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The introduction of preheat treatment and film thickness, solution pH, and annealing temperature optimizations show significant PEC enhancement for the ZnO NRs/CdS photoanode.

The research on organic solar cells has attracted researcher attention because of their flexibility, low cost and relatively simple processing methods. However, the efficiency issue is the shortcoming of organic solar energy, and one of the key factors affecting the power conversion rate is the utilization of electron transport layer. Among the materials used for the electron transport layer, metal oxides are widely used due to their stability, ease of preparation and tunable energy band structure. This article review the advantages and disadvantages of metal oxides as electron transport layers particulary focus on SnO2, TiO2 and ZnO. The different nanostructures properties of the materials is also explores. A brief discussion on the use of metal oxides as electron transport layers in improving the performance of organic solar cells in the future is also elucidated.

Surface modification and wetting state transformation of ZnO based nanomaterials have been extensively investigated due to their substantial roles in current industrial applications. In this work, we demonstrated the formation of highly crystalline and ordered Bi/ZnO nanorods arrays (Bi/ZNRs) grown on FTO substrate via a feasible hydrothermal method, as a function of reaction time (t). The lateral diameter of the nanostructures were found increased from 23 nm to 43 nm when the reaction time increased from 30 min to 90 min. An in-depth analysis and incisive mechanism of crystal growth under the function of reaction time were proposed. The crystal defect which originated from different Bi incorporation pathways has been declared as the main factor altering the optical energy, electrical properties and band structure of Bi/ZNRs. The Bi/ZNRs showed a higher localize current of 14.5 pA as compared to pristine ZNRs under an 6V applied bias condition, revealing the nature of Bi as a pentavalent dopant that contributed to a density of free electron. Additionally, the Bi/ZNRs also revealed a red shifted in optical energy band gap and exhibit a wetting transition from hydrophobic to hydrophilic textured surface. The novel nanostructures reported herein exhibit interesting physical and optical properties for the fabrication of high performance optoelectronic devices.

Zinc oxide nanorods (ZnO NRs) have gained considerable research interest due to their robust energy conversion efficiency. In the present work, ZnO NRs arrays were pinpointed to probe their electromechanical response under strain conditions. ZnO seed was sputtered on different substrates by radio frequency magnetron sputtering (RF) technique at 80 W constant power and 3.49 × 10−5 mbar base pressure. The X-ray diffraction patterns exhibit hexagonal wurtzite structure with preferred c-axis crystal directions in the (002) plane. The average thickness of the seed layer for all the samples was estimated at around 214.6 nm. Surface roughness and morphologies of the nanorods have been characterized by atomic force microscopy (AFM) and field emission scanning electron microscopy (FESEM), respectively. FE-SEM images show homogeneous growth in different directions on substrates. The average diameters of ZnO NRs on silicon, glass and ITO were 51, 58 and 61 nm, respectively. The average length of all the nanorods on the substrates were measured around 1–2 μm. The local piezoresponse measurements conducted on two selected domain regions of the nanorod arrays had been characterized by piezoresponse force microscopy (PFM) to confirm the switching-piezoelectric behavior.

One-dimensional ZnO nanorods (ZnO NRs) have the edge over other nanostructures due to their unique properties. Current work fabricated ZnO NRs on pre-seeded ITO glass substrate through hydrothermal synthesis using customized hydrothermal set-up. The sources of Zn2+ and OH− ions were supplied continuously from zinc nitrate hexahydrate and hexamethylenetetramine (HMTA), respectively whereby the concentration of both precursors and the temperature of growth solution varied from 0.01 M to 0.05 M and from 80 °C to 120 °C, respectively. The impact of concentration and temperature variation on hydrothermal reaction and corresponding PEC cell performance is discussed. Field emission scanning electron microscopy (FESEM) results revealed that the morphology of prepared ZnO NRs arrays is concentration- and temperature-dependent. X-ray diffraction (XRD) reflected strong orientation along (002) direction for the hexagonal wurtzite ZnO NRs, and the film crystallinity greatly improved when the temperature increased. At optimal concentration and hydrothermal temperature, the ZnO NRs photoanode exhibited a bandgap value of 3.22 eV and achieved an impressive photocurrent density of 0.483 mA/cm2 that was attributed to the ordered rods alignment and improved optical properties. In addition, the electrochemical impedance spectroscopy (EIS) demonstrated optimized one-dimensional (1D) NRs sample showed better charge separation and transfer rate, which was two times larger than ZnO nanoparticles. The present work exhibited better photoelectrochemical performance than the other reported literature showing the high quality of ZnO NRs produced.

In situ growth of silver nanostructures (AgNSs) and reduction of graphene oxide (rGO) were successfully performed using a one-step segmented flow reaction system. The detailed crystal growth mechanism of the AgNSs on the rGO was discussed. The relationship between the presence of AgNSs (nanoparticles and nanowires) on the rGO and the rGO's electrochemical behaviour was investigated. In this report, it was found that the presence of silver nanoparticles (AgNPs) on the rGO's surface enhances its specific capacitance by 400% as compared to rGO-based devices. This novel finding provides an alternative in designing future electronic devices.

In this work, sodium cholate (NaC) was used as novel green reducing agent for graphene oxide (GO) reduction at 90 °C and short synthesis time using a continuous segmented flow reaction system. As a comparison, we had used the common reducing agent which is glucose to study its chemical and electrochemical properties. The morphologies of GO and reduced-graphene oxide (rGO) were characterized with X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscope (FESEM), Fourier transformed infrared (FTIR), Raman and Ultraviolet–Visible (UV–Vis) spectroscopy analysis demonstrated that reduction of GO occurred. For electrochemical measurements, the rGO was cast on carbon cloth to investigate the electrochemical performance with cyclic voltammetry (CV) and galvanostatic charge–discharge (GCD) measurements. NaC assisted rGO (rGO–NaC) was able to achieve a specific capacitance up to 94 F g−1 at 0.1 A g−1 and remarkable capacitance retention of 103% after 10,000 cycles. A flexible test shows that rGO–NaC bendable at 0°–60°. These results demonstrate that rGO–NaC is promising as flexible supercapacitors electrodes.

In this project, crystalline silver nanowires (AgNWs) are successfully grown using a continuous segmented flow process. The robust relationship among the structural, electrical and optical properties of the AgNWs in the function of the polyvinylpyrrolidone (PVP) chain length is elaborated. A concise carrier transport and a density mechanism are also discussed using a localized conductive atomic force microscopy analysis. The obtained results proved that the AgNWs synthesized using PVP with a chain length of 1.3 M exhibit excellent electrical and optical properties in the form of flexible transparent film with a sheet resistance of 90% at various bending angles. These findings present an alternative approach for production of AgNWs and fabrication of a high flexible transparent electrode.

Inverted organic solar cell (IOSC) devices with different volume ratios of In2S3 nanoparticles have been studied under local spectral irradiances in Malaysia with respect to that of AM1.5G. The J-V curves of encapsulated IOSC devices were measured outdoor using an Ivium Potentiostat and local spectral irradiances were acquired using an AVANTES spectrometer concurrently. All of the IOSC devices experienced significant improvement in power conversion efficiency (PCE) under the both local sunny and cloudy conditions with respect to the AM 1.5G, by 22–35% and 31–65%, respectively. From spectral analysis, the area under the graph of spectral irradiance in UV–visible region is significantly higher compared to infrared region for both local sunny and cloudy conditions, by 44.6% and 55.9%, respectively, while it is only recorded as 12.9% for AM 1.5G. Last but not the least, we have successfully verified the numerical analysis to predict device performance by comparing the simulated and measured PCE values for different irradiance intensities whereby the prediction of PCE is better under sunny condition with a deviation of 3.4–10.8% compared to cloudy conditions, with deviation of 28.9–30.5%.

Crystallinity and band offset alignment of inorganic electron acceptor play a vital role in enhancing the device performance of inverted organic solar cell (IOSC). In this report, homogenous and vertically-aligned chemical treated ZnO nanorods (ZNR) were successfully grown on fluorine-doped tin oxide (FTO) substrate via a fully-solution method. It was found that the morphology of ZnO was fine-tuned from truncated surface to tubular structure under both of the anionic (KOH) and protonic (HCl) treatment. An extraordinary defect quenching phenomenon and hyperchromic energy band edge shift were observed in 0.1 M KOH-treated ZNR proven by the highest (0 0 2) peak detection and the lowest defect density. Compared with the pristine sample, the 0.1 M KOH-treated ZNR device showed a remarkable improvement in power conversion efficiency (PCE) up to 0.32%, signifying the effectiveness of anodic treatment. The robust correlation between the dependency of chemical treated ZNR and the device performance was established. This work elucidates a feasible method towards efficient IOSC devices development.

Charge transport dynamics in ZnO based inverted organic solar cell (IOSC) has been characterized with transient photocurrent spectroscopy and localised photocurrent mapping-atomic force microscopy. The value of maximum exciton generation rate was found to vary from 2.6 × 1027 m−3s−1 (Jsat = 79.7 A m−2) to 2.9 × 1027 m−3s−1 (Jsat = 90.8 A m−2) for devices with power conversion efficiency ranging from 2.03 to 2.51%. These results suggest that nanorods served as an excellent electron transporting layer that provides efficient charge transport and enhances IOSC device performance. The photovoltaic performance of OSCs with various growth times of ZnO nanorods have been analysed for a comparison between AM1.5G spectrum and local solar spectrum. The simulated PCE of all devices operating under local spectrum exhibited extensive improvement with the gain of 13.3–13.7% in which the ZnO nanorods grown at 15 min possess the highest PCE under local solar with the value of 2.82%.

In this work, the photocatalytic performance of Ag3PO4, Nb2O5 and Ag3PO4/Nb2O5 hybrid photocatalysts to degrade methyl orange dye, MO, in an aqueous solution under visible light irradiation was evaluated. The Ag3PO4 and Ag3PO4/Nb2O5 photocatalysts, with various Ag to Nb molar ratios, were prepared using a facile precipitation method. The photocatalysts were characterized by X-ray diffraction, UV–Visible, X-ray Photoelectron, and Photoluminescence spectroscopies. Upon the addition of Ag3PO4, the band gap energy of Nb2O5 decreased from 3.0 eV to 2.7 eV, indicating the possible use of the Ag3PO4/Nb2O5 hybrid photocatalysts under visible light irradiation. All of the prepared Ag3PO4/Nb2O5 catalysts exhibited higher photocatalytic performance than Ag3PO4 in degrading methyl orange dye under 23-watt visible light irradiation. The Ag3PO4/Nb2O5 catalyst, with a mole ratio of 2:1, exhibited the fastest MO degradation rate of 7.3 × 10−2 min−1, which is twice faster than that of Ag3PO4. The catalyst also shows better stability, as it is reusable for up to six experimental cycles while maintaining its photocatalytic activity above 60%.

Carbon dots (CDs) were successfully derived from water hyacinth leaves and the binary composite was achieved by incorporating CDs with g-C3N4 through hydrothermal treatment. The average particle size of CDs was found to be 3.1 nm and a blue-green fluorescence was emitted under the UV light irradiation. Both of the composites loaded with 20 wt.% (20CDs/g-C3N4) and 40 wt.% (40CDs/g-C3N4) of CDs achieved the highest degradation efficiency of 2,4-dichlorophenol (2,4-DCP) with 1.7 times higher than that of pure g-C3N4. This work successfully improved the properties of g-C3N4 by elongating the lifetime of photogenerated electrons and widening the visible light response. Both of 20CDs/g-C3N4 and 40CDs/g-C3N4 recorded the highest photocatalytic performance in degrading 2,4-DCP with degradation rate constant of 0.0194, and 0.0186 min−1, respectively. This is contributed by the prolonged charge carrier lifetime in 20CDs/g-C3N4; good visible light absorption and high specific surface area in 40CDs/g-C3N4. For the scavenger test, hole (h+) and superoxide radical (·O2−) were acknowledged as the key active species in photocatalysis.

The fabrication of photocatalyst with a visible response and prolonged lifetime of charge carriers is a significant tactic to treat EDCs. In this work, a green synthesis route was adopted to prepare carbon quantum dots (CQDs) from Arabian dates (AD-CQDs) via hydrothermal method. The different weight percentages of fabricated AD-CQDs (10, 15 and 20 wt%) were coupled with graphitic carbon nitride (g-C3N4) to construct AD-CQDs/g-C3N4 composites to degrade 2,4-dicholorophenol (2,4-DCP) under sunlight irradiation with an average light intensity of ~973 × 100 lx. The obtained AD-CQDs were used as a highly selective sensor for ferric (Fe3+) ions, with a low detection limit of 1 nM. The increase loading of AD-CQDs resulted in particle agglomeration which decreased the specific surface area of g-C3N4 from 74.799 m2/g to 62.542 m2/g. The low specific surface area in the composites did not hamper the photocatalytic performance in which all composites showed a higher degradation rate than that of g-C3N4. With the optimum loading of AD-CQDs (20 wt%), the composite degraded 100% of 2,4-DCP in 90 min which was 1.7 times higher than g-C3N4 (59.48%). The excellent photocatalytic performance was mainly correlated to the effective separation of photogenerated electrons as evidenced by TRPL and transient photocurrent response. The second factor is visible light response because of the minor decrease of band gap energy as evidenced in UV–vis DRS spectra. Both factors are attributed to the dual functions of AD-CQDs as electron acceptors and photosensitizers. The simple and low-cost synthesis strategy could be an alternative to obtain sunlight driven photocatalysts without coupling with metal dopants or other semiconductors.

Incorporating cadmium sulfide quantum dots (CdS QDs) onto ZnO nanorod (ZNRs) has been investigated to be an efficient approach to enhance the photovoltaic performance of the inverted organic solar cell (IOSC) devices based on ZNRs/poly (3-hexylthiophene) (P3HT). To synthesize CdS/ZNRs, different durations of deposition per cycle from 1 to 9 min were used to deposit CdS via SILAR technique onto ZNRs surface grown via hydrothermal method at low temperature on FTO substrate. In typical procedures, P3HT as donor polymer were spun-coating onto CdS/ZNRs to fabricate IOSC devices, followed by Ag deposition as anode by magnetron sputtering technique. Incorporation of CdS QDs has modified the morphological, structural, and optical properties of ZNRs. Incorporation of CdS QDs onto ZNRs also led to higher open circuit voltage (Voc) and short circuit current density (Jsc) of optimum ZNRs/CdS QDs devices due to the increased interfacial area between ZNRs and P3HT for more efficient exciton dissociation, reduced interfacial charge carrier recombination as a result of lower number of oxygen defects which act as electron traps in ZnO and prolonged carrier recombination lifetime. Therefore, the ZNRs/CdS QDs/P3HT device exhibited threefold higher PCE (0.55%) at 5 min in comparison to pristine ZNR constructed device (0.16%). Overall, our study highlights the potential of ZNRs/CdS QDs to be excellent electron acceptors for high efficiency hybrid optoelectronic devices.

We report our investigation on the growth of ZnO nanostructure on a patterned interdigitated microelectrode (IDE) using chemical bath deposition (CBD). Piezoresponse force microscopic techniques were used to characterise the piezoelectric material domain of the grown ZnO nanostructures. The synthesised ZnO nanostructures exhibits a hexagonal wurtzite structure with the c-axis preferred crystal orientation in the (002) plane. The average thickness of the ZnO seed layer was 467.5 nm, whereas the diameter and length of ZnO nanostructure were measured to be 2.73 µm and 6.96 µm respectively. The combine effect of Zinc nitrate and HTMA concentration and seed layer thickness are considered as the main reason for crystal morphology evolution. The ZnO nanostructures exhibited a phase switch of the response and hysteresis in the plot of phase versus dc voltage, as evidenced by the polarization exchanging of its ferroelectric behaviour. These results provide a fundamental understanding of piezoresponse ZnO nanostructure for future energy applications.

In this article, a simple new technique has been developed for the preparation of ZnO/ZnAl2O4-mixed metal oxide (MMO) as anode materials for visible light dye-sensitized (DS) photodetector using Zn/Al-layered double hydroxide (LDH) as precursor. Subsequently, a detailed correlation between the structural properties of the prepared samples and the photo-responsive behavior of the fabricated DS photodetectors was elucidated. Specifically, it is evidenced that a high surface area of the prepared mesoporous MMO anode materials exhibit excellent dye absorptivity and thus facilitate free electron transfer and increase the photocurrent in the fabricated DS photodetector. A significant bathochromic shift was observed in the optical energy of the prepared MMO samples under the increment of molar ratio, providing a short electron transfer pathway in the optimized Z7A DS photodetector, which in turn demonstrated photo-responsivity and photo-detectivity of 6 mA/W and 1.7 × 10+10 Jones, respectively. This work presents an alternative approach for the design of an eco-friendly MMO-based DS photodetector.

A homogeneous CuO-ZnO nanostructure with tunable morphology and optical band structure is successfully synthesized via a hydrothermal method under the different dopant mole ratios of Cu. The robust correlation between the crystallite size, surface morphology, optical band gap alteration of the synthesized CuO-ZnO and its performance in photoelectrochemical (PEC) activity are investigated and compared to the reference ZnO based photocathode. In this report, it is found that the morphology of hexagonal ZnO nanorod is changed to nanosheet and vertically align CuO-ZnO based nanograss after the Cu incorporation. This result is mainly due to the composition phase change after the excessive incorporation of Cu metal into ZnO lattice. Furthermore, the optical band gap of the sample also presented a bathochromic shifted after the Cu insertion. The measurements on PEC activity of CuO-ZnO nanostructure was performed under the irradiation of a 100 mWcm−2 Xenon light in 0.5M Na2SO4 electrolyte. Among the sample, 0 Zn:1 Cu exhibited a highest photocurrent density which is 5 fold as compared to its reference ZnO samples. This finding could be due to the highest surface active area and lowest optical energy band gap in the 0 Zn:1 Cu nanograss that eventually contributes to a high free electron density that facilitates the charge transport in the photoelectrochemical cells. This novel approach could provide an alternative to the future solar hydrogenation application.

The controllable growth of metal sulfide–metal oxide based nanomaterials with a tunable band gap structure is vital in the fabrication of new generation optoelectronic devices. In this paper, two-dimensional hierarchical CdS/ZnO nanorod arrays were successfully grown via a low temperature hydrothermal-SILAR method. A concise mechanism related to the surface and band gap modification on the CdS/ZnO nanorods was investigated under various CdS deposition cycles (N). The diameter and surface roughness properties of the sample were found to be linearly dependent on the value of N. A bathochromic shift in the optical energy band gap revealed the quantum size effects of the CdS/ZnO nanorods, as well as the induced interface band state and energy band split in the ZnO band state. An impressive improvement in the crystallinity of the sample was also observed under the CdS treatment. The correlation between the optical band gap and photovoltaic efficiency was evaluated. The results proved that the ZnO nanorod/CdS devices exhibited a threefold higher power conversion efficiency in comparison to a pristine ZnO nanorod device.

Efficient approach to synthesize (001)-faceted ZnO nanoplates thin film on an ITO substrate is reported via a conventional hydrothermal method. The field emission scanning electron microscopy and X-ray photoelectron spectroscopy analysis revealed that the surface structure and chemistry of the ZnO nanoplate thin film are strongly influenced by the ratio between the Zinc presursor and hexamethylenetetramine (HMT) concentrations in the reaction. The catalytic properties of the (001) faceted hexagonal ZnO nanoplate was examined in the conversion of 4-nitrophenol to 4-aminophenol in the absence of reducing agent under ultrasonication at room-temperature. In typical process, it was found that the conversion rate as high as 4.483 × 10−2 mol min−1 can be obtained from this system. Highly-reactive (001) faceted nanoplate with high oxygen vacancy is assumed as the driving force for such efficiency catalytic properties. The synthetic procedure and characterization of ZnO nanoplates will be discussed in detail.

One-dimensional ZnO nanorods (ZNRs) synthesized on fluorine-doped tin oxide (FTO) glass by hydrothermal method were modified with cadmium sulfide quantum dots (CdS QDs) as an electron transport layer (ETL) in order to enhance the photovoltaic performance of inverted organic solar cell (IOSC). In present study, CdS QDs were deposited on ZNRs using a Successive Ionic Layer Adsorption and Reaction method (SILAR) method. In typical procedures, IOSCs were fabricated by spin-coating the P3HT:PC61BM photoactive layer onto the as-prepared ZNRs/CdS QDs. The results of current-voltage (I-V) measurement under illumination shows that the FTO/ZNRs/CdS QDs/ P3HT:PC61BM/ PEDOT: PSS/Ag IOSC achieved a higher power conversion efficiency (4.06 %) in comparison to FTO/ZNRs/P3HT:PC61BM/PEDOT: PSS/Ag (3.6 %). Our findings suggest that the improved open circuit voltage (Voc) and short circuit current density (Jsc) of ZNRs/CdS QDs devices could be attributed to enhanced electron selectivity and reduced interfacial charge carrier recombination between ZNRs and P3HT:PC61BM after the deposition of CdS QDs. The CdS QDs sensitized ZNRs reported herein exhibit great potential for advanced optoelectronic application.

The crystallographic plane of the ZnO nanocrystals photocatalyst is considered as a key parameter for an effective photocatalysis, photoelectrochemical reaction and photosensitivity. In this paper, we report a simple method for the synthesis of a new (1 0 1) high-energy plane bounded ZnO nanocubes photocatalyst directly on the FTO surface, using a seed-mediated ultrasonic assisted hydrolysis process. In the typical procedure, high-density nanocubes and quasi-nanocubes can be grown on the substrate surface from a solution containing equimolar (0.04 M) zinc nitrate hydrate and hexamine. ZnO nanocubes, with average edge-length of ca. 50 nm, can be obtained on the surface in as quickly as 10 min. The heterogeneous photocatalytic property of the sample has been examined in the photodegradation of methyl orange (MO) by UV light irradiation. It was found that the ZnO nanocubes exhibit excellent catalytic and photocatalytic properties and demonstrate the photodegradation efficiency as high as 5.7 percent/μg mW. This is 200 times higher than those reported results using a relatively low-powered polychromatic UV light source (4 mW). The mechanism of ZnO nanocube formation using the present approach is discussed. The new-synthesized ZnO nanocubes with a unique (1 0 1) basal plane also find potential application in photoelectrochemical devices and sensing.

Anion passivation effect on metal-oxide nano-architecture offers a highly controllable platform for improving charge selectivity and extraction, with direct relevance to their implementation in hybrid solar cells. In current work, we demonstrated the incorporation of fluorine (F) as an anion dopant to address the defect-rich nature of ZnO nanorods (ZNR) and improve the feasibility of its role as electron acceptor. The detailed morphology evolution and defect engineering on ZNR were studied as a function of F-doping concentration (x). Specifically, the rod-shaped arrays of ZnO were transformed into taper-shaped arrays at high x. A hypsochromic shift was observed in optical energy band gap due to the Burstein-Moss effect. A substantial suppression on intrinsic defects in ZnO lattice directly epitomized the novel role of fluorine as an oxygen defect quencher. The results show that 10-FZNR/P3HT device exhibited two-fold higher power conversion efficiency than the pristine ZNR/P3HT device, primarily due to the reduced Schottky defects and charge transfer barrier. Essentially, the reported findings yielded insights on the functions of fluorine on (i) surface –OH passivation, (ii) oxygen vacancies (Vo) occupation and (iii) lattice oxygen substitution, thereby enhancing the photo-physical processes, carrier mobility and concentration of FZNR based device.

One dimensional (1D) zinc oxide, ZnO nanostructures have shown promising results for usage in photodiode and optoelectronic device due to their high surface area. Faster and conventional method for synthesis ZnO nanorods has become an attention for researcher today. In this paper, ZnO nanorods have been successfully synthesized via two-step process, namely alcothermal seeding and seed-mediated microwave hydrolysis process. In typical process, the ZnO nanoseeds were grown in the growth solution that contained equimolar (0.04 M) of zinc nitrate hexahydrate, Zn (NO3).6H2O and hexamethylenetetramine, HMT. The growth process was carried inside the inverted microwave within 5- 20 s. The effect of growth parameters (i.e. concentration, microwave power, time reaction) upon the modification of ZnO morphology was studied. ZnO nanostructures were characterized by Field emission scanning electron microscope (FESEM) and X-ray diffraction (XRD). The densities of nanorods were evaluated by the Image J analysis. It was found that the morphology (e.g. shape and size) of nanostructures has changed drastically with the increment of growth solution concentration. The density of ZnO nanorods was proven to increase with the increasing of reaction time and microwave power. We hypothesize that the microwave power might enhance the rate of nucleation and promote the faster nanostructure growth as compared with the normal heating condition due to the superheating phenomenon. This method might promote a new and faster alternative way in nanostructure growth which can be applied in currently existing application.

Fibrous, ultra small nanorod-constructed Pt nanocubes (PtNCs) directly grown on the substrate surface show enhanced heterogeneous catalytic reduction of methyl orange with efficiency 103 times higher compared to those in homogeneous reaction. The PtNCs may find potential application in organic reactions and photoelectrochemical devices.