Surface-enhanced Raman scattering (SERS) studies on silver nanorod substrates (original) (raw)
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Nanomaterials, 2013
Gold and silver nanoparticles (NPs) were prepared in water, acetonitrile and isopropanol by laser ablation methodologies. The average characteristic (longer) size of the NPs obtained ranged from 3 to 70 nm. 4-Aminobenzebethiol (4-ABT) was chosen as the surface enhanced Raman scattering (SERS) probe molecule to determine the optimum irradiation time and the pH of aqueous synthesis of the laser ablation-based synthesis of metallic NPs. The synthesized NPs were used to evaluate their capacity as substrates for developing more analytical applications based on SERS measurements. A highly energetic material, TNT, was used as the target compound in the SERS experiments. The Raman spectra were measured with a Raman microspectrometer. The results demonstrate that gold and silver NP substrates fabricated by the methods developed show promising results for SERS-based studies and could lead to the development of micro sensors.
Synthesis of Silver Nanoparticle Arrays for SERS Based Sensing
Lecture Notes in Electrical Engineering, 2011
Recently, noble-metal nanoparticles (NMNPs) were introduced in the sensing discipline, and become one of the most efficient ways to enhance sensors sensitivity. It is known, in fact, that NMNPs possess peculiar optical properties. When NMNPs are illuminated by a laser beam with proper wavelength, the so-called localized surface plasmons, a collective oscillation of conduction electrons on NMNP surface, are excited. The effect is relevant, for example, in Surface Enhanced Raman Spectroscopy, where a significant enhancement of a localized electromagnetic field near NMNPs surface allows to detect species usually undetectable with normal Raman spectroscopy. Here we present a method for the growth of silver NP arrays with controlled morphology by means of the pulsed laser ablation technique performed in presence of a Ar atmosphere. The nanoparticles size and morphology can be tuned, respectively, by the Ar pressure and the laser pulse number. The SERS activity of nanoparticle arrays is investigated by Raman scattering of adsorbed rhodamine 6G (R6G) at different concentrations.
Vibrational Spectroscopy, 2011
In surface-enhanced Raman scattering (SERS) technique the preparation of metal substrates containing minimum hindrance from impurities is an important issue. The synthesis of silver nanoparticles (Ag NPs) active as SERS substrates and having the above-mentioned advantage, were obtained by electron beam irradiation of Ag + aqueous solutions. Ag + ions were reduced by free radicals radiolytically generated in solution without the addition of chemical reductants or stabilizing agents.
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2003
A four step Ag foil laser ablation-Ag nanoparticle fragmentation procedure in ultrapure water was carried out both under argon and in air. Pulses of a high power Nd/YAG laser were used for laser ablation (1064 nm) and for the three step Ag hydrosol treatment in the absence of Ag foil in the sequence 1064 Á/532 Á/1064 nm. Transmission electron microscopy (TEM) and surface plasmon (SP) extinction spectra provide evidence of Ag nanoparticle fragmentation in the second and third step of the procedure carried out under argon. While polydispersity of Ag hydrosol increases in the second step, both the polydispersity and the mean size of the nanoparticles are reduced in the third step. Qualitative and quantitative surface-enhanced Raman scattering (SERS)/surface-enhanced resonance Raman scattering (SERRS) spectral probing of systems with Ag hydrosols and the selected adsorbates at 514.5 nm excitation shows that Ag hydrosols obtained in the second step of the preparation procedure carried out in air are the most suitable substrates for SERS/SERRS experiments performed at this excitation wavelength. #
Silver nanorods used to promote SERS as a quantitative analytical tool
Journal of Raman Spectroscopy, 2009
We have fabricated silver nanorod arrays by electrodepositing the nanorods evenly in the shallow pores of porous anodic aluminum oxide (AAO) templates. The diameter and length were 28 and 44 nm, respectively. The maxima of the transverse and longitudinal modes of the surface plasmon were near 417 and 511 nm, respectively. A good surface-enhanced Raman scattering (SERS) spectrum was observed by excitation with the 514.5-nm laser line. The SERS intensity increased almost linearly upon malachite green isothiocyanate adsorption on the tips of the silver nanorods as the concentration of the mother solutions increased. Our results show that silver nanorods fabricated on AAO templates could be used as an SERS substrate for quantitative analyses.
Journal of Colloid and Interface Science, 2008
Different Ag nanoparticles were prepared by four different methods (chemical reduction with trisodium citrate, chemical reduction with hydroxylamine hydrochloride, laser ablation and laser in situ photoreduction) to compare their applicability in surface-enhanced Raman scattering (SERS), their stability and other interfacial characteristics such as the pH, surface availability and the surface potential. This study was conducted by using the anthraquinone dye alizarin as a molecular probe since this molecule is able to be adsorbed onto the metal through three different forms, which relative proportions depend on the interfacial properties of the exposed metal surfaces.
SERS activity of silver and gold nanostructured thin films deposited by pulsed laser ablation
Applied Physics A, 2014
Nanostructured Au and Ag thin films were obtained by nanosecond pulsed laser ablation in presence of a controlled Ar atmosphere. Keeping constant other deposition parameters such as target-to-substrate distance, incidence angle, laser wavelength and laser fluence, the film morphology, revealed by SEM, ranges from isolated NPs to island structures and sensibly depends on gas pressure (10-100 Pa) and on the laser pulse number (500-3 9 10 4). The control of these two parameters allows tailoring the morphology and correspondingly the optical properties of the films. The position and width of the surface plasmon resonance peak, in fact, can be varied with continuity. The films showed remarkable surface-enhanced Raman activity (SERS) that depends on the adopted deposition conditions. Raman maps were acquired on micrometer-sized areas of both silver and gold substrates selected among those with the strongest SERS activity. Organic dyes of interest in cultural heritage studies (alizarin, purpurin) have been also considered for bench marking the substrates produced in this work. Also the ability to detect the presence of biomolecules was tested using lysozyme in a label free configuration.
Ag and Au nanoparticles for SERS substrates produced by pulsed laser ablation
Crystal Research and Technology, 2011
A method for the growth of films consisting of Nanoparticles (NP) of Ag and Au is presented. Nanostructured films were obtained by means of nanosecond pulsed laser ablation of a metallic target in presence of a controlled Ar atmosphere. The morphology of these films from island structures to isolated nanoparticles, measured by SEM, depends on the varying gas pressure (10-100 Pa) and on the number of laser pulses (500-30000), keeping other deposition parameters such as the target to substrate distance, incidence angle, laser wavelength, laser fluence constant. Fast imaging of the plasma, performed using a intensified and gateable CCD camera at different time delays with respect to the arrival of the laser pulse, allows revelation of the propagation regime of the ablation plume and inference of plasma initial velocity. This data along with the measured average ablated mass per pulse were taken as inputs to a model to estimate the average size of NPs grown in the expanding plume. The theoretical NP sizes were compared with sizes measured from TEM images. These images indicate narrow gradients of NP sizes. Hence strict control of growth parameters aids fine tuning of NP size that is essential for many applications, including Surface Enhanced Raman Spectroscopy (SERS) active substrates. UV-Visible Spectroscopy helped in determination of appropriate laser wavelength for resonant excitation of the localized surface plasmon. SERS Spectra obtained with increasingly lower concentrations of reference dye Rhodamin 6G (Rh6G) and medical drug Apomorphine, are discussed as a perspective of application to biomedical sensors.
Ag nanoparticles obtained by pulsed laser ablation in water: surface properties and SERS activity
Journal of Raman Spectroscopy, 2015
We studied the surface properties and reactivity of silver nanoparticles obtained by picosecond or nanosecond pulsed laser ablation in water and with 1064-nm wavelength. Ultraviolet-visible spectroscopy results and subsequent modelling by Mie theory indicated the presence of an oxide layer on the nanoparticle surface, which favours the colloidal stability, but reduces the interaction with the environment. The oxide layer is also responsible for the reduced surface enhanced Raman spectroscopy (SERS) activity of these colloids with respect to those obtained by chemical reduction. However, SERS activation can be efficiently obtained by addition of chloride ions to the colloids, leading to SERS enhancement factors that are comparable with those of the chemically prepared counterparts.