The optical properties of lead sulfide quantum dots (QDs) of different sizes embedded in a nanoporous silicate glass matrix (NSM) are investigated by steady-state and transient photoluminescence spectroscopy. The use of this matrix allows the fabrication of samples with reproducible optical characteristics, for both isolated and close-packed QDs. Low-temperature PL analysis of isolated QDs with sizes of 3.7 and 4.5 nm shows that the coefficient of temperature shift of the PL position changes sign with reducing QD size because of size-dependent contributions from thermal expansion, mechanical strain, and electron–phonon coupling. The PL intensity is determined by size-dependent splitting of the lowest energy electronic state.

Coherent anti-Stokes Raman scattering (CARS) spectroscopy is applied to diagnostics of phase behavior of a fluid in pores of nanoporous glasses. Samples with mean pore radii of 2 and 3.5 nm were filled with compressed carbon dioxide at near-room temperatures. CARS spectra of the 1388 cm −1 Q-branch were measured at isothermal compressing in a wide pressure range including the transition from gaseous to condensed state. The spectra show specific transformations caused by fluid adsorption and condensation in nanopores. We have carried out calculations of the spectral profiles based on the phase behavior of carbon dioxide in cylindrical glass nanopores. Phase behavior modeling was performed using thermodynamic concepts of surface adsorption and capillary condensation. A good agreement between experimental spectra and calculations was obtained. The potential of CARS technique for the diagnostics of fluid phase behavior in pores and for the characterization of nanoporous host structure is discussed.

quantum yields (PLQY), and wide tunability, combined with low material costs. [10,11] In which case the identification of an appropriate metal NIR plasmonic nanostructure is the next challenge, with only some complex gold nanostructures, such as tetrapods, [12] nanorods, [13] nanocages, [14] nanostars, [15] and faceted gold nanoparticles [16] can be cited. However, their plasmonic resonance bands are still limited in their tunable range to no longer than 1.0 µm and in addition their commercial manufacturing is highly costly. More recently, semiconductor nanocrystals with plasmonic features have attracted much attention, [17][18][19][20] with one particular example, copper deficient copper chalcogenides, [21][22][23][24][25][26][27] offering tunable plasmonic bands covering a wide range of the NIR. Plasmonic resonance in such semiconductor plasmonic nanocrystals (PNCs) arises from the excess of free holes and can be easily and reversibly tuned throughout the entire NIR spectral range. Although it is expected that near-field enhancement of optical responses by such PNCs will be less effective as compared to the noble metals in the visible range due to the smaller number of free carriers, [18] there are a few encouraging reports for PNC enhanced Raman scattering [28] and upconversion visible emission. [29] Despite the huge potential of plasmonic enhancement of NIR optical responses, especially NIR absorption and photoluminescence (PL), this topic has not been studied as of yet, with copper chalcogenides PNCs considered mostly for thermal therapy. [18,20] To realize a miniature NIR emitter which exploits plasmonic enhancement of radiation, an appropriate matrix must be selected. Such a matrix must provide optical transparency and high loading of nanoscale emitters. Importantly, the emitters and PNCs should be separated from each other to prevent PL quenching by means of nonradiative energy transfer. [1,30] At the same time, the distance between the emitter and PNC should be short enough (≈5-20 nm) to provide an effective enhancement. [1] The nanoporous silicate matrix (NSM) can satisfy these demands. [31,32] Its porous structure provides the separation between embedded QDs and PNCs, while high porosity allows the high loading of the nanoparticles.Nowadays PbS QDs are considered as a promising material for NIR photovoltaic and light-emitting devices. [33][34][35][36][37] However, the efficiency of the PbS QD light emitters is still far behind that for visible QDLEDs. [38,39] Here we report high (up to ≈20 times Strong enhancement of near-infrared (NIR) emission of lead sulfide quantum dots (QDs) induced by Cu 2−x Se semiconductor plasmonic nanocrystals (PNCs), both embedded into nanoporous silicate matrix is reported. The emission enhancement comes from resonant interaction of QD optical transition dipole with the near field of plasmons of semiconductor PNCs. Possible mechanisms of QD photoluminescence broadening and shift, including Rabi splitting and trap-state-related photoluminescence enhancement, are considered. ...

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Experimental research into changes of the optical thickness of phenanthrenequinone-doped polymethyl methacrylate samples in the process of irradiation by a 473 nm laser is presented. It was demonstrated that heating-induced reversible changes lead to a decrease in the optical thickness. The temperature coefficient of the relative changes of the optical thickness was measured to be -1.40×10 К, which matches the data published by other authors. It is also established that the irreversible changes induced by the photochemical transformation lead to an increase in the optical thickness outside of the absorption band of the samples (λ>530  nm), where the relative change of which at λ=532  nm is +3.7×10. It was demonstrated that the reversible and irreversible changes do not compensate for each other in the process of sample exposure.

The photoluminescence response of semiconductor CdSe/ZnS quantum dots embedded in a borosilicate porous glass matrix to exposure to ammonia vapor is investigated. The formation of surface complexes on the quantum dots results in quenching of the photoluminescence and a shortening of the luminescence decay time. The process is reversible, desorption of ammonia molecules from the quantum dot surface causes the photoluminescence to recover. The sensitivity of the quantum dot luminescence intensity and decay time to the interaction time and the reversibility of the photoluminescence changes make the CdSe/ZnS quantum dots in porous glass system a candidate for use as an optical sensor of ammonia.