This work deals with the field of dielectric photonics in a terms of development of dielectric microstructures which allows obtaining compact devices for controlling optical radiation at wavelength scales, providing opportunities for enhancing the luminescence intensity of sensitive layer in optical chemical sensors. One of the directions of the dielectric photonics is freely propagating optical radiation transformation by the axisymmetric microstructures into a high-intensity light beam of up to several wavelength extent and a lateral dimension of up to several tenths of the wavelengths, called as the "photonic nanojet." Here we present the simple, low-cost technique for dielectric microstructures developing and demonstrate the direct observation of luminescence enhancement via photonic nanojets formed by obtaining microstructures.
Quantitative and qualitative determination of metal ions is essential for a number of applications in life sciences and environmental monitoring. Optical and, namely, luminescent sensing allows non-invasive measurements within parallel monitoring of multiple samples. A wide variety of luminescent sensing probes using ion-sensitive indicators have been developed for sensing, imaging, and biomedical applications. Here we report a new sensitive element based on excitation energy transfer from donor (rhodamine 6G derivate) to acceptor (microalgae). The concepts and advantages of rhodamine-to-microalgae energy transfer-based sensor systems were highlighted.
Dendrimeric rhodamine-derived chemosensor (POSS-Rh8) for highly selective determination of Au in aqueous acidic solutions has been developed. The response mechanism is based on the catalytic destruction of the dendrimeric molecule what provide fluorescence enhancement via reducing intramolecular quenching. The probe exhibits linear signal response and allows determination of Au content in aqueous solutions from 2·10-7 M.
A novel turn on/off rhodamine 6G based fluorescent probe has been developed for selective detection of Au and Pd complexes in aqueous acidic solutions utilizing rhodamine spirolactam ring-opening process. Rhodamine derivatives have been widely used as versatile platforms for fluorescent probes. The newly designed probe reacts with [AuCl4]- and [PdCl4]2- to generate a product that has distinctly different optical properties. The probe undergoes a remarkable change in its absorption and emission spectrum upon addition of Au and Pd complexes that is associated with a discoloration and quenching of probe fluorescence. The probe exhibits near linear signal response and allows determination of Au and Pd content in aqueous solutions from 0.1 μM.
Here we report a novel luminescent sensor for amines and ammonia based on Eu(III) tris-β-benzoylacetonate complexes obtained in various conditions. It has been revealed that interaction of Eu(III) tris-β-benzoylacetonate with analyte vapor results in increase of the Eu(III) luminescence intensity. Exposure of Eu(III) complexes to ammonia and methylamine vapors results in a rapid increase of the emission and excitation spectra intensity and a rapid recovery, almost to the initial value, when the sample is exposed to air. Moreover, luminescence decay time value of Eu(III) complexes is in dependence on analyte presence and increase in ammonia atmosphere and decrease under purging of pure air. The dependences of sensor response features upon preparation conditions were shown. The mechanism of the analyte vapors effect on Eu(III) luminescence intensification has been suggested using the data of IR spectroscopy and quantum chemistry calculations. The mechanism of luminescence sensitization consists in bonding of an analyte molecule with a water molecule into the coordination sphere of Eu(III). As a result, the bond of a water molecule with the luminescence center weakens and the blockage of the quenching of luminescence on OH-vibrations takes place. The obtained data can be used for development of sensor materials with selective optical sensitivity to ecologically harmful vapours of organic and inorganic compounds.
Here, we report the studies of thermal treatment effect on the structural and optical properties of nanocomposites based on cadmium sulfide quantum dots embedded in a silicate matrix. An explanation of the mechanism of reversible photoinduced absorption of the nanocomposite has been given. It is found that heating at 180°C results in significant changing of nanocomposite absorption and luminescence spectra caused by structural changes of quantum dots. It is found that photoinduced optical absorption of the nanocomposite is caused by amorphous-structured cadmium sulfide quantum dots.
Here we report on preparation of planar optical waveguides based on chitosan (DD=80.5%, MW=500kDa) in different
salt forms, chitosan/gold nanoparticles, chitosan/gold nanoparticles/silica hybrids with layered structure and modification
of Na/K ion-exchange waveguides with thin chitosan/carrageenan multilayers. Chitosan-based optical waveguides with
thickness of 0.5- 1.5 μm were obtained on quartz, glass and MgF2 substrates by spin-coating and dip-coating. For
investigation of optical properties, light (wavelength 632 or 532 nm) was coupled into the planar waveguide via the flint
glass prism using goniometer. A number of modes, effective refractive index, waveguide propagation losses were
determined for all samples in the range of relative humidity 10-99%.
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