Temperature Driven Plasmon-Exciton Coupling in Thermoresponsive Dextran-Graft-PNIPAM/Au Nanoparticle/CdTe Quantum Dots Hybrid Nanosystem

The temperature-driven plasmon-exciton coupling in thermoresponsive dextran-graft-PNIPAM/Au nanoparticle/CdTe quantum dot (D-g-PNIPAM/Au NPs/CdTe QDs) hybrid nanosystem was studied. A significant (0.84 eV) splitting of the absorption peak was observed in the absorption spectrum of the nanosystem, which reflects the fact of formation of plexcitons, occurring due to strong plasmon-exciton coupling. An increasing with time plasmonic enhancement of the photoluminescence of CdTe QDs was revealed, as a result of the penetration of quantum dots into the volume of the D-g-PNIPAM/Au NP hybrid nanosystem and bonding to it. The heating–cooling cycle of the aqueous solution of the studied nanosystem leads to a reversible quenching-recovery alteration of the QD photoluminescence. The quenching was rationalized as a result of an increased probability of nonradiative resonance energy transfer (RET) from CdTe QDs to Au NPs, which occurs due to shortening of the NP-QD distance, caused by shrinking of the macromolecule due to cooling-induced lower critical solution temperature phase transition. Increasing the NP-QD distance in the heating stage recovers the QD PL intensity. The observed effect opens up opportunities for the controlled reversible temperature-driven tuning of the photoluminescence intensity of D-g-PNIPAM/Au NP/CdTe QD nanosystem, which is highly important for its potential use in photonics and biomedical applications.

     

On the health status of subjects employed at factories manufacturing enzyme preparations

Intensive exposure to the antigens of industrial strains of microorganisms and their metabolites resulted in the suppression of cellular immunity and the activation of some components of humoral immunity (IgM) and neutrophil bacterial activity in workers employed in the manufacture of enzymes. Industrial microflora (Bac. Subtilis and Asp. awamori) utilized in the technological process of microbiological synthesis of enzyme preparations was isolated from the skin in 34.25% and 16.44% and nasal and pharyngeal mucosa in 39.73% and 28.77% workers respectively. On clinical examination, most frequently affected were the skin (70.4% tested subjects), nasopharynx (64.4%), bronchopulmonary apparatus, oesophagus and GIT. Endoscopic tests confirmed the diagnoses in detecting producing strains on bronchial and oesophageal mucosa in 23.08% workers. In view of the low efficacy of employed individual protective equipment, the prevention of occupational pathology should be directed towards development or improvement of existing technological processes which would rule out intensive exposure of the human organisms to producing strains.