Silver Electrode Surface Research Articles

Surface modification of printed silver electrodes for efficient carrier injection in organic thin-film transistors

The modification of printed silver electrode surfaces for use as the bottom-contact electrodes of organic thin-film transistors (OTFTs) is reported. Printed silver electrodes fabricated using the surface photoreactive nanometal printing (SuPR-NaP) technique are inevitably covered with an inert surface layer of alkylamines that is originally used for encapsulation of the silver nanoparticles (AgNPs). However, it may act as a built-in protective layer against carrier injections. We demonstrate that a simple vapor exposure method is sufficient for converting the protective layer into a layer that assists carrier injection. As modifiers, we used various types of fluorinated benzenethiols that exhibit a stronger coordination with the silver surfaces than the alkylamimes. We detected the chemical conversion from alkylamine encapsulation to thiol coordination by surface enhanced Raman spectroscopy (SERS) and evaluated the improvement in the carrier injection using a transfer length method (TLM) for the OTFTs. Among the modifiers, the pentafluorobenzenethiol (PFBT) treatment significantly improves the device performance and stability of the OTFTs.

(Invited) Liquid Phase Ion-Gun Technique for Degradation and Evaluation of Oxide Films

Halide ions in environments destabilize oxide films on materials and lead to a local corrosion of the material. In order to investigate a quantitative effect of halide ions on oxide degradation, an electrochemical technique with a concentrating method of halide ions on the oxide in an experimental setup is necessary. Liquid phase ion-gun (LPIG), in which silver halide layer on a silver microelectrode is reduced in liquid phase, is one of the beneficial techniques to concentrate halide ions the vicinity of the material surface. Fushimi and Seo developed an LPIG as a chloride ion-generator and successfully applied in boric acid-borate buffers to degrade passive film on pure iron locally and to induce the local corrosion [1, 2]. Degradation reaction of the film was classified into three processes; depassivation induction, film depassivation, and corrosion propagation or repassivation, from electric charges consumed by both LPIG microelectrode and specimen electrode. Since an electric charge consumed on the microelectrode for the generation of chloride ions during the induction process corresponds to the amount of chloride ions needed for the degradation of passive film, the stability of passive films on different crystallographic grains were also evaluated. LPIG was also combined with electrochemical quartz crystal microbalance and used to investigate local corrosion of copper [3]. Lee and Fushimi have developed another type of LPIG, in which silver sulfide layer on the silver microelectrode is reduced to generate sulfur species, and applied to sulfide surface of silver electrode [4] and type 316L [5], 304, 430 and 443 [6] stainless steels. In this paper, the beneficial features of LPIG technique for investigating the initiation of local corrosion on iron-based materials are reviewed. The quantitative analyses for the halide ions generated from LPIG microelectrode will also be discussed.

Theoretical study of normal Raman spectra and SERS of benzyl chloride and benzyl radical on silver electrodes

Electrochemical surface‐enhanced Raman spectroscopy has been used to characterize adsorbed species widely but rarely to reaction intermediates on electrodes. In previous studies, the observed surface‐enhanced Raman spectroscopy signals were proposed from benzyl species due to the electrochemical reduction of benzyl chloride on silver electrode surfaces. In this work, we reinvestigated the vibrational assignments of benzyl chloride and benzyl radical as the reaction intermediate. On the basis of density functional theory calculations and normal mode analysis, our systematic results provide more reasonable new assignments for both surface species. Further, we investigated adsorption configurations, binding energies, and vibrational frequency shifts of benzyl radical interacting with silver. Our calculated results show that the wagging vibration displays significant vibrational frequency shift, strong coupling with some intramolecular modes in the phenyl ring, and significant changes in intensity of Raman signals. The study also provides absolute Raman intensity in benzyl halides and discusses the enhancement effect mainly due to the binding interaction with respect to free benzyl radical. Copyright © 2016 John Wiley & Sons, Ltd.

Theoretical Study on Electroreduction of p-Nitrothiophenol on Silver and Gold Electrode Surfaces

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 ...

增强碳纳米管场发射性能的沟槽形冷阴极制作

Based on sintering process and screen printing technique,a novel groove shape cold cathode was developed.The black insulation slurry was sintered to fabricate the bottom insulation layer,in which a gradient surface existed.The silver slurry was screen-printed on the bar electrode. With the baking and sintering process in proper sequence,the silver electrode was formed.Using fine sandpaper,aproper polishing process for silver electrode was conducted,so a smooth electrode surface was obtained.Due to the special silver electrode shape,a larger field enhancement factor was achieved easily.Carbon nanotubes were prepared on the silver electrode to form the field emitters. The dense carbon nanotube layer would cover the silver electrode surface completely.Owing to the special edge field enhancing effect,lots of electrons would be emitted from the carbon nanotube.The top insulation layer was used to restrain the side electron emission of carbon nanotube.With the groove shape cold cathode,a triode field emission display was fabricated,which exhibited good field emission properties and better luminescence image uniformity.Comparing with the common cold cathode field emission display,the turn-on electric field could be reduced from 1.86 V/μm to1.78V/μm,the maximum field emission current had been increased from 1 537μA to 2 863μA,and the maximum luminescence image brightness would be enhanced from 1 386cd/m2 to 1 865cd/m2.The developed fabrication technology had a potential practical application in field emission display.

Environmental Monitoring of Acetic Acid Gas by Thin Film Polyaniline Sensor

The acetic acid gas, as a kind of organic pollutants, can cause severe damage to both people and materials, and has received much attention as a problem. In this paper, a QCM sensor coated with the polyaniline film was employed as a gas sensor to detect the content of the acetic acid gas. The polyaniline film was electrochemical polymerized in situ on the silver electrode surface of quartz crystal microbalance (QCM) sensor and employed as sensing film for detection of acetic acid gas. Responses of the QCM sensors coated with the polyaniline film to different concentrations of the acetic acid gas as a function of time was presented. And the frequency shifts of QCM showed a linear correlation of the concentration of acetic acid gas. The result of our experiment fully indicated that the QCM sensor with the polyaniline film appear to respond effectively and sensitively to the acetic acid gas within the range of experimental concentrations. Such sensor will have potential application in our living environment for real-time monitoring.

Numerical simulation and experiment in the systems of labile complexes of metals. Silver reduction from the thiourea electrolyte

Voltammograms of silver reduction from complex thiourea electrolytes with the ligand to metal concentration ratio varied from 1 to 50 were measured on the freshly prepared surface of silver electrode. The results were analyzed using the numerical model of this electrode process which takes into account homogeneous chemical reactions proceeding in solution, diffusion–migration transfer of the species present in solution, and electrode reactions participated by electroactive components of the electrolyte. We estimated the values of standard exchange current density for partial electrode reactions in which silver complexes with different number of ligands can take part. The highest electrochemical activity is exhibited in solutions with the low concentration of complex-forming agent – by silver aqua complexes, while in solutions with high thiourea concentration – by silver complexes with one ligand. It was found that kinetic hindrances to discharge of the thiourea silver complexes unlikely to be due to the adsorption of thiourea molecules blocking the growth sites or to the adsorption of complex silver ions. The results admit interpretation of the mechanism of electrode process either from the viewpoint of simultaneous discharge of all the complex silver ions present or from the viewpoint of discharge of silver complex with one ligand in combination with rapid chemical reactions of dissociation of other, non-discharging silver complexes.

SERS and in situ SERS spectroelectrochemical investigations of serotonin monolayers at a silver electrode

Surface enhanced Raman scattering (SERS) technique was used to observe the adsorption structure of serotonin (5-hydroxytryptamine, 5-HT) monolayers formed on silver electrode surface at pH 11 and also by the aid of density functional theory (DFT). The SERS spectrum implied that monolayers of 5-HT could be self-assembled on the silver surface through O10 and N6 atoms and the molecular plane should be tilted on the surface. In situ electrochemical SERS experiment was performed in 0.1molL−1 KCl solution to investigate the stability of the 5-HT monolayers on the silver electrode surface. It could be found that 5-HT monolayers on silver surface experienced the changes of adsorption fashions as the potential shifting to a more negative direction prior to complete detachment from the silver surface.

Adsorption of acridine on silver electrode: SERS spectra potential dependence as a probe of adsorbate state

This work investigates acridine adsorption on the silver electrode surface. The dependence of the acridine SERS spectra on the electrode potential proved to be quite different for azaheterocycle molecules, while the pH effect as expected. The changes in the acridine SERS spectrum caused by the double electric layer (DEL) rearrangement can be explained by sorption/desorption rather than the adsorbate molecule reorientation. The presence of chloride anions close to the silver surface is important not only for the SERS-active properties but for the formation of the stabilised surface complexes of the protonated acridine as well.

The giant Raman scattering absolute cross-section for light scattered by the silver-adatom-metal complexes at silver electrodes in silver perchlorate aqueous solutions

The value of giant Raman scattering absolute cross-section for silver adatoms (σad = 3.1 × 10−27 cm2/adatom) is determined by the measuring of the background intensity in the giant Raman scattering spectra at silver electrode surfaces in silver perchlorate solutions. With taking into consideration of the sulfate ion specific adsorption, the improved value σad = 1.9 × 10−27 cm2/adatom is determined in silver sulfate solutions. The closeness of the values in the two solutions allows concluding that the weakly adsorbing anions affect but negligibly the silver adatom properties; however, in compliance with the earlier data obtained in sulfate solutions, they affect markedly the kinetics of the adatom migration over electrode surface.

Screen-printed Electrochemical Sensors and Biosensors for Monitoring Metal Pollutants

The present review (with 231 references) focuses on developments made in the area of screen -printed biosensors and sensors for the determination of metal ions in industrial, environmental and biomedical applications. The year 2012 represents the twentieth anniversary of the first reported application of screen-printed electrodes for the determination of metal ions. Focus is placed o n fabrication techniques, operating details and performance characteristics for the selected applications. The greater proportion of articles have utilised the technique of stripping voltammetry, gaining detection limits in the low ng/mL (ppb) region. An increasing percentage of these have explored bismuth as an alternative to mercury for the modification of the carbon electrode surface. However, a steady number of applications have shown the possibility of utilising the unmodified screen-printed carbon,gold or silver electrode surface. More recently the alternative approach of electrochemical biosensors has become a growing area. The majority of these have exploited the inhabitation metal ions exhibit on the enzyme activity of urease, acetylcholineste rase and glucose oxidase gaining detection limits in the sub µg/mL region, however recent applications utilising thiol-functionalised oligonucleotides have been shown the possibility of gaining detection limits as low as 120 ng/L for Hg

Polyaniline-Modified Quartz Crystal Microbalance Sensor for Detection of Formic Acid Gas

A polyaniline-modified quartz crystal microbalance (QCM) sensor was obtained through immobilizing the polyaniline film on the silver electrode surface of quartz crystal resonator by an electrochemical method. The sensor was studied for detecting the formic acid gas of different concentrations, and the results showed that the resonant frequency of QCM decreased quickly in the beginning and tended to be constant in the end when exposed to formic acid gas. The frequency shifts decreased faster as the concentration of formic acid gas increased. And the frequency shifts of the QCM sensors were found to be linearly related to the concentration of formic acid gas, which might be used to estimate the concentration level of the formic acid gas within the range of experimental concentrations. The result of on-line monitoring test fully indicated that the QCM sensor responded effectively to the increasing concentration of formic acid and had important practical significance and broad application prospect in real-time detection of antique conservation environment in the museum.

Surface-enhanced Raman spectroscopy of 4-tert -butylpyridine on a silver electrode

We report the observation of large surface-enhanced Raman scattering (SERS) (106) for 4-tert-butylpyridine molecules adsorbed on a silver electrode surface in an electrochemical cell with electrode potential set at − 0.5 V. A decrease in electrode potential to − 0.3 V was accompanied by a decrease in relative intensities of the vibrational modes. However, there were no changes in vibrational wavenumbers. Comparison of both normal solution Raman and SERS spectra shows very large enhancement of the intensities of a1, a2, and b2 modes at laser excitation of 488 nm. Enhancement of the non-totally symmetric modes indicates the presence of charge transfer as a contributor to the enhancement. Copyright © 2011 John Wiley & Sons, Ltd.

Structure of Monolayers Formed from Neurotensin and Its Single-Site Mutants: Vibrational Spectroscopic Studies

The human, pig, and frog neurotensins and four single-site mutants of human neurotensin (NT), having the following modifications, [Gln(4)]NT, [Trp(11)]NT, [D-Trp(11)]NT, and [D-Tyr(11)]NT, were immobilized onto an electrochemically roughened silver electrode surface in an aqueous solution. The orientation of adsorbed molecules was determined from surface-enhanced Raman scattering (SERS) measurements. A comparison was made between these structures to determine how the change upon the mutation of the neurotensin structure influences its adsorption properties. The SERS patterns were correlated with the contribution of the structural components of the aforementioned peptides to the ability to interact with the NTR1 G-protein receptor. Briefly, the SERS spectra revealed that the substitution of native amino acids in investigated peptides influenced slightly their adsorption state on an electrochemically roughened silver surface. Thus, human, pig, and frog neurotensins and [Gln(4)]NT and [D-Tyr(11)]NT tended to adsorb to the surface via the tyrosine ring, the oxygen atom of the deprotonated phenol group of Tyr(11), and the -CH(2)- unit(s), most probably of Tyr(11), Arg(9), and/or Leu(13). The observed changes in the enhancement of the deprotonated Tyr residue SERS signals indicated a further parallel orientation of a phenol-O bond with regard to the silver surface normal for pig NT, [Gln(4)]NT, and [D-Tyr(11)]NT, whereas the orientation was slightly tilted for human and frog NT. In the case of [Trp(11)]NT and [D-Trp(11)]NT, the formation of a peptide/Ag complex was confirmed by strong SERS bands involving the phenyl co-ring of Trp(11)/d-Trp(11) and -CH(2)- vibrations and the tilted and flat orientations of the two compounds with respect to the surface substrate. The spectral features were accompanied by a SERS signal caused by vibrations of the carboxyl group of C-terminal Leu(13) and the guanidine group of Arg(9). Reported changes in SERS spectra of L and D isomers were fully supported by generalized two-dimensional correlation analysis. Additionally, a combination of mutation-labeling and vibrational spectroscopy (Fourier-transform Raman and absorption infrared) was used to investigate the possible peptide conformations and environments of the tyrosine residues.

Surface-enhanced Raman scattering (SERS) spectroscopy of enantiomeric and racemic methionine on a silver electrode-evidence for chiral discrimination in interactions between adsorbed molecules

The adsorption of enantiomeric and racemic forms of methionine on the silver electrode surface was studied by surface–enhanced Raman scattering spectroscopy (SERS) as a function of pH value of the solution and the electrode potential, as well. Results for d–methionine were analogous to these for l-methionine, as expected. However, in the case of racemic mixture of d,l-methionine in acidic pH the spectral effects were different than those observed for monolayers built of pure enantiomer ( d or l). This effect was discussed in terms of interplay between surface-molecule and intermolecular interactions between adjacent methionine molecules at the Ag surface.

Research on the Emission Property of Cold Cathode Emitter with Enhanced Bar Electrode in a FED Panel

Using carbon nanotube (CNT) as cathode material, the field emission display (FED) panel with enhanced bar electrode was fabricated. With the photolithography process, the indium tin oxide (ITO) film was divided to form the cathode ITO electrode. The printed silver slurry was sintered to act as the cathode silver electrode, which was prepared on the cathode ITO electrode surface. The insulation layer was also fabricated on the cathode plate. The CNT paste was screen-printed on the surface of cathode ITO electrode and cathode silver electrode to form the field emitter. The detailed fabrication process of FED panel was given, and the sealed FED panel showed better field emission properties. Because of the enhanced bar electrode, the large field emission current was obtained.

Synthesis and kinetics of growth of metal nanoparticles inside ion-exchange polymers

Copper and silver nanoparticles have been obtained by means of saturation of a sulfostyrene-divinylbenzene cation-exchange polymer with metal ions and their subsequent chemical reduction. This procedure was repeated several times up to formation of a long-range conducting network (percolating cluster). Another system under study was an ensemble of Ag nanoparticles of various sizes on the silver electrode surface obtained by reduction of anodically formed layers of silver oxide. Recrystallization of deposited metal crystals inside the polymer matrix in contact with metal-ion containing solution is very slow for electrically separated particles. Formation of the electric network results in an enormous acceleration of this process via electron-ion mechanism, with growth of the average particle size, so that their potential will approach that of the compact metal with time. The initial period of the particle growth is well described by the parabolic law (Burke and Turnbull). The values of the particle-growth coefficient in this law, k, are drastically different for particles inside the matrix and on the electrode surface. Particle-to-particle electron transfer is impeded by insulating areas inside the polymer matrix. Besides, ionogenic centers of the matrix restrict the mobility of metal cations, thus slowing down the ion transfer within the recrystallization circuit. These observations have allowed us to establish the conditions resulting in long-term stabilization of metal nanoparticles inside the ion-exchange matrix with respect to their recrystallization.

Layer-by-layer assembled molecularly imprinted polymer modified silver electrode for enantioselective detection of d- and l-thyroxine

The present work describes a new, simple, and easy method for the generation of stable molecularly imprinted sites in polymeric film, combining self-assembled monolayer and Layer-by-layer approaches through thermal cross-linking of the layered structures, onto the surface of silver electrode. Modified silver electrodes demonstrate enantiodifferentiation and sensitive (detection limits 0.0060 ng mL −1 for l- and 0.0062 for d-thyroxine) determination of d- and l-thyroxine with the help of differential pulse anodic stripping voltammetric technique. The binding kinetics of thyroxine was explored using anodic stripping cyclic voltammetry and chronocoulometry. The sensor was also validated for d- and l-thyroxine determinations in biological and pharmaceutical samples.

ChemInform Abstract: Charge Shift of Adsorbed Pyridazine Molecules to the Silver Electrode Surface at Various Applied Voltages as Interpreted from the Surface Enhanced Raman Intensities.

Abstract An algorithm which enables one to calculate the bond polarizability derivatives from the surface enhanced Raman (SER) intensities has been employed to study the adsorption of pyridazine molecules on the silver electrode. It is inferred from the bond polarizability derivatives that as the applied voltage varies from −0.4 V to −0.6 V the electron charge in the bonding orbital n 1 + n 2 , formed from the lone pair orbitals n 1 and n 2 of the two adjacent nitrogen atoms, shifts towards the silver electrode surface, whereas from −0.6 V to −0.8 V it is the charge in the antibonding orbital n 1 − n 2 that shifts towards the electrode surface. The corresponding SER frequencies of those modes involving the stretch motion of the NN bond initially decrease and then increase. At the same time a charge shift occurs in the benzene-like ring which obeys the bond conjugate rule.

SERS of β‐Thioglucose Adsorbed on Nanostructured Silver Electrodes

Highly ordered microporous films of silver-containing regular arrays of spherical pores of differing diameters were prepared by electrochemical deposition into the interstitial spaces of a template formed by nanosphere lithography. These nanostructured electrodes in conjunction with a Raman microprobe spectrometer were used to obtain surface-enhanced Raman spectra (SERS) of beta-thioglucose (beta-TG) under potential control. The SERS results were compared with SERS of beta-TG on an electrochemically roughened silver electrode surface. The bands in the experimental spectra were assigned to particular vibrations with the help of ab initio predictions of the spectra. The results of this study show that beta-TG self-assembled at a silver electrode forms a hydrophilic film that may be used in biomimetic research to enhance interactions between the electrode and the hydrophilic portion of a model membrane, and to prevent interactions of proteins inserted into this membrane with the metal surface. However, in contact with the aqueous electrolyte an anomerization reaction takes place and the beta-TG film is a mixture of the alpha- and beta-anomers of thioglucose. A partial oxidation of the self-assembled molecules was also observed. In addition, the orientation of the adsorbed molecules changes as a function of the applied potential.