10 results on '"Chi, Hao-Chen"'
Search Results
2. Amperometric determination of NADH with Co3O4 nanosheet modifiedelectrode
- Author
-
Meng Shan Lin, Ying-Cih Chen, and Chi-Hao Chen
- Subjects
Detection limit ,Flow injection analysis ,Chemistry ,Inorganic chemistry ,Biomedical Engineering ,Biophysics ,General Medicine ,Ascorbic acid ,Redox ,Amperometry ,Linear range ,Electrochemistry ,Cobalt oxide ,Biotechnology ,Nanosheet - Abstract
In this work, we have developed a simple and reliable cobalt oxide (Co3O4) based amperometric sensor for the determination of NADH. A sheet shape Co3O4 nanooxide was synthesized by the CTAB assisted hydrothermal technique and was characterized by SEM and XPS. Owing to the redox property of Co3O4, the operating potential of NADH can be significantly reduced from 0.7down to 0.1 V. Compared to a commercial Co3O4 nanoparticle modified electrode, this nanosheet form cobalt oxide possesses a rapid background subsiding characteristic and a low residual current. This scheme was conducted on a flow injection system with a constant operating potential of 0.1 V (vs. Ag/AgCl, 3 M) in a 0.2 M phosphate buffer at pH 6.0. A suitable linear range from 10 to 100 μM (R=0.999) with a detection limit of 4.25 μM (S/N=3) was obtained. The RSD for 20 successive measurements of 75 μM NADH is only 1.4%, which indicates a high stability and no contamination during NADH oxidation. This scheme did not suffer from conventional antioxidants, including dopamine, uric acid, epinephrine, serotonin, histamine, and 4-acetaminophen, except ascorbic acid. Thus, an ascorbate oxidase was introduced to remove the ascorbic acid before the sample was injected into the flow injection analysis system. After this simple pretreatment, the influence of ascorbic acid was eliminated, successfully.
- Published
- 2013
3. Effect of passive film on electrochemical surface treatment for indium tin oxide
- Author
-
Yung-Fu Wu and Chi-Hao Chen
- Subjects
Materials science ,Passivation ,Mechanical Engineering ,Oxalic acid ,Inorganic chemistry ,Metals and Alloys ,chemistry.chemical_element ,Tin oxide ,digestive system ,Indium tin oxide ,chemistry.chemical_compound ,chemistry ,Mechanics of Materials ,Materials Chemistry ,Tartaric acid ,Tin ,Citric acid ,Indium - Abstract
Changes in indium tin oxide (ITO) film surface during electrochemical treatment in oxalic acid, tartaric acid, and citric acid were investigated. Controlling the voltage applied on ITO film allows the formation of a passive layer, effectively protecting the film surface. X-ray photoelectron spectrometry showed that the passive layer composition was predominantly SnO2 in tartaric acid, while a composite of tin oxide and tin carboxylate in citric or oxalic acid. Even though the passive films on ITO surface generated in these organic acids, the indium or tin could complex with the organic acid anions, enhancing the dissolution of ITO films. The experimental results show that the interaction between the dissolution and passivation could assist to planarize the ITO surface. We found that the optimal treatment at 0.5 V in 3 wt.% tartaric acid could provide the ITO surface with root-mean-squared roughness less than 1.0 nm, due to the weak complexing characteristics of tartaric acid.
- Published
- 2013
4. Airborne and Surface-Bound Microbial Contamination in Two Intensive Care Units of a Medical Center in Central Taiwan
- Author
-
Ping-Yun Huang, Zhi-Yuan Shi, Walter Den, Hui-Mei Huang, Jaw-Ji Tsai, and Chi-Hao Chen
- Subjects
biology ,Pseudomonas aeruginosa ,Pathogenic bacteria ,Contamination ,biology.organism_classification ,medicine.disease_cause ,Pollution ,Acinetobacter baumannii ,Microbiology ,Staphylococcus aureus ,Intensive care ,medicine ,Environmental Chemistry ,Escherichia coli ,Bacteria - Abstract
Samples of airborne and surface-bound microbial contamination were taken in two intensive care units of a large-scale medical center. Microbial analyses included total bacterial and fungal loads, as well as the four bacterial species of Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa and Acinetobacter baumannii. Among the 114 surface samples taken from seven designated surface locations of room and equipment for each patient, P. aeruginosa was the most frequently detected (19.3%) and most abundant (mean count: 4.18 cfu/plate) bacterium, whereas the respirator represented the most heavily contaminated surface location in both total pathogenic bacteria colony counts (272 cfu) and frequency of positive detection (38.2%). P. aeruginosa also represented the most frequently detected (39.1%, n = 46) and abundant (11.52 ± 17.16 cfu/m^3) bacterium in the air samples (n = 46), and was the only bacterium exhibiting a positive correlation of the mean counts between air and surface samples. The data analysis results further suggested a higher value of relative risk among the infected patients in the presence of the pathogens as compared to those in the absence of them, although the evidence of a of correlation for the individual bacterial species between the environmental samples and infected patients was inconclusive. This study also found that the mean airborne counts and the detection frequencies of these bacteria after patient visitation periods were higher than those before visitation, and that the installation of local air ionizers did not lead to any discernible differences in total bacterial and fungal concentrations.
- Published
- 2013
5. Time Reversal Processing Effect on Foci Structure in a Dynamic Ocean Waveguide
- Author
-
Chi-Hao Chen and Y. S. Chiu
- Subjects
Engineering ,business.industry ,Applied Mathematics ,Mechanical Engineering ,Acoustics ,Structure (category theory) ,Ocean environment ,Condensed Matter Physics ,Signal ,Optics ,Distortion ,Path (graph theory) ,Waveguide (acoustics) ,Bidirectional transmission ,business ,Underwater acoustic communication - Abstract
Time-reversal mirror (TRM) was recently developed for underwater communication system application. This technique has been introduced as an approach to compensate for signal distortion due to multiple path effect in ocean waveguide. TRM is used in this paper for sending a message signal in ocean waveguide, received at time-reversal-array (TRA), and retransmitted to the dynamic ocean environment with an internal solitary wave. The focal structures obtained from different simulating cases are used for bidirectional transmission expediency, and the TRA is used as the relay-line or trunked radio. Ocean waveguide characteristic effects on acoustical properties are also shown in this paper, and focal structure in different ocean environments is analyzed to provide an optimal approach to underwater communication systems and for physical insight's interests.
- Published
- 2007
6. Statistical Analysis of Sonar Performance Prediction in Littoral Environments
- Author
-
C.-W. Wang, Chi-Hao Chen, Yu-Hsing Chang, Chia-Wei Yang, and Mei-Chun Yuan
- Subjects
Applied Mathematics ,Mechanical Engineering ,Transmission loss ,Ambient noise level ,Range (statistics) ,Performance prediction ,Littoral zone ,Figure of merit ,Environmental science ,Condensed Matter Physics ,Sonar ,Standard deviation ,Marine engineering - Abstract
This paper presents the Statistical Analysis of Passive Sonar Performance Prediction in Littoral Environments. Passive sonar performance and acoustic prediction mainly refer to the detection range. The inputs for estimating the sonar detection range include the Figure of Merit (FOM), Transmission Loss (TL), and Ambient Noise (NL) of the operation region. These inputs are directly related to the ocean environment; hence, the detection range is, too. A littoral environment is highly variable both in time and space. This paper proposes a methodology for analyzing the statistical properties of the detection range from measurements of ocean water column properties. It is found that the detection range of the southwestern region of Taiwan in the summer is 13.8km with 5.9km as the standard deviation and in the winter is 37.8km with 33.6km as the standard deviation.
- Published
- 2006
7. Fast response time in liquid crystal cells doped with low concentrations of reactive mesogen via photopolymerization at low temperature
- Author
-
Che Ju Hsu, Chia Rong Sheu, Wen Ching Tsai, Liang Ying Huang, Chun Yu Chien, Seok Lyul Lee, Chi Hao Chen, Luo Yi Wu, and Chi-Yen Huang
- Subjects
Materials science ,Electrostriction ,Scanning electron microscope ,Mesogen ,Doping ,Analytical chemistry ,Response time ,02 engineering and technology ,021001 nanoscience & nanotechnology ,01 natural sciences ,Electronic, Optical and Magnetic Materials ,010309 optics ,Photopolymer ,Liquid crystal ,0103 physical sciences ,Contrast ratio ,0210 nano-technology ,health care economics and organizations - Abstract
Liquid crystal (LC) cells with photopolymers usually exhibit a fast response time but inevitably present decreased optical transmittance and lower contrast ratio due to incomplete dark states. In this study, we show that this issue can be improved when photopolymerization at low temperature is considered. Comparing performance with the 4 wt% RM257-doped fringe-field switching (FFS) LC cell photopolymerized at room temperature, the 1.4 wt% RM257-doped FFS LC cell photopolymerized at low temperature (273 K) shows better contrast ratio and lower operating voltage. In addition, the electrostriction effect can be also reduced in LC cells with lower RM257-doped concentration. As a result, the 1.4 wt% RM257-doped FFS cell shows a response time as fast as that in the 4 wt% RM257-doped FFS cell. Meanwhile, the average response time for gray-to-gray switching of the optimal FFS cell is 4.9 ms.
- Published
- 2017
8. Influence of Surface Hydrophobic Groups on the Adsorption of Proteins onto Nonporous Polymeric Particles with Immobilized Metal Ions
- Author
-
Hsuan Ang Tsai, Chi-Hao Chen, and Wen-Chien Lee
- Subjects
Dispersion polymerization ,Langmuir ,Glycidyl methacrylate ,Iminodiacetic acid ,Metal ions in aqueous solution ,technology, industry, and agriculture ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Biomaterials ,Hydrophobic effect ,chemistry.chemical_compound ,Colloid and Surface Chemistry ,Adsorption ,chemistry ,Polymer chemistry ,Organic chemistry ,Protein adsorption - Abstract
Iminodiacetic acid (IDA) and octyl moieties were covalently bound on nonporous particles, which were prepared from dispersion polymerization of methyl methacrylate and glycidyl methacrylate. After being charged with copper ions, the IDA-bound particles could specifically adsorb deoxyribonuclease I (DNase I) through the affinity interaction between protein and immobilized metal ion. A mixed-ligand (metal-chelate and octyl-bound) support was obtained after hydrophobic (octyl) groups were also introduced to the particle surface. The affinity adsorption of DNase I on the copper-IDA chelate was influenced by interaction between the protein and the bound octyl group. Both the affinity and the hydrophobic interactions could be well described by the Langmuir isotherms. The equilibrium adsorption constants were estimated separately to be 0.96 and 0.50 liter g(-1) for affinity and hydrophobic bindings, respectively. For binding on mixed-ligand support, the adsorption constant was 0.45 liter g(-1). It was evident that both affinity and hydrophobic interactions are involved in the adsorption of proteins onto mixed-ligand particles. Desorption of the inactive proteins from the support was possible by increasing the hydrophobicity of the solution. Copyright 2001 Academic Press.
- Published
- 2001
9. Amperometric determination of NADH with Co₃O₄ nanosheet modified electrode
- Author
-
Chi-Hao, Chen, Ying-Cih, Chen, and Meng-Shan, Lin
- Subjects
Serotonin ,Epinephrine ,Dopamine ,Metal Nanoparticles ,Oxides ,Ascorbic Acid ,Biosensing Techniques ,Cobalt ,NAD ,Electrodes ,Oxidation-Reduction ,Histamine ,Uric Acid - Abstract
In this work, we have developed a simple and reliable cobalt oxide (Co₃O₄) based amperometric sensor for the determination of NADH. A sheet shape Co₃O₄ nanooxide was synthesized by the CTAB assisted hydrothermal technique and was characterized by SEM and XPS. Owing to the redox property of Co₃O₄, the operating potential of NADH can be significantly reduced from 0.7 down to 0.1 V. Compared to a commercial Co₃O₄ nanoparticle modified electrode, this nanosheet form cobalt oxide possesses a rapid background subsiding characteristic and a low residual current. This scheme was conducted on a flow injection system with a constant operating potential of 0.1 V (vs. Ag/AgCl, 3 M) in a 0.2 M phosphate buffer at pH 6.0. A suitable linear range from 10 to 100 μM (R=0.999) with a detection limit of 4.25 μM (S/N=3) was obtained. The RSD for 20 successive measurements of 75 μM NADH is only 1.4%, which indicates a high stability and no contamination during NADH oxidation. This scheme did not suffer from conventional antioxidants, including dopamine, uric acid, epinephrine, serotonin, histamine, and 4-acetaminophen, except ascorbic acid. Thus, an ascorbate oxidase was introduced to remove the ascorbic acid before the sample was injected into the flow injection analysis system. After this simple pretreatment, the influence of ascorbic acid was eliminated, successfully.
- Published
- 2012
10. A novel structural specific creatinine sensing scheme for the determination of the urine creatinine
- Author
-
Meng Shan Lin and Chi-Hao Chen
- Subjects
Detection limit ,Creatinine ,Chromatography ,Conductometry ,Calibration curve ,Biomedical Engineering ,Biophysics ,General Medicine ,Biosensing Techniques ,Equipment Design ,Urinalysis ,High-performance liquid chromatography ,Amperometry ,Equipment Failure Analysis ,chemistry.chemical_compound ,chemistry ,Nafion ,Electrochemistry ,Copper plating ,Uric acid ,Electrodes ,Copper ,Biotechnology - Abstract
In this work, a highly structural dependent amperometric scheme was proposed for the determination of creatinine without enzymatic assistance. The principle of this novel method is based upon the formation of a soluble copper-creatinine complex on the copper electrode surface. Subsequently, an oxidative current from the regeneration of the surface oxide layer is monitored and it is proportional to the concentration of the creatinine. This scheme can be conducted at potential of -0.1 V (vs. Ag/AgCl, 3 M) in phosphate buffer (pH 7). A typical calibration plot from 25 μg/dL to 1.5 mg/dL (R(2)=0.997) with a detection limit of 6.8 μg/dL (S/N=3) is achieved. The relative standard deviation of 21 successive injections of 0.2 mg/dL creatinine is 0.018. Under the optimal conditions, the frequently encountered biological interferences at physiological or higher concentration were investigated. Only uric acid revealed an obvious interference (298.1%). However, a Nafion(®) coated copper plating electrode shows a successful decrement of the interference of the uric acid with slightly decreased sensitivity of creatinine. The feasibility of this scheme for further clinical application is demonstrated by both HPLC and FIA to evaluate the creatinine concentration in a urine sample.
- Published
- 2011
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