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1.
J Phys Chem A ; 123(42): 9199-9208, 2019 Oct 24.
Artigo em Inglês | MEDLINE | ID: mdl-31549839

RESUMO

Sulfadiazine, as a class of antibiotics, has been widely used in the world for decades; however, its surface-enhanced Raman spectra (SERS) on gold colloids are obviously different from ordinary Raman spectra in the solid powder and liquid solution. To explore the reasons for such significant differences, we used density functional theory calculations and normal-mode analysis to investigate the effects of the configuration, conformation, protonation, hydrogen-bonding interaction, and adsorption configurations of sulfadiazine on gold clusters to check these different effects on the vibrational assignments. Our calculated results can be summarized as two points. First, the Raman spectra strongly depend on the configuration, conformation, protonation, and hydrogen bonding of sulfadiazine. Second, the wagging vibration displays a significant vibrational frequency shift and a very strong SERS peak responsible for the observed SERS signal when sulfadiazine is adsorbed on gold clusters through the terminal amino group. This is different from another adsorption configuration through two oxygen atoms of the -SO2NH- group on gold clusters. Finally, we further investigate the potential energy surfaces along the wagging vibration and the binding interaction of -NH2 adsorbed on different sites of gold surfaces.

2.
Chem Commun (Camb) ; 54(1): 10-25, 2017 Dec 19.
Artigo em Inglês | MEDLINE | ID: mdl-29139483

RESUMO

In this feature article, we discuss in detail developmental bottleneck issues in Raman spectroscopy in its early stages and surface-enhanced Raman spectroscopy (SERS) in the past four decades. We divide SERS research into two different directions with different targets. Fundamental research is extending the limits of SERS to single-molecule, sub-nanometer resolution and femtosecond processes. In contrast, practical research is expanding the range of applications with the aim of providing versatile analytical tools for surface, materials, life, environmental, forensic and food sciences and also commercial instruments for use in daily life. In the second direction there have continually been many complex bottlenecks to be overcome. We attempt to enumerate the key issues in detail and also describe the achievements made to overcome the bottlenecks. In the last, but not least important part, we discuss the remaining bottlenecks and possible strategies for overcoming them to enable SERS to be an even more powerful and versatile technique.

3.
Sci Rep ; 6: 31981, 2016 Sep 23.
Artigo em Inglês | MEDLINE | ID: mdl-27659311

RESUMO

Inter- and intra- molecular hydrogen bonding plays important role in determining molecular structure, physical and chemical properties, which may be easily ignored for molecules with a non-typical hydrogen bonding structure. We demonstrated in this paper that the hydrogen bonding is responsible for the different Raman spectra in solid and solution states of p-Nitrothiophenol (PNTP). The consistence of the theoretical calculation and experiment reveals that the intermolecular hydrogen bonding yields an octatomic ring structure (8) of PNTP in the solid state, confirmed by the characteristic S-H---O stretching vibration mode at 2550 cm-1; when it comes to the solution state, the breakage of hydrogen bond of S-H---O induced the S-H stretching vibration at 2590 cm-1. Our findings may provide a simple and fast method for identifying the intermolecular hydrogen bonding.

4.
Phys Chem Chem Phys ; 18(27): 18112-8, 2016 Jul 21.
Artigo em Inglês | MEDLINE | ID: mdl-27327514

RESUMO

Organolead halide perovskites exhibit superior photoelectric properties, which have given rise to the perovskite-based solar cells whose power conversion efficiency has rapidly reached above 20% in the past few years. However, perovskite-based solar cells have also encountered problems such as current-voltage hysteresis and degradation under practical working conditions. Yet investigations into the intrinsic chemical nature of the perovskite material and its role on the performance of the solar cells are relatively rare. In this work, Raman spectroscopy is employed together with CASTEP calculations to investigate the organic-inorganic interactions in CH3NH3PbI3 and CH3NH3PbBr3-xClx perovskite single crystals with comparison to those having ammonic acid as the cations. For Raman measurements of CH3NH3PbI3, a low energy line of 1030 nm is used to avoid excitation of strong photoluminescence of CH3NH3PbI3. Raman spectra covering a wide range of wavenumbers are obtained, and the restricted rotation modes of CH3-NH3(+) embedded in CH3NH3PbBr3 (325 cm(-1)) are overwhelmingly stronger over the other vibrational bands of the cations. However, the band intensity diminishes dramatically in CH3NH3PbBr3-xClx and most of the bands shift towards high frequency, indicating the interaction with the halides. The details of such an interaction are further revealed by inspecting the band shift of the restricted rotation mode as well as the C-N, NH3(+) and CH3 stretching of the CH3NH3(+) as a function of Cl composition and length of the cationic ammonic acids. The results show that the CH3NH3(+) interacts with the PbX3(-) octahedral framework via the NH3(+) end through N(+)-HX hydrogen bonding whose strength can be tuned by the composition of halides but is insensitive to the size of the organic cations. Moreover, an increase of the Cl content strengthens the hydrogen bonding and thus blueshifts the C-N stretching bands. This is due to the fact that Cl is more electronegative than Br and an increase of the Cl content decreases the lattice constant of the perovskite. The findings of the present work are valuable in understanding the role of cations and halides in the performance of MAPbX3-based perovskite solar cells.

5.
Guang Pu Xue Yu Guang Pu Fen Xi ; 35(4): 1107-10, 2015 Apr.
Artigo em Japonês | MEDLINE | ID: mdl-26197611

RESUMO

The present paper developed a portable and fast sample pretreatment apparatus. It has many virtues like being portable, low power consumption and convenient operation, short extraction time and sound repeatability. Therefore, it can meet the requirements of on-site rapid detection pretreatment. The apparatus consists of four functional modules: ultrasonic extraction unit, heating unit, exhaust gas evaporation and absorption unit and control system. In addition, LED control panel and alarm device were designed. The whole treatment process needs three steps: ultrasonic extraction, liquid-liquid extraction and solvent evaporation by heating and pumping. For test of this apparatus performance, three real samples (pepper powder, pepper oil, bean sauce) containing banned additive Rhodamine B were taken as experiment objects. Compared with conventional laboratory pretreatment method, the PERS spectra achieved by two methods were little changed, but the experiment time was halved. In addition, the test results showed relative standard deviation less than ±5%.


Assuntos
Métodos Analíticos de Preparação de Amostras/instrumentação , Inocuidade dos Alimentos/métodos , Análise Espectral Raman , Extração Líquido-Líquido , Solventes , Verduras
6.
Artigo em Inglês | MEDLINE | ID: mdl-25710112

RESUMO

In order to explore the key role of surface plasmon resonance (SPR) and active (3)O2 for the chemical transformation to 4,4-dimercaptoazobenzene (DMAB) from p-aminothiophenol (PATP) adsorbed on Ag or Au NPs, we systematically investigated the laser wavelength and temperature dependent surface-enhanced Raman spectra of PATP capped Ag and Au NPs. DMAB can be easily observed at the 514.5nm laser for Ag NPs but at the 632.8nm laser for Au NPs, indicating that a suitable energy level is necessary for the formation of DMAB. The tendency is consistent with the wavelength dependent SPR properties of Ag or Au NPs accordingly. With the energy provided by annealing, the transformation of PATP to DMAB is much easier on Ag NPs at a lower temperature, and more DMAB can be observed at the same temperature, compared to the case of Au NPs under the same condition. It is mainly due to the active (3)O2 on Ag surfaces could be more easily formed than that on Au surfaces.


Assuntos
Compostos de Anilina/química , Ouro , Nanopartículas Metálicas/química , Prata , Compostos de Sulfidrila/química , Adsorção , Lasers , Oxigênio/química , Análise Espectral Raman , Ressonância de Plasmônio de Superfície , Temperatura Ambiente
7.
Artigo em Inglês | MEDLINE | ID: mdl-25467654

RESUMO

The laser induced transformation of p-aminothiophenol (PATP) to p,p'-dimercaptoazobenzene (DMAB) has attracted intensive interest recently, in which localized surface plasmon resonance (LSPR) assisted photocatalysis has been demonstrated to play an important role. In this paper, we systematically investigate the factors that influence the reaction for further understanding the mechanism using surface-enhanced Raman spectroscopy. The laser-induced formation of DMAB was found to depend on the surface coverage of PATP, the aggregation state of NPs, and the laser power. The disappearance of DMAB Raman signal at very low concentration of Ag NPs reveals that DMAB may only be formed between the neighboring NPs that can provide a suitable distance for the interaction between adsorbed PATP molecules.


Assuntos
Compostos de Anilina/química , Lasers , Nanopartículas Metálicas/química , Prata/química , Análise Espectral Raman/métodos , Compostos de Sulfidrila/química , Adsorção , Propriedades de Superfície
8.
Chem Commun (Camb) ; 50(94): 14740-3, 2014 Dec 07.
Artigo em Inglês | MEDLINE | ID: mdl-25325083

RESUMO

We employ, for the first time, a shell-isolated nanoparticle-enhancement strategy to extend Raman spectroscopy studies to single crystal electrode surfaces in ionic liquids, and combine density functional theory (DFT) calculations to elucidate the structural details of the imidazolium-based ionic liquid-Au single crystal electrode interfaces.

9.
Guang Pu Xue Yu Guang Pu Fen Xi ; 34(5): 1284-8, 2014 May.
Artigo em Chinês | MEDLINE | ID: mdl-25095423

RESUMO

Surface enhanced Raman spectroscopy (SERS) is a useful chemical analysis technique for its high sensitivity, which was used for Malachite Green qualitative analysis in real cases in the present article. Automatic recognition algorithms were put forward, which is a combination of three modules, including a robust Fourier transform for background rejection, a principal component analysis based character extraction method and artificial neural networks for classifying. Low-frequency background was rejected by iterative Fourier transform in order to eliminate the effect of variable background. The best principal component combination was obtained according to the Euclidean distances between-class and within-class in the sample space. And a three-layer back-propagating neural network was constructed for classifying. As it was shown, it would both minimize the network and reduce the classifying mistakes from variable baseline and Raman characters of other substances in seawater with best principal component combination. Malachite Green real-time detection in aquaculture used seawater was realized with a lower density limit of 0. 1 microg L-1. Moreover, the method proposed in this article could be extended for other sol analysis based on SERS technique.

10.
Artigo em Inglês | MEDLINE | ID: mdl-23764489

RESUMO

Interfacial structure determines the activity and selectivity of a sensor and plays important roles in interfacial electrochemistry, electroanalysis, biosensing, etc. In situ electrochemical Raman spectroscopy appears to be a powerful tool to probe the electrochemical interface and surface process by providing the molecular fingerprint information. Herein, the electrochemical behaviors of N-methyl-N'-carboxydecyl-4,4'-bipyridinium (derivatives of methyl viologens, MV(2+)) with different alkyl chain lengths (n=2 and 10) on roughened Au electrodes were systematically investigated by the electrochemical surface-enhanced Raman spectroscopy (SERS). Three systems with different interfacial structures were constructed. One is to anchor the MV(2+) molecules via esterification with the 2-mercaptoethanol molecule pre-assembled on the Au surface. The second system is similar to the first one but without esterification. The third system is the direct adsorption of MV(2+) molecules on the bare roughened Au surfaces. The three systems gave different spectral response upon the change of the electrode potential. A drastically increased relative Raman intensity of 19a/8a modes of the MV(2+) molecules was observed at negative potentials. The phenomenon is attributed to the formation of the reduced form of MV(2+) molecules, which produces resonant Raman effect to enhanced the signal of 19a mode. The third system showed the highest electrochemical reduction activity towards the reduction of MV(2+) molecules, followed by the first and second systems. The result indicates that the interfacial structure can sensitively influence electrochemical activity of the electrode.


Assuntos
Análise Espectral Raman/métodos , Viologênios/química , Eletrodos , Ouro/química , Metilação , Oxirredução , Propriedades de Superfície
11.
Phys Chem Chem Phys ; 14(24): 8485-97, 2012 Jun 28.
Artigo em Inglês | MEDLINE | ID: mdl-22614115

RESUMO

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.


Assuntos
Compostos de Anilina/química , Análise Espectral Raman/métodos , Compostos de Sulfidrila/química , Transporte de Elétrons , Vibração
12.
J Am Chem Soc ; 132(27): 9244-6, 2010 Jul 14.
Artigo em Inglês | MEDLINE | ID: mdl-20527877

RESUMO

Surface-enhanced Raman spectroscopy (SERS) has long been considered as a noninvasive technique that can obtain the fingerprint vibrational information of surface species. We demonstrated in this paper that a laser with a power level considered to be low in the traditional SERS measurement can already lead to a significant surface reaction. para-Aminothiophenol, an important probe molecule in SERS, was found to be oxidized to form 4,4'-dimercaptoazobenzene (DMAB) on a roughened silver surface during the SERS measurement. The assumption was confirmed experimentally by surface mass spectroscopy and SERS as well as electrochemistry of the synthesized DMAB, which agrees well with theoretical calculations. A defocusing method was used to avoid the laser induced surface reaction and perform reliable SERS characterization and identification, which can effectively avoid erroneous interpretation of the distorted experimental result.

13.
Analyst ; 135(5): 1084-9, 2010 May.
Artigo em Inglês | MEDLINE | ID: mdl-20419260

RESUMO

A subattomolar HIV-1 DNA detection assay based on multilayer metal-molecule-metal nanojunctions (NJs) has been developed using surface-enhanced Raman spectroscopy (SERS). There is a two-step mechanism involved. First, label free target DNA facilitated the precipitation of Detection Unit I on the substrate through forming a sandwiched structure based on the capture probe, resulting in the first level amplification of target. Following that, the binding site on Detection probe I was further recognized by Detection Unit II. These two complementary probes acted as bricks to build up the multi-metal-molecule-metal NJs between Au nanoparticles (NPs) that not only created SERS "hot spots" by the conjugated Au NPs, but also obviously decreased the distance between Au NPs and Raman labels. Therefore, the Raman signal of the tag molecules on these detection probes was significantly enhanced due to the distance dependent electromagnetic enhancement (EM) of SERS. With regards to a HIV-1 DNA sequence, the platform could detect a concentration as low as 10(-19) M (approximately 10(-23) mol) with the ability of single base mismatch discrimination.


Assuntos
DNA Viral/análise , HIV-1/genética , Análise Espectral Raman/métodos , Eletrodos , Ouro/química , Magnetismo , Nanopartículas Metálicas/química
14.
Anal Chem ; 81(1): 87-93, 2009 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-19117446

RESUMO

We have developed an electrostatic interaction based biosensor for thrombin detection using surface-enhanced Raman spectroscopy (SERS). This method utilized the electrostatic interaction between capture (thrombin aptamer) and probe (crystal violet, CV) molecules. The specific interaction between thrombin and aptamer could weaken the electrostatic barrier effect from the negative charged aptamer SAMs to the diffusion process of the positively charged CV from the bulk solution to the Au nanoparticle surface. Therefore, the more the bound thrombin, the more the CV molecules near the Au nanoparticle surface and the stronger the observed Raman signal of CV, provided the Raman detections were set at the same time point for each case. This procedure presented a highly specific selectivity and a linear detection of thrombin in the range from 0.1 nM to 10 nM with a detection limit of about 20 pM and realized the thrombin detection in human blood serum solution directly. The electrostatic interaction based technique provides an easy and fast-responding optical platform for a "signal-on" detection of proteins, which might be applicable for the real time assay of proteins.


Assuntos
Aptâmeros de Peptídeos/química , Violeta Genciana/química , Análise Espectral Raman/métodos , Trombina/análise , Técnicas Biossensoriais/métodos , Ouro/química , Humanos , Imunoglobulina A/análise , Nanopartículas Metálicas/química , Soroalbumina Bovina/análise , Eletricidade Estática
15.
Anal Bioanal Chem ; 388(1): 29-45, 2007 May.
Artigo em Inglês | MEDLINE | ID: mdl-17318524

RESUMO

Surface-enhanced Raman spectroscopy (SERS) has developed into one of the most important tools in analytical and surface sciences since its discovery in the mid-1970s. Recent work on the SERS of transition metals concluded that transition metals, other than Cu, Ag, and Au, can also generate surface enhancement as high as 4 orders of magnitude. The present article gives an overview of recent progresses in the field of Raman spectroscopy on transition metals, including experimental, theory, and applications. Experimental considerations of how to optimize the experimental conditions and calculate the surface enhancement factor are discussed first, followed by a very brief introduction of preparation of SERS-active transition metal substrates, including massive transition metal surfaces, aluminum-supported transition metal electrodes, and pure transition metal nanoparticle assembled electrodes. The advantages of using SERS in investigating surface bonding and reaction are illustrated for the adsorption and reaction of benzene on Pt and Rh electrodes. The electromagnetic enhancement, mainly lightning-rod effect, plays an essential role in the SERS of transition metals, and that the charge-transfer effect is also operative in some specific metal-molecule systems. An outlook for the field of Raman spectroscopy of transition metals is given in the last section, including the preparation of well-ordered or well-defined nanostructures, and core-shell nanoparticles for investigating species with extremely weak SERS signals, as well as some new emerging techniques, including tip-enhanced Raman spectroscopy and an in situ measuring technique.


Assuntos
Eletrodos , Nanopartículas Metálicas/química , Ressonância de Plasmônio de Superfície/métodos , Elementos de Transição/química , Adsorção , Benzeno/análise , Eletroquímica , Propriedades de Superfície
16.
Langmuir ; 22(25): 10372-9, 2006 Dec 05.
Artigo em Inglês | MEDLINE | ID: mdl-17129005

RESUMO

The aim of this work is to further improve the molecular generality and substrate generality of SERS (i.e., to fully optimize the SERS activity of transition-metal electrodes). We utilized a strategy of borrowing high SERS activity from the Au core based on Au-core Pt-shell (Au@Pt) nanoparticle film electrodes, which can be simply and routinely prepared. The shell thickness from about one to five monolayers of Pt atoms can be well controlled by adjusting the ratio of the number of Au seeds to Pt(IV) ions in the solution. The SERS experimental results of carbon monoxide adsorption indicate that the enhancement factor for the Au@Pt nanoparticle film electrodes is more than 2 orders of magnitude larger than that of electrochemically roughened Pt electrodes. The practical virtues of the present film electrodes for obtaining rich and high-quality vibrational information for diverse adsorbates on transition metals are pointed out and briefly illustrated with systems of CO, hydrogen, and benzene adsorbed on Pt. We believe that the electrochemical applications of SERS will be broadened with this strategy, in particular, for extracting detailed vibrational information for adsorbates at transition-metal electrode interfaces.


Assuntos
Ouro/química , Membranas Artificiais , Nanopartículas/química , Platina/química , Adsorção , Benzeno/química , Eletroquímica , Eletrodos , Hidrogênio/química , Tamanho da Partícula , Sensibilidade e Especificidade , Análise Espectral Raman/métodos , Propriedades de Superfície , Vibração
17.
J Phys Chem B ; 110(35): 17498-506, 2006 Sep 07.
Artigo em Inglês | MEDLINE | ID: mdl-16942090

RESUMO

Investigation of benzene adsorption on different metal surfaces closer to a practical system appears to be a very important intermediate stage to utilize the conclusion obtained on single-crystal surfaces. In this paper, we studied the electrochemical adsorption behaviors of benzene on roughened Pt group electrodes using surface enhanced Raman spectroscopy (SERS). The effects of potential, surface roughness, and benzene concentration were investigated. Significant difference in surface Raman spectra of benzene on Ru, Rh, Pd, and Pt surfaces were found. On Pt surfaces, the parallel-chemisorbed benzene, the vertical dissociated chemisorbed benzene, and the physisorbed benzene were observed, evidenced by the ring vibration mode appearing at 872, 1012, and 991 cm(-1), respectively. On Pd, only parallel-chemisorbed benzene and physisorbed benzene were found. On Rh and Ru, the SERS signals were mainly from the parallel-chemisorbed benzene, with an extremely weak signal from the physisorbed benzene. The potential dependent study reveals that the parallel-chemisorbed species interacts strongest with the substrate, while the physisorbed species can be easily removed at positive potentials. The models for the adsorbed benzene were given to account for the different types of benzene on these Pt group metals. The difference in the atomization heat of the four metals was used to interpret the different interaction strength of benzene with Pt group metals.

18.
Guang Pu Xue Yu Guang Pu Fen Xi ; 26(6): 1067-70, 2006 Jun.
Artigo em Chinês | MEDLINE | ID: mdl-16961232

RESUMO

Surface-enhanced Raman scattering (SERS) spectrum of imidazole adsorbed on a nickel electrode in 0.1 mol x L(-1) KCl solution was investigated as a function of applied potential. The corrosion inhibition effects of imidazole on the nickel electrodes in 0.1 mol x L(-1) KCl solution were investigated by using both cyclic voltagram and Tafel plot. The results indicated that imidazole was adsorbed on Ni electrode with tilted or perpendicular orientation due to the maximum enhancement of the in-plane vibration modes. The appearance of the peak at 1,173 cm(-1) (i. e. NH deformation) further supported the adsorption of neutral imidazole molecules in a neutral solution. A low-wave number band appeared at 214 cm(-1) was assigned to the Ni-N stretch, considering the interaction between imidazole molecules and the metal surface via N-atom. The molecules had maximum adsorption at -1.3 V. At higher negative potentials, the adsorption decreased gradually, which resulted in weaker inhibition effect.

19.
Guang Pu Xue Yu Guang Pu Fen Xi ; 25(9): 1418-21, 2005 Sep.
Artigo em Chinês | MEDLINE | ID: mdl-16379279

RESUMO

Electrochemical oxidation-reduction method was employed to roughen Zn electrode for obtaining SERS, and potential dependent surface enhanced Raman spectra (SERS) of roughened Zn electrode in KOH solution of different concentration wereobserved. The spectra of Zn electrode in various solutions had obvious differences which indicated the concentration of OH- had a great effect on the dissolution and passivation of zinc. Based on our experimental results, the authors attempt to analyse the behavior of zinc in alkaline and give the mechanism of its passivation.


Assuntos
Hidróxidos/química , Compostos de Potássio/química , Análise Espectral Raman/métodos , Zinco/química , Eletrodos , Concentração de Íons de Hidrogênio , Modelos Químicos , Soluções , Propriedades de Superfície
20.
J Am Chem Soc ; 125(32): 9598-9, 2003 Aug 13.
Artigo em Inglês | MEDLINE | ID: mdl-12904020

RESUMO

We report the first observation of surface-enhanced Raman scattering (SERS) excited with ultraviolet (UV) light from transition metal electrodes. Adsorbed pyridine and SCN- on rough rhodium (Rh) and ruthenium (Ru) electrodes, respectively, have been studied using 325 nm laser excitation. In contrast, the best enhancers in the visible and near infrared, silver and gold, do not produce UV-SERS. The experimental data of UV-SERS are in agreement with our preliminary theoretical calculation based on the electromagnetic enhancement mechanism. The enhancement factor is about 2 orders of magnitude for the Rh and Ru electrodes when they are excited at 325 nm.


Assuntos
Ródio/química , Rutênio/química , Análise Espectral Raman/métodos , Eletrodos , Piridinas/química , Espalhamento de Radiação , Tiocianatos/química , Raios Ultravioleta
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