Influence of different copper(II) salts on the oxidation and doping reactions of emeraldine base polyaniline

A spectroscopic investigation of the products formed in the reaction of emeraldine base (EB-PANI) with copper(II) ions in dimethylacetamide (DMA) is presented. It is well known that metal cations can dope emeraldine base polyaniline (EB-PANI) through a pseudo-protonation reaction. Resonance Raman, UV–vis-NIR, and EPR data, obtained for Cu²⁺/EB-PANI solutions prepared using CuCl₂·2 H₂O, Cu(NO₃)₂· 3 H₂O or Cu(CH₃COO)₂·H₂O as Cu²⁺ sources, showed that the species formed in reactions of EB-PANI and Cu²⁺ ions are dependent on the anions of the copper salt employed. EPR spectra pointed out that the environments of Cu²⁺ ions with acetate, chloride or nitrate as anions in DMA solution are distinct. Resonance Raman and UV–vis-NIR data demonstrated that the main reactions are the oxidation of EB-PANI to pernigraniline base (PB-PANI) and doping of EB-PANI to ES-PANI (emeraldine salt) when a direct coordination of Cu²⁺ ions to PANI exists. With nitrate as very weak coordinating anion, ES-PANI is formed preferentially. When copper chloride is used, both oxidation and doping of EB-PANI are verified. Conversely with acetate, the dimeric cage structure of this copper salt is preserved in solution, and oxidation of EB-PANI to PB-PANI is the only observed reaction. These results demonstrate the possibility of modulating the products of reaction between Cu²⁺ ions and EB-PANI in DMA solution by changing the counter ion of the Cu²⁺ source.     

Fabrication and Formation Mechanism of Ag Nanoplate‐Decorated Nanofiber Mats and Their Application in SERS

We report a new simple method to fabricate a highly active SERS substrate consisting of poly‐m‐phenylenediamine/polyacrylonitrile (PmPD/PAN) decorated with Ag nanoplates. The formation mechanism of Ag nanoplates is investigated. The synthetic process of the Ag nanoplate‐decorated PmPD/PAN (Ag nanoplates@PmPD/PAN) nanofiber mats consists of the assembly of Ag nanoparticles on the surface of PmPD/PAN nanofibers as crystal nuclei followed by in situ growth of Ag nanoparticles exclusively into nanoplates. Both the reducibility of the polymer and the concentration of AgNO₃ are found to play important roles in the formation and the density of Ag nanoplates. The optimized Ag nanoplates@PmPD/PAN nanofiber mats exhibit excellent activity and reproducibility in surface‐enhanced Raman scattering (SERS) detection of 4‐mercaptobenzoic acid (4‐MBA) with a detection limit of 10^?10 m , making the Ag nanoplates@PmPD/PAN nanofiber mats a promising substrate for SERS detection of chemical molecules. In addition, this work also provides a design and fabrication process for a 3D SERS substrate made of a reducible polymer with noble metals.     

Local and Remote Charge‐Transfer‐Enhanced Raman Scattering on One‐Dimensional Transition‐Metal Oxides

The one‐dimensional (1D) transition‐metal oxide MoO₃ belt is synthesized and characterized with X‐ray diffraction, scanning electron microscopy, and Raman spectroscopy. Charge‐transfer‐(CT) enhanced Raman scattering of 4‐mercaptobenzoic acid (4‐MBA) on a 1D MoO₃ belt was investigated experimentally and theoretically. The chemical enhancement of surface‐enhanced Raman scattering (SERS) of 4‐MBA on the MoO₃ belt by CT is in the order of 10³. The SERS of 4‐MBA was investigated theoretically by using a quantum chemical method. The remote SERS of 4‐MBA along the 1D MoO₃ belt (the light excitation to one side of the MoO₃ belt, and the SERS spectrum is collected on the other side of the MoO₃ belt) is also shown experimentally, which provides potential applications of SERS. The incident polarization dependence of remote SERS spectra has also been investigated experimentally.     

Highly Reproducible Surface‐Enhanced Raman Spectra on Semiconductor SnO2 Octahedral Nanoparticles

Highly reproducible surface‐enhanced Raman scattering (SERS) spectra are obtained on the surface of SnO₂ octahedral nanoparticles. The spot‐to‐spot SERS signals show a relative standard deviation (RSD) consistently below 20 % in the intensity of the main Raman peaks of 4‐mercaptobenzoic acid (4‐MBA) and 4‐nitrobenzenethiol (4‐NBT), indicating good spatial uniformity and reproducibility. The SERS signals are believed to mainly originate from a charge‐transfer (CT) mechanism. Time‐dependent density functional theory (TD‐DFT) is used to simulate the SERS spectrum and interpret the chemical enhancement mechanism in the experiment. The research extends the application of SERS and also establishes a new uniform SERS substrate.     

pH值和阴离子对吡啶2,6-二羧酸在金纳米颗粒表面的增强拉曼散射的影响

表面增强拉曼散射(SERS)被用于检测细菌芽抱中的一种重要的标志物吡啶2,6-羧酸(DPA).以聚乙烯吡啶烷酮(PVP)为粘合剂,将60 nm的金粒子组装到表面打磨光滑的金电极上,制备稳定、灵敏的SERS基底.通过不同pH值下吸附在金基底上的DPA的SERS特征,考察DPA分子吸附构型发生的变化,并分析酸根离子对其吸附...     

Real‐time measurement of peroxyacetyl nitrate using selected ion flow tube mass spectrometry

The on‐line detection of gaseous peroxyacetyl nitrate (PAN) using selected ion flow tube mass spectrometry (SIFT‐MS) has been investigated using a synthetic sample of PAN in air at a humidity of ～30%. Using the H₃O⁺ reagent ion, signals due to PAN at m/z 122, 77 and 95 have been identified. These correspond to protonated PAN, protonated peractetic acid and its water cluster, respectively. These products and their energetics have been probed through quantum mechanical calculations. The rate coefficient of H₃O⁺ has been estimated to be 4.5 × 10^?9 cm³ s^?1, leading to a PAN sensitivity of 138 cps/ppbv. This gives a limit of detection of 20 pptv in 10 s using the [M+H]⁺ ion of PAN at m/z 122. Copyright © 2010 John Wiley & Sons, Ltd.     

Monitoring of Endogenous Hydrogen Sulfide in Living Cells Using Surface‐Enhanced Raman Scattering

Hydrogen sulfide (H₂S) has emerged as an important gasotransmitter in diverse physiological processes, although many aspects of its roles remain unclear, partly owing to a lack of robust analytical methods. Herein we report a novel surface‐enhanced Raman scattering (SERS) nanosensor, 4‐acetamidobenzenesulfonyl azide‐functionalized gold nanoparticles (AuNPs/4‐AA), for detecting the endogenous H₂S in living cells. The detection is accomplished with SERS spectrum changes of AuNPs/4‐AA resulting from the reaction of H₂S with 4‐AA on AuNPs. The SERS nanosensor exhibits high selectivity toward H₂S. Furthermore, AuNPs/4‐AA responds to H₂S within 1 min with a 0.1 μM level of sensitivity. In particular, our SERS method can be utilized to monitor the endogenous H₂S generated in living glioma cells, demonstrating its great promise in studies of pathophysiological pathways involving H₂S.     

Theoretical Investigation on SERS of Pyridine Adsorbed on Cn Clusters Induced by Charge Transfer: A Hint that SERS Could be Applied on Many Materials

The SERS spectra of pyridine–C_n (n=1–6) complexes are investigated theoretically. The obtained enhancement factors of about 10²–10³ in the pre‐resonance Raman spectrum calculations are attributed to charge‐transfer transitions from the carbon clusters to pyridine, where a good match of band structures between substrates and probe molecules is essential.     

High‐Quality Covalently Grafting Hemoglobin on Gold Electrodes: Characterization,Redox Thermodynamics and Bio‐electrocatalysis

Herein, we report a versatile surface chemistry methodology to covalently immobilize ligands and proteins to self‐assembled monolayers (SAMs) on gold electrode. The strategy is based on two steps: 1) the coupling of soluble azido‐PEG‐amimo ligand with an alkynyl‐terminated monolayer via click reaction and 2) covalent immobilization hemoglobin (Hb) to the amine‐terminated ligand via carbodiimide reaction. Surface‐enhanced Raman scattering spectroscopy (SERS), atomic force microscopy (AFM), reflection absorption infrared spectroscopy (RAIR) and cyclic voltammetry are used to characterize the model interfacial reactions. We also demonstrate the excellent biocompatibility of the interface for Hb immobilization and reliable application of the proposed method for H₂O₂ biosensing. Moreover, the redox thermodynamics of the Fe³⁺/Fe²⁺ couple in Hb is also investigated.     

Biomimetic preparation of core‐shell structured surface‐enhanced Raman scattering substrate with antifouling ability,good stability,and reliable quantitative capability

The fouling and stability are two most critical limiting factors for practical applications of surface‐enhanced Raman scattering (SERS)‐based microfluidic electrophoresis device. Herein, we present a novel biomimetic nanoengineering strategy to achieve a SERS substrate featuring antifouling ability, good stability, and reliable quantitative capability. Typically, by employing tea polyphenol as the reducing agent, the substrate made of silver core‐gold shell nanostructures in situ grown on silicon wafer surface is fabricated. The core‐shell nanostructures are further embedded with internal standard molecules. Remarkably, the fabricated substrate preserves distinct SERS effects, adaptable reproducibility, and reliable quantitative ability even if the substrate is incubated with 15% H₂O₂, 13% HNO₃, or 10⁸ CFU/mL bacteria, or suffered from 12‐day continuous vibration at 250 rpm/min in PBS buffer. As a proof‐of‐concept application, the DNA‐functionalized substrate is capable of precise quantification of Hg²⁺ with a limit of detection down to ca. 1 pM even in sewage water.     

Surface enhanced raman and resonance raman spectroscopy in a non-aqueous electrochemical environment: Tris(2,2′-bipyridine)ruthenium(II) adsorbed on silver from acetonitrile

This letter reports the first observation of both surface enhanced Raman scattering (SERS) and surface enhanced resonance Raman scattering (SERRS) from the transition metal complex tris(2,2′-bipyridine)ruthenium (II), Ru(bpy)₃²⁺, adsorbed on a silver electrode from acetonitrile (ACN). The assignment of these spectra as valid examples of SERS and SERRS in a non-aqueous environment is based on the following criteria: (1) in situ demonstration of monolayer surface coverage of Ru(bpy)₃²⁺ using double potential step chronocoulometry (DPSCC); (2) the Raman signals are most intense after surface roughening by anodization; (3) the Raman spectra are potential dependent in the non-faradaic potential region; (4) the measured enhancement factors are greater ilian 10⁶; (5) the surface spectra are frequency shifted relative to their bulk counterpart; and (6) several other molecules also exhibit non-aqueous SERS and SERRS behavior. These results are highly significant in that generality of surface enhanced Raman spectroscopy has been extended into the rich domain of nonaqueous electrochemistry.     

Infrared Spectra of Protonated Coronene and Its Neutral Counterpart in Solid Parahydrogen: Implications for Unidentified Interstellar Infrared Emission Bands

Large protonated polycyclic aromatic hydrocarbons (H⁺PAHs) are possible carriers of unidentified infrared (UIR) emission bands from interstellar objects, but the characterization of infrared (IR) spectra of large H⁺PAHs in the laboratory is challenging. IR absorption spectra of protonated coronene (1‐C₂₄H₁₃⁺) and mono‐hydrogenated coronene (1‐C₂₄H₁₃^.), which were produced upon electron bombardment of parahydrogen containing a small proportion of coronene (C₂₄H₁₂) during matrix deposition, were recorded. The spectra are of a much higher resolution than those obtained by IR multiphoton dissociation by Dopfer and co‐workers. The IR spectra of protonated pyrene and coronene collectively appear to have the required chromophores for features of the UIR bands, and the spectral shifts on an increase in the number of benzenoid rings point in the correct direction towards the positions of the UIR bands. Larger protonated peri‐condensed PAHs might thus be key species among the carriers of UIR bands.     

Electron-bombardment matrix isolation and PEPICO studies as complementary techniques in ion chemistry: an FTIR study of the decomposition of the vinyl fluoride cation

FTIR spectra have been obtained for matrices formed following electron bombardment of gas mixtures containing varying amounts of vinyl fluoride (VF) in Ar (1:400 to 1:25 600; VF/Ar). The major matrix‐isolated products are a π‐complex of HF/C₂H₂, fluoroacetylene (HC≡CF) and two isomers of C₂H₂F^?. These products correspond well with the products of photoionization of VF near 15.8 eV. These observations support the dominant mechanism of ionization in the EB‐MI environment as charge transfer of the substrate molecule to Ar^?+. Some differences are noted between the observed EB‐MI products and the results from PEPICO studies, primarily in that the EB‐MI products are observed as neutralized forms. The close correlation in EB‐MI and photoionization results allows the EB‐MI technique to be utilized as an ion structural analysis tool in complement to PEPICO studies, and allows the use of PEPICO studies to help predict and elucidate high‐pressure chemistry mechanisms through EB‐MI studies. The differences in the EB‐MI results and ions observed using the PEPICO technique are rationalized in terms of the differences in the experimental techniques. Using VF as the test system, reagent partial pressure conditions that best complement PEPICO studies are determined. Although the major results are observed for all VF partial pressures, dilute samples give rise to further ionization of the primary products, and more concentrated samples give rise to radical—radical reaction chemistry. As a result, a nominal range of 1:3200 (VF/Ar) is demonstrated to provide the best correlation with the gas‐phase PEPICO measurements. Copyright © 2011 John Wiley & Sons, Ltd.     

Biocompatible Triplex Ag@SiO2@mTiO2 Core–Shell Nanoparticles for Simultaneous Fluorescence‐SERS Bimodal Imaging and Drug Delivery

Herein, we report the synthesis of biocompatible triplex Ag@SiO₂@mTiO₂ core–shell nanoparticles (NPs) for simultaneous fluorescence‐surface‐enhanced Raman scattering (F‐SERS) bimodal imaging and drug delivery. Stable Raman signals were created by typical SERS tags that were composed of Ag NPs for optical enhancement, a reporter molecule of 4‐mercaptopyridine (4‐Mpy) for a spectroscopic signature, and a silica shell for protection. A further coating of mesoporous titania (mTiO₂) on the SERS tags offered high loading capacity for a fluorescence dye (flavin mononucleotide) and an anti‐cancer drug (doxorubicin (DOX)), thereby endowing the material with fluorescence‐imaging and therapeutic functions. The as‐prepared F‐SERS dots exhibited strong fluorescence when excited by light at 460 nm whilst a stable, characteristic 4‐Mpy SERS signal was detected when the excitation wavelength was changed to longer wavelength (632.8 nm), both in solution and after incorporation inside living cells. Their excellent biocompatibility was demonstrated by low cytotoxicity against MCF‐7 cells, even at a high concentration of 100 μg mL^?1. In vitro cell cytotoxicity confirmed that DOX‐loaded F‐SERS dots had a comparable or even greater therapeutic effect compared with the free drug, owing to the increased cell‐uptake, which was attributed to the possible endocytosis mechanism of the NPs. To the best of our knowledge, this is the first proof‐of‐concept investigation on a multifunctional nanomedicine that possessed a combined capacity for fast and multiplexed F‐SERS labeling as well as drug‐loading for cancer therapy.     

Raman and SERS study on ibuprofen metal complexes with biomedical interest

Ibuprofen is one of the most widely used non-steroidal anti-inflammatory drugs (NSAIDs), in which the carboxylate group is available for metal–ligand interactions. The most stable geometries for ibuprofen (in both its protonated and deprotonated forms) were identified by optimizations obtained by the unrestricted Density Functional Theory (DFT). Theoretical study of ibuprofen interacting with Ag colloid in solution, led to two (for the protonated form) and three (for the deprotonated form) different optimized geometries, corresponding to different interaction sites of the Ag₂ cluster. Frequency calculations were performed in the limit of the harmonic approximation, using the aug-cc-pVDZ basis set. Interpretation of the theoretical Raman spectra was performed by the Potential Energy Distribution (PED) analysis of the fundamental vibrations modes. Raman study on the solid Ibuprofen-metal complexes confirmed that Co²⁺ gives monodentate complexes, while Zn²⁺ adopts a bidentate coordination. SERS spectra of metal complexes, suggested that at ppm concentration, the formation of stable 2:1 metal complexes is excluded, while is more probable the formation of 1:1 adduct with bidentate binding on the carboxylic group. The metal reaches its total coordination shell by complexation of water molecules.     

四-(对-磺基苯基)卟啉二酸(H2+4TSPP) 分子聚集体的共振喇曼光谱研究

研究了四-(对-磺基苯基)卟啉二酸(H     

Polyaniline emeraldine base in N‐methyl‐2‐pyrrolidinone containing secondary amine additives: A rheological investigation of solutions

From a rheological study of emeraldine base (EB)/N‐methyl‐2‐pyrrolidinone (NMP)/2‐methyl‐aziridine (2MA) solutions, a correlation between the solution concentration and solution viscosity was found. We investigated the rheokinetic mechanism of the EB dissolution process and determined the reaction rate, activation energy, equilibrium constant, and Gibbs free energy (ΔG_o) for the complexation between 2MA and EB tetrameric molecules ({EB}). The low rate constant (～3.0 × 10^?4 mol^?2 L² min^?1 at 298 K) indicates that the process of EB/NMP/2MA solution formation is slow. The {EB} and 2MA molecules need approximately 76 kJ/mol energy to form the complexes, and this implies that stable bonds may need to be broken before the complexes can form. Therefore, increasing the temperature can accelerate solution formation. The equilibrium constant increases with temperature, and this indicates that EB · 2MA complexation is endothermic. A positive value of ΔG_o (5.26 kJ/mol) indicates that EB · 2MA complexation is a thermodynamically unfavorable reaction; therefore, the concentrated EB/NMP/2MA solutions eventually gel. Furthermore, we find that the activation energy of EB/NMP viscous flow is 80 kJ/mol, which is about 3–4 times the energy of ? N? H? hydrogen bonding. This suggests that at least three hydrogen bonds can form between two {EB} molecules, which might be responsible for the poor solubility of EB in organic solvents. The effects of the temperature, EB concentration, and 2MA:{EB} molar ratio on the gelation process have also been investigated. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 2702–2713, 2002     

黄曲霉素B1在银团簇表面吸附的表面增强拉曼光谱

采用密度泛函理论(DFT)的B3LYP方法和6-311g(d, p)(C, H, O)/LanL2DZ(Ag)基组, 优化得到黄曲霉素分子AFB₁与Ag小团簇形成的复合物AFB₁-Ag_n (n=2, 4, 6)的稳定结构, 并计算了三种复合物的表面增强拉曼光谱(SERS)和预共振拉曼光谱(SERRS), 与实验结果相一致. 计算结果显示: 三种复合物表面增强拉曼光谱中C＝O伸缩振动模的增强因子约为10²-10³, 是由于极化率改变引起的静化学增强. 根据含时密度泛函理论(TDDFT)方法计算得到的吸收光谱, 分别选择407.5、446.2和411.2 nm作为入射光, 计算三种复合物的共振拉曼光谱, 发现在SERRS光谱中, Ag―O伸缩振动的增强因子达到10⁴量级, 主要是由电荷转移产生的共振增强引起的.     

SERS and FDTD simulation of gold nanoparticles grafted on germanium wafer via galvanic displacement

Uniform and dense Au nanoparticles grown on Ge (Au/Ge) were fabricated by a facile galvanic displacement method and employed as surface‐enhanced Raman scattering (SERS) substrates. The substrates exhibited excellent reproducibility in the detection of rhodamine 6G aqueous solution with a relative standard deviation of <20%. The substrate showed a high Raman enhancement factor of 3.44 × 10⁶. This superior SERS sensitivity was numerical confirmed by the three‐dimensional finite‐difference time‐domain method, which demonstrated a stronger electric field intensity (|E/E₀|²) distribution around the Au nanoparticles grown on Ge. This facile and low‐cost prepared Au/Ge substrate with high SERS sensitivity and reproducibility might have potential applications in monitoring in situ reaction in aqueous solution. Copyright © 2014 John Wiley & Sons, Ltd.     

L‐Argininium phosphite – a new candidate for NLO materials

In order to investigate the possibility of salt formation in the L‐Arg–H₃PO₃–H₂O system, single crystals of L‐argininium phosphite, C₆H₁₅N₄O₂⁺·H₂PO₃⁻, were prepared by evaporation of an aqueous solution containing equimolar quantities of L‐arginine and phosphorous acid. The asymmetric unit contains one L‐argininium(+) cation and one phosphite [HPO₂(OH)]⁻ anion. The phosphite anions form chains parallel to [010] by O—H...O hydrogen bonding, with an O...O distance of 2.630 (3) Å. The protonated amine and guanidyl groups of the L‐argininium(+) cations form N—H...O hydrogen bonds with the carboxylate groups and anions. The IR and Raman spectra are discussed in relation to the crystal structure. The salt displays nonlinear optical (NLO) properties. Another salt was obtained from a solution with a 1:2 molar ratio of components, but was characterized by vibrational spectra only.