Browsing by Author "Takhar, Vishakha"

The present disclosure relates to an electrode, a process for preparing the electrode, and an apparatus for electrolysis of water. The electrode comprises a conductive substrate, a conductive carbon additive, and a polymeric binder material. A material layer disposed on said conductive substrate, the material layer comprising an active material having a formula A2BX6, wherein A is an inorganic monovalent cation, B is a divalent metal cation, and X is a halide anion. The material enhances photo-assisted OER and offers potential STH benefits at the system level, making it suitable for renewable energy applications. An apparatus for electrolysis of water includes a reaction chamber, an electrode, a counter electrode, and a source configured to induce a water-splitting reaction to generate hydrogen and oxygen.

The present disclosure relates to an apparatus and method for wastewater treatment and chemical recovery. The apparatus comprises at least one wastewater feeding unit (101), at least one treatment unit (102), at least one treated water collection unit (103) in fluid communication with said treatment unit (102), at least one recovery solution storage unit (104) and at least one recovered solution storage unit (105). The apparatus has a compact design, is safe and reliable, is simple and cost-effective, environment-friendly, suitable for applications needing quick wastewater treatment and requires minimal modifications in various existing systems. The method for wastewater treatment and chemical recovery is easy to perform, economical and is environment-friendly.

We present the power exchange dynamics between two closely kept metal-insulator-metal (MIM) structures that constitutes a surface plasmon polariton waveguide directional coupler. This composite MIM waveguide coupler is a miniature one. A comparative study of the power exchange and coupling dynamics is presented for Gold, Silver, Aluminium and Copper; the commonly used noble metals for MIM waveguides. Finite-difference-time domain method based full numerical experiments are performed to reveal the impact of the operating wavelength, refractive indices of the waveguides and other system parameters on the coupling profile of the plasmonic directional coupler. Unlike a conventional dielectric coupler MIM waveguide coupler shows linear increment in coupling length with increasing wavelength. Insertion of dielectric media in between the metal strips strengthens the coupling. The influence of nature of the metal-dielectric interfaces and waveguide asymmetry on the power coupling profile is demonstrated.

This review provides a critical evaluation of the photocatalytic processes that control the efficiency of transition metal dichalcogenides (TMDCs) and their hybrid composites in notable applications, including pollutant abatement, hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and carbon dioxide (CO₂) reduction. TMDCs possess excellent physicochemical characteristics with tuneable bandgaps, large surface area, and intense visible-light absorption that render them exceptionally competent for initiating photo-induced redox reactions. The review highlights mechanistic understanding concerning charge carrier generation and separation, defect engineering, and interfacial electron transfer, all of which is a key to improved photocatalytic performance. Particular focus is on pollutant degradation mechanisms, water splitting kinetics, and CO₂ photoreduction mechanisms. Though promising, TMDCs face challenges such as photo-corrosion, short-term stability issues, and scale-up limitations. To overcome these challenges, the formation of heterojunctions with visible-light-active semiconductors, such as halide perovskites, is emphasized as a potential method to enhance charge separation and broaden spectral response. Furthermore, the integration of TMDCs with cocatalysts and the design of multicomponent heterostructures are investigated as methods to promote durability and efficiency. This review emphasizes the central role of TMDCs in developing scalable and sustainable photocatalytic systems for environmental and energy applications.

Herein, we demonstrate a facile and versatile method to decorate various sizes of silver nanodomes (ZnONR@AgND) along the length of zinc oxide nanorods (AgND) grown over fluorine-doped tin oxide (FTO) substrate. The silver nanodomes (AgND) embedded along the edges of hexagonal zinc oxide nanorods/FTO (ZnONR) substrate were fabricated by using a combination of size selective ZnONR growth and thermal reconstruction. The prepared heterostructure's structural, morphological, and optical behaviors were analyzed by Transmission electron microscopy (TEM), X-Ray diffraction, Raman spectroscopy, field emission scanning electron microscopy (FE-SEM), and UV-Vis spectroscopy. The results confirm the formation of ZnONR@AgND heterostructure with close-packing and construction of the crystalline AgND, adhering to the different faces of the 1D semiconducting ZnONR rods. The AgND size and separation was controlled by the initial sputter thickness and the thermal budget employed during annealing. Insight into the enhanced mechanism for surface-enhanced raman scattering (SERS) activity of ZnONR@AgND was ascertained by probing the hot-spot localization and the enhancement in the electric field by COMSOL simulations and experimentally verified by using rhodamine 6 G (R6G) probe molecules at various concentration 10⁻³ − 10⁻¹² M. The prepared ZnONR@AgND demonstrated a superior SERS signal (~10 times) due to localization of the hot spots at the AgNDs compared to pure Ag nanoparticles substrate (for 10⁻⁶ M). The improved SERS performance of the ZnONR@AgND is attributed to an effective charge transport within the plasmonic AgND, semiconducting ZnO, and the R6G molecule facilitated by the ability of the heterostructure to accommodate multiple hot-spots in a limited volume. This work demonstrates that the SERS activity of semiconductor-based hybrid Raman substrate can be significantly improved by effectively tuning the metal nanoparticle size and density along the length of such hybrid nanowires.

MoS2 quantum dots (MQDs) with an average size of 1.9 ± 0.7 nm were synthesized using a microwave-assisted method. Absorbance studies confirmed characteristic transitions of MoS2, with absorption humps at 260-280 nm and 300-330 nm, and a band gap of 3.6 ± 0.1 eV. Fluorescence emission studies showed dominant blue and some green emissions under 315 nm excitation, with an absolute quantum yield of ∼9%. The MQDs exhibited fluorescence stability over time after repeated quenching cycles across various pH and media systems. In vitro toxicity tests indicated cytocompatibility, with around 80% cell survival at 1000 mg L⁻¹. Confocal imaging demonstrated significant uptake and vibrant fluorescence in cancerous and non-cancerous cell lines. The MQDs showed strong selectivity towards Fe³⁺ ions, with a detection limit of 27.61 ± 0.25 nM. Recovery rates for Fe³⁺ in phosphate buffer saline (PBS) and simulated body fluid (SBF) systems were >97% and >98%, respectively, with a relative standard deviation (RSD) within 3%, indicating precision. These findings suggest that MQDs have high potential for diagnostic applications involving Fe³⁺ detection due to their fluorescence stability, robustness, enhanced cell viability, and dual-channel imaging properties.

Developing bifunctional electrocatalysts capable of efficiently driving the interconversion between oxygen and water molecules via oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) is crucial for establishing renewable-driven energy infrastructure. A series of lead-free halide perovskites Cs2SnX6 (X = Cl, Br, I) is designed, along with their mixed halide derivatives Cs2SnClxBr6-x (where x = 2, 3, 4), to probe bifunctional OER/ORR activity. Measurements reveal the influence of halide ions on the morphology and unravel the unique halide-electronegativity-tunable electronic properties. Further, these materials are immobilized on carbon paper and utilized as anode, where Cs2SnCl6 and Cs2SnCl2Br4 displayed the best OER activity and appreciable Faradic efficiency. The photophysical properties of the perovskites lead to a distinct enhancement (≈0.24–0.72 mA cm⁻²) in the OER current response for Cs2SnCl6 and Cs2SnCl2Br4 under white-light irradiation. The perovskites maintain their structural and chemical integrity during the (photo)electrocatalysis, as demonstrated by in-depth post-electrolytic surface analysis. The electrocatalysts continue to demonstrate active ORR during the cathodic scan (onset potential of ≈0.6 V vs RHE); however, with minimal influence of photoirradiation. Overall, the Cs2SnX6-based perovskite electrocatalysts exhibit promising bidirectional OER/ORR activity with competitive catalytic efficiency and stability, suitable for developing sustainable devices for O2/H2O redox chemistry-mediated energy transduction applications.

Reactive oxygen species (ROS) are crucial for environmental remediation, and nanomaterials have proven to be extremely effective catalysts for the utilization of ROS to degrade pollutants. This review presents a critical analysis of advanced ROS-generating nanomaterials such as metal oxides, two-dimensional (2D) materials, carbon-based materials, perovskites, and hybrid composites, along with various external triggers for ROS generation. There is a special emphasis on heterojunctions and upconversion systems, which boost charge transfer, band alignment, and interfacial interactions to maximize ROS generation. In contrast to other earlier research that emphasizes the use of particular material categories or biomedical purposes, this review gives special prominence to the environmental applications of nanomaterials, specifically in wastewater treatment. The novelty of this research is in the detailed discussion of hybrid materials, their mechanisms for ROS generation, and the convergence of defect engineering, plasmonic effects, heterostructures, and upconversion strategies toward improved photocatalytic performance. In addition, it critically assesses major challenges including material stability, scalability, environmental compatibility, and the demand for green synthesis methods. Research avenues for the future include devising standardized quantification protocols of ROS, computation-assisted design of materials, and large-scale fabrication methods for translating nanotechnology to real-world application. By addressing these research gaps, this review offers valuable insights into the advancement of next-generation ROS-based nanotechnologies, paving the way for their sustainable and effective implementation in environmental remediation.

In recent years, many 2D nanomaterials like graphene, MoS2, phosphorene, and metal oxide nanosheets have been investigated for gas sensing applications due to their excellent properties. Amongst other 2D nanomaterials, graphitic carbon nitride (g-C3N4) has attracted significant attention owing to its simple synthesis process, tunable electronic properties, and exceptional physicochemical properties. Such remarkable properties assert g-C3N4 as a potential candidate for the next-generation high-performance gas sensors employed in the detection of toxic and flammable gases. Although several articles and reviews are available on g-C3N4 for their synthesis, functionalities, and applications for the detection of humidity. Few of them have focused their attention on gas sensing using g-C3N4. Thus, in this review, we have methodically summed up the recent advances in g-C3N4 and its composites-based gas sensor for the detection of toxic and flammable gases. Moreover, we have also incorporated the synthesis strategies and the comprehensive physics of g-C3N4 based gas sensors. Additionally, different approaches are presented for the enhancement of gas sensing/detecting properties of g-C3N4 based gas sensors. Finally, the challenges and future scope of g-C3N4 based gas sensors for real-time monitoring of gases have been discussed.

This article investigates the power transfer dynamics in a Plasmonic waveguide coupler. The coupler is designed by cutting two parallel air grooves in a silver metallic sheet. The structure of the designed coupler is simulated using the finite difference-time-domain method, to find the impact of the wavelength of the radiation and types of the metals on power transfer characteristics in the coupler.

The synergistic influence of synthesized MoS2 (syn-MoS2) nanosheets and NaYF4:Yb,Tm,Nd upconversion nanoparticles (UCNP) on effective dye degradation is demonstrated. A detailed characterization of bulk MoS2 (b-MoS2), syn-MoS2 (with enhanced photocatalytic activity compared to the commercially available b-MoS2), and UCNP was done. Optical properties revealed that emission spectra of UCNP corresponding to 450, 475, and 650 nm overlap with absorption spectra of MoS2 (∼455 and 635 nm). A comparative methylene blue degradation of 96% could be achieved with the combination of UCNP and syn-MoS2 in comparison to 56.4% for syn-MoS2 and 42% for b-MoS2. Concentration-dependent dye degradation study of UCNP and syn-MoS2 revealed a maximum dye removal efficiency of 99.6% for 150 mg L^-1 of syn-MoS2 and 200 mg L^-1 of UCNP within 2 hrs. Comparative degradation investigations were performed on various dyes (methylene blue, methylene orange, rhodamine B, and their mixture) and water systems (artificial river-water and artificial seawater) to assess the potential applicability of the system in environmental remediation. After five cycles of reusability studies, an efficacy of 88% dye removal was obtained. The mechanism behind this was investigated using the ESR and scavengers test, which confirmed that the primary radicals responsible for dye degradation were superoxide (^•O2^-) and hydroxyl (^•OH). A comparative photocurrent experiment also verified that the presence of UCNP enhances the efficiency of the syn-MoS2 by 98% in the presence of visible light.

We demonstrate appropriate tuning of heterojunctions in CsPbBrxCl3−x−MoS2 composites (where x=0,1,2,3) by controlled regulation of the halide stoichiometry in the perovskite. A thorough optimization procedure determined the most effective photocatalyst, considering the pristine MoS2, perovskites with varying halide ratios, various physical mixing ratios of the two, and in-situ synthesized composite ratios of CsPbBrxCl3−x and MoS2 (2 : 1, 1.5 : 1, 1 : 1, 1 : 1.5, 1 : 2). Under two hours of exposure to visible light, a remarkable photocatalytic performance of CsPbBrCl2 : MoS2 with a 1 : 2 ratio was observed, removing 98 % of the methylene blue (MB) dye. Notably, only the CsPbBrCl2 and MoS2 composite demonstrated higher efficiencies since it resulted in a n-n type II heterojunction. Additionally, the CsPbBrCl2 : MoS2 composite exhibits the highest reaction rate constant, fifteen times higher than the pristine perovskite. Reusability assessment of this combination revealed sustained activity of 87 % for up to 5 cycles. The hydrogen evolution reaction investigations were carried out using the optimized CsPbBrCl2 : MoS2 composite, which yielded 265 times more hydrogen than pristine CsPbBrCl2. The Faradaic efficiency for 1 : 2 CsPbBrCl2 : MoS2 was found to be 96.61 %. Our results offer crucial perspectives on optimizing perovskite-MoS2 composites and demonstrate their utility in sustainable applications, including water treatment, renewable energy harvesting, and environmental remediation.