Phase-Controlled Multi-Dimensional-Structure SnS/SnS2/CdS Nanocomposite for Development of Solar-Driven Hydrogen Evolution Photocatalyst.

The quest for water-splitting photocatalysts to generate hydrogen as a clean energy source from two-dimensional (2D) materials has enormous implications for sustainable energy solutions. Photocatalytic water splitting, a major field of interest, is focused on the efficient production of hydrogen from renewable resources such as water using 2D materials. Tin sulfide and tin disulfide, collectively known as SnS and SnS2, respectively, are metal sulfide compounds that have gained attention for their photocatalytic properties. Their unique electronic structures and morphological characteristics make them promising candidates for harnessing solar energy for environmental and energy-related purposes. CdS/SnS/SnS2 photocatalysts with two Sn phases (II and IV) were synthesized using a solvothermal method in this study. CdS was successfully placed on a broad SnS/SnS2 plane after a series of characterizations. We found that it is composited in the same way as a core-shell shape. When the SnS/SnS2 phase ratio was dominated by SnS and the structure was composited with CdS, the degradation efficiency was optimal. This material demonstrated high photocatalytic hydrogenation efficiency as well as efficient photocatalytic removal of Cr(VI) over 120 min. Because of the broad light absorption of CdS, the specific surface area, which is the reaction site, became very large. Second, it served as a transport medium for electron transfer from the conduction band (CB) of the SnS to the CB of the SnS2. Because of the composite, these electrons flowed into the CB of CdS, improving the separation efficiency of the photogenerated carriers even further. This material, which was easily composited, also effectively prevented mineral corrosion, which is a major issue with CdS.

One-Step Synthesis of Transition Metal Dichalcogenide Quantum Dots Using Only Alcohol Solvents for Indoor-Light Photocatalytic Antibacterial Activity.

In this study, we report a one-step direct synthesis of molybdenum disulfide (MoS2) and tungsten disulfide (WS2) quantum dots (QDs) through a solvothermal reaction using only alcohol solvents and efficient Escherichia coli (E. coli) decompositions as photocatalytic antibacterial agents under visible light irradiation. The solvothermal reaction gives the scission of molybdenum-sulfur (Mo-S) and tungsten-sulfur (W-S) bonding during the synthesis of MoS2 and WS2 QDs. Using only alcohol solvent does not require a residue purification process necessary for metal intercalation. As the number of the CH3 groups of alcohol solvents among ethyl, isopropyl, and tert(t)-butyl alcohols increases, the dispersibility of MoS2/WS2 increases. The CH3 groups of alcohols minimize the surface energy, leading to the effective exfoliation and disintegration of the bulk under heat and pressure. The bulky t-butyl alcohol with the highest number of methyl groups shows the highest exfoliation and yield. MoS2 QDs with a lateral size of about 2.5 nm and WS2 QDs of about 10 nm are prepared, exhibiting a strong blue luminescence under 365 nm ultraviolet (UV) light irradiation. Their heights are 0.68-3 and 0.72-5 nm, corresponding to a few layers of MoS2 and WS2, respectively. They offer a highly efficient performance in sterilizing E. coli as the visible-light-driven photocatalyst.

P=O Functionalized Black Phosphorus/1T-WS2 Nanocomposite High Efficiency Hybrid Photocatalyst for Air/Water Pollutant Degradation.

Research on layered two-dimensional (2D) materials is at the forefront of material science. Because 2D materialshave variousplate shapes, there is a great deal of research on the layer-by-layer-type junction structure. In this study, we designed a composite catalyst with a dimension lower than two dimensions and with catalysts that canbe combined so that the band structures can be designed to suit various applications and cover for each other's disadvantages. Among transition metal dichalcogenides, 1T-WS2 can be a promising catalytic material because of its unique electrical properties. Black phosphorus with properly controlled surface oxidation can act as a redox functional group. We synthesized black phosphorus that was properly surface oxidized by oxygen plasma treatment and made a catalyst for water quality improvement through composite with 1T-WS2. This photocatalytic activity was highly efficient such that the reaction rate constant k was 10.31 × 10-2 min-1. In addition, a high-concentration methylene blue solution (20 ppm) was rapidly decomposed after more than 10 cycles and showed photo stability. Designing and fabricating bandgap energy-matching nanocomposite photocatalysts could provide a fundamental direction in solving the future's clean energy problem.

A high-efficiency and stable perovskite solar cell fabricated in ambient air using a polyaniline passivation layer.

Over the past number of years, the power conversion efficiency of perovskite solar cells has remained at 25.5%, reflecting a respectable result for the general incorporation of organometallic trihalide perovskite solar cells. However, perovskite solar cells still suffer from long-term stability issues. Perovskite decomposes upon exposure to moisture, thermal, and UV-A light. Studies related to this context have remained ongoing. Recently, research was mainly conducted on the stability of perovskite against non-radiative recombination. This study improved a critical instability in perovskite solar cells arising from non-radiative recombination and UV-A light using a passivation layer. The passivation layer comprised a polyaniline (PANI) polymer as an interfacial modifier inserted between the active layer and the electron transport layer. Accordingly, the UV-A light did not reach the active layer and confined the Pb2+ ions at PANI passivation layer. This study optimized the perovskite solar cells by controlling the concentration, thickness and drying conditions of the PANI passivation layer. As a result, the efficiency of the perovskite solar cell was achieved 15.1% and showed over 84% maintain in efficiency in the ambient air for one month using the 65 nm PANI passivation layer.

Nitrogen-Bearing Carbon Nanoparticles by Pyrolytic Decomposition of Piperazine Citrate Macromolecules for Cellular Imaging.

In this work, highly photoluminescent carbon nanoparticles (CNPs) are fabricated by pyrolytic decomposition of piperazine citrate at high pressure and high temperature. Piperazine serves as a hydrolytic, surface-passivating, and N-doping agent, facilitating the formation of a photopolymer. The as-synthesized CNPs, without any surface protection/passivation, exhibit excellent photolumi-nescence and a maximum quantum yield of 84%. The average particle size of the N-doped CNPs is 0.89±0.05 nm. In addition, the N-doped CNPs exhibit uniform diameters and nearly spherical shapes. The X-ray photoelectron spectroscopy results reveal that the CNPs are composed of carbon (64.4 wt%), oxygen (18.5 wt%), and nitrogen (17.1 wt%), indicating the presence of nitrogen-doped and carbon-rich moieties in the CNPs. Notably, the CNPs purified by the procedure developed in this work exhibit more stable luminescence properties than those purified with the conventional dialysis membrane. In addition, the potential application of the CNPs as fluorescent bioimaging probes, which offer a broad dosing window and exhibit multicolor emission, is investigated by directly cultur-ing A549 cells with the CNPs. The results reveal that the CNPs exhibit not only exceptional optical stability, but also outstanding biocompatibility and cell labeling capability. After incubating the A549 cells with CNPs, the CNPs are confined in perinuclear vacuole-similar shapes with a granulated form in cytoplasm preserving the nucleus. Notably, no significant morphological deterioration such as nuclear contraction is detected.

Black phosphorus @ molybdenum disulfide 2D nanocomposite with broad light absorption and high stability for methylene blue decomposition photocatalyst.

Recently, black phosphorus (BP) has become an increasingly popular two-dimensional material with application in many fields. In the field of photocatalyst, the substance is attracted by a wide spectrum and abundant constituents. BP is an attractive material with unique properties owing to its anisotropic structure, which is favorable for catalyst design as a result of bandgap change based on thickness. However, it has proved problematic in the photocatalyst field, due to rapid recombination of electrons and holes. As a result, to overcome this, we used a complex with MoS2 to prevent the recombination of electrons and holes and to have a broad range of optical absorption from visible light to NIR. MoS2 nanoflakes are a two-dimensional (2D) material of the transition metal dichalcogenide family, the advantage of which is that it can be used as a nano-junction between 2D materials. The nanocomposite material of BP and MoS2 shows a remarkable increase in photocatalytic decomposition ability of methylene blue which is an organic dye. It also has many cycles of catalytic ability, which is advantageous in terms of stability. There are expectations that MoS2 @ BP photocatalysts will be widely applied as a non-precious metal photocatalyst with broad light absorption spectra and multi-function photocatalytic materials.

Optical Sensing Properties of ZnO Nanoparticles Prepared by Spray Pyrolysis.

We studied the optical sensing properties of ZnO nanoparticles prepared by spray pyrolysis. To investigate their optical sensing performance, we incubated peptides on ZnO nanoparticles. The photoluminescence (PL) peak intensity of peptides on the ZnO nanoparticles was higher than that of peptides on the ZnO film or on the glass plate. This observed PL enhancement is attributed to the optical confinement of ZnO nanoparticles. The low-temperature spectra displayed a strong exciton emission peak with multiple sidebands, attributed to the bound exciton and its longitudinal optical phonon sidebands. The strong exciton emission is thought to be the combined effect of optical confinement due to the nanoparticle geometry, reduction of defect emission by thermal annealing, and reduction of non-radiative relaxation at low temperatures.

Improved Electrochromic Characteristics of a Honeycomb-Structured Film Composed of NiO.

Color changes controlled by electronic energies have been studied for many years in order to fabricate energy-efficient smart windows. Reduction and oxidization of nickel oxide under the appropriate voltage can change the color of a window. For a superior nickel oxide (NiO) electrochromic device (ECD), it is important to control the chemical and physical characteristics of the surface. In this study, we applied polystyrene bead templates to nickel oxide films to fabricate a honeycomb-structured electrochromic (EC) layer. We synthesized uniform polystyrene beads using the chemical wet method and placed them on substrates to create honeycomb-structured NiO films. Then, the EC characteristics of the nickel oxide films with a honeycomb structure were evaluated with UV-Visible and cyclic voltammetry. FE-SEM and AFM were used to measure the morphologies of the nanostructures and the efficiencies of the redox reactions related to the specific surface area.

Photocatalytic Degradation Effect of µ-Dielectric Barrier Discharge Plasma Treated Titanium Dioxide Nanoparticles on Environmental Contaminant.

This study focused on the photocatalytic degradation effect of the µ-dielectric barrier discharge (µ-DBD) plasma treated titanium dioxide (TiO2) nanoparticles on environmental contaminant such as formaldehyde. TiO2 nanoparticles were treated by a µ-DBD plasma source with nitrogen gas. We analyzed the degradation of formaldehyde with the plasma treated TiO2 nanoparticles by UV-visible spectrophotometer (UV-VIS), and demonstrated that the photocatalytic activity of the µ-DBD plasma-treated TiO2 nanoparticles showed significantly high catalytic efficiency rather than without plasma treated TiO2 nanoparticles. Field emission scanning electron microscopes (FE-SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and water contact angle analyzer were used to measure the effects of photocatalytic degradation for the plasma treated TiO2 nanoparticles.

Improvement of Charge Transportation in Si Quantum Dot-Sensitized Solar Cells Using Vanadium Doped TiO2.

The multiple exciton generation characteristics of quantum dots have been expected to enhance the performance of photochemical solar cells. In previous work, we first introduced Si quantum dot for sensitized solar cells. The Si quantum dots were fabricated by multi-hollow discharge plasma chemical vapor deposition, and were characterized optically and morphologically. The Si quantum dot-sensitized solar cells had poor performance due to significant electron loss by charge recombination. Although the large Si particle size resulted in the exposure of a large TiO2 surface area, there was a limit to ho much the particle size could be decreased due to the reduced absorbance of small particles. Therefore, this work focused on decreasing the internal impedance to improve charge transfer. TiO2 was electronically modified by doping with vanadium, which can improve electron transfer in the TiO2 network, and which is stable in the redox electrolyte. Photogenerated electrons can more easily arrive at the conductive electrode due to the decreased internal impedance. The dark photovoltaic properties confirmed the reduction of charge recombination, and the photon-to-current conversion efficiency reflected the improved electron transfer. Impedance analysis confirmed a decrease in internal impedance and an increased electron lifetime. Consequently, these improvements by vanadium doping enhanced the overall performance of Si quantum dot-sensitized solar cells.

Method for Fabricating Textured High-Haze ZnO:Al Transparent Conduction Oxide Films on Chemically Etched Glass Substrates.

We developed a technique for forming textured aluminum-doped zinc oxide (ZnO:Al) transparent conductive oxide (TCO) films on glass substrates, which were etched using a mixture of hydrofluoric (HF) and hydrochloric (HCl) acids. The etching depth and surface roughness increased with an increase in the HF content and the etching time. The HF-based residues produced insoluble hexafluorosilicate anion- and oxide impurity-based semipermeable films, which reduced the etching rate. Using a small amount of HCl dissolved the Ca compounds, helping to fragment the semipermeable film. This formed random, complex structures on the glass substrates. The angled deposition of three layers of ZnO:Al led to the synthesis of multiscaled ZnO:Al textures on the glass substrates. The proposed approach resulted in textured ZnO:Al TCO films that exhibited high transmittance (-80%) and high haze (> 40%) values over wavelengths of 400-1000 nm, as well as low sheet resistances (< 18 Ω/sq)..Si tandem solar cells based on the ZnO:Al textured TCO films exhibited photocurrents and cell efficiencies that were 40% higher than those of cells with conventional TCO films.

Influence of Heat Treatment Conditions on the Properties of Vanadium Oxide Thin Films for Thermochromic Applications.

In present work, the effects of the heat treatment on the structural, optical, and thermochromic properties of vanadium oxide films were investigated. Vanadium dioxide (VO2) thin films were deposited on glass substrate by reactive pulsed DC magnetron sputtering from a vanadium metal target in mixture atmosphere of argon and oxygen gas. Various heat treatment conditions were applied in order to evaluate their influence on the crystal phases formed, surface morphology, and optical properties. The films were characterized by an X-ray diffraction (XRD) in order to investigate the crystal structure and identify the phase change as post-annealing temperature of 500-600 degrees C for 5 minutes. Surface conditions of the obtained VO2(M) films were analyzed by field emission scanning electron microscopy (FE-SEM) and the semiconductor-metal transition (SMT) characteristics of the VO2 films were evaluate by optical spectrophotometry in the UV-VIS-NIR, controlling temperature of the films.

Patterning ITO by Template-Assisted Colloidal-Lithography for Enhancing Power Conversion Efficiency in Organic Photovoltaic.

Highly structured interfaces are very desirable in organic photovoltaic solar cells (OPVs), in order to enhance power conversion efficiency (PCE) by decreasing of the transport path for excited charge carriers in the absorber and increasing the optical path length for photon absorption. Many complicated, high-cost lithographic methods have been attempted to modify the surface of the absorber or substrate. However, solution-based colloidal-lithography processes are scalable and cost-effective, but generally result in non-uniform structured surfaces. In this report, we demonstrated an optimized silica-templated colloidal lithographical approach to create a well-defined and controlled transparent ITO layer for enhancing power conversion efficiency (PCE). Additionally, morphological effects of the patterned ITO on optical properties and PCE were analyzed in detail.

Enhanced Visible Transmittance of Thermochromic VO2 Thin Films by SiO2 Passivation Layer and Their Optical Characterization.

This paper presents the preparation of high-quality vanadium dioxide (VO2) thermochromic thin films with enhanced visible transmittance (Tvis) via radio frequency (RF) sputtering and plasma enhanced chemical vapor deposition (PECVD). VO2 thin films with high Tvis and excellent optical switching efficiency (Eos) were successfully prepared by employing SiO2 as a passivation layer. After SiO2 deposition, the roughness of the films was decreased 2-fold and a denser structure was formed. These morphological changes corresponded to the results of optical characterization including the haze, reflectance and absorption spectra. In spite of SiO2 coating, the phase transition temperature (Tc) of the prepared films was not affected. Compared with pristine VO2, the total layer thickness after SiO2 coating was 160 nm, which is an increase of 80 nm. Despite the thickness change, the VO2 thin films showed a higher Tvis value (λ 650 nm, 58%) compared with the pristine samples (λ 650 nm, 43%). This enhancement of Tvis while maintaining high Eos is meaningful for VO2-based smart window applications.

Patterned Well-Aligned ZnO Nanorods Assisted with Polystyrene Monolayer by Oxygen Plasma Treatment.

Zinc oxide is known as a promising material for sensing devices due to its piezoelectric properties. In particular, the alignment of ZnO nanostructures into ordered nanoarrays is expected to improve the device sensitivity due to the large surface area which can be utilized to capture significant quantities of gas particles. However, ZnO nanorods are difficult to grow on the quartz substrate with well-ordered shape. So, we investigated nanostructures by adjusting the interval distance of the arranged ZnO nanorods using polystyrene (PS) spheres of various sizes (800 nm, 1300 nm and 1600 nm). In addition, oxygen plasma treatment was used to specify the nucleation site of round, patterned ZnO nanorod growth. Therefore, ZnO nanorods were grown on a quartz substrate with a patterned polystyrene monolayer by the hydrothermal method after oxygen plasma treatment. The obtained ZnO nanostructures were characterized by X-ray diffraction (XRD) and field-emission scanning electron microscope (FE-SEM).

Flow Manipulation in Thread-Based Microfluidics by Tuning the Wettability of Wool.

Recent progress in thread-based microfluidic devices has provided portable and inexpensive field-based technologies enabling medical diagnostics, environmental monitoring, and food safety analysis. However, capillary-driven liquid flow in a single thread, a crucial aspect of thread-based microfluidics, is difficult to control. Among potential materials, hydrophobic wool thread is an appropriate candidate for liquid flow control in thread-based microfluidics because its wettability can be readily tuned by the introduction of a natural color pigment, thereby manipulating flow. Thus, utilizing natural wool thread as a channel, we demonstrate here that liquid flow manipulations, such as microselecting and micromixing, can be achieved by coating the complex Al(III) (Alum) brazilein onto wool thread. In addition to enabling flow control, the coated wool channels consisting entirely of naturally occurring substances will be beneficial for biological sensing devices.

Micropatterning of TiO2 thin films by MOCVD and study of their growth tendency.

In this work, we studied the growth tendency of TiO2 thin films deposited on a narrow-stripe area (<10 µm). TiO2 thin films were selectively deposited on OTS patterned Si(100) substrates by MOCVD. The experimental data showed that the film growth tendency was divided into two behaviors above and below a line patterning width of 4 µm. The relationship between the film thickness and the deposited area was obtained as a function of f(x) = a[1 - e((-bx))]c. To find the tendency of the deposition rate of the TiO2 thin films onto the various linewidth areas, the relationship between the thickness of the TiO2 thin film and deposited linewidth was also studied. The thickness of the deposited TiO2 films was measured from the alpha-step profile analyses and cross-sectional SEM images. At the same time, a computer simulation was carried out to reveal the relationship between the TiO2 film thickness and deposited line width. The theoretical results suggest that the mass (velocity) flux in flow direction is directly affected to the film thickness.

Angiogenic tube formation of bovine aortic endothelial cells grown on patterns formed by H2/He plasma treatment of the plasma polymerized hexamethyldisiloxane film.

Angiogenesis, the process to generate new vessels, is necessary for normal development in children as well as the wound healing and the tumor growth in adults. Therefore, it is physiologically and/or pathophysiologically significant to monitor angiogenesis. However, classical in vitro methods to evaluate angiogenesis take a long time and are expensive. Here, the authors developed a novel method to analyze the angiogenesis in a simple and economical way, using patterned films. In this study, the authors fabricated a plasma polymerized hexamethyldisiloxane (PPHMDSO) thin film deposited by capacitively coupled plasma chemical vapor deposition system with various plasma powers. The patterned PPHMDSO film was plasma treated by 10:90 H2/He mixture gas through a metal shadow mask. The films were characterized by water contact angle, atomic force microscopy, x-ray photoelectron spectroscopy, and Fourier-transform infrared spectroscopy analyses. Our results show that the PPHMDSO film suppresses the cell adhesion, whereas surface modified PPHMDSO film enhances the cell adhesion and proliferation. From cell culture experiments, the authors found that the patterned film with 300 µm line interval was most efficient to evaluate the tube formation, a sapient angiogenic indicator. This patterned film will provide an effective and promising method for evaluating angiogenesis.