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For the first time, we report experimentally and theoretically that nitroaromatic compounds, 2,4-dinitrobenzenethiol and 4-chloro-2-nitrobenzenethiol, on silver sols can be selectively reduced to 2-amino-4-nitrobenzenethiol and 2-amino-4-chlorobenzenethiol simply by irradiating with a visible light in ambient conditions, and the selective photoreduction is a very facile process. The results of quantum chemical calculations are in good agreement with our experimental data. Copyright (c) 2012 John Wiley & Sons, Ltd.

We describe a novel surface-enhanced Raman scattering (SERS) tag that is based on Au/Ag core-shell nanostructures embedded with p-aminothiophenol. The Au/Ag core-shell sandwich nanostructures demonstrate bright and dark stripe structure and possess very strong SERS activity. Under optimum conditions, the maximum SERS signal was obtained with a 10 nm thick Ag nanoshell, and the enhancement factor is 3.4 × 104 at 1077 cm−1. After conjugation to the antibody of muramidase releasing protein (MRP), the Au/Ag core-shell nanostructures were successfully applied to an SERS-based detection scheme for MRP based on a sandwich type of immunoassay.

In this study, we attempt to experimentally address the question of whether p,p′-dimercaptoazobisbenzene (DMAB) can be produced from p-aminothiophenol (PATP) by surface photochemistry reaction in the junctions of a Ag nanoparticle−molecule−Ag (or Au) film. First, utilizing surface-enhanced Raman scattering (SERS) spectra, we provide experimental and theoretical evidence that DMAB can be produced from PATP by surface photochemistry reaction in the junctions of a Ag nanoparticle−molecule−Ag film. Second, we investigate the SERS spectra utilizing both experimental and theoretical approaches, ultimately revealing that DMAB cannot be produced from PATP in the junctions of a Ag nanoparticle−molecule−Au film. The electromagnetic enhancements are estimated with three-dimensional finite-difference time domain methods, which are about 9 × 105 times in the junctions of Ag nanoparticle−PATP−Ag/Au films.

Stable gold nanochains with branched features were fabricated at room temperature with the assistance of polyvinylpyrrolidone (PVP). An attachment and fusion process was believed to responsible for the formation of the chain-like structure. During the process, PVP acted both as a structure-directing agent and as a stabilizer to inhibit continuous size increase. UV−vis−NIR study revealed that the unique structure shifted the longitudinal surface plasma resonant band (LSPR) to as far as 1457 nm, which may endow the product with new applications. The surface-enhanced Raman scattering activity was investigated with p-aminothiophenol as probe molecule. The enhancement factor (EF) of the products deposited as film on the Si substrate was estimated to be (1.03 ± 0.74) × l06 for the a1-type band, while it was (1.32 ± 0.15) × l07 for b2-type band. The enhancement of a1 modes was attributed to the electromagnetic mechanism, whereas the additional EF for the b2 mode is presumed to contribute from the chemical effect.

Recently, metal−molecule−metal junctions have been actively researched due to their potential applications in molecular electronics, and probing the structure of the molecules in the junctions is c...

A sensitive electrochemical molecularly imprinted sensor was developed for the detection of estradiol, by electropolymerization of p-aminothiophenol functionalized gold nanoparticles in the presence of estradiol as template molecule. The extraction of the template leads to the formation of cavities that are able to recognize and bind estradiol with high affinity. The performance of the developed sensor for the detection of estradiol was investigated by linear sweep voltammetry using a hexacyanoferrate/hexacyanoferrite solution as redox probe. The molecularly imprinted sensor exhibits a broad linear range, between 3.6 fM and 3.6 nM and a limit of quantification of 1.09 fM. Compared to the non-imprinted sensor, the imprinted sensor exhibits high affinity for the binding of estradiol. Moreover, selectivity studies, performed towards binding of testosterone, a hormone with similar chemical structure, proved high sensor selectivity. Furthermore, the molecularly imprinted sensor was applied for the analysis of spiked river samples with good recoveries. Keywords: Molecularly imprinted polymer, p-Aminothiophenol, Gold nanoparticles, Estradiol

We investigated the effect of the temperature of the plasmonic substrate on the surface enhanced Raman scattering of p-aminothiophenol adsorbed onto a particulate film of gold nanoparticles-decorated polystyrene nanospheres. The results demonstrated that temperature induces important modifications in the overall spectral signature of the charge transfer bands, which are consistent with the generation of a new molecular species. Moreover, the analysis of the shape of the vibrational band at 1078 cm(-1) assigned to the >C-S mode, which is enhanced by electromagnetic mechanism, reveals the co-existence of two distinct bands at 1071 and 1078 cm(-1), assignable to p,p'-dimercaptoazobenzene and p-aminothiophenol, respectively.

The inversion observed at 0·1 T for the magnetic field effects (MFEs) on the photoreduction of xanthone with p-aminothiophenol was investigated in the absence and the presence of a paramagnetic Gd3+ ion with the aid of a laser flash photolysis technique. The MFEs owing to the Δg and relaxation mechanisms were experimentally separated by the addition of Gd3+. Thus, we have proved for the present reaction that the MFEs owing to the hyperfine coupling mechanism and relaxation mechanism appear in a low field region (below 0·1 T) and that the MFEs owing to the Δg mechanism gradually appear in a high field region (above 0·1 T).

Combining experiment and theory, evidence from surface-enhanced Raman scattering (SERS) were obtained for p,p′-dimercaptoazobenzene (DMAB) produced from p-aminothiophenol (PATP) by selective catalytic coupling reaction on silver nanoparticles. The time-dependent SERS spectra of PATP are consistent with the calculated SERS spectra of DMAB, which is the direct evidence for the production of DMAB from PATP by selective catalytic coupling reaction on silver nanoparticles. The so-called “b2 modes” of PATP is the −N═N− related vibrational modes of DMAB. The silver nanoparticles could be assembled together to form different size of aggregates with different concentration of PATP solution. When the concentration of Ag nanoparticle (the radius 40 nm) in colloid is 35 pM, the time-dependent SERS of DMAB reveals that the better experimental conditions for observing SERS signals of DMAB are (1) concentration of PATP is around 5 × 10−6 M in which condition the aggregates consist with about 3−5 silver nanoparticles, wh...

For the first time, the experimental and theoretical evidence for the conversion of 4-nitrobenzenethiol (4-NBT) to p,p'-dimercaptoazobenzene (DMAB) in Ag and Cu sols by surface photochemistry reaction is obtained with surface-enhanced Raman scattering (SERS) spectroscopy. The SERS spectrum of 4-NBT in Cu sol is identical to that of DMAB produced from 4-aminothiophenol in Ag sol as reported in recent literature, thereby providing direct spectral evidence. Copyright (C) 2011 John Wiley & Sons, Ltd.

p-aminothiophenol (PATP) is an important molecule for surface-enhanced Raman spectroscopy (SERS). It can strongly interact with metallic SERS substrates and produce very strong SERS signals. It is a molecule that has often been used for mechanistic studies of the SERS mechanism as the photon-driven charge transfer (CT) mechanism is believed to be present for this molecule. Recently, a hot debate over the SERS behavior of PATP was triggered by our finding that PATP can be oxidatively transformed into 4,4'-dimercaptoazobenzene (DMAB), which gives a SERS spectra of so-called "b2 modes". In this perspective, we will give a general overview of the SERS mechanism and the current status of SERS studies on PATP. We will then demonstrate with our experimental and theoretical evidence that it is DMAB which contributes to the characteristic SERS behavior in the SERS spectra of PATP and analyze some important experimental phenomena in the framework of the surface reaction instead of the contribution "b2 modes". We will then point out the existing challenges of the present system. A clear understanding of the reaction mechanism for nitrobenzene or aromatic benzene will be important to not only understand the SERS mechanism but to also provide an economic way of producing azo dyes with a very high selectivity and conversion rate.