CdS-graphene Nanocomposite for Efficient Visible-light-driven Photocatalytic and Photoelectrochemical Applications

Inorganic CsPbX3 perovskites with compositions including CsPbBrxCl3−x, CsPbBr3, and CsPbBrxI3−x are synthesized, and their properties are investigated. Tauc plots calculated from the UV–vis spectra of the materials show that the bandgaps of CsPbBrxCl3−x, CsPbBr3, and CsPbBrxI3−x are 2.7, 2.35, and 1.8 eV, respectively. The as-prepared CsPbX3 nanodots have a cubic structure and their crystal sizes are around 5–10 nm. The diffraction peak intensity of the (110) plane is increased by adding Cl anion and reduced by adding I anion. By contrast, the peak intensity of the (200) plane is reduced by the introduction of Cl− ions and increased by the introduction of I− ions, suggesting that the nature of the halide anions affects the crystal orientation of CsPbX3 quantum dots. The highest occupied molecular orbital/lowest unoccupied molecular orbital levels of CsPbBrxCl3−x, CsPbBr3, and CsPbBrxI3−x calculated from ultraviolet photoemission spectra and UV–vis spectra are 6.5/3.8, 6.5/4.15, and 6.1/4.3 eV, respectively. The maximum luminance values measured for CsPbBrxCl3−x, CsPbBr3, and CsPbBrxI3−x-based light-emitting diodes (LEDs) are 15.2, 51.7, and 21.7 cd m−2, respectively. This research provides an overview of the energy levels and crystal structures of CsPbX3 quantum dots for the design of inorganic perovskite-based LEDs with high luminance and power efficiencies.

Investigation of Energy Levels and Crystal Structures of Cesium Lead Halides and Their Application in Full‐Color Light‐Emitting Diodes

In this study, three different poly(vinyl alcohol) (PVA) films doped with weight percentages of 0.05, 0.10 and 0.20 coumarin were coated on p-Si wafer via spin-coating method for the purpose of investigating the interaction of coumarin dopant with polymer host at molecular level. Therefore, metal–polymer–semiconductor (MPS) structures were formed and their current–voltage (I–V) and admittance measurements were taken to compare the main electrical parameters of the MPS structures with different film thicknesses. The values of ideality factor (n), barrier height (Φb), rectification ratio (RR = IF/IR), series resistance (Rs) and energy-dependent profiles of surface states (Nss) were calculated using the forward bias I–V data. There exists increasing trend for Nss values from mid-gap energy of Si toward the bottom of conductance band. The highest values of RR and photosensitivity (Iphoto/Idark) were found as 4.62 × 104 at ± 4 V for the MPS structure with 0.10 wt% coumarin doping level, respectively. The photoresponse of the structures was also analyzed using $$I_{\text{ph}} = AP^{m}$$ relation, and the value of m was obtained from the slope of ln(Iph)–Ln(P) plot for each diode as 1.48, 1.27 and 1.57, respectively. Experimental results suggest that 0.10% coumarin-doped PVA caused MPS structure to reveal better performance considering higher RR and lowest Nss, and so it can be considered as an alternative interfacial layer material for replacing traditional insulators.

A detailed comparative study on electrical and photovoltaic characteristics of Al/p-Si photodiodes with coumarin-doped PVA interfacial layer: the effect of doping concentration

Multifunctional novel core-shell composites, CdSNPs@ZIF-8, have been synthesized by in situ encapsulation of different amounts of CdSNPs (150, 300, and 500 μL suspension of CdSNPs in methanol) in ZIF-8 at room temperature. These composites have been characterized by powder X-ray diffraction, X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy, high-resolution transmission electron microscopy (HRTEM), and diffuse reflectance spectroscopy techniques and Brunauer-Emmett-Teller surface analysis. XPS and HRTEM indicate the encapsulation of CdSNPs within ZIF-8 crystal without disturbing the crystal order of ZIF-8. The average size of embedded CdSNPs (determined by the particle size distribution from HRTEM) is found to be 16.34 nm. CdSNPs@ZIF-8 showed potential to be used as an antibacterial agent against the broad spectrum of bacterial strains such as Gram-positive Staphylococcus aureus and Gram-negative green fluorescent protein-expressing Escherichia coli in aqueous medium, as evident by various biophysical experiments, viz., 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay, optical density and fluorescence spectroscopic studies, fluorescence and optical microscopic image analysis, disk diffusion assay, field emission scanning electron microscopy, and flow cytometry for reactive oxygen species induction assay. Further, the composite has been used as an efficient photocatalyst for the degradation of organic pollutants, such as methylene blue dye, in aqueous medium and found that the core-shell composite, CdSNPs@ZIF-8 (150 μL) (abbreviated as NC-1) (5 mg), exhibited higher photocatalytic activity (≈1.8 times) than CdSNPs for degradation of 90% of methylene blue (10 mL of 10 ppm) at pH ≥ 7 due to the synergetic effect. Therefore, in situ encapsulation of CdSNPs in ZIF-8 provides an easy executable measure for purification of wastewater effluents for the effective photocatalytic degradation of organic pollutants as well as to remove the bacterial contamination under sunlight.

Multifunctional CdSNPs@ZIF-8: Potential Antibacterial Agent against GFP-Expressing Escherichia coli and Staphylococcus aureus and Efficient Photocatalyst for Degradation of Methylene Blue.

Antioxidant and anti-inflammatory properties of marmelosin from Bael (Aegle marmelos L.); Inhibition of TNF-α mediated inflammatory/tumor markers.

The current–voltage (I–V) and optical characteristics of 4-hydroxy coumarin Schottky diode were investigated. The conventional methods related with device were used to extract the various diode parameters. From dielectric study low dielectric constant and loss was observed. From its optical study, an indirect allowed transition is shown by this compound. The optical band gap (E
 g
 ) was found to be around 3.78 eV. The observed properties shown by this molecule give a bright opportunity to explore its application for different organic devices.

Optical, DC and AC electrical investigations of 4-hydroxy coumarin molecule as an organic Schottky diode

Preparation and characterizations of cadmium sulfide nanoparticles

Composite films of imperatorin (a coumarin molecule) and poly vinyl alcohol (PVA) are prepared by a solution casting method. These composite films are exposed to γ-radiation of different doses at room temperature. These composite films are characterized by X-ray diffraction (XRD), Fourier transform infrared (FT-IR), UV-Visible and dielectric spectroscopy. After doping, the XRD data shows semicrystalline to amorphous phase formation in the PVA back bone. FT-IR analysis of these composite films shows various bands and a significant impact on them can be observed after irradiation. UV-Visible spectroscopy of these composite films shows various absorption bands. But the absorption band at 311 nm is the sharpest one. In these films, the optical band gap is determined by using Tauc's plots. These films follow indirect allowed transitions. In the present samples, the optical band gap increases with irradiation and finally decreases at the highest dose. The Urbach energy also decreases with increasing radiation dose, and gives clear indication that radiation induced defects are formed in the system. Additionally, both the dielectric constant and loss change with radiation dose. These changes are explained based on a universal dielectric response (UDR) model which also supports disorder in the system.

Gamma irradiation studies of composite thin films of poly vinyl alcohol and coumarin

The structural, optical and dielectric properties of micro-crystals of Oxypeucedanin (C16H14O5), isolated from ethyl acetate extract of the roots of the plant Prangos pabularia is presented. These isolated crystals were characterized by using X-ray diffraction (XRD), scanning electron microscopy, optical microscope, ultraviolet (UV)–visible spectroscopy and dielectric spectroscopy techniques. XRD of these crystals confirm that they have monoclinic structure (space group = P21/c). The frequency-dependent real part of the complex ac conductivity was found to follow the universal dielectric response: σac (ω)–ω
 s
 . The trend in the variation of the frequency exponent (s) with frequency (ω) supports the fact that correlated barrier hopping is the dominant charge transport mechanism for this compound. From the UV spectroscopy, the optical band gap (E
 g
 ) has been found to be around 3.76 eV and is following indirect allowed transition. The observed optical and electric properties predict these crystals as an open choice for modern flexible electronics.

Crystal structure, morphological, optical and electrical investigations of Oxypeucedanin micro crystals: an isolated compound from a plant

In the present paper, 4-hydroxy coumarin compound was synthesized. The crystallographic phase of this molecule was carried out by X-ray diffraction and confirms its monoclinic structure. Associated functional groups were predicted by Fourier transform infrared spectroscopy. To see its potential utility, a Schottky diode of this material was fabricated. The current–voltage (I–V) and optical characteristics of this Schottky diode were also investigated. Various well-established methods related with the device were used to get information about various diode parameters. From its optical measurement, this compound shows an indirect allowed transition. From optical data analysis, a band gap (E
 g) of around 3.78 eV was shown by this compound. The observed features exhibited by this molecule give a vital chance to explore its application for various optoelectronic devices.

K. Asokan

Papers

Optical, DC and AC electrical investigations of 4-hydroxy coumarin molecule as an organic Schottky diode

Preparation and characterizations of cadmium sulfide nanoparticles

Gamma irradiation studies of composite thin films of poly vinyl alcohol and coumarin

Crystal structure, morphological, optical and electrical investigations of Oxypeucedanin micro crystals: an isolated compound from a plant

Structural, optical and transport properties of 4-hydroxy coumarin: an organic Schottky diode