Shih-Han Wang

Bimetallic PtM (M = Pd, Ir) nanoparticle decorated multi-walled carbon nanotube enzyme-free, mediator-less amperometric sensor for H2O2

A new highly catalytic and intensely sensitive amperometric sensor based on PtM (where M=Pd, Ir) bimetallic nanoparticles (NPs) for the rapid and accurate estimation of hydrogen peroxide (H(2)O(2)) by electrooxidation in physiological conditions is reported. PtPd and PtIr NPs-decorated multiwalled carbon nanotube nanocatalysts (PtM/MWCNTs) were prepared by a modified Watanabe method, and were characterized by XRD, TEM, ICP, and XAS. The sensors were constructed by immobilizing PtM/MWCNTs nanocatalysts in a Nafion film on a glassy carbon electrode. Both PtPd/MWCNTs and PtIr/MWCNTs assemblies catalyzed the electrochemical oxidation of H(2)O(2). Cyclic voltammetry characterization measurements revealed that both the PtM (M=Pd, Ir)/MWCNTs/GCE possessed similar electrochemical surface areas (∼0.55 cm(2)), and electron transfer rate constants (∼1.23 × 10(-3)cms(-1)); however, the PtPd sensor showed a better performance in H(2)O(2) sensing than did the PtIr counterpart. Explanations were sought from XAS measurements to explain the reasons for differences in sensor activity. When applied to the electrochemical detection of H(2)O(2), the PtPd/MWCNTs/GC electrode exhibited a low detection limit of 1.2 μM with a wide linear range of 2.5-125 μM (R(2)=0.9996). A low working potential (0V (SCE)), fast amperometric response (<5s), and high sensitivity (414.8 μA mM(-1)cm(-2)) were achieved at the PtPd/MWCNTs/GC electrode. In addition, the PtPd/MWCNTs nanocatalyst sensor electrode also exhibited excellent reproducibility and stability. Along with these attractive features, the sensor electrode also displayed very high specificity to H(2)O(2) with complete elimination of interference from UA, AA, AAP and glucose.

Fabrication and application of amperometric glucose biosensor based on a novel PtPd bimetallic nanoparticle decorated multi-walled carbon nanotube catalyst

A sensitive, selective and stable amperometric glucose biosensor employing novel PtPd bimetallic nanoparticles decorated on multi-walled carbon nanotubes (PtPd-MWCNTs) was investigated. PtPd-MWCNTs were prepared by a modified Watanabe method, and characterized by XRD and TEM. The biosensor was constructed by immobilizing the PtPd-MWCNTs catalysts in a Nafion film on a glassy carbon electrode. An inner Nafion film coating was used to eliminate common interferents such as uric acid, ascorbic acid and fructose. Finally, a highly porous surface with an orderly three-dimensional network enzyme layer (CS-GA-GOx) was fabricated by electrodeposition. The resulting biosensor exhibited a good response to glucose with a wide linear range (0.062-14.07 mM) and a low detection limit 0.031 mM. The biosensor also showed a short response time (within 5 s), and a high sensitivity (112 μA mM(-1)cm(-2)). The Michaelis-Menten constant (K(m)) was determined as 3.3 mM. In addition, the biosensor exhibited high reproducibility, good storage stability and satisfactory anti-interference ability. The applicability of the biosensor to actual serum sample analysis was also evaluated.

Thick-Film Carbon Dioxide Sensor via Anodic Adsorbate Stripping Technique and Its Structural Dependence

A three-electrode based CO2 sensor was fabricated using thick-film technology. The performance of this sensor was further enhanced by incorporating platinum nanoparticles onto the working electrode surface. An eight-fold increase in the signal output was obtained from the electrode with the platinum nanoparticles. The sensing output was linearly related to the CO2 presented. Stability measurements demonstrated that the decline of the active surface area and the sensitivity of the sensor were 8% and 13%, respectively, over a two week period of time. The sensor response appeared to be a structural dependence of the crystallographic orientation of platinum electrode.

A Room Temperature Nitric Oxide Gas Sensor Based on a Copper-Ion-Doped Polyaniline/Tungsten Oxide Nanocomposite

The parts-per-billion-level nitric oxide (NO) gas sensing capability of a copper-ion-doped polyaniline/tungsten oxide nanocomposite (Cu2+/PANI/WO3) film coated on a Rayleigh surface acoustic wave device was investigated. The sensor developed in this study was sensitive to NO gas at room temperature in dry nitrogen. The surface morphology, dopant distribution, and electric properties were characterized using scanning electron microscopy, energy-dispersive X-ray spectroscopy mapping, and Hall effect measurements, respectively. The Cu2+/PANI/WO3 film exhibited high NO gas sensitivity and selectivity as well as long-term stability. At 1 ppb of NO, a signal with a frequency shift of 4.3 ppm and a signal-to-noise ratio of 17 was observed. The sensor exhibited distinct selectivity toward NO gas with no substantial response to O2, NH3 and CO2 gases.

Detection of cartilage oligomeric matrix protein using a quartz crystal microbalance.

Current methods for the accurate diagnosis of osteoarthritis (OA) based on magnetic resonance imaging and enzyme-linked immunosorbent assay method are highly sensitive and specific but require specialised laboratory facilities and highly trained operators to obtain a definitive result. A quartz crystal microbalance (QCM) immunosensor has been developed to detect cartilage oligomeric matrix protein (COMP) in this work. This QCM immunosensor was fabricated to immobilize COMP antibodies in orientation. Its potential dynamically monitored the processes of immunoreaction and could evaluate for the rapid and sensitive detection of COMP in laboratory-cultured preparations and clinical samples. The frequency response of the QCM immunosensor changed 10 kHz to 100 ng/ml COMP. The linear regression equation of frequency shift and COMP concentration is y = 0.0872 x + 1.2138 (R2 =0.9957).

Propagation Characteristics of Surface Acoustic Wave and Properties of Gas Sensors on Quartz

The simulation of wave propagation in periodic piezoelectric surface acoustic wave (SAW) structures was reported in this study. Firstly, space harmonics method (SHM) was used to analyze Rayleigh SAW propagation under a periodic Al grating. The results of SAW propagation analysis were applied to design a two-port resonator with Al grating on ST-cut quartz. The measured frequency response of the two-port resonator was approximately similar to the simulation one. Then, the chemical interface of polyaniline/WO3 composites was coated on the SAW resonator for ammonia detection. The SAW sensor responded to the ammonia gas and could be recovered using dry nitrogen. Detecting to 9.3ppm ammonia, the frequency shift was 5.9ppm, the noise level was 0.18ppm, and a signal-tonoise ratio was 32.8.

Piezoelectric sensor for sensitive determination of metal ions based on the phosphate-modified dendrimer

Heavy metal ions arising from human activities are retained strongly in water; therefore public water supplies must be monitored regularly to ensure the timely detection of potential problems. A phosphate-modified dendrimer film was investigated on a quartz crystal microbalance (QCM) for sensing metal ions in water at room temperature in this study. The chemical structures and sensing properties were characterized by Fourier transform infrared spectroscopy and QCM measurement, respectively. This phosphate-modified dendrimer sensor can directly detect metal ions in aqueous solutions. This novel sensor was evaluated for its capacity to sense various metal ions. The sensor exhibited a higher sensitivity level and shorter response time to copper(II) ions than other sensors. The linear detection range of the prepared QCM based on the phosphate-modified dendrimer was 0.0001 ~ 1 μM Cu(II) ions (R2 = 0.98). The detection properties, including sensitivity, response time, selectivity, reusability, maximum adsorption capacity, and adsorption equilibrium constants, were also investigated.

A Nitrogen Dioxide Surface Acoustic Wave Sensor Based on Polyaniline/Tungsten Oxide Nanocomposite

A surface acoustic wave sensor (SAW) based on polyaniline/tungsten oxide nanocomposite thin film was used to detect nitrogen dioxide at room temperature in this study. Polyaniline/tungsten oxide nanocomposite structure was fabricated from the aniline monomer and tungsten oxide gel. The coupling of modes (COM) theory was used to design the SAW device and simulate the performances of the SAW device. The theoretical simulation of the SAW device was similar to the experimental results. The presented SAW sensor exhibited reversibility and repeatability with reasonable response time when nitrogen dioxide was in ppm level at room temperature. The frequency shift of sensor was 0.5 ppm to 11 ppm nitrogen dioxide.