Enhancement of CO2 sorption uptake on hydrotalcite by impregnation with K2CO3

The awareness of symptoms of global warming and its seriousness urges the development of technologies to reduce greenhouse gas emissions. Carbon dioxide (CO(2)) is a representative greenhouse gas, and numerous methods to capture and storage CO(2) have been considered. Recently, the technology to remove high-temperature CO(2) by sorption has received lots of attention. In this study, hydrotalcite, which has been known to have CO(2) sorption capability at high temperature, was impregnated with K(2)CO(3) to enhance CO(2) sorption uptake, and the mechanism of CO(2) sorption enhancement on K(2)CO(3)-promoted hydrotalcite was investigated. Thermogravimetric analysis was used to measure equilibrium CO(2) sorption uptake and to estimate CO(2) sorption kinetics. The analyses based on N(2) gas physisorption, X-ray diffractometry, Fourier transform infrared spectrometry, Raman spectrometry, transmission electron microscopy, scanning electron microscopy, and energy dispersive X-ray spectroscopy were carried out to elucidate the characteristics of sorbents and the mechanism of enhanced CO(2) sorption. The equilibrium CO(2) sorption uptake on hydrotalcite could be increased up to 10 times by impregnation with K(2)CO(3), and there was an optimal amount of K(2)CO(3) for a maximum equilibrium CO(2) sorption uptake. In the K(2)CO(3)-promoted hydrotalcite, K(2)CO(3) was incorporated without changing the structure of hydrotalcite and it was thermally stabilized, resulting in the enhanced equilibrium CO(2) sorption uptake and fast CO(2) sorption kinetics.     

A two-photon excited luminescence of water-soluble rhodamine-platinum(II) complex: fluorescent probe specific for Hg2+ detection in live cell

The first example of cyclometalated platinum(II)-containing rhodamine probe (1) with two-photon induced luminescent properties was synthesized and investigated for mercury detection. A highly selective color change of 1, from light yellow to pink, is observed only in the presence of Hg²⁺ due to the formation of 1,3,4-oxadiazole ring in 2. This selectivity of Hg²⁺ with color changes can be observed easily by the naked-eye. Meanwhile, a remarkable turn-on and selective 20-fold fluorescent enhancement of 1 upon binding with Hg²⁺ over the other tested metal ions was observed. The water-soluble probe 1 was successfully applied in the visualizing of the site of Hg²⁺ accumulation as well as estimating of trace amounts of mercury ions in live HeLa cells by two-photon microscopy.     

Detection of mutant p53 using field-effect transistor biosensor

We assessed the abilities of wild p53 and mutant p53 proteins to interact with the consensus DNA-binding sequence using a MOSFET biosensor. This is the first report in which mutant p53 has been detected on the basis of DNA-protein interaction using a FET-type biosensor. In an effort to evaluate the performance of this protocol, we constructed the core domain of wild p53 and mutant p53 (R248W), which is DNA-binding-defective. After the immobilization of the cognate DNA to the sensing layer, wild p53 and mutant p53 were applied to the DNA-coated gate surface, and subsequently analyzed using a semiconductor analyzer. As a consequence, a significant up-shift in drain current was noted in response to wild p53, but not mutant p53, thereby indicating that sequence-specific DNA-protein interactions could be successfully monitored using a field-effect-based biosensor. These data also corresponded to the results obtained using surface plasmon resonance (SPR) measurements. Taken together, our results show that a FET-type biosensor might be promising for the monitoring of mutant p53 on the basis of its DNA-binding activity, providing us with very valuable insights into the monitoring for diseases, particularly those associated with DNA-protein binding events.     

Quantification of oxyresveratrol analog trans-2,4,3',5'-tetramethoxystilbene in rat plasma by a rapid HPLC method: application in a pre-clinical pharmacokinetic study

A rapid HPLC method was developed and validated for the quantification of oxyresveratrol analog trans‐2,4,3′,5′‐tetramethoxystilbene (oxyresveratrol tetramethyl ether, OTE) in rat plasma. Chromatographic separation was achieved on an RP‐HPLC column, which was protected by a guard column through a 12 min gradient delivery of a mixture of acetonitrile–water at 50°C. The UV absorbance at 325 nm was recorded. The retention time of OTE and trans‐stilbene (internal standard) was about 7.7 and 8.4 min, respectively. The calibration curves were linear (R² ≥ 0.9986) with a lower limit of quantification of 15 ng/mL. The intra‐ and inter‐day variations, in terms of RSD, were all lower than 9.8% while the intra‐day and inter‐day bias ranged from ?8.3 to +9.2%. The pharmacokinetics of OTE was assessed in rats using 2‐hydroxypropyl‐β‐cyclodextrin as a dosing vehicle. After intravenous administration, OTE possessed a long terminal elimination half‐life (t_{1/2 λz} = 481 ± 137 min) and slow clearance (Cl = 29.1 ± 3.7 mL/min/kg). Upon oral administration, OTE was rapidly absorbed. However, it only displayed minimal plasma exposure and its absolute oral bioavailability (F) was as low as 4.5 ± 3.2%. Fortunately, the levels of OTE after single oral administration were sufficient to inhibit human cytochrome P450 1B1. Copyright © 2010 John Wiley & Sons, Ltd.     

Development of Batch and Continuous Processes on Biodiesel Production in a Packed-Bed Reactor by a Mixture of Immobilized Candida rugosa and Rhizopus oryzae Lipases

In this study, transesterification and esterification were investigated in batch and continuous process using immobilized Candida rugosa and Rhizopus oryzae lipases. In the case of batch process, stepwise reaction method was investigated to prevent the lipase deactivation. Reaction conditions were as follows: temperature, 45 °C; agitation speed, 250 rpm; enzyme concentration, 20%; and water contents 10%. And then, conversion yield was 98.33% at 4 h. In the case of continuous process, circulation and long-term continuous system were investigated for development of efficient mass transfer system. Optimal reaction conditions were as follows: temperature, 45 °C; flow rate, 0.8 mL/min; and water contents, 10%. And then, conversion yield of biodiesel was 97.98% at 3 h. Especially, the maximum conversion yield using a mixture of immobilized lipases exceeded over 90% for 108 h in long-term continuous system under optimal reaction conditions (45 °C; flow rate, 0.8 mL/min; and water contents, 10%). These results should help in determining the best method for the biodiesel production and improving the design and operation of large scale by enzymatic systems.     

Electrochemical and spectroscopic investigations of Tb(III) in molten LiCl–KCl eutectic at high temperature

Electrochemical and spectroscopic properties of Tb(III) in molten LiCl–KCl eutectic at high temperature were investigated by cyclic voltammetry and time-resolved laser-induced fluorescence spectroscopy (TRLFS). The diffusion coefficient of Tb(III) and the formal standard potential of Tb(III)/Tb⁰ were determined to be 2.06 ± 0.4 × 10^? 5 cm² s^? 1 and ? 2.83 ± 0.03 V vs. Cl₂/Cl^? at 887 K, respectively. Additionally, visible fluorescence of Tb(III) due to the electronic transitions from ⁵D₃ and ⁵D₄ to ⁷F_J was observed and measured by TRLFS for the first time. These results provide the first fluorescence spectroscopic evidence for a direct in situ quantification of Tb(III) in the high temperature molten salt system.     

Graphene supported electrocatalysts for methanol oxidation

Graphene nanosheet was prepared by modified Hummer’s chemical method and utilized as a catalyst support of PtRu nanoparticles for the electro-oxidation of methanol. Home-made graphene nanosheet was clearly characterized by Raman spectroscopy and we applied colloidal method to synthesize with high metal content of 80 wt.% Pt–Ru catalyst, which is extensively clarified by HR-TEM and XRD analysis. 80 wt.% Pt–Ru/graphene nanosheet catalyst showed superior electrochemical activity toward methanol oxidation compared to Pt–Ru/Vulcan XC-72R. It is due to the significant increase of electrochemical active surface area for better catalyst utilization.     

Tuning the band-gap energy of TiO2-xCx nanoparticle for high performance photo-catalyst

We describe a method tuning the band-gap energy (E_g) of visible light sensitive TiO_2-xC_x nanoparticle. E_g tends to become smaller with the increase in the amount of carbon dopant in TiO_2-xC_x nanoparticle due to the increase in excess electrons. Photo-catalytic oxidative activity, however, did not depend on only the value of E_g, but also the energy level of valence band. TiO_1.96C_0.04 nanoparticle having E_g of 2.6 eV showed outstanding performance in oxidative decomposition of phenol under the irradiation of visible light.     

Luminescence efficiencies of self- and Tm activated CaWO4 under vacuum ultraviolet radiation excitation

Luminescence efficiency of self-activated CaWO₄ under 147 nm vacuum ultraviolet (VUV) radiation excitation is about 90% of that of BaMgAl₁₀O₁₇:Eu²⁺ (BAM), the commercial blue plasma display panel (PDP) phosphor. However, the color purity and the particle size of the former needs substantial modification before it can be considered for application in PDP. CaWO₄:Tm exhibits Tm³⁺ emission peaks in the blue region due to energy transfer from WO₄ to Tm³⁺ ions but the overall emission intensity under 147 nm excitation is reduced when compared to that of CaWO₄.