Zn[Formula: see text]Ni[Formula: see text]Te semiconductor nanocrystals in transparent glass for optoelectronic device applications.

Doping glass with semiconductors, particularly with nanostructured semiconductors, has attracted attention due to the large optical absorption cross-sections of the latter. Based on this property, Ni[Formula: see text] (5 wt%) doped phosphate glass and Zn[Formula: see text]Ni[Formula: see text]Te (x = 0.5, 1.0, 5.0 and 10.0 wt% of Ni[Formula: see text]) nanocrystals (NCs) doped phosphate glasses (GCs) were prepared by fusion method and subsequent heat treatment. Influence of Ni[Formula: see text] on structural, thermo-optical and third-order nonlinear optical properties have been analysed through various spectroscopic characterizations. The XRD pattern of the glass (G) exhibits the amorphous nature of the host material while GCs exhibit not only amorphous halo but also the presence of quantum dots (QDs) or nanocrystals (NCs) phases. TEM analysis of the studied GCs samples confirm the presence of quantum dots (QDs) and bulk NCs with an average diameter of approximately 4.2 [Formula: see text] 0.3 nm and 13.4 [Formula: see text] 0.2 nm, respectively. Several phosphate groups were observed and reported from Raman and FTIR-ATR spectra. The absorption band positions confirmed that Ni[Formula: see text] ions resemble to the octahedral symmetry. The intensity of absorption band around 1352 nm ([Formula: see text]T[Formula: see text](F) [Formula: see text] [Formula: see text]A[Formula: see text](F)) increased with the increase of Ni[Formula: see text] in GCs which is an indicative of the [Formula: see text]Ni[Formula: see text] coordination. The emission properties such as emission cross-sections ([Formula: see text]) full width at half maxima (FWHM) for the [Formula: see text]T[Formula: see text](D) [Formula: see text] [Formula: see text]T[Formula: see text](F) (visible) and [Formula: see text]A[Formula: see text](F) [Formula: see text] [Formula: see text]T[Formula: see text](F) (near-infrared) emission transitions were reported. Among the glass-containing semiconductor nanocrystals (GCs), the emission cross-sections in GC4 sample (x = 10% of Ni[Formula: see text]) are the largest for both the visible (11.88 [Formula: see text] 10[Formula: see text] cm[Formula: see text]) and infrared (0.98 [Formula: see text] 10[Formula: see text] cm[Formula: see text]) transitions. Thermal diffusivity (D), thermal conductivity (K) and temperature dependent optical path length change (ds/dT) were obtained through time-resolved thermal lens (TL) and thermal relaxation (TR) methods. The D and K parameters do not change significantly with increase of Ni[Formula: see text] ions (0.5-5%) in GCs. Nonlinear-refractive index and nonlinear absorption of the studied samples were also obtained using femtosecond Z-scan technique. The increase of nonlinear absorption coefficient ([Formula: see text]) is observed from GC2 (2.53 [Formula: see text] 10[Formula: see text] cm/W) to GC4 (7.98 [Formula: see text] 10[Formula: see text] cm/W). The GC4, sample with 10 wt% of Ni[Formula: see text], showed the lowest ds/dT (1.22 [Formula: see text] 10[Formula: see text] K[Formula: see text]) with good lasing (FOM and emission cross-sections) and nonlinear absorption properties suggesting that it can be a good candidate for visible-red emission light conversion in LED technology.

Near-infrared quantum cutting luminescence in Pr3+/Yb3+ doped lead bismuth borate glass.

In this paper, thermally stable lead-bismuth-borate glasses were doped with 0.5 mol% of Pr3+ ions at several concentration levels of Yb3+ ions. Structural characterizations were performed via Raman, differential scanning calorimetry, optical absorption and fluorescence spectra. The Judd-Ofelt intensity parameter, [Formula: see text], of Pr3+ doped glass was comparatively higher than those from reported ones, which reflects the increase of co-valency and asymmetry of chemical bonds in the local environment of Pr3+. Near-infrared emission in 900-2200 nm wavelength range was recorded through 443 nm blue laser pumping. Visible to near-IR quantum cutting and concentration quenching mechanisms were discussed to understand the luminescent behaviour. Intense IR emission ([Formula: see text] features generated by absorbing one visible photon leads to quantum efficiencies close to 128% in Pr3+/Yb3+ co-doped samples which may improve the solar spectrum absorption and accordingly, increase the efficiency of c-Si solar cells. Emission cross-section, lifetime, figure of merit and gain bandwidth corresponding to Pr3+: [Formula: see text] ([Formula: see text]m) were comparatively reported suggesting that the glass with molar composition 0.5Pr3+/0.1Yb3+ might be a potential candidate for [Formula: see text]m laser operation with low pump threshold.

Evaluation of the effects of mild heat in bovine milk by time resolved fluorescence.

Heat treatment of milk and dairy products are indispensable for the dairy industry. This thermal processing intends to extend shelf life, improve quality of the milk and minimize the health risks associated with milk and dairy products. The use of time-resolved fluorescence techniques to identify conformation and structure changes ok milk fat and proteins could help understand the temperature effects in bovine milk. This study aimed to use fluorescence lifetimes to evaluate the effects of heating fresh cow milk up to 85 °C. We observed different tendencies for fluorescence lifetimes submitted to different heating temperatures. The longer lifetime values decreased for temperatures higher than room temperature until it reached a minimum value near 40 °C and it slowly increased again for temperatures higher than 40 °C, indicating two distinct processes. These results indicate that time-resolved fluorescence can assist on the analysis of heating effects in fluid milk.

Time resolved fluorescence of cow and goat milk powder.

Milk powder is an international dairy commodity. Goat and cow milk powders are significant sources of nutrients and the investigation of the authenticity and classification of milk powder is particularly important. The use of time-resolved fluorescence techniques to distinguish chemical composition and structure modifications could assist develop a portable and non-destructive methodology to perform milk powder classification and determine composition. This study goal is to differentiate milk powder samples from cows and goats using fluorescence lifetimes. The samples were excited at 315nm and the fluorescence intensity decay registered at 468nm. We observed fluorescence lifetimes of 1.5±0.3, 6.4±0.4 and 18.7±2.5ns for goat milk powder; and 1.7±0.3, 6.9±0.2 and 29.9±1.6ns for cow's milk powder. We discriminate goat and cow powder milk by analysis of variance using Fisher's method. In addition, we employed quadratic discriminant analysis to differentiate the milk samples with accuracy of 100%. Our results suggest that time-resolved fluorescence can provide a new method to the analysis of powder milk and its composition.