Frontiers of Materials Science (v.11, #3)
Hydrophobic interaction membrane chromatography for bioseparation and responsive polymer ligands involved by Jingling Chen; Rong Peng; Xiaonong Chen (197-214).
Hydrophobic interaction chromatography (HIC) is a rapid growing bioseparation technique, which separates biomolecules, such as therapeutic proteins and antibodys, based on the reversible hydrophobic interaction between immobilized hydrophobic ligands on chromatographic resin spheres and non-polar regions of solute molecule. In this review, the fundamental concepts of HIC and the factors that may affect purification efficiency of HIC is summarized, followed by the comparison of HIC with affinity chromatography and ion-exchange chromatography. Hydrophobic interaction membrane chromatography (HIMC) combines the advantages of HIC and membrane process and has showed great potential in bioseparation. For better understanding of HIMC, this review presents an overview of two main concerns about HIMC, i.e. membrane materials and hydrophobic ligands. Specifically, cellulose fiber-based membrane substrate and environment-responsive ligands are emphasized.
Keywords: hydrophobic interaction membrane chromatography; bioseparation; membrane; environmental response ligand
A soft tissue adhesive based on aldehyde-sodium alginate and amino-carboxymethyl chitosan preparation through the Schiff reaction by Yu Wu; Liu Yuan; Nai-an Sheng; Zi-qi Gu; Wen-hao Feng; Hai-yue Yin; Yosry Morsi; Xiu-mei Mo (215-222).
Sodium alginate and carboxymethyl chitosan have been extensively applied in tissue engineering and other relative fields due to their low price and excellent biocompatibility. In this paper, we oxidized sodium alginate with sodium periodate to convert 1,2-hydroxyl groups into aldehyde groups to get aldehyde-sodium alginate (ASA). Carboxymethyl chitosan was modified with ethylenediamine (ED) in the presence of water-soluble N-(3-Dimethylaminopropyl)-N′-ethylcarbodiimide hydrochloride (EDC) to introduce additional amino groups to get amino-carboxymethyl chitosan (A-CS). Upon mixing the A-SA and A-CS aqueous solutions together, a gel rapidly formed based on the Schiff’s base reaction between aldehyde groups in A-SA and amino groups in A-CS. FTIR analysis confirmed the characteristic peak of Schiff’s base group in the hydrogel. It was confirmed that the gelation time be dependent on the aldehyde group content in A-SA and amino group content in A-CS. The fasted hydrogel formation takes place within 10 min. The data of bonding strength and cytotoxicity measurement also showed that the hydrogel had good adhesion and biocompatibility. All these results support that this gel has the potential as soft tissue adhesive.
Keywords: oxidized sodium alginate; amino-carboxymethyl chitosan; tissue adhesive; Schiff’s base
One-step synthesis and self-assembly behavior of thermo-responsive star-shaped β-cyclodextrin–(P(MEO2MA-co-PEGMA))21 copolymers by Lulu Wei; Beibei Lu; Lei Li; Jianning Wu; Zhiyong Liu; Xuhong Guo (223-232).
A novel β-cyclodextrin-poly(2-(2-methoxyethoxy)ethyl methacrylate)-co-poly(ethylene glycol) methacrylate (abbreviated as: β-CD-(P(MEO2MA-co-PEGMA))21) was prepared by using the one-step strategy, and then the star-shaped copolymers were used in the atom transfer radical polymerization (ATRP). The structure of star-shaped β-CD-(P(MEO2MA-co-PEGMA))21 copolymers were studied by FTIR, 1H NMR and gel permeation chromatography (GPC). The star-shaped copolymers could self-assembled into micelles in aqueous solution owing to the outer amphiphilic β-CD as a core and the hydrophilic P(MEO2MA-co-PEGMA) segments as a shell. These thermo-responsive starshaped copolymers micelles exhibited lower critical solution temperature (LCST) in water, which could be finely tuned by changing the feed ratio of MEO2MA to PEGMA. The LCST of star-shaped β-CD-(P(MEO2MA-co-PEGMA))21 copolymer micelles were increased from 35°C to 58°C with the increasing content of PEGMA. The results were investigated by DLS and TEM. When the temperature was higher than corresponding LCSTs, the micelles started to associate and form spherical nanoparticles. Therefore, β-CD-(P(MEO2MA-co-PEGMA))21 star-shaped copolymer micelles could be potentially applied in nano-carrier, nano-reactor, smart materials and biomedical fields.
Keywords: star-shaped copolymers; thermo-responsive; β-cyclodextrin (β-CD); selfassembly; atom transfer radical polymerization (ATRP)
Efficiency enhancement in DIBSQ:PC71BM organic photovoltaic cells by using Liq-doped Bphen as a cathode buffer layer by Guo Chen; Changfeng Si; Pengpeng Zhang; Kunping Guo; Saihu Pan; Wenqing Zhu; Bin Wei (233-240).
We have improved the photovoltaic performance of 2,4-bis[4-(N,Ndiisobutylamino)- 2,6-dihydroxyphenyl] squaraine:[6,6]-phenyl C71-butyric acid methyl ester (DIBSQ:PC71BM) organic photovoltaic (OPV) cells via incorporating Liq-doped Bphen (Bphen-Liq) as a cathode buffer layer (CBL). Based on the Bphen-Liq CBL, a DIBSQ:PC71BM OPV cell possessed an optimal power conversion efficiency of 4.90%, which was 13% and 60% higher than those of the devices with neat Bphen as CBL and without CBL, respectively. The enhancement of the device performance could be attributed to the enhanced electron mobility and improved electrode/active layer contact and thus the improved photocurrent extraction by incorporating the Bphen-Liq CBL. Light-intensity dependent device performance analysis indicates that the incorporating of the Bphen-Liq CBL can remarkably improve the charge transport of the DIBSQ:PC71BM OPV cell and thus decrease the recombination losses of the device, resulting in enhanced device performance. Our finding indicates that the doped Bphen-Liq CBL has great potential for high-performance solution-processed small-molecule OPVs.
Keywords: organic photovoltaic cells; squaraine; vcathode buffer layer; power conversion efficiency; solution-process
Highly ordered Ag–TiO2 nanocomposited arrays with high visible-light photocatalytic activity by Cong Zhao; Da-chuan Zhu; Xiao-yao Cheng; Shi-xiu Cao (241-249).
TiO2 is active only in the ultraviolet region. To enhance the active ability, a combined method consisting of the anodic oxidation method and the hydrothermal method was developed to prepare highly ordered Ag-TiO2 nanocomposited arrays. The anodic oxidation was used to synthesize amorphous nanotubes with high chemical activity that subsequently served as highly ordered templates in preparing the final sample. The amorphous nanotubes got converted to highly ordered Ag-TiO2 (anatase) arrays in the silver nitrate & glucose aqueous solution via hydrothermal treatment. SEM and TEM results show that the Ag-TiO2 nanocomposite was composed of a large number of Ag nanoparticles and anatase TiO2 nanoparticles, and the morphology of those at the top of the arrays was found different from that of its trunk. The morphology evolution mechanism of the obtained sample was discussed. It is also revealed that the Ag-TiO2 nanocomposite has high visible-light photocatalytic activity.
Keywords: TiO2 ; nanoparticles; silver; heterojunction
Preparation and characterization of phosphate-modified mesoporous TiO2 incorporated in a silica matrix and their photocatalytic properties in the photodegradation of Congo red by Alberto Estrella González; Maximiliano Asomoza; Ulises Arellano; Sandra Cipagauta Díaz; Silvia Solís (250-261).
This study describes the development of mesostructured TiO2 photocatalysts modified with PO4 3- to improve its specific surface area and reduce the recombination rate of the electron—hole pairs. The mesoporous photocatalyst was successfully incorporated into a high specific surface area silica matrix by the hydrolysis reaction of tetraethyl orthosilicate (TEOS). Pluronic 123 and phosphoric acid were used as the directing agent for the structure of the mesoporous TiO2 and as a source of phosphorus, respectively. TiO2, P/TiO2, TiO2-SiO2 and P/TiO2-SiO2 materials were characterized by BET, XRD, TEM-EDS, FTIR and UV-vis DRS measurements. The photoactivity of TiO2-SiO2 nanocomposites containing 15 wt.% photocatalyst/silica was evaluated in the degradation reaction of anionic dyes with UV radiation. The proposed nanomaterials showed high potential for applications in the remediation of wastewater, being able to reuse in several cycles of reaction, maintaining its photoactivity and stability. The separation and recovery time of the material is reduced between cycles since no centrifugation or filtration processes are required after the photooxidation reaction.
Keywords: photocatalysis; phosphated TiO2 ; TiO2-SiO2 ; Congo red dye
Electroless deposition of Au nanoparticles on reduced graphene oxide/polyimide film for electrochemical detection of hydroquinone and catechol by Xuan Shen; Xiaohong Xia; Yongling Du; Chunming Wang (262-270).
An electrochemical sensor for determination of hydroquinone (HQ) and catechol (CC) was developed using Au nanoparticles (AuNPs) fabricated on reduced graphene oxide/polyimide (PI/RGO) film by electroless deposition. The electrochemical behaviors of HQ and CC at PI/RGO-AuNPs electrode were investigated by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). Under the optimized condition, the current responses at PI/RGO-AuNPs electrode were linear over ranges from 1 to 654 mol/L for HQ and from 2 to 1289 mol/L for CC, with the detection limits of 0.09 and 0.2 mol/L, respectively. The proposed electrode exhibited good reproducibility, stability and selectivity. In addition, the proposed electrode was successfully applied in the determination of HQ and CC in tap water and the Yellow River samples.
Keywords: electroless; Au nanoparticles; hydroquinone; catechol; sensor
Hydrothermal growth of symmetrical ZnO nanorod arrays on nanosheets for gas sensing applications by Wenyan Zhao; Chuanjin Tian; Zhipeng Xie; Changan Wang; Wuyou Fu; Haibin Yang (271-275).
The hierarchical ZnO nanostructures with 2-fold symmetrical nanorod arrays on zinc aluminum carbonate (ZnAl-CO3) nanosheets have been successfully synthesized through a two-step hydrothermal process. The primary nanosheets, which serve as the lattice-matched substrate for the self-assembly nanorod arrays at the second-step of the hydrothermal route, have been synthesized by using a template of anodic aluminum oxide (AAO). The as-prepared samples were characterized by XRD, FESEM, TEM and SAED. The nanorods have a diameter of about 100 nm and a length of about 2 μm. A growth mechanism was proposed according to the experimental results. The gas sensor fabricated from ZnO nanorod arrays showed a high sensitivity to ethanol at 230°C. In addition, the response mechanism of the sensors has also been discussed according to the transient response of the gas sensors.
Keywords: ZnO nanorods; hydrothermal growth; gas sensitivity
Spectroscopic investigation confirms retaining the pristine nature of single-walled carbon nanotubes on dissolution in aniline by Somdutta Singha; Swapankumar Ghosh (276-283).
Carbon nanotubes in all forms are very much insoluble in both organic and inorganic solvents due to its high agglomeration and entangled morphology. General methods for dissolution of single-walled carbon nanotubes (SWNTs) are mostly associated with complexation or polymerization or addition of macromolecules which change the physical or chemical properties of SWNTs and the pristine nature of SWNTs is lost. Dissolution of SWNTs in a solvent like aniline is practiced here which is a very simple reaction method. Here aniline is capable to form a SWNT-aniline charge transfer complex without attachment of macromolecules or polymer which is also soluble in other organic solvents. Solvation of SWNTs by this method is also capable of maintaining the similarity between the structure of SWNTs before and after the dissolution, which means that the pristine nature of SWNTs is preserved. Formation of charge transfer complex in this reaction has been proven by UV-Vis/NIR absorption and photoluminescence spectroscopy. Raman spectroscopy and electron microscopy (FESEM and TEM) are the evidences for protection of the pristine nature of SWNTs even after high-temperature complexation reaction with aniline and also after solubilization in organic solvents.
Keywords: single-walled carbon nanotubes; aniline; dissolution; organic solvent; spectroscopy
In vitro corrosion of Mg–Ca alloy — The influence of glucose content by Lan-Yue Cui; Xiao-Ting Li; Rong-Chang Zeng; Shuo-Qi Li; En-Hou Han; Liang Song (284-295).
Influence of glucose on corrosion of biomedical Mg-1.35Ca alloy was made using hydrogen evolution, pH and electrochemical polarization in isotonic saline solution. The corrosion morphologies, compositions and structures were probed by virtue of SEM, EDS, FTIR, XRD and XPS. Results indicate that the glucose accelerated the corrosion of the alloy. The elemental Ca has no visible effect on the corrosion mechanism of glucose for the Mg-1.35Ca alloy in comparison with pure Mg. In addition, the presence of CO2 has beneficial effect against corrosion due to the formation of a layer of carbonatecontaining products.
Keywords: magnesium; corrosion; glucose; biomaterial
Dynamic recrystallization behavior of AZ31 magnesium alloy processed by alternate forward extrusion by Feng Li; Yang Liu; Xu-Bo Li (296-305).
One of the important factors that affect the microstructure and properties of extruded products is recrystallization behavior. Alternate forward extrusion (AFE) is a new type of metal extrusion process with strong potential. In this paper, we carried out the AFE process experiments of as-cast AZ31 magnesium alloy and obtained extrusion bar whose microstructure and deformation mechanism were analyzed by means of optical microscopy, electron backscattered diffraction and transmission electron microscopy. The experimental results indicated that homogeneous fine-grained structure with mean grain size of 3.91 μm was obtained after AFE at 573 K. The dominant reason of grain refinement was considered the dynamic recrystallization (DRX) induced by strain localization and shear plastic deformation. In the 573-673 K range, the yield strength, tensile strength and elongation of the composite mechanical properties are reduced accordingly with the increase of the forming temperature. Shown as in relevant statistics, the proportion of the large-angle grain boundaries decreased significantly. The above results provide an important scientific basis of the scheme formulation and active control on microstructure and property for AZ31 magnesium alloy AFE process.
Keywords: magnesium alloy; alternate forward extrusion (AFE); mechanical property; dynamic recrystallization