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A simple but effective electrochemical route to functionalize graphene is demonstrated. Cyclic voltammetric sweeps are performed in 0.5 M H2SO4 aqueous solution on electrodes containing carbon cloth, graphene, and Nafion ionomer. With supply of ambient oxygen, the formation of hydroxyl radicals from the oxygen reduction reaction during CV cycles initiates the decomposition of Nafion ionomer that engenders oxygenated functional groups on the graphene surface. Raman analysis suggests a minor change for the graphene structure. Exploring various amounts of Nafion ionomer, we determine the optimized conditions for graphene functionalization. Contact angle is used to evaluate the effect of Nafion ionomer decomposition. X-ray photoelectron spectroscopy is employed to study relevant functional groups. Afterwards, nanoparticles of Pd9Ru are synthesized and impregnated on those functionalized graphene (FGN) via a wet chemical reflux process. X-ray diffraction patterns of the as-synthesized samples suggest successful formation of alloy without presence of individual Pd and Ru nanoparticles. Images from transmission electron microscope confirm the average size of 3-4 nm. Subsequently, the Pd9Ru/FGN undergoes Cu under potential deposition, followed by a galvanic displacement reaction to deposit a Pt monolayer on the Pd9Ru surface (Pd9Ru@Pt). Intensive experimental work is ongoing to investigate the electrochemical active surface area (ECSA) and electrocatalytic activities of Pd9Ru@Pt/FGN.

We demonstrate a facile approach to fabricate an electrocatalyst consisting of Au encapsulating a hollow carbon microsphere (HCMS@Au) for the detection of uric acid (UA), dopamine (DA), and ascorbic acid (AA). The HCMS@Au is obtained by the pyrolysis of polystyrene@polydopamine@Au (PS@PDA@Au) microspheres. Electrochemical methods including potentiostatic mode and pulse voltammetric scans are employed to identify relevant redox signals for UA, DA, and AA. The HCMS@Au reveals a lower detection limit for DA in the ambiance of AA and UA. We attribute the Au nanoparticles with high electric conductivity and uniform size that are distributed conformally on the hollow carbon microspheres for the enhanced detection sensitivity. The morphology and composition of HCMS@Au are analyzed by scanning electron microscope, transmission electron microscope, and energy dispersive spectroscope.

The detection of hydrogen peroxide (H2O2) is of practical importance due to its involvement in the functioning and signal transduction of living cells. Various electrochemical techniques have been explored using either enzymatic or non-enzymatic sensors. In particular, non-enzymatic biosensors have attracted considerable attention because of their impressive stability and reproducibility. In addition, they are less susceptible to environmental interferences. However, the primary drawback of non-enzymatic sensors is poor sensitivity and selectivity. Hence, we want to address this issue by fabricating Cu2O in an inverse opaline structure. Our process involves the preparation of Au inverse opals serving as a three-dimensional ordered macroporous conductive substrate that allows an excessive surface area and sufficient porosity for mass transport. The Cu2O is electrodeposited on the Au inverse opals for the detection of H2O2. Comprehensive electrochemical analysis and materials characterization are conducted and discussed.

Bio-stimulating electrodes are recognized to be one of the most critical components for implantable biomedical electronic devices. In order to activate neurons for therapeutic functions, a desirable bio-stimulating electrode requires specific attributes including a large amount charge storage and high charge injection capacity along with a low impedance at the operating frequency of the device. Among the many electrode materials studied to date, iridium oxide has emerged as an especially promising candidate with superior characteristics for charge storage, biocompatibility and chemical inertness. In this presentation, we describe our studies on the interrelationships between charge transfer and structural changes in IrO2. In-situ X-ray absorption spectroscopy was used to determine the changes occurring in the oxidation states of IrO2 during cyclic voltammetry (CV) scans. These results are correlated with the structural changes occurring as determined by X-ray diffraction. In addition, we carried out eQCM measurements to better identify the electrochemical reactions associated with the redox peaks generated by the CV scans. The results of this study lead to a much better understanding of the operation of iridium oxide as a bio-stimulating electrode.

We demonstrate a facile approach to deposit Pt/IrO2 composite films via a bipolar pulsing deposition technique in which the Pt ions are electrochemically reduced and the IrO2 colloids are electrophoretically deposited. The composite Pt/IrO2 films are subjected to both potential pulse and differential pulse voltammetry to detect the presence of dopamine (DA) and ascorbic acid (AA) for bio-sensing applications. In human’s body, a critical concentration of DA is used as an indicator for onset of Parkinson's disease. Unfortunately, the existence of AA would interfere with the detection of DA due to their similar oxidation potential. By fabricating a composite of Pt and IrO2, a lower detection limit with a minimized interference of DA and AA could be achieved. Electrochemical parameters relevant to the preparation of Pt/IrO2 films are optimized and the resulting morphology and composition are analyzed by SEM and EDS. The oxidation state of Pt and Ir are determined by XPS. The electrical resistance and electrochemical surface area of Pt/IrO2 films are recorded by impedance spectroscopy and electrochemical analysis.

Chitosan is considered to be a natural polymer for promising applications in drug delivery, wound dressing/healing, biocompatible coating, and tissue engineering. Since the chitosan is known for bio-compatibility, non-toxicity, anti-bacterial ability, and low cost, there has been increasing interest to leverage the unique characteristics of chitosan to fabricate bio-composites for specific bio-medical purposes. In this work, we demonstrate a facile synthetic approach to fabricate composite hydrogels consisting of chitosan, poly(3,4-ethylenedioxythiophene (PEDOT), and iridium oxide (IrO2) nanoparticles. Our synthesis step entails a potentiostatic mode that enables electrophoresis and water electrolysis simultaneously to produce free-standing conductive hydrogels with high porosity. Materials characterization of the as-synthesized composite hydrogels confirm reasonable electric conductivity and impressive anti-bacterial performance. In addition, structural and compositional analysis such as SEM, EDX, XPS, and Raman spectroscopy are conducted. From in-vitro tests of fibroblast cells, we observe that the application of electrical signals accelerates the growth rate, and the resulting current responses are contingent on the magnitude of cell proliferation. Our composite hydrogels combine both electrical stimulation and detection functionality, desirable attributes for potential use in wound healing application.

The highly sensitive detection of hydrogen peroxide (H2O2) is of practical importance due to its involvement in the biofunction and signal transduction of cells. Various electrochemical techniques have been explored and studied for its detection, which can be realized through either enzymatic or non-enzymatic sensors. Particularly, non-enzymatic biosensors have been in great demand because of their high stability, high reproducibility, and less susceptible to environmental factors compared to the enzyme-based approach. However, many of them display inferior sensitivity or poor selectivity. Hence, this work aims to develop a highly sensitive non-enzymatic biosensor through structural and compositional approaches. From a structural point of view, Au inverse opals are utilized as the sensor scaffold due to their intriguing porous structure. The spatial arrangement of these materials resembles a honeycomb structure, which provides a high specific surface area, efficient mass transport, and strong mechanical stability. In addition to the benefits brought by inverse opals, we further incorporate a composite coating based on Cu2O to decorate the scaffold surface. Through the combination of a well-ordered pore structure with additional functionalization by composite formation, a synergistic improvement could be realized. To fabricate such structural biosensors, an expedited self-assembly process exploiting electrophoresis technique is first adopted to produce a colloidal crystal template. Subsequent electrodeposition processes are performed to construct the Au inverse opals and relevant functional coatings. The sensing performance of these 3D sensors is then evaluated by the detection of H2O2 using cyclic voltammetric analysis. Their structural and compositional characterizations are conducted by SEM, EDX, XPS, and Raman spectroscopy.

The development of pH sensors is critical for a wide variety of fields including food safety, chemical synthesis, and biomedical devices. Among many materials explored for pH sensing purposes, the iridium oxide (IrO2) has attracted the most attention for its broad working temperature and pH range, as well as rapid response time and low electrical impedance. In addition, the IrO2 is chemically stable and demonstrates negligible susceptibility to redox interference. In this work, we demonstrate a formula that enables electroless deposition of IrO2 on a flexible polyimide substrate. Our formula involves the mixing of Ir3+ precursor with selective additives of complexing agent, pH adjuster, and oxidizing agent. The morphology and composition of IrO2 films are analyzed by SEM and EDS. The oxidation state of Ir in IrO2 films are determined by XPS and XAS. For pH-sensing characteristic, the potentiometric response as a function of pH value is obtained by an electrochemical workstation.

Three-dimensional ordered macroporous Ni films, known as Ni inverse opals, are fabricated via a template approach in which polystyrene (PS) microspheres (820 nm in diameter) are assembled in closely-packed colloidal crystals via a vertical electrophoresis process, followed by electroplating of Ni into the interstitial voids within the colloidal crystals and the selective removal of PS microspheres. To improve its mechanical strength, a conformal Ni-Co layer (45 ∼ 64 nm) is electrodeposited on the skeletons of the Ni inverse opals by cyclic voltammetry. After coating, from nano-indentation tests, the hardness and reduced elastic modulus are enhanced considerably (172 ∼ 220% for hardness; 72 ∼ 79% for reduced elastic modulus), as compared to those of pristine inverse opals. After an annealing treatment for the interdiffusion of Ni and Co, the sample reveals an even stronger hardness. X-ray diffraction patterns indicate that the finite thickness of the inverse opals skeletons induces preferential growth of the (111) plane. In short, a combined effect of solid solution alloying, thickening of inverse opals skeletons for greater load bearing, and a predominant (111) plane is responsible for the improved mechanical strength of the Ni inverse opals.

We explore dopamine (DA) and its mixtures with polyethylene glycol (PEG) or polyethylenimine (PEI) as an adhesion layer for bonding between Cu and SiO2. The DA is oxidized to form polydopamine (PDA) which deposits as aggregates on SiO2 surface with notable surface roughness. After mixing with PEG or PEI, the morphology of PDA aggregates is altered considerably. Electroless Cu deposition in a mild alkaline bath is employed to deposit Cu atop the adhesion layer. The Cu films reveal an fcc lattice with (111) preferred orientation and their thickness was around 650 nm. From measurements of four-point probe, breaking strength, and tape-peeling tests, the PDA/PEG mixture reveals impressive performance serving as a strong adhesive for robust Cu bonding. We attribute the unique adhesive ability of PDA/PEG to the hydrogen bonds established between the catechol and amine groups of DA with PEG that renders desirable film formation on the SiO2 surface for optimized interaction between Cu and SiO2.

Fabrication of graphene was demonstrated by electrochemical exfoliation of graphite in an ammonium hydroxide solution. The processing parameter of applied voltage was optimized to accomplish graphene productivity and desired chemical composition. Images from the atomic force microscopy showed graphene sheets with lateral sizes of several hundred nanometers. Images from the transmission electron microscopy indicated the existence of stacked graphene sheets with thickness of a few graphene layers. Raman spectroscopy confirmed variation of as-synthesized graphene and bulk graphite. X-ray photoemission spectroscopy suggested the formation of graphene oxide at large voltage.

aDepartment of Chemical Engineering, National Chung Cheng University, Chia-Yi 62102, Taiwan bDepartment of Chemical Engineering, National Tsing Hua University, Hsin-Chu 30013, Taiwan cDepartment of Materials Science and Engineering, National Chiao Tung University, Hsin-Chu 300, Taiwan dGraduate Institute of Opto-Mechatronics, National Chung Cheng University, Chia-Yi 62102, Taiwan eAdvanced Institute of Manufacturing with High-Tech Innovations, National Chung Cheng University, Chia-Yi 62102, Taiwan

The ordered arrangement of meso/macropores in the inverse opaline structure could be beneficial to enhance the performance for several applications, such as sensing, electrocatalysis and filtration. One of the critical concerns for its practical use could be regarded to the mechanical properties of this structured material. We had successfully demonstrated the fabrication of larger-area Nickel inverse opaline films through a facile electrochemical route. In this work, a pulse voltage electrophoretic deposition or CV electro-polymerization was subsequently applied to a metallic inverse opaline film as working electrode. Several experimental parameters, including the recipes for deposition bath and the pulse programs, were explored and studied. With optimized experimental parameters, a conformal coating of oxide or polymeric materials on the skeleton of inverse opals could be successfully achieved. Their mechanical properties were evaluated by nanoindentation and microtensile test. Other structural and compositional characterization were conducted by SEM, EDS, XRD, and XPS analysis.

Metallization on patterned or insulating substrates possesses significant importance in various applications. However, there usually exhibit poor interfacial adhesion between metals and oxides/polymers. This is one of the major obstacles for this process in practical applications, such as integrated circuits and printed circuit board for wearable devices. In this research, we had successfully used dopamine as an adhesion layer in the heterogeneous interface, such as SiO2/Cu and polymer/Cu interfaces. The use of this reagent could act as both a reductant and interfacial adhesive. We performed SEM, TEM and EDS analysis to confirm the film structure and their compositions. Peeling test were also conducted for evaluating the enhancement of film adhesion with the introduction of dopamine. We expected this technique could be to apply in the thin film process in the near future.

We report a facile electrochemical method to produce functional groups on the carbon surface in which multiple cyclic voltammetric (CV) sweeps are imposed in 0.5 M H2SO4 electrolyte on the samples containing carbon cloth, Vulcan XC72R, and Nafion ionomer. With supply of ambient O2, the generation of radicals from the oxygen reduction and Nafion ionomer degradation enables an accelerated formation of oxygenated functional groups on the carbon surface. Raman analysis reveals structural variation for the carbon electrodes after CV modifications. X-ray photoelectron spectroscopy confirms the alteration of carbon structure in conjunction with notable increase of oxygenated groups and reduction in fluorine amount. The functionalized electrodes allow a 250% increment for PtRu electrodeposition as compared to the reference sample. We carry out electrochemical measurements on methanol electro-oxidation for the PtRu samples. The functionalized electrode demonstrates significant improvement in apparent current density and mass activity as opposed to the reference sample.

A tri-layered ceramic structure was prepared by consecutive electrophoretic depositions of anode, electrolyte, and cathode, followed by a single sintering process to fabricate solid oxide fuel cells. Materials characterizations including SEM and XRD were carried out along with electrochemical analysis.

Synthesis of various sizes particulate Ag supported on carbon nanocapsules (CNCs) were conducted in typical impregnation and wet chemical approach for physical characterization and electrochemical analysis in alkaline electrolyte. XRD of the as-synthesized powders indicated Ag in FCC phase. In i-V polarizations, the nano Ag/CNCs derived wet chemical route exhibited much enhanced oxygen reduction reaction capabilities than those of Ag/CNCs from impregnation method. Similar behaviors were recorded in galvanostatic discharging measurements between 10 and 200 mA/cm2.

A galvanostatic pulse electrodeposition technique of preparing nanoparticulate PtRu electrocatalyst for direct methanol fuel cells has been demonstrated. After extensive cyclic voltammetric analysis, we determined the optimized parameters for the methanol oxidation to be current on-time on 50 ms, current off-time of 400 ms, current density of 50 mA/cm2, and total charge of 8.0 C/cm2. In addition, the catalyst loading was measured at 68 μg/cm2, resulting in a mass activity of 213 mA/Pt.mg. The composition for the nanoparticles was confirmed as Pt65Ru35. High-magnification images on the specimen indicated fine particles in 4-20 nm with uniform distributions.

Synthesis of nanoparticulate Pt and PtRu were conducted in typical wet chemical approach on carbon nanocapsules (CNCs) and VXC72R for electrochemical characterization in acidic electrolyte. XRD of the as-synthesized powders indicated Pt and PtRu in FCC phase with particle sizes around 2~15 nm. Cyclic voltammetry of Pt/CNCs and PtRu/CNCs was analyzed for hydrogen oxidation reaction, revealing impressive catalytic power. In contrast, Pt/VXC72R and PtRu/VXC72R demonstrated moderately reduced performance. Our work suggested CNCs to be superb material as electrocatalyst support.

Iridium oxide is an attractive ceramic material for neurostimulation electrodes due to its desirable stability and biocompatibility. Electrostimulation medical devices for neural diseases require electroactive and biocompatible materials to transmit signals from electrodes to targeting tissues. In this study, we developed a cost effective and thickness controllable process to fabricate iridium oxide film by chemical bath deposition. The film thickness can be controlled by modifying solution recipe from 40 nm to 110 nm per batch. Surface morphology, crystallinity, and charge storage capacity of the iridium oxide with different thicknesses were analyzed. Accordingly, the iridium oxide films present rough and hydrophilic surfaces so that the films are expected to suitable for cell attachment and good biocompatibility for cell viability. In addition, the charge storage capacity (CSC) of the iridium oxide films with various thicknesses were significantly higher than platinum which is the conventional stimulation electrode material. Consequently, these results show advantages that make the iridium oxide film a promising neurostimulation electrode material for implantable medical devices in neural systems.

In this work, we demonstrate a simple scheme combining electrophoresis and electrodeposition to fabricate large-area unsupported Ni inverse opals. A variety of experimental variables are explored and the optimized parameters allows for the packing of 495 nm polystyrene microspheres on an ITO substrate to form a defectless colloidal crystal. Subsequently, a Ni plating is adopted to produce inverse opals, followed by the removal of the colloidal template and ITO substrate via chemical and physical routes. The large-area and free-standing Ni inverse opals (2×2 cm2) reveal hexagonally-arranged pores with interconnected pore channels. Materials characterization including SEM, XRD, AFM, Hall effect, 4-point probe, and porometer measurements are performed and their results are discussed.

By using nanoparticulate Ag as the activator to replace Pd, glyoxylic acid to replace formaldehyde as the reducing agent, 2,2’–bipyridine, K4Fe(CN)6, PEG-2000, Ascorbic acid, and Bis-(3-sodiumsulfopropyl disulfide) (SPS) as additives, we develop a Cu electroless plating bath to deposit Cu on activated polyimide substrates for flexible electronic devices. Polarization curves are recorded to elucidate the effect of additives over anodic behaviors of glyoxylic acid on activated substrates. Cyclic voltammetric measurements are carried out to clarify the responses of additives on both anodic and cathodic reactions occurring during electroless Cu deposition. SEM is used for observing the morphology of Cu deposition on Ag nanoparticle catalyzed polyimide substrates. XRD is adopted to determine the crystalline structure of Cu deposit. The quality of Cu deposit is inferred from electrical resistivity measurements. We demonstrate an optimized formula for relatively smooth Cu film with strong adhesion to the substrate.

We demonstrate our recent progress in conducting electrodeposition of CuMn thin film using a deep eutectic solvent, which consists of CHCl and ethyl glycol. The sources for Cu ions and Mn ions are C10H14CuO4 and MnCl2, respectively. Plating methods such as potentiostatic, galvanostatic, and current pulsing have been explored with relevant electrochemical parameters optimized and discussed. We determine that the current pulsing route enables the formation of CuMn thin film with desirable Mn amount. Material characterizations including Scanning Electron Microscopy, X-ray diffraction, X-ray Photoelectron Spectroscopy, and X-ray Absorption Microscopy have been carried out. Our results indicate that Mn exists in both metallic form and oxide, and after heat treatment, precipitates with excess Mn are found on the surface. In addition, the conductivity of deep eutectic electrolyte is greatly affected by the ambient moisture and consequently, the plating process is kept in a glovebox to minimize unnecessary interference.

Micro electrode array (MEA) has emerged as one of the most common tools to transmit electrostimulation signals. Innovative nanofabrication process provides high efficiency for implantable bio-devices by creating large surface area. One of the noticeable advantages of such nanostructured micro electrode is to minimize tissue damage and also to provide a suitable platform for neuron attached. Among neurostimulation electrode materials, iridium oxide has received substantial attention in recent years because of its unique ability to inject electric charge and its physical, chemical stability as well as its biocompatibility. On the other hand, anodic aluminum oxide (AAO) can be provide a wide range aspect ratio template for forming iridium oxide nanorods and nanowires on top of the microelectrode. In this study, we combined chemical bath deposition of iridium oxide and AAO templates to fabricate a nanostructured micro electrode array for implantable bio-devices. We also investigated the influence of the aspect ratio of AAO templates on stimulation performances and biocompatibilities of the nanostructured micro electrode array.

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