Ziziphus mauritiana-derived nitrogen-doped biogenic carbon dots: Eco-friendly catalysts for dye degradation and antibacterial applications.

In this study, the naturally available Ziziphus Mauritiana was used as a bioresource for the preparation of bifunctional nitrogen doped carbon dots (N-CDs). The doping of nitrogen into the graphitic carbon skeleton and the in-situ formation of N-CDs were systematically identified by the various structural and morphological studies. The green fluorescent N-CDs were used as active catalysts for the removal of Safranin-O dye and achieved 79 % removal efficiency. Furthermore, the prepared N-CDs were used to evaluate antibacterial activity with four different bacterial species, such as Shigella flexneri, Staphylococcus aureus, Streptococcus pyogenes, and Klebsiella pneumoniae. Amongst these, the highest antimicrobial activity was achieved against Klebsiella pneumonia, with a maximum zone of inhibition of 14.6 ± 1.12 at a concentration of 100 g mL-1. Thus, the obtained results demonstrate the cost efficient bifunctional application prospects of N-CDs to achieve significant catalytic and antibacterial activities.

Electronic, Raman and FT-IR spectral investigations of the charge transfer interactions between ketoconazole and povidone drugs with iodine.

The interaction between ketoconazole and povidone drugs with iodine was found to proceed through initial formation of a charge transfer (CT) complex as an intermediate. The stoichiometry of the complex was found to be 1:1 in the case of povidone-iodine system and 1:2 in the case of ketoconazole-iodine system and the same was confirmed by thermal (TGA/DSC) studies. The formation of I(3)(-) species was confirmed by electronic and laser Raman spectra. The three peaks appeared in Raman spectra, of the isolated adducts corresponds to nu(as)(I-I), nu(s)(I-I) and delta(I(3)(-)), confirmed the presence of asymmetric I(3)(-) ion. The rate of the interaction has been measured as a function of time and solvent. The pseudo-first-order rate constants at various temperatures for the interactions were measured and the activation parameters (DeltaG(#), DeltaS(#) and DeltaH(#)) were computed. Based on the spectral and spectrokinetic evidences a mechanism involving the formation of a polar intermediate and its conversion to the final product has been proposed and discussed.

Spectroscopic and kinetic studies on the interaction of ketoconazole and povidone drugs with DDQ.

The kinetics and mechanism of the interaction between 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) and ketoconazole and povidone drugs has been investigated spectroscopically. In the presence of large excess of donor, the 1:1 CT complex is transformed into a final product, which has been isolated and characterized by FT-IR and GC-MS techniques. The rate of formation of product has been measured as a function of time in different solvents at three temperatures. The thermodynamic parameters, viz. activation energy, enthalpy, entropy and free energy of activation were computed from temperature dependence of rate constants. Based on the spectro-kinetic results a plausible mechanism for the formation of the complex and its transformation into final product is presented and discussed.

Solvent effect on the charge transfer complex of oxatomide with 2,3-dichloro-5,6-dicyanobenzoquinone.

The charge transfer complex (CT-complex) between oxatomide drug and 2,3-dichloro-5,6-dicyanobenzoquinone (DDQ) was studied spectrophotometrically in 10 solvents at different temperatures. The donor oxatomide is found to form stable 1:1 stoichiometric complex with DDQ and the stoichiometry was unaffected by change in polarity of the solvent studied. The DeltaH degrees, DeltaS degrees and DeltaG degrees values are all negative, so the studied complex is reasonably stable and exothermic in nature. The ionization potential of the drug was determined using the CT-absorption bands of the complex in all the solvents. The dissociation energy of the charge transfer excited state for the CT-complex in different solvents was also determined and is found to be constant. The spectroscopic and thermodynamic properties were observed to be sensitive to the nature of the solvent.

Spectroscopic studies on the interaction of cilostazole with iodine and 2,3-dichloro-5,6-dicyanobenzoquinone.

The electron accepting properties of the 2,3-dichloro-5,6-dicyanobenzoquinone and iodine and electron donating properties of the drug cilostazole have been studied using the UV-vis, FT-IR, GC-MS and Far-IR techniques. The interaction of cilostazole drug with iodine and 2,3-dichloro-5,6-dicyanobenzoquinone resulted via the initial formation of charge-transfer complex as an intermediate. The rate of formation of the product have been measured and discussed as a function of solvent and temperature. The complexes have been found by Job's method of continuous variation revealed that the stoichiometry of the complexes in both the cases was 1:1. The enthalpies and entropies of formation of the complexes have been obtained by determining their rate constant at three different temperature. The ionization potential of the donor was determined using the charge-transfer absorption bands of the complexes and the same was found comparable with that computed using MOPAC PM3 method.

Spectroscopic studies on the interaction of cimetidine drug with biologically significant sigma- and pi-acceptors.

Spectroscopic studies revealed that the interaction of cimetidine drug with electron acceptors iodine and 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) resulted through the initial formation of ionic intermediate to charge transfer (CT) complex. The CT-complexes of the interactions have been characterized using UV-vis, (1)H NMR, FT-IR and GC-MS techniques. The formation of triiodide ion, I(3)(-), is further confirmed by the observation of the characteristic bands in the far IR spectrum for non-linear I(3)(-) ion with C(s) symmetry at 156 and 131cm(-1) assigned to nu(as)(I-I) and nu(s)(I-I) of the I-I bond and at 73cm(-1) due to bending delta(I(3)(-)). The rate of formation of the CT-complexes has been measured and discussed as a function of relative permittivity of solvent and temperature. The influence of relative permittivity of the medium on the rate indicated that the intermediate is more polar than the reactants and this observation was further supported by spectral studies. Based on the spectroscopic results plausible mechanisms for the interaction of the drug with the chosen acceptors were proposed and discussed and the point of attachment of the multifunctional cimetidine drug with these acceptors during the formation of CT-complex has been established.