Saxena, Deepak Kumar

In order to get the nanocomposite of silver-doped resin, we treated aniline with dil. HCl and formaldehyde solution (40%) with constant stirring and got polymer metal complex, then we calcinated this complex at 9000 C in Muffle furnace for 45 min. The structure and chemical properties of Ag-doped resin were confirmed byIH NMR and IR spectroscopic techniques. The morphological study of this decomposed polymer metal nanocomposite had been done by SEM, AFM and TEM. Polymer nanocomposites of metals represent an important field for fundamental studies which offer a wide range of engineering and biomedical applications. The prepared polymer Ag-doped aniline formaldehyde nanocomposites are widely used as photosensitive components, catalysts, photo-catalyst and in surface enhanced Raman spectroscopy as well as chemical analysis.

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.

In this report, our main focus is to introduce a set of one-dimensional (1D) NMR methods based on chemical shift, relaxation, and magnetization transfer, namely, NOE and chemical exchange involving selective pulse excitation to study the solution dynamics of drug in free and encapsulated state within polymeric microsphere. In this regard 5-fluorouracil (5-FU) loaded poly lactic-co-glycolic acid (PLGA) microspheres are prepared as model system via standard water-in-oil-in-water emulsification method. One-dimensional 1H and 19F nuclear magnetic resonance (NMR) spectra of 5-FU in presence of PLGA microspheres presented a significant change in linewidth and relaxation rates compared with free 5-FU confirming encapsulation. Furthermore, loss of coupling pattern in 1H and 19F NMR of PLGA encapsulated 5-FU as compared with free 5-FU suggests an enhanced –NH and –H2O protons exchange dynamics in the interior of the microsphere indicating hydrated microsphere cavity. Quantification of exchange dynamics in case of free and PLGA-encapsulated 5-FU was attempted employing 1D selective NOESY and 1D multiply selective inversion recovery experiments. Analysis of the exchange rates confirmed existence of more than one kind of water population within the cavity as mentioned in an earlier solid state NMR report.

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.

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.

Copper nanoparticles have been synthesized by simple chemical precipitation method and showed versatile thermal, mechanical, magnetic and electrical properties. Copper nanoparticles have been synthesized in following two steps, in step-1st, synthesis of polymer metal complex and in 2nd step formation of copper nanoparticles. Polymer metal complex is confirmed by IR spectroscopy and XRD confirmed by size of nanoparticles is 13.13 nm, Crystal system is orthorhombic, Bravais lattice is primitive, space group pccn(56) and 28 = 42.045. Thermal stability is confirmed by TGA and the compound is very slow (rate of 3 %) loss in weight per 100°C increase in the temperature up to 900°C. It shows that 70 % thermal stability of the compound at 900°C. Endothermic nature of copper nanoparticles has been confirmed by DSC.

Monoclinic chromium nanoparticleswere synthesized by thermal decomposition method using CrCl3 as precursor. It is a simple, fast and effective method.The synthesized nanoparticles were analyzed by infrared spectroscopy (IR) and nuclear magnetic resonance spectroscopy (NMR), scanning electron microscopy (SEM), and X- ray diffraction (XRD)techniques. The SEM analysis confirms the spherical shape morphology and presence of stress on the surface of the nanoparticles. The XRD analysis proves that the crystal structure ismonoclinic and the size of nanoparticles is 45.20 nm.

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.

Spectroelectrochemicalinvestigation of racemic alanine on poly crystalline metal surfaces was studied in 1M LiClO4 medium, to achieve cost effective separation of biologically important molecules from the racemic mixture. Analysis of the FTIR spectrum of racemic alanine in 1M LiClO4 indicated degradation of the same. Upon prolonged exposure in LiClO4, byproducts from degradation of alanine increasedin concentration as also observed from UV-Vis spectroscopy. Cyclic Voltammetry studies unraveled different adsorption behaviors on different metal surfaces for the racemic and the enantiomeric solution of alanine. Further FTIR analysis of the alanine solution after Cyclic Voltammetry revealed possible presence of cyanide (-C=N) and terminal alkyne as byproducts. As predicted by Monte Carlo simulations earlier, Circular Dichroism implied the dextro rotation of the racemic alanine solution after Cyclic Voltammetry. These results support the preferential adsorption of L-alanine over D-alanine from racemic mixture that could be attributed to the umbrella inversion of the molecule after adsorption on the metal surface in presence of applied electric field in the LiClO4 environment. A plausible mechanism for the formation of terminal alkyne and - C=N byproducts had also been attempted.

The prime focus of the present study is to employ NMR relaxation measurement to address the intermolecular interactions, as well as motional dynamics, of drugs, viz., paracetamol and aspirin, encapsulated within the β-cyclodextrin (β-CD) cavity. In this report, we have attempted to demonstrate the applicability of nonselective (R1ns), selective (R1se), and bi-selective (R1bs) spin-lattice relaxation rates to infer dynamical parameters, for example, the molecular rotational correlation times (τc) and cross-relaxation rates (σij) of the encapsulated drugs. Molecular rotational correlation times of the free drugs were calculated using the selective relaxation rate in the fast molecular motion time regime (ωH2τc2 ≪ 1 and R1ns/R1se ≈ 1.500), whereas that of the 1:1 complexed drugs were found from the ratio of R1ns/R1se in the intermediate motion time regime (ωH2τc2 ∼ 1 and R1ns/R1se ≈ 1.054), and these values were compared with each other to confirm the formation of inclusion complexes. Furthermore, the cross-relaxation rates were used to evaluate the intermolecular proton distances. Also, density functional theory calculations were performed to determine the minimum energy geometry of the inclusion complexes and the results compared with those from experiments. The report, thus, presents the possibility of utilizing NMR relaxation data, a more cost-effective experiment, to calculate internuclear distances in the case of drug-supramolecule complexes that are generally obtained by extremely time consuming two-dimensional nuclear Overhauser enhancement-based methods. A plausible mode of insertion of the drug molecules into the β-CD cavity has also been described based on experimental NMR relaxation data analysis.