Pal, Samanwita

Graphene oxide (GO) exhibits very poor photoluminescence (PL) characteristics because of the nonradiative recombination of electron-hole pairs. One of the crucial approaches for the enhancement of the optical features of GO is functionalization. In this study, we present a novel catalyst-free, rapid, one-step, aqueous-phase synthetic approach using SELECTFLUOR under mild conditions that provide access to highly photoluminescent fluorinated graphene oxide (FGO) emitting in the visible region. Time-resolved fluorescence spectroscopy and femtosecond transient absorption spectroscopy revealed that the enhanced PL is due to the increased π* → π transition and weaker electron-phonon interactions in FGO. Most importantly, the structure and composition analyses using 19F NMR and X-ray photoelectron spectroscopy suggest that the C-F bond on the basal plane neighboring to the aromatic rings is the key factor behind the enhancement of the fluorescence of FGO. Identification of the underlying C-F bonding features behind the emergence of strong orange fluorescence will contribute immensely to the fundamental understanding of the structure and optical property relationship of FGO. Moreover, strong orange fluorescence remains stable in a solid thin film of FGO, which offers a unique solution-processable route toward the integration of FGO in solid-state optoelectronic devices.

Emeraldine Hydrochloride salt is coated on copper substrate and studied for hydrogen storage and hydrogen evolution reaction in 1 M NaOH. Phenomenological thermodynamic approach demonstrated elsewhere in conjunction with the cyclic voltammetry data is employed to calculate the solvent modified work function for polyaniline coated copper in alkaline medium as −0.65 eV. The solvated work function is in satisfactory agreement with the band gap difference of π−π* transition in emeraldine base and π- polaron transition in emeraldine salt ca −0.6 eV as reported in the literature. 13C and 1H NMR studies revealed that polyaniline undergoes switching between emeraldine salt and emeraldine base, before and after hydrogen evolution respectively. The volume of hydrogen evolved on polyaniline coated copper is 1.64 times than that on copper as demonstrated by Gas chromatography. Thus emeraldine salt, when stored in NaOH act as hydrogen storage medium and upon electrochemical perturbation can release hydrogen at controlled rate depending on the scan rate employed.

2-Mercaptobenzothiazole (MBT) complexes of Ag(I) and Au(III) were synthesized by wet chemical method. The structural, optical, 1HNMR, ICP – MS and electrochemical studies of the complexes were carried out. The TUNEL assay studies of Ag(I)MBT and Au(III)MBT complexes on A549 cell line indicated induced apoptosis in the cells. TUNEL assay showed 60% cell viability for Ag(I)MBT whereas 80% for Au(III)MBT. Thus Ag(I)MBT can induce cell apoptosis in cells at a higher rate than Au(III)MBT. Therefore these complexes studied here can be a viable option as anti – proliferating agent.

In the present study, we have tried to characterize the inclusion complex of Hexaflumuron (HFM) with ß-cyclodextrin (ß-CD) using 1H & 19F NMR experiments. HFM is a pesticide (anti-termite) belonging to benzoylphenylurea family that contains three classes of fluorine. Its' very low aqueous solubility can lead to facile accumulation in water or soil causing rapid poisoning of the environment. Therefore, elimination of HFM requires scavenging agents such as ß-CD that can encapsulate HFM resulting in better aqueous solubility. A significant change in 19F and 1H NMR chemical shift, 1H & 19F longitudinal (T1) and 19F transverse relaxation (T2) time was observed for HFM in the presence of CD that confirms HFM-CD association. Jobs Plot demonstrated that ß-CD was found to form 2:1 inclusion complex with HFM. Association constant was determined from chemical shift titration method using modified Benesi-Hildebrand plot. The present study for the first time provides an insight in understanding formulation of HFM in ß-CD enhancingthe solubility giving rise to a possible soil remediation method.

The present study aims at the development and characterization of zinc oxide (ZnO) nanoparticles as a carrier for various anti-cancerous drugs viz. 5-Fluorouracil (5-FU), Doxorubicin (DOX) and Daunorubicin (DNR). ZnO nanoparticles were prepared by standard precipitation method. The measurement of optical band gap using UV-Visible Diffuse Reflectance Spectroscopy (DRS) analysis reveals the lowering of ZnO band gap after the drug loading. Crystallite size of free and drug loaded ZnO nanoparticles were determined using X-ray Diffraction (XRD) analysis. The crystallite size of ZnO nanoparticles increases after the drug loading. Both the techniques confirm the adsorption of drug molecules on ZnO surface.

In the present study, we attempt to characterize fluorinated ligand-serum albumin interaction in solution by a set of one-dimensional 19F ligand-based experiments. In this regard, a model system diflunisal (DFL)-human serum albumin (HSA) has been chosen to benchmark the utility of 19F relaxation and diffusion-based experiments in deciphering ligand-protein interactions. Further, we extend the application of a similar set of 19F experiments to unravel the molecular interaction in an unexplored system of 2,6-difluorobenzoic acid (DFBA)-bovine serum albumin (BSA). Interaction analysis of DFBA-SA is of particular interest because DFBA is not only a stable metabolite of a number of pesticides but also used as the starting reagent of many fluorinated drugs. Observation of 19F-1H & 1H-1H saturation transfer difference effects confirmed binding of the ligands to SA. Further, these ligand-protein complexes were probed in terms of the dissociation constant (KD), number of binding sites (n), bound fraction of the ligand (Pb), the complex lifetime (Δres), and exchange rate (Kex). Although Carr-Purcell-Meiboom-Gill (CPMG)-based transverse relaxation and diffusion analysis quantified the former three quantities, the latter two were determined by the constant time fast pulsing CPMG method. Additionally, 19F competition binding experiments performed with well-characterized BSA site markers and DFBA indicated nonspecific binding of DFBA to BSA, whereas similar measurements in the case of HSA with DFL and DFBA revealed superior binding interaction of DFL with SA.

Serum Albumin is a major carrier protein and its binding with drugs is important to examine the change in pharmacokinetic properties due to interaction amongst drugs. In the present study we have attempted to understand the relevant drug-drug interaction (DDI) between two common drugs viz, paracetamol, an anti-inflammatory and fluorouracil, an anti-cancer drug. In-vitro spectroscopic methods viz., fluorescence quenching and UV-vis absorption have been employed for the drug-bovine serum albumin (BSA) complexes studies. The binding parameters and quenching constants have been determined for BSA-Paracetamol and BSA-5Fluorouracil complex according to literature models. It is also predicted from the quenching studies that BSA-5Fluorouracil is a stronger complex than BSA-Paracetamol. On the other hand paracetamol can alter binding affinity of 5Fluorouracil towards BSA. Hence it becomes clear that although the drugs could be administered simultaneously but they influence each other's binding with protein in a concentration dependent fashion. Further these results also indicate that availability of free 5Fluorouracil in blood may increase in presence of paracetamol.

Analysis of the interaction of pesticides and their metabolites with the cellular proteins has drawn considerable attention in past several years to understand the effect of pesticides on environment and mankind. In this study, we have investigated the binding interaction of Bovine Serum Albumin (BSA) with a widely used organophosphorous insecticide chlorpyrifos (CPF), and its stable metabolite, 3,5,6-trichloro-2-pyridinol (TCPy) to provide a comparative analysis of the two molecules by employing various spectroscopic techniques viz., UV–vis absorption, Circular Dichroism (CD), and Fluorescence spectroscopy. The fluorescence quenching studies of BSA emission in two different solvents viz., water and methanol in presence of CPF and TCPy have led to the revelation of several interesting facts about the pesticide-protein interaction. It has been found that both the molecules cause static quenching of BSA emission as seen from the Stern-Volmer constant (Ksv) irrespective of the solvent used for the analysis. While TCPy is a stronger quencher in water, it exhibits comparable quenching capacity with CPF in methanol. The solvent dependent differential binding interaction of the two molecules finally indicates possibility of diverse bio-distribution of the pesticides within human body. The UV–vis and CD spectra of BSA in presence of the test molecules have unravelled that the molecules formed ground state complex that are highly reversible in nature and have minimal effect on the protein secondary structure. Furthermore it is also understood that structural changes of BSA in presence of CPF is significantly higher compared to that in presence of TCPY.

Emeraldine salt of polyaniline-coated copper substrate was used as a cathode to study hydrogen evolution reaction in 1M H2SO4. Hydrogen evolution reaction in acidic medium followed Grotthus mechanism, where proton hops randomly on the surface of polyaniline. With Randles-Sevcik equation, the average value of diffusion coefficient for H+ on polyaniline was calculated to be 2.66 times higher than that in the literature data. This higher value explicitly supported the rapid diffusion of H+ on polyaniline surface from the bulk electrolyte solution. With the help of a phenomenological thermodynamic approach demonstrated elsewhere, the solvent-modified work function of polyaniline-coated copper in acidic medium was calculated. The plot of exchange current density versus solvent-modified work function of different metals and polyaniline-coated copper indicated that at lower work function polyaniline-coated copper showed higher exchange current density and the rate of hydrogen evolution was much higher on polyaniline-coated copper than on copper. This was further confirmed by gas chromatography, and 13C and 1H nuclear magnetic resonance studies supported the mechanism proposed. From linear sweep voltammetry analysis, it was observed that the total capacity of hydrogen stored on polyaniline-coated copper was approximately 1.85 times higher than that on copper.

Molecular aggregation frequently occurs during material synthesis, cellular processes, and drug delivery systems, often resulting in decreased performance and efficiency. One major reason for such aggregation in an aqueous solution is hydrophobicity. While the basic understanding of the aggregation process of hydrophobic molecules from a thermodynamic standpoint is known, the present literature lacks a connection between the aggregation kinetics and the molecular basis of hydrophobicity. This study explores how various fluorescent probes (rhodamine dyes) aggregate in an aqueous solution due to their hydrophobicity. The method employs a combination of modeling and characterization to comprehend the aggregation process by examining the nonbonded intermolecular interactions. The aggregation kinetics was analyzed by measuring the average diffusivity of the molecules using fluorescent correlation spectroscopy and NMR diffusion measurements. Through all-atom molecular dynamics (MD) simulations, it has been observed that the level of hydrophobicity is strongly correlated to the total number of hydrogen bonds between water molecules and dyes. In addition, the aggregation frequency of colliding species, which depends on the concentration, is inversely related to hydrogen bonding and the diffusivity of the molecules. This study of small molecules was applied to predict protein aggregation rates, demonstrating strong alignment with the existing literature. The study has also helped to identify and understand the concentration at which a hydrophobic molecule does not aggregate in an aqueous solution. The method developed here could help investigate the aggregation process and its root causes at the molecular level in aqueous systems to develop strategies to control it. © 2025 American Chemical Society.