Chan-Hwa Chung

Decomposition of toluene using an atmospheric pressure plasma/TiO2 catalytic system

Abstract Application of atmospheric pressure plasma as an alternative technology for the destruction of toluene is demonstrated in this study. Used TiO 2 colloidal solution was obtained by an improved sol–gel method, and coated on glass beads to prepare decomposition of toluene. The physical property of synthesized TiO 2 catalyst film was analyzed by XRD and SEM spectroscopy. From these results, it was identified that the catalyst film exhibited anatase structure with particle size of about 50–100xa0nm after calcination at 500xa0°C for 1xa0h. The decomposition of toluene in TiO 2 /O 2 plasma system was investigated. Amounts of the catalyst and toluene concentration were fixed as 3xa0wt.% and 1000xa0ppm, respectively. The analyses for performance of toluene decomposition and intermediates in reaction were done by the in situ method using the mass spectroscopy and gas chromatography. The toluene of 40% was decomposed at pulse voltage of 13xa0kV in the only O 2 plasma condition without TiO 2 catalyst. Furthermore, the conversion enhanced remarkably in the TiO 2 /O 2 plasma system, and it reached 70% at pulse voltage of 13xa0kV after 120xa0min. This result was very notable compared with that in photocatalytic system, with below 40% after 120xa0min reaction.

Characterization of a TiO2 photocatalyst synthesized by the solvothermal method and its catalytic performance for CHCl3 decomposition

Abstract It is considered that the solvothermal method in this study renders a reliable synthesis procedure of the TiO2 photocatalyst having the anatase structure of nano size. Two kinds of TiO2 photocatalysts were synthesized by using the sol–gel and solvothermal methods, and then their physical properties and catalytic performances were compared. The TiO2 powder (Cat. 2) obtained by the solvothermal method at 300°C exhibited a pure anatase structure without any further treatment, while the TiO2 powder (Cat. 1) prepared by the sol–gel method was transformed to the anatase structure after thermal treatment at 500°C for 3xa0h. Cat. 2 had higher surface area (121xa0m2/g) and surface charge (+24.1xa0mV) than Cat. 1 (51xa0m2/g, +16.4xa0mV). In addition, the activation energy for H2O desorption over Cat. 2 was very high. These results show that the surface of Cat. 2 is very hydrophilic. In chloroform (CHCl3) decomposition under the UV-light (254xa0nm, 24xa0W/m2) with O2 bubbling (500xa0ml/min), the catalytic performance of Cat. 2 was considerably higher than that of Cat. 1. More than 95% of the chloroform was decomposed in 2xa0h over Cat. 2.

SYNTHESIS OF TIO2 PHOTOCATALYST THIN FILM BY SOLVOTHERMAL METHOD WITH A SMALL AMOUNT OF WATER AND ITS PHOTOCATALYTIC PERFORMANCE

Abstract Colloidal solutions containing nano-sized TiO2 particles were successfully obtained by adding a small amount of water and employing solvothermal method. A thin film obtained from this colloidal solution (Cat. 2) exhibited much better properties than another film obtained via a sol–gel method (Cat. 1). The former had smaller and more uniform TiO2 particles than the latter; it also had the anatase structure even after drying at 200°C; a much thinner film of Cat. 2 could be obtained and this film could remain stably attached on a silicon wafer or on a pyrex plate after a thermal treatment. Cat. 2 coated on a γ-alumina exhibited excellent performance for photocatalytic decomposition of CHCl3 under UV-light with O2 bubbling (90% conversion in 10xa0min), when comparing with a result obtained without the catalyst (70% conversion after 1xa0h).

Nanoporous Pt@Au(x)Cu(100-x) by hydrogen evolution assisted electrodeposition of Au(x)Cu(100-x) and galvanic replacement of Cu with Pt: electrocatalytic properties.

Electrodeposition of high-surface-area nanoporous Au-Cu foams under conditions of hydrogen codeposition is studied. The honeycomb-like Au(x)Cu(100-x) foams with 0 ≤ x ≤ 100 are electrodeposited by controlling the amount of corresponding ions in the solution. The amount of metal ions in deposited films follows that in used electrolytes. Compared to monometallic foams, the Au(x)Cu(100-x) structures are characterized by smaller ligament or particle sizes (less than 10 nm) and improved stability. The addition of even a small amount of Cu to the Au matrix is found to dramatically improve the stability of the structure in air environment or an acidic medium. Pt@Au(x)Cu(100-x) structures are formed by the galvanic displacement of Cu from Au(x)Cu(100-x) templates. During the displacement of Cu by Pt, Au serves as a buffer, decreasing mechanical stresses and preventing the detachment of the foam from the substrate. The surface ratio of Pt to Au atoms is controlled by adjusting the amount of Cu in the template. Pt@Au(x)Cu(100-x) electrodes are investigated as novel electrocatalysts for methanol oxidation in alkaline media. The Au-enriched surfaces show higher catalytic activity toward methanol oxidation, while the electrodes with a higher amount of Pt are more stable.

Removal of paraquat in aqueous suspension of TiO2 in an immersed UV photoreactor

Experiments were performed to investigate the effect of operating parameters on the photodegradation efficiency of paraquat in a TiO2-suspended photoreactor with immersed UV lamps. TiO2 particles were prepared by a hydrothermal method. The removal rate of paraquat in the reactor was 0.54 mg/l/h with only air-sparging. The removal rate in 24 h with both the UV radiation and air-sparging was 50% higher than that with only the UV radiation. Variations of the paraquat concentration at the UV intensities of 4 and 8 W/m2 decreased slowly with time, but that at 12 W/m2 decreased more rapidly. The removal efficiency at the air-sparging flow rate of 1 //min increased as a UV light intensity increased. pH value in the reactor at the UV intensity of 12 W/m2 decreased with time until 12 h and then increased with time over 12 h.

Usefulness of a photophobia questionnaire in patients with migraine

Photophobia is an important criterion for the diagnosis of migraine. However, several Asian epidemiological surveys about migraine have shown lesser prevalence of photophobia than that of Western studies. This discrepancy is probably caused by underestimation of photophobia due to inappropriate questioning of patients by physicians. To investigate this issue, we developed a questionnaire about photophobia and evaluated its usefulness in 103 patients with migraine. In phase 1 of the study, we found good repeatability of the questionnaire with a 0.826 k coefficient. In phase 2, the prevalence of photophobia from interviews and that from the questionnaire were compared. The prevalence of interview-documented photophobia was 51.5% and of questionnaire-documented photophobia 82.5% (P < 0.001). In phase 3, we attempted to make a short-form questionnaire with the same detection power of the questionnaire study. Two short-form questionnaires were identified as a useful method for detecting photophobia. The prevalence of photophobia could be underreported via interview, especially in Asian migraineurs. Using this questionnaire to test for photophobia, the diagnostic rate of photophobia and migraine could be improved.

Differential Effects of Corticosteroids on The Expression of Cyclooxygenase-2, Tumour Necrosis Factor-Alpha and Matrix Metalloproteinase-9 in An Animal Model of Migraine

Nitric oxide (NO) directly activates trigeminal afferents innervating the dura mater and up-regulates inflammatory mediators. We evaluated NO-mediated up-regulation of cyclooxygenase-2 (COX-2), tumour necrosis factor-alpha (TNF-α) and matrix metalloproteinase-9 (MMP-9), and the effect of glucocorticoid administration in an experimental animal model of migraine. COX-2 and TNF-α expression and MMP-9 activity were increased after continuous intravenous infusion of glyceryl trinitrate (GTN), a NO donor. Immunofluorescence staining demonstrated strong expression of these inflammatory mediators in the meningeal blood vessels. Methylprednisolone (MP) down-regulated MMP-9, which was reversed by RU486, a glucocorticoid receptor antagonist. COX-2 and TNF-α expression was not affected by MP or RU486 administration. These results suggest proinflammatory mediators are involved in the NO-mediated cascade of migraine pathogenesis. Further understanding of the activation of these inflammatory mediators at the transcriptional level may have therapeutic implications for future migraine treatments.

A case of symptomatic hypnic headache syndrome

The hypnic headache syndrome is a rare, benign, nocturnal, non-familial headache disorder that occurs only while asleep. Since the first description by Raskin (1) in 1998, the syndrome has been characterized by a diffuse headache that awakens patients at a consistent time of the night, sometimes during a dream, and lasts for 30–180 min. This disorder mainly affects elderly subjects and both sexes equally (2). The pathophysiological mechanism of hypnic headache is not known, but its circadian periodicity and responsiveness to lithium carbonate suggest that perturbation of chronobiological rhythms causes this headache (1). We describe a patient with hypnic headache, which had developed after pontine infarction. To our knowledge, this is the first report of symptomatic hypnic headache that developed after stroke and that suggests direct evidence of a potential pathophysiological mechanism and relationship of hypnic headache to the sleep cycle.

Dendritic nanoporous nickel oxides for a supercapacitor prepared by a galvanic displacement reaction with chlorine ions as an accelerator

Dendritic nanoporous nickel oxide and tube-like nickel–tin oxide electrodes were prepared by a galvanic displacement reaction in an aqueous electrolyte containing chlorine ions which dramatically accelerated the reaction. The nanoporous nickel oxide showed a capacitance of 1242 F g−1, 97.4% of which was retained even after 5000 charge–discharge cycles.

Surfactant Effects on the Morphology and Pseudocapacitive Behavior of V2O5⋅H2O

To overcome the drawback of low electrical conductivity within supercapacitor applications, several surfactants are used for nanoscale V2 O5 to enhance the specific surface area. Polyethylene glycol 6000 (PEG-6000), sodium dodecylbenzene sulfonate (SDBS), and Pluronic P-123 (P123) controllers, if used as soft templates, easily form large specific surface area crystals. However, the specific mechanism through which this occurs and the influence of these surfactants is not clear for V2 O5 ⋅H2 O. In the present study, we aimed to investigate the mechanism of crystal growth through hydrothermal processes and the pseudocapacitive behavior of these crystals formed by using diverse surfactants, including PEG-6000, SDBS, and P123. Our results show that different surfactants can dramatically influence the morphology and capacitive behavior of V2 O5 ⋅H2 O powders. Linear nanowires, flower-like flakes, and curly bundled nanowires can be obtained because of electrostatic interactions in the presence of PEG-6000, SDBS, and P123, respectively. Furthermore, the electrochemical performance of these powders shows that the nanowires, which are electrodes mediated by PEG-6000, exhibit the highest capacitance of 349u2005Fu2009g(-1) at a scan rate of 5u2005mVu2009s(-1) of all the surfactants studied. However, a symmetric P123 electrode comprising curly bundled nanowires with numerous nanopores showed an excellent and stable specific capacitance of 127u2005Fu2009g(-1) after 200u2005cycles. This work is beneficial to understanding the fundamental role of the surfactant in the assisted growth of V2 O5 ⋅H2 O and the resulting electrochemical properties of the pseudocapacitors, which could be useful for the future design of appropriate materials.