2-Dimensional Clay/Reduced Graphene Oxide Ordered Heterostructures Dispersible in Water via a One-Step Hydrothermal Route.

A facile and green method for trapping the hydrophobic reduced graphene oxide between the hydrophilic Kunipia F layers in order to attain stable aqueous dispersions of reduced graphene oxide is described. Initially stable aqueous dispersions of hydrophilic clay intercalated with hydrophilic graphene oxide sheets were formed providing well-organized heterostructures, as it was revealed by scanning electron microscopy images. These structures were preserved in the product obtained after hydrothermal treatment where the hydrophilic graphene oxide was converted to hydrophobic reduced graphene oxide. Ultraviolet measurements revealed the aforementioned conversion which was accompanied by a characteristic change in color from yellow-brown to black in the corresponding aqueous dispersions of these hybrids before and after hydrothermal treatment. The stability of these homogeneous dispersions was confirmed by Zeta Potential measurements implying interactions both in cases of graphene oxide and reduced graphene oxide with clay sheets that made feasible the effective interstratification of graphene-clay layered materials. In these stable dispersions chemistry in aqueous environment could be fully utilized making possible their incorporation e.g., as fillers to hydrophilic polymeric matrices extending thus the limits of application.

Removal of Reactive Red 195 from aqueous solutions by adsorption on the surface of TiO2 nanoparticles.

Nanoparticles of TiO2 were synthesized and characterized by XRD, BET, TG/DTA and TEM measurements. The commercial azo dye Reactive Red 195 (RR195) was selected as a model dye in order to examine the adsorption capacity of TiO2 at room temperature, under dark conditions. It was demonstrated that RR195 could be efficiently adsorbed in aqueous suspension of TiO2. A study on the effects of various parameters like initial pH, concentration of dye and concentration of adsorbent has been carried out in order to find optimum adsorption conditions. The optimum pH of sorption was 3. Substantial reduction of COD, besides removal of colour, was also achieved. The experimental data were analyzed by the Langmuir and Freundlich adsorption models. Equilibrium data fitted very well with the Langmuir model signifying the energetic homogeneity of TiO2 surface adsorption sites. At the temperature of 30 degrees C, the maximum monolayer adsorption capacity obtained from the Langmuir model is approximately 87 mg/g (pH 3.0). Kinetic studies were carried out and showed a rapid sorption of dye in the first 30 min while equilibrium was reached at 1h. Three kinetic adsorption models were used to describe the kinetics data, the pseudo-first-order model, the pseudo-second-order model and the intraparticle diffusion model. The sorption kinetics of dye was best described by the pseudo-second-order kinetic model.

New criteria to increase the reliability of systolic time intervals in left bundle branch block and right ventricular pacing.

We measured the systolic time intervals (STI) in 14 patients (pts) with intermittent left bundle branch block (LBBB) in order to find correlations and comparisons in their values which might pertain to the individual patients, with (b) and without (a) LBBB. QS2I, PEP and the PEP/LVET ratio increased significantly (b) while the LVET I did not change. STI correlation was significant and improved further when the QS2 (b) was corrected by subtracting from it the QRS prolongation (b) in msec. All 7 pts with a PEP/LVET ratio (b) greater than 0.65 had an (a) ratio greater than 0.42 (normal limits for our laboratory), sensitivity 100%. Six of 7 patients with a PEP/LVET (b) less than 0.65 had an (a) ratio less than 0.42 (specificity 87.5%). For the individual patient with LBBB his STI can be quite accurately assessed by subtracting from his QS2 (b) the prolongation of the QRS (b) greater than 80 msec the length of the normal QRS duration. The above data were prospectively evaluated in 10 pts to whom intermittent right ventricular pacing was applied. We found that the correction of the QS2 interval for QRS prolongation permitted a very reliable calculation of the STI.