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Iron oxide nanoparticles (Fe 3 O 4 , IONPs) are promising candidates for several biomedical applications such as magnetic hyperthermia and as contrast agents for magnetic resonance imaging (MRI). However, their colloidal stability in physiological conditions hinders their application requiring the use of biocompatible surfactant agents. The present investigation focuses on obtaining highly stable IONPs, stabilized by the presence of an oleic acid bilayer. Critical aspects such as oleic acid concentration and pH were optimized to ensure maximum stability. NPs composed of an iron oxide core with an average diameter of 9 nm measured using transmission electron microscopy (TEM) form agglomerates with an hydrodynamic diameter of around 170 nm when dispersed in water in the presence of an oleic acid bilayer, remaining stable (zeta potential of −120 mV). Magnetic hyperthermia and the relaxivities measurements show high efficiency at neutral pH which enables their use for both magnetic hyperthermia and MRI. [ABSTRACT FROM AUTHOR]

The thermal back isomerization of 5,5′,6,6′-tetrachloro-1,1′,3,3′-tetraethylbenzimidacarbocyanine cis photoisomers studied by nanosecond laser flash photolysis is reported in polar solvents and at different temperatures. The data show the formation of a cis isomer after laser excitation, which disappears afterwards in the microsecond timescale with first-order kinetics, forming again the trans conformer. The reaction rate constant does not depend on the solvent viscosity, but exhibits strong polarity dependence. Accordingly, the activation energy exhibits a parabolic polarity dependence, which is attributed to the charge transfer nature of the transition state. Such effect may be enhanced by stereochemical hindrance in the cis photoisomer. [Copyright &y& Elsevier]

Poly(3,4-ethylenedioxythiophene) (PEDOT) has been electrochemically polymerized from 3,4-ethylenedioxythiophene (EDOT) monomers through a vertically oriented mesoporous silica matrix previously formed on FTO electrodes. The mesoporous silica thin films with pore channels of 3 nm in diameter, closely packed in a hexagonal arrangement, were obtained by electrochemically-assisted self-assembly (EASA). The mesoporous silica/PEDOT films were characterized by SEM and TEM microscopy and by cyclic voltammety. They were also used to construct electrochromic devices (ECDs), which were fully characterized for switching speed, coloration efficiencies, and cycling and voltammetric responses. [ABSTRACT FROM AUTHOR]

Abstract: Soda-lime glasses doped with Eu3+ were synthesized using a variety of compositions, namely changing the fraction of CaO or Eu2O3. Those glasses were characterized with several techniques, including ellipsometry, UV–vis–NIR absorption spectroscopy, steady-state photoluminescence spectroscopy and time-resolved luminescence. The compositions' effects on optical properties such as refraction indexes, Eu3+ oscillator strengths and luminescence lifetimes were accessed from the analysis of the experimental results. Judd–Ofelt theory was used to analyze all these aspects, which allow the detection of a mismatch of optical properties from absorption and emission spectroscopy. This mismatch was confirmed from the time-resolved data, showing the existence of two different spectroscopic Eu3+ species. From those results it is concluded that there is evidence for lanthanide aggregation, giving rise to self-quenching effects that may be described through resonance energy transfer mechanisms. The difference between luminescence lifetimes for isolated and aggregated Eu(III) is interpreted as due to different interactions with oxygen in the matrix, namely degree of covalency of the Eu–O bond and point group symmetry of the lanthanide. [Copyright &y& Elsevier]