Alexander A. Sergeev

pH-indicators doped polysaccharide LbL coatings for hazardous gases optical sensing.

Sensitive layer-by-layer (LbL) coatings for optical detection of gaseous NH(3) and HCl were prepared by self-assembly of oppositely charged polysaccharides (chitosan and λ-carrageenan) followed by doping LbLs with pH-sensitive dyes - bromothymol blue (BTB) and Congo red (CR). It has been shown that CR, being an amphoteric dye, diffuses into LbL films regardless of the charge of the outermost polyelectrolyte layer, and the dye loading increases linearly with the LbL film thickness, whereas BTB diffuses into LbL films only when the outermost layer is positively charged, and linearity between dye loading and film thickness holds only up to 8-12 double layers (DLs) deposited. Formation of dye-doped LbL coatings at the surface of K(+)/Na(+) ion-exchanged glass has allowed fabrication of composite optical waveguide (OWG) gas sensor for detection of ammonia and hydrochloric acid vapors. The response time of BTB-doped composite OWG for ammonia detection was below 1s, and the detection limit was below 1 ppm. CR-doped OWG sensors have shown high sensitivity to HCl vapor but slow relaxation time (up to several hours for 12 DL LbL films).

Optical Amines and Ammonia Sensors Based on Europium(III) Luminescent Complexes

The effect of amines and ammonia vapour on luminescence of Eu (III) complexes immobilized in different matrices has been investigated. It has been revealed that interaction of Eu (III) tris-dibenzoylmethanate with analyte vapour results in the increase of the intensity of Eu (III) luminescence. The mechanism of the effect of ammonia and amines vapours on intensification of the Eu (III) luminescence has been suggested using the data of IR, luminescence spectroscopy and quantum chemistry calculations.

Sensitive Coatings for Luminescence Detection of Cu(II) in Solutions

Here we present a simple technique for copper (II) detection in aqueous solutions by luminescent dye doped polymeric film. In this study the photoluminescent dye lumocupferon was first embedded in thin films of polysaccharide chitosan. The sensor response is forming by quenching the dye luminescence. This technique can offer a rapid detection of Cu2+ with a dynamic range up to 350 μM.

NANOSTRUCTURED BIOPOLYMER SYSTEMS FOR OPTICAL SENSING APPLICATIONS

The present study reports the research of natural polymeric materials for optical sensors for environment monitoring. The development of simple rapid methods of analysis of the chemical composition of gaseous medium with high sensitivity and selectivity is important for a variety of problems. Optical waveguide sensor system largely meets these requirements, having high sensitivity, low response time, high reliability and ease of fabrication [1]. Here we present two new approaches to develop optical waveguide sensors.