Plasmon assisted intense blue-green emission from ZnO/ZnS nanocrystallites

Excellent luminescence properties of ZnO/ZnS nanocrystallites prepared using simple wet chemical approach at room temperature have been reported. ZnS coating on the surface of ZnO nanocrystallites enhanced the green emission (around 500 nm) by a factor of 2. The intensity of the blue emission around 450 nm of ZnO/ZnS nanocrystallites is observed to be as high as three times the emission intensity of pure ZnO nanocrystallites. A further overall increase by a factor of ∼2.5 has also been observed in the intensity of wide blue-green emission when the sample was prepared onto grating compared to that of the samples prepared onto uncoated as well as gold coated quartz. The enhanced emission is thought to be due to plasmon assisted electromagnetic field enhancement near nanocrystallites-metal interface. This is supported by power dependent photoluminescence measurements. The strong enhanced blue-green emission covering a wide spectral range of ∼375-650 nm signifies potential optoelectronic applications in near UV and VIS wavelength regimes.     

Rational Engineering of p-n Heterogeneous ZnS/SnO2 Quantum Dots with Fast Ion Kinetics for Superior Li/Na-Ion Battery

Constructing heterogeneous nanostructures is an efficient strategy to improve the electrical and ionic conductivity of metal chalcogenide-based anodes. Herein, ZnS/SnO₂ quantum dots (QDs) as p-n heterojunctions that are uniformly anchored to reduced graphene oxides (ZnS-SnO₂@rGO) are designed and engineered. Combining the merits of fast electron transport via the internal electric field and a greatly shortened Li/Na ion diffusion pathway in the ZnS/SnO₂ QDs (3–5 nm), along with the excellent electrical conductivity and good structural stability provided by the rGO matrix, the ZnS-SnO₂@rGO anode exhibits enhanced electronic and ionic conductivity, which can be proved by both experiments and theoretical calculations. Consequently, the ZnS-SnO₂@rGO anode shows a significantly improved rate performance that simple counterpart composite anodes cannot achieve. Specifically, high reversible specific capacities are achieved for both lithium-ion battery (551 mA h g⁻¹ at 5.0 A g⁻¹, 670 mA h g⁻¹ at 3.0 A g⁻¹ after 1400 cycles) and sodium-ion battery (334 mA h g⁻¹ at 5.0 A g⁻¹, 313 mA h g⁻¹ at 1.0 A g⁻¹ after 400 cycles). Thus, this strategy to build semiconductor metal sulfides/metal oxide heterostructures at the atomic scale may inspire the rational design of metal compounds for high-performance battery applications.     

Hierarchical Nanorods of MoS2/MoP Heterojunction for Efficient Electrocatalytic Hydrogen Evolution Reaction

Hierarchical nanostructures with tailored component and architectures are attractive for energy‐related applications. Here, the delicate design and construction of hierarchical MoS₂/MoP (H‐MoS₂/MoP) nanorods for the hydrogen evolution reaction (HER) are demonstrated. This multiscale design rationally combines the compositional and structural advantages of MoS₂/MoP heterojunction into a hierarchical architecture, which can modulate electronic structure of S, remarkably facilitating the electrocatalytic HER. Benefitting from their unique architecture and electronic structure, the H‐MoS₂/MoP nanorods exhibit excellent performance for HER with ultralow overpotential of 92 mV at current density of 10 mA cm^?2 in 1 m KOH and high stability. This work not only provides an efficient approach to constructing hierarchical heterojunctions, but also a multiscale strategy for all‐round regulation of the electronic structure and hierarchical morphology of nanomaterials for energy‐related applications.     

Core/Shell ZnO/ZnS Nanoparticle Electron Transport Layers Enable Efficient All-Solution-Processed Perovskite Light-Emitting Diodes

Solution-processed perovskite-based light-emitting diodes (PeLEDs) are promising candidates for low-cost, large-area displays, while severe deterioration of the perovskite light-emitting layer occurs during deposition of electron transport layers from solution in an issue. Herein, core/shell ZnO/ZnS nanoparticles as a solution-processed electron transport layer in PeLED based on quasi-2D PEA₂Cs_n−1Pb_nBr_3n+1 (PEA = phenylethylammonium) perovskite are employed. The deposition of ZnS shell mitigates trap states on ZnO core by anchoring sulfur to oxygen vacancies, and at the same time removes residual hydroxyl groups, which helps to suppress the interfacial trap-assisted non-radiative recombination and the deprotonation reaction between the perovskite layer and ZnO. The core/shell ZnO/ZnS nanoparticles show comparably high electron mobility to pristine ZnO nanoparticles, combined with the reduced energy barrier between the electron transport layer and the perovskite layer, improving the charge injection balance in PeLEDs. As a result, the optimized PeLEDs employing core/shell ZnO/ZnS nanoparticles as a solution-processed electron transport layer exhibit high peak luminance reaching 32 400 cd m⁻², external quantum efficiency of 10.3%, and 20-fold extended longevity as compared to the devices utilizing ZnO nanoparticles, which represents one of the highest overall performances for solution-processed PeLEDs.     

Controlled Synthesis of Kinked Ultrathin ZnS Nanorods/Nanowires Triggered by Chloride Ions: A Case Study

Colloidal synthesis of kinked ultrathin ZnS nanorods/nanowires with mixed phases using tiny Ag₂S nanocrystals as catalysts is reported. It is found that chloride ions can induce the controlled morphology transition from straight to kinking. The synthetic parameters modulating the growth of kinked ZnS nanorods/nanowires are systematically investigated. Chloride ions introduced in the reaction can generate more proportion of wurtzite phase by slowing the nucleation and growth rates during the growth of one‐dimensional (1D) ZnS nanorods/nanowires. The formation of kinked morphology is responsible for the increased domains of mixed stacking and twinning in single 1D nanostructures. The present recipe on controlled synthesis of 1D kinked nanorods/nanowires provides a model of crystal growth control, and these unique 1D nanostructures may also offer new opportunities to fabricate nanodevices with special functions.     

CdSe and CdSe/ZnS quantum dots for the detection of C-reactive protein

In this study, a method for the detection of C-reactive protein (CRP) using CdSe and CdSe/ZnS quantum dots (QDs) is proposed. CdSe and CdSe/ZnS core-shell QDs are synthesised by using 2-mercaptosuccinic acid (MSA) as a capping agent. These QDs were then subjected to various characterisation studies, namely X-ray diffraction and transmission electron microscope for size and structure, Fourier transform infrared spectroscopy for the confirmation of functional groups, ultraviolet–visible absorption and fluorescence spectroscopy for optical characteristics and dynamic light scattering for hydrodynamic changes of QDs. Two biochemical mixtures were developed: one by mixing blood serum containing CRP and CdSe-phosphorylethanolamine (PEA) and the other by mixing blood serum with CdSe/ZnS-PEA. When these mixtures are observed for fluorescence due to interaction of QDs with CRP, a correlation between changes in fluorescence for different concentrations of CRP is noted. The result demonstrates that CRP can be detected with the help of QDs without using any antibodies.     

Synergistical Coupling Interconnected ZnS/SnS2 Nanoboxes with Polypyrrole‐Derived N/S Dual‐Doped Carbon for Boosting High‐Performance Sodium Storage

Metal sulfides possess tremendous potentials owing to their high specific capacity for sodium storage. However, the huge volume expansion, accompanied with structural collapse and unsatisfied electric conductivity upon continuous cycling, always lead to inferior rate capability and severe cycling fading. In this work, binary metal sulfide (ZnS/SnS₂) nanoboxes confined in N/S dual‐doped carbon shell (ZSS@NSC) are fabricated through a facile co‐precipitation method involving the wrapping of polypyrrole, and subsequent in situ sulfidation process. Such a well‐designed heterogeneity between ZnS and SnS₂ provides rapid Na⁺ insertion and enhanced charge transport by creating an electric field at the heterointerface. More significantly, the formation of polypyrrole‐derived N/S dual‐doped carbon is synergistically coupled with the ZnS/SnS₂ to create a unique and robust architecture, further strengthening the interconnect function at the heterointerface, which improves electric/ion transfer and mitigates the volume variation during the long‐term cycling process. Herein, this as‐prepared ZSS@NSC exhibits satisfied specific capacity, excellent rate property, and superior cyclic stability (a reversible capacity of 456.2 mAh g^?1 with excellent capacity retention of 97.2% after 700 stable cycles at ultrahigh rate of 5 A g^?1). The boosted Na‐storage properties demonstrate that the optimized strategy of structure‐engineering has a broad prospect to promote energy storage applications.     

Highly luminescent blue emitting CdS/ZnS core/shell quantum dots via a single-molecular precursor for shell growth

Highly luminescent blue-emitting CdS/ZnS core/shell quantum dots (QDs) were synthesized in N-oleoylmorpholine by two facile steps: first, the CdS core QDs were prepared via a simple one-pot method involving a direct reaction of Cd precursor cadmium stearate and S precursor S powder in solvent N-oleoylmorpholine; second, ZnS shells were successively overcoated on CdS core through the decomposition of single molecular precursor zinc diethyldithiocarbamate. The thickness of shell was precisely tuned by controlling drip feed speed and amount of shell precursor. The obtained CdS/ZnS core/shell QDs showed the maximum photoluminescent quantum yield of 54.8% and narrow spectra bandwidth, exhibiting high monodispersity, good color purity and long fluorescent lifetimes. The CdS/ZnS core/shell QDs with tunable emission wavelength of 424–470 nm were obtained by controlling the thickness of ZnS shell overgrown on different-sized CdS QDs, which are promising materials for blue light-emitting devices.     

Excellent photocatalytic performance under visible-light irradiation of ZnS/rGO nanocomposites synthesized by a green method

ZnS/graphene nanocomposites with different graphene concentrations (5, 10 and 15 wt.%) were synthesized using L-cysteine as surfactant and graphene oxide (GO) powders as graphene source. Excellent performance for nanocomposites to remove methylene blue (MB) dye and hexavalent chromium (Cr(VI)) under visible-light illumination was revealed. TEM images showed that ZnS NPs were decorated on GO sheets and the GO caused a significant decrease in the ZnS diameter size. XRD patterns, XPS and FTIR spectroscopy results indicated that GO sheets changed into reduced graphene oxide (rGO) during the synthesis process. Photocurrent measurements under a visiblelight source indicated a good chemical reaction between ZnS NPs and rGO sheets.     

A new fluorescent film sensor for Pb(II) ions developed by simulating bio-mineralization process synthesizing of ZnS/CS nanocomposite

Chitosan/zinc sulfide (CS/ZnS) nano-composite films have been prepared by simulating bio-mineralization process. Factors affecting the hydrothermal stability and fluorescence properties of the films have been studied. Furthermore, the sensing properties of nano-composite films to lead ions have been systematically investigated. SEM and TEM observations showed that the size of ZnS particles is 70 nm, and the particles are evenly distributed within the CS films. The fluorescence emission of the nano-composite films indicates that the sizes of real fluorescing ZnS particles are less than 20 nm. This suggests that ZnS particles observed via SEM and TEM may be aggregates of smaller ZnS particles, and the smaller particles may be separated by the organics. The fluorescence emission (363 nm) of the nano-composite films is very sensitive to the presence of Pb ions. C_(Pb²⁺₎ increased from 0 to 664.2 mg L⁻¹ increases the emission dramatically. The emission is hardly affected by common ions in water, except for the iron ions. The films may be developed as excellent sensing films for Pb ions in water.     

Multilayer Polypyrrole Nanosheets with Self‐Organized Surface Structures for Flexible and Efficient Solar–Thermal Energy Conversion

Converting solar energy into concentrated heat is very appealing for various applications. Polypyrrole (PPy) is known to possess excellent photothermal property with low thermal conductivity, and thus is an ideal candidate for solar–thermal energy conversion. However, solar–thermal materials based on PPy or other conducting polymers still exhibit limited energy conversion efficiency due to the lack of effective light‐trapping schemes. Here, it is demonstrated that multilayer PPy nanosheets with spontaneously formed surface structures such as wrinkles and ridges via sequential polymerization on paper substrates can dramatically enhance broadband and wide‐angle light absorption across the full solar spectrum, leading to an impressive solar–thermal conversion efficiency of 95.33%. The intriguing solar–thermal properties and structural features of multilayer PPy nanosheets can be used for solar heating and photoactuators. Meanwhile, when used for solar steam generation, the measured efficiency could achieve ≈92% under one sun irradiation. The hierarchically multilayer structure is mechanically flexible and robust, holding great potential for practical solar energy utilization. This study provides a simple and straightforward approach toward engineering light‐weight and thermally insulating polymers into efficient solar–thermal materials for emerging solar energy‐related applications.     

Strain-Engineering of Mesoporous Cs3Bi2Br9/BiVO4 S-Scheme Heterojunction for Efficient CO2 Photoreduction

Slow charge kinetics and unfavorable CO₂ adsorption/activation strongly inhibit CO₂ photoreduction. In this study, a strain-engineered Cs₃Bi₂Br₉/hierarchically porous BiVO₄ (s-CBB/HP-BVO) heterojunction with improved charge separation and tailored CO₂ adsorption/activation capability is developed. Density functional theory calculations suggest that the presence of tensile strain in Cs₃Bi₂Br₉ can significantly downshift the p-band center of the active Bi atoms, which enhances the adsorption/activation of inert CO₂. Meanwhile, in situ irradiation X-ray photoelectron spectroscopy and electron spin resonance confirm that efficient charge transfer occurs in s-CBB/HP-BVO following an S-scheme with built-in electric field acceleration. Therefore, the well-designed s-CBB/HP-BVO heterojunction exhibits a boosted photocatalytic activity, with a total electron consumption rate of 70.63 µmol g⁻¹ h⁻¹, and 79.66% selectivity of CO production. Additionally, in situ diffuse reflectance infrared Fourier transform spectroscopy reveals that CO₂ photoreduction undergoes a formaldehyde-mediated reaction process. This work provides insight into strain engineering to improve the photocatalytic performance of halide perovskite.