Influence of barium substitution on the physical, thermal, optical and luminescence properties of Sm3+-doped metaphosphate glasses for reddish orange light applications.

Our present study focuses on examining the thermal, structural and luminescent characteristics of sodium barium metaphosphate glasses doped with Sm3+. Glass samples with molar compositions (100 - y)[(50P2O5)-(50-xNa2O)-(xBaO)]-ySm2O3, where x = 20, 25, 30, 35, 40 and y = 0.3 and 1% were first synthesized by conventional melt quenching and later dehydroxylated under a constant N2 flow to ensure final glasses with a very high degree of chemical and optical homogeneity and free of water. Upon the addition of BaO and Sm2O3, refractive index, molar mass, density, glass transition temperature and dilatometric softening temperature exhibited an increase, whereas the coefficient of thermal expansion showed a decrease. The FTIR spectra analysis reveals a network depolymerization that intensifies with rising BaO concentration, ultimately transitioning from a modifier oxide to a glass-forming element, at higher BaO concentrations. All doped samples exhibited prominent absorption bands in the visible (VIS) and near-infrared (NIR) regions, as revealed by the optical absorption spectra. The Na2O modifier demonstrated greater influence on Sm3+ emission compared to BaO, a phenomenon that can explained by the moderation of the local ligand field strength resulting from this substitution. With an increase in Sm2O3 concentration from 0.3 to 1 mol%, the experimental lifetimes of the 4G5/2 level decrease, primarily attributed to the presence of energy transfer mechanisms. A discussion of Judd-Ofelt parameter analysis and glass radiation properties will be presented.

Chitosan-Ag-TiO2 films: An effective photocatalyst under visible light.

Aiming the degradation of harmful molecules under visible light, new photocatalytic systems were created. For this purpose, the surface of chitosan thin films was modified in heterogeneous phase via a simple and straightforward mild chemical process: chemisorption of silver ions followed by the synthesis in situ of TiO2 at low temperature (100 °C). A high photocatalytic activity under visible light was observed, leading to the degradation and/or mineralization of different organic products such as o-toluidine, salicylic acid and 4-aminomethyl benzoic acid. This efficiency is partly attributed to the formation of Ag NPs and also to the unexpected appearance of AgCl NPs, likely formed from the residual chlorine contained in the chitosan. The resulting TiO2/Ag/AgCl/Chitosan system is easy to prepare under mild conditions, avoiding calcination treatments and opens new perspectives for the production of visible light-driven photocatalysts. Samples were analysed by different techniques: XRD, Raman, FE-SEM, XPS, TGA, GSDR, LIF and LIP.

Desmoplastic spitz nevus: report of a case and review of the literature.

Desmoplastic spitz nevus (DSN) is an uncommon melanocytic lesion. The histologic features of this benign tumour may mimic those of certain benign (dermatofibroma and desmoplastic cellular blue nevus) or malignant (metastatic carcinoma and malignant melanoma) neoplasms. We report the case of a male with a DSN, and also review the clinical characteristics, histologic features and differential diagnosis of this extremely rare lesion. The lesion is identified as an asymptomatic reddish-brown dome-shaped papule on the forearm. Microscopic examination showed a symmetric lesion in the dermis. The neoplastic cells were large and epithelioid-shaped, and were either isolated as individual cells or arranged in small nests in a paucicellular hyalinized stroma. Nuclei were large and vesicular with small nucleoli and no mitoses. Diffuse expression of S100 and the absence of staining with antibodies to melan-A and HMB45 was observed. A diagnosis of DSN with free margins was made. The histologic presentation of this benign lesion mimics both benign and malignant neoplasms. The immunohistochemical profile (S100 positive, HMB-45 negative and cytokeratin negative) may be helpful to differentiate it from other lesions.

Spin relaxation quenching in semiconductor quantum dots.

We have studied the spin dynamics in self-organized InAs/GaAs quantum dots by time-resolved photoluminescence performed under strictly resonant excitation. At low temperature, we observe strictly no decay of both the linear and the circular luminescence polarization. This demonstrates that the carrier spins are totally frozen on the exciton lifetime scale.