Co-reporter:Miaomiao Wang, Na Du, Yaohua Zhong, and Xirong Huang
Journal of Chemical & Engineering Data 2017 Volume 62(Issue 2) pp:
Publication Date(Web):January 26, 2017
DOI:10.1021/acs.jced.6b00956
The ε-β fishlike phase diagram of the system [C16mim]Br/[Omim]Tf2N/water was constructed in the presence of different additives (alcohol and inorganic salt). From the diagram some additive-dependent characteristic physicochemical parameters were obtained. Results show that with the increase of the alkyl chain length of alcohols, the solubility of the alcohol in [Omim]Tf2N, and the optimum solubilization parameter (SP*) decrease, while the maximum alcohol width (△ε) for the phase inversion and the mass fraction of the alcohol in the balanced interfacial film (Ain) increase. For inorganic salts, an increase in [NaCl], or an increase of the radius of halides (X–) at constant [NaX], or the substitution of the divalent anion SO42– by the same molar concentration of monovalent anion Cl– makes both SP* and △ε increase, but Ain decrease. Overall, the alcohol effect on the phase behavior of the microemulsion is greater than the salt effect, and the composition effect of an inorganic salt is greater than the concentration effect. These effects could be rationalized based on their influence on the dissolution and aggregation behavior of the surfactant [C16mim]Br in the system.
Co-reporter:Qian Li;Xirong Huang
Journal of Solution Chemistry 2017 Volume 46( Issue 9-10) pp:1792-1804
Publication Date(Web):31 May 2017
DOI:10.1007/s10953-017-0632-9
A new strategy is proposed here to formulate a bis(2-ethyl-1-hexyl)sulfosuccinate (AOT−) stabilized water-in-ionic liquid microemulsion without any additives. Replacing the inorganic counter ion Na+ by the organic 1-butyl-3-methylimidazolium ([Bmim]+) ion greatly improves the solubility of AOT− in hydrophobic 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([Bmim]Tf2N) (IL) and favors the formation of water-in-IL (W/IL) microdroplets. The existence of the W/IL microdroplets has been confirmed by dynamic light scattering, Fourier transform infrared absorption spectroscopy and ultraviolet–visible absorption spectroscopy. Also, presented for the first time are the effects of salts and alcohols on the microstructure and water solubilization capacity of the ternary H2O/[Bmim]AOT/[Bmim]Tf2N system. For inorganic salts, larger concentrations of the salt and higher charge density of the cation result in smaller microdroplet size and weak water solubilization capacity. For 1-hexanol, a high concentration of this alcohol results in small microdroplet size but high water solubilization capacity. Analyses indicate that the salts compress the electric double layers of W/IL microemulsions, decrease the size of the microdroplets and consequently reduce the water solubilization capacity; the alcohol, however, facilitates the aggregation of AOT−, increases the number of W/IL microdroplets, and therefore improves the water solubilization capacity of the system.
Co-reporter:Jing Zhang, Yuyan Xiao, Yaohua Zhong, Na Du, and Xirong Huang
ACS Sustainable Chemistry & Engineering 2016 Volume 4(Issue 7) pp:3995
Publication Date(Web):June 13, 2016
DOI:10.1021/acssuschemeng.6b00882
The ionic liquid [HNMP]Cl-catalyzed dehydration of fructose into 5-hydroxymethylfurfural (HMF) in deep eutectic solvents (formed by [Emim]Cl and different alcohols) was investigated. The experimental results indicated that the polarity of an alcohol and its stereostructure were major factors influencing fructose dehydration and that isopropanol was the optimum alcohol for the conversion system. Studies on the mechanism of the alcohol effect indicated that an alcohol could influence the formation of intermediates and their further transformation via the hydrogen bonds formed with [Emim]Cl and [HNMP]Cl. For the normal alcohols, the shorter the chain, the higher is the polarity and the stronger the ability to form the hydrogen bond; as a result, the alcohol with the shortest chain has the greatest negative effect on fructose dehydration. For the branched chain alcohols, the existence of steric hindrance led to their weaker ability to form the hydrogen bond with the ionic liquid so that their negative effects on the conversion were much smaller. The DES composed of equal moles of [Emim]Cl and isopropanol is the best one for the conversion of fructose into HMF catalyzed by [HNMP]Cl with an HMF yield of up to 89% after 3 h of reaction at 25 °C.Keywords: 5-Hydroxymethylfurfural; Alcohol; Fructose; Hydrogen bond; Steric hindrance;
Co-reporter:Xinxin Yu, Qian Li, Miaomiao Wang, Na Du and Xirong Huang
Soft Matter 2016 vol. 12(Issue 6) pp:1713-1720
Publication Date(Web):07 Dec 2015
DOI:10.1039/C5SM02704G
To formulate a compatible green medium for the conversion of a hydrophobic substrate by a hydrophilic enzyme, we investigated the phase behavior of pseudo ternary hydrophobic ionic liquid (HIL)/buffer/polyoxyethylene-type nonionic surfactant (CnEm)/n-alcohol system and the effects of the components on the formulation of the HIL-based bicontinuous microemulsion. It is found that small head group of the surfactant, high concentration of n-alcohol (medium/long alkyl chain) and low cohesive energy density of the HIL result in low phase transition temperature. In the CnEm stabilized compatible bicontinuous microemulsion, the kinetics of laccase catalyzed oxidation of 2,6-dimethoxyphenol were also investigated. It is found that in addition to temperature, n-alcohol is the key parameter affecting the catalytic performance of laccase, and the optimum n-alcohol depends on the type of HIL as an oil phase. All the kinetic parameters, such as Km, kcat, kcat/Km, and Ea (apparent activation energy), indicate that the bicontinuous microemulsion consisting of [Omim]NTf2/buffer/CnEm/n-hexanol is a suitable medium for the laccase-catalyzed reaction. To the best of our knowledge, this is the first report on the formulation of HIL-based bicontinuous microemulsion for enzyme catalysis.
Co-reporter:Feifan Wang, Feixue Zou, Xinxin Yu, Zhenyu Feng, Na Du, Yaohua Zhong and Xirong Huang
Physical Chemistry Chemical Physics 2016 vol. 18(Issue 15) pp:9999-10004
Publication Date(Web):11 Mar 2016
DOI:10.1039/C6CP00800C
A non-aqueous solution of tetra-n-butylammonium fluoride (TBAF) in ethylene glycol has been tried for the first time as a supporting electrolyte for the electropolymerization of 3-aminophenylboronic acid (APBA). Unlike the traditional acidic aqueous solution, the present medium needs no exogenous protons; moreover, the presence of CF3COOH is found to be unfavorable for the polymerization. The protons are in situ generated by the reaction between the boronic acid group on APBA and 1,2-dihydroxyl on ethylene glycol. So, ethylene glycol serves as not only the solvent but also the proton source. As a part of the supporting electrolyte, F− is found to be involved in the electrochemical synthesis of poly(3-aminophenylboronic acid) (PAPBA), but it is not indispensable. Studies on the electropolymerization process indicate that the size of the ions in the electrolyte affects the rate of the doping/dedoping process. The smaller the cation, the easier the doping/dedoping process, and the better the stability of the grown film. As demonstrated by Fourier transform infrared spectra, UV-vis spectra, and scanning electron microscopy, the obtained PAPBA is a cross-linked nanoporous polymer membrane that has a good adherence to the glassy carbon electrode.
Co-reporter:Jing Zhang, Xinxin Yu, Feixue Zou, Yaohua Zhong, Na Du, and Xirong Huang
ACS Sustainable Chemistry & Engineering 2015 Volume 3(Issue 12) pp:3338
Publication Date(Web):November 10, 2015
DOI:10.1021/acssuschemeng.5b01015
This report describes a dehydration of fructose into 5-hydroxymethylfurfural (HMF) promoted by ionic liquids [Bmim]Cl and [HNMP][CH3SO3] in ethanol solvent. Two intermediates captured in time-dependent HPLC determinations are identified and structurally characterized by in situ 1H NMR and online ESI(+)-MS/MS. Studies on the influence of the ionic liquids (ILs) on the formation and transformation of the intermediates indicate that [HNMP][CH3SO3] promotes the formation of the intermediates, while [Bmim]Cl promotes their transformation. The contribution of the component ions of the ILs to the dehydration originates from their activation toward the leaving of OH on fructose or the intermediates via the formation of multiple hydrogen bonds. This kind of weak interaction appears only at low temperature. On the basis of the present study and the related literature, we propose a concerted mechanism for the binary IL-promoted conversion of fructose into HMF at room temperature.Keywords: 5-Hydroxymethylfurfural; Concerted mechanism; Fructose; Hydrogen bond; Ionic liquids
Co-reporter:Feixue Zou, Xinxin Yu, Jing Zhang, Ni Cheng, Xirong Huang
Synthetic Metals 2015 Volume 204() pp:76-83
Publication Date(Web):June 2015
DOI:10.1016/j.synthmet.2015.03.015
•A novel proton functionalized RTIL–anilinium acetate is synthesized.•Electrosynthesis of PANI in [HANI]Ac runs at low onset potential and high rate.•Charge balancing counter-ion influences the anilinium oxidation onset potential.•The diffusion of PANI results in different CV signals under different conditions.•Triethylamine can tune the H+ level for the polymerization and therefore the rate.A novel proton functionalized room temperature ionic liquid–anilinium acetate ([HANI]Ac) with high ionic conductivity and low viscosity has been synthesized and used for the first time for aniline electropolymerization without any additives. The electropolymerization process reveals that the onset potential for anilinium oxidation (Eonset) in neat [HANI]Ac is +0.45 V vs. SCE, which is lower than those in aqueous and nonaqueous (ionic liquid as solvent/electrolyte) solutions. The control experiments and theoretical calculations indicate that the low Eonset in neat [HANI]Ac should be attributed to charge balancing counter-ion Ac−. Compared with [HANI]Ac/[BMIM]PF6 binary system, the mass transfer resistance of anilinium in neat [HANI]Ac is small, therefore the electropolymerization can be kept on at a high rate in a period. The cyclic voltammograms and Fourier transform infrared spectra demonstrate that the obtained PANI is highly conductive. The PANI has moderate solubility in [HANI]Ac and its adherence to the electrode is poor. During the electropolymerization, the accumulated PANI diffuses from the electrode/solution interface to the bulk phase which leads to different current signals of PANI under different conditions. Stirring slightly increases the oxidation current signal of anilinium but greatly reduces the redox current signal of PANI. Under quiescent conditions, lowering the upper switching potential reduces the redox current signal of PANI. The potential scan rate has great effect not only on the current signal of PANI but also on the redox peak shape. The electropolymerization process of [HANI]Ac in the presence of triethylamine further demonstrates that proton deficiency can result in a significant reduction of the rate of aniline polymerization.A novel proton functionalized room temperature ionic liquid anilinium acetate is synthesized and used for aniline electropolymerization without any additives.
Co-reporter:Keqian Yan, Yanwen Sun and Xirong Huang
RSC Advances 2014 vol. 4(Issue 61) pp:32363-32370
Publication Date(Web):08 Jul 2014
DOI:10.1039/C4RA04392H
The use of hydrophobic ionic liquids (ILs) as oil phases to formulate a H2O-in-IL (W/IL) microemulsion is of great significance to enzyme catalysis. In this report, we present the essential influence of the alkyl chain length of ILs on the phase behavior and the microstructure of H2O/IL/CnEm (polyoxyethylene alkyl ether) ternary systems. The ILs are [C4mim][PF6] (1-butyl-3-methylimidazolium hexafluorophosphate) and [C8mim][PF6] (1-octyl-3-methylimidazolium hexafluorophosphate). For a given nonionic surfactant, the alkyl chain length of ILs has an influence on the water solubilization capacity. The difference in the capacity, however, narrows and even disappears upon significant increase of the hydrophilic chain length of CnEm. FTIR spectroscopy and UV-Vis spectroscopy confirm the existence of bulk water in both [C4mim][PF6]- and [C8mim][PF6]-based C12E23-stabilized W/IL microemulsions. The catalytic activity of laccase hosted in the W/IL microemulsion and the dynamic light scattering measurement reveal that under the same conditions, the water droplet size dispersed in [C4mim][PF6] is larger than that in [C8mim][PF6]. To establish the newly developed W/IL microemulsion as an effective medium for laccase, a control study is presented, demonstrating that the W/IL microemulsion is superior to the pure ILs for the expression of the catalytic activity of laccase.
Co-reporter:Yan Hu;Yanwen Sun;Lu Lu ;Xirong Huang
Chinese Journal of Chemistry 2014 Volume 32( Issue 3) pp:263-268
Publication Date(Web):
DOI:10.1002/cjoc.201300899
Abstract
The ternary system of dodecylpyridinium bromide (DDPB)/acetone/H2O with appropriate composition can form a gel spontaneously and the gel is stable in hydrophobic ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate ([Bmim]PF6). Based on the gelation phenomenon we observed, the low molecular weight gelator (LMWG) was first tried to immobilize horseradish peroxidase (HRP) on glassy carbon electrode (GCE). The scanning electron microscope (SEM) images, the UV-Vis spectra and the bioactivity measurement indicate that the gel is suitable for the immobilization of HRP. The direct electrochemistry of the HRP-gel modified GCE (HRP-gel/GCE) in [Bmim]PF6 shows a pair of well-defined and quasi-reversible redox peaks with the heterogeneous electron transfer rate constant (ks) being 14.4 s−1, indicating that the direct electron transfer between HRP and GCE is fast. The HRP-gel/GCE is stable and reproducible. Also the electrode exhibits good electrocatalytic effect on the reduction of trichloroacetic acid (TCA), showing good promise in bioelectrocatalysis.
Co-reporter:Xinxin Yu;Yanwen Sun;Luyan Xue;Xirong Huang;Yinbo Qu
Topics in Catalysis 2014 Volume 57( Issue 10-13) pp:923-934
Publication Date(Web):2014 June
DOI:10.1007/s11244-014-0253-0
As media for an enzymatic reaction, ionic liquids (ILs) have many advantages over conventional molecular organic solvents, but some drawbacks still remain unsolved. In this review, we focus our attention on the various strategies that have been tried in recent years for improving the enzymatic performance in ILs. For clarity, this review is divided into several parts based on the hydrophilicity/hydrophobicity of ILs. For hydrophobic ILs, we put the emphasis on the construction of new macroscopically homogenous but microscopically heterogenous water-in-IL microemulsion systems and the catalytic performance of solubilized enzymes in them. For hydrophilic ILs, we highlight the enzyme performance related Hofmeister anions or cations series and the surface active effect of ILs.
Co-reporter:Jing Zhang;Feixue Zou;Xinxin Yu;Xirong Huang;Yinbo Qu
Colloid and Polymer Science 2014 Volume 292( Issue 10) pp:2549-2554
Publication Date(Web):2014 October
DOI:10.1007/s00396-014-3301-1
The laccase-catalyzed polymerization of aniline in sodium dodecyl benzene sulfonate (SDBS) micellar solution was studied in the absence and presence of an ionic liquid tetramethylammonium trifluoromethanesulfonate ([TMA]TfO). It was found that [TMA]TfO was able to lessen the negative effect of SDBS on the laccase activity, especially at high levels, and prevent the association of anilinium cation and SDBS anion. It was also found that low level of [TMA]TfO is beneficial to the synthesis of conducting polyaniline (PANI) probably due to the extension of the lifetime of aniline cation radicals by [TMA]TfO. In the presence of [TMA]TfO, all the polymerization systems were visually clear, and a maximum yield of water-soluble conducting PANI could be obtained at low level of [TMA]TfO and near the critical micelle concentration of SDBS.
Co-reporter:Yanwen Sun, Keqian Yan, Xirong Huang
Colloids and Surfaces B: Biointerfaces 2014 Volume 122() pp:66-71
Publication Date(Web):1 October 2014
DOI:10.1016/j.colsurfb.2014.06.040
•[C14mim]Br/Triton X-100/H2O/[Bmim]PF6 forms a large single phase region.•A novel W/IL microemulsion with positively charged membrane was demonstrated.•Laccase solubilized in the W/IL microemulsion is catalytically active.•The laccase activity depends on the charge and composition of the membrane.The phase behavior of the pseudo ternary system 1-tetradecyl-3-methylimidazolium bromide ([C14mim]Br)/Triton X-100/H2O/1-butyl-3-methylimidazolium hexafluorophosphate ([Bmim]PF6) has been studied at 35 °C. With the increase in the mole fraction of Triton X-100 in the mixed surfactants, the water solubilization capacity increases and the monophasic area enlarges. The H2O-in-[Bmim]PF6 (W/IL) microemulsion was identified via electrical conductivity measurement. The existence of bulk water in the W/IL microemulsion was demonstrated based on the change of the O-D vibration frequency with content of D2O added and confirmed using UV–vis technique with CoCl2 as probe. Laccase can be solubilized in the W/IL microemulsion and exhibits a catalytic activity. The interface of the W/IL microemulsion has an inhibitory effect on the expression of the laccase activity, and the inhibitory effect is varied with the molar ratio of the mixed surfactants.
Co-reporter:Ying Li;Xirong Huang;Yinbo Qu
Journal of Chemical Technology and Biotechnology 2013 Volume 88( Issue 12) pp:2227-2232
Publication Date(Web):
DOI:10.1002/jctb.4091
Abstract
BACKGROUND
The immobilization of biomacromolecules on carbon nanotubes has attracted considerable attention. Based on the specific affinity between concanavalin A (Con A) and glycosyl, and the ability of alkyl polyglucoside to disperse single-walled carbon nanotubes (SWNTs), a new self-assembly immobilization strategy is developed.
RESULTS
Using laccase (Lac) and horseradish peroxidase (HRP) as models, it is demonstrated that this new self-assembly immobilization strategy has obvious advantages over the direct adsorption immobilization strategy in enzyme loadings ( 1.34-fold (Lac) and 1.46-fold (HRP) higher) and in the specific activity ( 5.06-fold (Lac) and 4.77-fold (HRP) higher). Circular dichroism (CD) spectra and fluorescence spectra also indicate that the present new indirect immobilization strategy has less impact on the enzyme conformation compared with the direct adsorption strategy. For the catalytic oxidation of dibenzothiophene (DBT), the immobilized HRP prepared using the present self-assembly strategy was more effective than that using the direct adsorption strategy.
CONCLUSION
Based on these findings, it is concluded that the present self-assembly strategy can greatly improve the enzymatic properties of the immobilized enzymes. © 2013 Society of Chemical Industry
Co-reporter:Yin Zhao, Keqian Yan, Xirong Huang, Zhonghua Zhang, Yinbo Qu
Chemical Physics Letters 2013 Volume 555() pp:178-181
Publication Date(Web):3 January 2013
DOI:10.1016/j.cplett.2012.10.077
Abstract
On monolithic nanoporous silver (NPS), via DNA hybridization, we constructed an NPS/DNA-Cy5/silver nanoparticle (Ag NP) sandwich to investigate its SERS effect. In this sandwich, no chemical enhancement contributes to the SERS signal of Cy5. As compared with NPS, the present substrate exhibits particularly strong electromagnetic (EM) field enhancement. At the same Ag NPs surface loading, the SERS intensity decreases exponentially with increasing the length of double-stranded DNA (dsDNA). A larger pore size of NPS leads to weaker EM enhancement within the sandwich, but the relative intensity is not sensitive to the sizes and it is determined by the length of dsDNA.
Co-reporter:Feixue Zou, Luyan Xue, Xinxin Yu, Ying Li, Yin Zhao, Lu Lu, Xirong Huang, Yinbo Qu
Colloids and Surfaces A: Physicochemical and Engineering Aspects 2013 Volume 429() pp:38-43
Publication Date(Web):20 July 2013
DOI:10.1016/j.colsurfa.2013.03.054
•HRP catalyzed polymerization of aniline was carried out first in AOT micelle.•As dopant and dispersant, AOT has small negative effect on HRP activity.•As a biocatalyst, HRP could induce the formation of chiral polyaniline.•Chiral, conducting and water soluble polyaniline was biosynthesized in one step.Horseradish peroxidase (HRP)/H2O2-triggered polymerization of aniline in sodium bis-(2-ethylhexyl)sulfosuccinate (AOT) micellar solution is first presented. Results show that the critical micelle concentration of AOT in the polymerization system is very low and AOT has small effect on the activity of HRP, so it matches with HRP well for the end. As a template, the AOT micellar solution is essential for the formation of conducting polyaniline. In the present system, AOT also acts as a dopant and a dispersant, leading to the formation of conducting and water soluble polyaniline. Optimization of the pH and the H2O2 concentration results in more conducting polyaniline. During investigation, it was found that HRP itself can induce the formation of chiral polyaniline without any other chiral inducer. In short, with the aid of AOT, one-step biosynthesis of chiral, conducting and water soluble polyaniline using HRP as both catalyst and chiral inducer is realized. Compared with other aniline polymerization systems reported elsewhere, the present system shows many advantages. It needs less templates and no foreign chiral inducer while the synthesized polyaniline has good dispersibility and high electrical conductivity.
Co-reporter:Luyan Xue, Yin Zhao, Lijie Yu, Yanwen Sun, Keqian Yan, Ying Li, Xirong Huang, Yinbo Qu
Colloids and Surfaces B: Biointerfaces 2013 Volume 105() pp:81-86
Publication Date(Web):1 May 2013
DOI:10.1016/j.colsurfb.2012.12.050
Choline acetate is an ionic liquid composed of a kosmotropic anion and a chaotropic cation. According to Hofmeister series, a kosmotropic anion and/or a chaotropic cation could stabilize an enzyme, thereby facilitating the retention of the catalytic activity of the enzyme. In this work, we first report the influence of choline acetate on the activity and stability of lipase in AOT/water/isooctane reverse micelles. The indicator reaction is the lipase-catalyzed hydrolysis of 4-nitrophenyl butyrate. The results show that a low level of choline acetate does not affect the microstructure of the AOT reverse micelles, but the ionic liquid can improve the catalytic efficiency of lipase. Fluorescence spectra show that a high level of choline acetate has an impact on the conformation of lipase, so the activation is mainly due to the influence of choline acetate on the nucleophilicity of water. Infrared spectra demonstrate that choline acetate can form stronger hydrogen bonds with water surrounding lipase, and therefore enhance the nucleophilicity of the water, which makes it easier to attack the acyl enzyme intermediate, thereby increasing the activity of the lipase-catalyzed hydrolysis of the ester. A study on the stability of lipase in AOT reverse micelles indicates that the ionic liquid is able to maintain the activity of lipase to a certain extent. The effect of choline acetate is consistent with that predicted based on Hofmeister series.Graphical abstractHighlights► Choline acetate improves the hydrolysis efficiency of lipase in AOT reverse micelle. ► Low level of choline acetate does not affect the conformation of lipase. ► Nucleophilicity of water can be enhanced by choline acetate. ► As predicted based on Hofmeister series, choline acetate can stabilize lipase in reverse micelles.
Co-reporter:Luyan Xue, Ying Li, Feixue Zou, Lu Lu, Yin Zhao, Xirong Huang, Yinbo Qu
Colloids and Surfaces B: Biointerfaces 2012 Volume 92() pp:360-366
Publication Date(Web):1 April 2012
DOI:10.1016/j.colsurfb.2011.12.019
In the water-in-[Bmim][PF6] microemulsion stabilized by both AOT and Triton X-100, the lipase-catalyzed hydrolysis of 4-nitrophenyl butyrate (p-NPB) was investigated to evaluate the catalytic efficiency of lipase in this novel microemulsion. The structural parameters of the microemulsion and the conditions of the enzymatic reaction affect the catalytic activity of lipase, especially the concentration of Tris–HCl buffer. Under optimum conditions, the catalytic activity of lipase in the present microemulsion is much higher than that in H2O saturated [Bmim][PF6]. When the partitioning of the substrate in the microemulsion is taken into account, the catalytic efficiency of lipase in this novel microemulsion is 14.3 times that in H2O saturated [Bmim][PF6] due to the significant decrease of the Michaelis constant in the microemulsion. Due to the large interface, high water activity, and probably the activating effect of the imidazolium cation in the water pool, the present microemulsion is demonstrated to be a promising medium for the lipase-catalyzed hydrolytic reaction. To demonstrate an important biocatalytic application in the IL-based microemulsion, the lipase-catalyzed synthesis of the flavoring agent benzyl acetate via transesterification of vinyl acetate with benzyl alcohol was also studied in the medium. Due to the high dispersion of lipase, large interface and removal of the byproduct, a maximum yield of 94% was obtained, indicating that the novel microemulsion is really important and useful.Graphical abstractHighlights► The structural parameters of the microemulsion and the conditions of the enzymatic reaction affect the activity of lipase. ► The catalytic efficiency of lipase in the microemulsion is 14.3 times that in H2O saturated [Bmim][PF6]. ► The imidazolium cation in the microemulsion has activating effect on the lipase-catalyzed hydrolytic reaction. ► The microemulsion is a good medium for the synthesis of benzyl acetate via transesterification.
Co-reporter:Lu Lu, Yan Hu, Xirong Huang, and Yinbo Qu
The Journal of Physical Chemistry B 2012 Volume 116(Issue 36) pp:11075-11080
Publication Date(Web):August 16, 2012
DOI:10.1021/jp3054263
It is imperative to establish a simple, efficient, and practical method to investigate the Hofmeister effect of ionic liquids (ILs) on the behavior of proteins (enzymes). In this study, the effects of the cations and anions of different ILs in aqueous media on the structural stability of horseradish peroxidase (HRP), a model oxidoreductase, were systematically investigated using electrochemical methods. It is found that without ILs no direct electron transfer current signals of HRP appear at bare glassy carbon electrode (GCE) in phosphate buffer (pH 7.0) even after incubation and accumulation at a negative potential. In the presence of ILs, however, a current signal occurs at GCE, depending on the structure of the IL and its concentration. A linear relationship between the peak currents and the scan rates demonstrates that the direct electron transfer is a surface-confined thin-layer electrochemical process. The redox signal at GCE is from the heme of HRP. An IL has a perturbing effect on the HRP structure. The anodic peak current of HRP at GCE, the catalytic activity of HRP, and the secondary structure of HRP are well correlated. Different cations or anions at varied concentrations have different effects on the structural stability of HRP, resulting in different current signals at GCE. Thus, the anodic peak current of HRP at GCE can be used as an indicator to quantitatively characterize the effect of ILs on the structural stability of HRP. The present Hofmeister series for cations and anions is in good agreement with that reported elsewhere. To our knowledge, this is a first attempt to establish a simple and practical electrochemical method to correlate Hofmeister effects with characteristics of ions and solvents. The present investigation not only deepens our understanding of the complex electrochemical behavior of proteins in ILs media but also offers a practical guidance to designing “green” and biocompatible ILs for protein (enzyme) separation, purification, and enzymatic catalysis and conversion.
Co-reporter:Lu Lu;Xirong Huang;Yinbo Qu
Journal of Solid State Electrochemistry 2012 Volume 16( Issue 10) pp:3299-3305
Publication Date(Web):2012 October
DOI:10.1007/s10008-012-1772-x
A new carbon ionic liquid electrode (CILE) has been constructed using a low melting point (39 °C) hydrophobic ionic liquid (IL) 1-propyl-3-methylimidazolium hexafluorophosphate ([Pmim][PF6]) as the binder. Both cyclic voltammetry and electrochemical impedance spectroscopy demonstrate that, in addition to the composition optimization of the IL/graphite composite, heating the composite at a temperature a little higher than the melting point of [Pmim][PF6] can also lower the background current and enhance the mechanical strength of the CILE. The heated CILE is more sensitive than the traditional carbon paste electrode for the detection of H2O2. Glucose oxidase (GOx) can be easily entrapped in the bulk IL/graphite composite. Heating the GOx-modified CILE (GOx-CILE) at the melting point of [Pmim][PF6] does not lower the catalytic activity of GOx. As compared with n-octylpyridinium hexafluorophosphate (melting point 65 °C) as the binder, [Pmim][PF6]-based CILE is much better in signal-to-noise ratio. Under the optimum conditions, the [Pmim][PF6]-based GOx-CILE has a linear amperometric response to glucose over a concentration range of 2.0–26 mM with the detection limit as low as 0.39 mM. It follows that choosing an IL with a melting point of ca. 40 °C as a binder to fabricate enzyme-entrapped CILEs is a good strategy for the enhancement of the performance of the electrode.
Co-reporter:Lu Lu;Xirong Huang
Microchimica Acta 2011 Volume 175( Issue 1-2) pp:
Publication Date(Web):2011 October
DOI:10.1007/s00604-011-0663-7
We describe a facile electrochemical route for the synthesis of CuO flower-like microspheres (CuO FMs) by anodic dissolution of bulk Cu in sodium hydroxide solution at room temperature and without heating. Scanning electron microscopy and X-ray diffraction revealed that the CuO FMs are phase-pure monoclinic crystallites and comprised of CuO nanoflakes. The concentration of NaOH has a large effect on the size of the CuO FMs. The possible formation mechanism is discussed. The CuO FMs are electrocatalytically active towards the oxidation of H2O2, and this has resulted in a sensor for H2O2. To our knowledge, this is the simplest way to obtain clean CuO FMs.
Co-reporter:Luyan Xue, Huajun Qiu, Ying Li, Lu Lu, Xirong Huang, Yinbo Qu
Colloids and Surfaces B: Biointerfaces 2011 Volume 82(Issue 2) pp:432-437
Publication Date(Web):1 February 2011
DOI:10.1016/j.colsurfb.2010.09.016
It is of great significance to develop an appropriate water-in-ionic liquid (W/IL) microemulsion suitable for the expression of the catalytic activity of a given enzyme. In this paper, the phase diagram of a new AOT/Triton X-100/H2O/[Bmim][PF6] pseudo ternary system is presented. With the aid of nonionic surfactant Triton X-100, AOT could be dissolved in hydrophobic ionic liquid [Bmim][PF6], forming a large single phase microemulsion region. The water-in-[Bmim][PF6] (W/IL) microemulsion domain was identified electrochemically by using K3Fe(CN)6 as a probe. The existence of W/IL microemulsions was demonstrated spectrophotometrically by using CoCl2 as a probe. New evidences from the FTIR spectroscopic study, which was first introduced to the W/IL microemulsion by substituting D2O for H2O to eliminate the spectral interference, demonstrated that there existed bulk water at larger ω0 values (ω0 was defined as the molar ratio of water to the total surfactant) in the W/IL microemulsion, which had remained unclear before. In addition to the inorganic salts, biomacromolecule laccase could be solubilized in the W/IL microemulsion. The laccase hosted in the microemulsion exhibited a catalytic activity and the activity could be regulated by the composition of the interfacial membrane.
Co-reporter:Lu Lu, Xirong Huang, Yinbo Qu
Colloids and Surfaces B: Biointerfaces 2011 Volume 87(Issue 1) pp:61-66
Publication Date(Web):1 October 2011
DOI:10.1016/j.colsurfb.2011.04.037
The direct electrochemistry and bioelectrocatalysis of horseradish peroxidase (HRP) in Nafion films at glassy carbon electrode (GCE) was investigated in three [BF4]−-type room-temperature ionic liquids (ILs) to understand the structural effect of imidazolium cations. The three ILs are 1-ethyl-3-methylimidazolium tetrafluoroborate ([Emim][BF4]), 1-butyl-3-methylimidazolium tetrafluoroborate ([Bmim][BF4]) and 1-hexyl-3-methylimidazolium tetrafluoroborate ([Hmim][BF4]). A small amount of water in the three ILs is indispensable for maintaining the electrochemical activity of HRP in Nafion films, and the optimum water contents decrease with the increase of alkyl chain length on imidazole ring. Analysis shows that the optimum water contents are primarily determined by the hydrophilicity of ILs used. In contrast to aqueous medium, ILs media facilitate the direct electron transfer of HRP, and the electrochemical parameters obtained in different ILs are obviously related to the nature of ILs. The direct electron transfer between HRP and GCE is a surface-confined quasi-reversible single electron transfer process. The apparent heterogeneous electron transfer rate constant decreases gradually with the increase of alkyl chain length on imidazole ring, but the changing extent is relatively small. The electrocatalytic reduction current of H2O2 at the present electrode decreases obviously with the increase of alkyl chain length, and the mass transfer of H2O2 via diffusion in ILs should be responsible for the change. In addition, the modified electrode has good stability and reproducibility; the ability to tolerate high levels of F− has been greatly enhanced due to the use of Nafion film. When an appropriate mediator is included in the sensing layer, a sensitive nonaqueous biosensor could be fabricated.Graphical abstractImidazoliums with different alkyl groups as supporting electrolytes affect the direct electrochemistry and electrocatalysis of horseradish peroxidase (HRP) in Nafion film.Highlights► [BF4]−-type ionic liquids (ILs) with different alkyl groups on imidazole ring as supporting electrolytes. ► The HRP electrode without any mediators facilitates the clarification of the single effect of ILs on the direct electrochemistry and electrocatalysis. ► Nafion film rejects [BF4]−, highlights the effect of cations and reduces the potential interference of F−.
Co-reporter:Dr. Huajun Qiu; Zhonghua Zhang; Xirong Huang; Yinbo Qu
ChemPhysChem 2011 Volume 12( Issue 11) pp:2118-2123
Publication Date(Web):
DOI:10.1002/cphc.201100205
Abstract
Sensitive detection of molecules by using the surface-enhanced Raman scattering (SERS) technique depends on the nanostructured metallic substrate and many efforts have been devoted to the preparation of SERS substrates with high sensitivity, stability, and reproducibility. Herein, we report on the fabrication of stable monolithic nanoporous silver (NPS) by chemical dealloying of Ag–Al precursor alloys with an emphasis on the effect of structural evolution on SERS signals. It was found that the dealloying conditions had great influence on the morphology (the ligament/pore size) and the crystallization status, which determined the SERS signal of rhodamine 6G on the NPS. NPS with small pores, low residual Al, and perfect crystallization gave high SERS signals. A high enhancement factor of 7.5×105 was observed on bare NPS obtained by dealloying Ag30Al70 in 2.5 wt % HCl at room temperature followed by 15 min aging at around 85 °C. After coating Ag nanoparticles on the NPS surface, the enhancement factor increased to 1.6×108 owing to strong near-field coupling between the ligaments and nanoparticles.
Co-reporter:Huajun Qiu, Lu Lu, Xirong Huang, Yinbo Qu
Electrochimica Acta 2010 Volume 56(Issue 1) pp:291-296
Publication Date(Web):15 December 2010
DOI:10.1016/j.electacta.2010.08.081
In this work, a facile electrochemical route i.e., anodic dissolution of bulk Cu at 2.0 V or more (vs. SCE) in a NaOH solution containing NH2OH·HCl, was introduced for the synthesis of clean Cu2O microcrystals (Cu2O MCs) with morphologies of octahedron, half circular plate, etc. The bulk Cu electrode can be facilely dispersed into Cu(OH)42− in alkaline solutions with the help of intense O2 releasing. In the presence of reductive NH2OH·HCl, Cu(II) was quickly reduced to Cu(I). Due to the concentration gradient of Cu(I) and OH− resulting from the electrochemical reaction and the selective adsorption of OH− on different crystal facets, half circular plate Cu2O MCs were for the first time, synthesized. By changing the NaOH concentration or applied potential, octahedron and rectangular plate Cu2O MCs could also be obtained. Scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray diffraction (XRD) techniques, etc. were used to characterize the oxides. The Cu2O MCs were phase-pure cubic Cu2O. This electrochemical route is simple, basically green and can be used to synthesize Cu2O MCs with different morphologies.
Co-reporter:Huajun Qiu, Lu Lu, Luyan Xue, Xirong Huang
Electrochimica Acta 2010 Volume 55(Issue 20) pp:6081-6087
Publication Date(Web):1 August 2010
DOI:10.1016/j.electacta.2010.05.069
A 3-dimentional (3D) micro-nano hierarchical porous Cu film was fabricated by surface rebuilding of smooth Cu substrates in a blank solution of 1 M NaOH with square wave potential perturbation. The potential step from 0.4 to −2.5 V (vs. SCE) and a frequency of 50 Hz were chosen for the fabrication. The pore formation and Cu nanostructure evolution were characterized by scanning electron microscopy. The fabrication process involved fast Cu electrochemical oxidation–reduction and suitable rate of H2 releasing. During the repeated Cu oxidation–reduction, the Cu atoms were removable, forming dendrite-like structures. At the same time, the formed H2 bubbles acted as a dynamic template to shape the formation of micropores. The effect of H2 bubble as a template on the size of the formed micropores was demonstrated by adding a small amount of surfactant (cetyltrimethylammonium bromide, CTAB) into the basic solution to adjust the size of the bubbles. The as-prepared 3D porous Cu showed high electrocatalytic activity toward the reduction of NO3− and H2O2. The present in situ preparation method was green, convenient and required neither Cu(II) species and additives in solution nor post-treatment for template removal.
Co-reporter:Huajun Qiu, Xirong Huang
Journal of Electroanalytical Chemistry 2010 Volume 643(1–2) pp:39-45
Publication Date(Web):1 May 2010
DOI:10.1016/j.jelechem.2010.03.011
A nonenzymatic amperometric glucose sensor was fabricated based on the electrocatalytic oxidation of nanoporous gold (NPG) toward glucose. The NPG electrode was in situ prepared by a facile one-step square wave potential pulse (SWPP) treatment. The surface morphology of the NPG-based electrode was characterized by scan electron microscopy. Voltammetry and amperometric methods were used to evaluate the electrocatalytic activities of the NPG-based electrodes toward the glucose oxidation in both neutral and alkaline media. The NPG electrode showed a quick and sensitive response to glucose. The electrocatalytic activity of NPG in neutral condition was further improved when a small amount of Pt was decorated on NPG (NPG–Pt). When applied for glucose sensing, the NPG–Pt electrode showed a linear range of 0.5–10 mM with a sensitivity of 145.7 μA cm−2 mM−1 and a detection limit of 0.6 μM (S/N = 3). The physiological levels of ascorbic acid (0.1 mM) and uric acid (0.02 mM) only had negligible interferences to the glucose detection. The high sensitivity and selectivity of the present sensor was due to the high roughness factor of the electrode surface and unique electrooxidation mechanism of glucose. In addition, the present nonenzymatic glucose sensor was easy in preparation and very stable.
Co-reporter:Huajun Qiu, Yanli Sun, Xirong Huang, Yinbo Qu
Colloids and Surfaces B: Biointerfaces 2010 Volume 79(Issue 1) pp:304-308
Publication Date(Web):1 August 2010
DOI:10.1016/j.colsurfb.2010.04.017
An attempt was made in the present paper to develop a nanoporous gold (NPG)-based electrochemical aptasensor for thrombin detection. The substrate electrode NPG was in situ fabricated by a facile one-step square wave potential pulse (SWPP) treatment. The treatment involved repeated gold oxidation–reduction and intensive H2 bubbles evolution. After 100 min treatment, the active surface area of Au increased greatly (34 times). The electrochemical aptasensor was fabricated using a layer-by-layer assembling strategy. A “sandwich” structure was formed via thrombin connecting the aptamer-modified NPG and the aptamer-modified Au nanoparticles (AuNPs). The AuNPs was modified with two kinds of single strand DNA (ssDNA). One was aptamer of thrombin, but the other was not, reducing the cross-reaction between thrombin and its aptamer on the same AuNP. The electrochemical signal produced by the [Ru(NH3)6]3+ bound to ssDNA via electrostatic interaction was measured by chronocoulometry. Due to the amplification effects of both NPG and AuNPs, this novel NPG-based aptasensor could detect thrombin quantitatively in the range of 0.01–22 nM with a detection limit as low as 30 fM. The present aptasensor also exhibited excellent selectivity, stability and reusability.
Co-reporter:Hua-Jun Qiu, Gui-Ping Zhou, Guang-Lei Ji, Yun Zhang, Xi-Rong Huang, Yi Ding
Colloids and Surfaces B: Biointerfaces 2009 Volume 69(Issue 1) pp:105-108
Publication Date(Web):15 February 2009
DOI:10.1016/j.colsurfb.2008.11.007
The electrochemical detection of dopamine (DA) at conventional solid electrodes was interfered by the coexisted ascorbic acid (AA). To circumvent this problem, many modified electrodes were tried. In this paper, an attempt was made to use nanoporous gold (NPG) as modifying materials. The NPGs with different pore sizes were prepared simply by dealloying Ag from Au/Ag alloy with concentrated nitric acid. The glassy carbon electrode (GCE) based modified electrode was fabricated by simply affixing the NPG film on the surface of a GCE. The electrochemical behaviors of AA and DA at the modified electrode were studied. The results indicated that the NPG/GCE exhibited substantial enhancement in electrochemical sensitivity for DA and AA due to its large surface area. Results also showed that the oxidation of AA at the electrode was a diffusion-controlled process, but for DA it was an adsorption-controlled process. This result, together with the different anodic peak potentials of the two species, made it possible the selective determination of DA in the presence of AA. Due to the interaction of the amino group of DA with the surface of nanoscale gold, DA could be accumulated on the NPG/GCE, while AA could not. This permitted the coexistence of large amount of AA. When differential pulse voltammetry (DPV) was used, a submicrolevel of DA could be detected in the millimolar level of AA with a detection limit of 17 nM at a signal-to-noise ratio of 3. In a word, the modified electrode showed good sensitivity, selectivity and reproducibility.
Co-reporter:Huajun Qiu, Luyan Xue, Guanglei Ji, Guiping Zhou, Xirong Huang, Yinbo Qu, Peiji Gao
Biosensors and Bioelectronics 2009 Volume 24(Issue 10) pp:3014-3018
Publication Date(Web):15 June 2009
DOI:10.1016/j.bios.2009.03.011
On the basis of the unique physical and chemical properties of nanoporous gold (NPG), which was obtained simply by dealloying Ag from Au/Ag alloy, an attempt was made in the present study to develop NPG-based electrochemical biosensors. The NPG-modified glassy carbon electrode (NPG/GCE) exhibited high-electrocatalytic activity toward the oxidation of nicotinamide adenine dinucleotide (NADH) and hydrogen peroxide (H2O2), which resulted in a remarkable decrease in the overpotential of NADH and H2O2 electro-oxidation when compared with the gold sheet electrode. The high density of edge-plane-like defective sites and large specific surface area of NPG should be responsible for the electrocatalytic behavior. Such electrocatalytic behavior of the NPG/GCE permitted effective low-potential amperometric biosensing of ethanol or glucose via the incorporation of alcohol dehydrogenase (ADH) or glucose oxidase (GOD) within the three-dimensional matrix of NPG. The ADH- and GOD-modified NPG-based biosensors showed good analytical performance for biosensing ethanol and glucose due to the clean, reproducible and uniformly distributed microstructure of NPG. The stabilization effect of NPG on the incorporated enzymes also made the constructed biosensors very stable. After 1 month storage at 4 °C, the ADH- and GOD-based biosensors lost only 5.0% and 4.2% of the original current response. All these indicated that NPG was a promising electrode material for biosensors construction.
Co-reporter:Huajun Qiu, Caixia Xu, Xirong Huang, Yi Ding, Yinbo Qu and Peiji Gao
The Journal of Physical Chemistry C 2009 Volume 113(Issue 6) pp:2521-2525
Publication Date(Web):2017-2-22
DOI:10.1021/jp8090304
Nanoporous gold (NPG), prepared simply by dealloying Ag from Au/Ag alloy, was used in the present study as a carrier for laccase immobilization. Three immobilization strategies, i.e., physical adsorption, electrostatic attraction, and covalent coupling, were used to immobilize laccase on NPG. A detailed comparison among the three strategies was made in light of the loading, the specific activity, and the leakage of laccase. The present results indicated that the physical adsorption strategy was the best one for laccase immobilization on NPG. This was because of the potential covalent linkage between the nanoscale gold surface and the amino groups of the residue amino acids of laccase. The effects of the particle size of NPG on laccase loading and enzyme kinetics were also investigated. When the particle size of NPG got smaller, more laccase could access the inner pore and be immobilized. The kinetic study showed that the crushed NPG not only enhanced mass transfer of the substrate and its oxidation product but also favored the exposure of the active sites of the immobilized laccase to the substrate, i.e., the crushing facilitated the enhancement of the catalytic efficiency of laccase.
Co-reporter:Yun Zhang;Xirong Huang;Guanglei Ji;Ying Li
Central European Journal of Chemistry 2009 Volume 7( Issue 4) pp:
Publication Date(Web):2009 December
DOI:10.2478/s11532-009-0069-0
Yeast alcohol dehydrogenase (YADH) showed substantial decrease in its catalytic activity due to the strong electrostatic interaction between the head groups of sodium bis(2-ethylhexyl) sulfosuccinate (AOT) and YADH in AOT reverse micelles. However, the catalytic activity of YADH in a nonionic reverse micellar interface (GGDE/TX-100) obtained from a functional nonionic surfactant N-gluconyl glutamic acid didecyl ester (GGDE) and Triton X-100 (TX-100) was higher than that in AOT reverse micelle under the respective optimum conditions. A comparison of the kinetic parameters showed that the turnover number kcat in GGDE/TX-100 reverse micelle was 1.4 times as large as that in AOT reverse micelle, but the Michaelis constants in AOT reverse micelle for ethanol KmB was twice and for coenzyme NAD+ KmA was 5 times higher than their counterparts in GGDE/TX-100 reverse micelle. For the conversion of ethanol, the smaller KmB and larger kcat in GGDE/TX-100 reverse micelle resulted in higher catalytic efficiency kcat/KmB. The stability of YADH in GGDE/TX-100 reverse micelle was also found to be better than that in AOT reverse micelle. They were mainly attributed to the absence of electric charge on the head groups of GGDE and TX-100 in the GGDE/TX-100 reverse micelle.
Co-reporter:Jing Lan;Yun Zhang;Xirong Huang;Ming Hu;Weifeng Liu;Yuezhong Li;Yinbo Qu;Peiji Gao
Journal of Chemical Technology and Biotechnology 2008 Volume 83( Issue 1) pp:64-70
Publication Date(Web):
DOI:10.1002/jctb.1783
Abstract
BACKGROUND: Anionic surfactant sodium bis (2-ethylhexyl) sulfosuccinate (AOT) had an inhibiting effect on lignin peroxidase (LiP). To improve the catalytic activity of LiP in an AOT reversed micelle in isooctane, nonionic surfactant polyoxyethylene lauryl ether (Brij30) was incorporated into the interfacial membrane. H2O2 played dual roles in the LiP-catalyzed oxidation of substrates. To obtain a sustainable high activity of LiP, a coupled enzymatic reaction, i.e. the glucose oxidase (GOD)-catalyzed oxidation of glucose was used as an H2O2 source.
RESULTS: Owing to modification of the charge density of the interfacial membrane, the activity of LiP in an optimized AOT/Brij30 reversed micellar medium (χB (the molar percentage of Brij30) = 0.53, ω0 ([H2O]/([AOT] + [Brij30]) = 23, pH = 4.8) was 40 times that in a single AOT reversed micelle. Due to the controlled release of H2O2, the concentration of H2O2 in the mixed reversed micellar medium was maintained at a moderately high level throughout, which made the LiP-catalyzed oxidation of substrates proceed at a higher conversion rate than counterparts in which H2O2 was supplied externally in one batch at the beginning of the reaction. Decolourization of two waterless-soluble aromatic dyes (pyrogallol red and bromopyrogallol red) using LiP coupled with GOD in the medium also demonstrated that a higher decolourization percentage was obtained if H2O2 was supplied enzymatically.
CONCLUSION: The proposed measures (both physicochemical and biochemical) were very effective, giving significant improvement in the catalytic performance of LiP in a single AOT reversed micelle in isooctane, which helped to degrade or transform hydrophobic aromatic compounds with LiP in reversed micelles more efficiently. Copyright © 2007 Society of Chemical Industry
Co-reporter:Yun Zhang;Xirong Huang;Yuezhong Li
Journal of Chemical Technology and Biotechnology 2008 Volume 83( Issue 9) pp:1230-1235
Publication Date(Web):
DOI:10.1002/jctb.1931
Abstract
BACKGROUND: [bmim][PF6] is a hydrophobic ionic liquid which could be considered as an environmentally friendly solvent for biocatalysis. In pure [bmim][PF6], however, alcohol dehydrogenase from yeast (YADH) has no catalytic activity. The aim of the present work was (1) to quantitatively study the negative effect of [bmim][PF6] on the catalytic activity of YADH and the related mechanism and (2) to made an attempt to lessen the negative effect of [bmim][PF6] on YADH by microemulsifying [bmim][PF6].
RESULTS: The activity of YADH in the homogeneous solution formed by H2O, CH3CH2OH and [bmim][PF6] decreased rapidly with the increase of the molar fraction of [bmim][PF6]. The inhibitory effect of [bmim][PF6] on YADH was probably caused by the competition of the imidazole group of [bmim][PF6] with the coenzyme NAD+ for the binding sites on YADH. In a water-in-[bmim][PF6] microemulsion, YADH was catalytically active due to the formation of the interfacial membrane of the nonionic surfactant TritonX-100, which separated YADH from [bmim][PF6] and avoided the direct inactivation of [bmim][PF6] on YADH. Under optimal conditions, the activity of YADH was as high as 51 µmol L−1 min−1.
CONCLUSION: [bmim][PF6] was an inhibitor of YADH and its negative effect on YADH could be lessened by its microemulsification. Copyright © 2008 Society of Chemical Industry
Co-reporter:Huajun Qiu ; Caixia Xu ; Xirong Huang ; Yi Ding ; Yinbo Qu ;Peiji Gao
The Journal of Physical Chemistry C 2008 Volume 112(Issue 38) pp:14781-14785
Publication Date(Web):August 30, 2008
DOI:10.1021/jp805600k
Nanoporous gold (NPG) with different pore sizes was obtained by simple dealloying and thermal annealing methods. The morphology of the NPG was characterized by scanning electron microscopy and nitrogen adsorption technique. Laccase was immobilized on the surface of the NPG by physical adsorption. Detailed studies were made on the effect of the pore size on laccase immobilization. NPG with pore size of 40−50 nm was demonstrated to be a suitable support for laccase immobilization. Compared with free enzyme, the optimum pH of immobilized laccase did not change; the optimum temperature, however, rose from 40 to 60 °C. Both thermal and storage stabilities of laccase improved markedly via the immobilization. Laccase immobilized on NPG (100 nm in thickness) was used for enzyme electrode construction. Direct electrochemistry of laccase on NPG supported by glassy carbon electrode (NPG/GC) was achieved with high efficiency due to the outstanding physicochemical characteristics of the NPG. The laccase-loaded NPG/GC electrode also exhibited a strong electrocatalytic activity toward O2 reduction. When stored at 4 °C for 1 month, the electrode showed no obvious changes in its response. All results presented in the paper indicated that NPG was an excellent carrier for laccase immobilization and would have potential applications in biofuel cell and/or biosensor areas.
Co-reporter:Gui-Ping Zhou, Yun Zhang, Xi-Rong Huang, Chuan-Hong Shi, Wei-Feng Liu, Yue-Zhong Li, Yin-Bo Qu, Pei-Ji Gao
Colloids and Surfaces B: Biointerfaces 2008 Volume 66(Issue 1) pp:146-149
Publication Date(Web):1 October 2008
DOI:10.1016/j.colsurfb.2008.05.016
For hydrophobic ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF6]), an H2O-in-[BMIM][PF6] microemulsion could be formed in the presence of nonionic surfactant Triton X-100 (TX-100). In such a medium, both lignin peroxidase (LiP) and laccase could express their catalytic activity with the optimum molar ratio of H2O to TX-100 at 8.0 for LiP and >20 for laccase, and the optimum pH values at 3.2 for LiP and 4.2 for laccase, respectively. As compared with pure or water saturated [BMIM][PF6], in which the two oxidases had negligible catalytic activity due to the strong inactivating effect of [BMIM][PF6] on both enzymes, the use of the [BMIM][PF6]-based microemulsion had some advantages. Not only the catalytic activities of both fungal oxidases greatly enhanced, but also the apparent viscosity of the medium decreased.
Co-reporter:Yun Zhang, Xi-Rong Huang, Feng Huang, Yue-Zhong Li, Yin-Bo Qu, Pei-Ji Gao
Colloids and Surfaces B: Biointerfaces 2008 Volume 65(Issue 1) pp:50-53
Publication Date(Web):1 August 2008
DOI:10.1016/j.colsurfb.2008.02.015
To enhance the catalytic activity of lignin peroxidase (LiP) in a reverse micelle, a synthesized two-tail nonionic surfactant N-gluconyl glutamic acid didecyl ester (GGDE) was used to formulate a novel reverse micelle. Based on the LiP catalyzed oxidation of veratryl alcohol (VA) in this novel GGDE/TritonX-100–cyclohexane–H2O reverse micelle, the effects of the size of the reverse micelle, the buffer pH, and the concentration of H2O2 on the catalytic activity of LiP were investigated. Under the optimized conditions, the catalytic efficiency of LiP in the GGDE/TritonX-100 reverse micelle was 40 times higher than that in the AOT reverse micelle. The full expression of catalytic activity of LiP in this medium was mainly due to the lack of electrostatic interaction between LiP and the head group of GGDE and TritonX-100 and to the size fit between LiP and the inner water cavity of the reverse micelle.
Co-reporter:Jin-Ting LIU;Pei-Ji GAO
Chinese Journal of Chemistry 2007 Volume 25(Issue 11) pp:1627-1631
Publication Date(Web):13 NOV 2007
DOI:10.1002/cjoc.200790301
The steady state kinetics of the lignin peroxidase (LiP) catalyzed oxidation of veratryl alcohol (VA) by H2O2 in a sodium bis(2-ethylhexyl) sulfosuccinate (AOT)/isooctane/toluene/water reverse micellar medium was studied and a comparison with the corresponding aqueous medium was made to understand the effect of the reverse micellar medium on the catalytic mechanism and kinetic parameters. Results indicated that the model reaction in the AOT reverse micelle followed the ping-pong mechanism with true kcat, Km,VA and K being 59.6 min−1, 13.9 mmol· L−1 and 94.8 µmol·L−1, respectively; inhibition of high level of H2O2 on LiP followed the reversible competitive pattern with Ki being 0.140 mmol·L−1. The reaction mechanism and inhibition pattern in the AOT reverse micellar medium were the same as those in bulk aqueous medium, but the kinetic parameters except K were greatly different in the two media. The kcat and Ki values in the reverse micelle were approximately 2 and 20 times smaller than the corresponding values in the aqueous solution, but the Michaelis constant of VA was approximately 100 times greater than that in the aqueous solution. The above mentioned differences in the kinetic parameters were caused by the microheterogeneity and the interface of the AOT reverse micelle, which resulted in the partitioning of VA and H2O2, and by the changes of the conformation of LiP and the reactivity of the substrates.
Co-reporter:Airong Liu, Xirong Huang, Shaofang Song, Dan Wang, Xuemei Lu, Yinbo Qu, Peiji Gao
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 2003 Volume 59(Issue 11) pp:2547-2551
Publication Date(Web):September 2003
DOI:10.1016/S1386-1425(02)00444-4
The kinetics of ligninase-catalyzed oxidation of veratryl alcohol (VA) by H2O2 in the aqueous medium containing cationic surfactant cetyltrimethylammonium bromide (CTAB) has been investigated using spectrophotometric technique. Steady-state kinetic studies at different concentrations of CTAB indicate that the reaction follows a ping pong mechanism and the mechanism always holds but the kinetic parameters vary with CTAB concentrations. CTAB is a weak inhibitor for ligninase; it lowers the maximum initial velocity. CTAB also causes the Michaelis constant of H2O2 to decrease dramatically and that of VA to increase markedly. Based on the changes in kinetic parameters of the enzyme-catalyzed reaction at different CTAB concentrations (lower than, near to and larger than its critical micelle concentration) and the effects of the CTAB monomer and the micelles on the spectra of VA and its corresponding aldehyde, a conclusion could be made that modification of the enzymatic protein by the surfactant monomer should be responsible for the above-mentioned results.
Co-reporter:Feixue Zou, Ying Li, Xinxin Yu, Jing Zhang, Xirong Huang, Yinbo Qu
Journal of Molecular Catalysis B: Enzymatic (June 2014) Volume 104() pp:35-41
Publication Date(Web):1 June 2014
DOI:10.1016/j.molcatb.2014.03.007
•Conducting and soluble PANI was biosynthesized in AOT micellar solution.•Both AOT and β-cyclodextrin are compatible with laccase.•The complex of β-cyclodextrin with aniline favors para-coupled polymerization.•AOT is doped in PANI chain while β-cyclodextrin does not thread on it.The influence of β-cyclodextrin (β-CD) on the laccase-catalyzed aniline polymerization in sodium bis-(2-ethylhexyl)sulfosuccinate (AOT) micellar solution is first presented. Results show that the anionic AOT micelle is compatible with laccase and β-CD also has little negative effect on the expression of the catalytic activity of laccase. β-CD can improve the linearity or conductivity of polyaniline biosynthesized in AOT micellar solution. Component analysis shows that AOT is doped in polyaniline chain while β-CD does not thread on the polyaniline chain. Mechanism analysis indicates that the improvement of the linearity of polyaniline by β-CD is due to steric hindrance close to the ortho-position of aniline, which favors the para-coupled aniline polymerization.Download full-size image
Co-reporter:Guiping Zhou, Xirong Huang, Yinbo Qu
Biochemical Engineering Journal (15 November 2010) Volume 52(Issues 2–3) pp:117-122
Publication Date(Web):15 November 2010
DOI:10.1016/j.bej.2010.07.007
Co-reporter:Feifan Wang, Feixue Zou, Xinxin Yu, Zhenyu Feng, Na Du, Yaohua Zhong and Xirong Huang
Physical Chemistry Chemical Physics 2016 - vol. 18(Issue 15) pp:NaN10004-10004
Publication Date(Web):2016/03/11
DOI:10.1039/C6CP00800C
A non-aqueous solution of tetra-n-butylammonium fluoride (TBAF) in ethylene glycol has been tried for the first time as a supporting electrolyte for the electropolymerization of 3-aminophenylboronic acid (APBA). Unlike the traditional acidic aqueous solution, the present medium needs no exogenous protons; moreover, the presence of CF3COOH is found to be unfavorable for the polymerization. The protons are in situ generated by the reaction between the boronic acid group on APBA and 1,2-dihydroxyl on ethylene glycol. So, ethylene glycol serves as not only the solvent but also the proton source. As a part of the supporting electrolyte, F− is found to be involved in the electrochemical synthesis of poly(3-aminophenylboronic acid) (PAPBA), but it is not indispensable. Studies on the electropolymerization process indicate that the size of the ions in the electrolyte affects the rate of the doping/dedoping process. The smaller the cation, the easier the doping/dedoping process, and the better the stability of the grown film. As demonstrated by Fourier transform infrared spectra, UV-vis spectra, and scanning electron microscopy, the obtained PAPBA is a cross-linked nanoporous polymer membrane that has a good adherence to the glassy carbon electrode.
