Modification of a SERS-active Ag surface to promote adsorption of charged analytes: effect of Cu ions.

This work studies the impact of the electrostatic interaction between analyte molecules and silver nanoparticles (Ag NPs) on the intensity of surface-enhanced Raman scattering (SERS). For this, we fabricated nanostructured plasmonic films by immobilization of Ag NPs on glass plates and functionalized them by a set of differently charged hydrophilic thiols (sodium 2-mercaptoethyl sulfonate, mercaptopropionic acid, 2-mercaptoethanol, 2-(dimethylamino)ethanethiol hydrochloride, and thiocholine) to vary the surface charge of the SERS substrate. We used two oppositely charged porphyrins, cationic copper(II) tetrakis(4--methylpyridyl) porphine (CuTMpyP4) and anionic copper(II) 5,10,15,20-tetrakis(4-sulfonatophenyl)porphine (CuTSPP4), with equal charge value and similar structure as model analytes to probe the SERS signal.

Progress in the Development of SERS-Active Substrates Based on Metal-Coated Porous Silicon.

The present work gives an overview of the developments in surface-enhanced Raman scattering (SERS) with metal-coated porous silicon used as an active substrate. We focused this review on the research referenced to SERS-active materials based on porous silicon, beginning from the patent application in 2002 and enclosing the studies of this year. Porous silicon and metal deposition technologies are discussed.

Formation Regularities of Plasmonic Silver Nanostructures on Porous Silicon for Effective Surface-Enhanced Raman Scattering.

Plasmonic nanostructures demonstrating an activity in the surface-enhanced Raman scattering (SERS) spectroscopy have been fabricated by an immersion deposition of silver nanoparticles from silver salt solution on mesoporous silicon (meso-PS). The SERS signal intensity has been found to follow the periodical repacking of the silver nanoparticles, which grow according to the Volmer-Weber mechanism. The ratio of silver salt concentration and immersion time substantially manages the SERS intensity.

Determination of antimony by surface-enhanced Raman spectroscopy.

A highly sensitive method for the detection and quantitative evaluation of antimony(III) using the surface-enhanced Raman scattering (SERS) technique is demonstrated. The method is based on the analysis of SERS spectra intensity of antimony bound to phenylfluorone (Sb-PhF). Phenylfluorone is widely used as an organic reagent for the spectrophotometric determination of some heavy metals.

Nanostructures formed by displacement of porous silicon with copper: from nanoparticles to porous membranes.

The application of porous silicon as a template for the fabrication of nanosized copper objects is reported. Three different types of nanostructures were formed by displacement deposition of copper on porous silicon from hydrofluoric acid-based solutions of copper sulphate: (1) copper nanoparticles, (2) quasi-continuous copper films, and (3) free porous copper membranes. Managing the parameters of porous silicon (pore sizes, porosity), deposition time, and wettability of the copper sulphate solution has allowed to achieve such variety of the copper structures.

Fluorescence properties of the dicationic porphyrin 5,15-DiMPyP orderly aggregated along DNA surface.

5,15-bis(4-N-methylpyridyl)-10,20-diphenylporphyrin (5,15-DiMPyP, also known as t-H2Pagg) is capable of forming long-range ordered DNA-templated aggregates in solution. The present work reports the study of fluorescent properties of 5,15-DiMPyP, both monomeric and aggregated in presence of DNA, performed by means of steady-state and time-resolved fluorescence spectroscopy. The S1 state of free monomeric 5,15-DiMPyP is affected by a low-lying intramolecular charge transfer state which is destabilized upon porphyrin monomer binding to DNA.