CuS Quantum Dots Research Articles

Bright Blue-Light emitting cobalt doped CuS quantum dots: Photophysical studies and selective sensing application of ferric ion

Surface-functionalized quantum dots (QDs) have garnered significant attention in recent years for a variety of applications, including LEDs, photovoltaics, sensing, bioimaging and biomedical domains due to their distinct optical features such as strong photoluminescence behavior, high quantum yields etc. However, formation of nontoxic QDs is very challenging for the researchers because of their lower optical properties as compared to Cd based QDs. The phenomenon of doping in semiconductor QDs is an effective way to achieve high opto-electrical properties in the host QDs. We have presented a low temperature colloidal synthesis of CuS QDs using cobalt (Co2+) as a doping agent with an exceptional stability at room temperature for 30 days. The photoluminescence (PL) properties of Co2+-doped CuS QDs exhibit a deep-blue emission at 420 nm resulting in excellent optical property with an improvement of photoluminescence quantum yield. Due to remarkable CIE chromaticity coordinates, good CCT values, and high colour purity, the synthesized Co2+-doped CuS QDs could be used extensively in LEDs and prove to be useful as blue phosphors. The synthesized Co2+-doped CuS QDs also act as a fluorescence probe in the detection of ferric ion (Fe3+) with high sensitivity, good selectivity, a low limit of detection (LOD) and limit of quantification (LOQ), of (4.99 ± 0.12) μM and (16.67 ± 0.40) μM, respectively.

Novel Synthesis Route of Plasmonic CuS Quantum Dots as Efficient Co-Catalysts to TiO2/Ti for Light-Assisted Water Splitting.

Self-doped CuS nanoparticles (NPs) were successfully synthesized via microwave-assisted polyol process to act as co-catalysts to TiO2 nanofiber (NF)-based photoanodes to achieve higher photocurrents on visible light-assisted water electrolysis. The strategy adopted to perform the copper cation sulfidation in polyol allowed us to overcome the challenges associated with the copper cation reactivity and particle size control. The impregnation of the CuS NPs on TiO2 NFs synthesized via hydrothermal corrosion of a metallic Ti support resulted in composites with increased visible and near-infrared light absorption compared to the pristine support. This allows an improved overall efficiency of water oxidation (and consequently hydrogen generation at the Pt counter electrode) in passive electrolyte (pH = 7) even at 0 V bias. These low-cost and easy-to-achieve composite materials represent a promising alternative to those involving highly toxic co-catalysts.

Green synthesis of Bio-CuS quantum dots by sulfate reducing bacteria for solid-phase photocatalytic degradation of polyethylene film

In this study, CuS quantum dots (QDs) synthesized through biological method were used as photocatalysts for the photocatalytic degradation of polyethylene (PE) plastics. Bio-CuS QDs were synthesized through a green process using sulfate reducing bacteria, while Che-CuS QDs were prepared by chemical precipitation for comparison. The crystal structure, surface morphology, microstructure and optical properties of the samples were detected by XRD, SEM, TEM and UV–Vis DRS. The green synthesis mechanism of Bio-CuS was inferred by analyzing changes in amino acid concentration and the three-dimensional fluorescence spectra of extracellular polymeric substances before and after synthesis. The photocatalytic degradation of PE films by Che-CuS and Bio-CuS was investigated. The weight loss rates of PE+Che-CuS and PE+Bio-CuS were 9.1 % and 12.8 % after 14 d irradiation, respectively, while pure PE was only 1.7 %. Furthermore, SEM, UV–Vis DRS, contact angle, TGA, GPC and FTIR were adopted to characterize the PE film. The results revealed that PE+Che-CuS and PE+Bio-CuS underwent major changes in morphology, transparency, hydrophilicity, thermal stability, molecular weight and functional groups compared with PE, with more pronounced changes observed for PE+Bio-CuS. The quenching experiments of active species showed that h+ and·OH were critical to the PE degradation. The intermediate products of PE degradation were analyzed by GC–MS, and a possible degradation pathway was proposed. In addition, the possible mechanism of photocatalytic degradation of PE films by CuS QDs was proposed. This work provides a green remediation approach to addressing the growing plastic pollution in the environment.

Study of anti-corrosion epoxy resin coatings with high corrosion resistance and mechanical performance based on quantum dots

The corrosion of steel construction in marine environments faces severe corrosion threats, and coatings based on nanofillers are an effective strategy for steel corrosion protection. However, the related studies of the anti-corrosion coatings based on quantum dots are still poor. In this work, CuS and ZnS quantum dots (QD) were initially synthesized, and epoxy resin (EP) coatings containing QD with ratios of 0.05 wt%, 0.1 wt%, 0.2 wt%, and 0.5 wt% were successfully prepared subsequently. Surface analysis, electrochemical measurements, salt spray tests, and mechanical tensile tests were performed to characterize the prepared quantum dots and study the anti-corrosion behavior and mechanism of the prepared coatings. Results indicated that the prepared CuS and ZnS quantum dots have small sizes with values of 13.8 and 8.9 nm, respectively. Compared to the pure EP coating, QD-EP coatings have a higher mechanical strength and toughness which is conducive to improving the coatings’ corrosion resistance and service life. The impedance values of all the QD-EP coatings increase by more than three orders of magnitude in contrast to pure EP coating after 60 d of testing. Furthermore, the prepared QD-EP coatings possess a long-term anti-corrosion property.

Synthesis of TiO2 nanotubes from ilmenite with CuS nanoparticles as efficient visible-light photocatalyst.

Titanium dioxide nanotube (TNT) is one of the most widely used photocatalysts. In this research, TNT was prepared by a facile method using ilmenite (FeTiO3) concentrate as the titanium source. For this purpose, iron was leached out from ilmenite using HCl in assistance with the iron powder as the reducing agent to produce pure TiO2, where consequently, TNT was produced through hydrothermal treatment of the prepared TiO2 in an alkaline solution. CuS quantum dots, using the L-cysteine as a linker, were coated on the TNT to improve TNTs' photocatalytic properties. Characterization was done using XRD, SEM, FESEM, HRTEM, FT-IR, nitrogen sorption, and band gap measurement. The results revealed the formation of TNT with a star-shaped macrostructure as well as, a good dispersion of uniform CuS quantum dots with an average diameter of a few nanometers on the TiO2 structure. A dye adsorption kinetics study of the TNT and CuS-dopped TNT showed that TNT carries a higher adsorption capacity compared to the CuS-dopped TNT, developed due to its higher surface area and pore volume. Next, the photocatalytic performance (under visible light) of the prepared composite was studied over the methylene blue (MB) and malachite green (MG) dyes, after the determination of the dye adsorption equilibrium point (where the adsorption stops). TNT showed almost no dye degradation while the prepared composite degraded almost 95 % of the dyes as the result of the reduced band gap from 3.21 to 2.67 eV. In this study, for the first time, the TNT was prepared using a mineral source and ilmenite, enhanced in photocatalytic properties, and presented a successful application.

Implanting CuS Quantum Dots into Carbon Nanorods for Efficient Magnesium-Ion Batteries.

Magnesium-ion batteries (MIBs) are emerging as potential next-generation energy storage systems due to high security and high theoretical energy density. Nevertheless, the development of MIBs is limited by the lack of cathode materials with high specific capacity and cyclic stability. Currently, transition metal sulfides are considered as a promising class of cathode materials for advanced MIBs. Herein, a template-based strategy is proposed to successfully fabricate metal-organic framework-derived in-situ porous carbon nanorod-encapsulated CuS quantum dots (CuS-QD@C nanorods) via a two-step method of sulfurization and cation exchange. CuS quantum dots have abundant electrochemically active sites, which facilitate the contact between the electrode and the electrolyte. In addition, the tight combination of CuS quantum dots and porous carbon nanorods increases the electronic conductivity while accelerating the transport speed of ions and electrons. With these architectural and compositional advantages, when used as a cathode material for MIBs, the CuS-QD@C nanorods exhibit remarkable performance in magnesium storage, including a high reversible capacity of 323.7 mAh g-1 at 100mA g-1 after 100 cycles, excellent long-term cycling stability (98.5 mAh g-1 after 1000 cycles at 1.0 A g-1 ), and satisfying rate performance (111.8mA g-1 at 1.0 A g-1 ).

CuS quantum dots activated DNAzyme for ratiometric electrochemical detection of telomerase activity.

Telomerase activity detection has attracted much attention concerning its importance for early cancer diagnosis. Here, we established a ratiometric electrochemical biosensor for telomerase detection based on CuS quantum dots (CuS QDs) dependent DNAzyme-regulated dual signals. The telomerase substrate probe was used as the linker to combine the DNA fabricated magnetic beads and CuS QDs. In this way, telomerase extended the substrate probe with repeated sequence to from hairpin structure, releasing CuS QDs as an input to DNAzyme modified electrode. DNAzyme was cleaved with high current of ferrocene (Fc) and low current of methylene blue (MB). On the basis of the obtained ratiometric signals, telomerase activity detection was achieved in the range of 1.0×10-12-1.0×10-6 IU/L, with the limit of detection down to 2.75×10-14 IU/L. Moreover, telomerase activity from HeLa extracts was also tested to verify the clinical application.

Structural, Optical and Ionic Properties of PVA Capped CuS Quantum Dots

Copper sulphide quantum dots were synthesized by a simple chemical route using ammonia (aq.) as a complexing agent in PVA matrix. Copper acetate monohydrate and thiourea were used as precursors. The particle sizes as obtained from XRD results were found to be in good agreement with those of HRTEM. The UV-Vis. absorption and PL emission spectra exhibited a systematic blue shift of absorption and emission respectively confirming quantum confinement effect in the synthesized quantum dots. The band gap as estimated from Tauc-plot increased from 3.26eV to 3.92eV with change of concentration of complexing agent. The FTIR spectra exhibited Cu-S stretching peaks characteristic of CuS. Ionic contributions of the electrolytic ionic CuS solution as measured by a standard conductivity cell clearly showed the semiconducting behavior of the product material. The synthesized material may be exploited in fabrication of an optoelectronic device in UV-blue region.

Efficient wastewater disinfection by raised 1O2 yield through enhanced electron transfer and intersystem crossing via photocatalysis of peroxymonosulfate with CuS quantum dots modified MIL-101(Fe)

Peroxymonosulfate (PMS)-based photocatalysis is a promising alternative approach for wastewater disinfection. Singlet oxygen (1O2) is sensitive and efficient for bacterial inactivation. This study developed a 1O2-predominated PMS disinfection technique under visible light with CuS quantum dots (QDs) modified MIL-101(Fe) (CSQDs@MF). CuS QDs modification greatly enhanced the 1O2 quantum yield by 80% than that of MIL-101(Fe). Photoelectricity and photoluminescence tests demonstrated that both the enhanced electron transfer and energy transfer were responsible for improved 1O2 generation in Vis/PMS/CSQDs@MF system. The system took 60 min to inactivate 7.5-log E. coli, and it could be applied in a broad pH and dissolve oxygen range. Bacterial inactivation mechanism suggested that 1O2 attacked cell membrane first, then induced oxidative stress, up-regulated intracellular ROS level, eventually broke DNA strand. The system showed good disinfection performance on Gram-positive B. subtilis and fecal coliforms in practical wastewater, implying it is a promising alternative disinfection technology for wastewater treatment.

Hydrothermal Synthesis of Se-Doped CuS Quantum Dots with Respect to the DW/EN Solvent Ratio and Application as a Counter Electrode for Quantum Dot-Sensitized Solar Cells

Hydrothermal Synthesis of Se-Doped CuS Quantum Dots with Respect to the DW/EN Solvent Ratio and Application as a Counter Electrode for Quantum Dot-Sensitized Solar Cells

A Novel Artificial Neuron-Like Gas Sensor Constructed from CuS Quantum Dots/Bi2S3 Nanosheets

HighlightsAn ultra-sensitive capture of NO2 molecules and fast charge collection and transfer has been realized by constructing the model of artificial neuron-likegas sensing structure based on CuS quantum dots (QDs)/Bi2S3 nanosheets (NSs)realizes.Simulation analysis revealed that CuS QDs and Bi2S3NSs can be used, respectively, as the main adsorption sites and charge transport pathways, thus leading to a greatly enhanced gas capture ability and charge conduction performance of NO2.

Low field magnetic interactions in the transition metals doped CuS quantum dots

Polyvinlypyrrolidone (PVP) capped and magnetic transition metals (TM = Fe, Co and Cr) doped CuS quantum dots (Cu1-xTMxS; x = 0.02 & 0.04) were synthesized by low entropy facile chemical co-precipitation method. The structural, optical and magnetic characterizations of the synthesized QDs were done by using X-ray diffraction (XRD) technique, UV–Vis-NIR absorption spectroscopy, photoluminescence (PL) spectroscopy and superconducting quantum interference device (SQUID) respectively. The low field non-linearity and the presence of coercivity in the M−H loops indicate the presence low field magnetic (spin–spin) interactions between the doped cations.

Enhanced Supercapacitor Performance and Electromagnetic Interference Shielding Effectiveness of CuS Quantum Dots Grown on Reduced Graphene Oxide Sheets.

This study is focused on the preparation of the CuS/RGO nanocomposite via the hydrothermal method using GO and Cu–DTO complex as precursors. X-ray diffraction, Fourier-transform infrared spectroscopy, and Raman and X-ray photoelectron spectroscopy study revealed the formation of the CuS/RGO nanocomposite with improved crystallinity, defective nanostructure, and the presence of the residual functional group in the RGO sheet. The morphological study displayed the transformation of CuS from nanowire to quantum dots with the incorporation of RGO. The galvanostatic charge/discharge curve showed that the CuS/RGO nanocomposite (12 wt % Cu–DTO complex) has tremendous and outperforming specific capacitance of 3058 F g–1 at 1 A g–1 current density with moderate cycling stability (∼60.3% after 1000 cycles at 10 A g–1). The as-prepared nanocomposite revealed excellent improvement in specific capacitance, cycling stability, Warburg impedance, and interfacial charge transfer resistance compared to neat CuS. The fabricated nanocomposites were also investigated for their bulk DC electrical conductivity and EMI shielding ability. It was observed that the CuS/RGO nanocomposite (9 wt % Cu–DTO) exhibited a total electromagnetic shielding efficiency of 64 dB at 2.3 GHz following absorption as a dominant shielding mechanism. Such a performance is ascribed to the presence of interconnected networks and synergistic effects.

Y-type DNA structure stabilized p-type CuS quantum dots to quench photocurrent of ternary heterostructure for sensitive photoelectrochemical detection of miRNA

Herein, a p-n quenching photoelectrochemical (PEC) biosensor is constructed for the ultrasensitive detection of miRNA-21 which the SnO2/CdCO3/CdS ternary composite nanomaterial is used as a signal indicator and the Y-type DNA structure stabilized p-type CuS quantum dot (QD) is employed as a signal quencher. Constructing the cascade energy level structure by using three photosensitive materials, in which stannic oxide (SnO2) is used as the photoactive material and cadmium sulfide (CdS) and cadmium carbonate (CdCO3) are served as the sensitizers. The prepared SnO2/CdCO3/CdS cascade co-sensitization structure with significantly improved photocurrent signal can inhibit the recombination of photogenerated electrons and holes, thereby dramatically enhancing the initial photocurrent response. Amounts of single strands DNA (assistant DNA) are output via the exponential strand displacement amplification (E-SDA) when miRNA-21 is present. The output assistant DNA can stabilize the CuS QD by forming stable Y-type DNA nanostructure on the surface of SnO2/CdCO3/CdS modified electrode. Therefore, the PEC signal of SnO2/CdCO3/CdS ternary composite nanomaterial is greatly quenched, because of the competitive consumption of exciting light energy and electron donors, as well as the steric effect of Y-type DNA structure. The linear range of the biosensor is from 10 fM to 1 μM with the detection limit down to 3.25 fM.

CuS QDs/Co3O4 Polyhedra-Driven Multiple Signal Amplifications Activated h-BN Photoeletrochemical Biosensing Platform.

Herein, we developed an unmodified hexagonal boron nitride (h-BN) photoelectrochemical (PEC) biosensing platform with a low background signal and high sensitivity based on CuS quantum dots (QDs)/Co3O4 polyhedra-driven multiple signal amplifications. The prepared porous h-BN nanosheets with large specific surface areas, as the photoelectric substrate material, can provide extensive active reaction sites. Meanwhile, the CuS QDs/Co3O4 polyhedra were synthesized by the zeolitic imidazolate framework (ZIF-67) and utilized as a multiple signal amplifier, which can not only drive the p-n semiconductor quenching effect to compete with the h-BN photoelectrode for the consumption of electron donors and exciting light but also trigger a mimetic enzymatic catalytic precipitation effect to inhibit electron transfer. The quenching ability and peroxidase-like activity of CuS QDs/Co3O4 polyhedra were evaluated to prove its superiority, and the possible mechanisms of electron transfer and enzymatic catalytic were further analyzed in detail. The developed PEC biosensing platform for the chlorpyrifos assay presented outstanding performance with a wide linear range from 1 × 10-1 to 1 × 107 ng mL-1 and a low detection limit of 0.34 pg mL-1 and exhibited excellent selectivity, reproducibility, and stability. In addition, the CuS QDs/Co3O4 polyhedra-activated h-BN PEC biosensing platform may exhibit universality for various analytes via replacing the corresponding target aptamer sequence. This work provides a remarkable inspiration and valuable reference for the development of the PEC biosensor, and the signal amplifier-enabled unmodified PEC biosensing platform strategy has a bright application in early safety warning, bioanalysis and clinical diagnosis.

Ultrasmall aqueous starch-capped CuS quantum dots with tunable localized surface plasmon resonance and composition for the selective and sensitive detection of mercury(ii) ions.

Ultrasmall starch-capped CuS quantum dots (QDs) with controllable size were chemically fabricated in an aqueous medium. The phase of the CuS QDs was confirmed via X-ray diffraction (XRD), whereas the characteristic localized surface plasmon resonance (LSPR) peak in the near-infrared (NIR) region was measured using UV-Vis spectroscopy. Transmission electron microscopy and high bandgap analysis confirmed the formation of ultrasmall CuS QDs in the size range of 4–8 nm. CuS QDs have been used for the selective and sensitive detection of Hg2+ ions through colorimetric and spectroscopic techniques. The selective sensing of Hg2+ ions from various metal ions was detected via a remarkable change in color, damping in LSPR intensity, significant change in the Fourier-transform infrared spectra and X-ray photoelectron spectroscopic measurements. The mechanism of interaction between the CuS QDs and Hg2+ ions has been deeply explored in terms of the role played by the starch and the reorganization of sulfide and disulfide bonds to facilitate the access of Hg2+ ions into the CuS lattice. Finally, an intermediate Cu2−xHgxS nanostructure resulted in the leaching of Cu+ ions into the solution, which were further recovered and reused for the formation of fluorescent Cu2S nanoparticles. Thus, the entire process of synthesis, sensing and reuse paves the way for sustainable nanotechnology.

The Frontiers of Nanomaterials (SnS, PbS and CuS) for Dye-Sensitized Solar Cell Applications: An Exciting New Infrared Material.

To date, extensive studies have been done on solar cells on how to harness the unpleasant climatic condition for the binary benefits of renewable energy sources and potential energy solutions. Photovoltaic (PV) is considered as, not only as the future of humanity’s source of green energy, but also as a reliable solution to the energy crisis due to its sustainability, abundance, easy fabrication, cost-friendly and environmentally hazard-free nature. PV is grouped into first, second and third-generation cells. Dye-sensitized solar cells (DSSCs), classified as third-generation PV, have gained more ground in recent times. This is linked to their transparency, high efficiency, shape, being cost-friendly and flexibility of colour. However, further improvement of DSSCs by quantum dot sensitized solar cells (QDSSCs) has increased their efficiency through the use of semiconducting materials, such as quantum dots (QDs), as sensitizers. This has paved way for the fabrication of semiconducting QDs to replace the ideal DSSCs with quantum dot sensitized solar cells (QDSSCs). Moreover, there are no absolute photosensitizers that can cover all the infrared spectrum, the infusion of QD metal sulphides with better absorption could serve as a breakthrough. Metal sulphides, such as PbS, SnS and CuS QDs could be used as photosensitizers due to their strong near infrared (NIR) absorption properties. A few great dependable and reproducible routes to synthesize better QD size have attained much ground in the past and of late. The injection of these QD materials, which display (NIR) absorption with localized surface plasmon resonances (SPR), due to self-doped p-type carriers and photocatalytic activity could enhance the performance of the solar cell. This review will be focused on QDs in solar cell applications, the recent advances in the synthesis method, their stability, and long term prospects of QDSSCs efficiency.

Chitosan-mediated green synthesis and folic-acid modification of CuS quantum dots for photoacoustic imaging guided photothermal therapy of tumor

CuS nanomaterials capped with artificial organic-molecules or polymers have been well demonstrated as efficient photothermal nanoagents for the therapy of tumor, but their biocompatibility and target ability should be improved. To address these problems, we have used chitosan (CS) as the biomacromolecule model and surface ligands to prepare CuS quantum dots (QDs) via a simple co-precipitation method. CuS-CS QDs are then conjugated with folic acid (FA). The resulting CuS-CS-FA QDs are composed of hexagonal phase nanodots with sizes of about 4 nm. FA modification process has no apparent influence on the size, phase and composition of the QDs. Furthermore, the zeta potential and infrared spectroscopy confirm the efficient conjugation of FA. CuS-CS-FA QDs exhibit strong near-infrared photoabsorption and high photothermal efficiency (47.0%). As a result of the presence of CS ligand and FA modification, CuS-CS-FA QDs have good biocompatibility and relatively high cellular uptake efficacy. When CuS-CS-FA QD dispersion is injected intravenously into the tumor-bearing mice, the photoacoustic imaging reveals that CuS-CS-FA QD can be efficiently targeted and accumulated in the tumor and reach the peak dose at 60 min. The irradiation of 1064-nm laser (1.0 W cm−2, 10 min) results in the efficient inhibition of tumor growth, without treatment-induced toxicity. Therefore, CuS-CS-FA QDs have great potential to become biocompatible multifunctional nanoagents for imaging guided therapy of tumor.

Optimizing the Multiwall Carbon Nanotubes Counter Electrode by Depositing CuS Quantum Dots

For the purpose of improving the property of a multiwall carbon nanotubes (MWCNTs) counter electrode (CE), CuS quantum dots (QDs) are deposited. Three-dimension network MWCNTs as the framework are deposited onto an fluorine-doped tin oxide (FTO) glass substrate and then CuS QDs as active sites are loaded onto them with a successive ionic layer adsorption and reaction method to form a composite CE. TEM and energy dispersive X-ray (EDX) spectrum can verify the morphology and elemental composition of the composite CE that CuS QDs are loaded onto the MWCNTs CE successfully. The photoelectric properties of quantum dot sensitized solar cells (QDSCs) are analyzed with Nyquist, Tafel, and J–V curves. The results show that the catalytic ability of the CE is enhanced through the loading of CuS QDs according to electrochemical impedance spectroscopy and Tafel analyses. The effect of CuS depositing cycle times on the photoelectric properties of QDSCs is discussed. And the QDSC based on the MWCNTs CE deposited with CuS QDs in ten cycles can display the best performance within all cell samples ( $V_{{\text{oc}}}\,= \,{\text{0.874}}\,{\text{V}}$ , $J_{{\text{sc}}}\,= \,{\text{10.105}}\,{\text{mA cm}}^{- 2}$ , ${\text{FF}}\,= \,{\text{0.416}}$ , and $\eta \,= \,{\text{3.677}}\% $ ). The power conversion efficiency of this cell is almost equivalent to that of Pt CE one under the same conditions and especially its $V_{{\text{oc}}}$ is 0.118 V higher than that of the Pt CE.

Optimizing multi-walled carbon nanotubes as a low-cost and highly electrocatalytic counter electrode for QDSCs

The development of multi-wall carbon nanotubes (MWCNTs) counter electrodes (CEs) is limited due to its poor electrocatalytic activity in quantum dot sensitized solar cells (QDSCs). In this work, nanographite and CuS quantum dots (QDs) are introduced into acid-treated MWCNTs to form 3D structural composite CE for the purpose of improving the catalytic activity. The morphology and microstructure of CEs are observed with SEM and TEM images. Either the introduced nanographite or CuS QDs have attached to MWCNTs, which makes composite CE in the higher specific surface area. The electrical property and catalytic activity of CEs is analyzed through EIS and Tafel curves. The result shows that catalytic activity of MWCNTs CEs can be optimized through introducing either nanographite or CuS QDs to increase active sites. And the catalytic activity of nanographite-based CE is worse than that of CuS QDs-based one, whose performance is close to that of Pt CE in QDSCs. The photovoltaic parameters of QDSCs based on different CEs are investigated through J-V curves. Even if the power conversion efficiency (PCE) of QDSCs with the Pt CE is slightly higher than that of MWCNTs composite, the short circuit current density of cell with nanographite/MWCNTs composite CEs (10.510 mA cm−2) is higher than that of Pt CE (10.222 mA cm−2) and the open-circuit voltage of cell of CuS QDs/MWCNTs CEs (0.874 V) is higher than that of Pt CE (0.756 V). CuS QDs/MWCNTs composite can substitute Pt material commercially as a low-cost and high efficient CEs in QDSCs.