http://localhost:8081/jspui/handle/123456789/24 2026-05-07T01:48:10Z http://localhost:8081/jspui/handle/123456789/20440 Title: FUNCTIONALIZED PHOTOLUMINESCENT CARBON DOTS AND THEIR NANOCOMPOSITES WITH METAL OXIDE NANOPARTICLES: APPLICATIONS IN SENSING AND PHOTOCATALYSIS Authors: Cilamkoti, Vatsala Abstract: The thesis comprises of 7 chapters and it deals with developing suitable photoluminescence (PL) probes for detection of potential water pollutants and to develop efficient photocatalyst for sunlight driven photocatalytic degradation of emerging contaminants. On a broader perspective, the goal of the thesis is to develop a sustainable approach to ensure clean water for improving the quality of life in the earth. The thesis comprises of three main verticals, (a) discussing the fundamental concepts involved in carbon dot based PL probe for detection of pollutants and the semiconductor metal oxides as photocatalyst for degradation of the pollutants; (b) literature review in the above areas to identify the research gap and research objectives; and (c) developing suitable functionalized carbon dots as PL probe and p-type semiconductor based metal oxide nanocomposites with some of these functionalized carbon dots as solar photocatalyst for degradation of some selected water pollutants. In view of this, two batches of functionalized carbon dots are prepared using different carbon precursors, e.g., (i) sodium citrate, and (ii) 1,4 Butanediol, and both are functionalized by siloxane group. The first batch is prepared by hydrothermal heating of sodium citrate and (3-Aminopropyl)triethoxysilane (APTES) in an autoclave at 170 ºC for 12 h. The second batch is prepared by solvothermal method by heating 1,4-Butanediol and APTES in an autoclave at 170 ◦C for 12 h. These two batches are named as N-SiO2@CD1 and N-SiO2@CD2 respectively. The TEM studies revealed formation of network structure of polysiloxane with carbon dots of sizes less than 10 nm in them. Both exhibited bluish PL corresponding to emission wavelength of λ= 440 nm and 443 nm, respectively. The PL quantum yield of N-SiO2@CD1 is 23.1% and N-SiO2@CD2 is 27.0% measured against quinine sulphate. The obtained PLQY for both the batches are found to be higher than several of the nitrogen doped carbon dots reported in literature. Furthermore, the PLQY of the batch prepared with butanediol and APTES by solvothermal method is 10% higher than the batch prepared by hydrothermal method using sodium citrate and APTES. The chemical composition of both the batches has been studied by Fourier transformed infrared spectroscopy (FT-IR) and by X-ray photoelectron spectroscopy (XPS). Both the batches of N-SiO2@CD1 and N-SiO2@CD2 exhibited quantitative PL quenching by Cr(VI) and satisfied the Stern-Volmer relation. The linear region of PL quenching is found to be at least in the range of 1-75 μM. The limit of detection (LOD) of Cr(VI) by N-SiO2@CD1 and N-SiO2@CD2 are determined as 0.78 μM and 0.20 μM, respectively. Notably, the batch that exhibited higher PLQY, correspond to lesser LOD. In addition to Cr(VI), the better performing PL probe, i.e., N-SiO2@CD2 also exhibited linear PL quenching when treated with another water pollutant, e.g., 4-nitrophenol (4-NP), in the region 0.3 and 200 µM. The LOD for 4-NP detection is found to be much better (i.e., 0.07 µM) than iii that of Cr(VI). The PL quenching mechanism has been attributed to ground state complexation. The detection of Cr(VI) and 4-NP are not interfered by the common cations and anions that are present in water. The detection of 4-NP is mildly interfered by structural analogues of other nitrophenols. The feasibility of using N-SiO2@CD1 and N-SiO2@CD2 as probe for detecting Cr(VI) and 4-NP has been tested in real samples by estimating the recovery concentration analysis of spiked concentration in the real water samples. Furthermore, N-SiO2@CD2 has been used for imaging the lung cancer cells (A549 cells). 2024-07-01T00:00:00Z http://localhost:8081/jspui/handle/123456789/20325 Title: PHOTOINDUCED ORGANIC TRANSFORMATIONS OF OLEFINS AND CARBONYL COMPOUNDS Authors: Das, Anupam Abstract: There are seven chapters in the thesis. The purpose and scope of the effort are introduced in the first chapter. Unsaturated hydrocarbons containing at least one double bond between carbon atoms are known as alkenes. They are adaptable building blocks in the synthesis of organic compounds because of their reactivity, which enables them to take part in a variety of reactions. Carbene and carbenoid reactions, radical reactions, olefin metathesis, addition reactions, and olefin metathesis are a few important reactions involving alkenes. Similar to this, the reactivity of the carbonyl group makes carbonyl compounds very helpful in the synthesis of organic molecules. Nucleophilic addition processes, redox reactions, aldol reactions, acylation reactions, alkene production reactions, etc. are a few important reactions involving ketones. Under photoinduced circumstances, these two synthons have a great deal of potential to produce significant organic derivatives. Alkenes and carbonyls are discussed briefly in Chapter 2 as the most fundamental and practical synthons used to produce atom- and step-efficient heterocyclic compounds, which are essential ingredients in many pharmaceuticals, natural products, and significant intermediates in modern synthetic chemistry. Furthermore, because of their many physical, chemical, and biological characteristics, nitrogen-based motifs have grown to be crucial to material and pharmaceutical chemistry. The nitrogen scaffold has been decorated with numerous functional groups using novel synthetic techniques and procedures. It is highly intriguing to create a novel photo-induced catalysis approach that can be applied to chemical synthesis in a variety of ways. It is feasible to convert light into chemical energy using this state-of-the-art technology. Due to its low price and environmental friendliness, it is a good and sustainable substitute for traditional catalysis. Since nitrogen scaffolds are present in > 50% of all medicinal and functional materials, creating an effective synthetic process employing a photo-induced approach has become a valuable tool in recent years. This study focuses on some of the most significant recent advances in the subject, including the clarification of light's effects, the encouragement of fundamental-coupling stages, the selective functionalization of amines, the employment of complementary mechanistic concepts, and synthetic applications. In Chapter 3, two-step, one-pot, light-promoted syntheses of imidazo[1,2-a]pyridines and quinoxalines from alkynes and alkenes, respectively, are discussed. The transformations take place when acetonitrile and water are exposed to UV LED fluorescent black light (380–390 nm), which causes the synthesis of α,α′-dibromo ketones or α-bromo ketones. There is no need for a sensitizer, catalyst, or additives with this approach. This one-pot two-step procedure, which offers broad functional group tolerance, is a new addition to the synthetic methods available for quinoxaline and imidazopyridine derivatives via light-promoted intramolecular through-space charge transfer from amine center to a carbonyl group. Knoevenagel condensation is widely used in organic synthetic chemistry and several reaction conditions have been demonstrated. These reactions in a neutral medium are challenging. In chapter 4, we present a sustainable and greener method for Knoevenagel condensation reaction between carbonyl compounds (both aldehydes and ketones) and active methylene compounds using Rose Bengal as a photosensitizer in an aqueous medium. This protocol works smoothly for aromatic aldehydes and ketones containing both electron-donating and electron-withdrawing substituents. It is a common procedure in synthetic organic chemistry to deconstruct alkenes into their carbonyl derivatives, and numerous reaction conditions for electron-rich and unconjugated alkenes have been established. However, such conjugated and electron-deficient alkene reactions are quite difficult. In chapter 5, we showed that under milder and more environmentally friendly circumstances, light-promoted water-mediated NBS photoinitiated cleavage of electron-deficient conjugated alkenes may occur. This approach is also shown to include a deprotection phase for carbonyl groups. This method operates in an aqueous medium with a broad functional group tolerance and good regioselectivity at room temperature. The visible-light-induced catalyst-free condition for thiol self- and cross-coupling reactions in an ambient environment has been established in chapter 6. Further, the synthesis of β-hydroxysulfides is accomplished under very mild conditions involving the formation of an electron donor-acceptor (EDA) complex between a disulfide and an alkene. However, the direct reaction of thiol with alkene via the formation of a thiol-oxygen co-oxidation (TOCO) complex failed to produce the desired compounds in high yields. The protocol was successful with several aryl and alkyl thiols for the formation of disulfides. However, the formation of β-hydroxysulfides required an aromatic unit on the disulfide fragment, which supports the formation of the EDA complex during the course of the reaction. The approaches presented in this paper for the coupling reaction of thiols and the synthesis of β-hydroxysulfides are unique and do not require toxic organic or metal catalysts. An overview of the research on treating alkenes with hydroxyl radical species when other electron-deficient radical species, such as bromines and thiols, are present is given in chapter 7. This chapter compares the reactivity of different alkene species in the presence of similar radical initiators. For example, alkenes with electron-donating and neutral functional groups in the terminal position or alkenes with electron-withdrawing groups in the terminal position exhibit different reactivity. 2024-02-01T00:00:00Z http://localhost:8081/jspui/handle/123456789/20314 Title: PRESSURE EFFECT ON SPIN, ELECTRONIC, AND THERMAL TRANSPORT IN TERNARY INTERMETALLICS Authors: Chaudhary, Vikrant Abstract: The field of materials science has advanced significantly with the inception of computational technologies. Currently, more materials are designed on computers than those grown in laboratories. Designing and studying different aspects of a material using a computer helps us decide whether the material should be grown in laboratories. This process helps decrease lab waste and speeds up the discovery of novel materials. Using a computer, we can predict the possibility of synthesis and various properties of materials under varying external conditions. This thesis focuses on the computational investigation of structural, electronic, magnetic, topological, spin and current transport, and thermoelectric transport properties of ternary intermetallic compounds under strain and pressure conditions. We selected compounds from three different crystal classes for a thorough understanding of the effect of pressure on various properties. The materials that we studied are half-Heusler CoFeGe, hexagonal SrAgP, and tetragonal quasi two-dimensional KMgSb. The CoFeGe is studied for spin and current transport, SrAgP for topological and thermoelectric transport, and van der Waals KMgSb for thermal and electronic transport properties. These studies are presented in three different chapters. CoFeGe: Spintronics is an emerging form of electronics based on the electrons’ spin degree of freedom for which materials with robust half-metallic ferromagnet character are very attractive. Here, we determine the structural stability, electronic, magnetic, and mechanical properties of the half-Heusler (hH) compound CoFeGe, in particular in its cubic form. The first-principles calculations suggest that the electronic structure is robust with 100% spin polarization at the Fermi level under hydrostatic pressure and uni-axial strain. Both the longitudinal and Hall current polarization are calculated and the longitudinal current polarization (PL) is found to be > 99% and extremely robust under uniform pressure and uni-axial strain. The anomalous Hall conductivity and spin Hall conductivity of hH cubic CoFeGe (c-CoFeGe) are found to be ∼ −100 S/cm and ∼ 39 ¯h/e S/cm, respectively. Moreover, the Curie temperature of the alloy is calculated to be ∼ 524 K with a 3 μB magnetic moment. Lastly, the calculated mechanical properties indicate that c-CoFeGe is ductile and mechanically stable with a bulk modulus of ≈154 GPa. Overall, this analysis reveals that cubic CoFeGe is a robust half-metallic ferromagnet and an interesting material for spintronics applications. 2023-12-01T00:00:00Z http://localhost:8081/jspui/handle/123456789/20300 Title: BIOPHYSICAL STUDIES OF DIAMIDO ANTHRAQUINONE LIGAND-G-QUADRUPLEX DNA INTERACTIONS Authors: Anjana Abstract: Anthraquinones (9,10-dioxoanthracenes) represent a significant category of natural and synthetic compounds with broad uses. In addition to being employed as dyes, anthraquinone variants have been utilized for ages in medical implications, such as for laxative purposes, as well as for their antimicrobial and anti-inflammatory properties. Current applications of anthraquinone include arthritis, multiple sclerosis, and cancer. For centuries, anthraquinones have served as a privileged chemical structure having anthraquinone moiety, which work as a central framework for various anti-cancer drugs. Nevertheless, the appearance of drug-resistant cancers necessitates the innovation of fresh anticancer ligands/drugs. In recent years, there has been a rapid escalation in research efforts aimed at generating novel anthraquinone-derived compounds. These compounds serve as fundamental chemical blueprints, enabling structural modifications that lead to the creation of innovative anthraquinone based compounds with substantial potential as effective anticancer agents. In terms of mechanism, the majority of the compounds derived from anthraquinone hinder the advancement of cancer by focusing on crucial cellular proteins. Initially, anthraquinone ligands worked on inhibiting topoisomerases, closed circular DNA, duplex DNA, and triplex DNA but the current research attention centered on human telomeric sequences containing G-quadruplex Structures. G-quadruplex structure formation is associated with telomerase dysfunction and Telomerase enzyme is found active in 85% of cancer cells, and consequently it became an attractive target of anticancer therapeutics. Several types of anthraquinone derivatives have been synthesized and applied to several types of cancer such as leukemia, lymphoma, breast cancer, ovarian cancer and many more for more than two decades, to minimize the cytotoxicity of anthraquinone-based ligands/drugs. The researchers employed substitution methods to make new derivatives of anthraquinone bearing covalently linked different side chains at different positions (2-6, 2-7, 1-4, 1-5, 1-8) with some specific groups to enhance selectivity and specificity towards G-quadruplex DNA. Phillip J. Perry, Stephen Neidle and Huang et al, made a library of such compounds, in which some ligands scored high in anticancer therapeutics. The first anthraquinone derivative 2,6-amido anthraquinone documented, to successfully inhibit telomerase activity with IC50 = 23 μM (Telomerase assay) in cancer cells, was BSU-1051. It shows thermal stabilization (ΔTm) of the DNA by ~20 ⁰C stabilized the G-quadruplex DNA. The successful implication of such anthraquinone derivatives as anticancer drugs motivates us to work on these compounds. We synthesized 1,5-diamido anthraquinone derivatives and investigated through various spectroscopy techniques, UV-absorption, Fluorescence (steady state & lifetime), Circular Dichroism, thermal melting by using CD and Difference Scanning Calorimetry along with molecular modelling and biological assay (MTT) on breast cancer cell lines. Such a comprehensive study of these compounds was not reported earlier with two different G-quadruplex sequences HTel22 and wHTel26 in the presence of Na+ and K+ ions, respectively. We investigated the binding characteristics of a 1,5-diamide anthraquinone derivative against human telomere sequence d-[AGGG(TTAGGG)3] and with -TT- overhang at 5’ and 3’ terminals. The core DNA sequence d-[AGGG(TTAGGG)3] (HTel22) attains anti-parallel (basket) conformation in the presence of Na+ ions, whereas d-[AGGG(TTAGGG)3] with -TT-overhang (wHTel26) attains hybrid conformation (3+1) in presence of K+ ions. We got substantial results with these compounds which can work as anticancer agents in anticancer therapeutics. 2024-04-01T00:00:00Z