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151.
Diego Pallarola Luis Domenianni Graciela Priano Fernando Battaglini 《Electroanalysis》2007,19(6):690-697
In this work, two well known polymers, carboxymethyl dextran and poly(ethyleneglycol), are used for easily producing a platform for electrochemical affinity assays, avoiding nonspecific adsorption of proteins. In this way, modified electrode surfaces able to bind a recognition agent are constructed through simple and reliable reactions. 相似文献
152.
This paper deals with an often overlooked artifact in sequential and single extraction of metals from soils, viz. the volume to mass (V/m) ratio as a potential source for inadequate extraction yields. We offer a theoretical framework to get a grip on this intricate parameter and came up with a model based on a linear adsorption isotherm to derive the correct maximal metal extractability for a certain extractant. We verified the model experimentally using 0.1 mol l−1 nitric acid for extraction of seven metals (Cr, Co, Cu, Cd, Pb, Ni and Zn) from an urban soil sample, and concluded that commonly used V/m ratios in the range of 10-40 ml g−1 may give as much as 50% too low extraction yields. Thus, a strong caveat is in place as to be very critical what V/m ratios to use and preferably apply the model derived to obtain the correct maximal extractability using a variable V/m ratio method. 相似文献
153.
笼形聚氨肟树脂的研究:碱处理对吸附性能的影响 总被引:3,自引:1,他引:3
研究碱处理的笼形聚氨肟树脂(BCAO)对二价金属离子的吸附行为。吸附结果若生成2:1配的,得Mg^2+,Ca^2+,Ba^2+,Mn^2+,Co^2+,Ni^2+,Zn^2+,Cd^2+,Pb^2+,Cu^2+离子的吸附效率分别是27.1、29.2、30.4、29.0、27.1、30.8、45.0、39.8、60.3、62.1%,Hg^2+离子的吸附效率高达105%,表明在吸附过程中同时生成2:1 相似文献
154.
金属离子在煤界面吸附对煤成浆性的影响 总被引:7,自引:1,他引:7
本文研究了六种金属离子在三种煤表面的吸附规律,研究结果表明:铜离子能够改善煤的制浆效果,即铜离子加入煤浆中,分散剂的用量降低50%,煤浆浓度提高;钙、镁、钴、锌离子对煤的成浆性不利的原因是它们不能有效地被吸附到煤表面,游离的金属离子和分散剂发生反应,使得吸附到煤表面的分散剂相对减少,煤的成浆性变差。 相似文献
155.
Electrochemical and electrocatalytic properties of thin films Au(111-25 nm), which are quasi-single-crystal electrodes 25
nm thick made of gold with the (111) preferential orientation, and same electrodes modified with a monolayer (ML) of palladium
are studied in 0.1 M solutions of HClO4 and H2SO4 employing voltammetric techniques and surface enhanced infrared reflection absorption spectroscopy (ATR-SEIRAS). Spectroscopic
experiments demonstrate strong adsorption of electrolyte species (H2O, OHads, anions) on the Pd surface. The weak and reversible adsorption of CO on Au(111-25 nm) does not change the interfacial-water
structure. Adsorption of CO on the Pd-modified film results in an irreversibly adsorbed CO adlayer stabilized by co-adsorbed
isolated water species. Various electrooxidation mechanisms are discussed. Electrochemical and spectroscopic investigations
on the adsorption and electrooxidation of HCOOH on bare and 1 ML Pd-Au(111-25 nm) electrodes reveal that electrooxidation
proceeds in both cases via a direct or dehydrogenation pathway. This mechanism involves the formation of formate as intermediate,
which is detected by in situ ATR-SEIRAS. The reactivity on Pd-modified surfaces is higher than on bare gold. The specifically
adsorbed anions (sulfate/bisulfate) and the oxide formation on the substrate surface lower the reactivity for CO and HCOOH
on both surfaces.
Published in Russian in Elektrokhimiya, 2006, Vol. 42, No. 11, pp. 1312–1329.
Based on the report delivered at the 8th International Frumkin Symposium “Kinetics of the Electrode Processes,” October 18–22,
2005, Moscow.
The text was submitted by the authors in English. 相似文献
156.
比较两种超高交联聚苯乙烯吸附树脂NJ-8、AM-1与Amberlite XAD-4(以下简称XAD-4)对对硝基苯乙酮的静态吸附行为,根据吸附等温线研究了吸附热力学性质.在298~318K和研究的浓度范围内,NJ-8,AM-1、XAD-4对对硝基苯乙酮的吸附平衡数据符合Freundlich吸附等温方程.结果表明:吸附为放热过程,适当降低温度有利于吸附.计算了对硝基苯乙酮在NJ-8,AM-1、XAD-4树脂上的吸附焓变、自由能变,吸附熵变.对吸附行为作了合理的解释。 相似文献
157.
Chi-Chang?HuEmail author Hong-Ru?Chiang Chen-Ching?Wang 《Journal of Solid State Electrochemistry》2003,7(8):477-484
The electrochemical characteristics of ruthenium oxides, formed on Ru-plated Ti electrodes in 0.5 M H2SO4 by potential cycling with different CV upper potential limits (E
SU), were systematically compared. The repeated potential cycling between 0.2 and 0.75 V activated the formation/reduction of
surface Ru oxides with hysteretic behavior. This application of repeated CVs also modified the ability of Ru deposits for
hydrogen adsorption/desorption. An irreducible Ru oxide accumulated on the electrode at potentials more positive than ca.
0.95 V, whose capacitive characteristics are applicable for electrochemical supercapacitors. This irreducible oxide was composed
of an aggregate consisting of Ru in various oxidation states, bridged oxygen, OH and water in a 3D-like structure with a relatively
ordered and compact nature, from the X-ray photoelectron spectroscopic and voltammetric results. The surface reconstruction
of the Ru deposits induced by the repeated potential cycling with E
SU≥0.75 V was clearly observed from the SEM photographs. From the X-ray diffraction patterns, all the anodically formed Ru oxides
showed an amorphous nature. 相似文献
158.
Enhancing the enzymatic hydrolysis of cellulosic materials using simultaneous ball milling 总被引:1,自引:0,他引:1
Mais Ursula Esteghlalian Ali R. Saddler John N. Mansfield Shawn D. 《Applied biochemistry and biotechnology》2002,98(1-9):815-832
One of the limiting factors restricting the effective and efficient bioconversion of softwood-derived lignocellulosic residues
is the recalcitrance of the substrate following pretreatment. Consequently, the ensuing enzymatic process requires relatively
high enzyme loadings to produce monomeric carbohydrates that are readily fermentable by ethanologenic microorganisms. In an
attempt to circumvent the need for larger enzyme loadings, a simultaneous physical and enzymatic hydrolysis treatment was
evaluated. A ball-mill reactor was used as the digestion vessel, and the extent and rate of hydrolysis were monitored. Concurrently,
enzyme adsorption profiles and the rate of conversion during the course of hydrolysis were monitored. α-Cellulose, employed
as a model substrate, and SO2-impregnated steam-exploded Douglas-fir wood chips were assessed as the cellulosic substrates. The softwood-derived substrate
was further posttreated with water and hot alkaline hydrogen peroxide to remove >90% of the original lignin. Experiments at
different reaction conditions were evaluated, including substrate concentration, enzyme loading, reaction volumes, and number
of ball beads employed during mechanical milling. It was apparent that the best conditions for the enzymatic hydrolysis of
α-cellulose were attained using a higher number of beads, while the presence of air-liquid interface did not seem to affect
the rate of saccharification. Similarly, when employing the lignocellulosic substrate, up to 100% hydrolysis could be achieved
with a minimum enzyme loading (10 filter paper units/g of cellulose), at lower substrate concentrations and with a greater
number of reaction beads during milling. It was apparent that the combined strategy of simultaneous ball milling and enzymatic
hydrolysis could improve the rate of saccharification and/or reduce the enzyme loading required to attain total hydrolysis
of the carbohydrate moieties. 相似文献
159.
S. V. Shishkina T. G. Drushlyak L. A. Kutulya N. S. Pivnenko O. V. Shishkin 《Journal of Structural Chemistry》2004,45(5):889-895
X-ray analysis was carried out to study the molecular structure of β-hydroxyketone, which is one of the minor products of selective aldol condensation of (−)-menthone with 4-carbomethoxybenzaldehyde. The cyclohexanone ring of the compound has a practically undistorted chair conformation with an axial orientation of the 1-methyl group and the bulkiest 2-[1′-hydroxy-1′ -(4-carbomethoxyphenyl)]methyl substituent and the equatorial orientation of the isopropyl group in the 4 position. The stereochemical configuration was found to be (1R,2R,4 R, 1′ S), supporting that the compound belongs to the group of (+)-isomenthones; i.e., the starting (-)-menthone undergoes (to a certain extent) epimerization under the reaction conditions used. In crystal, there is intermolecular hydrogen bonding >C=O...HO- (the -O...H- bond length is 2.15 Å). The molecular conformation in hydroxyketone crystals differs from the one which prevails in solutions (according to previous NMR data) and which is characterized by an inverted cyclohexanone ring and intramolecular hydrogen bonding >C=O...HO.Original Russian Text Copyright © 2004 by S. V. Shishkina, T. G. Drushlyak, L. A. Kutulya, N. S. Pivnenko, and O. V. Shishkin__________Translated from Zhurnal Strukturnoi Khimii, Vol. 45, No. 5, pp. 933–940, September–October, 2004. 相似文献
160.
Jiang Wei Dorthe Bagge Ravn Lone Gram Peter Kingshott 《Colloids and surfaces. B, Biointerfaces》2003,32(4):275-291
The surface of AISI 316 grade stainless steel (SS) was modified with a layer of poly(ethylene glycol) (PEG) (molecular weight 5000) with the aim of preventing protein adsorption and bacterial adhesion. Model SS substrates were first modified to introduce a very high density of reactive amine groups by the adsorption of branched poly(ethylenimine) (PEI) from water. Methoxy-terminated aldehyde-poly(ethylene glycol) (M-PEG-CHO) was then grafted onto the PEI layers using reductive amination at the lower critical solution temperature (LCST) of the PEG in order to optimize the graft density of the linear PEG chains. The chemical composition and uniformity of the surfaces were determined using X-ray photoelectron spectroscopy (XPS) and time-of-flight static secondary ion mass spectrometry (ToF-SSIMS) in the imaging mode. The effects of PEI concentration and different substrate pre-cleaning methods on the structure and stability of the final PEG layer was examined. Piranha solution proved to be the most effective method for removing adventitious hydrocarbon contamination, compared to cleaning with ultrasonication in organic solvents, and was the SS substrate that produced the most stable and thickest PEI layer. The surface density of PEI was shown to increase with increasing PEI concentration (up to 30 mg/ml), as determined from XPS measurements, and subsequently produced the PEG layer with the highest density of attached chains. In model experiments using β-lactoglobulin no protein adsorption was detected on the optimized PEG surface as determined by XPS and ToF-SSIMS analysis. However, neither the adhesion of a Gram-negative (Pseudomonas sp.) nor a Gram-positive (Listeria monocytogenes) bacterium was affected by the coating as equal numbers adhered to all surfaces tested. Our results show that preventing protein adsorption is not a prerequisite stopping bacterial adhesion, and that other mechanisms most likely play a role. 相似文献