Mani Preeyanghaa

Nonclassical crystal growth in impurity-containing systems frequently exhibits growth arrest, macrostep-assisted growth recovery, and hysteresis, which cannot be adequately described by conventional impurity-pinning theories alone. In this work, we develop the pinning-activated growth macrostep transition model (PAGMTM), a bounded phenomenological kinetic model that provides a unified description of impurity-controlled crystal growth through the coupled processes of elementary-step pinning, macrostep activation, growth recovery, and reverse macrostep deactivation. The model introduces two characteristic driving-force thresholds associated with elementary-step depinning and macrostep activation. Growth suppression is represented through an impurity-controlled reduction function, whereas growth recovery is described by a bounded macrostep activation function that progressively restores the intrinsic crystal growth kinetics without exceeding the clean-surface growth limit. The inverse form of the activation function further enables estimation of characteristic kinetic activation levels (e.g., 10%, 50%, and 90%), providing a quantitative measure of the transition from elementary-step-dominated to macrostep-assisted growth. Complementary formulations based on supersaturation and temperature (supercooling) are developed, allowing the framework to be applied to both isothermal and cooling crystallisation systems. The model is validated against literature data for potassium dihydrogen phosphate (KDP) and K2SO4 crystal growth in the presence of Fe(III) and Cr(III) impurities, successfully reproducing growth suppression, progressive macrostep-assisted recovery, and hysteresis during both forward and reverse growth. The results demonstrate that impurity-mediated crystal growth can be quantitatively interpreted using a unified kinetic framework that links experimentally measurable growth-rate behavior with effective interfacial transition parameters, providing a physically interpretable approach for analyzing impurity-controlled nonclassical crystal growth.

Transition metal-based layered double hydroxides (LDHs) have gained an attractive interest among two-dimensional (2D) materials because they offer tunable structure, abundant active sites, and superior stability for carbon-dioxide (CO2) reduction. Recently, defect engineering, particularly transition metal vacancies, acted as the most important defects in enhancing the bifunctional catalytic activity of LDHs both in photocatalysis and electrocatalysis. This review explores the critical role that transition metal vacancies and defects play in improving CO2 adsorption, activation, and charge transfer processes, which in turn enhance catalytic performance. The interaction between defect engineering and LDHs electronic structure is examined, providing insight into the processes that support multi-electron transfer pathways and stabilize reaction intermediates. Furthermore, generating defects in layered double hydroxides and advanced spectroscopic techniques such as XAS, ESR, and PAS for defect-driven catalytic behavior are discussed. This review demonstrates the ground-breaking potential of defect-engineered LDHs in creating sustainable, dual-functional catalytic systems for CO2 reduction by tackling the problems of stability, scalability, and defect control. The insights provided in this review aim to inspire innovative approaches for the design of next-generation catalysts, paving the way for effective carbon capture and conversion technologies.

Scaling up photocatalytic systems for large-scale hydrogen generation holds transformative potential for sustainable energy but faces significant technical and economic challenges in transitioning from lab-scale experiments to industrial applications. This review delves into recent innovations that drive progress in this field, including advanced materials developed for improved efficiency and stability, as well as innovative reactor designs that optimize light capture and reactant flow. It also examines practical strategies for the integration of these systems with renewable energy sources, focusing on their scalability and cost-effectiveness. Key challenges addressed include mass transport limitations, reactant utilization, and catalyst longevity, accompanied by emerging solutions that aim to overcome these hurdles. The review comprehensively explores the intersection of technological advancements and economic feasibility, emphasizing environmental and economic considerations necessary for the practical implementation of photocatalytic hydrogen production. Emphasizing the most recent developments and strategic approaches, this review outlines a pathway for advancing large-scale sustainable hydrogen generation technologies.

Plastics became the preferred choice for food packaging due to their affordable cost, production efficiency, durability and application versatility. Small scale food beverage shops in metropolitan and urban areas in India frequently employ single-use plastic for packaging hot beverages and other food items, but the inadequately addressed issue of microplastic seepage, particularly from low-density polyethylene (LDPE) covers, remains a concern. The objective of the study was to identify the leachate of plastics from food packaging covers as a result of exposure to hot water at a temperature above 80 ºC. Microplastic sample treated with Fenton’s reagent and filtered using Whatman® grade GF/C microfiber filter paper and visually inspected using a light microscope. The morphological identification and chemical composition of microplastics was done using scanning electron microscope-energy dispersive X-ray spectroscopy (SEM-EDS). Nature of microplastics was characterized using reflectance Fourier transform infrared (FT-IR) analysis. The study observed the presence of around 20-30 microplastics with an average size ranging from 40 to 200 µm. Further, the EDS analysis confirmed the presence of microplastic particles in the filtered leachate, as indicated by the carbon peak at 0.3 to 0.4 KeV. Furthermore, the FT-IR analysis showed the presence of polyethylene microplastics leached from the tested samples. Despite the ban on single-use plastics, their persistent use in food packaging necessitates this study to raise awareness about microplastics and their impact on human health.

There is a growing demand for efficient methods to decrease hazardous organic contaminants in wastewater. Herein, a novel S‐scheme WS₂/BiOI heterojunction photocatalyst was prepared by a one‐pot solvothermal process. The structural morphology, crystal structure and optical absorption studies were studied. The sugar‐like nanocrystals of WS₂ are deposited on 3D‐BiOI marigold flowers, providing high surface area with increased visible light absorption. The photocatalytic activity of the synthesized materials was studied by visible light degradation of Rhodamine‐B (RhB). The optimized 20 wt.% WS₂ in the composite photocatalyst (band gap 2.25 eV) exhibited a 98.9 % photocatalytic degradation activity with a rate constant of 0.0940 min⁻¹ with performance retained after 3 consecutive recycling runs. Photoelectrochemical studies revealed excellent stability, increased separation and migration ability of charge carriers with lower charge resistance in the optimized WS₂/BiOI photocatalyst.

Oxygen-containing porous CN hollow nanotubes were engineered by facile thermal polycondensation of oxalic acid-assisted supramolecular aggregates and revealed superior photocatalytic hydrogen production.