Transparent Gold Electrode Research Articles

Flexible and transparent gold network electrodes on fluorinated graphene

Flexible, transparent gold electrodes on fluorinated graphene achieve 80.2% transparency, 1.66 Ω □−1 sheet resistance, and excellent durability under bending.

Fabrication of Translucid Gold‐Nanocellulose Electrodes and their Potential Application as Hydrogen Peroxide Sensor

AbstractIn this work, we describe the fabrication of a transparent gold electrode based on nanocellulose. The electrode was prepared via electron beam evaporation of gold onto nanocellulose films previously spread over a glass slip. Electrodes with different thickness of Au was fabricated, and the material's optical, morphological and electrical properties were assessed. Finally, as a proof of concept, a possible application of this electrode in hydrogen peroxide sensing was performed. The results show that a thin layer of gold on a nanocellulose translucid film allows obtaining a conductive transparent surface that could be used to design a transparent electrode.

Electrodeposition and Screening of Photoelectrochemical Activity in Conjugated Polymers Using Scanning Electrochemical Cell Microscopy.

A number of renewable energy systems require an understanding and correlation of material properties and photoelectrochemical activity on the micro to nanoscale. Among these, conducting polymer electrodes continue to be important materials. In this contribution, an ultrasensitive scanning electrochemical cell microscopy (SECCM) platform is used to electrodeposit microscale thin films of poly(3-hexylthiophene) (P3HT) on an optically transparent gold electrode and to correlate the morphology (film thickness and structural order) with photoactivity. The electrochemical growth of P3HT begins with a thin ordered film up to 10 nm thick, after which a second more disordered film is deposited, as revealed by micro-Raman spectroscopy. A decrease in photoactivity for the thicker films, measured in situ immediately following film deposition, is attributed to an increase in bulk film disorder that limits charge transport. Higher resolution ex situ SECCM phototransient measurements, using a smaller diameter probe, show local variations in photoactivity within a given deposit. Even after aging, thinner, more ordered regions within a deposit exhibit sustained enhanced photocurrent densities compared to areas where the film is thicker and more disordered. The platform opens up new possibilities for high-throughput combinatorial correlation studies, by allowing materials fabrication and high spatial resolution probing of processes in photoelectrochemical materials.

A versatile lab-on-a-chip tool for modeling biological barriers

Models of biological barriers are important to study physiological functions, transport mechanisms, drug delivery and pathologies. However, there are only a few integrated biochips which are able to monitor several of the crucial parameters of cell-culture-based barrier models. The aim of this study was to design and manufacture a simple but versatile device, which allows a complex investigation of barrier functions. The following functions and measurements are enabled simultaneously: co-culture of 2 or 3 types of cells; flow of culture medium; visualization of the entire cell layer by microscopy; real-time transcellular electrical resistance monitoring; permeability measurements. To this end, a poly(dimethylsiloxane)-based biochip with integrated transparent gold electrodes and with a possibility to connect to a peristaltic pump was built. Unlike previous systems, the structure of the device allowed a constant visual observation of cell growth over the whole membrane surface. Morphological characterization of the layers was also accomplished by immunohistochemical staining. The chip was applied to monitor and characterize models of the intestinal and lung epithelial barriers, and the blood–brain barrier. The models were established using human Caco-2 intestinal and A549 lung epithelial cell lines, hCMEC/D3 human brain endothelial cell line and primary rat brain endothelial cells co-cultured with primary astrocytes and brain pericytes. This triple primary co-culture blood–brain barrier model was assembled on a lab-on-a-chip device and investigated under fluid flow for the first time. Such a versatile tool is expected to facilitate the kinetic investigation of various biological barriers.

Hole-injection from a polar mono-molecular layer derivatised ultra-thin gold electrode into a triphenylamine derivative

This Letter, reports the hole-injection characteristics of an ultra-thin, transparent gold electrode derivatized with a thiolate polar monolayer into the amorphous molecular semiconductor, N, N′-bis(3-methylphenyl)- N, N′diphenyl-1,1′biphenyl- 4,4′-diamine (TPD). Thermionic emission with image force lowering gives an excellent description of the injection mechanism over a large range of temperatures and electric field strengths, yielding a zero field Schottky barrier height of ∼0.4 eV. This study demonstrates that derivatizing the surface of this novel gold electrode with a 4-nitrophenylthiolate monomolecular layer is an effective means of circumventing the abrupt negative vacuum level shift, which forms when TPD is thermally deposited onto gold electrodes.

Study of polyaniline films degradation by thin-layer bidimensional spectroelectrochemistry

Degradation of polyaniline films electrodeposited on optically transparent gold electrodes has been followed by thin-layer bidimensional spectroelectrochemistry. The influence of the anodic potential reached during multiple potential scans has been assessed. Correlation of changes in the spectral signals in normal and parallel arrangement has enabled identifying species of different nature, both soluble and insoluble, electroactive and inert, during the degradation of the polymer film. The three bidimensional spectroelectrochemistry signals have demonstrated the occurrence of different types of degradation processes depending on the applied potential, ranging from the simple release of oligomers and hydrolysis products retained in the film during electropolymerization to more dramatic modifications of the film.

A robust ultrathin, transparent gold electrode tailored for hole injection into organic light-emitting diodes

A viable alternative to the problematic indium tin oxide (ITO) glass substrates invariably employed as the anode in organic light-emitting diodes is reported; namely ultrathin gold electrodes supported on glass. The key element to the successful fabrication of these electrodes is the pre-treatment of the glass substrate with the adhesion promoter 3-mercaptopropyl(methyl)dimethoxysilane prior to gold thermal deposition. The resulting films are exceptionally robust and exhibit high transparency over the visible spectrum combined with very low sheet resistance. Unlike ITO glass, these electrodes are chemically well defined and are fabricated at room temperature with no post-deposition annealing.

Action spectra of the photopotential generation for pigment and dye solutions in nematic liquid crystals located in the electrochemical cell

The method of measurements of the action spectra of photopotential generation using a modulated acting light beam was elaborated and applied to two systems: the solutions of stilbazolium merocyanines and to the mixture of chlorophyll a and luteine. Both types of samples were dissolved in nematic liquid crystal and located either between two semiconducting electrodes, or between a transparent gold electrode and a semiconducting electrode. By changing the frequency of light modulation or the phase shift between a modulated light beam and a measured photopotential signal, information about the kinetics of photopotential generation is obtained. The free base and protonated merocyanine forms exhibit different kinetics of potential generation. The amplitude of the photopotential of the chlorophyll and luteine mixture is higher than the sum of the amplitudes of the photopotential of these pigments located in separated cells. In a cell with two semiconducting electrodes, the light gradient (e.g., different illumination of front and back electrodes due to light absorption) plays an important role in photopotential generation.

Spectroelectrochemical characterization of ultra-thin films formed by electropolymerization of phenothiazine derivatives on transparent gold electrodes

Transparent gold electrodes covered with an ultra-thin polyphenothiazine film layer have been obtained by electropolymerization of the monomeric parent compounds, Methylene Blue, Methylene Green and Azur A, under alkaline pH conditions. The electrochemical behaviour of the polymers immobilized on the electrode surface has been characterized by UV-visible difference spectroelectrochemistry. A study of the dependence of the oxidation state of the surface redox species with the applied potential of any of the different polymer layers immobilized on the electrode surface showed one rather irreversible redox process, at potentials shifted towards 100–120 mV more positive values than those obtained for the monomer in solution. The spectroelectrochemical curves, obtained from the absorbance changes observed at different applied potentials, showed a hysteresis in the oxidation process, as well as the loss of some electroactive material from the electrode surface during the reduction process for all polymers studied. For poly-Methylene Blue, a shift of the redox potential towards more negative values coupled with an increase in the irreversibility of the redox process at increasingly higher pH values has been observed. The simultaneously obtained UV-visible difference spectra of the different films resembled those of the solubilized monomers. However, the spectra of the polymers showed a shift of the main visible maximum towards 50–80 nm shorter wavelengths, depending on the monomer studied.

Spectroelectrochemical detection of phenothiazine and phenoxazine derivatives covalently bound to self-assembled cystamine monolayers

Abstract The phenothiazine derivatives, Toluidine Blue O and Azur A, and the phenoxazine derivative Nile Blue were bound covalently to self-assembled cystamine monolayers chemisorbed on gold electrodes by derivatization of the surface amino groups with two different bifunctional spacers: terephthaloyl chloride and 1,6-hexamethylene-diisocyanate. The formation of the amido- and urea-derivatives of the parent compounds after covalent immobilization induces a shift of their redox potentials towards more positive values which can easily be detected by cyclic voltammetry. UV-Vis difference spectroelectrochemistry has been used to characterize the electroactive species immobilized onto transparent gold electrode surfaces in both oxidation states. In every case, the oxidized-minus-reduced (and reduced-minus-oxidized) difference spectra of the immobilized redox species show a shift of the UV maxima towards longer wavelengths and a shift of the Vis maximum towards shorter wavelengths when compared with their parent compounds. Each redox species showed different optical characteristics depending on the spacer used for immobilization. For phenothiazine derivatives immobilized with 1,6-hexamethylene di-isocyanate the total surface coverages obtained by optical methods were close to those obtained by cyclic voltammetry. However, for the same derivatives immobilized with terephthaloyl chloride, and for Nile Blue, independently of the spacer used, higher surface coverages were found by optical methods than by cyclic voltammetry.

On the Electrical Properties of Nearly Stoichiometric Rutile Single Crystals (TiO2)

AbstractMeasurements are made of the current‐voltage‐time characteristics of etched, and unetched, TiO2 single crystals, with and without illumination through a transparent gold electrode. These results allow certain deductions to be made concerning the relation between space‐charge‐limited currents, polarization phenomena and the conductivity changes inducted by the applied field.It is shown that the polarization phenomena and observed I ∼ V2 characteristics must be ascribed to effects in sub‐surface regions. A small amount of electrolytic conductivity together with certain reactions with the electrode are considered to be the origin of the conductivity changes.