Microporous and macro-mesoporous silicon templates for surface-enhanced Raman scattering (SERS) substrates were produced by anodization of low doped p-type silicon wafers. By immersion plating in AgNO3, the templates were covered with silver metallic film consisting of different silver nanostructures. Scanning electron microscopy (SEM) micrographs of these SERS substrates showed diverse morphology with significant difference in an average size and size distribution of silver nanoparticles. Ultraviolet-visible-near-infrared (UV-Vis-NIR) reflection spectroscopy showed plasmonic absorption at 398 and 469 nm, which is in accordance with the SEM findings. The activity of the SERS substrates was tested using rhodamine 6G (R6G) dye molecules and 514.5 nm laser excitation. Contrary to the microporous silicon template, the SERS substrate prepared from macro-mesoporous silicon template showed significantly broader size distribution of irregular silver nanoparticles as well as localized surface plasmon resonance closer to excitation laser wavelength. Such silver morphology has high SERS sensitivity that enables ultralow concentration detection of R6G dye molecules up to 10(-15) M. To our knowledge, this is the lowest concentration detected of R6G dye molecules on porous silicon-based SERS substrates, which might even indicate possible single molecule detection.

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The mechanisms of light-activated bleaching procedures had a significant effect on the color change. The bleaching activation with LED405 and higher concentrations of peroxide in bleaching agents promoted better whitening effect.

Abstract. Oxidation of iron plates (α-phase) at high temperatures and in atmospheric conditions was monitored. The composition of oxidation products was analyzed with XRD, Raman and Mössbauer spectroscopies, whereas the morphologies of oxidation products were inspected by FE-SEM.

Light emitting porous silicon samples with different porosities, i.e. crystalline sizes, were produced from the low level doped p‐type silicon wafers by the anodization process. The effects of strong phonon confinement, redshift and broadening, were found on the O(Γ) phonon mode of the Raman spectra recorded at non‐resonant excitation condition using a near infrared 1064 nm laser excitation wavelength. Similarly, the blueshift of the photoluminescence peak was observed by reducing the crystalline sizes. Vibrational and optical findings were analysed within the existing models of confinement on the vibrational and electronic states of silicon nanocrystals. Since the energy of the photoluminescence peak of small nanocrystals also depends on the oxygen content on the surface of nanocrystals, the surface oxidation states were examined using infrared and energy dispersive spectroscopy. The partial coverage of the surface of nanocrystals was found due to the sample exposure to air. As a consequence, the photoluminescence energy did not increase as would be expected from the quantum confinement model. These results further indicate that the oxygen passivation along with the quantum confinement determines the electronic states of the silicon nanocrystals in porous silicon. Copyright © 2014 John Wiley & Sons, Ltd.