In-situ synthesis of CN@La(OH)3 nanocomposite for improved the charge separation and enhanced the photocatalytic activity towards Cr(VI) reduction under visible light

In this work, we report for the first time a novel graphitic carbon nitride (CN) composited with different weight percentages (5–15%) of La(OH)3 (CN@La(OH)3) for photocatalytic reduction of hexavalent chromium (Cr(VI)) in aqueous solution. In situ fabrication of the CN@La(OH)3 photocatalysts were carried out via a hydrothermal method. The La(OH)3 nanoparticles were deposited onto the surface of CN nanosheets to form heterojunction, as confirmed by series of techniques. Compared to the pure CN and different weight percentages of CN@La(OH)3 nanocomposite, the CN@La(OH)3(10%) nanocomposite exhibited remarkable photocatalytic reduction performance for Cr(VI) under visible light illumination. Such excellent photocatalytic reduction activity ascribed to the more photocatalytic active sites, high visible light harvesting capacity and improved electron-hole separation and transfer efficiency which was confirmed by photocurrent, impedance and photoluminescence results. The photoreduction efficiency and the reduction rate constant was 98.7% and 0.0263 min−1 within 50 min. A possible reaction mechanism for the effective reduction of carcinogenic Cr(VI) is put forward tentatively. Moreover, the developed CN@La(OH)3(10%) nanocomposite also possessed high structural stability and recyclability after five photocatalytic cycles. This work may open up the way into the robust photocatalysis of Cr(VI) in wastewater treatment application

Micro-Raman Scattering of Nanoscale Silicon in Amorphous and Porous Silicon

The size effect of nanoscale silicon in both amorphous and porous silicon was investigated with micro-Raman spectroscopy. Silicon nanostructures in amorphous silicon were deposited on quartz substrates by plasma enhanced chemical vapor deposition (PECVD) with deposition powers of 15, 30 and 50 W. Micro-Raman spectra of the nanostructured silicon show the T2g Raman active mode shifting from the 521 cm-1 crystalline Si Raman line to 494, 499 and 504 cm-1 as deposition power increased. Large Raman mode shifts, up to 27 cm-1 and broadening up to 23 cm-1 of the T2g Raman-active mode is attributed to a phonon confinement effect. The analysis of micro-Raman scattering data is useful to understand the role of deposition condition of the silicon sample. In addition, micro-Raman scattering intensity of porous silicon prepared using various current densities such as 10, 50 and 125 mA/cm2 has also been investigated. The effect of phonon confinement on the nanoscale porous silicon has been quantified. The relationship between Raman shift and stress on the porous silicon has been evaluated

Micro-Raman scattering of nanoscale silicon in amorphous and porous silicon

The size effect of nanoscale silicon in both amorphous and porous silicon was investigated with micro-Raman spectroscopy. Silicon nanostructures in amorphous silicon were deposited on quartz substrates by plasma enhanced chemical vapor deposition (PECVD) with deposition powers of 15, 30 and 50 W. Micro-Raman spectra of the nanostructured silicon show the T2g Raman active mode shifting from the 521 cm−1 crystalline Si Raman line to 494, 499 and 504 cm−1 as deposition power increased. Large Raman mode shifts, up to 27 cm−1 and broadening up to 23 cm−1 of the T2g Raman-active mode is attributed to a phonon confinement effect. The analysis of micro-Raman scattering data is useful to understand the role of deposition condition of the silicon sample. In addition, micro-Raman scattering intensity of porous silicon prepared using various current densities such as 10, 50 and 125 mA/cm2 has also been investigated. The effect of phonon confinement on the nanoscale porous silicon has been quantified. The relationship between Raman shift and stress on the porous silicon has been evaluated