Metallo-Surfactant assisted silver nanoparticles: A new approach for the colorimetric detection of amino acids.

In this study, we report a new class of metallo-surfactant assisted silver nanoparticle produced by reduction process via AgNO3 solution and extract of Turnera Subulata (TS) in aqueous which act as reducing and metallo-surfactant [Co(ip)2(C12H25NH2)2](ClO4)3 (ip = imidazo[4,5-f][1,10]phenanthroline) act as stabilizing agent. In this study the silver nanoparticles produced using Turnera Subulata extract has showed yellowish brown color formation and an absorption peak at 421 nm signaling the biosynthesis of silver nanoparticles. The presence of functional groups in the plant extracts were identified by FTIR analysis. In addition, the effects of ratio, changing the concentration of the metallo surfactant, TS plant leave extract, metal precursors, and pH of the medium have been investigated on the scale of the Ag nanoparticles. Spherical shaped, crystalline in nature and ∼50 nm sized particles were recorded using TEM and DLS analysis. Furthermore, the mechanistic insights into cysteine and dopa detection by silver nanoparticles were investigated using HR-TEM analysis. This induces aggregation in stable silver nanoparticles owing to selective and strong interaction of -SH group of cysteine with silver nanoparticle surface. The biogenic Ag NPs are found to be highly sensitive to amino acids of dopa and cysteine with the diagnosis maximum for both amino acids as low as 0.9 µM (dopa) and 1 µM (cysteine) under optimized conditions.

'On and Off' intercalative binding behaviour of double chain surfactant cobalt(III) complex containing 2, 2'-bipyridyl ligand in ß-Cyclodextrin: A detail approach on Host-guest inclusion of surfactant cobalt(III) complex and CT-DNA binding in micro-heterogeneous medium.

The binding interaction of surfactant cobalt(III) complex, cis-[Co(bpy)2(HA)2](ClO4)3, in which bpy is 2,2-bipyridine and HA is hexadecylamine or cetylamnine with DNA was through intercalative mode via the long aliphatic chains present in the ligands. The binding was investigated by various techniques, electronic absorption, fluorescence spectroscopy, circular dichroism (CD), cyclic voltametry (CV) and viscosimetry measurements. The spectroscopic studies together with cyclic voltammetry and viscosity experiments support that the surfactant cobalt(III) complex binds to calf thymus DNA by intercalation through the aliphatic chain present in the complex into the base pairs of DNA. The presence of bipyridine ligand with larger π-frame work may also enhance intercalation. UV-vis., spectrum showed 4 nm bathochromic shift of the absorption band at 352 nm along with significant hypochromicity for the absorption band of the complex. The intrinsic binding constants(at below and above CMC are Kb = 2.41 × 105M-1, Kb = 3.12 × 106M-1 respectively) is more in keeping with intercalators and suggests this binding mode. The viscosity measurements showed that the surfactant cobalt(III) complex-DNA interaction can be hydrophobic and confirm intercalation. Moreover, the complex induced detectable changes in the CD spectrum of CT-DNA. Competitive binding study with ethidium bromide (EB) shows that the surfactant complex exhibits the ability to displace the DNA-bound EB indicating that the complex binds to DNA in strong competition with EB for the intercalative binding site. Also, CV results confirm this mode because, with increasing the CT-DNA concentration, shift to higher potential was observed. Besides the effect of binding of surfactant cobalt(III) complex to DNA in presence of ß-cyclodextrin has also studied. This binding of the surfactant cobalt(III) complex in presence of ß-cyclodextrin medium has been prevented (at below and above CMC are Kb = 5.45 × 104M-1, Kb = 6.92 × 105M-1 respectively) due to the incorporation of the aliphatic chains into the cavity of ß-cyclodextrin. In presence of ß-cyclodextrin the binding occur through surface and (or) groove binding can be attributed to the inclusion of the long aliphatic chain that is present in one of the ligands into cyclodextrin.

States of Aggregation and Phase Transformation Behavior of Metallosurfactant Complexes by Hexacyanoferrate(II): Thermodynamic and Kinetic Investigation of ETR in Ionic Liquids and Liposome Vesicles.

Electronic absorption spectroscopy was used to study the ETR of surfactant-cobalt(III) complexes containing imidazo[4,5-f][1,10]phenanthroline, dipyrido[3,2-d:2'-3'-f]quinoxaline and dipyrido[3,2-a:2',4'-c](6,7,8,9-tetrahydro)phenazine ligands by using ferrocyanide ions in unilamellar vesicles of dipalmitoylphosphotidylcholine (DPPC) and 1-butyl-3-methylimidazolium bromide ((BMIM)Br), at different temperatures under pseudo-first-order conditions using an excess of the reductant. The reactions were found to be second-order and the electron transfer is postulated as occurring in the outer sphere. The rate constant for the electron transfer reactions was found to increase with increasing concentrations of ionic liquids. Besides these, the effects of surfactant complex ions on liposome vesicles in these same reactions have also been studied on the basis of hydrophobicity. We observed that, below the phase transition temperature, there is an increasing amount of surfactant-cobalt(III) complexes expelled from the interior of the vesicle membrane through hydrophobic effects, while above the phase transition temperature, the surfactant-cobalt(III) complexes are expelled from the interior to the exterior surface of the vesicle. Kinetic data and activation parameters are interpreted in respect of an outer-sphere electron transfer mechanism. By assuming the existence of an outer-sphere mechanism, the results have been clarified based on the presence of hydrophobicity, and the size of the ligand increases from an ip to dpqc ligand and the reactants become oppositely charged. In all these media, the ΔS# values are recognized as negative in their direction in all the concentrations of complexes employed, indicative of a more ordered structure of the transition state. This is compatible with a model in which these complexes and [Fe(CN)6]4- ions bind to the DPPC in the transition state. Thus, the results have been interpreted based on the self-aggregation, hydrophobicity, charge densities of the co-ligand and the reactants with opposite charges.