Sustainable Generation of Ni(OH)2 Nanoparticles for the Green Synthesis of 5-Substituted 1 H-Tetrazoles:A Competent Turn on Fluorescence Sensing of H2O2

A mutually correlated green protocol has been devised that originates from a sustainable production of β-Ni(OH)2 nanoparticles which is used for an efficient catalytic synthesis of versatile substituted tetrazoles, under mild reaction conditions in water via a simple, one-pot, eco-friendly method. The synthesis is followed by derivatization into a highly fluorescence active compound 9-(4-(5-(quinolin-2-yl)-1H-tetrazol-1-yl)phenyl)-9H-carbazole that can be used at tracer concentrations (0.1 μM) to detect as well as quantify hydrogen peroxide down to 2 μM concentration. The nanocatalyst was synthesized by a simple, proficient, and cost-effective methodology and characterized thoroughly by UV-vis absorption and Fourier transform infrared spectra, N2 adsorption/desorption, high resolution transmission electron microscopy, powder X-ray diffraction pattern, field emission scanning electron microscopy, and thermogravimetric analysis. Broad substrate scope, easy handling, higher efficiency, low cost, and reusability of the catalyst are some of the important features of this heterogeneous catalytic system. The strong analytical performance of the resultant derivative in low-level quantification of potentially hazardous hydrogen peroxide is the key success of the overall green synthesis procedure reported here

Spark plasma sintering processed alpha-SiAlON bonded tungsten carbide: Densification, microstructure and tribomechanical properties

Processing, microstructure and tribomechanical performance of spark plasma sintering (SPS) processed alpha-SiAlON bonded tungsten carbide (WC) have been reported. SPS at 1750 degrees C under 40 MPa for 25 min resulted in almost theoretically dense composites. Microstructure analysis using scanning and transmission electron microscopy revealed formation of principally micron sized, equiaxed WC grains surrounded by sub-micron to micron sized alpha-SiAlON having both equiaxed (higher concentration) and elongated (lower concentration) grain morphology. Sharp and clean WC/alpha-SiAlON interface regions were noticed without any interfacial reaction product. As evidenced from elemental mapping under HAADF-STEM, the alpha-SiAlON grain boundary region was found to be rich in yttrium and oxygen, whereas, presence of characteristics elements were identified in alpha-SiAlON and WC grains. Addition of alpha-SiAlON in WC matrix resulted in progressive improvement in tribomechanical performance of the composites compared to pure WC. The 40 wt% alpha-SiAlON bonded WC matrix composite offered almost 30-33% higher Vickers hardness and toughness than those obtained for pure WC. Three point flexural strength of the 40 wt% alpha-SiAlON/WC composite was found to be around 425 MPa. Unlubricated wear tests also indicated significantly higher damage of hard and tough beta-Si3N4 ball when sliding against the composites compared to pure WC. Formation of progressively thicker and adherent tribolayer containing broken particles of WC and alpha-SiAlON having sharp edges was possibly the primary reason that caused severe abrasive wear of the counterbody. Results indicated the efficacy of SPS processed alpha-SiAlON bonded WC composites having improved tribomechanical performance over conventional monolithic WC

Densification, microstructure and tribomechanical properties of SPS processed beta-SiAlON bonded WC composites

Densification, microstructure and tribomechanical properties of spark plasma sintering (SPS) processed beta-SiAlON (20-40 wt%) bonded WC matrix composites have been reported. All the specimens achieved almost their theoretical density values after SPS at 1750 degrees C for 25 min under 40 MPa. Incorporation of beta-SiAlON in WC significantly altered the densification trend of the composites resembling that of pure beta-SiAlON. Microstructural investigations using scanning and transmission electron microscopy revealed formation of principally equiaxed, micron sized WC grains surrounded by the sub-micron to micron sized beta-SiAlON phase. The interface region between WC and beta-SiAlON was found to be free of any reaction product. Energy dispersive X-ray spectrum confirmed presence of characteristics elements in both WC and beta-SiAlON phases in the composite. The maximum Vickers hardness (similar to 18 GPa) and fracture toughness (similar to 6.8 MPa-m(0.5)) under 10 kgf were obtained for the 30 wt% beta-SiAlON/WC composite. These were almost 6% and 50% higher, respectively, than those obtained for pure WC. Indentation size effect (ISE) analyses of some selected specimens indicated moderate sensitivity towards ISE (Meyer's exponent = 1.802) of the 30 wt% beta-SiAlON/WC composite and higher true hardness (similar to 15.4 GPa) than those obtained for both the constituent phases. The load dependence of fracture toughness of some selected specimens has also been reported. Unlubricated wear studies under 30 N up to 250 m using ball-on-disc configuration indicated similar to 46-55 times higher specific wear rate of the beta-Si3N4 ball when rubbed against the composites compared to that (similar to 8 x 10(-6) mm(3)/N-m) obtained against pure WC. Formation of compacted flaky tribo-layer within the wear track of the composites was evidenced

Z < 60-Rare earth promoted alpha-Si3N4 solid solution: Praseodymium

So long, larger sized rare earth cations than Neodymium (Z=60) were reported to form alpha-SiAlON either in a multi-cation system containing smaller cations or by following special processing conditions. In this study, Praseodymium (Z=59) alone is observed for the first time to promote alpha-SiAlON as a single crystalline phase, prepared under conventional processing conditions of heating and cooling cycle. The appearance of alpha-SiAlON is restricted to the compositional area corresponding to a high level substitution of m(RE1/3Al-N) for m(Si-N) bonds. Microstructure exhibits strain contrast in grains and array of dislocations in low angle grain boundary indicating deformation in lattice. (C) 2015 Elsevier Ltd. All rights reserved

Sintering and characterization of a hard-to-hard configured composite: Spark plasma sintered WC reinforced alpha-SiAlON

In this study, a composite comprising WC particulate-reinforced alpha-SiAlON was fabricated by spark plasma sintering (1750 degrees C/40 MPa/25 min) in order to develop a hard-to-hard phase configuration and to toughen the hard matrix through particulate reinforcement. Irrespective of the composition, the sintered samples were almost theoretically dense. The nature of the overall sintering process for the composite appeared to be guided by the liquid phase sintering of the SiAlON phase. Microstructural analyses using scanning and transmission electron microscopy indicated the presence of both equiaxed and elongated alpha-SiAlON grains. The WC grains principally appeared equiaxed in nature. A reaction product was not observed at the WC/alpha-SiAlON interface. High-angle annular dark-field scanning transmission electron microscopy imaging indicated the reasonable distribution of the elements within the constituent grains and grain boundary. The presence of an intergranular glassy phase was confirmed, which was principally rich in oxygen and yttrium, with some occasional tungsten in the case of triple junctions. The composite exhibited an acceptable combination of flexural strength, hardness, and fracture toughness with values around 489 MPa, 20 GPa, and 6 MPa-m(0.5), respectively. In contrast to expectations, a decline in hardness was observed up to <= 30 wt% WC. Presumably, the WC grains acted as defects/inclusions with similar dimensions, which eventually resulted in inadequate interfacial performance and reduced hardness. Improvements in the Vickers hardness and fracture toughness were obtained at a WC loading of 40 wt%. The indentation size effect and load dependence of the fracture toughness were also determined for some selected specimens. Higher damage rates for the beta-Si3N4 counterbody against the 40 wt% WC/alpha-SiAlON composite were observed up to 30 N under unlubricated conditions compared with those obtained against the monolithic constituent phases, i.e., alpha-SiAlON and WC. The formation of an adherent tribolayer was observed

ML-DTD: Machine Learning-Based Drug Target Discovery for the Potential Treatment of COVID-19

Recent research has highlighted that a large section of druggable protein targets in the Human interactome remains unexplored for various diseases. It might lead to the drug repurposing study and help in the in-silico prediction of new drug-human protein target interactions. The same applies to the current pandemic of COVID-19 disease in global health issues. It is highly desirable to identify potential human drug targets for COVID-19 using a machine learning approach since it saves time and labor compared to traditional experimental methods. Structure-based drug discovery where druggability is determined by molecular docking is only appropriate for the protein whose three-dimensional structures are available. With machine learning algorithms, differentiating relevant features for predicting targets and non-targets can be used for the proteins whose 3-D structures are unavailable. In this research, a Machine Learning-based Drug Target Discovery (ML-DTD) approach is proposed where a machine learning model is initially built up and tested on the curated dataset consisting of COVID-19 human drug targets and non-targets formed by using the Therapeutic Target Database (TTD) and human interactome using several classifiers like XGBBoost Classifier, AdaBoost Classifier, Logistic Regression, Support Vector Classification, Decision Tree Classifier, Random Forest Classifier, Naive Bayes Classifier, and K-Nearest Neighbour Classifier (KNN). In this method, protein features include Gene Set Enrichment Analysis (GSEA) ranking, properties derived from the protein sequence, and encoded protein network centrality-based measures. Among all these, XGBBoost, KNN, and Random Forest models are satisfactory and consistent. This model is further used to predict novel COVID-19 human drug targets, which are further validated by target pathway analysis, the emergence of allied repurposed drugs, and their subsequent docking study

Spark plasma-sintered MoSi2-reinforced Y-alpha-SiAlON ceramics: mechanical and high temperature tribological properties

Silicon aluminum oxy-nitride commonly abbreviated as SiAlON is indeed one of the most promising non-oxide engineering ceramics due to its ease of formation compared to extremely covalent silicon nitride ceramic and scope of tailoring the material properties as per application demand. To make it more suitable for high-performance applications, composites containing various secondary phases have been attempted so far to improve the mechanical performance over its monolithic counterpart. In the present work, reinforcement of particulate molybdenum disilicide (MoSi2) in Y-alpha-SiAlON matrix has been undertaken under spark plasma sintering (1750 degrees C, 10 min, 50 MPa die pressure) followed by Vickers hardness (HV), fracture toughness (K-IC), and high-temperature tribological properties under different conditions of the formed composites containing 10 and 20 wt.% secondary phase were investigated. Sintered specimens were >= 97.5% dense with negligible porosity. Addition of MoSi2 in Y-alpha-SiAlON resulted in reduced HV. The 20 wt.% MoSi2/Y-alpha-SiAlON composite showed similar to 11% lower HV1 compared to the monolith. On the contrary, K-IC of the 20 wt.% MoSi2/Y-alpha-SiAlON composite was found to be around 24% higher compared to pure Y-alpha-SiAlON (K-IC approximate to 3.9 MPa-m(0.5)). Additional fracture energy dissipation through crack deflection and bridging by the dispersed MoSi2 particulates was the primary reason behind obtaining higher fracture toughness for the composites. Unlubricated reciprocating ball-on-disc experiments against dense silicon nitride ball revealed a significant effect of MoSi2 oxidation in achieving improved wear resistance of the composites over the monolith, especially, beyond 300 degrees C in ambient air under applied normal loads up to 90 N and sliding distance up to 70 m