Effect Of Graphene Quantum Dots Research Articles

Effect of Graphene Quantum Dots (GQDs) on the mechanical, dynamic, and durability properties of concrete

Addressing ecological concerns stemming from concrete usage is paramount, prompting exploration into additives for mitigation. Graphene quantum dots (GQDs) have been recognized for their potential to improve the mechanical attributes of cement composites. Additionally, the electrochemical reduction of a saturated solution of carbon dioxide (CO2) and monoethanolamine (CO2-MEA) effectively removes CO2 from the atmosphere. This study delves into the influence of GQDs on the mechanical and durability aspects of concrete. It is noted that the control mix of concrete without GQDs was specifically designed for concrete railway sleepers. Varied proportions of GQDs, ranging from 0.3 % to 1.2 % at 0.3 % increments, were incorporated to assess their impact on fresh and hardened concrete properties. Mechanical properties such as compressive strength, splitting tensile strength, flexural strength, and dynamic properties were evaluated. Durability assessments encompassing water absorption and chloride ion penetration were conducted. Microstructural analysis via Field Emission Scanning Electron Microscopy (FESEM) imaging and Energy-dispersive X-ray spectroscopy (EDS) elucidated the concrete's internal composition. Notably, an optimal GQDs percentage of 0.3 % was observed, signifying its efficacy in enhancing the performance of concrete. When 0.3 % of GQDs was added to concrete, compressive strength, split tensile strength, and flexural strength were enhanced by 10.8 %, 23 %, and 11 % respectively. The incorporation of GQDs resulted in a notable improvement in the fundamental frequencies and dynamic modulus of elasticity. Concurrently, a decrease in the damping ratio was observed for specimens containing GQDs. Additionally, the porosity and chloride penetration depth were lower by 6 % and 30 % for specimens with 0.3 % GQDs. The improvement in workability, mechanical, and dynamic properties of concrete, along with reducing CO2 from the atmosphere, makes GQDs an ideal eco-friendly material. This study is the first to open new pathways for the development of construction materials that are not only structurally superior but also environmentally responsible, marking a significant step forward in the field of civil engineering materials, especially in railway applications.

Graphene Quantum Dots Reduce Hypertrophic Scar by Inducing Myofibroblasts To Be a Quiescent State.

Contrary to the initial belief that myofibroblasts are terminally differentiated cells, myofibroblasts have now been widely recognized as an activation state that is reversible. Therefore, strategies targeting myofibroblast to be a quiescent state may be an effective way for antihypertrophic scar therapy. Graphene quantum dots (GQDs), a novel zero-dimensional and carbon-based nanomaterial, have recently garnered significant interest in nanobiomedicine, owing to their excellent biocompatibility, tunable photoluminescence, and superior physiological stability. Although multiple nanoparticles have been used to alleviate hypertrophic scars, a GQD-based therapy has not been reported. Our in vivo studies showed that GQDs exhibited significant antiscar efficacy, with scar appearance improvement, collagen reduction and rearrangement, and inhibition of myofibroblast overproliferation. Further in vitro experiments revealed that GQDs inhibited α-SMA expression, collagen synthesis, and cell proliferation and migration, inducing myofibroblasts to become quiescent fibroblasts. Mechanistic studies have demonstrated that the effect of GQDs on myofibroblast proliferation blocked cell cycle progression by disrupting the cyclin-CDK-E2F axis. This study suggests that GQDs, which promote myofibroblast-to-fibroblast transition, could be a novel antiscar nanomedicine for the treatment of hypertrophic scars and other types of pathological fibrosis.

Carbons confined silver nanoclusters decorated carbon fiber electrodes toward electrochemical sensor of dihydroxyphenol and heavy metal ions

The development of electrochemical sensors based on noble metals has presented remarkable opportunities and challenges for the detection of trace phenols and heavy metal ions. However, the high costs of precious metals hinder the practical implementation of electrode materials. Enhancing the utilization efficiency of precious metals on the electrode surface is a crucial step toward improving electrochemical sensors based on these valuable materials. In this study, the morphology and utilization rate of silver nanoparticles were regulated by decorating nanofilms with different dimensions on carbon fiber electrodes. Specifically, the polypyrrole-derived carbon film coating enabled the material to have a large electroactive area and silver loading capacity. Simultaneously, the limiting effect of graphene quantum dots formed silver nanoparticles into silver clusters and achieved excellent electrochemical detection performance for dihydroxyphenol and heavy metal ions. Compared with silver nanoparticles, silver clusters provide higher electrocatalytic power and atomic utilization of silver. This study provides technical support for the trace analysis of environmental pollutants.

Halogen doped graphene quantum dots modulate TDP-43 phase separation and aggregation in the nucleus

TDP-43 is implicated in the dynamic formation of nuclear bodies and stress granules through phase separation. In diseased states, it can further condense into pathological aggregates in the nucleus and cytoplasm, contributing to the onset of amyotrophic lateral sclerosis. In this study, we evaluate the effect of graphene quantum dots (GQDs) with different functional groups on TDP-43’s phase separation and aggregation in various cellular locations. We find that halogen atom-doped GQDs (GQDs-Cl, Cl-GQDs-OH) penetrate the nuclear envelope, inhibiting the assembly of TDP-43 nuclear bodies and stress granules under oxidative stress or hyperosmotic environments, and reduce amyloid aggregates and disease-associated phosphorylation of TDP-43. Mechanistic analysis reveals GQDs-Cl and Cl-GQDs-OH modulate TDP-43 phase separation through hydrophobic and electrostatic interactions. Our findings highlight the potential of GQDs-Cl and Cl-GQDs-OH in modulating nuclear protein condensation and pathological aggregation, offering direction for the innovative design of GQDs to modulate protein phase separation and aggregation.

Mechanical behavior of graphene quantum dot epoxy nanocomposites: A molecular dynamics study

Quantum dot fillers were reported to enhance stiffness, yield strength, and toughness of polymers. However, the underlying mechanisms for these enhancements are unclear. In this study, for the first time, molecular dynamics simulations were performed to reveal the effects of graphene quantum dots (GQDs) on epoxy properties. Mechanical simulations revealed that addition of a single-layer graphene quantum dot with six reactive amine groups enhanced the epoxy yield strength by 17% and stiffness by 6%; whereas pristine GQDs reduced the strength by 6% and stiffness by 10%. The results show the importance of surface chemistry of GQDs towards the intelligent design of strong, tough, and multifunctional nanocomposites.

Fe–Mn nanocomposites doped graphene quantum dots alleviate salt stress of Triticum aestivum through osmolyte accumulation and antioxidant defense

An investigation was carried out to evaluate the effect of graphene quantum dots (GQD) and its nanocomposites on germination, growth, biochemical, histological, and major ROS detoxifying antioxidant enzyme activities involved in salinity stress tolerance of wheat. Seedlings were grown on nutrient-free sand and treatment solutions were applied through solid matrix priming and by foliar spray. Control seedlings under salinity stress exhibited a reduction in photosynthetic pigment, sugar content, growth, increased electrolyte leakage, and lipid peroxidation, whereas iron-manganese nanocomposites doped GQD (FM_GQD) treated seedlings were well adapted and performed better compared to control. Enzymatic antioxidants like catalase, peroxidase, glutathione reductase and NADPH oxidase were noted to increase by 40.5, 103.2, 130.19, and 141.23% respectively by application of FM_GQD. Histological evidence confirmed a lower extent of lipid peroxidation and safeguarding the plasma membrane integrity through osmolyte accumulation and redox homeostasis. All of these interactive phenomena lead to an increment in wheat seedling growth by 28.06% through FM_GQD application. These findings highlight that micronutrient like iron, manganese doped GQD can be a promising nano-fertilizer for plant growth and this article will serve as a reference as it is the very first report regarding the ameliorative role of GQD in salt stress mitigation.

An experimental and theoretical correlation to account for the effect of graphene quantum dots on the ionic conductivity of poly(ethylene oxide) polymer electrolytes

An experimental and theoretical correlation to account for the effect of graphene quantum dots on the ionic conductivity of poly(ethylene oxide) polymer electrolytes

Superior macro-scale tribological performance of steel contacts based on graphene quantum dots in aqueous glycerol

Reducing friction is one of the best ways to lower energy consumption and make processes more environmentally friendly. Because of the growing interest in green lubricants, we investigated the synergetic effects of graphene quantum dots (GQDs) combined with aqueous glycerol to improve the lubrication performance of self-mated steel contacts in reciprocating sliding motion. As a comparison, the lubrication performance of some other two-dimensional (2D) graphitic materials (graphite, graphene oxide, and graphene nanoplatelets) was also studied. The results demonstrate that the GQDs-based nano-lubricant reduces the running-in period and provides super-low friction at a high contact pressure in the boundary-lubrication regime, with 72% and 53% improvements in anti-friction and anti-wear performance compared with aqueous glycerol. On the other hand, the 2D graphitic materials provide super-low friction in the mixed-lubrication regime due to the dominant polishing effect of the hydroxyl groups. The surface Raman mapping indicates that the 2D graphitic materials were severely damaged by the continuous reciprocating motion owing to their inferior crack resistance. In contrast, the superior deformation resistance of the GQDs helps to develop a tough tribofilm. This lubrication mechanism suggests that internal shearing of graphene layers inside the GQDs significantly reduces the wear and friction during the running-in period, while the in-situ formation of strongly adhered tough tribofilm with more surface coverage contributed to the realization of super-low friction under a high contact pressure. This study demonstrated that GQDs-based green nano-lubricants could provide super-low friction at a high contact pressure in the boundary-lubrication regime, which was so far characteristic mainly for conventional environment-polluting lubricants.

Graphene quantum dots induce cascadic apoptosis via interaction with proteins associated with anti-oxidation after endocytosis by Trypanosoma brucei.

Trypanosoma brucei, the pathogen causing African sleeping sickness (trypanosomiasis) in humans, causes debilitating diseases in many regions of the world, but mainly in African countries with tropical and subtropical climates. Enormous efforts have been devoted to controlling trypanosomiasis, including expanding vector control programs, searching for novel anti-trypanosomial agents, and developing vaccines, but with limited success. In this study, we systematically investigated the effect of graphene quantum dots (GQDs) on trypanosomal parasites and their underlying mechanisms. Ultrasmall-sized GQDs can be efficiently endocytosed by T. brucei and with no toxicity to mammalian-derived cells, triggering a cascade of apoptotic reactions, including mitochondrial disorder, intracellular reactive oxygen species (ROS) elevation, Ca2+ accumulation, DNA fragmentation, adenosine triphosphate (ATP) synthesis impairment, and cell cycle arrest. All of these were caused by the direct interaction between GQDs and the proteins associated with cell apoptosis and anti-oxidation responses, such as trypanothione reductase (TryR), a key protein in anti-oxidation. GQDs specifically inhibited the enzymatic activity of TryR, leading to a reduction in the antioxidant capacity and, ultimately, parasite apoptotic death. These data, for the first time, provide a basis for the exploration of GQDs in the development of anti-trypanosomials.

Effects of graphene quantum dots on microstructure, optical and gas sensing properties of coral-like ZnCo2O4 nanoparticles

In this study, the composed nanocrystalline ZnCo2O4 and graphene quantum dots (GQDs) were prepared using the facile hydrothermal method. Various microstructure characteristics were specified using X-ray diffraction analysis approaches, including Williamson-Hall and Williamson-Smallman methods. The analysis of scanning electron microscopy, Brunauer-Emmett-Teller, and atomic force microscope were used to morphological characteristics and the pore size distributions of samples. Besides, the optical band gap was decreased by the addition of graphene quantum dots to the ZnCo2O4 nanostructure. The greater crystallite size (45.0 nm) was accompanied by the smaller band gap (3.60 eV). The gas sensing investigations exposed that the coral-like ZnCo2O4/GQD composite nanostructures gas sensor exhibited high response (6.97–100 ppm), selectivity, and low detection limit (0.43 ppm) towards triethylamine. Moreover, enhanced gas sensing properties of coral-like ZnCo2O4/GQD composite nanostructures were observed when compared with coral-like ZnCo2O4 nanostructures. These results can be attributed to their higher pore volume and diameter than nanocrystalline ZnCo2O4.

Folic acid-functionalized graphene quantum dots: Synthesis, characterization, radiolabeling with radium-223 and antiviral effect against Zika virus infection

The use of graphene quantum dots as biomedical devices and drug delivery systems has been increasing. The nano-platform of pure carbon has shown unique properties and is approved to be safe for human use. In this study, we successfully produced and characterized folic acid-functionalized graphene quantum dots (GQD-FA) to evaluate their antiviral activity against Zika virus (ZIKV) infection in vitro, and for radiolabeling with the alpha-particle emitting radionuclide radium-223. The in vitro results exhibited the low cytotoxicity of the nanoprobe GQD-FA in Vero E6 cells and the antiviral effect against replication of the ZIKV infection. In addition, our findings demonstrated that functionalization with folic acid doesn’t improve the antiviral effect of graphene quantum dots against ZIVK replication in vitro. On the other hand, the radiolabeled nanoprobe 223Ra@GQD-FA was also produced as confirmed by the Energy Dispersive X-Ray Spectroscopy analysis. 223Ra@GQD-FA might expand the application of alpha targeted therapy using radium-223 in folate receptor-overexpressing tumors.

Sonochemical synthesized BaMoO4/ZnO nanocomposites as electrode materials: A comparative study on GO and GQD employed in hydrogen storage

Due to poor rate proficiency and electrochemical capacity of transition metal oxides, production electrode materials as operative way to develop the electrochemical performance is a crucial strategy to make sure the great electroactive sites and fast electron/ion diffusion route. In order to solve this problem, carbon-based nanocomposites as conductive substrates are applied. The nanostructured BaMoO4/ZnO was produced by sonochemical method in the presence of tween 20 as stabilizing agent. Effect of graphene quantum dots (GQDs) and graphene oxide (GO) for developing hydrogen capacity of BaMoO4/ZnO was studied by providing representative composites of BaMoO4/ZnO-GQDs and BaMoO4/ZnO-GO. For this purpose, GQDs was synthesized using green source of Spiraea crenata and the GO provided by commercial company. The structural analysis shows preparation of scales-like morphology of BaMoO4/ZnO without any impurities through SEM, TEM, XRD, EDS and FT-IR characterization data. Also, the specific surface area for BaMoO4/ZnO-GQDs (11 m2/g) and BaMoO4/ZnO-GO (124 m2/g) nanocomposites increased by comparing to BaMoO4/ZnO (9.1 m2/g). The resultant nanocomposites used as new active compounds for applying in hydrogen storage strategies using cyclic voltammetry and chronopotentiometry tests. Comprehensively, the hydrogen capacitance after 15 cycles was demonstrated on the nanostructured BaMoO4/ZnO about 129 mAhg−1. It demanded the maximum capacitance for BaMoO4/ZnO-GQDs and BaMoO4/ZnO-GO nanocomposites were 284 and 213 mAhg−1 respectively, which was higher than the initial nanostructured BaMoO4/ZnO. It was exposed from the carbon based structured that; the endorsed electrochemical hydrogen storage (EHS) performance is ascribed to the reaction of the redox pair of Mo6+ /Mo5+ at the active sites throughout the EHS procedure. This study delivers a novel plan and potential sorption electrode materials to progress the intrinsic action of conductive compounds.

Enhanced Photodynamic Therapy Effects of Graphene Quantum Dots Conjugated with Aminoporphyrins

Porphyrins are promising materials for photodynamic therapy, but their low solubility and aggregation in biological environments are still obstacles to surpass. In order to overcome these limitations, the conjugation of porphyrins with graphene quantum dots (GQDs), here functioning as a vehicle to improve the internalization of porphyrins by cancer cells, was considered. The GQDs were conjugated with an aminoporphyrin via amide linkage using both thionyl chloride (SOCl2) and 1-ethyl-3-(3′-dimethylaminopropyl)carbodiimide coupling methodologies. Based on structural characterization (Fourier transform infrared and X-ray photoelectron spectroscopy), the best porphyrin loading was observed with the SOCl2 procedure. The new hybrids were investigated as phototherapeutic agents in high incidence breast cancer (T-47D cell line) under white light, and a significant photocytotoxic effect was observed at 10 nM. The conjugation of GQDs to the aminoporphyrin promoted an efficient uptake by the T-47D cells when compared with the nonimmobilized porphyrin. These results point out the high potential of the new hybrids to be explored as theragnostic agents.

Effects of different pyrolysis preparation condition on the fluorescence properties of graphene quantum dots

Due to the quantum confinement effect of graphene quantum dots (GQDs), the fluorescence properties of the GQDs can be adjusted by changing the size of the GQDs. We can obtain better fluorescence properties of the GQDs by varying the preparation conditions. GQDs were prepared by the pyrolysis method. To obtain GQDs with excellent fluorescence properties, the effect of different pyrolysis times and pH values on the properties of GQDs were studied. Fourier infrared spectroscopy, x-ray diffraction, transmission electron microscope, and fluorescence spectroscopy (PL) were used to characterize the morphology, structure, and fluorescence properties of GQDs. The experimental results show that with the increase of pyrolysis time, the carbonization of citric acid intensifies, the size of GQDs increases, the fluorescence peak of GQDs broadens, and the dependence of fluorescence emission increased gradually. Fluorescence property changes with the pyrolysis time, the fluorescence property is optimal with the pyrolysis time of 30 min, and the suitable pyrolysis time will cause the citric acid sufficient reaction to produce the maximum yield of GQDs. Besides, GQDs fluorescence properties are also affected by the acid-base environment. The fluorescence of GQDs solution has the strongest in an alkaline environment and quenched in an acidic environment.

Synergistic effects of graphene quantum dots and carbodiimide in promoting resin–dentin bond durability

ObjectiveResin-based dental adhesion is mostly utilized in minimally invasive operative dentistry. However, improving the durability and stability of resin–dentin bond interfaces remain a challenge. Graphene quantum dots (GQDs) reinforced by 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC) were introduced to modify the resin–dentin bond interfaces, thereby promoting their durability and stability. MethodsGQDs, EDC, and EDC+GQDs groups were designed to evaluate the effects of GQDs and EDC on collagenase activity, the interaction of GQDs with collagen, and the resin–dentin interface. First, the effects of GQDs and EDC on collagenase activity was evaluated by Collagenase (EC 3.4.24.3) reacting with its substrate. The interaction of GQDs and EDC with collagen were evaluated by cross-linking degree analysis, sodium dodecyl sulfate–polyacrylamide gel electrophoresis, attenuated total reflection Fourier transform infrared spectroscopy and enzymatic hydrolysis. Second, the acid-etched and rinse adhesive system was used to evaluate the resin–dentin bond on the basis of microtensile bond strength, in situ zymography and fluorescence confocal laser scanning microscopy. ResultsGQDs could inhibit collagenase activity. GQDs with the aid of EDC could cross-link collagen via covalent bonds and improve the anti-enzymatic hydrolysis of collagen. In the resin–dentin adhesion model, the μTBS of the EDC+GQDs group was significantly higher than the other control groups after thermocycling. The addition of EDC to GQDs could inhibit matrix metalloproteinase activity and promote the integrity of the bonding interfaces after thermocycling. SignificanceThis study presents a novel strategy to modify the resin–dentin interface and provides a new application for GQDs. This strategy has the potential to improve the durability of resin-based restoration in dentistry.

Interfacial enhancement effect of graphene quantum dots on PEDOT:PSS/single-walled carbon nanotubes thermoelectric materials

In the present study, Poly(3,4-ethylenedioxythiophene):poly(styrene sulfonic acid) (PEDOT:PSS), with the incorporation of graphene quantum dot (GQD)-coated single-walled carbon nanotubes (SWCNTs), has been used in the preparation of PEDOT:PSS/SWCNTs/GQDs thermoelectric films (PSG). The effect of SWCNTs/GQDs (as a nanofiller) on the microstructure and thermoelectric properties of the composite films has been especially investigated. It was observed that the addition of GQDs will induce a phase separation between PEDOT and PSS. Furthermore, the enhanced interfacial bonding induced a microstructure ordering and an accelerated transport of carriers. The in-plane electrical conductivity and Seebeck coefficient of the obtained film reached 1036 S•cm−1 and 13.8 μV•K−1, respectively, for 1 wt% of SWCNTs/GQDs. These results gave a high power factor (PF) of up to 19.9 µW•m−1•K−2, which is about six times as high as for pristine PEDOT:PSS and also higher than that of PEDOT:PSS/SWCNTs. The obtained maximum ZT reaches 3.22 × 10−3 with high PF value and low in-plane thermal conductivity. The present research provided a new strategy for developing high performance organic thermoelectric materials.

Fluorescent epoxy-graphene quantum dots nanocomposites: synthesis and study of properties

ABSTRACT This study aims to investigate the reinforcing effects of graphene quantum dots on various properties of epoxy resins. To do this, graphene quantum dots were synthesized, then, characterized by various spectroscopic methods. These nanoparticles including several weight percentages along with a curing agent were added to epoxy resin. Finally, fluorescent epoxy graphene quantum dots nanocomposites were prepared. FTIR, photoluminescence, UV-visible absorption, FESEM, TGA, tensile testing and DMTA analysis were used to characterize the resultant nanocomposites. Findings evinced that adding graphene quantum dots to the epoxy resin led to an improvement of thermal stability, mechanical features, and viscoelastic properties of nanocomposites.

Size Effect of Graphene Quantum Dots on Photoluminescence.

High-photoluminescence (PL) graphene quantum dots (GQDs) were synthesized by a simple one-pot hydrothermal process, then separated by dialysis bags of different molecular weights. Four separated GQDs of varying sizes were obtained and displayed different PL intensities. With the decreasing size of separated GQDs, the intensity of the emission peak becomes much stronger. Finally, the GQDs of the smallest size revealed the most energetic PL intensity in four separated GQDs. The PL energy of all the separated GQDs shifted slightly, supported by density functional theory calculations.

Hyaluronic acid-graphene quantum dot nanocomposite: Potential target drug delivery and cancer cell imaging.

Nowadays, the use of nanoparticle-based drug delivery systems has received much more attention. In this regard, here, graphene quantum dots (GQD) were used as drug carriers as well as imaging agents for cancer cells. In order to optimize the dose of the drug and reduce its side effects for healthy cells, hyaluronic acid was decorated on the surface of GQD to target cancer cells. The morphology and size of the synthesized nanoparticles alone and conjugated with hyaluronic acid were investigated using scanning electron microscopy (SEM) and transmission electron microscopy (TEM); TEM images revealed a particles size of ∼5.67 and ∼8.69 nm, respectively. In the presence of 1-ethyl-3-[3(dimethylamino)propyl]carbodiimide hydrochloride/N-hydroxysuccinimide (EDC/NHS), hyaluronic acid was bounded to dopamine hydrochloride and was prepared to react with GQD. After synthesis of graphene quantum dot-hyaluronic acid nanocomposite, curcumin (CUR) as a drug model was loaded on the synthesized nanocarriers, and its loading percentage was measured. The results showed that 98.02% of the drug was loaded on the nanocarriers. Also, the conjugation of each agent on the nanocarrier was approved by photoluminescence spectroscopy, Fourier transform infrared spectroscopy (FTIR), and UV-visible absorption techniques, and the results showed that the reactions were performed correctly. The effect of GQD, graphene quantum dot-hyaluronic acid, CUR, graphene quantum dot-hyaluronic acid-CUR on the viability of HeLa and L929 cells was evaluated by the MTT test. The results showed that the synthesized nanocarrier is completely biocompatible, and the drug nanocarriers reduce HeLa cell viability significantly due to the mediation of hyaluronic acid-CD44 for drug cell uptake. Simultaneously with drug delivery, the other goal of these nanocarriers is to image cancer cells by emitting fluorescent light. Fluorescent microscopy showed that these nanocarriers were adsorbed on HeLa cells, unlike L929 cells.

The effect of graphene quantum dots/ ZnS co‐passivation on enhancing the photovoltaic performance of CdS quantum dot sensitized solar cells

The effect of graphene quantum dots (GQDs) as a passivating layer for cadmium sulfide (CdS) quantum dot-sensitized solar cell (QDSSC) has been investigated. GQDs were prepared by the liquid exfoliation method. The optical properties of GQDs were studied by UV-Vis and photoluminescence spectroscopies. The morphology of GQDs was studied by transmission emission morphology (TEM) analysis. Further, the photoexcitation behavior of GQDs has been studied in detail using emission spectroscopy and its effect on the photovoltaic performance of CdS QDSSC has been explored using J-V analysis. The efficacy of GQDs as passivation layer over the CdS loaded titanium dioxide (TiO2) photoanode in QDSSC is high and thereby improved the open-circuit voltage (Voc) (555 mV) compared to zinc sulfide (ZnS) passivated QDSSC (509 mV). As a result, the photoconversion efficiency (PCE) of GQD-passivated QDSSC is relatively enhanced up to 25% higher than that of ZnS-passivated QDSSC under similar conditions. A high PCE of 4.26% has been achieved for GQD/ZnS co-passivated QDSSC, which is 31% higher than ZnS-passivated QDSSC. Besides, the impedance analysis revealed low internal resistance and high charge recombination resistance in the GQD-passivated QDSSC when compared to other cells. The presence of GQD layer suppressed the recombination with high electron transport and thereby improved the PCE of QDSSC. The present study shows the possibility of using GQDs as an interfacial passivation layer between the sensitizer and electrolytes for enhancing the photovoltaic performance of CdS-based QDSSCs.