Photoreductive dissolution of cerium oxide nanoparticles and their size-dependent absorption properties.

Cerium oxide has attracted attention recently for its photocatalytic properties, but there are gaps in understanding its performance, especially at low and high pH. UV irradiation of ceria nanoparticles causes electrons from photogenerated electron-hole pairs to localize as small polarons, yielding Ce3+ ions. In pH 10 solution, ceria nanoparticles capped with polyacrylic acid ligands can accumulate large numbers of Ce3+ defects as revealed by strong bleaching of the absorption onset.

Probing eumelanin photoprotection using a catechol:quinone heterodimer model system.

Eumelanin is a natural pigment with photoprotective and radical scavenging characteristics, which are vital for a multitude of living organisms. However, the molecular mechanisms behind these functions remain obscure, in part because eumelanin is a heterogeneous polymer composed of a complex assortment of structural and chemical domains. Despite uncertainty about its precise structure, the functional units of eumelanin are thought to include quinones in various oxidation states.

Gallium indium eutectic masking prior to porous silicon formation creates unique spatially-dependent chemistries.

We demonstrate that gallium indium (GaIn) eutectic can be used to create interesting crystalline Si/porous silicon (cSi/pSi) platforms that exhibit unique analyte- and spatially-dependent photoluminescence (PL) responses. Here we characterize these cSi/pSi regions by using profilometry, scanning electron microscopy (SEM), wide-field PL microscopy, and Fourier transform infrared (FTIR) microscopy. As we move along a vector from the cSi/pSi interface out into "bulk" pSi, the: (i) analyte-dependent, PL-based response initially increases and then decreases; (ii) total PL emission intensity, in the absence of analyte, increases; (iii) pSi thickness increases; and (iv) relative OSi-H to Si-H band amplitude ratio decreases.