimicrobial properties. Inorganic and Nano-Metal Chemistry 2020; 50(10), 1032-1038.

[41] R Shanmuganathan, S Sathiyavimal, QH Le, MM Al-Ansari, LA Al-Humaid, GK Jhanani, J Lee and S Barathi. Green synthesized cobalt oxide nanoparticles using Curcuma longa for anti-oxidant, antimicrobial, dye degradation and anti-cancer property. Environmental Research 2023; 236, 116747.

[42] M Kumar. Synthesis and characterization of Pleurotus citrinopileatus extract-mediated iron oxide (FeO) nanoparticles and its antibacterial and anticancer activity. Biomass Conversion and Biorefinery 2023; 14, 1-10.

[43] M Yusefi, K Shameli, RR Ali, SW Pang and SY Teow. Evaluating anticancer activity of plant-mediated synthesized iron oxide nanoparticles using Punica granatum fruit peel extract. Journal of Molecular Structure 2020; 1204, 127539.

[44] M Sriramulu, Balaji and S Sumathi. Photo catalytic, antimicrobial and antifungal activity of biogenic iron oxide nanoparticles synthesised using Aegle marmelos extracts. Journal of Inorganic and Organometallic Polymers and Materials 2021; 31, 1738-1744.

[45] R Govindasamy, V Raja, S Singh, M Govindarasu, S Sabura, K Rekha, VD Rajeswari, SS Alharthi, M Vaiyapuri, R Sudarmani, S Jesurani, B Venkidasamy and M Thiruvengadam. Green synthesis and characterization of cobalt oxide nanoparticles using Psidium guajava leaves extracts and their photocatalytic and biological activities. Molecules 2022; 27, 5646.

[46] K Singh, DS Chopra, D Singh and N Singh. Optimization and ecofriendly synthesis of iron oxide nanoparticles as potential antioxidant. Arabian Journal of Chemistry 2020; 13(12), 9034-9046.

[47] R Thakur, N Kaur, M Kaur, PK Bhowmik, H Han, K Singh, FM Husain and HS Sohal. Green synthesis of magnetic Fe₂O₃ nanoparticle with Chenopodium glaucum L. as recyclable heterogeneous catalyst for one-pot reactions and heavy metal adsorption. Molecules 2024; 29(19), 4583.

[48] G Tombuloglu, A Aldahnem, H Tombuloglu, Y Slimani, S Akhtar, KR Hakeem, MA Almessiere, A Baykal, I Ercan and A Manikandan. Uptake and bioaccumulation of iron oxide nanoparticles (Fe₃O₄) in barley (Hordeum vulgare L.): Effect of particle-size. Environmental Science and Pollution Research International 2024; 31(14), 22171-22186.

[49] VN Kalpana and VD Rajeswari. A review on green synthesis, biomedical applications, and toxicity studies of ZnO NPs. Bioinorganic Chemistry and Applications 2018; 2018, 3569758.

[50] JV Meshram, VB Koli, SG Kumbhar, LC Borde, MR Phadatare and SH Pawar. Structural, spectroscopic and anti-microbial inspection of PEG capped ZnO nanoparticles for biomedical applications. Materials Research Express 2018; 5(4), 45016.

[51] I Khan, K Saeed and I Khan. Nanoparticles: Properties, applications and toxicities. Arabian Journal of Chemistry 2019; 12(7), 908-931.

[52] A Ali, M Pan, TB Tilly, M Zia and CY Wu. Performance of silver, zinc, and iron nanoparticles-doped cotton filters against airborne E. coli to minimize bioaerosol exposure. Air Quality, Atmosphere, and Health 2018; 11(10), 1233-1242.

[53] A Sharma, SV Madhunapantula and GP Robertson. Toxicological considerations when creating nanoparticle-based drugs and drug delivery systems. Expert Opinion on Drug Metabolism and Toxicology 2012; 8(1), 47-69.

[54] J Jeevanandam, A Barhoum, YS Chan, A Dufresne and MK Danquah. Review on nanoparticles and nanostructured materials: History, sources, toxicity and regulations. Beilstein Journal of Nanotechnology 2018; 9, 1050-1074.

[55] S Iravani, H Korbekandi, SV Mirmohammadi and B Zolfaghari. Synthesis of silver nanoparticles: Chemical, physical and biological methods. Research in Pharmaceutical Sciences 2014; 9(6), 385-406.

[56] RJ Varghese, N Zikalala, EHM Sakho and OS Oluwafemi. Green synthesis protocol on metal oxide nanoparticles using plant extracts. Elsevier, Amsterdam, Netherlands, 2019, p. 67-82.

[57] G Sangeetha, S Rajeshwari and R Venckatesh. Green synthesis of zinc oxide nanoparticles by aloe barbadensis miller leaf extract: Structure and optical properties. Materials Research Bulletin 2011; 46(12), 2560-2566.

[58] SL Chia and DT Leong. Reducing ZnO nanoparticles toxicity through silica coating. Heliyon 2016; 2(10), e00177.

[59] P Jamdagni, P Khatri and JS Rana. Green synthesis of zinc oxide nanoparticles using flower extract of Nyctanthes arbor-tristis and their antifungal activity. Journal of King Saud University - Science 2018; 30, 168-175.

[60] CA Sergeant, D Africander, P Swart and AC Swart. Sutherlandia frutescens modulates adrenal hormone biosynthesis, acts as a selective glucocorticoid receptor agonist (SEGRA) and displays anti-mineralocorticoid properties. Journal of Ethnopharmacology 2017; 202, 290-301.

[61] D Krishnaiah, T Devi, A Bono and R Sarbatly. Studies on phytochemical constituents of six Malaysian medicinal plants. Journal of Medicinal Plants Research 2009; 3(2), 67-72.

[62] CO Alebiosu and AJ Yusuf. Phytochemical screening, thin-layer chromatographic studies and UV analysis of extracts of Citrullus lanatus. Journal of Pharmaceutical, Chemical and Biological Sciences 2015; 3, 214-220.

[63] NH Kumar, JD Andia, S Manjunatha, M Murali, KN Amruthesh and S Jagannath. Antimitotic and DNA-binding potential of biosynthesized ZnO-NPs from leaf extract of Justicia wynaadensis (Nees) Heyne - A medicinal herb. Biocatalysis and Agricultural Biotechnology 2019; 18, 101024.

[64] G Fais, A Sidorowicz, G Perra, D Dessì, F Loy, N Lai, P Follesa, R Orrù, G Cao and A Concas. Cytotoxic effects of ZnO and Ag nanoparticles synthesized in microalgae extracts on PC12 cells. Marine Drugs 2024; 22(12), 549.

[65] R Dobrucka and J Długaszewska. Biosynthesis and antibacterial activity of ZnO nanoparticles using Trifolium pratense flower extract. Saudi Journal of Biological Sciences 2016; 23(4), 517-523.

[66] J Fowsiya, G Madhumitha, NA Al-Dhabi and MV Arasu. Photocatalytic degradation of Congo red using Carissa edulis extract capped zinc oxide nanoparticles. Journal of Photochemistry and Photobiology B: Biology 2016; 162, 395-401.

[67] CA Soto-Robles, O Nava, L Cornejo, E Lugo-Medina, AR Vilchis-Nestor, A Castro-Beltrán and PA Luque. Biosynthesis, characterization and photocatalytic activity of ZnO nanoparticles using extracts of Justicia spicigera for the degradation of methylene blue. Journal of Molecular Structure 2021; 1225, 129101.

[68] S Ambika and M Sundrarajan. Antibacterial behaviour of Vitex negundo extract assisted ZnO nanoparticles against pathogenic bacteria. Journal of Photochemistry and Photobiology B: Biology 2015; 146, 52-57.

[69] D Suresh, RM Shobharani, PC Nethravathi, MP Kumar, H Nagabhushana and SC Sharma. Artocarpus gomezianus aided green synthesis of ZnO nanoparticles: Luminescence, photocatalytic and antioxidant properties. Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 2015; 141, 128-134.

[70] T Safawo, BV Sandeep, S Pola and A Tadesse. Synthesis and characterization of zinc oxide nanoparticles using tuber extract of anchote (Coccinia abyssinica (Lam.) Cong.) for antimicrobial and antioxidant activity assessment. OpenNano 2018; 3, 56-63.

[71] PC Nagajyothi, SJ Cha, IJ Yang, TVM Sreekanth, KJ Kim and HM Shin. Antioxidant and anti-inflammatory activities of zinc oxide nanoparticles synthesized using Polygala tenuifolia root extract. Journal of Photochemistry and Photobiology B: Biology 2015; 146, 10-17.

[72] D Suresh, PC Nethravathi, Udayabhanu, H Rajanaika, H Nagabhushana and SC Sharma. Green synthesis of multifunctional zinc oxide (ZnO) nanoparticles using Cassia fistula plant extract and their photodegradative, antioxidant and antibacterial activities. Materials Science in Semiconductor Processing 2015; 31, 446-454.

[73] AM Al-Mohaimeed, WA Al-Onazi and MF El-Tohamy. Multifunctional eco-friendly synthesis of ZnO nanoparticles in biomedical applications. Molecules 2022; 27, 579.

[74] S Faisal, H Jan, SA Shah, S Shah, A Khan, MT Akbar, M Rizwan, F Jan, Wajidullah, N Akhtar, A Khattak and S Syed. Green synthesis of zinc oxide (ZnO) nanoparticles using aqueous fruit extracts of Myristica fragrans: Their characterizations and biological and environmental applications. ACS Omega 2021; 6, 9709-9722.

[75] C Mallikarjunaswamy, VL Ranganatha, R Ramu, Udayabhanu and G Nagaraju. Facile microwave-assisted green synthesis of ZnO nanoparticles: Application to photodegradation, antibacterial and antioxidant. Journal of Materials Science: Materials in Electronics 2020; 31, 1004-1021.

[76] CO Tettey and HM Shin. Evaluation of the antioxidant and cytotoxic activities of zinc oxide nanoparticles synthesized using Scutellaria baicalensis root. Scientific African 2019; 6, e00157.

[77] G Sharmila, M Thirumarimurugan and C Muthukumaran. Green synthesis of ZnO nanoparticles using Tecoma castanifolia leaf extract: Characterization and evaluation of its antioxidant, bactericidal and anticancer activities. Microchemical Journal 2019; 145, 578-587.

[78] ZUH Khan, HM Sadiq, NS Shah, AU Khan, N Muhammad, SU Hassan, K Tahir, SZ Safi, FU Khan, M Imran, N Ahmad, F Ullah, A Ahmad, M Sayed, MS Khalid, SA Qaisrani, M Ali and A Zakir. Greener synthesis of zinc oxide nanoparticles using Trianthema portulacastrum extract and evaluation of its photocatalytic and biological applications. Journal of Photochemistry and Photobiology B: Biology 2019; 192, 147-157.

[79] J Iqbal, BA Abbasi, T Yaseen, SA Zahra, A Shahbaz, SA Shah, S Uddin, X Ma, B Raouf, S Kanwal, W Amin, T Mahmood, HA El-Serehy and P Ahmad. Green synthesis of zinc oxide nanoparticles using Elaeagnus angustifolia L. leaf extracts and their multiple in vitro biological applications. Scientific Reports 2021; 11, 20988.

[80] S Azizi, R Mohamad, A Bahadoran, S Bayat, RA Rahim, A Ariff and WZ Saad. Effect of annealing temperature on antimicrobial and structural properties of bio-synthesized zinc oxide nanoparticles using flower extract of Anchusa italica. Journal of Photochemistry and Photobiology B: Biology 2016; 161, 441-449.

[81] S Jafarirad, M Mehrabi, B Divband and M Kosari-Nasab. Biofabrication of zinc oxide nanoparticles using fruit extract of Rosa canina and their toxic potential against bacteria: A mechanistic approach. Materials Science and Engineering: C 2016; 59, 296-302.

[82] S Azizi, R Mohamad and MM Shahri. Green microwave-assisted combustion synthesis of zinc oxide nanoparticles with Citrullus colocynthis (L.) Schrad: Characterization and biomedical applications. Molecules 2017; 22(2), 301.

[83] B Malaikozhundan, B Vaseeharan, S Vijayakumar, K Pandiselvi, MAR Kalanjiam, K Murugan and G Benelli. Biological therapeutics of Pongamia pinnata coated zinc oxide nanoparticles against clinically important pathogenic bacteria, fungi and MCF-7 breast cancer cells. Microbial Pathogenesis 2017; 104, 268-277.

[84] H Padalia and S Chanda. Characterization, antifungal and cytotoxic evaluation of green synthesized zinc oxide nanoparticles using Ziziphus nummularia leaf extract. Artificial Cells, Nanomedicine, and Biotechnology 2017; 45, 1751-1761.

[85] S Rajeshkumar, SV Kumar, A Ramaiah, H Agarwal, T Lakshmi and SM Roopan. Biosynthesis of zinc oxide nanoparticles using Mangifera indica leaves and evaluation of their antioxidant and cytotoxic properties in lung cancer (A549) cells. Enzyme and Microbial Technology 2018; 117, 91-95.

[86] J Suresh, G Pradheesh, V Alexramani, M Sundrarajan and SI Hong. Green synthesis and characterization of zinc oxide nanoparticle using insulin plant (Costus pictus D. Don) and investigation of its antimicrobial as well as anticancer activities. Advances in Natural Sciences: Nanoscience and Nanotechnology 2018; 9, 15008.

[87] C Zhao, X Zhang and Y Zheng. Biosynthesis of polyphenols functionalized ZnO nanoparticles: Characterization and their effect on human pancreatic cancer cell line. Journal of Photochemistry and Photobiology B: Biology 2018; 183, 142-146.

[88] R Mohamed, B Gowdhami, MSM Jaabir, G Archunan and N Suganthy. Anticancer potential of zinc oxide nanoparticles against cervical carcinoma cells synthesized via biogenic route using aqueous extract of Gracilaria edulis. Materials Science and Engineering: C 2019; 103, 109840.

[89] RS Murugan, PSM Hajasharif, C Manoharan, A Dinesh, S Suthakaran, M Ayyar, M Hashem and H Fouad. Effect of Cu substitution on morphological, optical and electrochemical properties of Co₃O₄ nanoparticles by co-precipitation method. Results in Chemistry 2024; 11, 101830.

[90] K Athira, S Dhanapandian, S Suthakaran, A Dinesh and M Ayyar. Transition metal oxide-based NiO-Co₃O₄ nanocomposite as an electrode material for the high-performance supercapacitor. Journal of Materials Science: Materials in Electronics 2024; 35, 1178.

[91] T Rasheed, F Nabeel, M Bilal and HMN Iqbal. Biogenic synthesis and characterization of cobalt oxide nanoparticles for catalytic reduction of direct yellow-142 and methyl orange dyes. Biocatalysis and Agricultural Biotechnology 2019; 19, 101154.

[92] DC Onwudiwe, MP Ravele and EE Elemike. Eco-friendly synthesis, structural properties and morphology of cobalt hydroxide and cobalt oxide nanoparticles using extract of Litchi chinensis. Nano-Structures and Nano-Objects 2020; 23, 100470.

[93] M Sorbiun, ES Mehr, A Ramazani and AM Malekzadeh. Biosynthesis of metallic nanoparticles using plant extracts and evaluation of their antibacterial properties. Directory of Open Access Journals 2018; 3(1), 1-16.

[94] EG Mornani, P Mosayebian, D Dorranian and K Behzad. Effect of calcination temperature on the size and optical properties of synthesized ZnO nanoparticles. Journal of Ovonic Research 2016; 12(2), 75-80.

[95] N Akhlaghi, G Najafpour-Darzi and H Younesi. Facile and green synthesis of cobalt oxide nanoparticles using ethanolic extract of Trigonella foenumgraceum (Fenugreek) leaves. Advanced Powder Technology 2020; 31(8), 3562-3569.

[96] S Iravani and RS Varma. Sustainable synthesis of cobalt and cobalt oxide nanoparticles and their catalytic and biomedical applications. Green Chemistry 2020; 22(9), 2643-2661.

[97] SK Jesudoss, JJ Vijaya, PI Rajan, K Kaviyarasu, M Sivachidambaram, LJ Kennedy, HA Al-Lohedan, R Jothiramalingam and MA Munusamy. High performance multifunctional green Co₃O₄ spinel nanoparticles: Photodegradation of textile dye effluents, catalytic hydrogenation of nitro-aromatics and antibacterial potential. Photochemical and Photobiological Sciences 2017; 16, 766-778.

[98] W Anupong, R On-Uma, K Jutamas, D Joshi, SH Salmen, TA Alahmadi and GK Jhanani. Cobalt nanoparticles synthesizing potential of orange peel aqueous extract and their antimicrobial and antioxidant activity. Environmental Research 2023; 216, 114594.

[99] S Haq, F Abbasi, MB Ali, A Hedfi, A Mezni, W Rehman, M Waseem, AR Khan and H Shaheen. Green synthesis of cobalt oxide nanoparticles and the effect of annealing temperature on their physiochemical and biological properties. Materials Research Express 2021; 8(7), 75009.

[100] AT Khalil, M Ovais, I Ullah, M Ali, ZK Shinwari and M Maaza. Physical properties, biological applications and biocompatibility studies on biosynthesized single phase cobalt oxide (Co₃O₄) nanoparticles via Sageretia thea (Osbeck). Arabian Journal of Chemistry 2020; 13(1), 606-619.

[101] CT Anuradha and P Raji. Bio-inspired Senna auriculata flower extract assisted biogenic synthesis, characterization of cobalt oxide nanoparticles and their antibacterial and antifungal efficacy. Ceramics International 2022; 49, 11689-11695.

[102] S Kavica, P Rajesh, V Velmani and GT Parethe. Biological synthesis of cobalt oxide nanoparticles using Ziziphus oenopolia leaf extract. Journal of Environmental Nanotechnology 2024; 13, 85-91.

[103] S Uddin, LB Safdar, J Iqbal, T Yaseen, S Laila, S Anwar, BA Abbasi, MS Saif and UM Quraishi. Green synthesis of nickel oxide nanoparticles using leaf extract of Berberis balochistanica: Characterization, and diverse biological applications. Microscopy Research and Technique 2021; 84, 2004-2016.

[104] J Iqbal, BA Abbasi, R Ahmad, M Mahmoodi, A Munir, SA Zahra, A Shahbaz, M Shaukat, S Kanwal, S Uddin, T Mahmood and R Capasso. Phytogenic synthesis of nickel oxide nanoparticles (NiO) using fresh leaves extract of Rhamnus triquetra (Wall.) and investigation of its multiple in vitro biological potentials. Biomedicines 2020; 8(5), 117.

[105] RA Raj, MS AlSalhi and S Devanesan. Microwave-assisted synthesis of nickel oxide nanoparticles using Coriandrum sativum leaf extract and their structural-magnetic catalytic properties. Materials 2017; 10(5), 460.

[106] DH Prasad, HR Kim, JS Park, JW Son, BK Kim, HW Lee and JH Lee. Superior sinterability of nano-crystalline gadolinium doped ceria powders synthesized by co-precipitation method. Journal of Alloys and Compounds 2010; 495(1), 238-241.

[107] Y Wang, YF Zhang, HR Liu, SJ Yu and QZ Qin. Nanocrystalline NiO thin film anode with MgO coating for Li-ion batteries. Electrochimica Acta 2003; 48(28), 4253-4259.

[108] JW Lang, LB Kong, WJ Wu, YC Luo and L Kang. Facile approach to prepare loose-packed NiO nano-flakes materials for supercapacitors. Chemical Communications 2008; (35), 4213-4215.

[109] M Ghosh, K Biswas, A Sundaresan and CNR Rao. MnO and NiO nanoparticles: Synthesis and magnetic properties. Journal of Materials Chemistry 2006; 16(1), 106-111.

[110] X Zhang, W Shi, J Zhu, W Zhao, J Ma, S Mhaisalkar, TL Maria, Y Yang, H Zhang, HH Hngand and Q Yan. Synthesis of porous NiO nanocrystals with controllable surface area and their application as supercapacitor electrodes. Nano Research 2010; 3(9), 643-652.

[111] JF Li, B Xiao, LJ Du, R Yan and TD Liang. Preparation of nano-NiO particles and evaluation of their catalytic activity in pyrolyzing cellulose. Journal of Fuel Chemistry and Technology 2008; 36, 42-47.

[112] YW Baek and YJ An. Microbial toxicity of metal oxide nanoparticles (CuO, NiO, ZnO, and Sb₂O₃) to Escherichia coli, Bacillus subtilis, and Streptococcus aureus. Science of the Total Environment 2011; 409(8), 1603-1608.

[113] K Lingaraju, HR Naika, H Nagabhushana, K Jayanna, S Devaraja and G Nagaraju. Biosynthesis of nickel oxide nanoparticles from Euphorbia heterophylla (L.) and their biological application. Arabian Journal of Chemistry 2020; 13, 4712-4719.

[114] A Manikandan, M Durka and SA Antony. One-pot flash combustion synthesis, structural, morphological, and opto-magnetic properties of spinel MnₓCo₁₋ₓAl₂O₄ (x = 0, 0.3, and 0.5) nanocatalysts. Journal of Superconductivity and Novel Magnetism 2015; 28, 209-218.

[115] Z Suo, X Dong and H Liu. Single-crystal-like NiO colloidal nanocrystal-aggregated microspheres with mesoporous structure: Synthesis and enhanced electrochemistry, photocatalysis, and water treatment properties. Journal of Solid State Chemistry 2013; 206, 1-8.

[116] S Saif, A Tahir, T Asim and Y Chen. Plant mediated green synthesis of CuO nanoparticles: Comparison of toxicity of engineered and plant mediated CuO nanoparticles towards Daphnia magna. Nanomaterials 2016; 6(11), 205.

[117] X Dong, W Ding, X Zhang and X Liang. Mechanism and kinetics model of degradation of synthetic dyes by UV-vis/H₂O₂/ferrioxalate complexes. Dyes and Pigments 2007; 74(2), 470-476.

[118] AA Ezhilarasi, JJ Vijaya, K Kaviyarasu, LJ Kennedy, RJ Ramalingam and HA Al-Lohedan. Green synthesis of NiO nanoparticles using Aegle marmelos leaf extract for the evaluation of in-vitro cytotoxicity, antibacterial and photocatalytic properties. Journal of Photochemistry and Photobiology B: Biology 2018; 180, 39-50.

[119] S Ghazal, N Khandannasab, HA Hosseini, Z Sabouri, A Rangrazi and M Darroudi. Green synthesis of copper-doped nickel oxide nanoparticles using okra plant extract for the evaluation of their cytotoxicity and photocatalytic properties. Ceramics International 2021; 47(19), 27165-27176.

[120] SA Kumar, SSR Inbanathan, A Manikandan, NS Topare, S Srinivasan, MA Kumar, MH Mahmoud, H Fouad, A Ansari and LS Priya. Green synthesis, structural, morphological and sonocatalytic properties of CuO nanoparticles assisted by Camellia sinensis (Tea) extract. Industrial Crops and Products 2024; 219, 118915.

[121] M Sahooli, S Sabbaghi and R Saboori. Synthesis and characterization of mono sized CuO nanoparticles. Materials Letters 2012; 81, 169-172.

[122] MJ Soltanianfard and A Firoozadeh. Synthesis and characterization of copper (II)-oxide nanoparticles from two Cu(II) coordination polymers. Journal of Sciences, Islamic Republic of Iran 2016; 27, 113-117.

[123] AA Radhakrishnan and BB Beena. Structural and optical absorption analysis of CuO nanoparticles. Indian Journal of Advances in Chemical Science 2014; 2, 158-161.

[124] MA Dar, YS Kim, WB Kim, JM Sohn and HS Shin. Structural and magnetic properties of CuO nanoneedles synthesized by hydrothermal method. Applied Surface Science 2008; 254(22), 7477-7481.

[125] TMD Dang, TTT Le, E Fribourg-Blanc and MC Dang. Synthesis and optical properties of copper nanoparticles prepared by a chemical reduction method. Advances in Natural Sciences: Nanoscience and Nanotechnology 2011; 2, 15009.

[126] N Sundaramurthy and C Parthiban. Biosynthesis of copper oxide nanoparticles using Pyrus Pyrifolia leaf extract and evolve the catalytic activity. International Research Journal of Engineering and Technology 2015; 2(6), 332-338.

[127] R Dastjerdi and M Montazer. A review on the application of inorganic nano-structured materials in the modification of textiles: Focus on anti-microbial properties. Colloids and Surfaces B: Biointerfaces 2010; 79(1), 5-18.

[128] Udayabhanu, PC Nethravathi, MAP Kumar, D Suresh, K Lingaraju, H Rajanaika, H Nagabhushana and SC Sharma. Tinospora cordifolia mediated facile green synthesis of cupric oxide nanoparticles and their photocatalytic, antioxidant and antibacterial properties. Materials Science in Semiconductor Processing 2015; 33, 81-88.

[129] YT Prabhu, KV Rao, VS Sai and T Pavani. A facile biosynthesis of copper nanoparticles: A micro-structural and antibacterial activity investigation. Journal of Saudi Chemical Society 2017; 21(2), 180-185.

[130] HR Naika, K Lingaraju, K Manjunath, D Kumar, G Nagaraju, D Suresh and H Nagabhushana. Green synthesis of CuO nanoparticles using Gloriosa superba L. extract and their antibacterial activity. Journal of Taibah University for Science 2015; 9(1), 7-12.

[131] IM Jhung, AA Rahuman, S Marimuthu, AV Kirthi, K Anbarasan, P Padmini and G Rajakumar. Green synthesis of copper nanoparticles using Eclipta prostrata leaves extract and their antioxidant and cytotoxic activities. Experimental and Therapeutic Medicine 2017; 14(1), 18-24.

[132] G Jayakumarai, C Gokulpriya, R Sudhapriya, G Sharmila and C Muthukumaran. Phytofabrication and characterization of monodisperse copper oxide nanoparticles using Albizia lebbeck leaf extract. Applied Nanoscience 2015; 5, 1017-1021.

[133] JK Sharma, MS Akhtar, S Ameen, P Srivastava and G Singh. Green synthesis of CuO nanoparticles with leaf extract of Calotropis gigantea and its dye-sensitized solar cells applications. Journal of Alloys and Compounds 2015; 632, 321-325.

[134] BK Sharma, DV Shah and DR Roy. Green synthesis of CuO nanoparticles using Azadirachta indica and its antibacterial activity for medicinal applications. Materials Research Express 2018; 5(9), 95033.

[135] M Gowri, N Latha and M Rajan. Copper oxide nanoparticles synthesized using Eupatorium odoratum, Acanthospermum hispidum leaf extracts, and its antibacterial effects against pathogens: A comparative study. BioNanoScience 2019; 9, 545-552.

[136] A Azam, AS Ahmed, M Oves, MS Khan and A Memic. Size-dependent antimicrobial properties of CuO nanoparticles against Gram-positive and Gram-negative bacterial strains. International Journal of Nanomedicine 2012; 7, 3527-3535.

[137] G Sharmila, M Thirumarimurugan and VM Sivakumar. Optical, catalytic and antibacterial properties of phytofabricated CuO nanoparticles using Tecoma castanifolia leaf extract. Optik 2016; 127(19), 7822-7828.

[138] M Dolati, F Tafvizi, M Salehipour, TK Movahed and P Jafari. Biogenic copper oxide nanoparticles from Bacillus coagulans induced reactive oxygen species generation and apoptotic and anti-metastatic activities in breast cancer cells. Scientific Reports 2023; 13(1), 3256.

[139] B Murugan, MZ Rahman, I Fatimah, JA Lett, J Annaraj, NHM Kaus, MA Al-Anber and S Sagadevan. Green synthesis of CuO nanoparticles for biological applications. Inorganic Chemistry Communications 2023; 155, 111088.

[140] A Al-Yunus, W Al-Arjan, H Traboulsi, R Schuarca, P Chando, ID Hosein and M Hessien. Effect of synthesis conditions on CuO-NiO nanocomposites synthesized via saponin-green/microwave assisted-hydrothermal method. Nanomaterials 2024; 14(3), 308.

[141] E Hannachi, Y Slimani, A Ekicibil, A Manikandan and FB Azzouz. Excess conductivity and AC susceptibility studies of Y-123 superconductor added with TiO₂ nano-wires. Materials Chemistry and Physics 2019; 235, 121721.

[142] E Priyadharshini, S Suresh, S Srinivasa and A Manikandan. Electrochemical performance of TiO₂-C nanocomposite as an anode material for lithium-ion battery. Journal of Materials Science: Materials in Electronics 2020; 31, 6199-6206.

[143] BA Kumar, V Vetrivelan, G Ramalingam, A Manikandan, S Viswanathan, P Boomi and G Ravi. Computational studies and experimental fabrication of DSSC device assembly on 2D-layered TiO₂ and MoS₂@ TiO₂ nanomaterials. Physica B: Condensed Matter 2022; 633, 413770.

[144] B Trouiller, R Reliene, A Westbrook, P Solaimani and RH Schiestl. Titanium dioxide nanoparticles induce DNA damage and genetic instability in vivo in mice. Cancer Research 2009; 69(22), 8784-8789.

[145] X Chai, H Zhang and C Cheng. 3D FTO inverse opals@ hematite@ TiO₂ hierarchically structured photoanode for photoelectrochemical water splitting. Semiconductor Science and Technology 2017; 32(11), 114003.

[146] O Monfort, D Raptis, L Satrapinskyy, T Roch, G Plesch and P Lianos. Production of hydrogen by water splitting in a photoelectrochemical cell using a BiVO₄/TiO₂ layered photoanode. Electrochimica Acta 2017; 251, 244-249.

[147] A Fujishima, TN Rao and DA Tryk. Titanium dioxide photocatalysis. Journal of Photochemistry and Photobiology C: Photochemistry Reviews 2000; 1(1), 1-21.

[148] SP Goutam, G Saxena, V Singh, AK Yadav, RN Bharagava and KB Thapa. Green synthesis of TiO₂ nanoparticles using leaf extract of Jatropha curcas L. for photocatalytic degradation of tannery wastewater. Chemical Engineering Journal 2018; 336, 386-396.

[149] T Pushpamalini, M Keerthana, R Sangavi, A Nagaraj and P Kamaraj. Comparative analysis of green synthesis of TiO₂ nanoparticles using four different leaf extract. Materials Today Proceedings 2020; 40(S1), S180-S184.

[150] RA Rodríguez-Jiménez, Y Panecatl-Bernal, J Carrillo-López, MÁ Méndez-Rojas, A Romero-López, M Pacio-Castillo, I Vivaldo, A Morales-Sánchez, RD Arce, J Caram, J Villanueva-Cab and J Alvarado. Influence of ethanolic plant extracts on morphology and size distribution of sol‐gel prepared TiO₂ nanoparticles. ChemistrySelect 2021; 6(16), 3958-3968.

[151] A Ansari, VU Siddiqui, WU Rehman, MK Akram, WA Siddiqi, AM Alosaimi, MA Hussein and M Rafatullah. Green synthesis of TiO₂ nanoparticles using Acorus calamus leaf extract and evaluating its photocatalytic and in vitro antimicrobial activity. Catalysts 2022; 12(2), 181.

[152] BP Narasaiah, P Banoth, AGB Dominguez, BK Mandal, CK Kumar, CHW Barnes, LDLS Valladares and P Kollu. Biogenic photo-catalyst TiO2 nanoparticles for remediation of environment pollutants. ACS Omega 2022; 7 (30), 26174-26189.

[153] S Subhapriya and P Gomathipriya. Green synthesis of titanium dioxide (TiO₂) nanoparticles by Trigonella foenum-graecum extract and its antimicrobial properties. Microbial Pathogenesis 2018; 116, 215-220.

[154] D Anbumani, KV Dhandapani, J Manoharan, R Babujanarthanam, AKH Bashir, K Muthusamy, A Alfarhan and K Kanimozhi. Green synthesis and antimicrobial efficacy of titanium dioxide nanoparticles using Luffa acutangula leaf extract. Journal of King Saud University - Science 2022; 34(3), 101896.

[155] D Hariharan, K Srinivasan and LC Nehru. Synthesis and characterization of TiO₂ nanoparticles using Cynodon dactylon leaf extract for antibacterial and anticancer (A549 cell lines) activity. Journal of Nanomedicine Research 2017; 5(6), 138-142.

[156] M Narayanan, P Vigneshwari, D Natarajan, S Kandasamy, M Alsehli, A Elfasakhany and A Pugazhendhi. Synthesis and characterization of TiO₂ NPs by aqueous leaf extract of Coleus aromaticus and assess their antibacterial, larvicidal, and anticancer potential. Environmental Research 2021; 200, 111335.

[157] GK Naik, PM Mishra and K Parida. Green synthesis of Au/TiO₂ for effective dye degradation in aqueous system. Chemical Engineering Journal 2013; 229, 492-497.

[158] AA Kashale, KP Gattu, K Ghule, VH Ingole, S Dhanayat, R Sharma, JY Chang and AV Ghule. Biomediated green synthesis of TiO₂ nanoparticles for lithium ion battery application. Composites Part B: Engineering 2016; 99, 297-304.

[159] A Rostami-Vartooni, M Nasrollahzadeh, M Salavati-Niasari and M Atarod. Photocatalytic degradation of azo dyes by titanium dioxide supported silver nanoparticles prepared by a green method using Carpobrotus acinaciformis extract. Journal of Alloys and Compounds 2016; 689, 15-20.

[160] KA Kumar, SK Gousia, M Anupama and JNL Latha. A review on phytochemical constituents and biological assays of Averrhoa bilimbi. International Journal of Pharmacy and Pharmaceutical Science Research 2013; 3(4), 136-139.

[161] R Aswini, S Murugesan and K Kannan. Bio-engineered TiO₂ nanoparticles using Ledebouria revoluta extract: Larvicidal, histopathological, antibacterial and anticancer activity. International Journal of Environmental Analytical Chemistry 2021; 101(15), 2926-2936.

[162] N Thakur, J Ghosh, SK Pandey, A Pabbathi and J Das. A comprehensive review on biosynthesis of magnesium oxide nanoparticles, and their antimicrobial, anticancer, antioxidant activities as well as toxicity study. Inorganic Chemistry Communications 2022; 146, 110156.

[163] MR Farani, M Farsadrooh, I Zare, A Gholami and O Akhavan. Green synthesis of magnesium oxide nanoparticles and nanocomposites for photocatalytic antimicrobial, antibiofilm and antifungal applications. Catalysts 2023; 13(4), 642.

[164] I Balderas-León, JM Silva-Jara, MÁ López-Álvarez, P Ortega-Gudiño, A Barrera-Rodríguez and C Neri-Cortés. Degradation of malachite green dye by solar irradiation assisted by TiO₂ biogenic nanoparticles using Vaccinium corymbosum extract. Sustainability 2024; 16(17), 7638.

[165] ET Helmy, EM Abouellef, UA Soliman and JH Pan. Novel green synthesis of S-doped TiO₂ nanoparticles using Malva parviflora plant extract and their photocatalytic, antimicrobial and antioxidant activities under sunlight illumination. Chemosphere 2021; 271, 129524.

[166] A Muthuvel, NM Said, M Jothibas, K Gurushankar and V Mohana. Microwave-assisted green synthesis of nanoscaled titanium oxide: Photocatalyst, antibacterial and antioxidant properties. Journal of Materials Science: Materials in Electronics 2021; 32, 23522-23539.

[167] BK Thakur, A Kumar and D Kumar. Green synthesis of titanium dioxide nanoparticles using Azadirachta indica leaf extract and evaluation of their antibacterial activity. South African Journal of Botany 2019; 124, 223-227.

[168] L Gudata, A Saka, JL Tesfaye, R Shanmugam, LP Dwarampudi, N Nagaprasad, B Stalin and R Krishnaraj. Investigation of TiO₂ nanoparticles using leaf extracts of Lippia adoensis (Kusaayee) for antibacterial activity. Journal of Nanomaterials 2022; 2022, 3881763.

[169] R Saini and P Kumar. Green synthesis of TiO₂ nanoparticles using Tinospora cordifolia plant extract and its potential application for photocatalysis and antibacterial activity. Inorganic Chemistry Communications 2023; 156, 111221.

[170] AK Shimi, HM Ahmed, M Wahab, S Katheria, SM Wabaidur, GE Eldesoky, MA Islam and KP Rane. Synthesis and applications of green synthesized TiO₂ nanoparticles for photocatalytic dye degradation and antibacterial activity. Journal of Nanomaterials 2022; 2022, 7060388.

[171] A Saka, Y Shifera, LT Jule, B Badassa, N Nagaprasad, R Shanmugam, LP Dwarampudi, V Seenivasan and K Ramaswamy. Biosynthesis of TiO₂ nanoparticles by Caricaceae (Papaya) shell extracts for antifungal application. Scientific Reports 2022; 12, 15960.

[172] MA Irshad, R Nawaz, MZ Rehman, M Imran, J Ahmad, S Ahmad, A Inam, A Razzaq, M Rizwan and S Ali. Synthesis and characterization of titanium dioxide nanoparticles by chemical and green methods and their antifungal activities against wheat rust. Chemosphere 2020; 258, 127352.

[173] H Rathi and AR Jeice. Visible light photocatalytic dye degradation, antimicrobial activities of green synthesized Ag/TiO₂ nanoparticles. Chemical Physics Impact 2024; 8, 100537.

[174] LMA Masoudi, AS Alqurashi, AA Zaid and H Hamdi. Characterization and biological studies of synthesized titanium dioxide nanoparticles from leaf extract of Juniperus phoenicea (L.) growing in Taif Region, Saudi Arabia. Processes 2023; 11(1), 272.

[175] E Vidhya, S Vijayakumar, M Nilavukkarasi, VN Punitha, S Snega and PK Praseetha. Green fabricated MgO nanoparticles as antimicrobial agent: Characterization and evaluation. Materials Today Proceedings 2021; 45, 5579-5583.

[176] S Vijayakumar, VN Punitha and N Parameswari. Phytonanosynthesis of MgO nanoparticles: Green synthesis, characterization and antimicrobial evaluation. Arabian Journal for Science and Engineering 2022; 47, 6729-6734.

[177] BK Sharma, BR Mehta, VP Chaudhari, EV Shah, SM Roy and DR Roy. Green synthesis of dense rock MgO nanoparticles using Carica papaya leaf extract and its shape dependent antimicrobial activity: Joint experimental and DFT investigation. Journal of Cluster Science 2021; 33, 1667-1675.

[178] IY Younis, SS El-Hawary, OA Eldahshan, MM Abdel-Aziz and ZY Ali. Green synthesis of magnesium nanoparticles mediated from Rosa floribunda charisma extract and its antioxidant, antiaging and antibiofilm activities. Scientific Reports 2021; 11, 16868.

[179] SN Nandhini, N Sisubalan, A Vijayan, C Karthikeyan, M Gnanaraj, DAM Gideon, T Jebastin, K Varoprasad and R Sadiku. Recent advances in green synthesized nanoparticles for bactericidal and wound healing applications. Heliyon 2023; 9(2), e13128.

[180] T Ahmed, M Noman, N Manzoor, M Shahid, KM Hussaini, M Rizwan, S Ali, A Maqsood and B Li. Green magnesium oxide nanoparticles-based modulation of cellular oxidative repair mechanisms to reduce arsenic uptake and translocation in rice (Oryza sativa L.) plants. Environmental Pollution 2021; 288, 117785.

[181] SA Kumar, M Jarvin, SSR Inbanathan, A Umar, NP Lalla, NY Dzade, H Algadi, QI Rahman and S Baskoutas. Facile green synthesis of magnesium oxide nanoparticles using tea (Camellia sinensis) extract for efficient photocatalytic degradation of methylene blue dye. Environmental Technology and Innovation 2022; 28, 102746.

[182] E Proniewicz, AM Vijayan, O Surma, A Szkudlarek and M Molenda. Plant-assisted green synthesis of MgO nanoparticles as a sustainable material for bone regeneration: Spectroscopic properties. International Journal of Molecular Sciences 2024; 25(8), 4242.

[183] S Joghee, P Ganeshan, A Vincent and SI Hong. Ecofriendly biosynthesis of zinc oxide and magnesium oxide particles from medicinal plant Pisonia grandis R. Br. leaf extract and their antimicrobial activity. BioNanoScience 2019; 9, 141-154.

[184] J Suresh, G Pradheesh, V Alexramani, M Sundrarajan and SI Hong. Green synthesis and characterization of hexagonal shaped MgO nanoparticles using insulin plant (Costus pictus D. Don) leave extract and its antimicrobial as well as anticancer activity. Advanced Powder Technology 2018; 29, 1685-1694.

[185] M Barzegar, D Ahmadvand, Z Sabouri and M Darroudi. Phytoextract-mediated synthesis of magnesium oxide nanoparticles using Caccinia macranthera extract and examination of their photocatalytic and anticancer effects. Materials Research Bulletin 2024; 169, 112514.

[186] K Velsankar, K Aravinth, PSA Cláudia, Y Wang, F Ameen and S Sudhahar. Bio-derived synthesis of MgO nanoparticles and their anticancer and hemolytic bioactivities. Biocatalysis and Agricultural Biotechnology 2023; 53, 102870.

[187] K Karthik, S Dhanuskodi, SP Kumar, C Gobinath and S Sivaramakrishnan. Microwave assisted green synthesis of MgO nanorods and their antibacterial and anti-breast cancer activities. Materials Letters 2017; 206, 217-220.

[188] R Dobrucka. Synthesis of MgO nanoparticles using Artemisia abrotanum herba extract and their antioxidant and photocatalytic properties. Iranian Journal of Science and Technology, Transactions A: Science 2018; 42, 547-555.

[189] R Periakaruppan, V Naveen and J Danaraj. Green synthesis of magnesium oxide nanoparticles with antioxidant potential using the leaf extract of Piper nigrum. JOM 2022; 74, 4817-4822.

[190] R Periakaruppan, P Vanathi and KSV Selvaraj. Phyto-synthesis, characterization of magnesium oxide nanoparticles using aqueous extract of Piper betle leaf and an assessment of its antioxidant potential. Biomass Conversion and Biorefinery 2023. https://doi.org/10.1007/s13399-023-05116-6.

[191] S Ali, KG Sudha, M Thiruvengadam and R Govindasamy. Biocompatible synthesis of magnesium oxide nanoparticles with effective antioxidant, antibacterial, and anti-inflammatory activities using Magnolia champaca extract. Biomass Conversion and Biorefinery 2024; 14, 21431-21442.

[192] L Umaralikhan and MJM Jaffar. Green synthesis of MgO nanoparticles and its antibacterial activity. Iranian Journal of Science and Technology Transactions A: Science 2016; 42, 477-485.

[193] A Fatiqin, H Amrulloh and W Simanjuntak. Green synthesis of MgO nanoparticles using Moringa oleifera leaf aqueous extract for antibacterial activity. Bulletin of the Chemical Society of Ethiopia 2021; 35(1), 161-170.

[194] RB Rotti, DV Sunitha, R Manjunath, A Roy, SB Mayegowda, AP Gnanaprakash, S Alghamdi, M Almehmadi, O Abdulaziz, M Allahyani, A Aljuaid, AA Alsaiari, SS Ashgar, AO Babalghith, AEA El-Lateef and EB Khidir. Green synthesis of MgO nanoparticles and its antibacterial properties. Frontiers in Chemistry 2023; 11, 1143614.

[195] A Akshaykranth, N Jayarambabu, VR Tumu and RK Rajaboina. Comparative study on antibacterial activity of MgO nanoparticles synthesized from Lawsonia inermis leaves extract and chemical methods. Journal of Inorganic and Organometallic Polymers and Materials 2021; 31, 2393-2400.

[196] G Sharmila, C Muthukumaran, E Sangeetha, H Saraswathi, S Soundarya and NM Kumar. Green fabrication, characterization of Pisonia alba leaf extract derived MgO nanoparticles and its biological applications. Nano-Structures and Nano-Objects 2019; 20, 100380.

[197] HR Raveesha, S Nayana, DR Vasudha, JS Begum, S Pratibha, CR Ravikumara and N Dhananjaya. The electrochemical behavior, antifungal and cytotoxic activities of phytofabricated MgO nanoparticles using Withania somnifera leaf extract. Journal of Science: Advanced Materials and Devices 2019; 4(1), 57-65.

[198] H Dabhane, S Ghotekar, M Zate, S Kute, G Jadhav and V Medhane. Green synthesis of MgO nanoparticles using aqueous leaf extract of Ajwain (Trachyspermum ammi) and evaluation of their catalytic and biological activities. Inorganic Chemistry Communications 2022; 138, 109270.

[199] S Manzoor, G Yasmin, N Raza, J Fernandez, R Atiq, S Chohan, A Iqbal, S Manzoor, B Malik, F Winter and M Azam. Synthesis of polyaniline coated magnesium and cobalt oxide nanoparticles through eco-friendly approach and their application as antifungal agents. Polymers 2021; 13(16), 2669.