Co-reporter:Run-Wen Yan
The Journal of Physical Chemistry C 2016 Volume 120(Issue 22) pp:11820-11830
Publication Date(Web):May 17, 2016
DOI:10.1021/acs.jpcc.6b03116
Co-reporter:Liu-Bin Zhao
The Journal of Physical Chemistry C 2016 Volume 120(Issue 3) pp:1570-1579
Publication Date(Web):January 7, 2016
DOI:10.1021/acs.jpcc.5b10207
Recent studies demonstrated that aromatic amines and aromatic nitro compounds could be converted to the corresponding azo species during surface-enhanced Raman experiments. It is very interesting to study the reaction mechanism for molecules that contain both an amino group and a nitro group, nitroaniline isomers. DFT calculations are applied to study the surface-enhanced Raman scattering and plasmonic photocatalysis of nitroaniline isomers on silver surfaces. The normal Raman and surface Raman spectra of nitroaniline isomers are first simulated and compared with experimental results. The calculated Raman spectra of o-nitroaniline (ONA), m-nitroaniline (MNA), and p-nitroaniline (PNA) correspond to their solid-state Raman spectra. However, the simulated surface Raman spectra of nitroaniline–silver complexes are significantly different from the experimental SERS spectra. According to the theoretical simulation, the appearance of new peaks in the SERS experiments of nitroaniline is attributed to the formation of new surface species. Two possible reaction routes, an oxidative coupling route and a reductive coupling route, are suggested to be involved in surface plasmon-mediated photocatalysis of nitroaniline on silver. It is found that the reaction route of nitroaniline on silver is strongly affected by the surroundings. The potential energy curves for the photocatalysis of PNA in the air and in the solution are presented. In the case that PNA is exposed in the air in the presence of oxygen, PNAs are oxidized to dinitroazobenzene (DNAB) by the surface activated oxygen species. In the case that PNA is immersed in the solution in the absence of oxygen, PNAs are reduced to diaminoazobenzene (DAAB) by the excited hot electrons. Finally, the Raman spectra of oxidative coupling product DNAB and reductive product DAAB are simulated. They are in good agreement with the abnormal Raman signals in SERS experiments of nitroaniline on silver.
Co-reporter:Ran Pang, Li-Juan Yu, Meng Zhang, Zhong-Qun Tian, and De-Yin Wu
The Journal of Physical Chemistry A 2016 Volume 120(Issue 42) pp:8273-8284
Publication Date(Web):September 30, 2016
DOI:10.1021/acs.jpca.6b07064
Strong hydrogen-bonding interaction and Raman spectra of hydrated proton have been investigated using hybrid density functional theory method B3LYP. The solvation model of density (SMD) approach is employed in the present calculation to simulate hydrated protons in aqueous solution. Focusing on the different hydrogen-bonded Eigen-water and Zundel-water interactions, we present a better assignment of Raman signals of hydrated proton on the basis of vibrational analysis in different environments. Our results showed that B3LYP calculations could give a good prediction for characteristic vibrational frequencies of Eigen and Zundel isomers in liquid phase. The O–H stretching vibrational frequencies from Eigen and Zundel units are very sensitive to hydrogen-bonding interaction with solvent water molecules. Moreover, the solvation effect and the external electric-field effect lead to the proton deviating from the central position of Zundel structure and finally resulting in a transition to Eigen one in aqueous solution. Furthermore, by combining theoretical prediction and Raman scattering theory, we calculate absolute Raman intensities of characteristic signals based on the polarizability tensor derivatives of hydrated proton clusters. This is very helpful to infer the microstructure of hydrated protons in aqueous solution by using Raman measurements.
Co-reporter:Rui Jiang
The Journal of Physical Chemistry C 2016 Volume 120(Issue 30) pp:16427-16436
Publication Date(Web):July 6, 2016
DOI:10.1021/acs.jpcc.6b04638
p-Aminothiophenol (PATP) is an important probe molecule in surface-enhanced Raman spectroscopy. The unique and strong SERS signals of PATP distinguished from its normal Raman spectrum were considered as a signal of an existing charge transfer mechanism. Recent theoretical and experimental studies demonstrate that PATP undergoes surface catalytic coupling reaction to produce an aromatic azo species p,p′-dimercaptoazobenzene (DMAB), which should be responsible for the abnormal signals in the observed SERS spectra of PATP. In this work, three aminothiophenol derivatives with different substitute position and conjugation degree between the amino group (−NH2) and mercapto group (−SH) were chosen to study the effects of substituent including adsorption orientation effect and conjugation effect on the reactivity of photoinduced surface catalytic coupling reactions. A combined SERS and DFT study indicated that no surface reactions occurred for compound C1 and compound C2, while compound C3 was converted to the corresponding azo species during their SERS measurements. The differences in reactivity of the selected probe molecules were investigated on the basis of proposed photoexcitation and photoreaction mechanisms.
Co-reporter:Liu-Bin Zhao
The Journal of Physical Chemistry C 2016 Volume 120(Issue 2) pp:944-955
Publication Date(Web):December 21, 2015
DOI:10.1021/acs.jpcc.5b07966
The surface plasmon catalytic selective aerobic oxidation of aromatic amines to aromatic azo compounds in metal/molecule/metal junctions was explored by density functional theory. The overall reaction could be divided into the initial plasmon-induced oxygen activation and the subsequent photothermal-driven dehydrogenation process. The activation of oxygen on silver and gold surfaces is proposed through a surface plasmon-mediated hot electron injection mechanism at solid/gas interface. Resonance absorption of incident light by metal nanostructures generates energetic electron–hole pairs. Time-dependent density functional theory calculations illustrate that the excited hot electrons created on metal surfaces can transfer to the antibonding 2π* orbital of adsorbed oxygen, which facilitates the dissociation of O2 on metal surfaces. Silver shows better catalytic performance for the oxygen activation due to its stronger surface plasmon resonance absorption intensity and higher hot electron energy level. Aromatic amines adsorbed on the metal surfaces can be selectively oxidized to the corresponding azo compounds by the activated surface oxygen species. The aerobic oxidations of p-aminothiophenol in the nanogaps between metal substrate and three different nanoparticles (Ag, Au, and Au@SiO2) are compared. The activated oxygen species on silver surfaces exhibits the strongest oxidation ability for its lowest reaction barriers of dehydrogenations. This work demonstrates that silver catalyst should be an excellent candidate for the heterogeneous photocatalysis, which can concurrently enhance oxygen dissociation and oxidative dehydrogenation reactions.
Co-reporter:Meng Zhang
The Journal of Physical Chemistry C 2016 Volume 120(Issue 22) pp:11956-11965
Publication Date(Web):May 20, 2016
DOI:10.1021/acs.jpcc.6b02252
Co-reporter:Yan-Li Chen, De-Yin Wu, and Zhong-Qun Tian
The Journal of Physical Chemistry A 2016 Volume 120(Issue 23) pp:4049-4058
Publication Date(Web):May 31, 2016
DOI:10.1021/acs.jpca.6b03604
We have theoretically investigated the substituent effect of adenine at the C8 position with a substituent X = H, F, Cl, and Br by using the density functional theory (DFT) at the B3LYP/6-311+G(d, p) level. The aim is to study the substituent effect of halogen atoms on the relative stability, vibrational frequencies, and solvation effect of tautomers. Our calculated results show that for substituted adenine molecules the N9H8X tautomer to be the most stable structure in gas phase at the present theoretical level. Here N9H8X denotes the hydrogen atom binds to the N9 position of imidazole ring and X denotes H, F, Cl, and Br atoms. The influence of the induced attraction of the fluorine substituent is significantly larger than chlorine and bromine ones. The halogen substituent effect has a significant influence on changes of vibrational frequencies and Raman intensities.
Co-reporter:Li-Kun Yang, Ya-Qiong Su, Xiao-Ying Wu, Da-Xiao Zhang, Yan-Li Chen, Fang-Zu Yang, De-Yin Wu and Zhong-Qun Tian
Nanoscale 2015 vol. 7(Issue 21) pp:9563-9569
Publication Date(Web):22 Apr 2015
DOI:10.1039/C5NR00664C
A novel, mild and effective method was designed for grafting of high-quality organic monolayers on a silicon surface to catalyze nanoparticles’ growth. By using a white-light source, 3-mercaptopropionic acid (3-MPA) molecules were attached to hydrogen-terminated Si(111) surfaces at room temperature. The attached monolayers were characterized using X-ray photoelectron spectroscopy to provide detailed information. The in situ growth of Au nanoparticles (AuNPs) with dimensions below 20 nm was catalyzed on a silicon surface with highly uniform and compact structure morphology. The AuNPs can grow selectively in a certain region on a patterned Si–Si3N4 chip. p-Nitrothiophenol (p-NTP) was used as the probe to evaluate the SERS enhancement of the highly uniform and compact AuNP–Si substrate. In order to better understand the white light initiation of the addition reaction of 3-MPA on the Si(111)–H surface, the mechanism was elucidated by density functional theoretical (DFT) calculations, which indicated that the formation of the Si–O bond occurred at the PEC of the first singlet excited state (S1) with a very low activation barrier about 30% of the ground state (S0) value.
Co-reporter:De-Yin Wu;Meng Zhang;Liu-Bin Zhao;Yi-Fan Huang;Bin Ren
Science China Chemistry 2015 Volume 58( Issue 4) pp:574-585
Publication Date(Web):2015 April
DOI:10.1007/s11426-015-5316-y
Nanoscale noble metals can exhibit excellent photochemical and photophysical properties, due to surface plasmon resonance (SPR) from specifically collective electronic excitations on these metal surfaces. The SPR effect triggers many new surface processes, including radiation and radiationless relaxations. As for the radiation process, the SPR effect causes the significant focus of light and enormous enhancement of the local surface optical electric field, as observed in surface-enhanced Raman spectroscopy (SERS) with very high detection sensitivity (to the single-molecule level). SERS is used to identify surface species and characterize molecular structures and chemical reactions. For the radiationless process, the SPR effect can generate hot carriers, such as hot electrons and hot holes, which can induce and enhance surface chemical reactions. Here, we review our recent work and related literature on surface catalytic-coupling reactions of aromatic amines and aromatic nitro compounds on nanostructured noble metal surfaces. Such reactions are a type of novel surface plasmon-enhanced chemical reaction. They could be simultaneously characterized by SERS when the SERS signals are assigned. By combining the density functional theory (DFT) calculations and SERS experimental spectra, our results indicate the possible pathways of the surface plasmon-enhanced photochemical reactions on nanostructures of noble metals. To construct a stable and sustainable system in the conversion process of the light energy to the chemical energy on nanoscale metal surfaces, it is necessary to simultaneously consider the hot electrons and the hot holes as a whole chemical reaction system.
Co-reporter:Liu-Bin Zhao
The Journal of Physical Chemistry C 2015 Volume 119(Issue 9) pp:4949-4958
Publication Date(Web):February 10, 2015
DOI:10.1021/jp512957c
The electroreduction of p-nitrothiophenol (PNTP) on gold and silver electrodes has been investigated by means of density functional theory. A combination of thermodynamic calculations and surface Raman/IR spectral simulations has allowed us to reveal the reaction mechanism and reaction products of electroreduction of PNTP on metal electrodes. First, thermodynamic calculations were carried out to calculate the standard electrode potentials of PNTP and its possible intermediates. The potential energy curves of PNTP reduction as a function of the applied potential are obtained on the basis of the calculated standard electrode potentials of the elementary electrochemical reactions. Second, surface vibrational spectral simulation was performed to provide theoretical assignments of reaction products for the in situ Raman/IR experimental studies of electroreduction of PNTP. The most interesting finding in the reaction product identified by IR spectroscopy is PATP; however, Raman spectroscopy shows that the main product is p,p′-dimercaptoazobenzene (DMAB). The difference between IR and Raman measurements arises from the fact that the incident laser used in Raman measurement can induce the formation of DMAB by photoreduction of PNTP or photo-oxidation of PATP. Finally, the reaction mechanism of electroreduction of PNTP was compared with its photoreduction mechanism.
Co-reporter:Meng Zhang, Li-Juan Yu, Yi-Fan Huang, Jia-Wei Yan, Guo-Kun Liu, De-Yin Wu, Zhong-Qun Tian and Bing-Wei Mao
Chemical Communications 2014 vol. 50(Issue 94) pp:14740-14743
Publication Date(Web):06 Oct 2014
DOI:10.1039/C4CC06269H
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.
Co-reporter:Zhao-Bin Chen, Zheng-Lian Peng, Jing-Hong Liang, Xiao-Shun Zhou, De-Yin Wu, C. Amatore, Bing-Wei Mao
Electrochemistry Communications 2014 Volume 47() pp:41-44
Publication Date(Web):October 2014
DOI:10.1016/j.elecom.2014.07.022
•Conductance of Au atomic contact (AC) is studied under interfacial charge transfer.•Conductance of Au AC changes from quantization to random distribution•Transient oxidation and structural relaxation of Au AC are proposed.This paper presents a work on hitherto unreported conductance alteration of gold atomic contact by electrochemical reduction of redox species at the contact. The interfacial charge transfer current due to reduction of Ru(NH3)63 + at Au atomic contacts can cause paradigm change of electron transport through the contacts: Conductance quantization is altered to random distribution with substantially reduced length of conductance plateau on the conductance traces. Transient oxidation of the Au atomic contact upon reduction of Ru(NH3)63 +, which relaxes atomic contact structures and hence the conductance, is proposed together with DFT calculation. The observations in the present work also disclose possible mechanistic information that might be generalized to electrochemical reduction at atomic scale.
Co-reporter:Li-Kun Yang ; Ya-Qiong Su ; Christopher T. Williams ; Fang-Zu Yang ; De-Yin Wu ;Zhong-Qun Tian
The Journal of Physical Chemistry C 2014 Volume 118(Issue 45) pp:25987-25993
Publication Date(Web):September 19, 2014
DOI:10.1021/jp5056073
Density functional theory calculations have been used to elucidate the mechanism of ultraviolet-induced functionalization of H–Si(111) surfaces with ethylene. The initial steps of this reaction involve the formation of a hole in the surface through photoemission and a partial restructuring of the surface. The H atom bound to the vacant site exhibits a significant chemical activity. Two competing pathways for this process involve a stochastic response mechanism and a chain reaction mechanism. These findings are discussed in light of recent experimental results of covalently attached monolayer formation on H–Si surfaces. The simulated infrared spectra of the two products were analyzed to elucidate the feature of the competing mechanisms.
Co-reporter:Dr. Yi-Fan Huang;Meng Zhang;Liu-Bin Zhao;Dr. Jia-Min Feng;Dr. De-Yin Wu;Dr. Bin Ren;Dr. Zhong-Qun Tian
Angewandte Chemie International Edition 2014 Volume 53( Issue 9) pp:2353-2357
Publication Date(Web):
DOI:10.1002/anie.201310097
Abstract
Surface plasmon resonances (SPRs) have been found to promote chemical reactions. In most oxidative chemical reactions oxygen molecules participate and understanding of the activation mechanism of oxygen molecules is highly important. For this purpose, we applied surface-enhanced Raman spectroscopy (SERS) to find out the mechanism of SPR-assisted activation of oxygen, by using p-aminothiophenol (PATP), which undergoes a SPR-assisted selective oxidation, as a probe molecule. In this way, SPR has the dual function of activating the chemical reaction and enhancing the Raman signal of surface species. Both experiments and DFT calculations reveal that oxygen molecules were activated by accepting an electron from a metal nanoparticle under the excitation of SPR to form a strongly adsorbed oxygen molecule anion. The anion was then transformed to Au or Ag oxides or hydroxides on the surface to oxidize the surface species, which was also supported by the heating effect of the SPR. This work points to a promising new era of SPR-assisted catalytic reactions.
Co-reporter:Liu-Bin Zhao, Meng Zhang, Yi-Fan Huang, Christopher T. Williams, De-Yin Wu, Bin Ren, and Zhong-Qun Tian
The Journal of Physical Chemistry Letters 2014 Volume 5(Issue 7) pp:1259-1266
Publication Date(Web):March 21, 2014
DOI:10.1021/jz5003346
Taking advantage of the unique capacity of surface plasmon resonance, plasmon-enhanced heterogeneous catalysis has recently come into focus as a promising technique for high performance light-energy conversion. This work performs a theoretical study on the reaction mechanism for conversions of p-aminothiophenol (PATP) and p-nitrothiophenol (PNTP) to aromatic azo species, p,p′-dimercaptoazobenzene (DMAB). In the absence of O2 or H2, the plasmon-driven photocatalysis mechanism (hot electron–hole reactions) is the major reaction channel. In the presence of O2 or H2, the plasmon-assisted surface catalysis mechanism (activated oxygen/hydrogen reactions) is the major reaction channel. The present results show that the coupling reactions of PATP and PNTP strongly depend on the solution pH, the irradiation wavelength, the irradiation power, and the nature of metal substrates as well as the surrounding atmosphere. The present study has drawn a fundamental physical picture for understanding plasmon-enhanced heterogeneous catalysis.Keywords: catalysis; density functional theory; photochemistry; potential energy surface; surface plasmon resonance;
Co-reporter:Dr. Yi-Fan Huang;Meng Zhang;Liu-Bin Zhao;Dr. Jia-Min Feng;Dr. De-Yin Wu;Dr. Bin Ren;Dr. Zhong-Qun Tian
Angewandte Chemie 2014 Volume 126( Issue 9) pp:2385-2389
Publication Date(Web):
DOI:10.1002/ange.201310097
Abstract
Surface plasmon resonances (SPRs) have been found to promote chemical reactions. In most oxidative chemical reactions oxygen molecules participate and understanding of the activation mechanism of oxygen molecules is highly important. For this purpose, we applied surface-enhanced Raman spectroscopy (SERS) to find out the mechanism of SPR-assisted activation of oxygen, by using p-aminothiophenol (PATP), which undergoes a SPR-assisted selective oxidation, as a probe molecule. In this way, SPR has the dual function of activating the chemical reaction and enhancing the Raman signal of surface species. Both experiments and DFT calculations reveal that oxygen molecules were activated by accepting an electron from a metal nanoparticle under the excitation of SPR to form a strongly adsorbed oxygen molecule anion. The anion was then transformed to Au or Ag oxides or hydroxides on the surface to oxidize the surface species, which was also supported by the heating effect of the SPR. This work points to a promising new era of SPR-assisted catalytic reactions.
Co-reporter:Liu-Bin Zhao ; Meng Zhang ; Bin Ren ; Zhong-Qun Tian
The Journal of Physical Chemistry C 2014 Volume 118(Issue 46) pp:27113-27122
Publication Date(Web):October 22, 2014
DOI:10.1021/jp507987x
The electro-oxidation of p-aminothiophenol (PATP) on gold electrodes has been investigated by means of density functional theory. A combination of thermodynamic calculations and surface Raman and infrared (IR) spectral simulations has allowed us to reveal the electro-oxidation mechanism and reaction products of PATP on gold electrodes in acidic, neutral, and basic solutions. PATP can be first oxidized to the radical cation PATP(NH2•+) or the neutral radical PATP(NH•) depending on the pH of aqueous solutions, and this is the rate-determining step. The radical cation or neutral radical can then transform to the dimerized products through a radical coupling reaction. In the acidic medium, the radical cation reacts with its resonance hybrid through a N–C4 coupling to form 4′-mercapto-N-phenyl-1,4-quinone diimine (D1), which can further undergo hydrolysis to yield 4′-mercapto-N-phenyl-1,4-quinone monoimine (D2). In the neutral medium, the neutral radical reacts with its resonance hybrid through the N–C2(6) coupling to form 4,4′-dimercapto-N-phenyl-1,2-quinone diimine (D3). In the basic medium, the neutral radical reacts with its resonance structure through the N–N coupling to form 4,4′-dimercaptoazobenzene (D4). The adsorbed dimer products exhibit reversible redox properties. The calculated standard electrode potentials of the above four species decrease in the order D3, D1, D2, and D4. Finally, the characteristic bands for the surface Raman and IR spectra of D1 to D4 redox pairs are clearly assigned. This study provides mechanistic insight into the electrochemical reaction properties of PATP on metal electrodes.
Co-reporter:Ran Pang, Li-Juan Yu, De-Yin Wu, Bing-Wei Mao, Zhong-Qun Tian
Electrochimica Acta 2013 Volume 101() pp:272-278
Publication Date(Web):1 July 2013
DOI:10.1016/j.electacta.2013.03.069
Noble metal catalysts, such as silver and gold, play a significant role in photocatalytic water splitting to hydrogen for their high efficiency and environmentally-friendly nature. In this paper, a surface electron–hydronium ion-pair (EHIP) was proposed as an intermediate for photocatalytic hydrogen evolution reaction (HER) on silver and gold cathodes based on density functional theory (DFT) calculations. The EHIP is in the configuration of H3O+(H2O)ne−, where the hydronium H3O+ and the electron is separated by water layers. The electron bound in the EHIP can first be excited under light irradiation, subsequently inducing a structural relaxation into a hydrated hydrogen atom. Eventually, two hydrogen atoms recombine into a hydrogen molecule in the thin layer close to the electrode surface, e.g. at the outer Helmholtz plane (OHP). Additionally, Raman spectra of the interfacial EHIP species are calculated, which is in support of the presence of EHIP intermediates in the process of photocatalytic HER on silver and gold cathodes.
Co-reporter:Sha Tao, Li-Juan Yu, Ran Pang, Yi-Fan Huang, De-Yin Wu, and Zhong-Qun Tian
The Journal of Physical Chemistry C 2013 Volume 117(Issue 37) pp:18891-18903
Publication Date(Web):August 21, 2013
DOI:10.1021/jp4042777
The wagging mode is a characteristic out-of-plane bending vibration for a series of organic compounds containing −CH2/–NH2 groups, such as terminal olefins, p-substituted aniline derivates, and benzyl radicals. The SERS signal of the wagging mode is always sensitive to the interfacial interaction, displaying significant frequency shift and Raman enhancement. To understand the origin of the special SERS signal, density functional theory (DFT) calculation is performed to obtain harmonic vibrational frequencies and Raman intensities of equilibrium structures for the p−π conjugated molecules adsorbed on silver surfaces on the basis of the molecule–metallic cluster model. Our results showed that the frequency shift of the wagging mode is strongly dependent on the hybridization effect, the sp2 changing to sp3 hybridization causes a dramatic frequency shift for the wagging mode. Furthermore, our results also revealed the causes of the remarkable enhancement of this mode in SERS intensity. From the point of view of the frontier molecular orbital interaction and the change of electronic structures, the derivatives of polarizability tensor for the wagging coordinate are quite large appearing at the significant extent of the geometry deformation, closely associated with the p−π conjugation effect and the hybridization property, as well as the energy exchange of the frontier molecular orbitals. The last factor results in significant increases in the derivatives of polarizability tensor along with the direction of the wagging vibrations.
Co-reporter:Rong Huang, Hong-Tao Yang, Li Cui, De-Yin Wu, Bin Ren, and Zhong-Qun Tian
The Journal of Physical Chemistry C 2013 Volume 117(Issue 45) pp:23730-23737
Publication Date(Web):October 15, 2013
DOI:10.1021/jp407615r
The interaction of adenine with silver surfaces has been investigated using density functional method. Two isomers of N9H and N7H were included to model surface species. Considering the complexity of silver surfaces in surface-enhanced Raman spectroscopy, neutral and positive silver clusters were used to mimic the substrate. Following the bonding principle, we consider adenine-approached silver clusters in different configurations and their relation to the Raman spectra. For neutral adenine Agn (n = 4, 7, and 9) complexes, N9H–Agn complexes are more stable than N7H–Agn ones. The corresponding Raman spectra strongly depended on the structure of adenine and the adsorption sites. Moreover, we find N7H interacts with one positively charged silver cluster via N3 and N9 at the same time as the most stable surface complex, which can reproduce the experimental surface Raman spectra of adenine well on silver surfaces.
Co-reporter:Liu-Bin Zhao, Yi-Fan Huang, Xiu-Min Liu, Jason R. Anema, De-Yin Wu, Bin Ren and Zhong-Qun Tian
Physical Chemistry Chemical Physics 2012 vol. 14(Issue 37) pp:12919-12929
Publication Date(Web):30 Jul 2012
DOI:10.1039/C2CP41502J
We propose that aromatic nitro and amine compounds undergo photochemical reductive and oxidative coupling, respectively, to specifically produce azobenzene derivatives which exhibit characteristic Raman signals related to the azo group. A photoinduced charge transfer model is presented to explain the transformations observed in para-substituted ArNO2 and ArNH2 on nanostructured silver due to the surface plasmon resonance effect. Theoretical calculations show that the initial reaction takes place through excitation of an electron from the filled level of silver to the lowest unoccupied molecular orbital (LUMO) of an adsorbed ArNO2 molecule, and from the highest occupied molecular orbital (HOMO) of an adsorbed ArNH2 molecule to the unoccupied level of silver, during irradiation with visible light. The para-substituted ArNO2−˙ and ArNH2+˙ surface species react further to produce the azobenzene derivatives. Our results may provide a new strategy for the syntheses of aromatic azo dyes from aromatic nitro and amine compounds based on the use of nanostructured silver as a catalyst.
Co-reporter:Yonghui He, Shu Chen, Younian Liu, Yizeng Liang, Juan Xiang, Deyin Wu, Feimeng Zhou
Journal of Inorganic Biochemistry 2012 Volume 113() pp:9-14
Publication Date(Web):August 2012
DOI:10.1016/j.jinorgbio.2012.02.035
Understanding the structure of mammal Bi-containing metallothionein-2 (Bi-MT2) is of great physiological significance due to the importance of Bi-MT2 in alleviating adverse effect of anti-cancer drugs. A unique feature of rabbit liver Bi-MT2 is the metal–oxygen bond (BiO), which is absent in well-characterized Zn-MT2 and Cd-MT2. However, the ligand contributing to the BiO bonding in Bi-MT2 remains unidentified. In this study, the coordination of Bi3+ to rabbit liver metal-free metallothionein was investigated using both experimental and theoretical methods. UV–visible and circular dichroism spectra indicate that Bi-MT2 has a different secondary structure from those of Zn-MT2 and Cd-MT2. Three possible Bi3+ coordination structures in Bi7-MT2 and relative binding free energies were calculated using the density functional theory. Absorption spectra corresponding to these coordination structures were evaluated by time-dependent density functional theory. Our computation results are consistent with the UV–vis spectroscopic data and strongly suggest that the carboxyl group in the aspartic acid residues contributes to the BiO bond formation.UV–visible and circular dichroism spectra of Bi3+ binding to metal-free metallothionein, combined with DFT computation results, strongly suggest that the carboxyl group in the aspartic acid residues contributes to the BiO bond formation Bi7-MT.Highlights► The spectral characterizations of Bi3+ binding to thionein are described. ► A new Bi3+ coordination mode in Bi7-MT is proposed. ► The oxygen donating to Bi3+ is found to derive from a carboxyl group of aspartate.
Co-reporter:De-Yin Wu, Liu-Bin Zhao, Xiu-Min Liu, Rong Huang, Yi-Fan Huang, Bin Ren and Zhong-Qun Tian
Chemical Communications 2011 vol. 47(Issue 9) pp:2520-2522
Publication Date(Web):25 Jan 2011
DOI:10.1039/C0CC05302C
When p-aminothiophenol (PATP) is used as a probe molecule and adsorbs on silver and gold nanogaps, a significant change of relative SERS intensities can be observed. Our DFT calculations show that surface photocatalytic coupling reactions yield a new surface species of p,p′-dimercaptoazobenzene (DMAB) causing the significant change in the SERS spectra.
Co-reporter:Liu-Bin Zhao ; Rong Huang ; Mu-Xing Bai ; De-Yin Wu ;Zhong-Qun Tian
The Journal of Physical Chemistry C 2011 Volume 115(Issue 10) pp:4174-4183
Publication Date(Web):February 23, 2011
DOI:10.1021/jp1117135
The adsorption mechanism of aromatic amines on noble metal surfaces and the amine−metal interaction effects on Raman spectroscopy are studied by density functional theory. We find that donation of nitrogen lone-paired electrons plays an important role in the amine−metal interaction. The interaction will be enhanced when aniline adsorbs on positively charged metal clusters because of the electrostatic attraction. It is observed that the Raman signal of the NH2 group is sensitive to the amine−metal interaction. A significant frequency shift and abnormal giant Raman enhancement of the NH2 wagging (ωNH2) mode are predicted theoretically when aniline and its derivatives attach to noble metal surfaces with the amino group. The origin of the frequency shift and the enhanced Raman intensity as well as the line shape broadening has been discussed in detail. Using the characteristic Raman signals of ωNH2, we can infer the adsorption configuration and estimate the strength of the amine−metal interaction. Our calculated results propose that the phenomenon can be extended to other surface probe molecules containing the amino group for investigating amine−metal interactions on SERS active metal substrates.
Co-reporter:Rong Huang ; Liu-Bin Zhao ; De-Yin Wu ;Zhong-Qun Tian
The Journal of Physical Chemistry C 2011 Volume 115(Issue 28) pp:13739-13750
Publication Date(Web):June 10, 2011
DOI:10.1021/jp201977z
Stable structures and vibrational spectra of adenine and adenine–Ag+ complexes which might exist on silver surfaces have been investigated by hybrid density functional B3LYP and ab initio MP2 methods. For adenine–Ag+ complexes, considered as monomeric species, there are two stable structures (i-1H-9H-Ag7 and 7H-Ag3) in the gas phase and four stable structures (9H-Ag1, 9H-Ag3, 9H-Ag7 and 7H-Ag3) in aqueous solution calculated with a solvation model of density (SMD). Analyzing the vibrational spectra of these stable structures in the gas phase and in aqueous solution, we can find that Ag+ influences the spectra significantly and different tautomers can be distinguished from each other on the basis of characteristic bands of their vibrational spectra. Furthermore, we propose that the dimer of 7H-Ag3 should be the most stable structure in aqueous solution though 7H-Ag3 is not the most stable one in the gas phase. This is supported by the predicted Gibbs free energy of the dimerization process and experimental Raman spectra of the adenine–Ag+ complex.
Co-reporter:Yi-Fan Huang ; Hong-Ping Zhu ; Guo-Kun Liu ; De-Yin Wu ; Bin Ren ;Zhong-Qun Tian
Journal of the American Chemical Society 2010 Volume 132(Issue 27) pp:9244-9246
Publication Date(Web):June 8, 2010
DOI:10.1021/ja101107z
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.
Co-reporter:Jian-Feng Li, Yi-Fan Huang, Sai Duan, Ran Pang, De-Yin Wu, Bin Ren, Xin Xu and Zhong-Qun Tian
Physical Chemistry Chemical Physics 2010 vol. 12(Issue 10) pp:2493-2502
Publication Date(Web):26 Jan 2010
DOI:10.1039/B919266B
The observed surface-enhanced Raman scattering (SERS) spectra of water adsorbed on metal film electrodes of silver, gold, and platinum nanoparticles were used to infer interfacial water structures on the basis of the change of the electrochemical vibrational Stark tuning rates and the relative Raman intensity of the stretching and bending modes. To explain the increase of the relative Raman intensity ratio of the bending and stretching vibrations at the very negative potential region, density functional theory calculations provide the conceptual model. The specific enhancement effect for the bending mode was closely associated with the water adsorption structure in a hydrogen bonded configuration through its H-end binding to surface sites with large polarizability due to strong cathodic polarization. The present results allow us to propose that interfacial water molecules exist on these metal cathodes with different hydrogen bonding interactions, i.e., the HO–H⋯H–Pt dihydrogen bond for platinum and the HO–H⋯Ag(Au) for silver and gold. This dihydrogen bonding configuration on platinum is further supported from observation of the Pt–H stretching band. Furthermore, the influences of the pH effect on SERS intensity and vibrational Stark effect on the gold electrode indicate that the O–H stretching SERS signals are enhanced in the alkaline solutions because of the hydrated hydroxide surface species adsorbed on the gold cathode.
Co-reporter:Yi-Fan Huang;Nai-Ning Yin;Xiang Wang, Dr.;Bin Ren Dr. ;Zhong-Qun Tian Dr.
Chemistry - A European Journal 2010 Volume 16( Issue 5) pp:1449-1453
Publication Date(Web):
DOI:10.1002/chem.200902199
Co-reporter:De-Yin Wu, Xiu-Min Liu, Yi-Fan Huang, Bin Ren, Xin Xu and Zhong-Qun Tian
The Journal of Physical Chemistry C 2009 Volume 113(Issue 42) pp:18212-18222
Publication Date(Web):September 11, 2009
DOI:10.1021/jp9050929
p-Mercaptoaniline (pMA, it is often called p-aminothiophenol (PATP)) can form self-assembled monolayer (SAM) through its thiol group on metal surfaces. It is also an important surface probe molecule in the surface-enhanced Raman spectroscopy (SERS). More recently, pMA has been used in molecular electronics as a single-molecule conductance wire to link two nanoscale metal leads, constructing a molecular wire junction. When pMA adsorbs on these metal nanostructures and nanogaps, there exhibit strongly detectable surface Raman signals of “non-totally symmetric” modes. The abnormal enhancement mechanisms proposed in the literature fall into three different categories, i.e., photoinduced charge transfer, tautomerization of benzenoid and quinonoid states, and the charge tunneling enhancement mechanism. Here, we present a novel mechanism to understand the observed SERS for pMA adsorbed on silver surfaces. On the basis of our theoretical calculations combined with the reports in literatures, we propose that the pMA molecules adsorbed on nanoscale rough surfaces of noble metals and nanoparticles undergo a catalytic coupling reaction to selectively produce a new surface species p,p′-dimercaptoazobenzene (DMAB), an aromatic azo compound, which is responsible for the experimentally observed Raman spectra. The present results are important for understanding many pMA-related experiments on noble nanoparticles.
Co-reporter:Yu-Xiong Jiang, Jian-Fen Li, De-Yin Wu, Zhi-Lin Yang, Bin Ren, Jia-Wen Hu, Yuan L. Chow and Zhong-Qun Tian
Chemical Communications 2007 (Issue 44) pp:4608-4610
Publication Date(Web):09 Oct 2007
DOI:10.1039/B711218A
We utilized the strategy of ‘borrowing SERS activity’, by chemically coating several atomic layers of a Pt-group metal on highly SERS-active Au nanoparticles, to obtain the first SERS (also Raman) spectra of surface water on Pt and Pd metals, and propose conceptual models for water adsorbed on Pt and Pd metal surfaces.
Co-reporter:De-Yin Wu;Bin Ren;Zhong-Qun Tian
Israel Journal of Chemistry 2006 Volume 46(Issue 3) pp:317-327
Publication Date(Web):10 MAR 2010
DOI:10.1560/IJC_46_3_317
Since the mid-1990s good quality surface-enhanced Raman spectra have been obtained from many transition metal (TM) electrodes. It has been observed quite often that SERS band intensities, i.e., the relative intensities of different vibrational modes, of the adsorbate are very sensitive to the nature of the metal. Since transition metals interact with adsorbed molecules much more strongly than the typical SERS substrates, i.e., Au, Ag, and Cu, it is desirable to give a detailed and quantitative explanation of the spectroscopic behavior on TM electrodes. In the present study, a hybrid density functional approach with 6–311+G**/LanL2DZ basis sets and the B3LYP nonlocal exchange-correlation functionals has been used for the Raman intensity analysis on totally symmetric modes of pyridine adsorbed at transition metal electrodes, e.g., iron, cobalt, nickel, palladium, and platinum. Among all studied metal electrodes, iron and cobalt are predicted to be the most effective SERS substrates involving chemical enhancement, a result in good agreement with the experiments. The chemical bonding enhancement plays a role in pyridine interaction with the transition metal electrodes. The charge transfer enhancement as the most common chemical mechanism is also discussed for comparison.
Co-reporter:De-Yin Wu;Bin Ren;Zhong-Qun Tian
ChemPhysChem 2006 Volume 7(Issue 3) pp:619-628
Publication Date(Web):3 MAR 2006
DOI:10.1002/cphc.200500439
The binding interactions between pyridine and bimetallic silver–gold clusters are investigated using density functional theory (DFT). The binding energies of pyridine–bimetallic cluster complexes indicate that the bonding depends strongly on the binding site (Au or Ag atom) and bonding molecular orbitals in a given configuration. The donation of the lone-pair electrons of the nitrogen of pyridine to an appropriate unoccupied orbital of each metal cluster plays an important role. The low-lying excited states and charge-transfer states of four stable complexes of interest are calculated on the basis of a time-dependent DFT method. In nonresonance Raman scattering processes, the influence of binding interactions on the relative Raman intensity of totally symmetric pyridine vibrational modes is discussed. These calculated relative Raman intensities are compared with observed surface-enhanced Raman spectra of pyridine adsorbed on silver–gold alloy surfaces.
Co-reporter:Liu-Bin Zhao, Yi-Fan Huang, Xiu-Min Liu, Jason R. Anema, De-Yin Wu, Bin Ren and Zhong-Qun Tian
Physical Chemistry Chemical Physics 2012 - vol. 14(Issue 37) pp:NaN12929-12929
Publication Date(Web):2012/07/30
DOI:10.1039/C2CP41502J
We propose that aromatic nitro and amine compounds undergo photochemical reductive and oxidative coupling, respectively, to specifically produce azobenzene derivatives which exhibit characteristic Raman signals related to the azo group. A photoinduced charge transfer model is presented to explain the transformations observed in para-substituted ArNO2 and ArNH2 on nanostructured silver due to the surface plasmon resonance effect. Theoretical calculations show that the initial reaction takes place through excitation of an electron from the filled level of silver to the lowest unoccupied molecular orbital (LUMO) of an adsorbed ArNO2 molecule, and from the highest occupied molecular orbital (HOMO) of an adsorbed ArNH2 molecule to the unoccupied level of silver, during irradiation with visible light. The para-substituted ArNO2−˙ and ArNH2+˙ surface species react further to produce the azobenzene derivatives. Our results may provide a new strategy for the syntheses of aromatic azo dyes from aromatic nitro and amine compounds based on the use of nanostructured silver as a catalyst.
Co-reporter:Yu-Xiong Jiang, Jian-Fen Li, De-Yin Wu, Zhi-Lin Yang, Bin Ren, Jia-Wen Hu, Yuan L. Chow and Zhong-Qun Tian
Chemical Communications 2007(Issue 44) pp:NaN4610-4610
Publication Date(Web):2007/10/09
DOI:10.1039/B711218A
We utilized the strategy of ‘borrowing SERS activity’, by chemically coating several atomic layers of a Pt-group metal on highly SERS-active Au nanoparticles, to obtain the first SERS (also Raman) spectra of surface water on Pt and Pd metals, and propose conceptual models for water adsorbed on Pt and Pd metal surfaces.
Co-reporter:Meng Zhang, Li-Juan Yu, Yi-Fan Huang, Jia-Wei Yan, Guo-Kun Liu, De-Yin Wu, Zhong-Qun Tian and Bing-Wei Mao
Chemical Communications 2014 - vol. 50(Issue 94) pp:NaN14743-14743
Publication Date(Web):2014/10/06
DOI:10.1039/C4CC06269H
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.
Co-reporter:De-Yin Wu, Liu-Bin Zhao, Xiu-Min Liu, Rong Huang, Yi-Fan Huang, Bin Ren and Zhong-Qun Tian
Chemical Communications 2011 - vol. 47(Issue 9) pp:NaN2522-2522
Publication Date(Web):2011/01/25
DOI:10.1039/C0CC05302C
When p-aminothiophenol (PATP) is used as a probe molecule and adsorbs on silver and gold nanogaps, a significant change of relative SERS intensities can be observed. Our DFT calculations show that surface photocatalytic coupling reactions yield a new surface species of p,p′-dimercaptoazobenzene (DMAB) causing the significant change in the SERS spectra.
Co-reporter:Jian-Feng Li, Yi-Fan Huang, Sai Duan, Ran Pang, De-Yin Wu, Bin Ren, Xin Xu and Zhong-Qun Tian
Physical Chemistry Chemical Physics 2010 - vol. 12(Issue 10) pp:NaN2502-2502
Publication Date(Web):2010/01/26
DOI:10.1039/B919266B
The observed surface-enhanced Raman scattering (SERS) spectra of water adsorbed on metal film electrodes of silver, gold, and platinum nanoparticles were used to infer interfacial water structures on the basis of the change of the electrochemical vibrational Stark tuning rates and the relative Raman intensity of the stretching and bending modes. To explain the increase of the relative Raman intensity ratio of the bending and stretching vibrations at the very negative potential region, density functional theory calculations provide the conceptual model. The specific enhancement effect for the bending mode was closely associated with the water adsorption structure in a hydrogen bonded configuration through its H-end binding to surface sites with large polarizability due to strong cathodic polarization. The present results allow us to propose that interfacial water molecules exist on these metal cathodes with different hydrogen bonding interactions, i.e., the HO–H⋯H–Pt dihydrogen bond for platinum and the HO–H⋯Ag(Au) for silver and gold. This dihydrogen bonding configuration on platinum is further supported from observation of the Pt–H stretching band. Furthermore, the influences of the pH effect on SERS intensity and vibrational Stark effect on the gold electrode indicate that the O–H stretching SERS signals are enhanced in the alkaline solutions because of the hydrated hydroxide surface species adsorbed on the gold cathode.
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