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131.
Enhancing the organic dye adsorption on porous xerogels 总被引:4,自引:0,他引:4
Zhijian Wu Ik-Sung Ahn Chang-Ha Lee Jung-Hyun Kim Yong Gun Shul Kangtaek Lee 《Colloids and surfaces. A, Physicochemical and engineering aspects》2004,240(1-3):157-164
We investigate the adsorption of four different organic dyes (i.e., methyl orange, alizarin red S, brilliant blue FCF, and phenol red) on porous xerogels. To understand the factors affecting the adsorption capacity of the xerogels, we vary the hydrophobicity and the textural properties of the xerogels as well as the solution pH. We control the hydrophobicity by mixing two different precursors (i.e., vinyltriethoxysilane (VTES) and tetraethoxysilane (TEOS)) and the textural properties by using cetyltrimethylammonium bromide (CTAB) as a templating agent. We find that the adsorption capacity is enhanced as the organic/inorganic hybrid xerogel or the templated xerogel is used instead of the purely inorganic or the untemplated xerogel. In all the cases studied, adsorption decreases as the pH is increased due to the electrostatic repulsion between the dyes and the xerogel surface. We find that both the hydrophobic surface and larger pore size/volume are required to enhance the adsorption capacity significantly. 相似文献
132.
133.
A. Hussain C.W. Ahn H.J. Lee I.W. Kim J.S. Lee S.J. Jeong S.K. Rout 《Current Applied Physics》2010,10(1):305-310
We have fabricated lead-free Bi0.5(Na0.75K0.25)0.5TiO3 (BNKT) ceramics by a conventional process (CP) and reactive templated grain growth (RTGG) methods. The effect of grain orientation on structure, dielectric, complex impedance and electrical properties was investigated. The phase formation and grain morphology of BNKT ceramics were examined by X-ray diffraction (XRD) and scanning electron microscope (SEM), respectively. High dielectric constant and low dielectric loss was observed for grain oriented (textured) BNKT ceramics. Complex impedance, temperature dependent ac and dc conductivity were performed to explore the conduction behavior of the prepared BNKT ceramics. 相似文献
134.
Peptides containing azaglycine located terminally or within the backbone have been prepared in the solid phase by means of an automatic synthesizer. 相似文献
135.
Jang HS Ryu KE Ahn WS Chun HJ Dal Park H Park KD Kim YH 《Colloids and surfaces. B, Biointerfaces》2006,50(2):141-146
Previously, novel poly(ethylene glycol) (PEG) and sulfonated PEG acrylate (PEG-SO3A/OA) copolymers were prepared as coating and/or blending materials for biomedical applications. Surfaces modified with copolymers exhibited increased anti-coagulation properties and decreased plasma adsorption level due to increased hydrophilic properties and reorientation characteristics of PEG/PEG-SO3A chains in water phase. As continuation study, anti-complement effects of PEG-SO3/OA copolymers were investigated in vitro, and compared with those of low-density polyethylene (LDPE) and PEG/OA. C3 activation by PEG-SO3/OA samples was lower than that by PEG/OA samples, which was attributed to decreased surface nucleophile level of samples. PEG-SO3/OA samples increased inhibition of Bb production, resulting in decreased C5 activation. Owing to reduced activations of C3 and C5, PEG-SO3/OA samples markedly decreased SC5b-9 levels in plasma. 相似文献
136.
The reaction of AgX (X− = NO3
−, ClO4
−, or CF3SO3
−) with 1,3-bis(3-pyridyl)tetramethyldisiloxane (L) at room temperature affords 20-membered metallacyclodimers, [Ag(L)]2(X)2. For the macrocyclodimer, fine competition among argentophilic, electrostatic, and π···π interaction exists. The macrocyclodimer
is a unique molecular chair that tunes a transannular argentophilic interaction via the bite size of the counteranions. In
order to reversibly control the argentophilic interaction, anion exchange has been accomplished. The anion exchangeability
depends on the water solubility rather than the electrostatic interaction between silver(I) and anions. 相似文献
137.
Soojin Park Wha‐Keun Ahn Sunyoung Lee Sang Yun Han Bum Ku Rhee Han Bin Oh 《Rapid communications in mass spectrometry : RCM》2009,23(23):3609-3620
Ultraviolet (UV) photodissociation (PD) experiments using 266 nm light were performed for a series of phosphopeptide cations in a Fourier transform mass spectrometer. The objective of the experiments was to determine whether 266 nm UV irradiation on the phosphopeptide cations would induce unique peptide backbone dissociation. In addition, the general behavior of the phosphate loss (?80 or ?98 Da) was monitored, particularly for those phosphopeptides with a phosphotyrosine residue that itself is a UV chromophore. For phosphopeptides with a UV chromophore, their photodissociation behavior was very similar to that of low‐energy sustained off‐resonance irradiation collisionally activated dissociation (SORI‐CAD), with a few exceptions. For example, b‐ and y‐type peptide backbone fragments were prevalent, and their dephosphorylation behavior was consistent with that of the SORI‐CAD results. For phosphoserine peptides, the loss of a phosphate group was always observed. On the other hand, for phosphotyrosine peptides, the phosphate loss was found to be dependent on the presence of a basic amino group in the sequence and the charge state of the precursor ions, in agreement with the CAD results in the literature. However, hydrogen atom loss or aromatic side chain loss, which is known to be the excited state specific fragmentation pathway, was rarely observed in our 266 nm UV PD experiments, in contrast to the previous UV PD literature (particularly at 220 nm). The mechanism for these observations is described in terms of dominant internal conversion followed by intramolecular vibrational energy redistribution (IVR). Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
138.
139.
A series of crosslinked polymer electrolyte membranes were prepared by blending cellulose and sulfosuccinic acid (SA) for
fuel cell applications. The crosslinking reaction of membranes occurred via the esterification between –OH of cellulose and
–COOH of SA, as confirmed by FT-IR spectroscopy. Both the ion exchange capacity and the proton conductivity increased in proportion
to the increase of SA concentrations due to the increasing portion of charged groups in the membrane. In contrast, the water
uptake linearly increased up to 25 wt.% of SA concentration, above which it decreased abruptly. The maximum behavior of water
uptake may be a result of competitive effect between the increasing number of ionic sites and the increasing degree of crosslinking
with the SA concentrations. Wide angle X-ray scattering also showed that the crystalline structures of cellulose disappeared
upon the introduction of SA. The mechanical properties of cellulose/SA membranes, i.e., tensile strength at break and Young’s
modulus, showed a maximum at 15 wt.% of SA, as revealed by universal testing machine. These membranes exhibited good thermal
stability up to 250 °C, as revealed by thermal gravimetric analysis. 相似文献
140.
Relationships between an assembler and a vendor in a supply chain are investigated in two-period models when the assembler wants to reduce response time by incentive systems. The assembler may offer myopic or farsighted incentive contracts to the vendor, under short-term or long-term relationships. Incentive schemes, effort levels, and expected payoffs under different perspectives and relationships are examined. We find that a farsighted assembler provides the vendor with a higher incentive than a myopic assembler in the first period. A long (short)-term relationship is preferred if the value of farsightedness under a long-term relationship is greater (less) than the switching option value under a short-term relationship. We propose several sufficient conditions regarding which perspectives and relationships are preferred. 相似文献