The fluorescence enhancement factor of the conjugate of immunoglobulin G labeled with fluorescein isothiocyanate (IgG-FITC) as an immunofluorescent marker was optimized as a function of the optical and topographic parameters of a colloidal silver film on the surface of a standard polystyrene immunoassay plate. The factors influencing fluorescence enhancement were identified. The fluorescence enhancement was shown to be a plasmon-resonance process by using time-resolved spectroscopy, analysis of fluorescence excitation spectra, and enzyme immunoassay determination of the relative concentrations of IgG-FITC adsorbed on the solid phase. The optical density of the silver colloidal film at the excitation and emission wavelengths of IgG-FITC was the most important parameter correlated with the fluorescence enhancement factor. The maximum enhancement factor of 10.2 times was obtained for silver films with the highest optical density.

The use of plasma-assisted synthesis of effective plasmonic photocatalysts for degradation of aqueous organic pollutants is limited by a lack of understanding of the effects of plasma treatment on the properties of plasmonic nanoparticles. In this study, the effect of cold atmospheric plasma on the optical properties of plasmonic silver (Ag) nanoparticles was investigated. Silver nanoparticles were deposited on quartz surfaces and treated by dielectric barrier discharge plasma for various time. The plasma treated Ag nanoparticles were characterized using UV-visible spectroscopy technique.

A study was carried out and a comparative analysis of the spectral-kinetic (absorption and fluorescent) characteristics of nanospheres containing luminescent inorganic quantum dots (QDs) CdSe/ZnS, covered with an amphiphilic polymer shell, which ensures the stability of nanospheres in aqueous colloidal solutions and the possibility of introducing into them hydrophobic photochromic diarylethene molecules with different structure. Photoinduced reversible isomerization of diarylethene molecules causes modulation of the photoluminescence signal of quantum dots, including through the control of the efficiency of resonant energy transfer (FRET) from quantum dots to the cyclic isomer of diarylethene. The FRET efficiency turned out to be the highest in nanospheres with DAE2 and DAE4. The value of the quality index (QF) of the FRET photomodulator (which shows the efficiency of modulation of the quantum yield of QD photoluminescence), introduced in this work, varies for samples with different diarylethenes from 0.003 (for DAE1) to 0.09 (for DAE2). Nanospheres containing luminescent nanoparticles of various shapes can be used in the development of luminescent photocontrolled panels, fluorescent markers, etc.

A study was carried out and a comparative analysis of the spectral-kinetic (absorption and fluorescent) characteristics of nanospheres containing luminescent inorganic quantum dots (QDs) CdSe/ZnS, covered with an amphiphilic polymer shell, which ensures the stability of nanospheres in aqueous colloidal solutions and the possibility of introducing into them hydrophobic photochromic diarylethene molecules with different structure. Photoinduced reversible isomerization of diarylethene molecules causes modulation of the photoluminescence signal of quantum dots, including through the control of the efficiency of resonant energy transfer (FRET) from quantum dots to the cyclic isomer of diarylethene. The FRET efficiency turned out to be the highest in nanospheres with DAE2 and DAE4. The value of the quality index (QF) of the FRET photomodulator (which shows the efficiency of modulation of the quantum yield of QD photoluminescence), introduced in this work, varies for samples with different diarylethenes from 0.003 (for DAE1) to 0.09 (for DAE2). Nanospheres containing luminescent nanoparticles of various shapes can be used in the development of luminescent photocontrolled panels, fluorescent markers, etc. Keywords: quantum dots, fluorescence, Forster resonance energy transfer, nanocomposites, photochromism, diarylethenes.

The kinetics of caffeine photodegradation is investigated in the presence of nanostructured ZnO-based catalysts.

In this study, a low-pressure plasma is employed for the synthesis and modification of TiO2-based photocatalysts. The commercially available TiO2 nanoparticles were impregnated with a Ruthenium-based photosensitizer (N3). The samples were subsequently exposed to a plasma to promote the formation of a plasma-polymerized poly-allyl layer. A plasma was excited by a radio frequency (RF) power source. Argon (Ar) was used as a carrier gas. Photocatalytic activity of samples was investigated in the photodegradation of methyl orange (MO) and caffeine in aqueous solution under ultraviolet irradiation. Comparison of catalysts activity was performed between N3-containing 110, covered with a polymer layer, TiO2 covered with a polymer layer, and Ar-RF plasma treated and untreated TiO2. The rate constant of photodegradation was used to express the catalytic reactivity of the catalyst. The maximal value of the rate constant of MO degradation reaction was found to be 1.1 x 10(-2 )s(-1) for TiO2 covered with a poly-allyl layer. The value of rate constant was 4.4 times higher for TiO2 covered with polymer layer than that for untreated TiO2. However, for caffeine photodegradation reaction, no increase in catalytic activity was observed for modified TiO2. The difference in catalytic performance in the photodegradation of MO and caffeine may be caused by differences in the reaction mechanism. Enhancement of photocatalytic activity toward MO photodegradation by coating of TiO2 with poly-allyl layers might be due to the photogenerated electron transfer from polymer to TiO2. The catalysts were characterized by the time resolved photoluminescence and infrared spectroscopy.

Here we report, for the first time to our knowledge, the plasma modification of ZnO-based photocatalysts impregnated with silver nanoparticles (Ag NPs). Plasma-treated semiconductors have been recently proposed as effective catalysts for photodegradation of methyl orange (MO) in aqueous solution. Whereas effects of plasma treatment on activity of catalysts doped with a metal atom have been investigated, the effects of plasma treatment on the performance of catalysts doped with metal nanoparticles (NPs) have not yet been studied. In this study, ZnO microparticles were impregnated with Ag NPs. Impregnated catalysts were prepared by a wet impregnation method followed by plasma treatment. For this purpose, dielectric barrier discharge (DBD) plasma was applied. The photocatalytic degradation of methyl orange was investigated under ultraviolet (UV) light irradiation in the presence of aqueous suspension of Ag-NPs-impregnated ZnO. The catalysts were characterized by photoluminescence (PI) spectroscopy, scanning electron microscopy (SEM) combined with energy dispersive X-ray spectroscopy (EDX), infrared spectroscopy (IR), and UV-Vis spectroscopy. The presence of silver in ZnO was established by the inductively coupled plasma atomic emission spectrometry (ICP-AES) technique. A diminished catalytic activity was observed after impregnation with Ag NPs. A subsequent treatment by DBD plasma leads to the enhancement of catalysts' performance. The photocatalytic activity, expressed in terms of rate constants of photodegradation of methyl orange, was approximately 3 times higher for synthesized samples than that for untreated ZnO.