Trends Sci. 2025; 22(6): 9924

Multifunctional Hybrids of Graphene Quantum Dots with Inorganic Nanoparticles (Metal, Metal Oxide and MOF) - Topical State and Evolutions

Ayesha Kausar

National Center for Physics, Quaid-i-Azam University Campus, Islamabad, Pakistan

(Corresponding author’s e-mail: [email protected])

Received: 2 February 2025, Revised: 16 February 2025, Accepted: 23 February 2025, Published: 1 April 2025

Abstract

Carbon based quantum dots have been discovered as unique florescent nanoentities having different types, such as carbon nanodots, graphene quantum dots, and polymer dots. Out of these, graphene quantum dots can be seen as zero dimensional derivatives of graphene (2 dimensional nanosheet). Due to recent advancement in the field of graphene quantum dots, various inorganic and organic hybrids have been reported in the literature so far. In this concern, inorganic nanoparticles like metal, metal oxide, as well as metal organic framework (MOF) have been used to design graphene quantum dots/metal nanoparticles, graphene quantum dots/metal oxide nanoparticles, and graphene quantum dot/MOF type hybrids. These nanomaterials have been designed using efficient synthesis strategies including hydrothermal, solvothermal, freeze dying, solution, in situ, and several other methods. Accordingly, this state-of-the-art review article aims to highlight advantageous physical properties, such as microstructure, electron/charge conduction, florescence, catalytic activity, etc., in addition to dispersion, compatibility, and interface formation of graphene quantum dots with inorganic nanoparticles. Consequently, high tech application areas of graphene quantum dots/inorganic nanoparticle hybrids have been identified for optical sensors, supercapacitors, photocatalysts for environmental treatment, and antimicrobials for wound healing purposes. Despite the success of graphene quantum dots/inorganic nanoparticle hybrids so far, focused future research efforts on these nanomaterials may lead to large/commercial scale applications in energy, electronics, environment, and biomedical fields by overcoming underlying design/synthesis/performance challenges.

Keywords: Graphene quantum dots, Metal/metal oxides, MOF, Hybrids, Optical sensors, Photocatalysts, Wound healing

Introduction

Graphene, since its discovery, has been analyzed for nanostructural uniqueness (1 atom thick 2 dimensional nanosheet) and remarkable physical properties (electronic, electrical, thermal, mechanical) [1]. Wide ranging top down and bottom-up synthesis methods have been used for the fabrication of graphene and its modified nanostructures. Consequently, pristine graphene and resulting hybrids exhibited promising applications in the fields of photovoltaics, light emitting diodes, fuel cells, sensing/capacitive devices, charge storage batteries, ecological materials, biomedical appliances, and countless other technological areas [2,3]. Due to synthesis and optimal property challenges of graphene, its modified forms and nanocomposites have been reported for high end advancements in the potential applied areas [4].

In this regard, graphene quantum dots appeared as inimitable graphene derivatives [5]. Graphene quantum dots are basically a type of carbon based quantum dots, besides carbon nanodots and polymers dots. Like pristine graphene, graphene quantum dots have also been investigated for their fabrication, properties, and applications as advanced hybrid nanostructures [6,7]. Similar to other quantum dots, graphene quantum dots revealed quantum confinement, edge/surface effects, florescence, and other advantageous physical properties [8]. Consequently, graphene quantum dots have been studied for valuable energy/electronics and biomedical (bioimaging, biosensing, drug delivery, etc.) applications [9,10]. In the form of hybrid nanostructures, graphene quantum dots have superior dispersion, tunable nanostructure, adjustable properties, and high tech applications [11]. In this concern, high performance inorganic hybrids of graphene quantum dots have been designed using metal nanoparticles [12], metal oxides [13], and metal organic frame (MOF) [14]. According to the literature so far, applications of graphene quantum dot/inorganic nanoparticle hybrids have been noted for electronic devices, energy devices, environmental treatments, and biomedical areas [15,16]. Despite the to date technical success of graphene quantum dots/inorganic hybrids, several existing field challenges have been observed for these nanomaterials, which can be overcome via focused future research investigations by the field scientists [17-19].

This novel review article has been designed to emphasize almost every possible structural, synthesis, physical property, and applied prospect of graphene quantum dot and metal, metal oxide, and MOF derivative hybrids. In this regard, important graphene quantum dot/inorganic designs, morphological, conducting, florescence, catalytic, and other physical features have been reported in the literature so far. Nevertheless, future progress and industrial scale uses of graphene quantum dot/inorganic hybrids can be achieved through comprehensive research attempts to overcome underlying design, compatibility, and processing challenges to enhance structure-property-performance relationships of these nanomaterials [20,21].

Graphene quantum dot hybrids with metal nanoparticles

Graphene quantum dots have been modified to form hybrid nanostructures using numerous functional nanomaterials [22,23]. In this concern, metal nanoparticles have been considered as promising nanoadditives for graphene quantum dots to design hybrid nanostructures [24,25]. As per scientific data, pristine metal nanoparticles and their nanocomposites have been researched for widespread technical applications, ranging from engineering materials and electronic/energy devices to biomedical (drug transfusion, bioimaging, etc.) sectors [26-28]. Accordingly, metal nanoparticle based nanocomposites have been designed using matrices, such as polymers, carbon, and inorganic nanomaterials (metal/metal oxide) [29,30]. Consequently, literature reports have been observed on design/fabrication, physiochemical characteristics, and applications of variety of metal nanoparticles (gold, silver, iron, zinc, copper, etc.) and related hybrids [31-33]. It seems that due to nanolevel sizes, interfacial interactions, and compatibility, metal nanoparticles can develop synergistic structural and functional relationships with graphene quantum dots [34,35]. In this regards, we found a number of scientific surveys up till now on the hybrids of graphene quantum dots with metal nanoparticles [36]. Notably, Ibarra et. al. [37] applied hydrothermal technique for the formation of graphene quantum dots using various nanocarbon precursors, including graphene, carbon nanotube, and amorphous carbon. Then, high performance nitrogen doped graphene quantum dots and gold (Au) nanoparticle based hybrids were also hydrothermally synthesized. Figures 1A(a) and 1A(b) show transmission electron microscopy micrographs of graphene quantum dots (prepared using graphene precursor). Graphene quantum dots can be observed as hexagonal nanoparticles of 20 - 50 nm occurring as aggregates. Figures 1A(c) and 1A(d) show transmission electron microscopy micrographs of nitrogen doped graphene quantum dots/gold nanoparticle hybrids. As per images, Au nanoparticles (lattice spacing 0.24 nm) seemed to be uniformly dispersed within the nitrogen doped graphene quantum dots aggregates, due to interfacial coupling effects between these nanoparticles. Figures 1B(a) and 1B(b) show color differences of graphene derived nanodots in visible light (reddish brown) and UV light (bluish green), respectively. In addition, Figure 1(C) demonstrates photoluminescence spectra of graphene quantum dots, which were hydrothermally prepared by different nanocarbon sources. Accordingly, graphene, carbon nanotube, and amorphous carbon depicted emission peaks at 488, 490, and 496 nm, respectively. Here, photoluminescence features of the nanodots were seemed to be dependent upon their sizes (according to precursor nanocarbon used during their synthesis) as well as quantum confinement effects.

Zhang et al. [38] applied hydrothermal technique to form nitrogen doped graphene quantum dots using green precursors (hydroxyethyl cellulose/L-citrulline). Afterwards, hybrids of graphene quantum dots with silver (Ag) nanoparticles were prepared using silver nitrate salt, in a solution method (Figure 2(A)). Figures 2B(a) and 2B(b) show transmission electron microscopy micrographs of nitrogen doped graphene quantum dots and nitrogen doped graphene quantum dots/Ag hybrid, respectively. As per results, pristine nitrogen doped graphene quantum dots had uniform spherical morphology, whereas nitrogen doped graphene quantum dots/Ag hybrid revealed dispersion of silver nanoparticles attached to quantum dot surfaces. In high resolution transmission electron microscopy micrograph, a clear interface formation can be seen between the nanodots and inorganic nanoparticles (Figure 2B(c)). Consequently, Figures 2(C) and 2(D) show florescence excitation and emission spectra of graphene quantum dots and their nanocomposites, respectively. As per results, nitrogen doped graphene quantum dots depicted narrow emission band (400 - 495 nm) due to narrow particle size distribution. The hybrid revealed excitation and emission bands at 340 and 408 nm, respectively. Accordingly, nitrogen doped graphene quantum dots/Ag hybrid was found efficient as a photocatalyst for H₂O₂ induced florescence for uric acid detection.

In this way, we analyzed effectiveness of few important designs of metal nanoparticle (Ag, Au, Pt, Cu, Fe, etc.) functional graphene quantum dots in the fields of energy devices, sensors/electronics, catalysis, and biomedical sectors [39-41].

Figure 1 (A) Transmission electron microscopy images of (a,b) graphene quantum dots obtained from graphene; (c,d) nitrogen doped graphene quantum dots/gold nanoparticle hybrid, inset: Au nanoparticle with lattice spacing; (B) graphene quantum dots obtained from graphene via hydrothermal method: (a) Daylight image with brown reddish color; (b) florescence in the same; (C) photoluminescence (PL) of graphene quantum dots obtained from different nanocarbons hydrothermally [37]. Reproduced with permission from MDPI.

Figure 2 (A) Schematic illustration of the preparation of silver nanoparticle modified nitrogen doped graphene quantum dots (AgNPs/N-CQDs) used for uric acid detection; (B) transmission electron microscopy image of: (a) Nitrogen doped graphene quantum dots (N-CQDs); and (b) AgNPs/N-CQDs; (c) high resolution transmission electron microscopy image of AgNPs/N-CQDs; (C) florescence excitation and emission spectra of N-CQDs; (D) florescence excitation and emission spectra and UV absorption for AgNPs/N-CQDs [38]. Reproduced with permission from MDPI.

Combination of graphene quantum dot with metal oxide/inorganic nanoadditives

As mentioned above, modification of graphene quantum dots using metal nanoentities showed advantageous enhancements in electronic, electrical, thermal, catalytic, and biocompatibility characteristics of the resulting graphene quantum/inorganic nanoparticle hybrids [42,43]. Besides metal nanoparticles, hybrids of metal oxides and graphene quantum dots have been designed and investigated for their physical or covalent interactions [44-46]. Metal oxides (crystalline solids) nanoparticles usually consist of metal cations and oxide anions [47]. Pristine metal oxides as well as metal oxide hybrids have been manufactured via number of efficient synthesis techniques, including in situ, solution, sol gel, template, and hydrothermal approaches [48]. Like metal nanoparticles, metal oxides have also been frequently studied in the literature for their significant physical properties and myriad of technical applications, ranging from solar cells and sensors to drug delivery and other biomedical areas [49]. Accordingly, graphene quantum dots/metal oxide nanoparticles hybrids have been explored for photovoltaic, catalytic, water splitting, environmental, and other technological applications [50-52]. In this concern, graphene quantum dots/metal oxide hybrids seemed to develop promising heterointerfaces responsible for their advanced applications in ecological photoelectrochemical energy production devices, such as fuel cells, perovskite solar cells, etc. [53-55]. Among inorganic metal oxide nanoparticles, Sudhagar et. al. [56] designed hybrids of titania (TiO₂) with graphene quantum dots. For this, hollow nanowires of TiO₂ (100 - 200 nm) were developed and decorated with graphene quantum dots on their surfaces. The ensuing graphene quantum dots/TiO₂ nanowire hybrids had superior photocharge carrying properties and 70 % higher photocurrent, than pristine nanowires. These results were attributed to mutual structure-property associations of graphene quantum dots and TiO₂ nanowires, thereby leading to advanced photocharge transfer characteristics. Raghavan et al. [57] manufactured graphene quantum dots and TiO₂ based hybrids via facile sonication and hydrothermal techniques, as shown in Figure 3(A).

Figure 3 (A) Scheme for preparation of graphene quantum dots (GQD) and titania (TiO₂) based photocatalyst for H₂ production; (B) sensitizing effect and cocatalytic role of GQD deposited on TiO₂ for improved photocatalytic H₂ evolution under solar light, here VB = valance band; CB = conduction band; (C) (a,c) high resolution transmission electron microscopy images of graphene quantum dots/titania hybrids [57]. Reproduced with permission from ACS.

The 5 - 20 wt.% TiO₂ nanoparticles were used to form hybrid with graphene quantum dots. Figure 3(B) shows visible light and UV light irradiation based studies to explore photosensitization effects of these hybrids. Due to band gap of 2.26 eV and electron/charge transference, graphene quantum dots were found efficient to enhance photosensitization and photocatalytic activity of TiO₂ nanoparticles in these nanohybrids. Here, photocatalytic activity of TiO₂ seemed to be promoted by quantum dots through inducing recombination/parting of charge carriers. According to high resolution transmission electron microscopy micrographs in Figures 3C(a) and 3C(b), tiny TiO₂ nanoparticles (~ 20 nm) can be seen dispersed on graphene quantum dots surfaces. Accordingly, these inorganic nanoparticles had lattice plane and spacing of (101) and 0.36 nm, respectively. In this way, graphene quantum dots/TiO₂ hybrids were designed as environmentally benign photocatalysts for H₂ production.

Badrigilan et al. [58] established a hybrid combination of graphene quantum dots with iron oxide and bismuth oxide nanoparticles. They used facile solution route for the formation of resulting graphene quantum dots/iron/bismuth oxides nanocomposites. Technically, these hybrids were found effective for photothermal therapy showing > 50 % killing efficiency for malignant cells. Xi et al. [59] designed unique hollow nanocomposite nanospheres of nitrogen doped graphene quantum dots, carbon, and palladium (Pd) nanoparticles. For hybrid nanoparticle fabrication, initially silica nanoparticle functional graphene quantum dots were prepared and subsequently converted to polydopamine functional silica/graphene quantum dots nanostructures (Figure 4(A)). Next, Pd nanoparticles were in situ synthesized on silica/graphene quantum dots/polydopamine nanohybrid surfaces. Further annealing and processing led to the formation of hollow nitrogen doped graphene quantum dots/carbon/Pd nanospheres. Figure 4(B) shows transmission electron microscopy micrographs of hollow nanocomposite nanoparticles of nitrogen doped graphene quantum dots/carbon/Pd hybrids. Tiny Pd nanoparticles (< 3 nm in size) can be seen uniformly dispersed on hollow nitrogen doped graphene quantum dots (10 - 30 nm average sizes) surfaces. Such Pd nanoparticle functional nanodots revealed catalytic properties beneficial for H₂O₂ sensing purposes. Figure 4(C) shows a view on biosensing performance of nitrogen doped graphene quantum dot and Pd derived hollow nanospheres. The H₂O₂ sensing properties of finally obtained polydopamine/silica/graphene quantum dot-Pd nanoparticle nanostructures were examined for malignant cell treatment.

Hence, different combinations of graphene quantum dots with metal oxide nanoparticles (silica, titania, iron oxide, bismuth oxide, etc.) have been reported in the literature so far. Depending upon the type of metal oxide nanoparticles used and synergistic effects between graphene quantum dots-metal oxide hybrid nanoparticles, valuable applications in the fields of energy, catalysis, and biomedical sectors have been discovered by the field scientists till date.

Hybrids of graphene quantum dot and MOF

Metal organic framework or MOF constitutes an important category of porous hybrid nanostructures having metal ions connected via organic linkers and effective bonding [60]. In spite of technically desirable high surface area and porosity features, MOF nanoparticles had limited temperature stability under extreme pyrolysis conditions [61]. Therefore, to enhance practical applications of MOF, its functional nanocomposites have been designed using a number of inorganic (metal/metal oxide) and carbon nanoparticles [62-64]. Nevertheless, formation of high end MOF hybrids often faces challenges of structural compatibility and facile processing [65-67]. Noteworthy applications of pristine MOF as well as derived nanomaterials have been observed in the fields of electronics, energy maneuvers, medical, and environmental systems [68]. Accordingly, we found research attempts regarding technical designs of MOF hybrids with graphene/graphene oxide [69,70]. Subsequently, graphene quantum dots (as unique graphene derivatives) have been composited with MOF nanoparticles to investigate their structural-property synergies and related unique physical properties [71,72].

Figure 4 (A) Formation of NGQDs@NC@Pd HNSs; (1) amino-functionalization of SiO₂ nanospheres; (2) SiO₂ nanospheres wrapping with GQD nanosheets; (3) PDA coating on SiO2@GQD surface; (4) Pd NPs loading on SiO₂@GQD@PDA surface; (5) NGQD@NC@Pd HNSs formation by carbonization and hydrogen fluoride (HF) etching; (B) (a-c) transmission electron microscopy images of NGQDs@NC@Pd HNSs at different magnifications; (C) biosensing prospects of Pd nanoparticles decorated N doped graphene quantum dots [59]. Pd = Palladium; NPs = nanoparticles; GQD = graphene quantum dots; NGQD@NC@Pd HNSs = nitrogen doped graphene quantum dots@nitrogen doped carbon@Palladium/hollow structured nanospheres; PDA = polydopamine; SiO₂@GQD = silica@graphene quantum dots; SiO₂@GQD@PDA = silica@graphene quantum dots@polydopamine; SiO₂@GQD@PDA@Pd = silica@graphene quantum dots@polydopamine@Palladium. Reproduced with permission from ACS.

Xu et al. [73] adopted a unique method for the formation of nitrogen doped graphene quantum dots using zinc (Zn) based MOF or zeolitic imidazolate framework. For this purpose, they first converted zeolitic imidazolate framework into carbonized zeolitic imidazolate framework as a carbon source/precursor for the formation of nanodots. Later, nitrogen doped graphene quantum dots were prepared via solution, autoclave, and sonication techniques (Figure 5(A)). Figure 5(B) shows transmission electron microscopy and high resolution transmission electron microscopy images for the resulting graphene quantum dots. The tiny nanoparticles had small diameter of ~ 2 nm showing the success of synthesis method used. In addition, nitrogen doped graphene quantum dots own lattice spacing and plane of about 0.214 nm and (100), respectively. Figure 5(C) exhibits UV-VIS spectral studies on nitrogen doped graphene quantum dots with adsorption peak at 227 nm and blue shift at 200 nm due to π-π* transitions. In addition, weak/broad adsorption peaks (290 - 350 nm) were observed due to electron withdrawing properties of surface functionalities of nanodots.

Figure 5 (A) Synthesis of nitrogen doped graphene quantum dots (N-GQDs) from zeolitic imidazolate framework (ZIF-8) and carbonized zeolitic imidazolate framework (ZIF-8C) as precursor; (B) transmission electron microscopy image of N-GQDs, inset: High resolution transmission electron microscopy image of graphitic layers of a single nanodot; and (C) UV-VIS absorption spectrum of N-GQDs dispersed in water, inset: Adsorption peaks at 290 and 350 nm and photographs of N-GQD solution IN: (Left) ambient and (right) UV light (365 nm) [73]. Reproduced with permission from RSC.

Tian et al. [74] formed a Zn based MOF, i.e., zeolitic imidazolate framework-8, zeolitic imidazolate framework-8/graphene quantum dots, and doxorubicin/ zeolitic imidazolate framework-8/graphene quantum dots nanocomposites using simple solution, sonication, and centrifugation techniques. Figures 6(A) - 6(F) show scanning electron microscopy and transmission electron microscopy studies on these nanoparticles. Here, zeolitic imidazolate framework-8 and its nanocomposites with graphene quantum dots had sizes ~ 50-100 nm. Conversion of zeolitic imidazolate framework-8 to zeolitic imidazolate framework-8/graphene quantum dots caused slight increase in nanoparticle sizes, however surface uniformity remained same both for pristine metal organic frame work and nanodot nanocomposites. Figure 6(G) illustrated thermogravimetry analysis thermograms showing slightly lower maximum degradation temperature for doxorubicin/zeolitic imidazolate framework-8/graphene quantum dots hybrids, relative to zeolitic imidazolate framework-8/graphene quantum dots, due to degradation of doxorubicin functionalities in structure. The ensuing doxorubicin/zeolitic imidazolate framework-8/graphene quantum dots were suggested useful for photothermal therapies in biomedical field.

Figure 6 (A) Scanning electron microscopy image and transmission electron microscopy micrographs of: (A,D) ZIF-8; (B,E) ZIF-8/GQD; and (C,F) DOX-ZIF-8/GQD nanoparticles, respectively; (G) thermogravimetric analysis of ZIF-8, ZIF-8/GQD, and DOX-ZIF-8/GQD nanoparticles [74]. ZIF-8 = zeolitic imidazolate framework; ZIF-8/GQD = zeolitic imidazolate framework-8/graphene quantum dots; DOX-ZIF-8/GQD = doxorubicin/zeolitic imidazolate framework-8/graphene quantum dots. Reproduced with permission from ACS.

Tang et al. [75] prepared graphene quantum dots/Zn-MOF hybrids using solvothermal and solution techniques. These hybrids showed high specific surface area, of about 1,841 m² g⁻¹ and facilitated electron and charge transfer characteristics due to well interconnected 3 dimensional nanostructures. Accordingly, graphene quantum dots/Zn-MOF hybrids were further studied for application as high performance supercapacitor electrode showing superior specific capacitance and capacitance retention of around 200 F g⁻¹ and 53 %, correspondingly. Yu et al. [76] designed graphene quantum dots and Zn based metal organic framework (zeolitic imidazolate framework-8) based nanomaterials. In this concern, zeolitic imidazolate framework-8/graphene quantum dots, carbon/zeolitic imidazolate framework-8, and carbon/zeolitic imidazolate framework-8/graphene quantum dots nanocomposites were synthesized by facile solution and carbonization techniques. The resultant nanoporous nanomaterials depicted superior surface area of ~ 668 m² g⁻¹. Figure 7(A) shows uniform surface morphology with hexagonal shaped (~100 nm) zeolitic imidazolate framework-8/graphene quantum dots hybrid nanoparticles. Development of unique microstructures pointed towards the effectiveness of synthesis techniques for self-assembly growth processes during hybrid nanoparticle fabrication. Figures 7(B) and 7(C) depict nanostructures of carbon/zeolitic imidazolate framework-8, and carbon/zeolitic imidazolate framework-8/graphene quantum dots nanoparticles, respectively, formed after calcination. The annealing and carbonization seemed to develop rough surface morphologies of these nanoparticles. According to cycling stability performance measured by specific capacity and coulombic efficiency (Figure 7(D)), carbon/zeolitic imidazolate framework-8/graphene quantum dots had superior charge-discharge capacity of 400 - 800 mAh g⁻¹ and columbic efficiency up to 100 %, as lithium battery electrodes. In addition, these hybrid electrodes showed prolonged cyclic stability in ∼ 10,000 charge-discharge cycles. These resulted can be attributed to synergic effects of graphene quantum dots with porous zeolitic imidazolate framework-8; thereby enhancing overall electrochemical performance for battery electrode application.

Incidentally, high end graphene quantum dots/MOF hybrids have been detected competent for energy devices [77,78], catalysis/electronics [79,80], and biomedical [81,82], etc.

Figure 7 Transmission electron microscopy images of (A) ZIF-8@GQDs; (B) C(ZIF-8); (C) C(ZIF-8)@GQDs; and (D) cycling stability performance at 100 mA g⁻¹ of C(ZIF-8)@GQDs based anode [76]. ZIF-8@GQDs = zeolitic imidazolate framework-8@graphene quantum dots; C(ZIF-8) = carbon/zeolitic imidazolate framework-8; C(ZIF-8)@GQDs = carbon/zeolitic imidazolate framework-8@graphene quantum dots. Reproduced with permission from RSC (Open access).

Prospects of graphene quantum dots/inorganic nanoparticle hybrids

Carbon based quantum dots and related nanomaterials have attracted increasing scientific interests due to quantum/surface/edge effects and physico-chemical properties; thereby leading to their high end uses in industrial level applications [83,84]. Particularly, graphene quantum dots (an important type of carbon nanodots), have been studied for myriad of applications in the fields of energy/electronics, engineering, and biomedical systems [84-86]. Among efficient techniques used for graphene quantum dots synthesis, hydrothermal method, chemical vapor deposition, microwave/plasma strategies, and chemical/ electrochemical approaches have been observed in the literature till date [87]. As discussed in above sections of this review, research progresses in the field of graphene quantum dots resulted in a number of advanced organic-inorganic hybrids of graphene quantum dots with metal, metal oxide, and MOF nanoparticles. Consequently, we noticed technical applications of graphene quantum dots hybrids as luminescent sensors for environmental and biomedical related uses [88,89]. Accordingly, Figure 8 shows few important application areas of graphene quantum dot hybrids as luminescent devices [90]. For example, graphene quantum dots/metal nanoparticle hybrids have been designed as optical sensors and other optoelectronics [91]. Such sensors have been found efficient for detection and eradication of hazardous metal ion from environment (water or air media) [92,93]. Consequently, graphene quantum dots/metal nanoparticle hybrids based optical sensors depicted superior efficiency, selectivity, and sensitivity for toxic ion removal from water [94-96]. In addition, effectiveness of these sensors for trace metal ion detection has been analyzed through surface enhanced Raman spectroscopy (SERS) technique [97]. Henceforward, graphene quantum dots/inorganic nanoparticle hybrids derived SERS florescent sensors have been found competent for important environmental applications [98].

Figure 8 Graphene quantum dot and related nanocomposites in sensing technology [90]. Reproduced with permission from MDPI.

Another important application of graphene quantum dots/inorganic nanoparticle hybrids has been found in the field of capacitive devices [99]. For instance, Xiaoshan et al. [100] designed boron doped graphene quantum dot and inorganic Nb₉VO₂₅ nanoparticles based supercapacitor electrodes. Here, Nb₉VO₂₅ (an inorganic nanomaterial) was formed by coordination of Nb(V) and V(V). Combining boron doped graphene quantum dot with Nb(IV)/V(IV) developed efficient electron transfer paths and narrowed bandgap for rapid charge/electron flow through the hybrid nanostructure. In addition, graphene quantum dot/Nb₉VO₂₅ hybrid had tunable nanostructure, doping, conductivity, and capacitance properties. The resulting supercapacitor showed high energy density of ~ 77 – 146 W h kg⁻¹, specific capacitance of ~ 138 - 263 F g⁻¹, and > 95 % capacitance retention over 10,000 cyclic recitals.

In biomedical sectors, graphene quantum dots/metal nanoparticle hybrids have been used for wound healing purposes [101-103]. In this concern, Norouzi et al. [104] fabricated graphene quantum dot-TiO₂-graphene oxide hybrid mats for wound dressing application though an electrospinning technique. These nanomaterials had optimum water resistance and biodegradability properties for safe wound healing applications. Moreover, water contact angle studies on graphene quantum dot-TiO₂-graphene oxide hybrid mats depicted hydrophilicity nature for better wound treatment. In addition, mechanical stability studies for effective prolonged use of graphene quantum dot-TiO₂-graphene oxide hybrids demonstrated superior strength and flexibility properties due to their uniform and interracially compatible interlinked porous nanostructures. Hence, graphene quantum dot/TiO₂ hybrids were applied as efficient wound healers due to antibacterial activity against Gram-negative and Gram-positive bacterial strains.

Similar to metal and metal oxide nanoparticles, outstanding applications of graphene quantum dot/MOF hybrids have been reported for lithium ion batteries [105], supercapacitors [106], radiation shielding [107], environmental purposes [108], and biomedical sectors, such as drug delivery [109]. For example, Wei et al. [110] designed nanocomposite of graphene quantum dots and zinc-MOF for photocatalytic applications. The resulting graphene quantum dot/Zn-MOF hybrid was investigated as a photocatalyst for carbon dioxide CO₂ conversion. These hybrids exhibited superior photocatalytic CO₂ conversion efficiency due to rapid electron-hole pair generation. Hence, environmental remediation application of graphene quantum dot/MOF hybrid has been well established in the literature.

Conclusions and views

Conclusively, this revolutionary review highlights designs, fabrication, properties, and applied aspects of graphene quantum dots and their hybrids with inorganic nanoparticles, like metal, metal oxide, and MOF. Combination of graphene quantum dot with inorganic nanoparticles developed compatible interfaces and mutual interactions; thereby enhancing microstructural, electrical/charge conductivity, florescence, catalytic/ photocatalytic, ion recognition, and antimicrobial effects. Accordingly, we observed applications of graphene quantum dots/inorganic nanoparticles hybrids in the fields of sensors, energy devices, and biomedical fields. Nevertheless, as per literature availability so far, we can say that research and progress on these multifunctional hybrid materials are still in primary stages. Hence, we suggest comprehensive and focused scientific investigations to form high performance graphene quantum dot/inorganic nanomaterials for future industrial scale applications for optoelectronics (sensors), energy devices (solar cells, batteries and supercapacitors), environmental remediation, and biomedical (antimicrobials and drug transfusion) fields.

Henceforth, fundamentals and technological potential of graphene quantum dots/inorganic nanomaterials have been argued in this manuscript. Nevertheless, literature up till now include random research reports on these technically viable hybrids and no systematic studies conducted so far towards commercial level deployments. As per our analysis, systematic fabrication of these hybrids using predefined and optimum synthesis conditions seems indispensable for their commercial scale applications. For that reason, concerned field researchers must perform in-depth research investigations on graphene quantum dots based hybrids to overcome challenges of possible toxicity, impurities, uncontrolled nanoparticle sizes, design reproducibility, low quantum yields, low photoluminescence, aggregation, low electron/charge conductivity, and nanodot-inorganic nanoparticle synergies; thereby enhancing their commercial scalability for future devices and environment related industries. In this regard, we suggest use of green synthesis approaches and ecological or biodegradable precursors, and nontoxic solvents and reagents to reduce greenhouse emissions and related environmental burden. Furthermore, graphene nanodots and derived hybrids need to be comprehensively investigated for their cradle to grave life cycle and influence on our ecosystem.

References

1. P Praiypan and U Pinsook. Impact of electron-phonon coupling on graphene intercalation compounds from self energy: Polynomial models selection. Trends in Sciences 2024; 21(8), 7907.

2. S Anitasari, HS Budi, YK Shen, S Yani and N Tandirogang. Optimizing the pore structure and geometry of polycaprolactone/graphene scaffold to promote osteogenesis. Trends in Sciences 2024; 21(11), 8297.

3. B Liu, J Sun, J Zhao and X Yun. Hybrid graphene and carbon nanotube-reinforced composites: Polymer, metal, and ceramic matrices. Advanced Composites and Hybrid Materials 2025; 8, 1.

4. M Dahiya, V Khanna and N Gupta. Computational studies of graphene reinforced nanocomposites: Techniques, parameters, and future perspectives. ECS Journal of Solid State Science and Technology 2024; 13(6), 061005.

5. R Garreis, C Tong, J Terle, MJ Ruckriegel, JD Gerber, LM Gächter, K Watanabe, T Taniguchi, T Ihn, K Ensslin and WW Huang. Long-lived valley states in bilayer graphene quantum dots. Nature Physics 2024; 20, 428-434.

6. Y Yan, J Gong, J Chen, Z Zeng, W Huang, K Pu, J Liu and P Chen. Recent advances on graphene quantum dots: From chemistry and physics to applications. Advanced Materials 2019; 31(21), 1808283.

7. H Cho, G Bae and BH Hong. Engineering functionalization and properties of graphene quantum dots (GQDs) with controllable synthesis for energy and display applications. Nanoscale 2024; 16(7), 3347-3378.

8. S Kadian, SK Sethi and G Manik. Recent advancements in synthesis and property control of graphene quantum dots for biomedical and optoelectronic applications. Materials Chemistry Frontiers 2021; 5(2), 627-658.

9. P Kumar, C Dhand, N Dwivedi, S Singh, R Khan, S Verma, A Singh, MK Gupta and S Kumar. Graphene quantum dots: A contemporary perspective on scope, opportunities, and sustainability. Renewable and Sustainable Energy Reviews 2022; 157, 111993.

10. Y Cui, L Liu, M Shi, Y Wang, X Meng, Y Chen, Q Huang and C Liu. A review of advances in graphene quantum dots: From preparation and modification methods to application. C - Journal of Carbon Research 2024; 10(1), 7.

11. A Kalkal, S Kadian, R Pradhan, G Manik and G Packirisamy. Recent advances in graphene quantum dot-based optical and electrochemical (bio) analytical sensors. Materials Advances 2021; 2(17), 5513-5541.

12. P Mohapatra, S Behera, S Sahoo, A Mishra, A Kesh, L Shubhadarshinee, BR Jali, P Mohapatra and AK Barick. Synergistic effect of silver nanoparticles decorated graphene quantum dots nanohybrids reinforced polyaniline ternary nanocomposites on optical, thermal, and dielectric properties. Composite Interfaces 2025; 32(1), 1-26.

13. M Madadi, MR Moghadam, P Salarizadeh, A Bazmandegan-Shamili and M Shahbakhsh. Sensitive electrochemical detection of dopamine using CuCo₂O₄/graphene quantum dots-modified carbon paste electrode. Inorganic Chemistry Communications 2025; 171, 113566.

14. R Ghasemzadeh and K Akhbari. Degradation of acid blue 41 with carbon quantum dots@ MOF-808 nanocomposite as a biocompatible photocatalyst under visible light. Journal of Photochemistry and Photobiology A: Chemistry 2025; 458, 115984.

15. JP Rodríguez-Caicedo, DR Joya-Cárdenas, MA Corona-Rivera, N Saldaña-Robles, CE Damian-Ascencio and A Saldaña-Robles. Efficiency of graphene quantum dots in water contaminant removal: Trends and future research directions. Water 2025; 17(2), 166.

16. SS Purohit, S Patra and SK Swain. Fluorescent carbon nanoparticles based biosensors. Elsevier, Amsterdam, The Netherlands, 2025. p. 337-366.

17. R Shaheen and MA Hanif. Nanocomposite materials for decontamination of highly toxic acid dye from aqueous streams. International Journal of Environmental Analytical Chemistry 2024. https://doi.org/10.1080/03067319.2024.2301926

18. N Nesakumar, S Srinivasan and S Alwarappan. Graphene quantum dots: Synthesis, properties, and applications to the development of optical and electrochemical sensors for chemical sensing. Microchimica Acta 2022; 189, 258.

19. L Cui, X Ren, M Sun, H Liu and L Xia. Carbon dots: Synthesisproperties and applications. Nanomaterials 2021; 11(12), 3419.

20. MH Karami, M Abdouss, A Rahdar and S Pandey. Graphene quantum dots: Background, synthesis methods, and applications as nanocarrier in drug delivery and cancer treatment: An updated review. Inorganic Chemistry Communications 2024; 161, 112032.

21. A Aly, M Ghali, A Osman and MK El Nimr. Non-synthetic luminescent graphene quantum dots in coconut water for aniline sensing applications. Materials Research Bulletin 2024; 171, 112603.

22. YJ Hsiao and LY Lin. Enhanced surface area, graphene quantum dots, and functional groups for the simple acid-treated carbon fiber electrode of flexible fiber-type solid-state supercapacitors without active materials. ACS Sustainable Chemistry & Engineering 2020; 8(6), 2453-2461.

23. A Gouda, A Masson, M Hoseinizadeh, F Soavi and C Santato. Biosourced quinones for high-performance Santatoentally benign electrochemical capacitors via interface engineering. Communications Chemistry 2022; 5(1), 98.

24. Y Guo, Q Huang, F Xu, Z Luo, Y Wei, Z Chen, Z Zeng, H Zhang and H Shi. A graphene quantum dots based dual-modal fluorometric and visualized detection of copper ions. Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 2025; 328, 125442.

25. M Cobos, I De-La-Pinta, G Quindós, MJ Fernández and MD Fernández. Graphene oxide–silver nanoparticle nanohybrids: Synthesis, characterization, and antimicrobial properties. Nanomaterials 2020; 10, 376.

26. AK Oyebamiji, SA Akintelu, SO Afolabi, O Ebenezer, ET Akintayo and CO Akintayo. A comprehensive review on mycosynthesis of nanoparticles, characteristics, applications, and limitations. Plasmonics 2025. https://doi.org10.1007/s11468-024-02755-x

27. EM Materón, CM Miyazaki, O Carr, N Joshi, PHS Picciani, CJ Dalmaschio and F Davis. Magnetic nanoparticles in biomedical applications: A review. Applied Surface Science Advances 2021; 6, 100163.

28. Z Du, Y Qi, J He, D Zhong and M Zhou. Recent advances in applications of nanoparticles in SERS in vivo imaging. Wiley Interdisciplinary Reviews: Nanomedicine and Nanobiotechnology 2021; 13(2), e1672.

29. F Batool, S Noreen, HY Gonadal, A Arshad, T Iqbal and S Iqbal. Waste-derived graphene for the removal of heavy metals: A sustainable approach toward environmental remediation. In: N Talreja, D Chauhan and M Ashfaq (Eds.). Waste-derived carbon nanostructures: Synthesis and applications. Springer, Cham, Switzerland, 2025, p. 149-175.

30. J Iqbal, S Ijaz, N Ijaz, BA Abbasi, T Yaseen, Z Ullah, R Iqbal, G Murtaza, Z Ashraf, T Mahmood, S Kanwal, I Ali, I Ullah and M Kazi. Microbial synthesis of metal nanoparticles for nanomedicinal and catalytic applications. In: AT Khalil and A Islam (Eds.). Expanding nanobiotechnology: Applications and commercialization. CRC Press, Boca Raton, United States, 2025, p. 88-124.

31. M Pandey, K Deshmukh and CM Hussain. Functionalized magnetic nanoparticles for theranostic applications. John Wiley & Sons, New York, 2025.

32. Z Zhao, D Wu, D Lv, X Zhang, L Chen and B Zhang. Supported of gold nanoparticles on carboxymethyl lignin modified magnetic nanoparticles as an efficient catalyst for reduction of nitroarenes and treatment of human melanoma. International Journal of Biological Macromolecules 2024; 270, 132250.

33. P Gupta, K Mishra, AK Mittal, N Handa and MK Paul. Current expansion of silver and gold nanomaterials towards cancer theranostics: Development of therapeutics. Current Nanoscience 2024; 20(3), 356-372.

34. K Bakht, A Ishaq, AM Khan, RA Khan, M Bilal, F Rabbani and AJ Shaikh. Evaluation of binding compatibility among transition metal nanoparticles towards graphene quantum dots and their magnetic properties. Journal of Nanoparticle Research 2023; 25(10), 210.

35. Y Song and S Chen. Graphene quantum-dot-supported platinum nanoparticles: defect-mediated electrocatalytic activity in oxygen reduction. ACS Applied Materials & Interfaces 2014; 6(16), 14050-14060.

36. AB Amor, H Hemmami, IB Amor, S Zeghoud, AA Alhamad, M Belkacem, NS Nair and AB Sruthimol. Advances in carbon quantum dot applications: Catalysis, sensing, and biomedical innovations. Materials Science in Semiconductor Processing 2025; 185, 108945.

37. D Ibarra, O Kharissova and I Gomez. Synthesis of graphene quantum dots coupled to au nanoparticles: A facile and versatile route using different carbon sources. C - Journal of Carbon Research 2023; 9(2), 45.

38. Q Zhang, S Du, F Tian, X Long, S Xie, S Tang and L Bao. Silver nanoparticle-functionalised nitrogen-doped carbon quantum dots for the highly efficient determination of uric acid. Molecules 2022; 27(14), 4586.

39. NAA Nazri, NH Azeman, MHA Bakar, NN Mobarak, Y Luo, N Arsad, THTA Aziz, ARM Zain and AAA Bakar. Localized surface plasmon resonance decorated with carbon quantum dots and triangular Ag nanoparticles for chlorophyll detection. Nanomaterials 2021; 12(1), 35.

40. M Tohari, A Lyras and M Alsalhi. Ultrafast energy transfer in the metal nanoparticles-graphene nanodisks-quantum dots hybrid systems. Plasmonics 2019; 14, 17-24.

41. W Saeed, Z Abbasi, M Bilal, SH Shah, A Waseem and AJ Shaikh. Interactive behavior of graphene quantum dots towards noble metal surfaces. Physica E: Low-Dimensional Systems and Nanostructures 2023; 147, 115596.

42. K Tungare, M Bhori, KS Racherla and S Sawant. Synthesis, characterization and biocompatibility studies of carbon quantum dots from Phoenix dactylifera. 3 Biotech 2020; 10(12), 540.

43. P Kamble, D Malavekar and AP Tiwari. Natural biowaste derived fluorescent carbon quantum dots: Synthesis, characterization and biocompatibility study. Journal of Fluorescence 2024; 34(1), 191-201.

44. S Kanungo, N Gupta, R Rawat, B Jain, A Solanki, A Panday, P Das and S Ganguly. Doped carbon quantum dots reinforced hydrogels for sustained delivery of molecular cargo. Journal of Functional Biomaterials 2023; 14(3), 166.

45. RA de Jesus, GC de Assis, RJ de Oliveira, JAS Costa, CMP da Silva, HMN Iqbal and LFR Ferreiraet. Metal/metal oxide nanoparticles: A revolution in the biosynthesis and medical applications. Nano-Structures & Nano-Objects 2024; 37, 101071.

46. UO Aigbe and AO Osibote. Green synthesis of metal oxide nanoparticles, and their various applications. Journal of Hazardous Materials Advances 2024; 13, 100401.

47. Y Zhu, Z Tang, L Yuan, B Li, Z Shao and W Guo. Beyond conventional structures: Emerging complex metal oxides for efficient oxygen and hydrogen electrocatalysis. Chemical Society Reviews 2025; 54(2), 1027-1092.

48. S Yadav, N Rani and K Saini. A review on transition metal oxides based nanocomposites, their synthesis techniques, different morphologies and potential applications. IOP Conference Series: Materials Science and Engineering 2022; 1225, 012004.

49. A Kaur, B Bajaj, A Kaushik, A Saini and D Sud. A review on template assisted synthesis of multi-functional metal oxide nanostructures: Status and prospects. Materials Science and Engineering: B 2022; 286, 116005.

50. X Wang, M Wang, G Liu, Y Zhang, G Han, A Vomiero and H Zhao. Colloidal carbon quantum dots as light absorber for efficient and stable ecofriendly photoelectrochemical hydrogen generation. Nano Energy 2021; 86, 106122.

51. ZW Heng, WC Chong, YL Pang and CH Koo. An overview of the recent advances of carbon quantum dots/metal oxides in the application of heterogeneous photocatalysis in photodegradation of pollutants towards visible-light and solar energy exploitation. Journal of Environmental Chemical Engineering 2021; 9, 105199.

52. L Jin, H Zhao, ZM Wang and F Rosei. Quantum dots‐based photoelectrochemical hydrogen evolution from water splitting. Advanced Energy Materials 2021; 11(12), 2003233.

53. C Cheng, Q Liang, M Yan, Z Liu, Q He, T Wu, S Luo, Y Pan, C Zhao and Y Liu. Advances in preparation, mechanism and applications of graphene quantum dots/semiconductor composite photocatalysts: A review. Journal of Hazardous Materials 2022; 424, 127721.

54. Y Yu, T Ma and H Huang. Semiconducting quantum dots for energy conversion and storage. Advanced Functional Materials 2023; 33(16), 2213770.

55. L Jin, H Zhao, ZM Wang and F Rosei. Quantum dots: Quantum dots‐based photoelectrochemical hydrogen evolution from water splitting (Adv. Energy Mater. 12/2021). Advanced Energy Materials 2021; 11(12), 1.

56. P Sudhagar, I Herraiz-Cardona, H Park, T Song, SH Noh, S Gimenez, IM Sero, F Fabregat-Santiago, J Bisquert, C Terashima, U Paik, YS Kang, A Fujishima and TH Han. Exploring graphene quantum dots/TiO₂ interface in photoelectrochemical reactions: Solar to fuel conversion. Electrochimica Acta 2016; 187, 249-255.

57. A Raghavan, S Sarkar, LR Nagappagari, S Bojja, S MuthukondaVenkatakrishnan and S Ghosh. Decoration of graphene quantum dots on TiO₂ nanostructures: Photosensitizer and cocatalyst role for enhanced hydrogen generation. Industrial & Engineering Chemistry Research 2020; 59(29), 13060-13068.

58. S Badrigilan, B Shaabani, N Gharehaghaji and A Mesbahi. Iron oxide/bismuth oxide nanocomposites coated by graphene quantum dots:“Three-in-one” theranostic agents for simultaneous CT/MR imaging-guided in vitro photothermal therapy. Photodiagnosis and Photodynamic Therapy 2019; 25, 504-514.

59. J Xi, C Xie, Y Zhang, L Wang, J Xiao, X Duan, J Ren, F Xiao and S Wang. Pd nanoparticles decorated N-doped graphene quantum dots@ N-doped carbon hollow nanospheres with high electrochemical sensing performance in cancer detection. ACS Applied Materials & Interfaces 2016; 8(34), 22563-22573.

60. B Achenbach, A Yurdusen, N Stock, G Maurin and C Serre. Synthetic aspects and characterization needs in MOF chemistry - from discovery to applications. Advanced Materials 2025. https://doi.org/10.1002/adma.202411359

61. A Kirchon, L Feng, HF Drake, EA Joseph and HC Zhou. From fundamentals to applications: A toolbox for robust and multifunctional MOF materials. Chemical Society Reviews 2018; 47(23), 8611-8638.

62. Y Feng, X Li, S Lu, R Li, Z Gong, X Shang, Y Pei, W Zheng, D Tu and X Chen. Modulator-directed assembly of hybrid composites based on metal-organic frameworks and upconversion nanoparticles. Nano Research 2023; 16(1), 1482-1490.

63. D Guo, L Chen and Y Li. MOF‐supported metal nanoparticles for catalytic applications. Catalysis in Confined Frameworks: Synthesis, Characterization, and Applications 2024. https://doi.org/10.1002/9783527839278.ch7

64. PK Sonkar and V Ganesan. Metal-organic frameworks. In: M Kathiresan and MA Kulandainathan (Eds.). Nanomaterials for sustainable energy applications. CRC Press, Boca Raton, 2024.

65. S Ramu, I Kainthla, L Chandrappa, JM Shivanna, B Kumaran and RG Balakrishna. Recent advances in metal organic frameworks-based magnetic nanomaterials for waste water treatment. Environmental Science and Pollution Research 2024; 31(1), 167-190.

66. M Hubab and MA Al-Ghouti. Recent advances and potential applications for metal-organic framework (MOFs) and MOFs-derived materials: Characterizations and antimicrobial activities. Biotechnology Reports 2024; 42, e00837.

67. A Chaouiki, S Fatimah, M Chafiq, J Ryu and YG Ko. State-of-the-art advancements in metal− organic framework nanoarchitectures for catalytic applications. Applied Materials Today 2024; 38, 102224.

68. M Davoudabadi Farahani and M Hasanzadeh. Investigation of the properties and applications of magnetic metal-organic framework (MMOF) composites for detection and removal of environmental pollutants. Advanced Materials and New Coatings 2021; 9(35), 2546-2572.

69. Z Haeri, B Ramezanzadeh and M Ramezanzadeh. Recent progress on the metal-organic frameworks decorated graphene oxide (MOFs-GO) nano-building application for epoxy coating mechanical-thermal/flame-retardant and anti-corrosion features improvement. Progress in Organic Coatings 2022; 163, 106645.

70. R Majidi, I Danaee, L Vrsalović and D Zarei. Development of a smart anticorrosion epoxy coating containing a pH-sensitive GO/MOF nanocarrier loaded with 2-mercaptobenzothiazole corrosion inhibitor. Materials Chemistry and Physics 2023; 308, 128291.

71. B Wei, X Wei, M Wang, Z Yao, Z Chen, P Chen, X He and J Zhou. Ultra-broadband microwave absorption of honeycomb-like 3-dimensional carbon foams embedded with zero-dimensional magnetic quantum dots. Journal of Alloys and Compounds 2023; 939, 168781.

72. S Mao, JW Shi, G Sun, Y Zhang, D Ma, K Song, Y Lv, J Zhou, H Wang and Y Cheng. PdS quantum dots as a hole attractor encapsulated into the MOF@Cd_0.5Zn_0.5S heterostructure for boosting photocatalytic hydrogen evolution under visible light. ACS Applied Materials & Interfaces 2022; 14(43), 48770-48779.

73. H Xu, S Zhou, L Xiao, H Wang, S Li and Q Yuan. Fabrication of a nitrogen-doped graphene quantum dot from MOF-derived porous carbon and its application for highly selective fluorescence detection of Fe³⁺. Journal of Materials Chemistry C 2015; 3(2), 291-297.

74. Z Tian, X Yao, K Ma, X Niu, J Grothe, Q Xu, L Liu, S Kaskel and Y Zhu. Metal-organic framework/graphene quantum dot nanoparticles used for synergistic chemo-and photothermal therapy. ACS Omega 2017; 2(3), 1249-1258.

75. T Tang, R Yuan, N Guo, J Zhu, X Gan, Q Li, F Qin, W Luo, L Wang, S Zhang, H Song and D Jia. Improving the surface area of metal organic framework-derived porous carbon through constructing inner support by compatible graphene quantum dots. Journal of Colloid and Interface Science 2022; 623, 77-85.

76. H Yu, W Zhu, H Zhou, J Liu, Z Yang, X Hu and A Yuan. Porous carbon derived from metal-organic framework@ graphene quantum dots as electrode materials for supercapacitors and lithium-ion batteries. RSC Advances 2019; 9(17), 9577-9583.

77. L Giri, SR Rout, RS Varma, M Otyepka, K Jayaramulu and R Dandela. Recent advancements in metal–organic frameworks integrating quantum dots (QDs@MOF) and their potential applications. Nanotechnology Reviews 2022; 11(1), 1947-1976.

78. A Sharma, DN Gopi, SM Mohammed and RK Thomas. Energy applications of metal and metal oxide nanoparticles. In: A Shukla, KH Asli, NK Rawat, AR Abraham and AK Haghi (Eds.). Technological advancement in clean energy production. Apple Academic Press, Florida, 2024, p. 75-96.

79. N Kajal, V Singh, R Gupta and S Gautam. Metal organic frameworks for electrochemical sensor applications: A review. Environmental Research 2022; 204, 112320.

80. CES Ferreira, SS Balula and L Cunha-Silva. Recent advances in catalytic compounds developed by thermal treatment of (Zr-based) metal-organic frameworks. Compounds 2024; 4(2), 315-337.

81. S Jain, M Nehra, R Kumar, N Dilbaghi and S Kumar. Quantum dots and conjugated metal-organic frameworks for targeted drug delivery and bioimaging of cancer. In: AK Kaushik, S Kumar and GR Chaudhary (Eds.). Engineered nanostructures for therapeutics and biomedical applications. Woodhead Publishing, Cambridge, 2023. p. 73-102.

82. GA Udourioh, MM Solomon, CO Matthews-Amune, EI Epelle, JA Okolie, VE Agbazue and U Onyenze. Current trends in the synthesis, characterization and application of metal-organic frameworks. Reaction Chemistry & Engineering 2023; 8(2), 278-310.

83. A Nair, JT Haponiuk, S Thomas and S Gopi. Natural carbon-based quantum dots and their applications in drug delivery: A review. Biomedicine & Pharmacotherapy 2020; 132, 110834.

84. K Barve, U Singh, P Yadav and D Bhatia. Carbon-based designer and programmable fluorescent quantum dots for targeted biological and biomedical applications. Materials Chemistry Frontiers 2023; 7(9), 1781-1802.

85. W Li, Y Wang, H Yin, J Chen, K Han, F Liu and R Zhang. Excitation-dependent emission in Sb³⁺-doped all-inorganic rare-earth double perovskites for anticounterfeiting applications. Inorganic Chemistry 2024; 63(23), 10481-10489.

86. K Barve, U Singh, P Yadav, K Kansara, P Vaswani, A Kumar and D Bhatia. Red fluorescent carbon nanoparticles derived from Spinacia oleracea L.: A versatile tool for bioimaging and biomedical applications. Materials Advances 2023; 4(23), 6277-6285.

87. N Manjubaashini, TD Thangadurai, D Nataraj and S Thomas. Future research on graphene quantum dots. In: N Manjubaashini, TD Thangadurai, D Nataraj and S Thomas (Eds.). Graphene quantum dots: The emerging luminescent nanolights. Springer, New York, 2024, p. 275-279.

88. A Buzid and JHT Luong. Electrochemical sensing and biosensing-based on carbon nanodots. In: UP Azad and P Chandra (Eds.). Handbook of nanobioelectrochemistry: Application in devices and biomolecular sensing. Springer, New York, 2023, p. 339-362.

89. M Nehra, N Dilbaghi, AA Hassan and S Kumar. Carbon-based nanomaterials for the development of sensitive nanosensor platforms. In: A Deep and S Kumar (Eds.). Advances in nanosensors for biological and environmental analysis. Elsevier, Amsterdam, The Netherlands, 2019, p. 1-25.

90. A Kaur, K Pandey, R Kaur, N Vashishat and M Kaur. Nanocomposites of carbon quantum dots and graphene quantum dots: Environmental applications as sensors. Chemosensors 2022; 10(9), 367.

91. X Zhang, WW Zhu, LH Mei, S Zhang, J Liu and F Wang. Machine learning-enhanced bacteria detection using a fluorescent sensor array with functionalized graphene quantum dots. ACS Applied Materials & Interfaces 2025; 17(2), 3084-3096.

92. PP Khobrekar, GA Zalmi, AP Raiturker, RW Jadhav, A Ganguly, A D’Costa, ST Bugde and SV Bhosale. Citric acid functionalized neomycin carbon dots for cytotoxicity and sensing application. Journal of Molecular Structure 2025; 1323, 140769.

93. S Mishra, RN Bharagava, N More, A Yadav, S Zainith, S Mani and P Chowdhary. Heavy metal contamination: An alarming threat to environment and human health. In: RC Sobti, NK Arora and R Kothari (Eds.). Environmental biotechnology: For sustainable future. Springer, Singapore, 2019, p. 103-125.

94. D Türkmen, M Bakhshpour, S Akgönüllü, S Aşır and A Denizli. Heavy metal ions removal from wastewater using cryogels: A review. Frontiers in Sustainability 2022; 3, 765592.

95. SK Raj, V Yadav, GR Bhadu, R Patidar, M Kumar and V Kulshrestha. Synthesis of highly fluorescent and water soluble graphene quantum dots for detection of heavy metal ions in aqueous media. Environmental Science and Pollution Research 2021; 28, 46336-46342.

96. NAA Anas, YW Fen, NA Yusof, NAS Omar, NS Ramdzan and WMEMM Daniyal. Investigating the properties of cetyltrimethylammonium bromide/hydroxylated graphene quantum dots thin film for potential optical detection of heavy metal ions. Materials 2020; 13(11), 2591.

97. EGL Oliveira, HP de Oliveira and ASL Gomes. Metal nanoparticles/carbon dots nanocomposites for SERS devices: Trends and perspectives. SN Applied Sciences 2020; 2(9), 1491.

98. XX Han, RS Rodriguez, CL Haynes, Y Ozaki and B Zhao. Surface-enhanced Raman spectroscopy. Nature Reviews Methods Primers 2021; 1, 87.

99. R Zheng, H Lin, L Sun, Y Ying, B He and Y Liu. Constructing nitrogen-doped graphene quantum dots embedded in CNT supported layered (Ni_0.5Co_0.5)₃V₂O₈ self-supporting film for high-performance supercapacitor. Journal of Colloid and Interface Science 2025; 677, 49-58.

100. L Xiaoshan, L Ruiyi, L Zaijun, Y Yongqiang and L Xiaohao. Construction of advanced Nb₉VO₂₅ electrode material by introducing graphene quantum dot for high energy supercapacitors with exceptionally high diffusive capacitance. Journal of Industrial and Engineering Chemistry 2025; 141, 269-284.

101. I Zare, SZ Nasab, A Rahi, A Ghaee, M Koohkhezri, MR Farani, HM Gholipour, AH Atabaki, MR Hamblin, E Mostafavi and H Kang. Antimicrobial carbon materials-based quantum dots: From synthesis strategies to antibacterial properties for diagnostic and therapeutic applications in wound healing. Coordination Chemistry Reviews 2025; 522, 216211.

102. Y Qian, J Wang, X Geng, B Jia, L Wang, YQ Li, B Geng and W Huang. Graphene quantum dots nanoantibiotic‐sensitized TiO_2−x heterojunctions for sonodynamic‐nanocatalytic therapy of multidrug‐resistant bacterial infections. Advanced Healthcare Materials 2024; 13(22), 2400659.

103. DZ Zmejkoski, ZM Marković, DD Mitić, NM Zdravković, NO Kozyrovska, N Bugárová and BMT Marković. Antibacterial composite hydrogels of graphene quantum dots and bacterial cellulose accelerate wound healing. Journal of Biomedical Materials Research Part B: Applied Biomaterials 2022; 110(8), 1796-1805.

104. F Norouzi, M Pourmadadi, F Yazdian, K Khoshmaram, J Mohammadnejad, MH Sanati, F Chogan, A Rahdar and F Baino. PVA-based nanofibers containing chitosan modified with graphene oxide and carbon quantum dot-doped TiO₂ enhance wound healing in a rat model. Journal of Functional Biomaterials 2022; 13(4), 300.

105. B Bajorowicz, M Wilamowska-Zawłocka, W Lisowski, A Żak and T Klimczuk. N-doped graphene quantum dot-decorated MOF-derived yolk-shell ZnO/NiO hybrids to boost lithium and sodium ion battery performance. Applied Surface Science 2024; 655, 159702.

106. H Hassan, M Shoaib, MA Ghanem and M Osman. Graphene quantum dots decorated on chromium oxide and zirconium metal-organic framework composite (GQDs@Zr-MOF/Cr₂O₃) for asymmetric supercapacitors and hydrogen production. Materials Chemistry and Physics 2025; 332, 130225.

107. X Liang and G Ji. Metal organic framework (MOF)-anchored polymeric nanocomposite foams for electromagnetic interference shielding. In: S Thomas, C Paoloni and AR Pai (Eds.). Porous nanocomposites for electromagnetic interference shielding. Elsevier, Amsterdam, The Netherlands, 2024. p. 337-362.

108. W Lv, Y Song, H Pei and Z Mo. Synthesis strategies and applications of metal-organic framework-quantum dot (MOF@QDs) functional composites. Journal of Industrial and Engineering Chemistry 2023; 128, 17-54.

109. Q Jia, Z Li, C Guo, X Huang, Y Song, N Zhou, M Wang, Z Zhang, L He and M Du. A γ-cyclodextrin-based metal-organic framework embedded with graphene quantum dots and modified with PEGMA via SI-ATRP for anticancer drug delivery and therapy. Nanoscale 2019; 11(43), 20956-20967.

110. D Wei, W Tang, Y Gan and X Xu. Graphene quantum dot-sensitized Zn-MOFs for efficient visible-light-driven carbon dioxide reduction. Catalysis Science & Technology 2020; 10(16), 5666-5676.