Pandiyan Thangarasu

Fluorescent organic nanoparticles (FONs) for selective recognition of Al3+: application to bio-imaging for bacterial sample

The development of a novel chemo-sensor for the detection of Al3+ with high sensitivity in aqueous solution is widely considered an important research goal because of the importance of such probes in medicine, living systems and the environment. In this work, we describe a new fluorescent probe, a Schiffs base N,N′-propylenebis(salicylimine) (salpn) as fluorescent organic nanoparticles for Al3+. The study shows that salpn detects Al3+ with the detection limit as low as 1.24 × 10−3 mM, indicating that the chemo-sensor has high sensitivity in aqueous medium, and the fluorescence intensity increases with the increasing Al3+ concentration in the presence of the salpn-ONPs which act as chemo-sensors. The interference of common coexistent metal ions such as Mn2+, Mg2+, Co2+, Fe3+, Ni2+, Zn2+, Sr2+, Ag+, Sm3+, Al3+, Cd2+, Ba2+, Na+ and K+ was tested, showing that salpn-ONPs efficiently detect Al3+ ions with small interference from Cu2+ and Cr3+. Finally, the efficiency of salpn to as a fluorescent probe for Al ion in living systems was evaluated in Gram-negative and Gram positive bacteria, and con-focal laser scanning microscopy confirms its utility that this chemo-sensor efficiently detects Al3+ ion in Staphylococcus aureus enclosed by a single membrane.

Density Functional Theory and Electrochemical Studies: Structure–Efficiency Relationship on Corrosion Inhibition

The relationship between structure and corrosion inhibition of a series of 30 imidazol, benzimidazol, and pyridine derivatives has been established through the investigation of quantum descriptors calculated with PBE/6-311++G**. A quantitative structure-property relationship model was obtained by examination of these descriptors using a genetic functional approximation method based on a multiple linear regression analysis. Our results indicate that the efficiency of corrosion inhibitors is strongly associated with aromaticity, electron donor ability, and molecular volume descriptors. In order to calibrate and validate the proposed model, we performed electrochemical impedance spectroscopy (EIS) studies on imidazole, 2-methylimidazole, benzimidazole, 2-chloromethylbenzimidazole, pyridine, and 2-aminopyridine compounds. The experimental values for efficiency of corrosion inhibition are in good agreement with the estimated values obtained by our model, thus confirming that our approach represents a promising and suitable tool to predict the inhibition of corrosion attributes of nitrogen containing heterocyclic compounds. The adsorption behavior of imidazole or benzimidazole heterocyclic molecules on the Fe(110) surface was also studied to elucidate the inhibition mechanism; the aromaticity played an important role in the adsorbate-surface complex.

Synergistic Antibacterial Activity of Nanohybrid Materials ZnO-Ag and ZnO-Au: Synthesis, Characterization, and Comparative Analysis of Undoped and Doped ZnO Nanoparticles

ZnO nanoparticles (NPs) were prepared using the hydrothermal method, and then doped with Ag or Au NPs, yielding ZnO NPs, ZnO–Ag NPs, and ZnO–Au NPs, which were characterized by transmission electron microscopy, X-ray diffraction, and energy-dispersive X-ray spectroscopy. The synthesized nanomaterials were analyzed for their antibacterial properties against bacterial strains (Staphylococcus aureus, Bacillus cereus, Escherichia coli, and Salmonella typhi) by qualitative and quantitative assays. Minimal inhibitory concentration (MIC) results show that growth control is more effective for Gram-positive bacteria than for Gram-negative bacteria. Although ZnO NPs and Ag NPs are antibacterial agents, the lowest bacterial growth was observed for ZnO–Ag NPs, showing that the doped Ag NPs greatly facilitate the interaction between the microbial cells and the NP surface. Though the same antibacterial effect was expected for ZnO–Au NPs, the inhibition activity was very close to that of ZnO NPs. The order of bacterial cell growth inhibition was ZnO–Ag NPs >> ZnO–Au NPs ~ ZnO NPs >> ZnO powder. We also analyzed the morphology of bacterial cells treated with NPs by scanning electron microscopy.

Organic-Inorganic Hybrid Nanoparticles for Bacterial Inhibition: Synthesis and Characterization of Doped and Undoped ONPs with Ag/Au NPs

Organic nanoparticles (ONPs) of lipoic acid and its doped derivatives ONPs/Ag and ONPs/Au were prepared and characterized by UV-Visible, EDS, and TEM analysis. The antibacterial properties of the ONPs ONPs/Ag and ONPs/Au were tested against bacterial strains (Staphylococcus aureus, Bacillus cereus, Escherichia coli and Salmonella typhi). Minimal Inhibitory Concentration (MIC) and bacterial growth inhibition tests show that ONPs/Ag are more effective in limiting bacterial growth than other NPs, particularly, for Gram positive than for Gram-negative ones. The order of bacterial cell growth inhibition was ONPs/Ag > ONPs > ONPs/Au. The morphology of the cell membrane for the treated bacteria was analyzed by SEM. The nature of bond formation of LA with Ag or Au was analyzed by molecular orbital and density of state (DOS) using DFT.

Theoretical and experimental studies of phenol oxidation by ruthenium complex with N,N,N- tris(benzimidazol - 2yl-methyl)amine

AbstractThe ruthenium complex with (N,N,N-tris(benzimidazol-2yl-methyl)amine, L1) was prepared, and characterized. Fukui data were used to localize the reactive sites on the ligand. The structural and electronic properties of the complex were analyzed by DFT in different oxidation states in order to evaluate its oxidant properties for phenol oxidation. The results show that the hard Ru(IV) cation bonds preferentially with a hard base (Namine = amine nitrogen, or axial chloride ion), and soft Ru(II) with a soft base (Nbzim = benzimidazole nitrogen or axial triphenyl phosphine). Furthermore, the Jahn-Teller effect causes an elongation of the axial bond in the octahedral structure. The bonding nature and the orbital contribution to the electronic transitions of the complex were studied. The experimental UV-visible bands were interpreted by using TD-DFT studies. The complex oxidizes phenol to benzoquinone in the presence of H2O2 and the intermediate was detected by HPLC and 13C NMR. A possible mechanism and rate law are proposed for the oxidation. The adduct formation of phenol with [Ru(O)L1]2+ or [Ru(OH)L1]+ is theoretically analyzed to show that [Ru(OH)L1-OPh]+ could produce the phenol radical. Graphical AbstractPhenol oxidation by ruthenium complex

A ruthenium(III) complex derived from N,N′-bis(salicylidene)ethylenediamine as a chemosensor for the selective recognition of acetate and its interaction with cells for bio-imaging: experimental and theoretical studies

A ruthenium(III) complex of N,N′-bis(salicylidene)ethylenediamine (L1) was prepared to give a compound of composition [RuL1(H2O)(PPh3)]PF6, which was examined using spectroscopic methods and single-crystal X-ray diffraction analysis. The geometric analysis was accomplished by DFT studies, which enabled a comparative analysis with related Ru(III) complexes. Sensing studies by means of fluorescence spectroscopy revealed that [RuL1(H2O)(PPh3)]+ performs the selective detection of acetate without interference from the presence of other anions (F−, Cl−, Br−, I−, CN−, ClO4−, NO3−, HSO4−, H2PO4−), with a detection limit of 1.20 × 10−7 M. The stoichiometry of the complex formed between the ruthenium complex and acetate is 1 : 1, as determined by Jobs method. Molecular orbital analysis based on DFT calculations revealed that the energy of the orbital, which is responsible for the Photo Electron Transfer (PET) mechanism, is lowered for [RuL1(H2O)(AcO)] when compared to that for [RuL1(H2O)(PPh3)]+, resulting in an enhanced fluorescence intensity after addition of acetate. Furthermore, the recognition of acetate ions with the ruthenium complex in Saccharomyces cerevisiae cells was studied, and the absorption of the substrate (host) within the cells and the subsequent addition of the guest (acetate anion) were carefully examined through fluorescence spectroscopy.

A Much-Needed Mechanism and Reaction Rate for the Oxidation of Phenols with ClO2: A Joint Experimental and Computational Study

The oxidation of phenols with chlorine dioxide, a powerful means to eliminate phenol pollutants from drinking water, is explored. Kinetic experiments reveal that 2,4,6-trichlorophenol exhibits a lower oxidation rate than other phenols because the chlorine atoms (σ = 0.22) at ortho and para-positions decrease the benzene’s electron density, in agreement with the Hammett plot. The oxidation of phenol was found to be second order with respect to phenol and first order with respect to ClO2 and a possible mechanism is proposed. The phenol/ClO2 oxidation was found to be pH-dependent since the reaction rate constant increases with increasing pH. The oxidation rate was also significantly enhanced with an increasing methanol ratio in water. The oxidation products, such as benzoquinones, were analysed and confirmed by liquid chromatography and gas chromatography–mass spectrometry. Density functional theory computations at both the B3LYP/6-311+G(d,p) and M06-2X.6-311+G(d,p) levels with the SCRF-PCM solvation model (i.e. with water) further supported the proposed mechanisms in which activation barriers predicted the right reactivity trend as shown by the kinetic experiments.

Silver Cementation with Zinc From Residual X Ray Fixer, Experimental and Thermochemical Study

Silver cementation with zinc from residual X. ray fixers (XRF) was studied. The chemical analysis of XRF showed 5.16 g/l (Ag), 0.56 g/l (Al), 5.24 g/L (K), 7.02 g/L (Na) and 172.56 g/L (S). The cementation process in terms of solution pH was thermodynamically modeled using FactSage by constructing the potential-pH diagram at 298.15 K. This di agram showed that the cementation process leads to metallic silver together with residual unreacted zinc. The parameters experimentally evaluated were: pH (ranged from 3.0 to 7.0, temperature (ranged from 298.15 to 318.15 K) and the Ag:Zn weight ratio (1:1, 1:2, 1:3, 1:4 and 1:5). The maxim silver cementation (99.99 % Ag) was obtained at 90s of reaction, pH 6.0, 318 K and Ag: Zn equal to 1:3. Sil ver cementation increases whit the Ag:Zn weight ratio, pH and temperature increases. The X-Ray and SEM-EDS results showed that the cementation product is formed by Ag and Zn.

A new computational model for the prediction of toxicity of phosphonate derivatives using QSPR

Structural and electronic properties of a series of 25 phosphonate derivatives were analyzed applying density functional theory, with the exchange-correlation functional PBEPBE in combination with the 6-311++G** basis set for all atoms. The chemical reactivity of these derivatives has been interpreted using quantum descriptors such as frontier molecular orbitals (HOMO, LUMO), Hirshfeld charges, molecular electrostatic potential, and the dual descriptor [