Facile Hot-injection Method Research Articles

Wurtzite CuIn(SxSe1-x)2 Nanocrystals: Colloidal Synthesis and Band-Gap Engineering.

CuIn(SxSe1-x)2 nanocrystals as an emerging class of functional materials present huge potential for industrial applications; however, the synthesis of CuIn(SxSe1-x)2 nanocrystals remains a formidable challenge in achieving both tunable band gap and phase. Here, we reported a facile hot-injection method for synthesizing a family of wurtzite CuIn(SxSe1-x)2 nanocrystals, enabling manipulation of the S and Se contents across the entire compositional range (0 ≤ x ≤ 1). The obtained nanocrystals exhibit band gaps ranging from 1.21 to 1.58 eV, which vary depending on the S/Se ratios in the products. This approach can be readily extended to other scenarios involving chalcogenide nanomaterials, thereby facilitating the advancement of next-generation functional materials and applications.

Hot injection synthesis of CuS decorated CdS and ZnS nanomaterials from metal thiosemicarbazone complexes as single source precursors: Application in the photocatalytic degradation of methylene blue

CdS and ZnS are considered excellent semiconductors for photocatalysis, but photocorrosion and low photocatalytic activity limit their practical application. In order to improve on their photocatalytic activities, Copper sulfide-decorated CdS and ZnS (CuS@CdS and CuS@ZnS) nanocomposites were synthesized from Cu(II), Zn(II) and Cd(II) complexes of 2–(phenyl(pyridin–2–yl)methylene)hydrazine–1–carbothioamide, as single source precursors using a facile hot injection method at 250 °C, employing olive oil as capping agent. The structure, morphology, and optical properties of the as-prepared nanocomposites were determined using various analytical techniques. The results of powder X-ray diffraction (p-XRD), energy dispersive X-ray spectroscopy (EDX) and elemental mapping showed the presence of CuS, CdS and ZnS in CuS@CdS and CuS@ZnS, confirming the formation of nanocomposites. Transmission Electron Microscopy (TEM) images show agglomeration of CuS nanoparticles on the surface of CdS and ZnS nanoparticles. Scanning electron microscopy (SEM) images of CuS@CdS and CuS@ZnS nanocomposites revealed an agglomerated flower-like structure with porous surface. The band gap energies of 2.84 eV and 3.12 eV for CuS@CdS and CuS@ZnS, respectively, obtained from Tauc plots, demonstrate that combining CuS with single CdS and ZnS has an effect on their optical properties which probably account for the improved photocatalytic responses. The photocatalytic performance of the as-prepared materials was evaluated using the photodegradation of methylene blue (MB) dye under UV light irradiation. Results show that the degradation efficiencies for CuS@CdS (57 %) and CuS@ZnS (65 %) nanocomposites exhibited higher photocatalytic activity compared to those of pure CuS (42.0 %), CdS (35.1 %) and ZnS (57 %), suggesting that thiosemicarbazone complexes can be used as precursors for the development of metal sulphide nanocomposites as useful photocatalysts for the degradation of organic pollutants.

Novel Au/Cu2NiSnS4 Nano-Heterostructure: Synthesis, Structure, Heterojunction Band Offset and Alignment, and Interfacial Charge Transfer Dynamics.

Considering the importance of physics and chemistry at material interfaces, we have explored the coupling of multinary chalcogenide semiconductor Cu2NiSnS4 nanoparticles (CNTS NPs) for the first time with the noble metal (Au) to form Au-CNTS nano-heterostructures (NHSs). The Au-CNTS NHSs is synthesized by a simple facile hot injection method. Synergistic experimental and theoretical approaches are employed to characterize the structural, optical, and electrical properties of the Au-CNTS NHSs. The absorption spectra demonstrate enhanced and broadened optical absorption in the ultraviolet-visible-near-infrared (UV-Vis-NIR) region, which is corroborated by cyclic voltammetry (CV) readings. CV measurements show type II staggered band alignment, with a conduction band offset (CBO) of 0.21 and 0.23 eV at the Au-CNTS/CdS and CNTS/CdS interface, respectively. Complementary first-principles density functional theory (DFT) calculations predict the formation of a stable Au-CNTS NHSs, with the Au nanoparticle transferring its electrons to the CNTS. Moreover, our interface analysis using ultrafast transient absorption experiments demonstrate that the Au-CNTS NHSs facilitates efficient transport and separation of photoexcited charge carriers when compared to pristine CNTS. The transient measurements further reveal a plasmonic electronic transfer from the Au nanoparticle to CNTS. Our advanced analysis and findings will prompt investigations into new functional materials and their photo/electrocatalysis and optoelectronic device applications in the future.

Inhibiting the phase transition of WO3 for highly stable aqueous electrochromic battery

Aqueous electrochromic battery (ECB) has shown intense potential for achieving energy storage and saving simultaneously. While tungsten oxide (WO3) is the most promising EC material for commercialization, the cycling stability of WO3-based aqueous ECBs is currently unsatisfactory due to the repeated phase transition during the redox process and the corrosion by acidic electrolytes. Herein, we present a titanium-tungsten oxide alloy (Ti-WO3) with controllable morphology and crystal phase synthesized by a facile hot injection method to overcome the challenges. In contrast to conventional monoclinic WO3, the Ti-WO3 nanorods can stably maintain their cubic crystal phase during the redox reaction in an acidic electrolyte, thus leading to dramatically enhanced response speed and cycling stability. Specifically, when working in a well-matched hybrid Al3+/Zn2+ aqueous electrolyte, our phase-transition-free cubic Ti-WO3 exhibits an ultra-high cycling stability (>20000 cycles), fast response speed (3.95 s/4.65 s for bleaching/coloring), as well as excellent discharge areal capacity of 214.5 mA h m−2. We further fabricate a fully complementary aqueous electrochromic device, for the first time, using a Ti-WO3/Prussian blue device architecture. Remarkably, the complementary ECB shows >10000 stable operation cycles, attesting to the feasibility of our Ti-WO3 for practical applications. Our work validates the significance of inhibiting the phase transitions of WO3 during the electrochromic process for realizing highly cyclable aqueous ECB, which can possibly provide a generalized design guidance for other high-quality metallic oxides for electrochemical applications.

Tunable white light emission in antimony doped vacancy-ordered double perovskite Cs2ZrCl6 nanocrystals

Design of stable white-light emitting materials based on the emerging lead-free metal halide colloidal nanocrystals is in urgent demand for lighting technology innovation. Herein, we developed a facile hot-injection method and optimize the synthesis conditions to prepare Sb3+ doped Cs2ZrCl6 nanocrystals with good uniformity and crystallinity. Sb3+ ions were doped into the Cs2ZrCl6 lattice and proved to occupy the sites of Zr4+ ions, generating additional absorption bands at lower energy and new emission band centered at 620 nm apart from the absorption and emission from the host. The emission at 620 nm from Sb3+ ions could be prompted by an energy transfer process between the host STEs and Sb3+ ions. Moreover, benefiting from two broad emission bands from singlet and triplet states of Sb3+ ions in Cs2ZrCl6 nanocrystals, we obtained tunable white-light-emitting nanocrystals by adjusting the dopant concentration. Our study provides a reliable method to design efficient single-emitter-based white-light emitting metal halide nanocrystals and promote their development in the field of lighting and displays.

Colloid synthesis of Ni12P5/N, S-doped graphene as efficient bifunctional catalyst for alkaline hydrogen evolution and triiodide reduction reaction

Designing high-efficient bifunction catalysts with excellent catalytic activity and enhanced charge-transfer capability in both alkaline hydrogen evolution reaction (HER) and triiodide reduction reaction (IRR) is of utmost significance to advance the development of green hydrogen production and photovoltaics, respectively, yet remains a crucial challenge. Here, highly dispersed and small-sized Ni12P5 nanocrystals with narrow size distribution was well attached on the surface of N, S co-doped graphene (Ni12P5/NSG) by the facile hot-injection method. As expected, the optimized Ni12P5/NSG requires a relatively low overpotential of 132.94 ± 0.08 mV to deliver a current density of 10 mA cm−2 in alkaline condition, accompanied with remarkable long-time durability with negligible attenuation over 50 h. Density functional theory (DFT) calculations revealed that the positively synergic effect between Ni12P5 and NSG are in favor of modulating the rate determining step of the dissociation of H2O to *(OH-H), thereby upgrading its HER activity. When used as the counter electrode catalyst for IRR in DSSCs, the resultant Ni12P5/NSG exhibits extraordinary Pt-like catalytic activity and well electrochemical stability in iodide-based electrolyte, delivering a high photoelectric conversion performance (PCE) comparable to Pt. The improved PCE can be attributed to the accelerated interfacial charge-transfer capability around active sites for facilitating the reaction kinetics of IRR, as demonstrated by DFT calculations. This work provides an effective strategy for synthesizing cost-effective composites with multi-active sites and offering valuable insight into the structure-performance relationship, which is conducive to guide the synthesis of promising catalysts in the energy conversion field.

Water-resistant perovskite-inspired copper/silver pnictohalide nanocrystals for photoelectrochemical water splitting

Lead halide perovskites (LHPs) photoelectrodes for photoelectrochemical (PEC) water splitting are promising candidates for solar-to-fuel conversion. However, the poor stability of LHPs in aqueous electrolyte media, together with the toxicity of lead, restricts the practical application of LHP photoelectrodes. Herein, we report the first-ever colloidal synthesis of quaternary Cu1.4Ag0.6BiI5 nanocrystals (NCs), a new lead-free perovskite-inspired nanomaterial, by a facile hot injection method. The Cu1.4Ag0.6BiI5 NCs exhibit an extraordinary water resistance, due to the well-defined coverage of hydrophobic ligands on the surface of NCs with unique layered cation disordered structure. Together with their high structural stability, the Cu1.4Ag0.6BiI5 NCs-based photoanode displays a maximum photocurrent density of 4.62 mA cm−2 at 1.23 V vs. reversible hydrogen electrode, and an applied bias photo-to-current efficiency of 2.94% without any protective layer. Our study highlights the great potential of lead-free Cu1.4Ag0.6BiI5 NCs-based photoelectrodes for a wide range of low-cost, eco-friendly, and high-performance PEC applications.

Temperature-dependent photoluminescence and third-order nonlinear optical properties of Mn2+ doped CsPbCl3 nanocrystals

In this work, CsPbCl3 and Mn:CsPbCl3 nanocrystals (NCs) were synthesized by a facile hot-injection method. In X-ray photoelectron spectroscopy test, the existence of Cs, Mn, Pb, Cl elements was confirmed, indicating that Mn2+ was successfully doped into CsPbCl3 NCs. The pure CsPbCl3 and Mn:CsPbCl3 NCs were studied by temperature dependent photoluminescence (PL) spectroscopy. It was found that Mn:CsPbCl3 NCs had higher exciton binding energy, which indicated that Mn:CsPbCl3 NCs may have stronger ability of third-order nonlinear optical effect. Furthermore, closed-aperture (CA) and open-aperture (OA) Z-scan tests were carried out on CsPbCl3 and Mn:CsPbCl3 NCs. CA Z-scan test found that they are all self-focusing media. OA Z-scan test found that Mn:CsPbCl3 NCs has a higher two-photon absorption coefficient, which is ∼4.5 times higher than that of pure CsPbCl3 NCs.

In-situ assembling 0D/2D Z-scheme heterojunction of Lead-free Cs2AgBiBr6/Bi2WO6 for enhanced photocatalytic CO2 reduction

All-inorganic lead-free halide double perovskites have emerged as rising star photocatalysts to substitute the toxic lead-based hailed perovskites (LHPs) owing to their unique photophysical properties. Nevertheless, their photocatalytic activities toward CO2 reduction are still far from comparable with the LHPs, associated with severe charge recombination and sluggish surface catalytic reaction. Herein, a delicate 0D/2D heterojunction of Cs2AgBiBr6/Bi2WO6 (CABB/BWO) was assembled by in-situ growing cubic CABB nanocrystals on the flat surface of BWO nanosheets via a facile hot-injection method. Density functional theory (DFT) calculations disclose that the work function and Fermi level difference between CABB and BWO give rise to charge redistribution at the interface upon the formation of the heterojunction, creating an internal electric field (IEF). Upon light irradiation, the IEF enables the photogenerated electron transfer from BWO to CABB via direct Z-scheme electron transfer mode with striking spatial charge separation as verified by in-situ X-ray photoelectron (XPS) and electron spin resonance (ESR) spectra. Consequently, the CABB/BWO heterojunction realizes 7-fold higher photocatalytic activity than pristine CABB with significant electron consumption rate of 87.66 µmol g-1h−1 under simulated solar light (AM 1.5G).

The effect of graphene on structure and optical properties of CdSe nanoparticles for optoelectronic application

CdSe-reduced Graphene Oxide (CdSe-rGO) nanocomposite was synthesized using a facile hot injection method with excellent control over the size and morphology. The superb distribution of the CdSe quantum dots (CdSe QDs) and the tightly anchoring to the graphene sheets enhance their optical properties. Therefore, the effect of reduced Graphene oxide (rGO) on the structure and optical properties of CdSe nanoparticles is studied by X-ray diffraction (XRD), UV–visible spectroscopy, and transmission electron microscopy (TEM). As well as Effective mass approximation model (EMA) and Polynomial Fitting Functions (PFF) were used to calculate the sizes of nanoparticles, yielding particle sizes ranging from 4.64 to 5.46 nm and 2.74–3.72 nm, respectively. These values were comparable to those obtained by TEM and XRD. Furthermore, the data revealed that the direct energy gap of the CdSe QDs was reduced from 2.33 eV for the smallest size to 2.17 eV for the largest size. The optical parameters of CdSe-rGO nanocomposite such as the refractive index and extinction coefficient were increased with the particle size growth. As well, optical dielectric constant and optical conductivity were improved due to the increase of the particle size of CdSe QDs in the CdSe-rGO nanocomposite. So, the capability of CdSe-rGO nanocomposite to tune the optical parameters makes it a suitable candidate for a wide range of applications, specifically optoelectronics.

Monodispersed ultra-thin BiOCl nanosheets with (110) facets exposed in situ self-assembled on reduced graphene oxide to enhance NO2 sensing performance at room temperature

In order to effectively increase gas adsorption active sites and boost the electrical conductivity of the materials, we synthesized ultra-thin BiOCl nanosheets with the uniform dispersion on reduced graphene oxide by a facile hot-injection method for detection of the concentration of the pollutant NO2. The size of BiOCl nanosheet was controlled within 25–30 nm. TEM, EPR and XPS unveil the presence of oxygen vacancy (VO) in the composite. The optimum BiG-3 sensor (the mass ratio of BiOCl/rGO is 1/3) exhibits a high sensitivity, elevated selectivity and remarkable long-term stability with the response (S = Ra/Rg) of 12.95–5 ppm NO2, response/recovery time of 9.3 s and 63 s, and as long as 60 days of stability at room temperature. The significant improvement in gas sensing performance of BiG-3 nanocomposite was mainly due to the highest selectivity with the higher adsorption energy of highly exposed (110) crystal planes for NO2, and a large number of oxygen vacancies providing additional active sites. Large areas of effective contact between ultra-thin BiOCl nanosheets and rGO can synergistically promote electron transport. Hence, the high sensing performance sensing material may be inspirations for actual productions.

Suppressing ion migration of CsPbBr x I3-x nanocrystals by Nickel doping and the application in high-efficiency WLEDs

All inorganic perovskite nanocrystals CsPbX3(X = Cl, Br, I) are the great potential candidates for the application of high-performance light emitting diodes (LED) due to their high Photoluminescence Quantum Yield (PLQY), high defect tolerance, narrow full-width half-maximum and tunable wavelength of 410–700 nm. However, the application of red-emitting (630–650 nm) CsPbBr x I3-x nanocrystals are perplexed by phase segregation due to the composition of mixed halides and the difference in halide ion mobility. Herein, we provide an effective strategy to suppressing the migration of Br/I ions through Ni2+ doping via a facile Hot-Injection method and the PLQY was improved as well. DFT calculations show that the introduction of Ni2+ causes a slight contraction of the host crystal structure, which improves the bond energy between Pb and halides and reduces the level of surface defects. Therefore, the phase stability is improved by Ni2+ doping because the phase segregation caused by ion migration in the mixed phase is effectively inhibited. Meanwhile, the non-radiative recombination in the exciton transition process is reduced and the PLQY is improved. What’s more, benefiting from the suppressed ion migration and enhanced PLQY, we combine the Ni2+-doped CsPbBr x I3-x nanocrystals with different Br/I ratios and YAG: Ce3+ phosphors as color conversion layers to fabricate high efficiency WLED. When the ratio of Br/I is 9:11, WLED has a color coordinate of (0.3621, 0.3458), the color temperature of 4336 K and presents a high luminous efficiency of 113.20 lm W−1, color rendering index of 94.9 under the driving current of 20 mA and exhibits excellent stability, which shows great potential in the application of LED.

Inorganic lead-free cesium copper chlorine nanocrystal for highly efficient and stable warm white light-emitting diodes

Inorganic cesium lead halide ( CsPbX 3 , X = Cl , Br, I) nanocrystals (NCs) attract extensive attention because of their excellent optoelectronic performance. However, the classic CsPbX 3 NCs suffer from toxicity and instability, which impede their further applications in commercial fields. Here the inorganic lead-free cesium copper chlorine NCs are synthesized by a facile hot-injection method. The blue-emission 3D CsCu 2 Cl 3 and green-emission 0D Cs 3 Cu 2 Cl 5 NCs are prepared at 70°C and 120°C, respectively, suggesting that the reaction temperature may account for the final components. Owing to the self-trapped exciton effect, the unique optical properties, such as high photoluminescence (PL) quantum yield, broadband emission, large Stokes shift, and long PL decay time, are demonstrated for both cesium copper chlorine NCs. Moreover, highly efficient and stable warm white light-emitting diodes are fabricated with CsCu 2 Cl 3 and Cs 3 Cu 2 Cl 5 NCs. The study highlights the promising potential for lead-free cesium copper chlorine nanocrystals in nontoxic solid-state lighting applications.

Design of earth-abundant ternary Fe1−xCoxS2 on RGO as efficient electrocatalysts for hydrogen evolution reaction

Developing inexpensive and earth-abundant materials instead of precious metal Pt has broad applications in the production of hydrogen through electrolysis of water. Herein, a series of ternary Fe1−xCoxS2 nanoparticles hybridized with reduced graphene oxide (RGO) (Fe1−xCoxS2/RGO) have been synthesized by a facile hot-injection method for hydrogen evolution reaction (HER) in acidic solutions. The electrochemical measurements show that the optimal HER activity is obtained when the ratio of Co is 61%, exhibiting a low overpotential of 198 mV at 10 mA cm−2 and a small Tafel slope of 94 mV dec−1. Moreover, density-functional theoretical calculations indicate that the incorporation of Co atoms can activate the electrocatalytic performance of FeS2 with a smaller Gibbs free energy for hydrogen adsorption (ΔGH*). The enhanced HER activity might be owing to the synergistic effects between the highly conductive RGO supports and the electroactive Fe0.39Co0.61S2. This study gives an insight into the design and development of the HER electrocatalysts based on earth-abundant Fe1−xCoxS2 and promotes the applications of transition metal dichalcogenides for hydrogen generation in the future.

Synergistically enhanced performance of transition-metal doped Ni2P for supercapacitance and overall water splitting.

Cost-effective and readily available catalysts applicable for electrochemical conversion technologies are highly desired. Herein, we report the synthesis of dithiophosphonate complexes of the type [Ni{S2P(OH)(4-CH3OC6H4)}2] (1), [Co{S2P(OC4H9)(4-CH3OC6H4)}3] (2) and [Fe{S2P(OH)(4-CH3OC6H4)}3] (3) and employed them to prepare Ni2P, Co-Ni2P and Fe-Ni2P nanoparticles. Ni2P was formed by a facile hot injection method by decomposing complex 1 in tri-octylphosphine oxide/tri-n-octylphosphine at 300 °C. The prepared Ni2P was doped with Co and Fe employing complexes 2 and 3, respectively, under similar experimental conditions. Doping Ni2P with Co and Fe demonstrated synergistic improvement of Ni2P performance as an electrocatalyst in supercapcitance, hydrogen evololution and oxygen evolution reactions in alkaline medium. Cobalt doping improved the Ni2P charge storage capacity with a supercapacitance of 864 F g-1 at 1 A g-1 current density. Fe doped Ni2P recorded the lowest overpotential of 259 mV to achieve a current density of 10 mA cm-2 and a Tafel slope of 80 mV dec-1 for OER, better than the undoped Ni2P and the benchmark IrO2. Likewise, Fe-doped Ni2P electrode required the lowest overpotential of 68 mV with a Tafel slope of 110 mV dec-1 to attain the same current density for HER. All catalysts showed excellent stability in supercapacitance and overall water splitting reactions, indicating their practical use in energy conversion technologies.

Enhanced photovoltaic performance of quantum-dot-sensitized solar cells using Graphene/Cu2-xSe composite counter electrode

The counter electrode (CE) plays an important role in determining the overall performance of quantum dots (QDs) sensitized solar cells (QDSCs) by collecting the electrons from the external circuit and catalyzing the reduction of oxidized electrolyte. Metal sulfides/selenides have been commonly used as CE in QDSCs. Among these CEs, the copper selenides are considered to be a superior CE for realizing highly efficient QDSCs due to its excellent catalytic activity. However, there has always been a trade-off between catalytic activity and conductivity in copper selenides CEs, such as the CE based on copper selenide nanoparticles has highest specific surface areas, leading to best catalytic activity compared with the CEs based on other copper selenide nanostructures (nanowires, nanorods, nanosheets etc.). But it also faces the worst conductivity due to a large number of grain boundaries existed in the copper selenide film based on nanoparticles. In this work, graphene (GR)/Cu2-xSe composite material has been prepared via a facile hot injection method, and their photovoltaic and electrochemical properties are studied in detail. Through optimizing the ratio of GR: Cu2-xSe and sintering temperature, the QDSCs based on the optimized GR/Cu2-xSe composite CE shows an obvious improvement in cell performances and yield a PCE of 6.66% compared with that of the cells based on bare Cu2-xSe (5.95%), bare Graphene (2.82%) and bare CuxS (4.85%) CEs. The improved performance of the composite CE was attributed to the combining effect of high catalytic activity of Cu2-xSe nanoparticles and good conductivity of graphene. This work demonstrates that GR/Cu2-xSe composite CE could be potential candidate for realizing high efficiency QDSCs.

MoS2-Carbon Inter-overlapped Structures as Effective Electrocatalysts for the Hydrogen Evolution Reaction.

The ability to generate hydrogen in an economic and sustainable manner is critical to the realization of a future hydrogen economy. Electrocatalytic water splitting into molecular hydrogen using the hydrogen evolution reaction (HER) provides a viable option for hydrogen generation. Consequently, advanced non-precious metal based electrocatalysts that promote HER and reduce the overpotential are being widely researched. Here, we report on the development of MoS2-carbon inter-overlapped structures and their applicability for enhancing electrocatalytic HER. These structures were synthesized by a facile hot-injection method using ammonium tetrathiomolybdate ((NH4)2MoS4) as the precursor and oleylamine (OLA) as the solvent, followed by a carbonization step. During the synthesis protocol, OLA not only plays the role of a reacting solvent but also acts as an intercalating agent which enlarges the interlayer spacing of MoS2 to form OLA-protected monolayer MoS2. After the carbonization step, the crystallinity improves substantially, and OLA can be completely converted into carbon, thus forming an inter-overlapped superstructure, as characterized in detail using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). A Tafel slope of 118 mV/dec is obtained for the monolayer MoS2-carbon superstructure, which shows a significant improvement, as compared to the 202 mV/dec observed for OLA-protected monolayer MoS2. The enhanced HER performance is attributed to the improved conductivity along the c-axis due to the presence of carbon and the abundance of active sites due to the interlayer expansion of the monolayer MoS2 by OLA.

Dye-sensitized photocatalytic hydrogen evolution by using copper-based ternary refractory metal chalcogenides

The exploration of photocatalytic transformation of solar energy into H2 through water splitting is an important direction towards sustainable and non-polluting energy in order to cover energy necessity partially. Ternary transition metal chalcogenides have been attracted attention among the other chalcogenides due to their potential applications in the photocatalytic and electrocatalytic hydrogen evolution. Herein, Cu2WS4 nanocubes and Cu2WSe4 nanosheets have been synthesized through a facile hot-injection method to benefit from the advantages such as minimizing the required pressure and reaction time by this technique. The photocatalytic hydrogen evolution activities of Cu2WS4 and Cu2WSe4 have been investigated under the visible light irradiation by using eosin-Y (EY) dye and triethanolamine (TEOA) as a photosensitizer and an electron donor, respectively. Cu2WS4 nanocubes have exhibited higher photocatalytic activity and stability than Cu2WSe4 nanosheets. The photocatalytic HER rates of Cu2WS4 and Cu2WSe4 have been determined as 1260 μmol g−1 h−1 and 861 μmol g−1 h−1, respectively. Photocatalytic HER activities were figured out in the order of Cu2WS4 > Cu2WSe4 which could be attributed to differences between proton reduction potential and the conduction band energy levels.

Photoelectrochemical Investigation on the Cadmium Sulfide (CdS) Thin Films Prepared using Spin Coating Technique

Photoelectrochemical cell technology is one of the simplest technologies, which converts light energy directly into electricity. The synthesis of cadmium sulfide (CdS) nanocrystals (NCs) was performed by the facile hot injection method. The NCs were characterized by different techniques such as XRD, Raman, UV-Vis, FESEM, and XPS. The XRD pattern confirms the phase pure hexagonal CdS NCs. The band gap of NCs calculated from the UV-Visible spectrum is at 2.40 eV, indicating good absorption in the visible spectrum. XPS analysis confirmed the presence of individual elements in CdS NCs. The CdS thin-films having different thicknesses were prepared on FTO substrates using the spin coating technique. Photoelectrochemical (PEC) investigation of CdS NCs thin-films photoelectrodes was performed by varying its thickness. The increase in the thickness of thin-films increased photocurrent density.

Lead-free cesium tin halide nanocrystals for light-emitting diodes and color down conversion.

Organometal halide perovskites are attracting a great deal of attention because of their long carrier diffusion lengths, wide wavelength tunability, and narrow-band emission. However, the toxicity of lead has caused considerable environmental and health concerns. In this work, lead-free cesium tin halide nanocrystals are synthesized and investigated. CsSnBr3 and CsSnI3 nanocrystals, 25 and 7 nm in size, are synthesized by a facile hot injection method. Absorption spectroscopy, photoluminescence spectroscopy, and X-ray diffraction were used to understand their structural and optical properties. CsSnBr3 and CsSnI3 nanocrystals show emission peaks at 683 and 938 nm, respectively. These nanocrystals show shelf stability for a few months. Temperature-dependent photoluminescence is utilized to know more about fundamental physical parameters, such as exciton binding energy, charge carrier–phonon interactions and band gap. Light-emitting diodes and color down-conversion films are also demonstrated using these lead free perovskite nanocrystals.