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Surface-enhanced Raman spectroscopy (SERS) is a promising optical method for analyzing molecular samples of various nature. Most SERS studies are of an applied nature, indicating a serious potential for their application in analytical practice. Dendritelike nanostructures have great potential for SERS, but the lack of a method for their predictable production significantly limits their implementation. In this paper, a method for controllably obtaining spatially separated, self-organized, and highly-branched silver dendrites via template synthesis in pores of SiO2/Si is proposed. The dendritic branches have nanoscale roughness, creating many plasmon-active "hotspots" required for SERS. The first held 3D modeling of the external electromagnetic wave interaction with such a dendrite, as well as experimental data, confirms this theory. Using the example of a reference biological analyte, which is usually used as a label for other biological molecules, the dendrites' SERS-sensitivity up to 10−15M was demonstrated with an enhancement factor of 108. The comparison of simulation results with SERS experiments allows distinguishing the presence of electromagnetic and chemical contributions, which have a different effect at various analyte concentrations. [ABSTRACT FROM AUTHOR]

This work is devoted to study the peculiarities of charge transfer in SiO2(Ni)/Si nanosystems formed as a result of the electrochemical deposition of nickel into the pores of the ion-track silicon oxide template on silicon. Special attention is given to analysis of the results in the context of the band structure and physical properties of dielectric on semiconductor systems with metallic inclusions in the dielectric matrix. Experimental studies of the current-voltage characteristics of SiO2(Ni)/Si nanostructures demonstrated that value of potential barrier on the Si/metal interface in the pores of the silicon oxide template depended on temperature. On the basis of these results an interpretation of the charge transfer mechanisms in SiO2(Ni)/Si nanosystems at different temperature ranges was proposed. In the temperature region of ~300–200 K charge carrier motion occurs through the n-Si with an employment of metallic clusters in pores being in a contact with the semiconductor, by means of the overbarrier emission of electrons from higher energy levels of Si conduction band. In the lower temperatures (~200-100 K) a current flow takes place only through the semiconductor due to an increase of resistivity on energy barriers n-Si/metal, which leads to a practically complete exclusion of a participation of the metal in the charge transport process. In the low temperatures (~100–20 K), the variable range hopping conduction between pores on the SiO2/Si boundary, containing localized states, dominates. [ABSTRACT FROM AUTHOR]

The results of research on the behavior of Ni nanotubes under the influence of environments with different pH values are presented. The influence of exposure time on morphology and composition under specific test conditions was investigated, and a detailed study of the nanotube crystal structure parameters vs. time was carried out. Based on the obtained results, a mechanism for the degradation of Ni nanotubes under different conditions was suggested. [ABSTRACT FROM AUTHOR]

The modern development of nanotechnology requires the discovery of simple approaches that ensure the controlled formation of functional nanostructures with a predetermined morphology. One of the simplest approaches is the self-assembly of nanostructures. The widespread implementation of self-assembly is limited by the complexity of controlled processes in a large volume where, due to the temperature, ion concentration, and other thermodynamics factors, local changes in diffusion-limited processes may occur, leading to unexpected nanostructure growth. The easiest ways to control the diffusion-limited processes are spatial limitation and localized growth of nanostructures in a porous matrix. In this paper, we propose to apply the method of controlled self-assembly of gold nanostructures in a limited pore volume of a silicon oxide matrix with submicron pore sizes. A detailed study of achieved gold nanostructures' morphology, microstructure, and surface composition at different formation stages is carried out to understand the peculiarities of realized nanostructures. Based on the obtained results, a mechanism for the growth of gold nanostructures in a limited volume, which can be used for the controlled formation of nanostructures with a predetermined geometry and composition, has been proposed. The results observed in the present study can be useful for the design of plasmonic-active surfaces for surface-enhanced Raman spectroscopy-based detection of ultra-low concentration of different chemical or biological analytes, where the size of the localized gold nanostructures is comparable with the spot area of the focused laser beam. [ABSTRACT FROM AUTHOR]