Rajendran Selvakumar

Differently environment stable bio-silver nanoparticles: study on their optical enhancing and antibacterial properties.

Generally, limited research is extended in studying stability and applicational properties of silver nanoparticles (Ag NPs) synthesized by adopting ‘green chemistry’ protocol. In this work, we report on the synthesis of stable Ag NPs using plant-derived materials such as leaf extract of Neem (Azadirachta indica) and biopolymer pectin from apple peel. In addition, the applicational properties of Ag NPs such as surface-enhanced Raman scattering (SERS) and antibacterial efficiencies were also investigated. As-synthesized nanoparticles (NPs) were characterized using various instrumentation techniques. Both the plant materials (leaf extract and biopolymer) favored the synthesis of well-defined NPs capped with biomaterials. The NPs were spherical in shape with an average particle size between 14-27 nm. These bio-NPs exhibited colloidal stability in most of the suspended solutions such as water, electrolyte solutions (NaCl; NaNO3), biological solution (bovine serum albumin), and in different pH solutions (pH 7; 9) for a reasonable time period of 120 hrs. Both the bio-NPs were observed to be SERS active through displaying intrinsic SERS signals of the Raman probe molecule (Nile blue A). The NPs were effective against the Escherichia coli bacterium when tested in nutrient broth and agar medium. Scanning and high-resolution transmission electron microscopy (SEM and HRTEM) images confirmed cellular membrane damage of nanoparticle treated E. coli cells. These environmental friendly template Ag NPs can be used as an antimicrobial agent and also for SERS based analytical applications.

A facile synthesis of silver nanoparticle with SERS and antimicrobial activity using Bacillus subtilis exopolysaccharides

In this study, we report a facile synthesis of silver nanoparticle having SERS and antimicrobial activity using bacterial exopolysaccharide (EPS). Bacillus subtilis (MTCC 2422) was grown in nutrient broth and the extracellular EPS secreted by the organism was extracted and purified. The purified EPS was used for the synthesis of silver nanoparticles. The kinetics of silver nanoparticle synthesis was deduced by varying the exposure time and the concentration of EPS. The rate constant (k) for the synthesis of silver nanoparticle was calculated from the slope of ln(A∞ − At) versus time plot. The k value was found to be 3.49 × 10−3, 5.81 × 10−3 and 5.03 × 10−3 per min for particle synthesis using 2, 5 and 10 mg/mL EPS, respectively. The nanoparticles synthesised had an average particle size of 5.18 ± 1.49 nm, 1.96 ± 0.77 nm and 2.08 ± 0.88 nm for 2, 5 and 10 mg/mL EPS, respectively. The synthesised particles were characterised using UV-Vis absorbance spectroscopy, high-resolution transmission electron microscopy (HRTEM) attached to EDS (energy dispersive spectroscopy), Fourier transform infrared spectroscopy (FTIR), surface enhanced Raman spectroscopy (SERS) and zeta potential analyser. To our knowledge, this is the first study to report SERS activity of microbial Bacillus subtilis EPS-based synthesis of silver nanoparticle. HRTEM images showed silver nanoparticle entrapped in polysaccharide nanocages. Silver nanoparticle showed higher adherence towards the bacterial surface, with good bactericidal activity against Pseudomonas aeroginosa and Staphylococcus aureus.

Synthesis of photocatalytic La(1–x)AxTiO3.5–δ (A=Ba, Sr, Ca) nano perovskites and their application for photocatalytic oxidation of congo red dye in aqueous solution

Abstract A-site substituted La 0.8 A 0.2 TiO 3.5–δ (A=Ba, Sr, Ca) nano perovskites were prepared by sol-gel method and characterized using thermogravimetry/differential thermal analysis (TGA/DTA), X-ray diffraction (XRD), ultraviolet-visible (UV-Vis) spectroscopy and transmission electron microscopy (TEM). XRD analysis showed that the La 0.8 A 0.2 TiO 3.5–δ (A=Ba, Sr, Ca) nano perovskites derived after calcination at 800 °C were in single phase with orthorhombic structure. The particle size of all nano perovskites was found to be ∼20 nm. The synthesized nano perovskites were tested for the photocatalytic decomposition of an azo dye, Congo red. The sequential behavior of La 0.8 A 0.2 TiO 3.5–δ (A=Ba, Sr, Ca) nanoperovskites for photocatalytic decomposition of congo red in aqueous solution by visible light at room temperature was studied at various time intervals and the efficiency of degradation of the nanoperovskites was compared. Among all the A-site substituted La 0.8 A 0.2 TiO 3.5–δ (A=Ba, Sr, Ca) nano perovskites, Ba substituted compound showed the highest dye degradation.

Amino­guanidinium hydrogen succinate

The title compound, CH7N4 +·C4H5O4 −, is a molecular salt containing discrete aminoguanidinium and succinate ions. The aminoguanidinium cation is nearly planar, with a maximum deviation of 0.035 (1) Å. The dihedral angle between the aminoguanidinium cation and the succinate anion is 3.35 (6)°. The crystal packing exhibits intermolecular N—H⋯O and O—H⋯·O hydrogen bonds.

Amino-guanidinium hydrogen fumarate.

The title compound, CH7N4 +·C4H3O4 −, is a molecular salt in which the aminoguanidinium cations and fumarate monoanions are close to planar, with maximum deviations of 0.011 (1) and 0.177 (1) Å, respectively. The crystal packing is stabilized by intermolecular N—H⋯O and O—H⋯O hydrogen bonds.

Isomorphic metal malonates with N-aminoguanidine: MCo2O4 (M = Ni & Zn) nanoparticle synthesis via a (AmgH)2[M1/3Co2/3(mal)2(H2O)2] precursor solid solution

Divalent metal complexes of malonate with aminoguanidine possessing (AmgH)2[M(mal)2(H2O)2] [M = Co (1), Ni (2) or Zn (3); mal = malonate anion and AmgH = aminoguanidinium cation] stoichiometry and their solid solutions, (AmgH)2[Ni0.5Co0.5(mal)2(H2O)2] (4) and (AmgH)2[M1/3Co2/3(mal)2(H2O)2] [where M = Ni (5) or Zn(6)], were prepared and characterized by analytical, thermal and powder X-ray diffraction studies. The crystal and molecular structures of both cobalt and nickel compounds were isomorphic, crystallizing in the triclinic space group P. The complexes exhibit similar modes of endo-followed by exothermic decomposition to produce respective metal oxides below 550 °C. Metal cobaltites, MCo2O4 where M = Ni and Zn, were obtained from the above solid solutions as decomposition residues by heating at 600, 700 and 800 °C in a silica crucible for 3 h. Spinel oxides nanoparticles were characterized by infrared spectra, powder X-ray diffraction patterns, scanning electron microscope coupled with energy dispersive X-ray analysis and transmission electron microscope studies.