Место издания:Publishing House of I.M.Sechenov First MSMU Moscow
Первая страница:193
Последняя страница:193
Аннотация:The development of selective and sensitive, and at the same time - compact, sensors for detection of varoius analites is one of the most important tasks of modern analytical chemistry. The nano-structured organic arrays, including photonic crystals and a sensitive layer of polymer, are quite promising as a basis for creation of these sensing elements. The photonic crystals are the regular structures of nanoscale particles having forbidden band towards photons and reflecting the light at a defined wavelength. According to the Wulff-Bragg's condition, the wavelength of reflected light depends on the periodicity of photonic crystal structure. The periodicity of particles changes in dependence on external conditions such as temperature, ionic strength, pH and especialy – to chemical treatment of matrix, including photonic crystals, by various substances. The alteration of periodicity in photonic crystal can be detected visually due to changed colour of matrix. Thus, the application of organic arrays with photonic crystals as basis of the sensor devices is the new approach in analytical chemistry.
The main goal of this publication is the investigation of action of non-polar solvents on the sensor organic matrix.
Photonic crystals were formed from polystyrene microspheres via self-assembly mechanism. The microspheres with particle size 170, 230 and 280 nm were obtained by emulsion polymerization [1]. The layered regular structure was covered on both sides by polydimethylsiloxane film (PDMS), swelling under the action of non-polar solvents or their saturated steams, and applyed on a microscope glass slide, acrylic disk, polycarbonate plate as a holding substrates.
Toxic non-polar solvents – benzene, toluene and o-xylene, commonly used in industry, were chosen as investigated analites. The sensor organic arrays in initial state and after treatment by these solvents and their steams were studied by diffuse reflectance spectroscopy. The solvent drops (5-20 mcl) were dosed exactly by the microsyringe on the surface of PDMS film; in the case of saturated steam the sensor array were treated by keeping in the closed vessel for a long time, and afer this – the duffuse reflectance spectra were plotted.
The reflectance spectral maxima for sensor organic arrays with average particle size 170, 230 and 280 nm are accordingly at wavelengths 450, 530 and 620 nm. The halfwidth of spectral maxima is 25-30 nm. The bathochromic shift (60-90 nm) of maxima at the diffuse reflectance spectra are observed in every case after the treatment of the sensor array by solvents or their steams. The solvent drop, inflicted on the surface of organic matrix, results in shift of spectral maximum in 5-8 min. In the case of treatment by solvent steams, the spectral maxima of sensor arrays with particle size 170 nm shifted during 240 min for o-xylene, 60 min for toluene and less then 30 min for benzene. Herewith, the treated site of matrix changes uniformly the colour, that allows to detect visually toluene up to 2.1–2.8.10-5 mole level, for example. The level up to 0.7.10-5 mole of toluene is succeeded to detect by the method of diffuse reflectance spectroscopy.
Thus, the nano-structured sensor arrays, including photonic crystals and sensitive toward presence of toxic solvent satured steams, were developed.
