Nickel nanowires have been formed by stationary electrochemical deposition of nickel into mesoporous silicon templates from the modified Watts bath. Monitoring of the porous silicon potential during the electrochemical deposition has given the determination of the emergence of Ni on the outer surface of porous layer. Maximum filling factor of porous silicon with Ni has been achieved to 67%. The pore dimensions have been found to define the length and diameter of the Ni nanowires that have equaled to 10 mu m and 100-120 nm, respectively. The polycrystalline nature of the nickel nanowires, as well as the expansion of nickel lattice constant in comparison with bulk material has been established by analyzing the X-ray diffraction spectra. The synthesized samples have possessed ferromagnetic properties, which have been confirmed by temperature measurements of the magnetization. Smaller values of the specific magnetization of the Ni/PS samples and the atomic magnetic moment of Ni atoms at the low temperature with respect to those of bulk material have been suggested to be mostly caused by formation of nickel silicide at the beginning of the Ni electrochemical deposition. (C) 2012 The Electrochemical Society. [DOI: 10.1149/2.050210jes] All rights reserved
Copper (II) sulfate was used as a source of copper to achieve uniform distribution of Cu particles deposited on porous silicon. Layers of the porous silicon were formed by electrochemical anodization of Si wafers in a mixture of HF, C3H7OH and deionized water. The well-known chemical displacement technique was modified to grow the copper particles of specific sizes. SEM and XRD analysis revealed that the outer surface of the porous silicon was covered with copper particles of the crystal orientation inherited from the planes of porous silicon skeleton. The copper crystals were found to have the cubic face centering elementary cell. In addition, the traces of Cu2O cubic primitive crystalline phases were identified. The dimensions of Cu particles were determined by the Feret's analysis of the SEM images. The sizes of the particles varied widely from a few to hundreds of nanometers. A phenomenological model of copper deposition was proposed.
We registered surface enhanced Raman scattering (SERS) spectra of the human lactoferrin molecules adsorbed on a silvered porous silicon (por-Si) from 10−6–10−18 M solutions. It was found that the por-Si template causes a negative surface potential of silver particles and their chemical resistivity to oxidation. These properties provided to attract positively charged lactoferrin molecules and prevent their interaction with metallic particles upon 473 nm laser excitation. The SERS spectra of lactoferrin adsorbed from 10−6 M solution were rather weak but a decrease of the concentration to 10−10 M led to an enormous growth of the SERS signal. This effect took place as oligomers of lactoferrin were broken down to monomeric units while its concentration was reduced. Oligomers are too large for a uniform overlap with electromagnetic field from silver particles. They cannot provide an intensive SERS signal from the top part of the molecules in contrast to monomers that can be completely covered by the electromagnetic field. The SERS spectra of lactoferrin at the 10−14 and 10−16 M concentrations were less intensive and started to change due to increasing contribution from the laser burned molecules. To prevent overheating the analyte molecules on the silvered por-Si were protected with graphene, which allowed the detection of lactoferrin adsorbed from the 10−18 M solution.
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