Reversible light-induced capacitance switching of azobenzene ether/PMMA blends

Fully reversible light-induced switching of the capacitance with changes larger than 50% has been achieved by using photo-active thin polymer films. The films consist of PMMA polymer blended with high concentrations of branched azobenzene ether dye molecules. Polymer thin sheet capacitors can be easily produced by spin coating and drop casting in various thicknesses ranging from 100 nm to 8 μm, respectively. Reversible capacitance switching is induced by illumination with UV and visible light, respectively. The capacitance change is correlated to the trans to cis isomerization of the azobenzene ether molecules and the alignment of the molecular dipoles in the film. Switching times depend on chromophore concentration, film thickness and light intensity used. The influence of wavelength of the light, of the temperature as well as of an electrical field applied during illumination on the capacitance change is addressed.     

Phytochemical and cytotoxic investigations of Alpinia mutica rhizomes

The methanol and fractionated extracts (hexane, ethyl acetate and water) of Alpinia mutica (Zingiberaceae) rhizomes were investigated for their cytotoxic effect against six human carcinoma cell lines, namely KB, MCF7, A549, Caski, HCT116, HT29 and non-human fibroblast cell line (MRC 5) using an in vitro cytotoxicity assay. The ethyl acetate extract possessed high inhibitory effect against KB, MCF7 and Caski cells (IC?? values of 9.4, 19.7 and 19.8 μg/mL, respectively). Flavokawin B (1), 5,6-dehydrokawain (2), pinostrobin chalcone (3) and alpinetin (4), isolated from the active ethyl acetate extract were also evaluated for their cytotoxic activity. Of these, pinostrobin chalcone (3) and alpinetin (4) were isolated from this plant for the first time. Pinostrobin chalcone (3) displayed very remarkable cytotoxic activity against the tested human cancer cells, such as KB, MCF7 and Caski cells (IC?? values of 6.2, 7.3 and 7.7 μg/mL, respectively). This is the first report of the cytotoxic activity of Alpinia mutica.     

Functional and preliminary characterisation of hydrocolloid from tamarillo (Solanum betaceum Cav.) puree

Hydrocolloid from tamarillo (Solanum betaceum Cav.) puree was extracted using water and characterised for the first time. Proximate compositions of the extracted hydrocolloid were also determined. Functional characteristics such as water-holding capacity, oil-holding capacity, emulsifying activity, emulsion stability, foaming capacity and stability of the hydrocolloid were evaluated in comparison to that of commercial hydrocolloids. Its functional groups and degree of esterification were determined using Fourier Transform Infrared (FT-IR) spectroscopy. Monosaccharide profiling was done using reverse-phase high pressure liquid chromatography (RP-HPLC). Screening of various fruits for high hydrocolloid yield after water extraction resulted in tamarillo giving the highest yield. The yield on dry weight basis was 8.30%. The hydrocolloid constituted of 0.83% starch, 21.18% protein and 66.48% dietary fibre with 49.47% degree of esterification and the monosaccharides identified were mannose, ribose, rhamnose, galacturonic acid, glucose, galactose, xylose and arabinose. Higher oil-holding capacity, emulsifying activity and emulsion stability compared to commercial hydrocolloids propose its possible application as a food emulsifier and bile acid binder. Foaming capacity of 32.19% and good foam stabilisation (79.36% of initial foam volume after 2 h of foam formation) suggest its promising application in frothy beverages and other foam based food products. These findings suggest that water-extracted tamarillo hydrocolloid can be utilised as an alternative to low methoxyl pectin.     

Insight into the Excitation-Dependent Fluorescence of Carbon Dots

High quantum yield, photoluminescence tunability, and sensitivity to the environment are a few distinct trademarks that make carbon nanodots (CDs) interesting for fundamental research, with potential to replace the prevalent inorganic semiconductor quantum dots. Currently, application and fundamental understanding of CDs are constrained because it is difficult to make a quantitative comparison among different types of CDs simply because their photoluminescence properties are directly linked to their size distribution, the surface functionalization, the carbon core structures (graphitic or amorphous) and the number of defects. Herein, we report a facile one-step synthesis of mono-dispersed and highly fluorescent nanometre size CDs from a ‘family’ of glucose-based sugars. These CDs are stable in aqueous solutions with photoluminescence in the visible range. Our results show several common features in the family of CDs synthesized in that the fluorescence, in the visible region, is due to a weak absorption in the 300–400 nm from a heterogeneous population of fluorophores. Fluorescence quenching experiments suggest the existence of not only surface-exposed fluorophores but more importantly solvent inaccessible fluorophores present within the core of CDs. Interestingly, time-resolved fluorescence anisotropy experiments directly suggest that a fast exchange of excitation energy occurs that results in a homo-FRET based depolarization within 150 ps of excitation.     

Competency evaluation on electrolytic conductivity measurement in Indonesia by an unofficial bilateral comparison between RCChem-LIPI and NIMT

Accreditation and Quality Assurance - The Research Centre for Chemistry—Indonesian Institute of Sciences (RCChem-LIPI) organized an unofficial bilateral comparison on electrolytic...     

Rigorous Stochastic Averaging at a Center with Additive Noise

We consider a random perturbation of a two-dimensional Hamiltonian system with an isolated elliptic fixed point; that is, a center. Under an appropriate change of time, we identify a reduced stochastically-averaged model. We give a rigorous proof of averaging at the center. Our main technique is to use the martingale problem. Our formulation of the result is in a sufficiently abstract setting that it agrees with more complicated averaging results.     

Sensitized emission from lanthanide-doped nanoparticles embedded in a semiconductor sol-gel thin film.

In(2)O(3) sol-gel thin films made with LaF(3):Ln(3+) (Ln=Er, Nd, and Eu) nanoparticles were prepared and showed sensitized emission of the lanthanide ions after In(2)O(3) matrix excitation. The excitation spectra showed an In(2)O(3) absorption band in addition to the excitation peaks of the lanthanide ions, clearly demonstrating that there is energy transfer from the In(2)O(3) matrix to Ln(3+) (Er(3+), Nd(3+), and Eu(3+)). Similarly, HfO(2) and ZrO(2) sol-gel thin films made with LaF(3):Ln(3+) nanoparticles also showed energy transfer from the semiconductor matrix to the lanthanide ions.