Effect of ligand on the redox reactions of thallium metal clusters

Pulse radiolysis of an aqueous solution of mono-valent thallium ion and mixed solutions of Tl⁺/Ag⁺ in the presence of various amino polycarboxylic acids such as trans-1,2-diaminocyclohexane-N,N,N′,N′-tetraacetic acid (DCTA), diethylenetriaminepentaacetic acid (DTPA), N-(2-hydroxyethyl)ethylenediaminetriacetic acid (HEDTA) and triethylenetetraminehexaacetic acid (TTHA) has been carried out. Abnormal valence states of Tl ions were generated. It is concluded that DCTA, DTPA, HEDTA and TTHA decrease the redox potential of Tl ions in aqueous solutions. It was observed that the electron transfer from complexed Tl₂⁺ to Ag⁺ varied in the range 7.5 × 10⁸ to 1.0 × 10⁹, depending on the type of complexing ligand. Electron transfer from Tl₂⁺ to Ag⁺ lead to the formation of silver atoms, which agglomerate further to form silver colloid.     

Investigating the translocation of λ-DNA molecules through PDMS nanopores

We investigate the translocation of λ-DNA molecules through resistive-pulse polydimethylsiloxane (PDMS) nanopore sensors. Single molecules of λ-DNA were detected as a transient current increase due to the effect of DNA charge on ionic current through the pore. DNA translocation was found to deviate from a Poisson process when the interval between translocations was comparable to the duration of translocation events, suggesting that translocation was impeded during the presence of another translocating molecule in the nanopore. Characterization of translocation at different voltage biases revealed that a critical voltage was necessary to drive DNA molecules through the nanopore. Above this critical voltage, frequency of translocation events was directly proportional to DNA concentration and voltage bias, suggesting that transport of DNA from the solution to the nanopore was the rate limiting step. These observations are consistent with experimental results on transport of DNA through nanopores and nanoslits and the theory of hydrodynamically driven polymer flow in pores.     

From Grignard's reagents to well-defined Mg nanostructures: distinctive electrochemical and solution reduction routes

Anisotropic Mg nanowires have been successfully prepared by electrocrystallization of Grignard's reagents thought to proceed via a modified faces, steps, and kinks (FSK) mechanism. Mg nanoparticles with roughly hexagonal shapes have also been obtained via chemical reduction of the same Grignard's reagents.     

Preparation,X-ray crystallography and thermolysis of transition metal nitrates of 2,2′-bipyridine (Part 63)

Recent work has described the preparation and characterization of the two complexes [Fe₂(C₁₀H₈N₂)₄O(OH₂)₂](NO₃)₄ and [Co(C₁₀H₈N₂)₃]₂[Co(OH₂)₆]·7(OH₂) (NO₃)₈ in which both the nitrogen atoms of 2,2′-bipyridine are directly bonded with the metals. Their structures were determined by single-crystal X-ray diffraction at 296 K. Thermolysis of these complexes has been detailed by the use of TG–DTA and ignition delay measurements. Kinetics of thermal decomposition has also been established. Model free isoconversional and model fitting kinetic approaches have been applied to isothermal TG data for the decomposition of these complexes.     

Controlled orientation in a bio-inspired assembly of Ag/AgCl/ZnO nanostructures enables enhancement in visible-light-induced photocatalytic performance

In a bio-inspired approach, polyamine-mediated mineralization of ZnO was explored to develop an environmentally benign methodology for synthesizing Ag/AgCl/ZnO nanostructures. The assembling properties displayed by the polyamines to create composite structures was utilized to have the nanocomponents effectively interact with each other in a way that is desirable for the application envisaged. The polyamines, which act as a mineralizing agent for ZnO nanoparticles, also facilitate the formation of Ag/AgCl within ZnO under ambient conditions. Thus synthesized Ag/AgCl/ZnO nanostructures represent a multi-heterojunction system in which the nanocomponents lead in a synergistic way to enhancement in the photocatalytic activity under visible-light irradiation.     

Formation of silver nanoparticles in formamide:water mixtures: a radiolytic study

The pulse radiolysis of FA and FA:water solutions was studied in the absence and presence of redox indicator 1,1′-dimethyl-4,4′-bipyridinium dichloride (methyl viologen, MV²⁺). The experiments performed in the presence of MV²⁺ have provided strong support to the idea that the first species obtained from the reaction of e_sol⁻ and ^•OH with FA produces radicals that show reactivity towards the MV²⁺. Both the radicals on reaction with MV²⁺ results in the appearance of the well-known intense blue MV^•+ radical absorption signal (λ_max = 395 nm, λ_max = 605 nm). The intermediate radicals formed during radiolysis were used to generate silver nanoparticles.     

Modified structural,morphological and photoelectrochemical properties of 120 MeV Ag9+ ion irradiated BaTiO3 thin films

The effects of high electronic energy deposition on the structure, surface topography, optical property and photoelectrochemical behavior of barium titanate thin (BaTiO₃) films have been investigated by irradiating films with 120 MeV Ag⁹⁺ ions at different ion fluences in the range of 1 × 10¹¹–3 × 10¹² ions cm^?2. Barium titanate thin films were deposited on indium tin oxide-coated glass substrate by sol–gel spin coating method. The structure of the film was crystalline with tetragonal phase. Surface topography was studied by atomic force microscopy detailing the values of roughness of the films. Maximum photocurrent density of 1.78 mA cm^?2 at 0.4 V/SCE and applied bias photon-to-current efficiency (ABPE) of 0.91% was observed for BaTiO₃ film irradiated at 1 × 10¹¹ ions cm^?2.     

Nanoparticle-assembled capsule synthesis: formation of colloidal polyamine-salt intermediates

There is current interest in developing new synthesis strategies for multifunctional hollow spheres with tunable structural properties that would be useful in encapsulation and controlled release applications. A new route was reported recently, in which the sequential reaction of polyamines, multivalent anions, and charged nanoparticles leads to the formation of polymer-filled and water-filled organic/inorganic micron-sized structures known as nanoparticle-assembled capsules. This technique is unique among other capsule preparation routes, as it allows the rapid and scalable formation of robust shells at room temperature, in near-neutral water, and with readily available precursors. This nanoparticle assembly synthesis route involves two steps: the formation of polymer aggregates and the subsequent deposition of particles around the aggregates. The purpose of this paper is to understand in greater detail the noncovalent chemistry of the polymer-salt aggregation step. With poly(allylamine hydrochloride) (PAH) as the model polymer, aggregate formation was investigated as a function of charge ratio, pH, and time through dynamic light scattering, electrophoretic mobility measurements, chloride ion measurements, and optical microscopy. PAH formed aggregates by the cross-linking action of divalent and higher-valent anions above a critical charge ratio and in a pH range defined by the pKa values of PAH and the anion. The aggregates grew in size through coalescence and with growth rates that depended on their surface charge. Controlling polymer aggregate growth provided a direct and simple means to adjust the size of the resultant capsule materials.     

Isotropic-nematic phase transition in the Lebwohl-Lasher model from density of states simulations

Density of states Monte Carlo simulations have been performed to study the isotropic-nematic (IN) transition of the Lebwohl-Lasher model for liquid crystals. The IN transition temperature was calculated as a function of system size using expanded ensemble density of states simulations with histogram reweighting. The IN temperature for infinite system size was obtained by extrapolation of three independent measures. A subsequent analysis of the kinetics in the model showed that the transition occurs via spinodal decomposition through aggregation of clusters of liquid crystal molecules.