Porphyrin-based donor-acceptor COFs as efficient and reusable photocatalysts for PET-RAFT polymerization under broad spectrum excitation

Covalent organic frameworks (COFs) are crystalline and porous organic materials attractive for photocatalysis applications due to their structural versatility and tunable optical and electronic properties. The use of photocatalysts (PCs)...

Determination of hafnium in zirconium materials

An arc atomic emission technique of hafnium determination in zirconium is developed and tested. The study was carried out on a PGS-2 spectrometer equipped with MAÉS analyzer and information processing software «Atom 3.3». («VMK-Optoélektronika», Novosibirsk). Excitation of spectra of pre-oxidized metal was carried out using a medium-frequency generator «Vesuvius» («VMK-Optoélektronika», Novosibirsk). Analytical line of hafnium was free of spectral overlap with the lines of zirconium. We have set a current of the AC arc discharge (20 A), exposure time (30 sec) and the form of the electrode into which the sample is placed («narrow crater») are selected. The effect of buffering additives (graphite powder, bismuth fluoride) on the intensity of the analyte lines was studied. It is shown that high sensitivity of the analyte is observed for oxidized material without additives. Reduction of the random error attributed to the influence of conditions of spectrum excitation and sample preparation is achieved using the intensity ratio of the analyte line and zirconium as an analytical signal. Recommendations regarding preparation of the samples for calibration are given. The lower limit of the determined concentration is 0.01% with a relative standard deviation in repeatability 3%.

RESEARCH OF RADIAL VIEW OF SPECTRUM EXCITATION SOURCE BASED ON MICROWAVE PLASMA

The results of the research of the radial method of observation of the spectrum excitation source based on microwave plasma (MP) are presented in the article. Using of a combination of a three-slot torch and a longitudinal magnetic microwave field for the formation of MP makes it possible to obtain an axisymmetric plasma shape similar to ICP flame. The visual similarity of the MP and ICP confirms the existence of various analytical zones in plasma, both in height (with a radial view) and radius (with an axial view) caused by differences in temperature and electron density in the observed zones. Using of the radial method of MP observation makes it possible to increase the ratio of the intensities of the spectral lines to MP background for some elements and to reduce the detection limits achieved with the axial method of observation, especially when analyzing highly mineralized samples with a total mineralization of more than 1 % wt. Another important advantage of the radial method of MP observation in comparison with the axial is the increase of the linearity range of the calibration curve.

Effect of the functionalized π-bridge on porphyrin sensitizers for dye-sensitized solar cells: an in-depth analysis of electronic structure, spectrum, excitation, and intramolecular electron transfer

The effects of π-bridge on the structural and optoelectronic properties of porphyrin sensitizers were systematically elucidated.