No abstract

No abstract

p-CuSCN/n-Fe 2 O 3 heterojunctions were electrochemically prepared by sequentially depositing α-Fe 2 O 3 and CuSCN films on FTO (SnO 2 :F) substrates. The α-Fe 2 O 3 and CuSCN films and the α-Fe 2 O 3 /CuSCN heterojunctions were characterized by Field Emission Scanning Electron Microscopy (FESEM), Energy-Dispersive X-ray spectroscopy (EDX), and X-Ray Diffraction (XRD). Pure crystalline CuSCN films were electrochemically deposited on α-Fe 2 O 3 films by fixing the SCN/Cu molar ratio in the electrolytic bath to 1:1.5 at 60 °C and at a potential of-0.4 V. The photocurrent measurements showed an increase of the intrinsic surface states or defects at the α-Fe 2 O 3 /CuSCN interface. The photoelectrochemical performance of the α-Fe 2 O 3 /CuSCN heterojunction was examined by chronoamperometry and linear sweep voltammetry techniques. It was found that the α-Fe 2 O 3 /CuSCN structure exhibits a higher photoelectrochemical activity when compared to α-Fe 2 O 3 thin films. The highest photocurrent density was obtained for α-Fe 2 O 3 /CuSCN films in 1 M NaOH electrolyte. This high photoactivity was attributed to the high active surface area and to the external applied bias;, which favors the transfer and the separation of the photogenerated charge carriers in α-Fe 2 O 3 /CuSCN heterojunction devices. The flat band potential and the donor density were found to be maximal for the heterojunction. These results suggest a substantial potential to achieve heterojunction thin films in photoelectrochemical water splitting applications.

Electrodeposition of gold into porous silicon was investigated. In the present study, porous silicon with ~100 nm in pore diameter, so-called medium-sized pores, was used as template electrode for gold electrodeposition. The growth behavior of gold deposits was studied by scanning electron microscope observation of the gold deposited porous silicon. Gold nanorod arrays with different rod lengths were prepared, and their surface-enhanced Raman scattering properties were investigated. We found that the absorption peak due to the surface plasmon resonance can be tuned by changing the length of the nanorods. The optimum length of the gold nanorods was ~600 nm for surface-enhanced Raman spectroscopy using a He–Ne laser. The reason why the optimum length of the gold nanorods was 600 nm was discussed by considering the relationship between the absorption peak of surface plasmon resonance and the wavelength of the incident laser for Raman scattering.

Using the easily applicable hydrothermal method Cr-doped hematite thin films have been deposited polycrystalline on conductive glass substrates. The hydrothermal bath consisted of an aqueous solution containing a mixture of FeCl3.6H2O and NaNO3 at pH = 1.5. The samples were introduced in an autoclave and heated for a fixed time at a fixed temperature and then annealed in air at 550ºC. The concentration of the incorporated Cr atoms (Cr 4+ ions) was controlled by varying the concentration of the Cr(ClO4)3 precursor solution, varied from 0 % to 20 %. All samples followed morphological and structural studies using field-emission scanning electron microscopy, high-resolution transmission electron microscopy and X-ray diffraction. Chronoamperometry measurements showed that Cr-doped hematite films exhibited higher photoelectrochemical activity than the undoped films. The maximum photocurrent density and incident photon conversion efficiencies (IPCE) were obtained for 16 at.% Cr-doped films. This high photoactivity can be attributed to both the large active surface area and increased donor density caused by Cr-doping in the α-Fe2O3 films. All samples reached their best IPCE at 400 nm. IPCE values for 16 at.% Cr-doped hematite films were thirty times higher than that of undoped samples. This high photoelectrochemical performance of Cr-doped hematite films is mainly attributed to an improvement in charge carrier properties.