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Abstract 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, $${\Omega }_2$$ Ω 2 , 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 ( $$\sim 1.0\,\upmu {\text {m}})$$ ∼ 1.0 μ m ) 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+: $$^3F_2 \rightarrow ^3H_4$$ 3 F 2 → 3 H 4 ( $$\sim 2.0\,\upmu$$ ∼ 2.0 μ m) were comparatively reported suggesting that the glass with molar composition 0.5Pr3+/0.1Yb3+ might be a potential candidate for $$\sim 2.0\,\upmu$$ ∼ 2.0 μ m laser operation with low pump threshold.

Abstract 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 $$^{2+}$$ 2 + (5 wt%) doped phosphate glass and Zn $$_{1-x}$$ 1 - x Ni $$_x$$ x Te (x = 0.5, 1.0, 5.0 and 10.0 wt% of Ni $$^{2+}$$ 2 + ) nanocrystals (NCs) doped phosphate glasses (GCs) were prepared by fusion method and subsequent heat treatment. Influence of Ni $$^{2+}$$ 2 + 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 $${\pm }$$ ± 0.3 nm and 13.4 $${\pm }$$ ± 0.2 nm, respectively. Several phosphate groups were observed and reported from Raman and FTIR-ATR spectra. The absorption band positions confirmed that Ni $$^{2+}$$ 2 + ions resemble to the octahedral symmetry. The intensity of absorption band around 1352 nm ( $$^3$$ 3 T $${_1}$$ 1 (F) $$\rightarrow$$ → $$^3$$ 3 A $${_2}$$ 2 (F)) increased with the increase of Ni $$^{2+}$$ 2 + in GCs which is an indicative of the $$^{[6]}$$ [ 6 ] Ni $$^{2+}$$ 2 + coordination. The emission properties such as emission cross-sections ( $${\sigma }_{emi}$$ σ emi ) full width at half maxima (FWHM) for the $$^1$$ 1 T $${_2}$$ 2 (D) $$\rightarrow$$ → $$^3$$ 3 T $${_2}$$ 2 (F) (visible) and $$^3$$ 3 A $${_2}$$ 2 (F) $$\rightarrow$$ → $$^3$$ 3 T $${_1}$$ 1 (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 $$^{2+}$$ 2 + ) are the largest for both the visible (11.88 $$\times$$ × 10 $$^{-18}$$ - 18 cm $$^2$$ 2 ) and infrared (0.98 $$\times$$ × 10 $$^{-20}$$ - 20 cm $$^2$$ 2 ) 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 $$^{2+}$$ 2 + 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 ( $$\beta$$ β ) is observed from GC2 (2.53 $${\times }$$ × 10 $$^{-10}$$ - 10 cm/W) to GC4 (7.98 $${\times }$$ × 10 $$^{-10}$$ - 10 cm/W). The GC4, sample with 10 wt% of Ni $$^{2+}$$ 2 + , showed the lowest ds/dT (1.22 $$\times$$ × 10 $$^{-6}$$ - 6 K $$^{-1}$$ - 1 ) 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.

Este trabalho apresenta o estudo e avaliação de um procedimento para detecção de fraudes com a diluição de água, cloreto de sódio e soda cáustica em leite, que se baseia no monitoramento da condutividade elétrica. Os resultados mostram um decréscimo linear da condutividade à medida que se acrescenta água. Por outro lado, a adição de soda cáustica e cloreto de sódio resultam em aumento da condutividade elétrica. Concluiu-se ser possível utilizar medidas de condutividade elétrica para a veri? cação de fraudes no leite com adição de água, cloreto de sódio e hidróxido de sódio, desde que estes não tenham sido acrescentados simultaneamente.

O trabalho apresenta a caracterização óptica do leite com o objetivo de quantificar sua composição por meio de uma técnica não invasiva, a absorção infravermelha por transforada de Fourier (FT-IR). As amostras foram diluidas com água e a densidade de gordura apresentou diminuição linear com o aumento da diluição com água.