Application of molecular dynamics techniques and luminescent probes to the study of glass structure: the SiO2–GeO2 case

In this paper, we report on the results obtained from molecular dynamic simulation of a Eu3+-doped germanosilicate glass. This simulation provides further information on the structure. In particular it reveals a homogeneous distribution of SiO4 and GeO4 units, a decrease of defects compared to SiO2 and GeO2 glasses, and a trend to clustering of the doping ions. Using the modified crystal-field theory, the luminescence spectroscopic properties have been computed and comparison with experimental data has allowed a correlation of the spectral features with two main types of local environment depending on the coordination number and on the medium-range arrangement around the doping ions

Population pharmacokinetics of nalbuphine after surgery in children

International audienceBACKGROUND : Nalbuphine is an opioid analgesic agent widely used for control of mild-to-severe pain. However, limited data are available on the pharmacokinetics of this drug in children. The aim of this study was to characterize the population pharmacokinetics of nalbuphine in patients with ages ranging from 1 to 11 yr and to identify patient characteristics partially explaining inter-individual variability in nalbuphine pharmacokinetic parameters.METHODS : Twenty-two children were included in this study. They received nalbuphine after surgery by continuous infusion (loading dose, 0.2 mg kg(-1) over 10 min followed by continuous infusion of 0.8 mg kg(-1) over 24 h). If pain relief was not adequate, 0.1 mg kg(-1) bolus doses were allowed in 10 min. Eleven blood samples were collected per patient. The data were analysed by non-linear mixed-effect modelling with the use of a two-compartment structural model.RESULTS : Twenty patients completed the study. In the final model, the parameter values were standardized for a body weight of 70 kg using an allometric model. Population parameter estimates were: clearance 130 litre h(-1) 70 kg(-1), inter-compartment clearance 75.6 litre h(-1) 70 kg(-1), central volume of distribution 210 litre 70 kg(-1), and peripheral volume of distribution 151 litre 70 kg(-1). In the children of this study, total clearance expressed in litre h(-1) kg(-1) decreased significantly with increasing age and the elimination half-life significantly increased.CONCLUSIONS : The allometric power model developed in this study best reflected the data and may be useful for dose adjustment

Wavelength shifting systems based on flavonols and their metal complexes encapsulated by post-doping in porous SiO₂ xerogel matrices

SiO2 xerogels with very low organic and silanol content have been doped with flavonols and flavonol-metal complexes through a post-doping encapsulation procedure. With a final aim of developing wavelength shifters, this work has shown that 3-hydroxyflavone (3HF) and Al(3HF)2+-doped xerogels have interesting luminescent properties. Moreover, spectroscopic characterization of these two doped xerogels shows that the encapsulation procedure does not significantly alter the emission properties of the dopant species. For 3HF-doped xerogels, emission studies and Raman analyses suggest that the encapsulated dye is surrounded by an apolar but inorganic nanoenvironment. This study demonstrates the possibility of obtaining organic fluorophor- and metal-complex fluorophor-doped xerogels with good optical properties fabricated by a simple soaking and drying post-doping procedure.</p

Investigating properties of semiconductor nanoparticles

International audienc

Wavelength shifting systems based on flavonols and their metal complees encapsulated by post-dopin in porous SiO2 xerogel matrices

<p>SiO₂ xerogels with very low organic and silanol content have been doped with flavonols and flavonol-metal complexes through a post-doping encapsulation procedure.</p> <p>With a final aim of developing wavelength shifters, this work has shown that 3-hydroxyflavone (3HF) and Al(3HF)₂⁺-doped xerogels have interesting luminescent properties. Moreover, spectroscopic characterization of these two doped xerogels shows that the encapsulation procedure does not significantly alter the emission properties of the dopant species. For 3HF-doped xerogels, emission studies and Raman analyses suggest that the encapsulated dye is surrounded by an apolar but inorganic nanoenvironment.</p> <p>This study demonstrates the possibility of obtaining organic fluorophor- and metal-complex fluorophor-doped xerogels with good optical properties fabricated by a simple soaking and drying post-doping procedure.</p

Kinetics of densification of porous silica gels: a structural and textural study

The present work is devoted to the structural analysis of silica xerogel samples containing controlled pore sizes ranging from 25 to 270 Å. It focuses on the kinetics of densification processes. Porous xerogels were treated in air at the fixed temperature of 1050 °C for periods varying from 10 min to 3 h and were allowed to cool down in open air. They were characterized by density and nitrogen adsorption–desorption measurements, as well as by Raman spectroscopy. The structural studies were based on the evolution of the intensities and profiles of certain characteristic bands in the Raman spectra. Among these are the two defects bands, D1 and D2 associated with the vibrations of four- and three-membered silica rings, respectively, and the ν(Si–O–Si) band centered at 430 cm−1. Analyses allowed a characterization of the structural changes occurring with densification of the amorphous matrix. In addition it was found that all modifications are brought to a halt after a characteristic time which depends on the initial porosity. It is important to note that the final microscopic structure is the same for all samples regardless of the initial pore size