Nanoporous Platinum Research Articles

CMOS-Integrable Enzyme-Free Amperometric Cholesterol Nano-Biosensor for U-Health and POC Applications

In this research, CMOS-integrable enzyme-free amperometric cholesterol nano-biosensors with nanoporous platinum (Pt) electrodes were designed, fabricated and analyzed. These nano-biosensors were fabricated on silicon substrates for U-health and POC (point of care) system applications by using a nonionic surfactant and electroplating technique. These nano-biosensors worked e ciently at an applied potential of 400 mV and exhibited excellent linearity in the cholesterol concentration range from 10 M to 8 mM. They also showed good temperature tolerance up to 50 C. The fabricated nano-biosensors with a nanoporous Pt working electrode (WE) and a 50m spacing between the WE and the counter electrode (CE), with a nanoporous Pt WE and a 10m spacing between the WE and the CE and with a nanoporous Pt WE/CE with a 50m spacing exhibited the cholesterol sensitivity of 13.03 A/mM cm2, 29.9 A/mM cm2 and 30.95 A/mM cm2, respectively. These nano-biosensors were not a ected by several interference species in blood.

Synthesis and Characterization of Nanoporous Palladium and Platinum Powders

not Available.

Fully Packaged Nonenzymatic Glucose Microsensors With Nanoporous Platinum Electrodes for Anti-Fouling

CMOS integrable nonenzymatic glucose microsensors with nanoporous platinum (Pt) working and counter electrode (WE/CE) were first fabricated, packaged, and characterized with biocompatible Nafion and hydrophilic polyurethane (HPU) membrane materials. Optimal packaging material and its processing condition for these nonenzymatic sensors were investigated. The optimally packaged glucose microsensor was evaluated in human blood plasma solution for checking its biocompatibility and commercial applicability. The fabricated microsensors with nanoporous Pt WE/CE had a sensitivity of 7.75 muA mM <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-2</sup> . The packaged microsensor with Nafion membrane had better performance characteristics than packaged one with HPU. The packaged microsensor with 1:6 ratio of Nafion to ethanol exhibited a sensitivity of 0.83 mu A mM <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-2</sup> and stable current change in the human blood plasma solution, while the current response of nonpackaged microsensor was rapidly saturated because adsorption of various proteins and cells as expected. These data indicate that the packaged nonenzymatic microsensor with biocompatible Nafion membrane is promising and strongly applicable for <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">in</i> <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">vitro</i> and <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">in</i> <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">vivo</i> glucose monitoring systems.

Fabrication and Optimization of a Nanoporous Platinum Electrode and a Non-enzymatic Glucose Micro-sensor on Silicon

In this paper, optimal conditions for fabrication of nanoporous platinum (Pt) were investigated in order to use it as a sensitive sensing electrode for silicon CMOS integrable non-enzymatic glucose micro-sensor applications. Applied charges, voltages, and temperatures were varied during the electroplating of Pt into the formed nonionic surfactant C16EO8 nano-scaled molds in order to fabricate nanoporous Pt electrodes with large surface roughness factor (RF), uniformity, and reproducibility. The fabricated nanoporous Pt electrodes were characterized using atomic force microscopy (AFM) and electrochemical cyclic voltammograms. Optimal electroplating conditions were determined to be an applied charge of 35 mC/mm2, a voltage of -0.12 V, and a temperature of 25 °C, respectively. The optimized nanoporous Pt electrode had an electrochemical RF of 375 and excellent reproducibility. The optimized nanoporous Pt electrode was applied to fabricate non-enzymatic glucose micro-sensor with three electrode systems. The fabricated sensor had a size of 3 mm × 3 mm, air gap of 10 μm, working electrode (WE) area of 4.4 mm2, and sensitivity of 37.5 μA•L/mmol•cm2. In addition, it showed large detection range from 0.05 to 30 mmolL-1 and stable recovery responsive to the step changes in glucose concentration.

Fabrication and Optimization of a Nanoporous Platinum Electrode and a Non-enzymatic Glucose Micro-sensor on Silicon.

In this paper, optimal conditions for fabrication of nanoporous platinum (Pt) were investigated in order to use it as a sensitive sensing electrode for silicon CMOS integrable non-enzymatic glucose micro-sensor applications. Applied charges, voltages, and temperatures were varied during the electroplating of Pt into the formed nonionic surfactant C16EO8 nano-scaled molds in order to fabricate nanoporous Pt electrodes with large surface roughness factor (RF), uniformity, and reproducibility. The fabricated nanoporous Pt electrodes were characterized using atomic force microscopy (AFM) and electrochemical cyclic voltammograms. Optimal electroplating conditions were determined to be an applied charge of 35 mC/mm2, a voltage of -0.12 V, and a temperature of 25 °C, respectively. The optimized nanoporous Pt electrode had an electrochemical RF of 375 and excellent reproducibility. The optimized nanoporous Pt electrode was applied to fabricate non-enzymatic glucose micro-sensor with three electrode systems. The fabricated sensor had a size of 3 mm x 3 mm, air gap of 10 µm, working electrode (WE) area of 4.4 mm2, and sensitivity of 37.5 µA•L/mmol•cm2. In addition, it showed large detection range from 0.05 to 30 mmolL-1 and stable recovery responsive to the step changes in glucose concentration.

A Nonenzymatic Glucose Sensor Using Nanoporous Platinum Electrodes Prepared by Electrochemical Alloying/Dealloying in a Water‐Insensitive Zinc Chloride‐1‐Ethyl‐3‐Methylimidazolium Chloride Ionic Liquid

AbstractWe report here a nonenzymatic sensor by using a nanoporous platinum electrode to detect glucose directly. The electrode was fabricated by electrochemical deposition and dissolution of PtZn alloy in zinc chloride‐1‐ethyl‐3‐methylimidazolium chloride (ZnCl2‐EMIC) ionic liquid. Both SEM and electrochemical studies showed the evidences for the nanoporous characteristics of the as‐prepared Pt electrodes. Amperometric measurements allow observation of the electrochemical oxidation of glucose at 0.4 V (vs. Ag/AgCl) in pH 7.4 phosphate buffer solution. The sensor also demonstrates significant reproducibility in glucose detection; the higher the roughness factor of the Pt electrode, the lower the detection limit of glucose. The interfering species such as ascorbic acid and p‐acetamidophenol can be avoided by using a Pt electrode with a high roughness factor of 151. Overall, the nanoporous Pt electrode is promising for enzymeless detection of glucose at physiological condition.

Apparent electrocatalysis on 3D nanoporous platinum film electroplated from hexagonal lyotropic liquid crystalline phase of Triton X-100

Electrocatalytic effect of nanoporous interface between platinum (Pt) and electrolyte was investigated in terms of direct electrochemical oxidation of glucose. A Pt film with 3D nanopores was electroplated from the hexagonal (H 1) lyotropic liquid crystal (LLC) phase of t-octylphenoxypolyethoxyethanol (Triton X-100), a nonionic surfactant with a phenyl group in a hydrophobic tail. This Pt film, which was electroplated from H 1-LLC of Triton X-100 (ePt-H 1-TX100), comprised closely stacked crystalline (face centered cubic) nanoparticles (diameter, 4–7 nm) with 3D nanopores (width, 1–2 nm) developed among the particles. The ePt-H 1-TX100 showed high surface roughness and selective enhancement of a sluggish redox reaction, that is, kinetic-controlled reaction such as glucose oxidation. Nonenzymatic glucose sensing can be achieved by using discriminatively enhanced sensitivity to glucose over redox active interfering molecules.

Adsorbate effects on the surface stress–charge response of platinum electrodes

The length change in response to changes in the surface stress during scans of the electrode potential was measured for nanoporous platinum samples immersed in aqueous NaF, an electrolyte with weak ion adsorption. The surface stress–charge response may be characterized separately for four different processes, selected by the potential range and by the surface pretreatment: hydrogen adsorption/desorption, oxygen adsorption/desorption (and/or surface oxidation/reduction), and nominally capacitive charging of the Pt surface in two different states, clean and oxide-covered. While each process exhibits a roughly linear response, the magnitude and even the sign of the slope, which determines the surface stress–charge coefficient, ζ, differ. We suggest that the sign of ζ depends on the penetration depth of the excess charge: for strong screening the electronic charge is located outside of the surface, and ζ is negative as found previously for clean metal surfaces. For weaker screening, the wider space charge layer implies a trend for the excess charge to fill bulk-like unoccupied states. These states are here antibonding, giving positive-valued ζ.

Regulation of Electrochemical Oxidation of Glucose by lonic Strength-Controlled Virtual Area of Nanoporous Platinum Electrode

Electrochemical reaction of glucose was regulated by the electrochemically active area of nanoporous platinum, which is controlled by ionic strength. The profile of the oxidation current of glucose vs. ionic strength was identical with that of the electrochemically active area. This result confirms that the nanopores are virtually opened for the electrochemical reaction of glucose when the ionic strength climbs over a specific concentration and implies that the electrochemical reactions on nanoporous electrode surfaces can be controlled by concentration of electrolyte.

Development of a membrane-based electrochemical immunosensor

A membrane-based electrochemical immunosensor sensitive towards proteins is described, based on nanoporous alumina-modified platinum wire electrodes. The sensing mechanism depends on the blocking of pore channels when the protein antigen molecules bind to antibody molecules attached to the channel walls, impeding the diffusion of redox probe, ferrocenemethanol, towards the sensing platinum wire overlaid by the nanoporous alumina film. The antibody and antigen used in this work were anti-glucose oxidase and glucose oxidase, respectively. The immunosensor showed a low limit of detection of 100 ng L −1 antigen concentration and was selective towards glucose oxidase protein in the presence of another protein, glucothione S-transferase.

Development of Guidelines for Nanobiosensor Evaluation as Medical Devices

To use nanobiosensors as diagnostic devices, they should be evaluated and approved as medical devices before marketing. This study was performed to establish appropriate evaluation guidelines that provide how to verify the safety and effectiveness of a novel nanobiosensor as a medical device. We prepared an enzymeless glucose sensor with nanoporous platinum electrode to evaluate performance and stability by comparing it with a commercial enzyme-based glucose sensor. Through these evaluation studies, we developed guidelines, and the guidelines consist of five parts: evaluation of analytical performance, clinical performance, safety, stability, and design and quality control systems. Analytical and clinical performance of nanobiosensors should be evaluated by accuracy, sensitivity, reproducibility, cut-off value, and other specific performance characteristics. Also, electric, mechanical, and biological safety should be evaluated. With the performance and safety, validation of storing conditions and shelf life should be established with evaluation and characterization of nano-structured parts for stability evaluation. Then, design and quality control systems should be evaluated in the aspect of quality requirements, material, manufacturing process, and final product. These guidelines will be helpful for facilitating the commercialization of the safe, effective, and novel diagnostic nanobiosensors into market place.

Synthesis and characterization of ruthenium-decorated nanoporous platinum materials

We report on the synthesis of novel three-dimensional nanoporous Pt–Ru bimetallicnetworks by decorating nanoporous Pt networks with Ru using a hydrothermally assistedprecipitating process. Scanning electron microscopy (SEM) and energy dispersive x-rayspectroscopy (EDS) were used to characterize the morphology and the composition ofthe nanoporous Pt–Ru networks formed. X-ray diffraction analysis confirmedthat, after protected annealing treatment, Pt–Ru bimetallic material was formed.The electrocatalytic activity of the synthesized nanoporous Pt–Ru networks wascharacterized using electrochemical oxidation of methanol as a probe. The electrocatalyticactivity of the nanoporous Pt networks significantly increases with the increments ofdecorated Ru and reaches the highest value with 41% of Ru. The peak current ofmethanol oxidation on the nanoporous Pt–Ru(41%) bimetallic networks is over180% higher than that on the nanoporous Pt networks without Ru decoration.This is very desirable for fuel cell development and electrochemical sensor design.

Solid‐State Reference Electrode Based on Electrodeposited Nanoporous Platinum for Microchip

AbstractA new solid‐state reference electrode operating in buffered aqueous solution for electrochemical system on microfluidic chip is reported. The anodized nanoporous platinum showed its usefulness as a solid‐state reference electrode owing to near‐Nernstian behavior, low hysteresis, and quick response. The presence of redox couples such as Fe(CN)$\rm{ _6^{3 - /4 - } }$, bringing about significant interference, can be successfully suppressed by an electropolymerized poly‐1,3‐phenylendiamine (poly‐m‐PD) layer on the nanoporous platinum surface. Since the poly‐m‐PD coated nanoporous platinum oxide responds exclusively to pH, its potential should be constant and stable in a buffer solution. The nanoporous platinum oxide with poly‐m‐PD film is easy to produce and is particularly compatible with microfabrication. The experimental results in this study demonstrate that the proposed system successfully works as a solid‐state reference electrode that should be integrated on microchips for microanalysis systems.

Integration of a Nanoporous Platinum Thin Film into a Microfluidic System for Non-enzymatic Electrochemical Glucose Sensing

In this paper, we describe an amperometric-type enzymeless glucose sensing system based on a nanoporous platinum (Pt) electrode embedded in a microfluidic chip. This microchip system is comprised of a microfluidic transport channel network and a miniaturized electrochemical cell for nonenzymatic glucose sensing. Sample and buffer solutions were transferred to the cell by programmed electroosmotic flow (EOF). A nanoporous Pt electrode with the roughness factor of 200.6 was utilized to determine glucose concentrations in phosphate buffered saline (PBS) by the direct oxidation of glucose, without any separation process. The sensitivity of the developed system is 1.65 microA cm-2 mM-1 in the glucose concentration range from 1-10 mM in PBS.

Electrochemical oxidation of hydrogen peroxide at nanoporous platinum electrodes and the application to glutamate microsensor

The electrochemical behavior of hydrogen peroxide (H 2O 2) at nanoporous platinum (Pt) thin film was investigated and the reaction of the enzymes immobilized on the electrode was examined. The nanoporous Pt underlying the enzyme layer was electrochemically deposited on Pt–Ir alloy microelectrodes in the solution consisting of hexachloroplatinic acid and a non-ionic surfactant, octaethylene glycol monohexadecyl ether (C 16EO 8). Glutamate oxidases were entrapped during electro-polymerization of 1,3-phenylenediamine on the nanoporous Pt microelectrodes to form a glutamate oxidase layer. The glutamate microsensors as made were compared with flat Pt-based one in terms of the performance and characteristics.

High surface area nanoporous platinum: facile fabrication and electrocatalyticactivity

In this paper, nanoporous platinum films with an enhanced surface area wereobtained through a facile route by selective anodic dissolution of Cu from PtCualloy. A homogeneous PtCu alloy was electrochemically deposited at a glassycarbon electrode at room temperature, then Cu was electrochemically etchedfrom the PtCu alloy resulting in the fabrication of a nanoporous platinum filmwith a much higher surface area. The surface area of the dealloyed nanoporousplatinum film was highly enhanced by up to 500 times compared with that of apolycrystalline platinum electrode. This nanoporous platinum film exhibited highstability and remarkable catalytic activity for oxygen electro-reduction and methanolelectro-oxidation, with promising applications in fuel cells and biosensors, etc.

Facile Fabrication of Nanoporous Platinum by Selective Anodic Dissolution of Cu from Electrodeposited PtCu Alloy

not Available.

PH-Sensitive Solid-State Electrode Based on Electrodeposited Nanoporous Platinum

The nanoporous platinum oxide (H1-ePtO) as a hydrogen ion-selective sensing material is reported. Bare nanoporous platinum oxides exhibit near-Nernstian behavior (e.g., -55 mV/pH in PBS), ignorable hysteresis, a short response time, and high precision, which are remarkably better than those of flat platinum oxides. The electrode potential of a nanoporous platinum oxide responds exclusively to hydrogen ion, which implies its usefulness as a solid-state pH sensor. In the present study, the performance of nanoporous platinum oxide was investigated and compared with that of IrOx in terms of selectivity and the influences of ionic strength, temperature, complexing ligands, and surfactants. H1-ePtO functions well as a pH-sensing solid-state material, and it is viewed as a promising alternative to IrOx. Interference by redox couples was successfully suppressed by covering the H1-ePtO surface with a protective layer, e.g., an electropolymerized polyphenol thin film. Since the nanoporous platinum oxide with such a protective layer is particularly suitable for miniaturization and micropatterning, our findings suggest its usefulness in applications such as solid-state pH sensors embedded in chip-based microanalysis systems.

Investigation on the dye-sensitized solar cell

The key technologies in dye-sensitized solar cell, including nanoporous TiO２2 film, dye-sensitizer, electrolyte, platinum catalysis, and TCO glass, have bee n investigated, and we also optimized the different technologies with assemblyin g the small area dye-sensitized solar cells. About 9% photo-electric conversion efficiency has been demostrated in our lab under AM1.5 solar simulator. Our results show that there would be a possibility for commercial production based on our technologies.

Synthesis and characterization of nanoporous metallic platinum

Nanoporous metallic platinum with a high specific surface area of 91 m 2/g was synthesized by a templating method using nonporous silica nanoparticles. The templating reaction is constituted of four steps: (1) a coating reaction of a Pt compound on the silica surface; (2) reduction of the Pt compound; (3) dissolution of the silica by alkaline treatment; (4) removal of residual carbon in the nanoporous platinum by heat treatment. Thus, nanoporous metallic platinum, stabilized by a small amount of carbon, can successfully be obtained by a relatively convenient synthetic process. This material can be a promising model material for development of new scientific fields concerned with electromagnetic properties and a functional material applicable to fuel cell or catalytic reactions.