Perovskite LaNiO3/Ag3PO4 heterojunction photocatalyst for the degradation of dyes

Pristine lanthanum nickelate (LaNiO3), silver phosphate (Ag3PO4) and perovskite lanthanum nickelate silver phosphate composites (LaNiO3/Ag3PO4) were prepared using the facile hydrothermal method. Three composites were synthesized by varying the percentage of LaNiO3 in Ag3PO4. The physical properties of as-prepared samples were studied by powder X-ray diffraction (pXRD), Fourier-transform infrared (FT-IR), Scanning electron microscopy (SEM) and Energy-dispersive X-ray (EDX). Among all synthesized photocatalysts, 5%LaNiO3/Ag3PO4 composite has been proved to be an excellent visible light photocatalyst for the degradation of dyes i.e., rhodamine B (RhB) and methyl orange (MO). The photocatalytic activity and stability of Ag3PO4 were also enhanced by introducing LaNiO3 in Ag3PO4 heterojunction formation. Complete photodegradation of 50 mg/L of RhB and MO solutions using 25 mg of 5%LaNiO3/Ag3PO4 photocatalyst was observed in just 20 min. Photodegradation of RhB and MO using 5%LaNiO3/Ag3PO4 catalyst follows first-order kinetics with rate constants of 0.213 and 0.1804 min−1, respectively. Perovskite LaNiO3/Ag3PO4 photocatalyst showed the highest stability up to five cycles. The photodegradation mechanism suggests that the holes (h+) and superoxide anion radicals O2 •− plays a main role in the dye degradation of RhB and MO

Low leakage-current InAsSb nanowire photodetectors on silicon

Axially doped p–i–n InAs0.93Sb0.07 nanowire arrays have been grown on Si substrates and fabricated into photodetectors for shortwave infrared detection. The devices exhibit a leakage current density around 2 mA/cm2 and a 20% cutoff of 2.3 μm at 300 K. This record low leakage current density for InAsSb based devices demonstrates the suitability of nanowires for the integration of III–V semiconductors with silicon technology

Room temperature mid-infrared emission from faceted InAsSb multi quantum wells embedded in InAs nanowires

There is considerable interest in the development of InAsSb-based nanowires for infrared photonics due to their high tunability across the infrared spectral range, high mobility, and integration with silicon electronics. However, optical emission is currently limited to low temperatures due to strong nonradiative Auger and surface recombination. Here, we present a new structure based on conical type II InAsSb/InAs multiquantum wells within InAs nanowires which exhibit bright mid-infrared photoluminescence up to room temperature. The nanowires are grown by catalyst-free selective area epitaxy on silicon. This unique geometry confines the electron–hole recombination to within the quantum wells which alleviates the problems associated with recombination via surface states, while the quantum confinement of carriers increases the radiative recombination rate and suppresses Auger recombination. This demonstration will pave the way for the development of new integrated quantum light sources operating in the technologically important mid-infrared spectral range

Growth and characterization of site-controlled InAs(Sb) nanowires for use in infrared photodetectors

There is considerable interest in the development of InAs(Sb) nanowires for infrared photonics due to their high tunability across the infrared spectral range and integration with silicon electronics applications. The use of nanowires in IR photonics also promises transformational advantages. Site-controlled catalyst free epitaxial growth on silicon wafers was used in this work to enable exploitation of recent scientific understanding in the control of light matter interactions through geometry, while also offering practical integration advantages and strong, tuneable optical emission. However, optical emission is currently limited to low temperatures due to strong non-radiative Auger and surface recombination. Simple structures suffer from deleterious effects due to the high surface to volume ratio in nanowires which has limited emission to fixed wavelengths and low temperatures, until now. In this thesis the growth of InAs(Sb) has been developed to realize high performance costeffective optoelectronic structures for the development of emitters and photodetectors operating in the mid-infrared spectral range. In addition to characterizing the optical properties of the grown nanowires, this research has improved their optical efficiency by reducing nonradiative surface and Auger recombination. The growth of advanced InAs nanowires containing embedded multiple quantum well (MQWs) and superlattices (SL) structures is reported for the first time. The MQWs and SL structures are based on type II InAsSb/InAs MQWs which exhibit bright mid-infrared photoluminescence up to room temperature. This unique geometry confines the electron-hole recombination to within the quantum wells which alleviates the problems associated with recombination via surface states, whilst the quantum confinement of carriers increases the radiative recombination rate and suppresses Auger recombination. This demonstration paves the way for the development of new integrated quantum nano-light sources operating in the technologically important mid-infrared spectral range. In this work we also realized the first InAsSb shortwave infrared nanowire photodetectors and the lowest leakage current density reported for any InAs(Sb) photodiode at 300 K. Using the same method of growth (site-controlled epitaxy), allowed for high quality shortwave nanowire infrared photodetectors to be grown on silicon substrates, while obtaining surprisingly low leakage current density. The unique design of these nanowire photodetectors also allows for electrical conduction through the substrate which simplifies many aspects of the fabrication and expands the opportunities for integration. Although the nanowires occupy only a small fraction of the light collection area, optimization of the length and diameter can significantly increase the absorbance up to that of planar films. Combined with the reduction in leakage current density over InAs(Sb), this should provide more than 2 orders of magnitude increase in signal-noise ratio over state-of-the-art InAs(Sb) devices. This represents a major step toward high-performance mid-infrared photodetectors compatible with silicon technologies and which can potentially be integrated with other photonic systems

Evaluation of In Doped GaAs Alloys to Optimize Electronic, Thermoelectric and Mechanical Properties

The electronic, mechanical and transport properties of the In substitution in GaAs are investigated by the TB-mBJ potential, BoltzTraP code and Charpin tensor matrix analysis using Wien2k code. The formation energies of the alloys Ga1−xInxAs (x = 0.0, 0.25, 0.50, 0.75 and 1.0) confirm that they are thermodynamically favorable. The directional symmetry changes when increasing the In concentration and reduces the bandgap from 1.55 eV (GaAs) to 0.57 eV (InAs), as well as reducing the electrical conductivity and increasing the Seebeck coefficient. The thermoelectric performance is depicted by the power factor without including lattice vibration. The elastic properties’ analysis shows mechanical stability, and elastic moduli decrease with an increasing In in GaAs, which converts the brittle nature to ductile. The Debye temperature, hardness and thermal conductivity decrease, thus, increasing their importance for device fabrications

Experimental Investigation on Silicon Powder Mixed-EDM of Nimonic-90 Superalloy

Powder mixed electrical discharge machining (PM-EDM) is a technological advancement in electrical discharge machining (EDM) processes where fine powder is added to dielectric to improve the machining rate and surface quality. In this paper, machining of Nimonic-90 was carried out using fabricated PM-EDM, setup by adding silicon powder to kerosene oil. The influence of four input process parameters viz. powder concentration (PC), discharge current (IP), spark on duration (SON), and spark off duration (SOFF) has been investigated on surface roughness and recast layer thickness. L9 Taguchi orthogonal and grey relational analysis have been employed for experimental design and multi-response optimization, respectively. With the addition of silicon powder to kerosene oil, a significant decrease in surface roughness and recast layer thickness was noticed, as compared to pure kerosene. Spark on duration was the most significant parameter for both surface roughness and the recast layer thickness. The minimum surface roughness (3.107 µm) and the thinnest recast layer (14.926 μm) were obtained at optimum process parameters i.e., PC = 12 g/L, IP = 3 A, SON = 35 μs, and SOFF = 49 μs using grey relational analysis

Effect of Rare-Earth Ions on the Optical and PL Properties of Novel Borosilicate Glass Developed from Agricultural Waste

There is considerable attention devoted to the use of agricultural waste as a raw material substitute for commercial silica in the development of borosilicate glasses doped with rare earth oxides. Here, we present a novel structure for borosilicate glasses made from rice husk ash with a 25% molar ratio of extracted SiO2 and doped with neodymium (GRN) or dysprosium (GRD). Adding rare earth oxides to borosilicate glasses by the melt quenching method enhanced optical transmission due to the presence of their tetrahedral geometries. GRN samples showed few bands near zero, which constitutes good utility for band rejection filters in image devices, and the samples exhibited energy values ranging from 3.03 to 3.00 eV before and after gamma irradiation. Optical transmissions of GRD samples showed peaks at 25,974, 22,172, 13,333, 11,273, 9302, 7987, and 6042 cm−1. Deterioration in transmittance was observed when the investigated samples were exposed to irradiation doses of 20 and 50 kGy in the wavenumber range of 12,500 to 50,000 cm−1; however, different behaviors after irradiation with 50 kGy caused an increase in transparency in comparison to 20 kGy irradiation, which was pronounced for higher wavenumbers (greater than 12,500 cm−1). Photoluminescence emission and excitation spectra of the glass-doped Nd3+ (GRN) and glass-doped Dy3+ (GRD) samples were determined. GRD exhibited emission in the blue and yellow regions of the visible spectrum, which gave a white flash of light. Chromaticity coordinate (CIE) measurements of GRD samples indicated the origin of its luminous color relative to the standard white light region

NiSe₂/Ag₃PO₄ Nanocomposites for Enhanced Visible Light Photocatalysts for Environmental Remediation Applications

This study investigated the use of NiSe2/Ag3PO4 nanocomposite catalysts for the photocatalytic degradation of RhB and BPA pollutants. Samples of pure NiSe2, Ag3PO4, and NiSe2/Ag3PO4 composites with varying NiSe2 (10%, 20%, and 30%) proportions were synthesized using hydrothermal techniques. The 20% NiSe2/Ag3PO4 composite showed the greatest photocatalytic efficiency for both RhB and BPA degradation. The study also examined the impact of various factors, such as the initial concentration of dye, catalyst amount, pH, and reaction time, on the photodegradation process. The 20% NiSe2/Ag3PO4 catalyst effectively degraded 10 ppm RhB in 20 min and 20 ppm BPA in 30 min. The physical properties of the samples were examined using SEM, PXRD, and energy-dispersive X-ray spectroscopy. The cycling runs of 20% NiSe2/Ag3PO4 also exhibited improved stability compared to Ag3PO4, with a degradation rate of 99% for RhB and BPA. The combination and synergistic effect of NiSe2 and Ag3PO4 played a vital role in enhancing the stability of the photocatalysts. Both the RhB and BPA photodegradation followed pseudo-first-order kinetic models with rate constants of 0.1266 min−1 and 0.2275 min−1, respectively. The study also presented a Z-scheme reaction mechanism to elucidate the process of photodegradation exhibited by the composites after active species capture experiments, which showed that superoxide anion radicals and holes were responsible for the photodegradation

Tailoring the optical properties of PC/ZnS nanocomposite by γ radiation

Chemical coprecipitation methodology in atmospheric air has been used to prepare Zinc sulfide (ZnS) nanoparticles (NPs); EDTA-ethylenediamine was used as stabilizing agent. Then ex-situ casting technique was used to synthesis nanocomposite (NCP) from Polycarbonate polymer (PC) and the synthesized ZnS NPs. Detection analysis of XRD records demonstrated that synthesized ZnS adjusts cubic zinc blend construction of lattice constant matches 5.345 Å and an average grain size 4nm. PC/ZnS NCP samples were irradiated with doses of gamma radiation in the range 25‑230 kGy. The modifications in optical parameters of the irradiated NCP samples were investigated using UV spectroscopic analysis and CIE color variation technique. Tauc's model and optical dielectric loss assisted in estimating the optical band gap (Eg) and to recognize the type of electronic transition. Eg decreased from 3.83 to 3.00 eV upon increasing the radiation doses γ up to 230 kGy; demonstrating the enhancement of the amorphous phase in the NCP. This was conveyed by an increase in the refractive index. Moreover, the color variations were explored using UV transmission spectra and the CIELAB color space methodology. The γ radiation causes a reduction in green and blue color components, conveyed by an increase in whiteness. This led to a noteworthy color variation that is applicable in marketable imitation on printing press