Kaspars Ozols

Investigation of mechanism of organic solvent vapours sensing effect in polyisoprene-high structure carbon black composite

A study of detecting organic vapour environments of nine different solvents by polyisoprene-high structured carbon composite (PHSCBC) sensors is reported. The electric resistance of the composite is found to be increased as soon as it contacts the vapour and to return to the initial value after being removied from the environment. To reveal the mechanism of the effect, simultaneous measurements of electrical resistance, elongation, and changes caused by sorption of organic solvent molecules in the bulk of PHSCBC samples were made in real time. From sorption experiments it has been found that the increase of electric resistance is generally dominated by absorption of solvent molecules in the matrix material, subsequently swelling it up and increasing the distance between conductor particles. The experiments prove that a remarkable and rapid change of the resistance could be explained by change of the tunnelling currents between adjacent carbon nano-particles.

Development and Characterization of Novel Conductive Nanofiller Based on Multi-Walled Carbon Nanotubes Grafted with Poly(3,4-Ethylenedioxythiophene)

In the present study, an approach for the graft polymerization of multi-walled carbon nanotubes (MWCNTs) with 3,4-ethylenedioxythiophene (EDOT) has been evaluated. The surface of the MWCNTs was activated with thiophene groups through the amide linker followed by oxidative polymerization of EDOT monomer resulted in the development of PEDOT-g-MWCNTs. The methods of thermal gravimetric analysis (TGA), X-ray fluorescence, and Raman spectroscopy were used for characterization of functionalization efficiency. The TGA data indicated of 21% functionalization attached to MWCNTs. X-ray fluorescence confirmed the presence of Cl, and S atoms in functionalized fillers. The study of Raman spectra confirmed the presence of PEDOT groups attributed to most characteristic signal at 1400-1500 cm-1 region. The electrical conductivity for both pristine MWCNT and PEDOT-g-MWCNT powder materials was compared.

Phase conjugation properties of a-As-S-Se films

Light wavefront inversion (phase conjugation) in a-As-S-Se films has been studied experimentally. Phase conjugation (PC) of plane and spherical waves is carried out in a-As40S15Se45 films using degenerate four-wave-mixing (DFWM) geometry at 633 nm. In the plane wave case simultaneous PC efficiency and DE measurements have been made versus exposure time, light intensity and holographic grating period. The maximal PC efficiency was 2.3% and the minimal PC specific recording energy was 2 J/(cm2%) whereas the maximal DE was 0.9% and the minimal specific hologram recording energy was 10 J/(cm2%). The optimal grating period was 2 μm. When compared to a-Se films a-As-S-Se films exhibit lower PC efficiency but higher photosensitivity. The advantages of a PC setup for the investigation of photoinduced processes in comparison with a usual holographic setup are observed.