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Abstract We demonstrate the growth of ZnSe microspheres in large quantities by using a mixture of Zn and Se as precursors via direct current arc discharge method without the addition of any catalyst or template. The as-obtained samples were characterized by X-ray diffraction, Raman, energy-dispersive X-ray spectrometry, scanning and transmission electron microscopy, and ultraviolet-visible reflectance spectroscopy. The majority of the ZnSe microspheres which were composed of ZnSe nanoparticles exhibited perfectly spherical morphology and a distinct hollow structure with a relatively rough surface. The growth mechanism of ZnSe hollow microspheres has been discussed. Room-temperature excitation and emission spectra as well as the fluorescence lifetime of ZnSe hollow microspheres were measured and the results showed ZnSe hollow microspheres exhibit an intensive wide broad emission bands from 550 to 750 nm upon 470 nm excitation with fast decay time 1.09 ms and CIE chromaticity coordinates (0.65, 0.34), which was ascribed to characteristic structure defects (vacancies and interstitials) in ZnSe. Additionally, the temperature dependent emission behavior was measured and discussed. [ABSTRACT FROM AUTHOR]

A rapid and single-step method for the fabrication of a zinc selenide (ZnSe) concave microlens array through the high-speed line-scanning of a femtosecond laser pulse is presented. Approximately 1.1 million microlenses, with minimized volume and high transparency at wavelengths between approximately 0.76–20 μm were fabricated within 36 min. More importantly, the size of the microlenses can be controlled by adjusting the laser power. Their high-quality infrared optical performance was also demonstrated. This method holds great promise for the development of ZnSe-based micro-optical devices.

• A green and simple synthesis of ZnSe/ZnS quantum dots in aqueous solution was presented. • The influences of synthesis parameters on structure and optical properties of the particles were investigated in details. • ZnSe/ZnS showed better luminous intensity and lifespan than ZnSe and blue luminous. The core-shell quantum dots of ZnSe-ZnS were synthesized in aqueous solution using glutathione (GSH) in an environmentally friendly way. The effects of the concentration of GSH, the synthesis temperature and the NaOH concentration (pH) on the microstructural and optical properties of the prepared core-shell systematically were investigated. Analysis of the XRD patterns and TEM particle images confirmed that the round-typed ZnSe-ZnS quantum dots of size 3 to 5 nm were formed. Comparing to the single core ZnSe, the core-shell ZnSe-ZnS showed an increase in photoluminescence (PL) emission intensity up to 130%. In addition, the core-shell quantum dots showed a good long-term stability maintaining their high PL intensity for at least 84 days. The synthesis process optimization was discussed in detail. The light emission intensities of the quantum dots were dependent on the GSH concentration. The optimum GSH concentration for the core-shell synthesis was found to be around 0.1 mmol. High temperature above 70 C for the core-shell synthesis generally improved the optical properties. However, light discharge characteristics were correlated with the core-shell synthesis temperature and the pH in solution. At the high temperatures of 70 °C and 90 °C, the emission intensities were degraded with high pH of 13 due to the dissociation of the ligand were accelerated. The optimized ZnSe-ZnS quantum dots showed high color purity emitting blue fluorescence light of 378 nm with the narrow full width at half maximum (FWHM) less than 20 nm. Optimization of synthesis parameters showed the possibilities of the simple and eco-friendly manufacture of long term stable and efficient ZnSe-ZnS core-shell quantum dots in aqueous solutions for display applications. [ABSTRACT FROM AUTHOR]

Multi-junction solar cells exhibit superior power conversion efficiency (PCE) in comparison with their single-junction counterparts. The tunable bandgap, low-cost, elevated short circuit current density (J sc), and open-circuit voltage (V oc) of perovskite solar cells (PSCs) have led to their widespread adoption as top sub-cells in tandem devices. Stability remains a significant challenge for these cells. To address this issue, carbon perovskite solar cells (CPSCs) have emerged as a potential solution, offering enhanced stability without hole transport layers (HTLs). This study focuses on the simulation of HTL-free CPSCs using an improved electron transport material (ETM) instead of TiO 2. The implementation of this enhancement leads to a notable increase in the PCE of the CPSCs, rising from 7.97 % to 14.38 %. Through optimizing the defect concentration and doping density of the perovskite absorber layer, a significant improvement in the PCE is achieved, reaching 16.87 %. A novel configuration incorporating a gradient doping profile in the perovskite layer is introduced, leading to a remarkable enhancement in the PCE, which reaches 22.22 %. Two absorber materials are suggested, CIGS and GeTe, as bottom sub-cells. Three tandem cell configurations, PSC/CIGS, CPSC/CIGS, and CPSC/GeTe, are rigorously explored based on the optimized sub-cells. The PCEs of the proposed configurations are found to be 30.52 %, 22.7 %, and 36.59 %, respectively. Computational analysis reveals that the PSC/CIGS tandem cell exhibits lower stability against temperature variations compared to CPSC/CIGS and CPSC/GeTe. Additionally, the proposed CPSC/GeTe tandem is highly praised as a favorable contender, offering both high efficiency and stability among the various configurations considered in this study. [Display omitted] • Many tandem cells have been designed and simulated based on practical calibrations. • A carbon-based perovskite cell (CPSC) without hole transport layer is more stable. • CPSC/CIGS tandem cell is proposed with an efficiency of 22.7 %. • Upon replacing CIGS sub-cell with GeTe, an efficiency of 36.59 % is obtained. • The temperature effects on all the proposed tandem cells are investigated. [ABSTRACT FROM AUTHOR]

Large area attenuated total reflectance-Fourier transform infrared spectroscopy (LAATR-FTIR) is introduced as a novel technique for detecting small microplastics (MPs) down to 1.3 μm. Two different LAATR units, one with a zinc selenide (ZnSe) and one with a germanium (Ge) crystal, were used to detect reference MPs < 20 μm, and MPs in marine water samples, and compared with μ-FTIR in transmission mode. The LAATR units performed well in identifying small MPs down to 1.3 μm. However, they were poorly suited for large MPs as uneven particle thickness resulted in uneven contact between crystal and particle, misinterpreting large MPs as many small MPs. However, for more homogeneous matrices, the technique was promising. Further assessment indicated that there was little difference in spectra quality between transmission mode and LAATR mode. All in all, while LAATR units struggle to substitute transmission mode, it provides additional information and valuable information on small MPs. [Display omitted] • LAATR and transmission mode have different results on MP shape and number. • LAATR unit has low detection limit compared with transmission mode. • LAATR unit with ZnSe and Ge crystal can detect MPs down to 2.1 and 1.3 μm. • LAATR performed well in detecting small MPs, and limited in detecting large MPs. [ABSTRACT FROM AUTHOR]

[Display omitted] Lithiophilic ZnSe nanoparticles/N-doped carbon modified carbon cloth (ZnSe/NC@CC) acts as lithium host to achieve homogenous Li nucleation and growth. The LiFePO 4 -based (LFP) cell, utilizing the established anode (Li@ZnSe/NC@CC), achieves an impressive capacity retention of 90.3% after 600 cycles even at a low N/P ratio of around 2.2. • A framework with polarity and good conductivity is developed as a lithium host. • ZnSe/NC@CC shows a high adsorption effect and low migration barrier to Li ions. • Long-term Li plating/stripping is improved with Li@ZnSe/NC@CC anode. • A low N/P ratio and high rate capacity for LFP full cell are realized. The commercialization of lithium metal anode possessing ultra-high theoretical capacity has been impeded by safety hazards and inadequate cycling lifespan because of the unregulated lithium dendrites. Here, a framework where MOF-derived ZnSe nanoparticles/N-doped carbon nanosheets are attached to 3D flexible carbon cloth (called ZnSe/NC@CC) is developed. This framework functions as a lithium host for mitigating the detrimental effects of lithium dendrites within the cell. The ZnSe and N-doped sites aid in homogenizing lithium nucleation due to the strong lithiophilicity. The ion/electron conducting mixture (Li 2 Se and Zn) derived from the lithiation of ZnSe is advantageous for the following homogeneous Li+ flux distribution/deposition. Therefore, the Li@ZnSe/NC@CC electrode performs superbly under 1 mA cm−2, with low lithium nucleation overpotential (8 mV) and extended cycling lifespan (2500 h). Moreover, the LiFePO 4 -based (LFP) cell, utilizing the established anode, achieves an impressive cycling lifespan (over 1200 cycles at 1C, 1C = 170 mAh g−1) and enhanced rate performance (116.7 mAh g−1 at 10C). It is worth mentioning that the cell maintains an excellent capacity retention of 90.3% after 600 cycles even at a low N/P ratio (defined as the ratio of negative to positive capacity) of around 2.2. This research offers valuable insights for creating a dendrite-free anode in high-energy–density lithium batteries. [ABSTRACT FROM AUTHOR]

In aqueous zinc-ion batteries (AZIBs), the zinc metal anode faces serious problems such as dendrite growth, interface corrosion, and byproduct accumulation, which hinder the commercialization process of AZIBs. Herein, an inorganic hybrid interfacial layer ZnF 2 /ZnSe (ZnFS) including the insulating interfacial phase (ZnF 2 ) and conductive interfacial phase (ZnSe) has been manufactured. ZnF 2 provides excellent corrosion resistance, inhibiting the corrosion and passivation of the zinc metal anode to enhance interfacial stability. The conductive ZnSe can reduce the interfacial resistance and induce the rapid migration of Zn 2+ , leading to the uniform deposition of Zn to inhibit the dendrite growth. Consequently, the Zn/ZnFS//Zn/ZnFS symmetrical batteries can run stably for more than 2200 h at 1 mA cm -2 /1 mAh cm -2 and over 700 h at 5 mA cm -2 /5 mAh cm -2 . At the same time, the average Coulombic efficiency of the Zn/ZnFS//Ti half batteries reaches 98.3% after 600 cycles (1 mA cm -2 /1 h), indicating that the reversibility of zinc was greatly improved. The full batteries based on the Zn/ZnFS anode and (NH 4 ) 2 V 10 O 25 ·8H 2 O cathode perform a high capacity ratio of 73.4% after 620 cycles at 1 A g -1 . The concept of hybrid interface layer design can provide inspiration for the modification of metal anode.

In a novel approach that capitalized on the differential solubility product (K sp ) of ZnSe and Ag 2 Se, a unique ZnSe/Ag 2 Se binary heterostructure was efficiently synthesized in situ. ZnSe/Ag 2 Se exhibited excellent antimicrobial efficiency under visible light. Incorporating Ag 2 Se into ZnSe significantly enhanced the photoelectric performance of the catalyst, greatly accelerating the separation of the photogenerated electrons in the system. Active species removal experiments determined that ·O 2 - and H 2 played crucial roles in photocatalytic antibacterial efficiency. Further investigation into the levels of cellular membrane peroxidation, bacterial morphology, and intracellular contents concentration revealed that during the photocatalytic antimicrobial process, reactive oxygen species initially oxidize phospholipids in the cell membrane, leading to damage to the external structure of the cell and leakage of the intracellular contents, ultimately resulting in bacteria inactivation. The photocatalytic antimicrobial process of ZnSe/Ag 2 played crucial roles in photocatalytic antibacterial efficiency. Further investigation into the levels of cellular membrane peroxidation, bacterial morphology, and intracellular contents concentration revealed that during the photocatalytic antimicrobial process, reactive oxygen species initially oxidize phospholipids in the cell membrane, leading to damage to the external structure of the cell and leakage of the intracellular contents, ultimately resulting in bacteria inactivation. The photocatalytic antimicrobial process of ZnSe/Ag 2 Se fundamentally deviates from conventional methods, offering new insights into efficient disinfection and photocatalytic antimicrobial mechanisms.

Graphical abstract Highlights • Rapid, microwave-assisted synthesis of 2D ZnSe and ZnSe:Mn nanosheets and microflowers. • Systematically characterization of NCs in terms of structural and optical properties. • The photocatalytic activity of ZnSe and ZnSe:Mn NCs evaluated by degradation of methyl orange (MO). • Superior photocatalytic activity of ZnSe:Mn depending on Mn doping concentration. Abstract Zinc selenide (ZnSe) and manganese-doped zinc selenide (ZnSe:Mn) nanosheet and microflower morphologies were successfully fabricated in only 15–25 min in solvothermal reactions under microwave irradiation. In order to compare the effect of microwave heating on the properties of obtained ZnSe nanocrystals, the synthesis under conventional heating was conducted additionally in similar conditions. The obtained nanocrystals were systematically characterized in terms of structural and optical properties using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), diffuse reflectance UV–vis spectroscopy (DR UV–vis), Fourier-transform infrared spectroscopy (FT-IR), photoluminescence spectroscopy (PL), X-ray photoelectron spectroscopy (XPS), Atomic Absorption spectroscopy (AAS) and Brunauer-Emmett-Teller (BET) surface area analysis. ZnSe and ZnSe:Mn nanosheets were synthesized with the length of 300–600 nm, width of 150–400 nm, and thickness about 10–30 nm. The photocatalytic activity of ZnSe and ZnSe:Mn nanocrystals with different morphologies was evaluated by the degradation of methyl orange (MO). The results show that all samples had high coefficient of degradation of MO under ultraviolet irradiation (UV). Manganese-doped ZnSe nanocrystals exhibited superior photocatalytic activity and can offer many wide opportunities and perspectives in the field of photocatalysis and solar energy conversion. [ABSTRACT FROM AUTHOR]

Abstract One way to improve the rate of hydrogen production from water-splitting reactions is by the separation of photogenerated carriers. This separation process can be achieved with narrow bandgap semiconductors. ZnSe has a 2.7 eV bandgap, but its photocatalytic activity is very low due to a high recombination rate of the photogenerated carriers. Therefore, a combination of Bi 2 S 3 and ZnSe may potentially produce a visible-light-active photocatalyst, utilizing bandgap engineering and the p-n junction effect. ZnSe, Bi 2 S 3 and Bi 2 S 3 -ZnSe nanocomposites were prepared by a hydrothermal method. Bi 2 S 3 at different weight percentages (3–15 wt%) was decorated with ZnSe nanoparticles. The hydrogen evolution reaction was conducted in the investigation of ZnSe, Bi 2 S 3 and Bi 2 S 3 -ZnSe photocatalytic efficiency. The results demonstrate that photocatalytic efficiency was highly affected by the Bi 2 S 3 weight percent. The optimal weight percent for Bi 2 S 3 was 15 wt%, at which the rate of hydrogen evolution was 2600 μmol g−1 h−1 within 240 min in the presence of 1.2 g/L photocatalyst. [ABSTRACT FROM AUTHOR]

Highlights • ZnO/ZnSe heterostructures were synthesized successfully via one-pot hydrothermal approach. • The synthesized heterostructure photocatalysts have been employed for the degradation of Congo Red. • The higher photocatalytic activities are ascribed to efficient charge separation. Abstract Environmental remediation using sunlight is one of the most promising and cost-effective approaches to mitigate environmental hazards significantly related to the industrial development. In the present work, we report the synthesis of ZnO/ZnSe heterostructure via one-pot hydrothermal approach for the photocatalytic degradation of diazo dye i.e. Congo red. XRD analysis verified the crystal structure, phase purity and successful synthesis of the ZnO/ZnSe heterostructure photocatalysts. Moreover, the morphology and elemental composition of the photocatalysts were studied using scanning electron microscopy (SEM), transmission electron microscopy (TEM) and electron dispersive X-ray spectroscopy (EDX), respectively. The alignment of energy levels for the synthesized heterostructured photocatalysts was also drawn while using UV-visible diffuse reflectance spectroscopy (DRS) and X-ray photoelectron spectroscopy (XPS). Finally, the as-synthesized heterostructures were employed as efficient photocatalysts for the degradation of Congo red under the illumination of UV-visible light. Our results indicated that ZnO/ZnSe heterostructure photocatalysts with maximum ZnSe content can efficiently degrade the dye up to 91% which might be attributed to the effective charge separation as extended solar absorption due to narrow bandgap of ZnSe. [ABSTRACT FROM AUTHOR]

Abstract Structural and optical properties of SiO 2 (600 nm)/Si films successively implanted with two types of ions (Zn and Se) or three types of ions (Zn, Se and S) and afterwards annealed at 900 °C were investigated. RS, PL and TEM methods were used to characterize A 2 B 6 nanocrystals synthesized in SiO 2 matrix. The Raman spectra recorded using an excitation with two different laser lines (355 and 473 nm) have shown the formation of ZnSe nanocrystals after a double implantation of Zn and Se ions, while ZnS x Se 1−x nanoclusters have been synthesized after a triple implantation of Zn, Se and S ions. Based on Raman spectra recorded with blue and UV excitations, the possible sulfur content (x ≈ 0.4) has been estimated for synthesized ternary alloy. The intensive PL bands for SiO 2 films implanted with (Zn, Se, S) and (Zn, Se) were detected in the blue and red spectral ranges, respectively. [ABSTRACT FROM AUTHOR]

Abstract: In order to alleviate the effect of the surface defects on the emission properties of quantum dots, copper ions‐doped ZnSe quantum dots (QDs) in the glasses are prepared using melt‐quenching and subsequent thermal annealing methods. For glasses without copper doping, tunable band‐edge emission from ZnSe QDs is achieved. For glasses with copper doping, efficient energy transfer from ZnSe QDs to copper ions is observed, and efficient broad band emission from copper ions is realized at the expense of the band‐edge emission of ZnSe QDs. Absorption spectra, size‐dependent broad‐band emission spectra and electron spin resonance spectra show the cupric ions are doped into the ZnSe QDs. Results reported here shows that doping of transition‐metal ions into semiconductor QDs in glasses is promising for development of high efficient luminescent glasses. [ABSTRACT FROM AUTHOR]

Optical absorption spectra of colloidal solutions and films based on ZnSe quantum dots (QD) stabilized with thioglycerol or thioglycolic acid and precipitated on spherical nanoparticles of silicon dioxide are presented and studied. In addition to the usual quantum-size effect, two contributions to the energy of excitons in QD were found. The first (surface effect) occurs in colloidal solutions of QD stabilized by thioglycerol due to the absorption of the thiol –SH group by Zn and Se atoms. The second (polarization effect) is additional and is formed in the solid films of both colloids due to the dielectric mismatch between QD materials and the surrounding matrix. It was shown for the first time that the electronic excitation energy transfer on a spherical surface in dense ZnSe QD array occurs due to the mechanism of strong interaction (hybridization of orbitals) between neighboring QD, which is satisfactorily described by the proposed theoretical model. [ABSTRACT FROM AUTHOR]

Abstract A comparative study of anti-reflection microstructures (ARMs) and ARMs with Al 2 O 3 coatings (Al 2 O 3 /ARMs) on zinc selenide (ZnSe) has been carried out. The transmittance and electric field intensities were analyzed and presented using finite-difference time-domain (FDTD) simulations. ARMs were successfully fabricated on ZnSe surfaces by reactive ion etching and an Al 2 O 3 layer was deposited onto the ARMs by an ion beam sputtering method. The theoretical analysis and experimental results showed that the transmittance of Al 2 O 3 /ARMs-treated ZnSe had a close relationship with the thickness of Al 2 O 3 layer and was higher than that of ARMs-treated ZnSe in the 2–5 μm wavelength range, which was due to the fact that the Al 2 O 3 /ARMs had a better graded refractive index profile. The angle-dependent reflectance of ZnSe with Al 2 O 3 /ARMs was lower than that with ARMs. A difference of the spatial distribution of the electric field intensity between ARMs and Al 2 O 3 /ARMs was observed due to the surface Al 2 O 3 coating, which predicted qualitative laser damage thresholds for both structures. The results of this study provide potential applications in high-efficiency IR optoelectronic devices and high power mid-infrared laser systems. Highlights • The transmittance of Al 2 O 3 /ARMs on ZnSe is enhanced by the more graded refractive index profile. • The composite antireflective structures allowed a significant improvement in omni-directional antireflective properties. • A change of the spatial distribution of the electric field intensity between ARMs and Al 2 O 3 /ARMs is observed. [ABSTRACT FROM AUTHOR]

The purpose of this work is to achieve the best efficiency of Cu(In, Ga)Se2 solar cells by replacing the CdS buffer layer with other nontoxic materials. The simulation tool used in this study is Silvaco-Atlas package based on digital resolution 2D transport equations governing the conduction mechanisms in semiconductor devices. The J-V characteristics are simulated under AM1.5G illumination. Firstly, we will report the modeling and simulation results of CdS/CIGS solar cell, in comparison with the previously reported experimental results [1]. Secondly, the photovoltaic parameters will be calculated with CdS buffer layer and without any buffer layer to understand its impact on the output parameters of solar cells. The simulation is carried out with the use of electrical and optical parameters chosen judiciously for different buffers (CdS, ZnOS and ZnSe). In comparison to simulated CdS/CIGS, the best photovoltaic parameters have been obtained with ZnOS buffer layer. The structure has almost the same open circuit voltage Voc and fill factor FF, and higher short circuit current density Jsc, which results in slightly higher conversion efficiencies. [ABSTRACT FROM AUTHOR]

We present our results related to the growth, photoluminescence characterization and modelling of a quantum well (QW) involving a type II heterostructure, Zn1-xCdxSe/ZnTe/Zn1-xCdxSe, confined within ZnSe barriers with a type I band alignment. We show that this type of hybrid QWs may be employed for the elaboration of Zn1-xCdxSe/ZnSe/GaAs based red emitters without exceeding a Cd content around 42%. The design of the ZnSe/Zn1−xCdxSe/ZnTe/Zn1−xCdxSe/ZnSe QW was based on calculations employing the transfer matrix method under the effective mass, envelope function approximation. The QW was epitaxially grown at 275°C on a semi-insulating GaAs (001) substrate by a combination of molecular beam epitaxy for the ZnSe barriers, submonolayer pulsed beam epitaxy for the ZnCdSe layers of the QW and atomic layer epitaxy for the central ZnTe QW layer. A heterostructure with a central region of 2 ZnTe monolayers surrounded at each side by seven monolayers of Zn1−xCdxSe, with x ∼ 0.41, presented a room temperature exitonic deep red emission with a peak at 1.829 eV. [ABSTRACT FROM AUTHOR]

In this paper, nanostructured ZnSe/ZnS multilayer thin films were prepared on silicon substrates by electron beam evaporation technique. This heterostructure takes advantage of the properties of ZnSe and ZnS, with ZnSe and ZnS acting as light-emitting and passivation layers, respectively. To enhance the luminescence performance, the optimal thickness of ZnS and ZnSe films and the annealing conditions were investigated. Nanostructured films with 3.5 nm ZnSe and 15 nm ZnS annealed at 660 °C for 100 min in N 2 were found to be the optimal conditions. In addition, crystal structures and surface morphologies of the films were characterized, which showed outstanding blue emission. The excellent blue emission achieved in the optimized films indicates that nanostructured ZnSe/ZnS multilayer films could be used as novel luminescence materials. [ABSTRACT FROM AUTHOR]

The CdTe nanocrystal (NC) is an outstanding, low-cost photovoltaic material for highly efficient solution-processed thin-film solar cells. Currently, most CdTe NC thin-film solar cells are based on CdSe, ZnO, or CdS buffer layers. In this study, a wide bandgap and Cd-free ZnSe NC is introduced for the first time as the buffer layer for all solution-processed CdTe/ZnSe NC hetero-junction thin-film solar cells with a configuration of ITO/ZnO/ZnSe/CdTe/MoOx/Au. The dependence of the thickness of the ZnSe NC film, the annealing temperature and the chemical treatment on the performance of NC solar cells are investigated and discussed in detail. We further develop a ligand-exchanging strategy that involves 1,2-ethanedithiol (EDT) during the fabrication of ZnSe NC film. An improved power conversion efficiency (PCE) of 3.58% is obtained, which is increased by 16.6% when compared to a device without the EDT treatment. We believe that using ZnSe NC as the buffer layer holds the potential for developing high-efficiency, low cost, and stable CdTe NC-based solar cells. [ABSTRACT FROM AUTHOR]

Earth-abundant and low-toxic Cu 2 ZnSnSe 4 (CZTSe) kesterite-compound semiconducting absorbers were deposited on bare Mo(600 nm) and Mo(10 nm)/MoN(50 nm)/Mo(600 nm) substrates using a two-stage selenization process. The effects of the MoN barrier on the properties of the CZTSe films and device performance were investigated. X-ray diffraction, Raman spectroscopy, and scanning electron microscopy showed that the addition of a MoN barrier layer resulted in a decrease in the MoSe 2 layer thickness. Raman depth analysis showed that for the bare Mo substrates, the ZnSe phase was distributed from the middle to the surface of the absorber, whereas it was distributed at the bottom for the MoN barrier substrates. MoSe 2 formation was suppressed greatly with the MoN barrier layer. On the other hand, the current-voltage curve of the device was distorted significantly by the incorporation of the MoN barrier layer. The electro-optical properties will be discussed in conjunction with the ZnSe distribution in the absorber layers. [ABSTRACT FROM AUTHOR]

Photoelectrochemical (PEC) cell is a meaningful way to fulfil carbon dioxide (CO 2 ) conversion to value-added chemicals, but the exploration of ideal photocathode materials with high photo-conversion efficiency remains a challenge. Herein, porous ZnO@ZnSe core/shell nanosheet array on fluorine doped-tin oxide (FTO) glass is synthesized via dissolution-recrystallization mechanism by using ZnO nanosheet array as the template, and is used for the first time as the photocathode for PEC reduction of CO 2 . The effect of ZnSe loading amount on PEC responses of composite electrode is investigated in detail. Under the irradiation of visible light, the optimized ZnO@ZnSe photocathode exhibits onset potentials at 0.39 V ( vs. RHE) in CO 2 -purged 0.5 M NaHCO 3 solution and achieves the photocurrent of 1.17 mA cm -2  at −0.11 V ( vs. RHE). Interestingly, the competitive H 2 evolution reaction can be suppressed effectively and thereby the selectivity for CO 2 reduction reactions especially for CO formation is increased when the applied voltage became more negative. The faradic efficiency of CO increases dramatically from 4.2% at 0.2 V to 52.9% at −0.4 V and the electron selectivity for CO 2 reduction increases from 70.1% to 96.6% accordingly. These results demonstrate that ZnO@ZnSe composite electrode can work as promising photocathode for efficient CO 2 reduction. [ABSTRACT FROM AUTHOR]

Abstract: This work describes for the first time the employment of water soluble GSH‐ZnSe QDs stabilized by XG and MWCNT for electrode modification in the detection of Cd ions in a highly sensitive and selective manner resulting from the unique structure and surface chemistry of the used QDs. The surface of a glassy carbon (GC) electrode was modified through casting a thin layer of multiwalled carbon nanotubes (MWCNT) followed by a complex layer of ZnSe quantum dots (QDs) stabilized by xanthan gum (XG). Due to the electrocatalytic properties of MWCNT and electroanalytical performance of ZnSe‐XG complex, the new modified electrode significantly improves the sensitivity and selectivity of Cd(II) detection and exhibits enhanced performance in comparison to bare GC, ZnSe/GC and ZnSe/MWCNT/GC electrodes. Strong interactions between ZnSe QDs and XG resulting from hydrogen bonding and complexing association led to stabilization of ZnSe QDs and higher affinity towards Cd(II) ions adsorption compared to a ZnSe QDs film alone. The modified electrode showed linear response in a wide concentration range from 100 nM to 5 μM (R2=0.9967) along with a high sensitivity of 156.6 nA ⋅ mol−1 ⋅ L−1 and a low detection limit of 20 nM. The electrode shows high selectivity to Cd with negligible interference from other metal ions and salts. [ABSTRACT FROM AUTHOR]

Emerging part of condensed matter science, which deals with the systems of extreme two‐dimensionality, renews the interest in natural 2D objects such as planar stacking faults (SFs) in semiconductor crystals. We report on the observation of an excitonic state localized at the 1D intersection of the SF with a high quality ZnSe quantum well (QW). The micro‐photoluminescence measurements are performed in a specimen used for preceding transmission electron microscopy studies. We demonstrate that the observed narrow lines are polarized along SFs and their linewidths depend on the SFs length. For short SFs, the linewidth can be as low as 0.15 meV. Using the combination of the effective mass approach and the density functional theory calculations we show that the exciton localization is due to the intrinsic electric field inside the SF, which also leads to a spatial separation of electron and hole in the exciton. The 1D intersection of perfect natural and artificial 2D objects can serve as a promising playground for the study of subtle excitonic effects in single defects. [ABSTRACT FROM AUTHOR]

Photoluminescence (PL) spectra of ZnSe single crystals grown by the chemical vapor transport (CVT) method with iodine as a transport agent and doped with the group V elements (P, As, Sb, Bi) during the growth are investigated in the wavelength range between 420 and 750 nm at temperatures between 10 and 300 K. The effect of co-doping of ZnSe samples with iodine and the group V elements on luminescence centers and PL spectra is studied. It is established that acceptor-type associative centers of activator luminescence (I Se A Se), where A represents the group V element, are formed as a result of co-doping. These centers are responsible for new wide bands of long-wavelength emission with maxima between 575 and 580 nm at room temperature. Photoluminescence mechanism that explains the behavior of the observed PL bands with temperature variation is proposed. • ZnSe samples co-doped with I and group V elements (P, As, Sb, Bi) are grown by CVT method with iodine as a transport agent. • PL bands attributed to FE (441.4 nm), DBE (442.6 nm) and ABE (443.5 nm) are observed for ZnSe(I) and ZnSe(I):Sb at 10 K. • Ionization energies of shallow donors (I Se) and acceptors (Sb Se) are estimated to be Δ E D ≈ 35 meV and Δ E А ≈ 130 meV. • (I Se A Se) acceptor-type associative centers, where A represents the group V element, are formed as a result of co-doping. • (I Se A Se) acceptor-type associative centers are responsible for wide PL bands with maxima between 570 and 580 nm. [ABSTRACT FROM AUTHOR]

Time series of acoustic emission pulses were excited in ductile ZnS and ZnSe ceramics either by a falling weight or by indenting the Vickers pyramid. Energy distributions in emitted acoustical emission pulses were found to be random (Poisson-like) in the events of short (0.3–0.5 ms) impact forcing. In the case of the gradual (∼1 s) indenting, the energy distributions followed a power law typical for the self-similar structures appearing through long-range interactions between nucleating microcracks (scaling). In ductile materials, the rate of straining governs the dislocation motion. Provided enough loading time, such as in indenting experiments, the sliding dislocations form bunches, which serve as weak points for the crack nucleation. Given a tend to self-organizing in the ensemble of dislocations, the energy release in impeded cracking process (i. e. indenting) exhibits statistically ordered behavior.

Well-designed porous structured bimetallic ZnSe/CoSe₂/carbon composite nanofibers with uniformly distributed pores were prepared as anodes for sodium-ion batteries by electrospinning and subsequent simple heat-treatment processes. Size-controlled polystyrene (PS) nanobeads in the electrospinning solution played a key role in the formation and uniform distribution of pores in the nanofiber structure, after the removal of selected PS nanobeads during the heat-treatment process. The porous ZnSe/CoSe₂/C composite nanofibers were able to release severe mechanical stress/strain during discharge−charge cycles, introduce larger contact area between the active materials and the electrolyte, and provide more active sites during cycling. The discharge capacity of porous ZnSe/CoSe2/C composite nanofibers at the 10,000th cycle was 297 mA h g−1, and the capacity retention measured from the second cycle was 81%. The final rate capacities of porous ZnSe/CoSe2/C composite nanofibers were 438, 377, 367, 348, 335, 323, and 303 mA h g−1 at current densities of 0.1, 0.5, 1, 3, 5, 7, and 10 A g−1, respectively. At the higher current densities of 10, 20, and 30 A g−1, the final rate capacities were 310, 222, and 141 mA h g−1, respectively.

In recent years, nanowires have been shown to exhibit high photosensitivities, and, therefore are of interest in a variety of optoelectronic applications, for example, colour-sensitive photodetectors. In this study, we fabricated two-terminal PbS, In 2 S 3 , CdS and ZnSe single-nanowire photoresistor devices and tested applicability of these materials under the same conditions for colour-sensitive (405 nm, 532 nm and 660 nm) light detection. Nanowires were grown via atmospheric pressure chemical vapour transport method, their structure and morphology were characterized by scanning and transmission electron microscopy (SEM and TEM), X-ray diffraction (XRD), and optical properties were investigated with photoluminescence (PL) measurements. Single-nanowire photoresistors were fabricated via in situ nanomanipulations inside SEM, using focused ion beam (FIB) cutting and electron-beam-assisted platinum welding; their current-voltage characteristics and photoresponse values were measured. Applicability of the tested nanowire materials for colour-sensitive light detection is discussed. [ABSTRACT FROM AUTHOR]

The design, calibration and operation of a dual photoelastic modulator-based Fourier transform broadband Stokes polarimeter is presented. This instrument measures the full Stokes vector in the 2.5–11 m range in the mid-infrared. Analytical expressions for the wavelength-dependent terms affecting the determination of the four elements of the Stokes vector are provided, along with options for their practical solution. As an example, the dispersion of the birefringence of a quartz waveplate is measured. [ABSTRACT FROM PUBLISHER]

ZnSe nanoparticles are prepared by using chemical method in the occurrence of an optically transparent and semicrystalline polyvinyl alcohol polymer matrix. The prepared samples were characterised by different spectroscopic techniques like XRD, SEM with EDS, TEM, optical absorption, photoluminescence and FT-IR spectroscopic techniques. The average crystallite size was found to be 6 nm from the XRD pattern. The morphology of prepared sample was analysed by using SEM and TEM studies. Optical absorption spectrum exhibited the bands which were corresponds to pure ZnSe. Photoluminescence spectrum exhibits the emission band at 431 nm with the excitation wavelength of 350 nm. Functional groups of the prepared sample were observed in the FT-IR spectrum. [ABSTRACT FROM PUBLISHER]

Hydrothermal method was used to synthesize pure ZnSe nanosphere materials. The effects of the reducing agent amount, the reaction time and temperature were investigated on the purity of ZnSe. Also, the effects of surfactants such as sodium dodecyl sulfate (SDS) (anionic) and cetyl trimethylammonium bromide (CTAB) (cationic) were studied on the morphology of ZnSe. The prepared nanospheres were characterized using XRD, SEM, TEM and UV-Vis spectroscopy. Through these techniques, it was found that the pure ZnSe nanoparticles have a zinc blend structure and in a spherical form with average diameter of 30 nm. DOI: http://dx.doi.org/10.4314/bcse.v28i1.5

Charge recombination is an important factor that limits the cell efficiency of quantum dot sensitized solar cells (QDSSCs). Herein, we report a facile way to improve the cell performance of CdSe sensitized ZnO QDSSC by overcoating a thin layer of ZnSe on CdSe/ZnO film through a successive ionic layer adsorption and reaction (SILAR) procedure. Photovoltaic investigations indicate that ZnSe overcoating can increase photocurrent and photovoltage of the cell, resulting in significant enhancement of the cell efficiency, which is much better than the widely used traditional ZnS material. The superior role of ZnSe overcoating is ascribed to its large inhibition of charge recombination loss owing to its suitable band structure, efficient passivation of ZnO and CdSe QDs as well as its small lattice mismatch with CdSe that leads to the large decrease of surface/interface defects in CdSe/ZnO photoanode. This finding provides an alternative efficient way to enhance the cell performance of ZnO based QDSSC by suppressing the charge recombination. [ABSTRACT FROM AUTHOR]

Nanostructured ZnSe/ZnS multilayer thin films with excellent blue light emission were prepared using the electron beam evaporation technique. The structures and crystallization of the nanostructured ZnSe/ZnS multilayer thin films were studied by X-ray diffraction, which revealed a good crystallization with cubic structure of ZnSe and wurtzite structure of ZnS. The surface and inner morphologies of these films were analyzed by the Scanning Electron Microscopic and Transmission Electron Microscope, respectively. Optical transmission spectra were also investigated by UV–vis–NIR scanning spectrophotometer. Furthermore, the blue emission spectra of annealed films locating at about 440 nm were obtained, which corresponded to near band-edge emission of ZnSe. An obvious blue-shift of near band-edge emission was observed with annealing temperature increasing due to the quantum confinement effects. It is full of great potential for the nanostructured films to be used in optoelectronic devices based on outstanding blue luminescence performance. [ABSTRACT FROM AUTHOR]

In this work, a simple, effective, reproducible and green fabrication process for the production of high-quality, pure ZnSe nanoparticles at low temperature is presented. The structural and optical properties of these nanoparticles have been examined by transmission electron microscopy (TEM), energy dispersive X-ray analysis (EDX), Ultraviolet-Visible spectroscopy (UV–vis), photoluminescence (PL), and Raman spectroscopy. TEM analysis confirms that the formed products are ZnSe particles with size less than 10 nm, respectively. Strong blue shift absorption with energy band gap of 3.85 eV is observed from UV–vis spectrophotometry. Photoluminescence measurements showed that the nanoparticles exhibit a strong UV emission peak at 380 nm. The blue emission could be attributed to the quantum size effect of ZnSe nanocrystals. Raman spectroscopy of the ZnSe NPs showed a clear shift of transverse optical (TO) and longitudinal optical (LO) phonon modes, as well as a broadening of the LO phonon mode. [ABSTRACT FROM AUTHOR]

In this article, we report the design and performance of the ZnSe thin films sandwiched with 75 nm thick slab of indium as promising device for microwave resonating applications. The device is studied by X-ray diffraction, temperature dependent resistivity measurements and impedance spectroscopy in the frequency domain of 0.1-1.8 GHz. The X-ray analysis revealed a metal induced improvement in the crystallization process of the cubic phase of ZnSe. It is also observed that the nanosandwiching of the indium between two layers of ZnSe, significantly lowered the electrical resistivity by 17 times and improved the performance of the ZIZ when used as back to back Schottky device between an Au and carbon electrodes. The impedance spectroscopy analysis has shown that the resistance spectral variation controls the frequency domains of the device. The maximum cutoff frequency was achieved at 4.44 GHz when an input signal of biasing voltage of 0.1 V is dominated with frequency of 1.50 GHz. When the device was tested as microwave resonator it show band stop filter features of notch frequency of 1.0 GHz. [ABSTRACT FROM AUTHOR]

The Chemical Bath Deposition (CBD) technique was used to synthesise Zinc Selenide (ZnSe) thin films. To characterise ZnSe thin films for their structural, compositional, electronic and optical properties, XRD, SEM, EDX, optical absorbance and dielectric studies were conducted. To study the structure and crystallite size of ZnSe thin film, X-ray diffraction (XRD) analysis was used. By Scanning Electron Microscopic (SEM) and energy-dispersive X-ray analysis (EDX) studies, the surface morphology of these films was studied. Using UV–Visible absorption spectrum, the optical properties of the ZnSe thin films were determined. The optical band gap for a ZnSe thin film was found to be 2.8 eV. Photoluminescence emission peaks of the as-deposited ZnSe thin films were observed. At different frequencies and at room temperature for the prepared ZnSe thin films, the dielectric studies were carried out. [ABSTRACT FROM PUBLISHER]

ZnSe is one of the important and excellent II-VI semiconductor materials, which has direct transition band structure. In this paper, ZnSe thin films were prepared by an electrochemical deposition method, and the formation mechanism of ZnSe was studied systematically. Voltammetry and chronoamperometry combined with X-ray diffraction (XRD) and Raman techniques were used to analyze the deposition processes. It is found that the substrate and deposition potentials have a great influence on the phase composition of deposited thin film, and Zn substrate is beneficial to the preparation ZnSe films. Strong selenium-substrate interaction results in the formation of selenium compounds involving electrode materials. The addition of Zn(II) source can affect the reduction potential of Se, and results in the change of reducing mechanism of Se(0) from Se(IV). Se(0) formed from HSe because the formation of HSe is more active than forming Se(0) directly from Se(IV), and HSe can recombine with the substrate material, forming selenium-substrate compounds more quickly. [ABSTRACT FROM AUTHOR]

Multiple-shell ZnSe core-shell microspheres were synthesized on a large scale by a facile solvothermal method in ethylene glycol (EG) with ethylene diamine tetraacetic acid (EDTA) assisted. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV–vis absorption spectroscopy and photoluminescence (PL) were used to characterize the structures and optical properties of these core-shell spheres with multiple shells. XRD and SEM analyses show that the as-grown ZnSe samples are zinc-blende core-shell structures with multiple shells. The possible growth mechanism is investigated. The results of photocatalysis of methyl red (MR) indicate that the multiple-shell ZnSe core-shell microspheres possess remarkable photocatalytic activity. [ABSTRACT FROM AUTHOR]

ZnSe:Eu quantum dots (QDs) were synthesized using the heating-up method by adding a Eu precursor in Zn and Se precursors. The optical property was investigated based on the change in the multimodal emission caused by increasing the amount of the Eu precursor. The emission wavelength of ZnSe QDs increased from 398 nm to 405 nm when the reaction was carried out for 30–300 s. The broad spectrum was attributed to the 4 F 6 5 D 1 → 4 F 7 transition when the Eu 2+ emission was increased from 450 to 550 nm. Eu 3+ shows characteristic red emission peaks at 579, 592, 615, 651, and 700 nm owing to the electronic transition of 5 D 0 → 7 F j (j = 0, 1, 2, 3, 4). The expected structure of the ZnSe:Eu QDs was verified by XRD, TEM, and XPS. Compared to the diffraction peaks of pristine ZnSe, the corresponding peaks for the ZnSe:Eu QDs are shifted, by about 0.43°, to larger angles, because the ionic radius of Eu 3+ (0.95 Å) is larger than that of Zn 2+ (0.74 Å). They also have Eu 2+ O and Eu 3+ O dangling bonds on the surface of Eu 3+ -doped ZnSe QDs, with an average size of about 3.15 nm. These semiconductor QDs with rare earth elements are promising candidates to fabricate light-converting materials. [ABSTRACT FROM AUTHOR]

The various mole percent (1-5%) of Eu-doped ZnSe thin films were fabricated on the indium-doped tin oxide (ITO) conducting glass substrate by single-step electrochemical deposition (ECD) process in an aqueous medium at 50 °C. The structural, optical, magnetic, and electrochemical properties were characterized as a function of the Eu ion concentration. The X-ray diffraction (XRD) analyses evidenced that the films were hexagonal wurtzite structure along with the (101) preferential orientation. High-resolution scanning electron microscopy (HRSEM) results revealed that the thin films show a spherical like structure for 1-3% of Eu-doped ZnSe films. Further, increasing of Eu concentration (4 and 5%), the surface morphology of thin films was observed as agglomerated grain-like structure. The band gap energy of Eu-doped ZnSe thin films (2.35 to 2.49 eV) determined by UV-Vis spectra showed a blue shift of absorption edge compared to the pure ZnSe thin film (2.33 eV). The increased band gap by doping of Eu is due to the quantum size effect. The PL emission intensity enhanced by increasing Eu concentration which revealed the enhanced radiative recombination in the luminescence process. The magnetic study revealed that Eu-doped ZnSe thin films were ferromagnetic in nature. Electrochemical impedance analysis indicated that 4% of Eu-doped ZnSe thin films showed a lower charge transfer resistance (352 Ω) and excellent properties compared to the other samples. Further, the photoelectrochemical measurements carried out for the optimized 4% Eu-doped ZnSe thin film revealed the faster migration of photoinduced charge carriers. The present investigation demonstrates that the electrochemically deposited Eu-doped ZnSe thin film is a promising candidate for electrochemical device applications. [ABSTRACT FROM AUTHOR]

We report on the results of a numerical study of quantum transport in ZnSe-based resonant-tunneling diodes (RTDs) and quantum cascade oscillators (QCOs) with fixed and unequal barrier heights. It is found that the negative differential resistance exists up to room temperature in the current–voltage characteristics of the RTD and QCO devices with unequal barrier heights. Further, we demonstrate that QCOs with unequal barrier heights have a better frequency and power performance characteristics compared with RTDs and are more beneficial for high-power terahertz generation at room temperature. For the best QCO device with 100 periods of quantum cascading, a maximum output power of ~7–9 \mu \textW for the operating frequency range from 0.1 to ~6 THz at room temperature was achieved. [ABSTRACT FROM PUBLISHER]

We have obtained the Compton profile of ZnSe from the first principles GW approximation (GWA) method and ground-state density functional theory (DFT) method. We observe that between 0 and 1.5 a.u., there is better agreement to previous studies via the GWA difference profile compared to the ground-state difference profile. Above 1.5 a.u., both cases do not agree with the trend of the previous study; however, the application of the GWA is seen to improve the agreement compared to localized density approximation. Previous studies have reported that discrepancies from experiment are related to pseudopotential calculations which have been observed to overestimate momentum density between 0 and 1.5 a.u., while the reverse trend is seen above 1.5 a.u. We thus conclude that improvement to the pseudopotential technique to obtain the Compton profile is possible if the sharp Fermi break of the momentum distribution between high and low momenta becomes more smeared. Using the broadened spectral functions via the contour deformation method to obtain the momentum distributions, the GWA is a natural tool to achieve this via the contribution from the dielectric screening to the quasiparticle energies. [ABSTRACT FROM PUBLISHER]

The objective of this study is to explore the electrical and optical characterization of zinc selenide (ZnSe) and zinc sulfide (ZnS) semiconductors as cathode materials of an Infrared image converter. The experiments and simulations have been performed for various converter parameters such as pressure, breakdown voltage, interelectrode distance and illumination. The plasma system has been excited by a dc source, and gas discharge phenomena has been determined under a wide atmospheric pressure range, p. The findings show that ZnS and ZnSe have similar electronic behavior in the image converter in general. The measured discharge currents vary for the two cathodes. In the simulations, the electron mobility, thermal velocity, 3D electron density, space and surface charge density, and mean electron energy have been explored in the Ar-filled converter. It has been proven that the two semiconductors exhibit different properties of discharge, in particular, the mobility of electrons, the ionization coefficients, the breakdown voltages U , thermal velocities of electrons and surface charge densities. According to the experimental and theoretical findings, ZnSe shows better electrical and optical characteristics for the Ar-filled converter. [ABSTRACT FROM AUTHOR]

In this study, ZnSe and ZnSe:Cu quantum dots (QDs) were synthesized using Na2SeO3 as the Se source by a rapid and room temperature photochemical (UV-assisted) approach. Thioglycolic acid (TGA) was employed as the capping agent and UV illumination activated the chemical reactions. Synthesized QDs were successfully characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), photoluminescence (PL) and UV-visible (UV-vis) spectroscopy, Fourier transform-infrared (FT-IR), and energy dispersive X-ray spectroscopy (EDX). XRD analysis demonstrated the cubic zinc blend phase QDs. TEM images indicated that round-shaped particles were formed, most of which had a diameter of about 4 nm. The band gap of the ZnSe QDs was higher than that for ZnSe in bulk. PL spectra indicated an emission with three peaks related to the excitonic, surface trap states and deep level (DL) states. The band gap and QD emission were tunable only by UV illumination time during synthesis. ZnSe:Cu showed green emission due to transition of electrons from the Conduction band (CB) or surface trap states to the 2T2 acceptor levels of Cu2+. The emission was increased by increasing the Cu2+ ion concentration, such that the optimal value of PL intensity was obtained for the nominal mole ratio of Cu:Zn 1.5%. [ABSTRACT FROM AUTHOR]

ZnSe and Au nanoparticles co-sensitized TiO 2 nanotube arrays (ZnSe/Au/TiO 2 NTs) with wide light absorption were first successfully fabricated using two-step anodization, microwave-assisted chemical reduction and in situ deposition process. The investigation indicated that ZnSe and Au nanoparticles grew uniformly on the surface of TiO 2 NTs. The optic property of ZnSe/Au/TiO 2 NTs showed a stronger visible light absorption. Enhanced photocurrent (0.61 mA/cm 2 ) of the ZnSe/Au/TiO 2 NTs was observed due to the enhanced the photoelectric separation efficiency. Meanwhile, the photoelectrochemical measures clearly demonstrated that the ZnSe/Au/TiO 2 NTs had more efficient photoelectrochemical property than the TiO 2 NTs. Furthermore, ZnSe/Au/TiO 2 NTs also demonstrated the highest photoelectrocatalytic capability and stability during the photoelectrocatalytic degradation of MB, which was attributed to the synergistic effects between nanotubular structures of TiO 2 and uniformly dispersed ZnSe and Au nanoparticles, as well as the small bias potential. [ABSTRACT FROM AUTHOR]

We identified conditions for room-temperature operation of terahertz quantum cascade lasers (THz QCLs) where variable barrier heights are used on ZnSe/Zn1- xMg x Se material systems. The THz QCL devices are based on three-level two-well design schemes. The THz QCL lasers with alternating quantum barriers with different heights were compared with THz QCL laser structures with fixed quantum barrier heights. It is found that the THz QCL device with novel design employing variable barrier heights achieved the terahertz emission of about 1.45 THz at room-temperature (300 K), and has improved laser performance due to the suppression of thermally activated carrier leakage via higher-energy parasitic levels. Thus, THz QCL devices employing the design with variable barrier heights may lead to future improvements of the operating temperature and performance of THz QCL lasers. (© 2016 WILEY-VCH Verlag GmbH &Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]