Modified electrode with reduced graphene oxide/poly(3-hydroxyphenylacetic acid): a new platform for oligonucleotide hybridization

Journal of Solid State Electrochemistry - This paper reports a new platform for oligonucleotide hybridization, prepared by electropolymerization of 3-hydroxyphenylacetic acid onto gold electrode...     

Experimental and theoretical analysis of bias ionization by?α-particles in a nitrogen laser

Nitrogen laser performance with TE configuration and wedge electrodes is analyzed with background ionization in the laser discharge channel by α particles at a low exposition rate. With the bias ionization, the laser power presents two peaks as a function of gas pressure, with one at the normal low pressure, without bias ionization, and the other at high pressure generated by bias ionization. A simple theoretical model has been developed in a trial to understand this behavior. This model was first tested in later results for a TE configuration nitrogen laser, with flat electrodes, without and with bias ionization. It has been observed that due to the competition between electrode shielding by positively charged α particles and bulk ionization by impact, the laser energy is suppressed with pressure below 50 Torr and enhanced above it.     

Li‐doped nanosized TiO2 powder with enhanced photocalatylic acivity under sunlight irradiation

This work reports on the synthesis of Li‐doped TiO₂ nanoparticles using the sol–gel process and solid‐state sintering, and investigates their potential use as a photocatalyst for degradation under sunlight excitation of different organic model compounds in aqueous solution. The structure of the nanocrystals was examined by X‐ray diffraction, UV‐vis ground state diffuse reflectance absorption spectra and X‐ray photoelectron emission spectroscopy. Results showed that samples prepared by sol–gel process and calcined at 400 °C are composed of a mixture of anatase and rutile phases, in contrast to the one prepared by solid‐state sintering, which exhibits an anatase phase with Li being involved in a spinel phase. The photocatalytic degradation of aqueous solutions of different aromatic compounds was successfully achieved under sunlight excitation in presence of Li‐doped TiO₂ prepared via sol–gel process. It was shown that the calcination temperature and the preparation mode greatly affect the photocatalytic efficiency. Copyright © 2010 John Wiley & Sons, Ltd.     

A method for bioconjugation of carbohydrates using Diels-Alder cycloaddition

Diels-Alder-type cycloaddition of an electronically matched pair of saccharide-linked conjugated dienes and a dienophile-equipped protein gives neoglycoproteins at ambient temperature in pure water with a reaction half-life of approximately 2 h. Uncoupled saccharides can be recovered by diafiltration with complete conservation of the diene moiety, thus allowing their repeated use. The procedure described is the first for creating a carbon-carbon covalent bond in the bioconjugation step between a saccharide and a protein.     

Structure and photoluminescence of a benzil nanocolumn in a C-methylcalix[4]resorcinarene-based framework

A new framework based on C-methylcalix[4]resorcinarene and the flexible nonconjugated spacer 1,4-bis(imidazol-1yl-methyl)benzene encloses a large one-dimensional channel, containing benzil nanocolumns. Unlike in a previously reported series of benzil-containing supramolecular solids with conjugated linker molecules, benzil luminescence is observed, but the lifetime of 580 ns at 77 K is considerably shorter than the 145 micros reported for neat benzil at room temperature.     

Coherence transition in granular YBa2Cu3O7-δ, YBa2Cu2.95Zn0.05O7-δ, and YBa1.75Sr0.25Cu3O7-δ superconductors

We have studied experimentally the electrical magneto-conductivity near the superconducting transition of YBa₂Cu₃O_7-δ, YBa₂ (Cu_2.95Zn_0.05)O_7-δ and Y(Ba_1.75Sr_0.25)Cu₃O_7-δ polycrystalline samples. The measurements were performed in magnetic fields ranging from 0 to 400 Oe applied parallel to the current orientation. The results show that the resistive transition of these systems proceeds in two stages. The pairing transition occurs at the bulk critical temperature T_c, where superconductivity is stabilized within small and homogeneous regions of the sample generically called grains. The regime of approach to the zero resistance state reveals the occurrence of a coherence transition at a lower temperature T_c0. This transition is related to the connective nature of the granular samples and is controlled by fluctuations of the order-parameter phase of individual grains. Our experiments show that the Zn-doping, besides depressing the pairing critical temperature, strongly enlarges the temperature range dominated by effects related to the coherence transition. The substitution of Ba by Sr causes only a small reduction of T_c, but also enhances significantly the effects related to the grain coupling phenomenology. In general, our results indicate that these impurity substitutions in YBa₂Cu₃O_7-δ produce or magnify the granularity at a microscopic level, enhancing the effects of phase fluctuations in the conductivity near the transition.     

Natural-based plasticizers and biopolymer films: A review

In recent years, much attention has been focused on research to replace petroleum-based commodity plastics, in a cost-effective manner, with biodegradable materials offering competitive mechanical properties. Biopolymers have been considered as the most promising materials for this purpose. However, they generally present poor mechanical properties regarding processability and end-use application, since the fragility and brittleness exhibited during thermoformation can limit their potential for application. In order to overcome this problem, plasticizers are added to provide the necessary workability to biopolymers. This class of products became more visible when biodegradable additives and plasticizers also became the focus of material scientists. The use of natural and/or biodegradable plasticizers, with low toxicity and good compatibility with several plastics, resins, rubber and elastomers in substitution of conventional plasticizers, such as phthalates and other synthetic conventional plasticizers attracted the market along with the increasing worldwide trend towards use of biopolymers. Here we discuss the main results and developments in natural plasticizer/synthetic and biopolymer-based films during the last decades.