Sofia University

About: Sofia University is a education organization based out in Sofia, Bulgaria. It is known for research contribution in the topics: Large Hadron Collider & Laser. The organization has 8533 authors who have published 15730 publications receiving 306320 citations. The organization is also known as: University of Sofia & BFUS.

Engineering crystalline quasi-two-dimensional polyaniline thin film with enhanced electrical and chemiresistive sensing performances.

Abstract: Engineering conducting polymer thin films with morphological homogeneity and long-range molecular ordering is intriguing to achieve high-performance organic electronics. Polyaniline (PANI) has attracted considerable interest due to its appealing electrical conductivity and diverse chemistry. However, the synthesis of large-area PANI thin film and the control of its crystallinity and thickness remain challenging because of the complex intermolecular interactions of aniline oligomers. Here we report a facile route combining air-water interface and surfactant monolayer as templates to synthesize crystalline quasi-two-dimensional (q2D) PANI with lateral size ~50 cm2 and tunable thickness (2.6–30 nm). The achieved q2D PANI exhibits anisotropic charge transport and a lateral conductivity up to 160 S cm−1 doped by hydrogen chloride (HCl). Moreover, the q2D PANI displays superior chemiresistive sensing toward ammonia (30 ppb), and volatile organic compounds (10 ppm). Our work highlights the q2D PANI as promising electroactive materials for thin-film organic electronics. Large area and homogeneous PANI thin films are important in high-performance organic electronics, but controlling the thickness and crystallinity in PANI thin films is challenging. Here the authors use air-water interface and surfactant monolayer templates to synthesize large area crystalline PANI films with tunable thickness.

Nanocomposite Formation in Hydrogenated Nitrile Rubber (HNBR)/Organo‐Montmorillonite as a Function of the Intercalant Type

Abstract: Hydrogenated acrylonitrile butadiene rubber (HNBR) was melt compounted with montmorillonite (MMT) and organophilic modified MMTs prior to sulfur curing In contrast to the micro-composite formation resulting from the compounding of the HNBR and pristine MMT, the modified MMTs (ie, octasdecylamine : MMT-ODA, octadecyltrimethylamine : MMT-ODTMA, methyltallow-bis(2-hydroxyethyl) quaternary ammonium : MMT-MTH intercalants) produced nanocoomposites It was found that the organoclay with primary amine intercalant (cf MMT-ODA) gave confined structures along with the exfoliated/intercalated structures This was traced to its reactivity with the curatives By contrast, the organoclays containing less reactive quaternary ammonium compounds (cf MMT-ODTMA, MMT-MTH) were exfoliated and intercalated based on X-ray diffraction (XRD) and transmission electron microscopy (TEM) results The hydroxyl functional groups of the MMT-MTH supported the clay dispersion The better adhesion between MMT-MTH and HNBR was explained by hydrogen bonding between the hydroxyl groups of the intercalant and the acrylonitrile group of the HNBR matrix This HNBR/MMT-MTH nanocomposite showed the best mechanical properties as verified by tensile mechanical tests and dynamic mechinical thermal analysis (DMTA) The high tensile strength along with the high elongation at break for the rubber nanocomposites were attributed to the ability of the 'clay network' to dissipate the input energy upon uniaxial loadin

Increased levels of tissue factor mRNA in mononuclear blood cells of patients with primary antiphospholipid syndrome.

Abstract: Antiphospholipid antibodies (aPL) may stimulate tissue factor (TF) expression in cultured endothelial cells and monocytes, but there are discrepancies as to the expression of TF in the patients with antiphospholipid syndrome (APS). By using reverse transcription and polymerase chain reaction amplification, we have analysed TF mRNA accumulation in freshly isolated mononuclear blood cells (MBC) of 14 patients with primary APS (PAPS) and six normal controls. TF mRNA accumulation was low or absent in uncultured MBC from all normal controls, but was elevated in uncultured MBC from nine of the patients as well as in normal MBC incubated with 100 ng/ml lipopolysaccharide (LPS). Mean levels of TF mRNA, as measured by densitometry, were higher in MBC from patients (N = 14) than in those from controls (N = 6, P = 0.009), and in MBC from patients with a history of thrombosis (N = 9) than in those from patients without thrombosis (N = 5, P = 0.02). Uncultured MBC of patients with thrombosis accumulated TF mRNA at similar levels to LPS-treated normal MBC. Increased levels of TF mRNA were found in eight of ten patients with conventional aPL (ie, anti-cardiolipin antibodies [aCL] and/or lupus anticoagulant [LA]) and little if any accumulation of TF mRNA was observed in three of four patients without aPL at the time of study. These data strongly suggest that circulating monocytes of many patients with PAPS are subjected to an up-regulated TF expression that may well explain their prothrombotic state. Although the presence or absence of TF mRNA in MBC was associated with, respectively, the presence or absence of conventional aPL in 11 of the 14 patients studied, our study cannot exclude the involvement of factors other than aCL or LA in inducing TF expression.

Surface photovoltage phase spectroscopy – a handy tool for characterisation of bulk semiconductors and nanostructures

Abstract: A new approach is proposed for determining the semiconductor conductivity type (n or p) based on measurements of surface photovoltage (SPV) phase spectra in metal–insulator–semiconductor structures under modulated super-bandgap optical excitation. It is shown that the sign of the bandgap-related knee in the spectrum of the SPV phase modulus gives information about the surface band bending direction and thus about the semiconductor type. The proposed approach can be applied also to multilayered structures, containing buried interfaces in order to obtain the band bending in the sample region, where the light is absorbed. Further on, the SPV phase spectral dependence is discussed taking into account the recombination processes in the system under study. It is concluded that for the cases of non-linear recombination the SPV phase spectrum reveals the peculiarities of the optical absorption coefficient spectrum, which is known until now only for the SPV amplitude spectrum. This is confirmed by SPV phase and amplitude spectral measurements in bulk Si, as well as in GaAs quantum wells.