Journal of Nano Research Vol. 90

Abstract: Heterostructures are important for various electrical, optical, and magneto-transport applications. In the present work, MoS₂/ZnO heterostructures are successfully grown by magnetron sputtering followed by annealing of ZnO thin films. After annealing, ZnO is again coated with Mo by using the same technique. ZnO-Mo stack is further sulfurized to convert Mo into MoS₂. X-ray diffraction (XRD) showed the structural analysis of ZnO, MoS_2, and MoS₂/ZnO heterostructures with polycrystalline nature. Scanning electron microscopy (SEM) also supports the granular morphology of ZnO, MoS_2, and MoS₂/ZnO films. Energy dispersive X-ray analysis (EDX) confirms the presence of necessary elements i.e., Zn, Mo, S, O, and Si. Further, the impact of the magnetic field on the current-voltage (I-V) behavior of MoS₂/ZnO heterostructures, reveals insights into their magneto-resistive capabilities.

Abstract: ZnO thin films were deposited on borosilicate glass substrates by confocal radio frequency (RF) magnetron sputtering and subsequently annealed in air at 300 °C and 500 °C for 60 min. The influence of thermal treatment on the structural, morphological, optical, and electrical properties was systematically investigated. X-ray diffraction (XRD) confirmed the formation of a hexagonal wurtzite phase with a pronounced (002) preferential orientation. Rietveld refinement analysis revealed that annealing led to a decrease in the lattice parameter c from 5.344 Å to 5.220 Å, an increase in crystallite size from 9.3 nm to 34.1 nm, and a reduction in microstrain from 0.0265 to 0.0027. Raman spectroscopy exhibited a sharper E₂^high mode at 438 cm^-1 and a suppressed defect-related A₁(LO) mode (583 cm^-1), evidencing enhanced crystallinity and defect passivation. Scanning electron microscopy (SEM) observations revealed grain coalescence and densification with increasing annealing temperature. The average optical transmittance improved from 70.8% to 82.2%, accompanied by a slight widening of the optical band gap from 3.22 eV to 3.27 eV. Hall measurements indicated a marked decrease in resistivity from 2.7 × 10^-2 Ω·cm to 5 × 10^-3 Ω·cm, yielding a maximum figure of merit of 1.68 × 10^-3 Ω^-1 at 500 °C. Overall, post-deposition annealing is shown to significantly enhance crystallinity, reduce structural defects, and improve the optoelectronic performance of ZnO thin films, confirming their suitability for transparent electronics and photovoltaic applications.

Abstract: Cu₃SnS₄ films were grown on glass substrates via method of spin coating, followed by annealing at 550 °C in a furnace under H₂S:Ar (1:9) sulfur rates of 30 and 40 sccm for 15, 30, and 60 minutes. The effect of the sulfur rate and annealing time on the structural, morphological, and optical behaviors of the samples was systematically investigated using X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), atomic force microscopy (AFM), photoluminescence (PL), Hall effect, and UV-Vis spectroscopy. The XRD patterns revealed that all the Cu₃SnS₄ samples had a polycrystalline structure. The crystallite size, dislocation density, interplaner distance, micro-strain, and crystallite number of the Cu₃SnS₄ samples were calculated from the XRD spectra. Among all the samples, the CTS sample annealed for 15 minutes under a 30 sccm H₂S:Ar (1:9) gas flow showed the best crystalline structure. The surface morphology of the samples showed spherical micro-crystal formations. Analysis of the Cu₃SnS₄ samples indicated that the surfaces were composed of valley and peak regions. The valley regions appeared relatively smooth, while the peak regions displayed a crystal structure with specific orientations. When examining the energy band gap values, it is observed that the energy band gap of the films increases significantly with the increase in sulfur flow rate. PL analysis revealed emission peaks at approximately 1.41 eV and 1.80 eV, along with broad emission bands at 549 nm, 567 nm, 689.42 nm, and 882.6 nm. An increase in sulfur content led to a reduction in peak intensity, which is attributed to conduction band fluctuations and the formation of structural defects. The carrier concentration of the samples is found to be on the order of 10¹⁷ cm⁻³ and 10¹⁸ cm⁻³, which is more appropriate for thin-film solar cells (TFCSs).

Abstract: High-performance ultraviolet photodetectors require high sensitivity, fast response, strong radiation resistance, and high on/off ratio. This study investigates the impact of in-situ nitrogen doping on the performance of Silicon Carbide ultraviolet photodetectors (SiC-UVPDs). The SiC-UVPD devices demonstrated high sensitivity, fast response, low dark current, and good stability. Notably, the sensitivity of the devices increased with higher nitrogen doping, reaching 1.94 × 10⁵ % for the 8-sccm nitrogen-doped SiC-UVPD under 254 nm UV light illumination at 20 V - a 51% improvement compared to undoped SiC-UVPDs. Furthermore, nitrogen doping did not compromise the devices' response speed. Consequently, the combination of high sensitivity, fast response, low-cost fabrication, and robust radiation resistance positions SiC-UVPDs as promising candidates for high-performance ultraviolet photodetectors, particularly in harsh environment applications.

Abstract: Through a simple electrodeposition technique, SnO₂/MnO₂ nanocomposite films were directly deposited onto ultrathin stainless-steel (SS) foils for use in electrochemical supercapacitors. The materials were characterized by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD). Electrochemical experiment revealed that the SnO₂/MnO₂ electrodes exhibited a high gravimetric capacitance of 876 F/g at a current density of 1 A/g. Furthermore, an asymmetric supercapacitor was fabricated using the SnO₂/MnO₂ nanocomposite as the positive electrode and activated carbon as the negative electrode. This asymmetric device demonstrated a capacitance of 72.2 F/g at 1 A/g and retained approximately 87.5% of its initial capacitance after 28,000 cycles, highlighting its excellent cycling stability and practical application potential. The combination of high capacitance and robust stability makes this SnO₂/MnO₂ nanocomposite a promising candidate for high-performance supercapacitor electrodes.

Abstract: The development of sustainable ammonia synthesis methods is crucial for reducing the environmental impact of the energy-intensive Haber–Bosch process. However, creating efficient and cost-effective electrocatalysts for ammonia synthesis remains a significant challenge, primarily due to competition from the hydrogen evolution reaction (HER), which diverts current away from ammonia production and reduces Faradaic efficiency. This study investigates the electrocatalytic performance of a La₀.₃Sr₀.₇Ti₀.₈Fe₀.₂O₃-_δ and Ce₀.₈Gd₀.₁₈Ca₀.₀₂O₂-_δ (LSTF–CGDC) composite cathode for green ammonia production from humid nitrogen (3% H₂O) under ambient pressure. Synthesized via a sol–gel method and characterized using X-ray diffraction (XRD), the composite exhibited high structural stability and phase compatibility. Ammonia synthesis was achieved across a temperature range of 375–450 °C and applied voltages of 1.2–1.8 V, with a peak production rate of 4.0 × 10⁻¹¹ mol s⁻¹ cm⁻² at 425 °C and 1.4 V. Despite these promising results, the Faradaic efficiency remained low (~0.07%) due to persistent HER competition. This study underscores the potential of non-noble perovskite-based catalysts for sustainable ammonia production and highlights the need for further optimization in both selectivity and efficiency.

Abstract: Nanostructured titanium dioxide (TiO₂) was synthesized via a hydrothermal method to enhance photocatalytic degradation of organic and pharmaceutical contaminants in wastewater. Characterization techniques confirmed the formation of anatase-phase TiO₂ with a tetragonal structure, spherical morphology, and an average crystallite size of 29 nm. The material exhibited a band gap of 3.1 eV. The TiO₂ solution has proven to be very effective in accelerating the breakdown of pharmaceutical and organic contaminants in wastewater, as evidenced by several methods, including high-performance liquid chromatography (HPLC) and Gas chromatography (GC). Photocatalytic performance was evaluated under varying catalyst concentrations and pH levels. Optimal degradation efficiency (72%) was achieved at pH 10, demonstrating TiO₂'s potential as an effective photocatalyst for wastewater treatment.

Abstract: A novel Mg_1-xCo_xAl₂O₄ (x=0, 0.25, 0.50, 0.75 and 1) nano-catalyst with high viscosity reduction rate of heavy oil and photocatalytic activity for the degradation methylene blue was synthesized by a tartaric acid complexation method. The crystallite size, cell parameter, cell volume and particle size of Mg_1-xCo_xAl₂O₄ catalyst are proportional to the x value, while the specific surface area is inversely proportional to the x value. The effects of different catalyst, catalyst content and water content on viscosity reduction rate of Dongying heavy oil were investigated. When the catalyst content of Mg_0.5Co_0.5Al₂O₄ is 15 wt%, the viscosity reduction rate of heavy oil reaches 89.53%, while water decreases the viscosity reduction rate. The degradation percentage of the Mg_1-xCo_xAl₂O₄ (x=0.5) catalyst for the degradation of methylene blue reached 95.34% when the catalyst dose was 1 g/L, the dye concentration was 15 mg/L and pH was 7. The dye sensitization greatly improved the photocatalytic activity of the MgAl₂O₄ under the combined action of Mg and Co ions. This new experimental phenomenon will help to expand the application range of spinel aluminate in catalysis fields including reduce viscosity with heavy oil and dye removal.

Abstract: Plant-based nanoparticles (NPs) synthesis has gained increasing attention due to its cost-effectiveness, rapidity, and environmental friendliness. In this study, the green synthesis of silver nanoparticles (MP-AgNPs) using Maclura pomifera fruit extract and their antioxidant activities were investigated. The synthesized MP-AgNPs were characterized by Ultraviolet-Visible (UV-Vis) spectroscopy, Scanning Electron Microscopy (SEM), Energy-Dispersive X-ray Spectroscopy (EDX), Fourier Transform Infrared (FTIR) spectroscopy, and X-ray Diffraction (XRD) analysis. According to the EDX results, the elemental composition by mass was 22.72% carbon, 13.89% oxygen, and 57.74% silver. SEM analysis revealed that the MP-AgNPs were predominantly spherical, with an average particle size of 39.02 nm. The zeta potential of MP-AgNPs was measured as –34.6 mV, indicating good nanoparticle stability and electrostatic repulsion among particles. In antioxidant assays, the ABTS radical scavenging activity showed IC₅₀ values of 6.36 ± 0.02 µg/mL for MP-AgNPs, 7.27 ± 0.00 µg/mL for BHT, and 10.58 ± 0.01 µg/mL for the extract. Furthermore, FRAP assay results demonstrated increased antioxidant activity in the order of extract (3.55 ± 0.00 µmol TE/mg), BHT (5.33 ± 0.01 µmol TE/mg), and MP-AgNPs (5.39 ± 0.02 µmol TE/mg).

Abstract: This material presents the research of AlTiN coating properties, deposited at low temperature by cathodic arc physical vapor deposition technology. As well as evolutionary development of coating when is added Cr element to it, or creating multilayer structure adding a CrN as internal layer on it. Each of these steps results in increasing with almost 80% of coating resistance to plastic deformation and a huge reduction in the wear rate of the resulting coating.