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Preparation of fly ash-TiO2-metal hybrid composites for adsorption and photocatalytic applications
(2026-06-05) Sharma, Ridhima; Pal, Bonamali; Barman, Sanghamitra
Abstract: Chapter-1 This chapter provides an overview of adsorption and semiconductor photocatalysis as effective strategies for wastewater treatment, with a focus on fly ash–TiO₂–metal–zeolite hybrid materials. It discusses the environmental impact of industrial effluents and the drawbacks of conventional remediation technologies. The chapter highlights the role of fly ash as an inexpensive, porous support, its functionalization with TiO2 to enhance photocatalytic activity, and subsequent performance improvements achieved through metal doping and zeolite incorporation. A critical review of recent studies illustrates how these components work synergistically to broaden light absorption, enhance charge separation, and improve catalyst durability for degrading dyes. Methods for material synthesis, structural and optical characterization, and performance evaluation are summarized. The chapter concludes by identifying existing research gaps and emphasizing the need for advanced hybrid composites capable of achieving superior efficiency under visible and solar light irradiation. Chapter-2 This study emphasizes the need to achieve both high photocatalytic efficiency and strong adsorption capacity in a catalyst to ensure complete removal of fuchsine blue dye (FB) from wastewater. In this work, TiO2 and fly ash–TiO2 composites (0.5–5wt%) were prepared using a sol–gel method combined with wet impregnation, and their performance was evaluated for combined processes of adsorption and photocatalytic breakdown of fuchsin blue dye. The materials were characterized using XRD, UV–DRS, SEM, EDS, Raman spectroscopy, and N₂ adsorption analysis. Adsorption and degradation experiments were conducted to evaluate the effects of pH (2–10), adsorbent dosage (1–9 mg), contact time (30–180 min), and initial dye concentration (5–30 mg/L) on FB dye removal efficiency. Among the tested samples, the 5 wt% fly ash–TiO2 composite exhibited the highest adsorption capacity of 20.32 mg/g and achieved 76% FB dye removal. These results indicate that adsorption occurs primarily through monolayer coverage on a homogeneous surface, in agreement with the Langmuir isotherm, and governed by pseudo-first-order kinetics. Under UV irradiation, the same 5wt% fly ash–TiO2 composite reached a maximum photocatalytic degradation of 88% after 180 minutes, following pseudo-first-order kinetics. The catalyst demonstrated excellent reusability, maintaining its dye removal performance consistent over five consecutive cycles. Chapter-3 In this study, copper (Cu) photo-deposited fly ash-TiO2 composites (FT-Cu0.5-2) with Cu content ranging from 0.5 to 2wt% were synthesized to evaluate their adsorption and photocatalytic activity toward the photodegradation of fuchsin blue (FB) dye under visible light as well as natural sunlight. Structural characterization was performed using X-ray diffraction (XRD) and diffuse reflectance spectroscopy (DRS), while morphological and surface chemical analyses were carried out through high-resolution transmission electron microscopy (HR-TEM), X-ray photoelectron spectroscopy (XPS), and N₂ adsorption Brunauer-Emmett-Teller (BET) analysis. These confirmed the successful fabrication of fly ash-TiO2 (FT) and Cu-modified composites (FT-Cu0.5-2). Copper nanoparticles, with sizes in the range between 7 and 17 nm, were uniformly distributed on the FT composite surface. The impact of various adsorption parameters, including FB dye concentration, adsorbent dose, solution pH, and contact duration, was systematically investigated. Following 180 minutes of adsorption in the dark, the 1wt% Cu-loaded FT composite (FT-Cu1) showed the highest dye removal efficiency of 77% and fitted well to the Langmuir adsorption model. A notable enhancement in photocatalytic activity was observed for FT-Cu1, which achieved 92% FB degradation under sunlight and 94% under visible light, compared to the unmodified FT catalyst with only 68% and 71% removal, respectively. This enhancement in removal efficiency is attributed to the synergistic interaction between Cu, fly ash, and TiO2 components. The presence of Cu improved the efficient separation of photogenerated charge carriers and expanded visible light absorption by introducing intermediate energy states within the TiO2 bandgap. The degradation pathway of FB dye was elucidated via trapping experiments using hole scavengers and detection of intermediate species through High-Resolution Mass Spectrometry (HRMS). Additionally, the FT-Cu composite exhibited strong photostability and could be reused effectively, maintaining approximately 83% degradation efficiency after five consecutive cycles, demonstrating its potential for sustainable treatment of organic contaminants. Chapter-4 In this work, copper photo-deposited fly ash–TiO₂ (FT-Cu1) composites were modified with ZSM-5 zeolite at loadings of 1%, 3%, and 5% by weight, designated as 1ZFT-Cu1, 3ZFT-Cu1, and 5ZFT-Cu1, respectively. These composites were investigated for their capability to adsorb and photo-catalytically degrade crystal violet (CV) dye under visible and solar light exposure. Characterization techniques, including UV-Vis diffuse reflectance spectroscopy (DRS), field emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), and BET surface area analysis, revealed that the addition of ZSM-5 enhanced crystallinity, minimized particle aggregation, and increased visible light absorption by the composites. Among the samples, the 3wt% ZSM-5-loaded composite (3ZFT-Cu1) exhibited the best photocatalytic performance, achieving dye removal efficiencies of 98% under visible light and 95% under solar irradiation, using a catalyst dosage of 5 mg, initial dye concentration of 5 mg/L, a contact time of 180 minutes, and solution pH 9. The adsorption process fitted well with the Freundlich isotherm model, indicating multilayer adsorption, while the degradation kinetics followed a pseudo-first-order rate. The superior activity is credited to the synergistic interaction of copper doping, the porous structure of ZSM-5, and the fly ash support, which collectively enhanced light absorption and dye uptake. The 3ZFT-Cu1 composite also showed commendable stability, retaining 84% of its degradation efficiency after five cycles of reuse. Free radical trapping studies using hole scavengers elucidated the photocatalytic degradation pathway of CV dye, highlighting the composite’s effectiveness under visible light for potential wastewater treatment applications
Synthesis and Bioactivity of Selenium Nanoparticles Stabilized by Biocompatible Agents
(2026-06-01) Anmol; Prakash, Ranjana; Prakash, N. Tejo
In recent past, the domain of nanobiotechnology has progressively transitioned towards the creation of eco-friendly, biologically inspired techniques for nanoparticle production, focusing on biocompatible and ecologically safe procedures. Endophytic fungi are prolific makers of secondary metabolites and exopolysaccharides (EPS), both of which are significant for applications such as nanoparticle fabrication and the identification of bioactive compounds. The presented research work was aimed to investigate the biofunctionalization potential of secondary metabolites that were extracted from an endophytic fungal source. The isolation and antimicrobial screening were done of fungal isolates obtained from a plant source, Nerium oleander, commonly known as the Ganer plant. Upon the basis of antimicrobial screening of the fungal extracts, one of the isolates showing good antimicrobial potential was selected for further studies, i.e., NL(C). Following the morphological and molecular identification, the strain was observed to be Nigrospora spp. Moving forward, the fungal strain’s secondary metabolites, viz., fungal extract (NL(C)) and exopolysaccharide (EPS), were employed for the stabilization of selenium nanoparticles (SeNPs). Selenium nanoparticles have garnered significant interest in the last decade for their multifunctional uses in medicinal, environmental, and industrial fields. The study aimed at the green production of selenium nanoparticles utilizing endophytic fungal extracts (NL(C)) and exopolysaccharides (EPS). The study demonstrates a biological approach that effectively facilitates the synthesis and stabilization of SeNPs with the help of secondary metabolites, i.e., fungal extract rich in phenolic and flavonoids, which was obtained from endophytic fungi Nigrospora spp. termed as NL(C)-SeNPs. The nanoparticles formed were characterized via various techniques i.e., UV- visible spectroscopy, FTIR, DLS, and TEM. The synthesized NL(C)-SeNPs were spherical with a size of 55 ± 7.0 nm. These capped SeNPs (NL(C)-SeNPs) showed prominent bioactivity in terms of in-vitro anti-oxidant properties and anti-microbial activity on Escherichia coli, Enterobacter faecalis, and Staphylococcus aureus and antifungal activity on Aspergillus niger and Fusarium laterium. The results indicated NL(C)-SeNPs portray enhanced anti-oxidant and anti-microbial activity in a dose-dependent manner. Apart from their antimicrobial efficacy NL(C)-SeNPs was also successful in showing cell cytotoxic effect against HepG2 cells. In the second stage, of this study, green synthesis was obtained by using EPS extracted from the same strain N. guilinensis. The primary objective of this work was to investigate the synthesis and the bioactivity of SeNPs encapsulated with exopolysaccharide (EPS). The EPS. was mainly composed of 395 ± 13.20 mg/g carbohydrate and 121 ± 3.21 mg/g protein, the following moiety was used for surface stabilization of selenium nanoparticles (SeNPs). Bioactive SeNPs i.e., EPS-SeNPs. with an average size of 43.7 ± 13.7 nm were successfully synthesized. The antibacterial bioactivity of EPS-SeNPs was seen to be showing inhibition against Gram-positive bacteria, viz., Bacillus subtilis, Staphylococcus aureus, and Enterococcus faecalis, as well as Gram-negative bacteria, such as Escherichia coli and Salmonella enterica. In addition, the study also demonstrated antifungal activity against Alternaria alternata, Fusarium laterium, and Aspergillus niger. The cytotoxic activity of synthesized EPS-SeNPs exhibited a dose-dependent response against liver carcinoma cell lines, i.e., the HepG2. Upon juxtaposition, it was observed that although both the SeNPs are showing broad spectrum activity, yet EPS-SeNPs was shown to be more bio-actively potent than NL(C)-SeNPs. Additionally, these findings also support the hypothesis that these nanoparticles hold potential as an emerging material in the field of therapeutics. The synthesized EPS-SeNPs were converted into a functional material to improve the antibacterial performance of commercial gauze textiles. The challenge of bacterial contamination, which triggers an immune response, remains a significant hurdle in the biomedical field. As the conventional wound dressings lack antimicrobial efficacy, to enhancement of the antibacterial activity of dressing material was considered with the help of EPS-SeNPs, which may indirectly support wound healing. This study explored the use of exopolymeric substance-capped selenium nanoparticles (EPS-SeNPs) to enhance the antibacterial properties of cotton gauze. The modification of the gauze involved using chitosan as an adhesive agent to improve the deposition of EPS-SeNPs. The resulting functionalized gauze, termed EPS-SeNPs@CH_CG, was further analysed using physicochemical techniques such as XRD, FTIR, and FE-SEM. This functionalized gauze exhibited both anti-adhesive and bactericidal properties against Escherichia coli and Staphylococcus aureus. A prolonged antibacterial effect was also observed to be facilitated by the sustained release of selenium from the gauze. This study underscores the potential of EPS-SeNPs@CH_CG-functionalized cotton gauze for anti-microbial enhancement, which can be an asset for biomedical applications.
Topological semimetallic states with magnetic order: electronic states and collective excitations
(2026-05-28) Garima; Singh, Dheeraj Kumar
The discovery of linear band crossings at the Fermi level in graphene, protected by symmetry and topology, marked a transformative milestone in condensed matter physics. This novel quantum phase, termed the topological semimetal (TSM), has catalyzed extensive exploration in a wide array of material systems. Characterized by exotic and robust electronic properties, topological semimetals have opened new frontiers in next-generation electronic and spintronic technologies, enabling the manipulation of multiple degrees of freedom in a fundamentally new manner. Among various classes, Dirac and Weyl semimetals have emerged as key representatives, where the protection and breaking of fundamental symmetries—such as time-reversal and inversion—govern the emergence of Dirac or Weyl points. While Dirac semimetals require these symmetries (or sometimes, non-symmorphic lattice symmetries) to protect the four-fold degenerate Dirac points, Weyl semimetals arise when either symmetry is broken, resulting in pairs of Weyl nodes carrying opposite topological charges (Chern numbers). Although substantial focus has been given to three-dimensional semimetals, their two-dimensional counterparts have garnered increasing attention due to promising potential for miniaturized device applications. Notably, magnetic monolayers like FeSe and TaCoTe2 have been proposed as candidates to host two-dimensional Dirac fermions. This thesis explores the emergence and tunability of topological semimetallic phases within two-dimensional magnetically ordered systems. The first system considered is the spin-density wave (SDW) state in iron pnictides, which hosts Dirac-like features near the Fermi level. Experimentally observed metallic SDW state dictates the presence of additional pockets at the Fermi level. However, no attempt has been made in exploring the possibility of Dirac points at the Fermi level. We demonstrate that the Dirac points in this phase can be brought precisely to the Fermi level by tuning the orbital splitting between the dxz and dyz orbitals of iron. This tuning simultaneously suppresses non-Dirac Fermi pockets, stabilizing a Dirac semimetallic state with (π, 0) SDW state. The orbital character and slopes of bands forming the Dirac cone are shown to be key parameters in controlling this behavior. Additionally, by eliminating second-neighbor intraorbital hopping, we reveal a perfectly nested (π, π) ordered phase in a two-orbital Hubbard model, analyze the semimetallic state, and discuss its topological characteristics. The second system involves an antiferromagnetically (AFM) ordered state with Rashba-type spin-orbit coupling, where a Dirac semimetallic phase is realized under specific symmetry constraints on magnetic moment orientation using the Rashba- Hubbard model. Upon introducing an in-plane magnetic field like term aligned with the moment direction, Dirac points split into Weyl points, thereby realizing a Weyl semimetallic phase. Subsequently, we also investigate collective excitations using two primary probes: quasiparticle interference and optical conductivity. These tools elucidate the interplay between correlations, symmetry, and band topology in the ordered systems, and thereby provide insights into the possible anisotropic electronic states. The research work presented in the thesis is organized and structured in the form of seven chapters, which are briefly described as follows: i) Chapter 1 introduces the fundamental concepts of topology in condensed matter physics, reviews the development of topological insulators and semimetals, and outlines the two magnetically ordered 2D systems that form the focus of this thesis. ii) Chapter 2 develops the theoretical framework, employing the Hubbard model for systems with broken time-reversal (T ) and inversion (P) symmetries. It demonstrates how Dirac and Weyl semimetallic phases emerge under specific symmetry constraints and external tuning in an antiferromagnetically ordered non-symmorphic lattice. Topological invariants (Chern numbers) and edge-state dispersions are computed to confirm non-trivial band topology. iii) Chapter 3 examines collective excitations in AFM–TSM phases within a nonsymmorphic crystal, focusing on optical conductivity and quasiparticle interference for both magnetic and non-magnetic impurities, revealing strong anisotropy in the electronic responses. iv) Chapter 4 addresses the realization of a Dirac semimetallic phase in a striped (π, 0) SDW order within a multi-orbital Hubbard model. By tuning the orbital splitting δ between dxz and dyz orbitals, Dirac points are brought exactly to the Fermi level, eliminating additional band crossings. Edge-state dispersions for ribbons with varying orientations and chain parity are also analyzed. v) Chapter 5 provides a detailed analysis of optical conductivity and quasiparticle excitation spectra in the semimetallic SDW phase, demonstrating that Dirac cones near the Fermi level can play a very significant role in the origin of anisotropic transport and one-dimensional QPI patterns. vi) Chapter 6 explores the semimetallic state in iron-based superconductors with the checkerboard-type antiferrromagnetic order, which emerges upon suppression of second-neighbor intraorbital hopping in the minimal two-orbital model of iron pnictides. Fermi-surface reconstruction collapses the pockets into Dirac points with equal orbital contributions but anisotropic. Analytical conditions for Dirac point formation and the evolution of edge states with interaction strength are derived. Furthermore, quasiparticle interference as well as optical conductivity are also explored. vii) Chapter 7 summarizes the principal findings and outlines potential directions for future research in the field of topological quantum materials.
Digital Marketing and Consumer Behavior Towards Purchase Decisions: A Study With Reference To Punjab and Haryana
(2026-05-27) Kaur, Sumanpreet; Sharma, Rakesh Kumar
Digital marketing has become a cost-effective strategy amidst the rapid expansion of online platforms, particularly among digitally native consumers. Anchored in an integrated (Unified Theory of Acceptance and Use of Technology-Theory of Planned Behaviour) UTAUT–TPB cultural framework, this study examines how behavioural and socio-cultural factors, mediated through Digital Marketing Channels (DMCs), influence consumer purchase intentions. Data was collected via a self-designed questionnaire from 600 respondents using Likert scale options, across Punjab and Haryana and analysed using regression analysis, ANOVA, and Partial Least Squares Structural Equation Modelling (PLS-SEM). The results reveal that modern consumer behaviour is predominantly shaped by individual financial circumstances and pragmatic concerns rather than external social or cultural pressures. Although digital marketing channels do not directly affect purchase intentions, they exert a significant indirect influence through enhanced product preference and information search behaviours. Social and cultural factors emerged as robust predictors of purchase intention (path coefficient = 0.490, t = 14.847, p < 0.01), while information search and evaluation also showed a significant positive association (path coefficient = 0.454, t = 12.617, p < 0.01). Product preference notably mediated the relationship between digital marketing channels and purchase intentions, amplifying the effect (path coefficient = 0.151, t = 4.133, p < 0.01), with a significant direct association between digital marketing channels and product preference (path coefficient =0.701, t=34.300, p < 0.01). Theoretically, this research extends technology acceptance models by integrating attitudinal, normative, and cultural constructs within UTAUT and TPB frameworks and articulating a theory of change (ToC) logic model tailored for digital commerce in emerging markets. Practically, the study offers actionable insights for marketers to optimize digital channel strategies within rapidly evolving digital ecosystems.
Performance Improvement of Generalized Frequency Division Multiplexing based 5G Communication System
(2026-05-21) Kaur, Manpreet; Joshi, Hem Dutt
The current fifth generation (5G) technology has brought a paradigm shift in wireless communication systems, offering unprecedented speeds, ultra-low latency, massive device connectivity, and remarkable network capacity. While 5G is still in its early stages of deployment and expansion, researchers and industry experts are already contemplating the requirements, challenges, and opportunities for ”beyond 5G” (B5G) communication. The development of B5G is gaining attention as the global community seeks to redefine wireless communication systems for the future. The diverse requirements of the B5G standards include data rates of 1 Gb/s, device density of up to 107 devices/km2, high mobility of up to 1000 km/h, and latency in the range of 10−100 μs. To cater for the evolving requirements of future communication systems many current and future standards have adopted multicarrier techniques which include both orthogonal (i.e., Orthogonal Frequency Division Multiplexing (OFDM) and Universal Filtered Multicarrier (UFMC) and non-orthogonal (i.e., Generalized Frequency Division Multiplexing (GFDM), Orthogonal Time Frequency Space (OTFS), and Filter Bank Multicarrier (FBMC) techniques. GFDM has gained attention as a non-orthogonal waveform with several advantageous features, making it a viable choice for future generations (like B5G, 6G). These advantages include its flexible structure, resilience against frequency selective fading, minimal OOB emissions, high spectral efficiency attributed to reduced CP overhead, and low PAPR. This dissertation aims to enhance the performance of GFDM-based 5G communication systems. It includes a performance analysis of the GFDM system over mmWave channels, particularly the FTR channel. The impact of channel impairments, such as the unavailability of perfect channel state information (CSI), on the performance of GFDM systems is also presented. The second contribution of this thesis is the introduction of a novel timing synchronization algorithm, which significantly improves the performance of GFDM systems. This improvement leads to increased reliability in data transmission, a crucial aspect of the B5G system. The third contribution involves a novel filter design method based on the discrete biorthogonality condition and Wigner Distribution (WD). The proposed filter enhances the GFDM system’s performance in terms of both Symbol Error Rate (SER) and Power Spectral Density (PSD). The analytical results derived from the proposed expressions are verified through Monte Carlo simulations. In some cases, numerical integration is required over finite limits, which can be easily implemented with negligible error using tools such as MATLAB and Mathematica.