Bilayer Deposition Research Articles

MICROSTRUCTURE, CHEMICAL COMPOSITION, AND NANOMECHANICAL PROPERTIES OF ARC-PVD ZrTa/ZrTaO2 BILAYER COATINGS

The results of vacuum-arc deposition of thin bilayer ZrTa/ZrTaO2 coatings on the surface of titanium dental implants, AISI-316L stainless steel are presented. The structure, phase and chemical composition of deposited coatings have been investigated by means of scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS) and X-ray diffraction analysis XRD. Nanomechanical properties have been investigated by nanoindentation method. The obtained results can be useful for optimization of implant surfaces to prevent corrosion and mechanical failure, thereby improving osseointegration.

Concerting magnesium implant degradation facilitates local chemotherapy in tumor-associated bone defect

Effective management of malignant tumor-induced bone defects remains challenging due to severe systemic side effects, substantial tumor recurrence, and long-lasting bone reconstruction post tumor resection. Magnesium and its alloys have recently emerged in clinics as orthopedics implantable metals but mostly restricted to mechanical devices. Here, by deposition of calcium-based bilayer coating on the surface, a Mg-based composite implant platform is developed with tailored degradation characteristics, simultaneously integrated with chemotherapeutic (Taxol) loading capacity. The delicate modulation of Mg degradation occurring in aqueous environment is observed to play dual roles, not only in eliciting desirable osteoinductivity, but allows for modification of tumor microenvironment (TME) owing to the continuous release of degradation products. Specifically, the sustainable H2 evolution and Ca2+ from the implant is distinguished to cooperate with local Taxol delivery to achieve superior antineoplastic activity through activating Cyt-c pathway to induce mitochondrial dysfunction, which in turn leads to significant tumor-growth inhibition in vivo. In addition, the local chemotherapeutic delivery of the implant minimizes toxicity and side effects, but markedly fosters osteogenesis and bone repair with appropriate structure degradation in rat femoral defect model. Taken together, a promising intraosseous administration strategy with biodegradable Mg-based implants to facilitate tumor-associated bone defect is proposed.

Polymer chain transport investigated using surface enhanced Raman spectroscopy: monitoring of diffusion kinetics on meso-structured plasmonic substrates.

We utilize the results of surface-enhanced Raman spectroscopy (SERS)-based interdiffusion experiments on meso-structured substrates to independently validate direct observations of plasmonic enhancements on these elements. The plasmonic enhancement function (PEF) is crucial for accurately determining interdiffusion coefficients using this newly proposed SERS-based methodology. The substrates feature a microscale inverted pyramid geometry, coated with nanoscale sputtered gold. Interdiffusion experiments involve the sequential deposition of polymer bilayers, with deuterated polystyrene (dPS) at the bottom and polystyrene (PS) on top, followed by annealing while periodically acquiring Raman spectra. The temporal evolution of the PS Raman signal reflects not only the interdiffusion process but also plasmonic effects, as the Raman scattering primarily arises from the substrate's plasmonic hotspots. High-resolution finite element (FE) diffusion simulations, combined with experimental SERS data, are used to infer the PEF of the substrate. The derived PEF is consistent with two hotspots located at the apex and vertices of the pyramidal cavity, extending along the edges and spreading into the molecular layer in direct contact with the substrate. This finding is tested against experiments conducted at various diffusion rates, showing excellent agreement. It corroborates recent observations by Steuwe et al. regarding the localization of hotspots on this specific substrate but contradicts other studies that attribute hotspots solely to the micron-scale geometry. This analysis establishes a solid foundation for reliably determining diffusion coefficients using this SERS-based methodology.

Thermoelectric Properties of Annealed Bilayer SnSe/PbTe and SnSe/PbSe Thin Films by Thermal Evaporation Method

Tin Selenide, Lead Selenide, and Lead Telluride are known best thermoelectric materials for mid and high-temperature electric generation applications. The bilayer of these materials could enhance the quality of a thermoelectric generation. The present work deals with bilayer deposition of SnSe/PbTe and SnSe/PbSe in glass substrates using physical vapor deposition followed by annealing at 323K, 423K, and 523K. The structure and morphology of the films have been investigated by XRD, SEM, and FESEM studies. The thermoelectric pursuance of both bilayer thin films was studied with the temperature as a function in the range of 300K to 623K. Both films exhibit the maximum Seebeck coefficient. The electrical Conductivity and Power factor increased gradually for SnSe/PbTe thin films and SnSe/PbSe thin films for the samples annealed up to 573K and then decreases. The electronic thermal conductivity of both films was very low compared to the total thermal conductivity. The absolute thermal conductivity at room temperature was calculated by Transient Hot Wire (THW) method. The maximum Figure of Merit (ZT) value obtained for SnSe/PbTe and SnSe/PbSe at room temperature was 0.81 and 1.3 for 573K annealed thin films respectively.

Enhancement of photoelectrochemical performance for nitrogen-doped titanium dioxide-based thin films produced by a facile air-based sputtering deposition

This work explores the use of air as a reactive gas in the sputtering deposition of N-doped TiO2-based bilayer, gradient, and multilayer thin films for photoelectrochemical evaluations. By merely adjusting the air/Ar flow ratio, crystalline phases, nitrogen doping contents, electrical properties, optical bandgaps, and valence band maximum (VBM) positions of N–TiO2 films were tailored. The N–TiO2/TiN(O) bilayer on the glass substrates exhibited a peak photocurrent density of 776 μA cm−2 at an air/Ar ratio of 1.60, which may be due to suitable bandgap and carrier mobility of the TiO2 overlayer as the bandgap was affected by the nitrogen content and rutile fraction in the TiO2 overlayer. To further improve the performance of N–TiO2, stepwise and sequential gradient structures with gradient bandgaps and nitrogen contents were produced, which could reach photocurrent densities of 805 ± 4 and 837 ± 3 μA cm−2, respectively. The gradient structures lead to enhanced light absorption efficiency and reduce carrier recombination. The N–TiO2/TiN(O) multilayer structures were also designed and revealed the highest photocurrent density of 865 ± 7 μA cm−2. Such evident enhancement is mainly due to the thin conductive while translucent TiN(O) layers between the photoelectrochemical-active N–TiO2 layers provide multiple low-impedance channels in enhancing carrier transport.

Electrochemical deposition of bilayer PPy/PPy-HA coating on AZ31 Mg alloy: Effect of HA content on characteristics and corrosion protection

This study aimed to examine the impact of naturally derived hydroxyapatite (HA) particles on the surface characteristics and corrosion behavior of polypyrrole (PPy)/polypyrrole-HA bilayer coatings. The coatings were applied onto AZ31 Mg alloy substrates using the potentiostatic electrodeposition method. Varying concentrations of HA particles (1, 3, and 5 wt%) were incorporated into the electrodeposition baths to create the top composite layers. Morphological analysis using FESEM revealed that the presence of HA particles led to PPy coatings with reduced porosity and more compact structures. EDS analysis and elemental mapping confirmed the presence of HA particles within the PPy matrix. AFM topography parameters indicated a slight increase in roughness values as the concentration of HA particles increased, with the average roughness rising from 46 nm for pure PPy coating to 53 nm for the coating with the highest HA content. Wettability results showed that the water contact angle (WCA) decreased from 56.6° for unreinforced PPy to 35.6° for the bilayer PPy/PPy-5 wt%HA coating. The corrosion behavior of the samples was investigated using potentiodynamic polarization and electrochemical impedance spectroscopy. It was observed that HA particles effectively reduced the corrosion current density (icorr), with the icorr of the optimal bilayer coating containing 3 wt% HA being 3.7 × 10−7 A cm−2, approximately two times lower than that of unreinforced PPy coating. Furthermore, the adhesion strength of the coatings was not affected by the inclusion of HA particles.

Modification of Cellulose Acetate Microfiltration Membranes Using Graphene Oxide-Polyethyleneimine for Enhanced Dye Rejection.

Pressure-based membrane processes represent excellent water resource recovery prospects from industrial waste streams. In contrast with conventional pretreatment technologies, studies have shown that membrane pretreatment applications, such as microfiltration (MF), are more cost-effective and improve the results of the overall treatment processes. Hence, enhancing rejection efficiency of MF will enhance the performance of any downstream treatment processes. In this study, 0.45 µm cellulose acetate (CA) microfiltration membranes were modified by vacuum filtration-assisted layer-by-layer deposition of bilayers composed of negatively charged graphene oxide (GO) and positively charged polyethyleneimine (PEI). The performance of 1-, 2-, and 4-bilayer GO-PEI-modified membranes were investigated for their dye-rejection of anionic eriochrome black T (EBT) dye and cationic methylene blue (MB) dye in a cross-flow membrane module. As the number of bilayers on the membrane increased, the membrane thicknesses increased, and the deionized (DI) water flux through the membranes decreased from 4877 LMH/bar for the control (no bilayer) membrane to 2890 LMH/bar for the 4-bilayer membrane. Conversely, the dye-rejection performance of the modified membranes increased as increasing bilayers of GO-PEI deposited on the membranes. The anionic EBT dye saw superior rejection (~90% rejection) compared to the cationic MB dye (~80% rejection), which can be attributable to the electrostatic repulsion between the negatively charged GO surface and anionic EBT dye. After 50% recovery of the saline and dye-laden feed water, there was an observed drop in DI water fluxes of ~40-41% and 36%, respectively. There was also a slight increase in EBT dye-rejection during the composite feed-water experiments, attributed to the precipitation of salts on the membrane feed side or pore spaces, which subsequently reduce the membrane pore sizes.

A lipid membrane supported on an artificial extracellular matrix made of polyelectrolyte multilayers: towards nanoarchitectonics at the cellular interface.

To implement a specific function, cells recognize multiple physical and chemical cues and exhibit molecular responses at their interfaces - the boundary regions between the cell lipid-based membrane and the surrounding extracellular matrix (ECM). Mimicking the cellular external microenvironment presents a big challenge in nanoarchitectonics due to the complexity of the ECM and lipid membrane fragility. This study reports an approach for the assembly of a lipid bilayer, mimicking the cellular membrane, placed on top of a polyelectrolyte multilayer cushion made of hyaluronic acid and poly-L-lysine - a nanostructured biomaterial, which represents a 3D artificial ECM. Model proteins, lysozyme and α-lactalbumin, (which have similar molecular masses but carry opposite net charges) have been employed as soluble signalling molecules to probe their interaction with these hybrids. The formation of a lipid bilayer and the intermolecular interactions in the hybrid structure are monitored using a quartz crystal microbalance and confocal fluorescence microscopy. Electrostatic interactions between poly-L-lysine and the externally added proteins govern the transport of proteins into the hybrid. Designed ECM-cell mimicking hybrids open up new avenues for modelling a broad range of cell membranes and ECM and their associated phenomena, which can be used as a tool for synthetic biology and drug screening.

Humidity-Responsive Polymer Cushion-Supported Biomimetic Membrane: A Model System for X-ray Studies.

An effort aimed at replacing the conventional water column by a relative humidity (RH) environment for structural investigation of a soft polymer cushion-supported model phospholipid membrane has been reported. An RH-responsive well-hydrated polymer cushion layer capable of approximately 2-fold swellability under RH 96% has been employed for phospholipid model membrane fabrication. To validate the proposed method, supported lipid bilayers (SLBs) of phosphocholine and phosphoethanolamine were deposited and structurally characterized at molecular level by the X-ray scattering method. In addition, the molecular interaction of the porphyrin-based hemin molecule, having a drug-like structure, with the supported membrane has been studied for further validation. The swelling behavior of the polymer cushion has been studied at a range of RH values prior to the bilayer deposition. The RH environment, in comparison to the conventional water column, enhanced the dynamic range approximately by 100-fold and the structural resolution by 2-fold. Thus, the bilayer structural features can be assessed without being overwhelmed by the background signals from the traditional water column. This facilitates in extracting reliable layer parameters and exogenous molecule-induced minute changes from the model fit. The proposed method will have far-reaching implications in biosensor engineering, protein-lipid, and drug-lipid interaction studies, X-ray microscopy, imaging, and photon correlation spectroscopy studies from SLBs where acquiring sufficient scattered intensity is still a challenge. This study also predicts that lab-based rotating-anode X-ray instruments can potentially be an alternative to the hard-access synchrotron experiments on biomimetic membranes, keeping the dynamic range and structural resolution uncompromised.

Photoabsorption Enhancement in Synthetic-Natural Dye-Sensitized Solar Cells Using Bilayer TiO2 Deposition and Separated Sensitization

In this study, a new methodology is proposed for the cosensitization of dye-sensitized solar cells by synthetic and natural dyes to increase their optical absorption. Synthetic dyes are efficient but expensive. In contrast, natural dyes are cheap but have a low adsorption rate in competition with synthetic dyes. Therefore, the conventional cosensitization method which is based on dye mixing prevents complete adsorption of natural dyes. In this work, a bilayer deposition of TiO2 and separated sensitization of each layer by one type of dye was performed. The N719 was used as a synthetic dye and betanin, crocin, acacetin, and indigo were used as natural dyes, which are extracted from plants inexpensively. The dyes were evaluated by UV-visible and FT-IR analyses. The results showed that a broad spectrum can be achieved due to different peaks in the photoabsorption spectra of these dyes. The bottom layer was sensitized by natural dyes while the top layer was sensitized by N719. Due to the effect of temperature on dyes, a low-temperature method based on acid-assistant sintering has been used for the top layer. The results of XRD and FESEM analyses indicated that a layer with proper crystalline phase, acceptable morphology, and good porosity can be achieved in the low-temperature process by tunning the acid concentration. The electrical properties of the fabricated solar cells were investigated by EIS analysis and J-V characteristics. The results showed that charge injection and transportation were improved via the ability of the proposed approach in separated dye adsorption. An efficiency of 3.48% was provided by the proposed method which demonstrates its better performance in comparison with the cocktail and sequential methods that showed efficiencies of 1.88% and 2.29%, respectively. The results indicated that separated sensitization of each layer can improve the dye loading leading to spectral expansion.

HfO2:Y2O3 ultrathin nanolaminate structures grown by ALD: Bilayer thickness and annealing temperature effects on optical properties

–Ultrathin nanolaminate structures were prepared by sequential HfO2:Y2O3 (HY) bilayer deposition at 250 °C on n-type (100) silicon wafers via thermal atomic layer deposition (ALD) method. Three sets of four samples were prepared, each sample with a total thickness of the nanolaminate of 54.5 ± 0.8 nm. The nominal thicknesses of the HY bilayers of the four samples were 0.5:0.5 nm, 1:1 nm, 2:2 nm, and 5:5 nm After the deposition, two of the sets were annealed in N2 atmosphere for 1 h at 500 °C and 750 °C, respectively. The third set was used as control samples. The optical behavior of the ultrathin nanolaminate structures was studied as a function of the HY bilayer thickness and annealing temperature. The thickness and optical parameters were analyzed via spectroscopic ellipsometry to gain information about the optical constants and bandgap values. An increase of the refractive index was found when the HY bilayer thickness decreased from 5:5 nm to 0.5:0.5 nm for both annealing temperatures as well as for the as-deposited sample, while the optical bandgap varied between 3.8 eV and 4.5 eV. The obtained results demonstrate the viability of HY ultrathin nanolaminate structures as a dielectric material for application in electronic and/or optoelectronic devices. Furthermore, the optical properties dependence on the bilayer thickness and annealing temperature could offer the possibility to design, fabricate, and improve samples with tunable optical properties at the nanoscale.

Fabrication, characterisation and application of Poly Allyl Amine Hydrochloride / Poly Styrene Sulphonate/Zinc Oxide (PAH/(PSS/ZnO)n bilayers in the removal of pollutants from oil refinery waste water

ABSTRACT The application of nanomaterials in the oil and gas industry has been widely studied in the past few years, and polymeric nano thin films have become an area of interest among researchers. In this work, multilayer nano thin films were fabricated using poly(ally lamine hydrochloride) (PAH), zinc oxide (ZnO) and poly(styrene sulphonate sodium salt) (PSS) on glass template by Layer-by-Layer (L-b-L) technique and its potential application for the photo degradation of oil refinery wastewater have been reported. The L-b-L fabrication of the thin film was carried out at an assembly pH of 8.0. The morphological characterisation and elemental composition of the fabricated thin films were studied using Scanning Electron Microscope (SEM) and Energy Dispersive X-Ray Analysis (SEM – EDX). Chemical bond and surface functional groups were identified using Fourier Transform Infrared Spectroscopy (FTIR). SEM characterisation depicted the uniform deposition of ZnO particles in the polyelectrolyte matrix. The outcome of the FTIR analysis is justified by the presence of strong C=C bonds favouring the strength of bilayer deposition. A comparative study on the degradation efficiency was carried out using oil refinery effluents for the photo degradation of ZnO/PSS/PAH thin films and suspension form of ZnO by varying the process parameters such as number of bilayers and contact time. The ZnO/Polyelectrolyte multilayer thin films performed extremely well in reducing the chemical oxygen demand (COD) and Total Organic carbon (TOC) to the standards. A maximum COD removal efficiency of 80.1% was obtained at conditions where PAH/(PSS, ZnO)5 bilayers were used at pH 7.2 with a contact time of 120 minutes. The total organic carbon removal was around 55% under optimum conditions of pH 7.2 and PAH/(PSS, ZnO)5 at 120 minutes. This study illustrates that immobilised zinc oxide nanoparticles can effectively remove pollutants from oily wastewater and the process seems to be attractive in the environmental applications.

Front Cover: Manufacture of Multilayered Artificial Cell Membranes through Sequential Bilayer Deposition on Emulsion Templates (ChemBioChem 13/2021)

Front Cover: Manufacture of Multilayered Artificial Cell Membranes through Sequential Bilayer Deposition on Emulsion Templates (ChemBioChem 13/2021)

Manufacture of Multilayered Artificial Cell Membranes through Sequential Bilayer Deposition on Emulsion Templates.

Efforts to manufacture artificial cells that replicate the architectures, processes and behaviours of biological cells are rapidly increasing. Perhaps the most commonly reconstructed cellular structure is the membrane, through the use of unilamellar vesicles as models. However, many cellular membranes, including bacterial double membranes, nuclear envelopes, and organelle membranes, are multilamellar. Due to a lack of technologies available for their controlled construction, multilayered membranes are not part of the repertoire of cell‐mimetic motifs used in bottom‐up synthetic biology. To address this, we developed emulsion‐based technologies that allow cell‐sized multilayered vesicles to be produced layer‐by‐layer, with compositional control over each layer, thus enabling studies that would otherwise remain inaccessible. We discovered that bending rigidities scale with the number of layers and demonstrate inter‐bilayer registration between coexisting liquid–liquid domains. These technologies will contribute to the exploitation of multilayered membrane structures, paving the way for incorporating protein complexes that span multiple bilayers.

Excess Heat Capacity in Mo/Au Transition Edge Sensor Bolometric Detectors.

Excess heat capacity in a bolometric detector has the consequence of increasing or leading to multiple device time constants. The Mo/Au bilayer transition edge sensor (TES) bolometric detectors initially fabricated for the high resolution mid-infrared spectrometer (HIRMES) exhibited two response thermalization scales, one of which is a few times longer than estimates based upon the properties of the bulk materials employed in the design. The relative contribution of this settling time to the overall time response of the detectors is roughly proportional to the pixel area, which ranges between ~0.3 and 2.6 mm2. Use of laser ablation to remove sections of the silicon membranes comprising the pixels results in a detector response with a smaller contribution from the secondary time constant. Additional information about the nature of this excess heat capacity is gleaned from glancing incidence x-ray diffraction, which reveals the presence of molybdenum silicides near the silicon surface which is a consequence of the bi-layer deposition. Quantitative analysis of the concentration of excess molybdenum, estimated with secondary ion mass spectroscopy, is commensurate to the additional heat capacity needed to explain the anomalous time response of the detectors.

A quantitative determination of lipid bilayer deposition efficiency using AFM.

The efficacy of a number of different methods for depositing a dimyristoylphosphatidylcholine (DMPC) lipid bilayer or DMPC–cholesterol (3 : 1) mixed bilayer onto a silicon substrate has been investigated in a quantitative manner using atomic force microscopy (AFM) image analysis to extract surface coverage. Complementary AFM-IR measurements were used to confirm the presence of the lipids. For the Langmuir–Blodgett/Schaefer deposition method at temperatures below the chain-melting transition temperature (Tm), a large number of bilayer defects resulted when DMPC was deposited from a water subphase. Addition of calcium ions to the trough led to smaller, more frequent defects, whereas addition of cholesterol to the lipid mixture led to a vast improvement in bilayer coverage. Poor coverage was achieved for deposition at temperatures above Tm. Formation of the deposited bilayer from vesicle fusion proved a more reliable method for all systems, with formation of near-complete bilayers within 60 seconds at temperatures above Tm, although this method led to a higher probability of multilayer formation and rougher bilayer surfaces.

Multilayer and Surface Immobilization of EDOT-Decorated Nanocapsules.

To assess the feasibility of utilizing reagent-loaded, porous polymeric nanocapsules (NCs) for chemical and biochemical sensor design, the surfaces of the NCs were decorated with 3,4-ethylenedioxythiophene (EDOT) moieties. The pores in the capsule wall allow unhindered bidirectional diffusion of molecules smaller than the programmed pore sizes, while larger molecules are either entrapped inside or blocked from entering the interior of the nanocapsules. Here, we investigate two electrochemical deposition methods to covalently attach acrylate-based porous nanocapsules with 3,4-ethylenedioxythiophene moieties on the nanocapsule surface, i.e., EDOT-decorated NCs to the surface of an existing PEDOT film: (1) galvanostatic or bilayer deposition with supporting EDOT in the deposition solution and (2) potentiostatic deposition without supporting EDOT in the deposition solution. The distribution of the covalently attached NCs in the PEDOT films was studied by variable angle FTIR-ATR and XPS depth profiling. The galvanostatic deposition of EDOT-decorated NCs over an existing PEDOT (tetrakis(pentafluorophenyl)borate) [PEDOT(TPFPhB)] film resulted in a bilayer structure, with an interface between the NC-free and NC-loaded layers, that could be traced with variable angle FTIR-ATR measurements. In contrast, the FTIR-ATR and XPS analyses of the films deposited potentiostatically from a solution without EDOT and containing only the EDOT-decorated NCs showed small amounts of NCs in the entire cross section of the films.

Controlled synthesis of Fe–Pt nanoalloys using atomic layer deposition

We report the phase and size-controlled synthesis of Fe–Pt nanoalloys, prepared via a two-step synthesis procedure. The first step is the deposition of bilayers consisting of iron oxide and Pt films of desired thicknesses using atomic layer deposition, followed by a temperature-programmed reduction treatment of the film under H2/N2 atmosphere. This method enables the phase pure synthesis of all three Fe–Pt alloy phases, namely Fe3Pt, FePt, and FePt3, as revealed by in situ x-ray diffraction and x-ray fluorescence measurements. It is also demonstrated that by changing the total thickness of the bilayers while keeping the Pt/(Pt + Fe) atomic ratio constant, the size of the resulting bimetallic nanoparticles can be tuned, as confirmed by scanning electron microscopic measurements.

Facile catalyst deposition using mists for fluidized-bed production of sub-millimeter-long carbon nanotubes

We developed a facile mist deposition method that yields nanometer-thick catalyst films on ceramic beads using aqueous solution of metal nitrates as a low cost catalyst precursor through two different strategies: (a) using a monolayer of a mixture of Fe(NO3)3 and Al(NO3)3 (Fe + Al) and (b) using a bilayer of Fe(NO3)3 on top of the mixture of Fe(NO3)3 and Al(NO3)3 (Fe/(Fe + Al)). In the fluidized bed, the catalyst precursor films were converted into Fe nanoparticles on an AlOx layer by thermal annealing and CNTs were synthesized by chemical vapor deposition. The yield and specific surface area of the resulting CNTs were strongly influenced by the deposition methods. The bilayer deposition strategy showed an improved controllability in acquiring small catalyst particles at a high density, which obtained high yields of CNTs with large specific surface area. As a result, CNTs of 7.5 nm in diameter, triple-wall on average, and 0.6 mm in length were synthesized by employing the fluidized bed chemical vaper deposition technique, suggesting a new way for the high-yield production of long few-wall CNTs at reasonable cost.

Hydrazine-free chemical bath deposition of WSe2 thin films and bi-layers for photovoltaic applications

We report the photovoltaic performance of a diode based on a p-type tungsten diselenide (WSe2) active region. The device is formed by WSe2 and cadmium sulfide (CdS) layers, both obtained via chemical bath deposition. A novel hydrazine-free chemical formulation allows deposition of WSe2 on glass and flexible Hastelloy substrates. Characterization of WSe2 via Raman spectroscopy shows four bands at 189, 244, 293, and 588 cm−1. The strongest band at 293 cm−1 is assigned to the interlayer interaction mode of the WSe2 layers. The photoluminescent characterization of Hastelloy/CdS/WSe2 samples exhibits two excitonic transitions at 1.7860 and 1.7899 eV. The current density-voltage (J-V) measurements of the CdS/WSe2 structure show a photovoltaic response with VOC = 180 mV, JSC = 0.07 mA cm−2, and FF = 0.22.