Frontiers of Chemical Science and Engineering

ISSN 2095-0179

ISSN 2095-0187(Online)

CN 11-5981/TQ

2015 Impact Factor: 1.043

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Enzyme-instructed self-assembly of peptides containing phosphoserine to form supramolecular hydrogels as potential soft biomaterials
Jie Zhou, Xuewen Du, Jiaqing Wang, Natsuko Yamagata, Bing Xu
Front. Chem. Sci. Eng.    2017, 11 (4): 509-515.
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Enzyme-instructed self-assembly (EISA) offers a facile approach to explore the supramolecular assemblies of small molecules in cellular milieu for a variety of biomedical applications. One of the commonly used enzymes is phosphatase, but the study of the substrates of phosphatases mainly focuses on the phosphotyrosine containing peptides. In this work, we examine the EISA of phosphoserine containing small peptides for the first time by designing and synthesizing a series of precursors containing only phosphoserine or both phosphoserine and phosphotyrosine. Conjugating a phosphoserine to the C-terminal of a well-established self-assembling peptide backbone, (naphthalene-2-ly)-acetyl-diphenylalanine (NapFF), affords a novel hydrogelation precursor for EISA. The incorporation of phosphotyrosine, another substrate of phosphatase, into the resulting precursor, provides one more enzymatic trigger on a single molecule, and meanwhile increases the precursors’ propensity to aggregate after being fully dephosphorylated. Exchanging the positions of phosphorylated serine and tyrosine in the peptide backbone provides insights on how the specific molecular structures influence self-assembling behaviors of small peptides and the subsequent cellular responses. Moreover, the utilization of D-amino acids largely enhances the biostability of the peptides, thus providing a unique soft material for potential biomedical applications.

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A mini review: Shape memory polymers for biomedical applications
Kaojin Wang, Satu Strandman, X. X. Zhu
Front. Chem. Sci. Eng.    2017, 11 (2): 143-153.
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Shape memory polymers (SMPs) are smart materials that can change their shape in a pre-defined manner under a stimulus. The shape memory functionality has gained considerable interest for biomedical applications, which require materials that are biocompatible and sometimes biodegradable. There is a need for SMPs that are prepared from renewable sources to be used as substitutes for conventional SMPs. In this paper, advances in SMPs based on synthetic monomers and bio-compounds are discussed. Materials designed for biomedical applications are highlighted.

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Electrochemistry during efficient copper recovery from complex electronic waste using ammonia based solutions
Zhi Sun, Hongbin Cao, Prakash Venkatesan, Wei Jin, Yanping Xiao, Jilt Sietsma, Yongxiang Yang
Front. Chem. Sci. Eng.    2017, 11 (3): 308-316.
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Leaching selectivity during metal recovery from complex electronic waste using a hydrochemical process is always one of the generic issues. It was recently improved by using ammonia-based leaching process, specifically for electronic waste enriched with copper. This research proposes electrodeposition as the subsequent approach to effectively recover copper from the solutions after selective leaching of the electronic waste and focuses on recognising the electrochemical features of copper recovery. The electrochemical reactions were investigated by considering the effects of copper concentration, scan rate and ammonium salts. The diffusion coefficient, charge transfer coefficient and heterogeneous reaction constant of the electrodeposition process were evaluated in accordance with different solution conditions. The results have shown that electrochemical recovery of copper from ammonia-based solution under the conditions of selective electronic waste treatment is charge transfer controlled and provide bases to correlate the kinetic parameters with further optimisation of the selective recovery of metals from electronic waste.

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ZnFe2O4 deposited on BiOCl with exposed (001) and (010) facets for photocatalytic reduction of CO2 in cyclohexanol
Guixian Song, Xionggang Wu, Feng Xin, Xiaohong Yin
Front. Chem. Sci. Eng.    2017, 11 (2): 197-204.
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ZnFe2O4-BiOCl composites were prepared by both hydrothermal and direct precipitation processes and the structures and properties of the samples were characterized by various instrumental techniques. The samples were then used as catalysts for the photocatalytic reduction of CO2 in cyclohexanol under ultraviolet irradiation to give cyclohexanone (CH) and cyclohexyl formate (CF). The photocatalytic CO2 reduction activities over the hydrothermally prepared ZnFe2O4-BiOCl composites were higher than those over the directly-precipitated composites. This is because compared to the direct-precipitation sample, the ZnFe2O4 nanoparticles in the hydrothermal sample were smaller and more uniformly distributed on the surface of BiOCl and so more heterojunctions were formed. Higher CF and CH yields were obtained for the pure BiOCl and BiOCl composite samples with more exposed (001) facets than for the samples with more exposed (010) facets. This is due to the higher density of oxygen atoms in the exposed (001) facets, which creates more oxygen vacancies, and thereby improves the separation efficiency of the electron-hole pairs. More importantly, irradiation of the (001) facets with ultraviolet light produces photo-generated electrons which is helpful for the reduction of CO2 to ·CO2. The mechanism for the photocatalytic reduction of CO2 in cyclohexanol over ZnFe2O4-BiOCl composites with exposed (001) facets involves electron transfer and carbon radical formation.

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A comparison of the catalytic hydrogenation of 2-amylanthraquinone and 2-ethylanthraquinone over a Pd/Al 2O3 catalyst
Enxian Yuan, Xiangwei Ren, Li Wang, Wentao Zhao
Front. Chem. Sci. Eng.    2017, 11 (2): 177-184.
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The hydrogenation of 2-ethylanthraquinone (eAQ), 2-tert-amylanthraquinone (taAQ) and their mixtures with molar ratios of 1:1 and 1:2 to the corresponding hydroquinones (eAQH2 and taAQH2) were studied over a Pd/Al2O3 catalyst in a semi-batch slurry reactor at 60 °C and at 0.3 MPa. Compared to eAQ, TaAQ exhibited a significantly slower hydrogenation rate (about half) but had a higher maximum yield of H2O2 and a smaller amount of degradation products. This can be ascribed to the longer and branched side chain in taAQ, which limits its accessibility to the Pd surface and its diffusion through the pores of the catalyst. Density functional theory calculations showed that it is more difficult for taAQ to adsorb onto a Pd (111) surface than for eAQ. The hydrogenation of the eAQ/taAQ mixtures had the slowest rates, lowest H2O2yields and the highest amounts of degradation products.

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Aptamer-coded DNA nanoparticles for targeted doxorubicin delivery using pH-sensitive spacer
Pengwei Zhang, Junxiao Ye, Ergang Liu, Lu Sun, Jiacheng Zhang, Seung Jin Lee, Junbo Gong, Huining He, Victor C. Yang
Front. Chem. Sci. Eng.    2017, 11 (4): 529-536.
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An anticancer drug delivery system consisting of DNA nanoparticles synthesized by rolling circle amplification (RCA) was developed for prostate cancer membrane antigen (PSMA) targeted cancer therapy. The template of RCA was a DNA oligodeoxynucleotide coded with PSMA-targeted aptamer, drug-loading domain, primer binding site and pH-sensitive spacer. Anticancer drug doxorubicin, as the model drug, was loaded into the drug-loading domain (multiple GC-pair sequences) of the DNA nanoparticles by intercalation. Due to the integrated pH-sensitive spacers in the nanoparticles, in an acidic environment, the cumulative release of doxorubicin was far more than the cumulative release of the drug in the normal physiological environment. In cell uptake experiments, treated with doxorubicin loaded DNA nanoparticles, PSMA-positive C4-2 cells could take up more doxorubicin than PSMA-null PC-3 cells. The prepared DNA nanoparticles showed the potential as drug delivery system for PSMA targeting prostate cancer therapy.

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Functional ferritin nanoparticles for biomedical applications
Zhantong Wang, Haiyan Gao, Yang Zhang, Gang Liu, Gang Niu, Xiaoyuan Chen
Front. Chem. Sci. Eng.    2017, 11 (4): 633-646.
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Ferritin, a major iron storage protein with a hollow interior cavity, has been reported recently to play many important roles in biomedical and bioengineering applications. Owing to the unique architecture and surface properties, ferritin nanoparticles offer favorable characteristics and can be either genetically or chemically modified to impart functionalities to their surfaces, and therapeutics or probes can be encapsulated in their interiors by controlled and reversible assembly/disassembly. There has been an outburst of interest regarding the employment of functional ferritin nanoparticles in nanomedicine. This review will highlight the recent advances in ferritin nanoparticles for drug delivery, bioassay, and molecular imaging with a particular focus on their biomedical applications.

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Catalytic oxidation of carbon monoxide, toluene, and ethyl acetate over the xPd/OMS-2 catalysts: Effect of Pd loading
Zhidan Fu, Lisha Liu, Yong Song, Qing Ye, Shuiyuan Cheng, Tianfang Kang, Hongxing Dai
Front. Chem. Sci. Eng.    2017, 11 (2): 185-196.
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The Pd catalyst supported on cryptomelane-type manganese oxide octahedral molecular sieve (OMS-2) were prepared. The effect of Pd loading on the catalytic oxidation of carbon monoxide, toluene, and ethyl acetate over xPd/OMS-2 has been investigated. The results show that the Pd loading plays an important role on the physicochemical properties of the xPd/OMS-2 catalysts which outperform the Pd-free counterpart with the 0.5Pd/OMS-2 catalyst being the best. The temperature for 50% conversion was 25, 240 and 160 °C, and the temperature for 90% conversion was 55, 285 and 200 °C for oxidation of CO, toluene, and ethyl acetate, respectively. The low-temperature reducibility and high oxygen mobility of xPd/OMS-2 are the factors contributable to the excellent catalytic performance of 0.5Pd/OMS-2.

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Towards Cr(VI)-free anodization of aluminum alloys for aerospace adhesive bonding applications: A review
Shoshan T. Abrahami, John M. M. de Kok, Herman Terryn, Johannes M. C. Mol
Front. Chem. Sci. Eng.    2017, 11 (3): 465-482.
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For more than six decades, chromic acid anodizing (CAA) has been the central process in the surface pre-treatment of aluminum for adhesively bonded aircraft structures. Unfortunately, this electrolyte contains hexavalent chromium (Cr(VI)), a compound known for its toxicity and carcinogenic properties. To comply with the new strict international regulations, the Cr(VI)-era will soon have to come to an end. Anodizing aluminum in acid electrolytes produces a self-ordered porous oxide layer. Although different acids can be used to create this type of structure, the excellent adhesion and corrosion resistance that is currently achieved by the complete Cr(VI)-based process is not easily matched. This paper provides a critical overview and appraisal of proposed alternatives to CAA, including combinations of multiple anodizing steps, pre- and post anodizing treatments. The work is presented in terms of the modifications to the oxide properties, such as morphological features (e.g., pore size, barrier layer thickness) and surface chemistry, in order to evaluate the link between fundamental principles of adhesion and bond performance.

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Solvates and polymorphs of clindamycin phosphate: Structural, thermal stability and moisture stability studies
Junbo Gong, Dejiang Zhang, Yuanyuan Ran, Keke Zhang, Shichao Du
Front. Chem. Sci. Eng.    2017, 11 (2): 220-230.
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Clindamycin phosphate (CP), an antibacterial agent, has been reported to form several solid-state forms. The crystal structures of two CP solvates, a dimethyl sulfoxide (DMSO) solvate and a methanol/water solvate (solvate V), have been determined by single crystal X-ray diffraction. The properties and transformations of these forms were characterized by powder X-ray diffraction, Single-crystal X-ray diffraction, differential scanning calorimetry, thermo gravimetric analysis, hot-stage microscopy, and dynamic vapor sorption. Very different hydrogen bonding networks exist among the host-host and host-solvent molecules in the two crystal structures, resulting in different moisture stabilities. The thermal stabilities of the two solvates upon heating and desolvation were also studied. When the temperature was above the boiling point of methanol, solvate V converted to a polymorphic phase after a one step desolvation process, whereas the desolvation temperature of the DMSO solvate was below the boiling point of DMSO. At the relative humidity above 43%, the DMSO solvate transformed to a hydrate at 25 °C. In contrast, solvate V did not transform at any of the humidities studied.

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The influence of curing conditions on the mechanical properties and leaching of inorganic polymers made of fayalitic slag
Remus I. Iacobescu, Valérie Cappuyns, Tinne Geens, Lubica Kriskova, Silviana Onisei, Peter T. Jones, Yiannis Pontikes
Front. Chem. Sci. Eng.    2017, 11 (3): 317-327.
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This study reports on the impact of the curing conditions on the mechanical properties and leaching of inorganic polymer (IP) mortars made from a water quenched fayalitic slag. Three similar IP mortars were produced by mixing together slag, aggregate and activating solution, and cured in three different environments for 28 d: a) at 20 °C and relative humidity (RH) ~ 50% (T20RH50), b) at 20 °C and RH≥90% (T20RH90) and c) at 60 °C and RH ~ 20% (T60RH20). Compressive strength (EN 196-1) varied between 19 MPa (T20RH50) and 31 MPa (T20RH90). This was found to be attributed to the cracks formed upon curing. Geochemical modelling and two leaching tests were performed, the EA NEN 7375 tank test, and the BS EN 12457-1 single batch test. Results show that Cu, Ni, Pb, Zn and As leaching occurred even at high pH, which varied between 10 and 11 in the tank test’s leachates and between 12 and 12.5 in the single batch’s leachates. Leaching values obtained were below the requirements for non-shaped materials of Flemish legislation for As, Cu and Ni in the single batch test.

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A conceptual methodology for simultaneous optimization of water and heat with non-isothermal mixing
Yanlong Hou, Wanni Xie, Zhenya Duan, Jingtao Wang
Front. Chem. Sci. Eng.    2017, 11 (2): 154-165.
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A new conceptual methodology is proposed to simultaneously integrate water allocation and energy networks with non-isothermal mixing. This method employs a simultaneous model and includes two design steps. In the first step, the water allocation network (WAN), which could achieve the targets of saving water and energy, is obtained by taking account the temperature factor into the design procedure. The optimized targets of both freshwater and energy are reached at this step which ensures this approach is a simultaneous one. In the second step, based on the obtained WAN, the whole water allocation and heat exchange network (WAHEN) is combined with the non-isothermal mixing to reduce the number of heat exchangers. The thus obtained WAHEN can achieve three optimization targets (minimization of water, energy and the number of heat exchangers). Furthermore, the effectivity of our method has been demonstrated by solving two literature examples.

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Recent advances in SERS detection of perchlorate
Jumin Hao, Xiaoguang Meng
Front. Chem. Sci. Eng.    2017, 11 (3): 448-464.
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Perchlorate has recently emerged as a widespread environmental contaminant of healthy concern. Development of novel detection methods for perchlorate with the potential for field use has been an urgent need. The investigation has shown that surface-enhanced Raman scattering (SERS) technique has great potential to become a practical analysis tool for the rapid screening and routine monitoring of perchlorate in the field, particularly when coupled with portable/handheld Raman spectrometers. In this review article, we summarize progress made in SERS analysis of perchlorate in water and other media with an emphasis on the development of SERS substrates for perchlorate detection. The potential of this technique for fast screening and field testing of perchlorate-contaminated environmental samples is discussed. The challenges and possible solutions are also addressed, aiming to provide a better understanding on the development directions in the research field.

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Surface modification of broom sorghum-based activated carbon via functionalization with triethylenetetramine and urea for CO2capture enhancement
Elaheh Mehrvarz, Ali A. Ghoreyshi, Mohsen Jahanshahi
Front. Chem. Sci. Eng.    2017, 11 (2): 252-265.
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A new type of activated carbon (AC) was synthesized using broom sorghum stalk as a low cost carbon source through chemical activation with H3PO4 and KOH. The AC obtained by KOH had the largest BET surface area of 1619 m2·g−1 and the highest micropore volume of 0.671 cm3·g−1. CO2 adsorption was enhanced by functionalizing the AC with two different amines: triethylenetetramine (TETA) and urea. The structure of the prepared ACs was characterized by Brunauer-Emmett-Teller method, scanning electron microscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis and acid-base Boehm titration analyses. The adsorption behavior of CO2 onto raw and amine-functionalized ACs was investigated in the temperature range of 288–308 K and pressures up to 25 bar. The amount of CO2 uptake at 298 K and 1 bar achieved by AC-TETA and AC-urea was 3.22 and 2.33 mmol·g−1which shows a 92% and 40% improvement compared to pristine AC (1.66 mmol·g−1), respectively. Among different model isotherms used to describe the adsorption equilibria, Sips isotherm presented a perfect fit in all cases. Gas adsorption kinetic study revealed a fast kinetics of CO2adsorption onto the ACs. The evaluation of the isosteric heat of adsorption demonstrated the exothermic nature of the CO2 adsorption onto unmodified and modified samples.

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Metal salts with highly electronegative cations as efficient catalysts for the liquid-phase nitration of benzene by NO2 to nitrobenzene
Shenghui Zhou, Kuiyi You, Zhengming Yi, Pingle Liu, Hean Luo
Front. Chem. Sci. Eng.    2017, 11 (2): 205-210.
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Metal salts with highly electronegative cations have been used to effectively catalyze the liquid-phase nitration of benzene by NO2 to nitrobenzene under solvent-free conditions. Several salts including FeCl3, ZrCl4, AlCl3, CuCl2, NiCl2, ZnCl2, MnCl2, Fe(NO3)3·9H2O, Bi(NO3)3·5H2O, Zr(NO3)4·5H2O, Cu(NO3)2·6H2O, Ni(NO3)2·6H2O, Zn(NO3)2·6H2O, Fe2(SO4)3, and CuSO4 were examined and anhydrous FeCl3 exhibited the best catalytic performance under the optimal reaction conditions. The benzene conversion and selectivity to nitrobenzene were both over 99%. In addition, it was determined that the metal counterion and the presence of water hydrates in the salt affects the catalytic activity. This method is simple and efficient and may have potential industrial application prospects.

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Rh2O3/hexagonal CePO4 nanocatalysts for N2O decomposition
Huan Liu, Zhen Ma
Front. Chem. Sci. Eng.    2017, 11 (4): 586-593.
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Hexagonal CePO4 nanorods were prepared by a precipitation method and hexagonal CePO4 nanowires were prepared by hydrothermal synthesis at 150 °C. Rh(NO3)3 was then used as a precursor for the impregnation of Rh2O3 onto these CePO4 materials. The Rh2O3 supported on the CePO4 nanowires was much more active for the catalytic decomposition of N2O than the Rh2O3 supported on CePO4 nanorods. The stability of both catalysts as a function of time on stream was studied and the influence of the co-feed (CO2, O2, H2O or O2/H2O) on the N2O decomposition was also investigated. The samples were characterized by N2 adsorption-desorption, inductively coupled plasma optical emission spectroscopy, X-ray diffraction, transmission electron microscopy, X-ray photoelectron microscopy, hydrogen temperature-programmed reduction, oxygen temperature-programmed desorption, and CO2 temperature-programmed desorption in order to correlate the physicochemical and catalytic properties.

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Progress in membrane distillation crystallization: Process models, crystallization control and innovative applications
Xiaobin Jiang, Linghan Tuo, Dapeng Lu, Baohong Hou, Wei Chen, Gaohong He
Front. Chem. Sci. Eng.    2017, 11 (4): 647-662.
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Membrane distillation crystallization (MDC) is a promising hybrid separation process that has been applied to seawater desalination, brine treatment and wastewater recovery. In recent years, great progress has been made in MDC technologies including the promotion of nucleation and better control of crystallization and crystal size distribution. These advances are useful for the accurate control of the degree of supersaturation and for the control of the nucleation kinetic processes. This review focuses on the development of MDC process models and on crystallization control strategies. In addition, the most important innovative applications of MDC in the last five years in crystal engineering and pharmaceutical manufacturing are summarized.

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The effect of doping and steam treatment on the catalytic activities of nano-scale H-ZSM-5 in the methanol to gasoline reaction
Baodong Song, Yongqiang Li, Gang Cao, Zhenhai Sun, Xu Han
Front. Chem. Sci. Eng.    2017, 11 (4): 564-574.
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In the transformation of methanol to gasoline (MTG), the selectivity to gasoline and the aromatic content in the produced gasoline are important factors. The catalytic activities of steam-treated and non-steam-treated nano-scale H-ZSM-5 (NHZ5) catalysts impregnated with Ag(I), Zn(II) or P(V) have been investigated in a continuous flow fixed bed reactor. The NH3-TPD results showed that after impregnation, the Ag/NHZ5, Zn/NHZ5 and P/NHZ5 catalysts contained comparatively more strong, medium-strong and weak acid sites, respectively. Treatment with steam decreased the number of acid sites in all the catalysts, but the pore volumes in the catalysts were larger which improved carbon deposition resistance resulting in prolonged lifetimes. After 6 h of MTG reaction, the selectivity to gasoline for the steam-treated catalysts, AgH2O/NHZ5, ZnH2O/NHZ5 and PH2O/NHZ5 were 70.5, 68.4 and 68.7 wt-%, respectively, whereas their respective aromatic contents in the produced gasoline were 61.9, 55.4 and 39.0 wt-%. Thus PH2O/NHZ5 is the most promising catalyst for MTG applications which can meet the China IV gasoline standard that the amount of aromatics in gasoline should be less than 48 wt-%.

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A comparative study on polypropylene separators coated with different inorganic materials for lithium-ion batteries
Linghui Yu, Jiansong Miao, Yi Jin, Jerry Y.S. Lin
Front. Chem. Sci. Eng.    2017, 11 (3): 346-352.
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Coating commercial porous polyolefin separators with inorganic materials can improve the thermal stability of the polyolefin separators and hence improve the safety of lithium-ion batteries. Several different inorganic materials have been studied for the coating. However, there lacks a study on how different inorganic materials affect the properties of separators, in terms of thermal stability and cell performance. Herein, we present such a study on coating a commercial polypropylene separator with four inorganic materials, i.e., Al2O3, SiO2, ZrO2 and zeolite. All inorganic coatings have improved thermal stability of the separators although with differences. The coating layers add 28%–45% of electrical resistance compared with the pure polypropylene separator, but all the cells prepared with the coated polypropylene separators have the same electrical chemical performance as the uncoated separator in terms of rate capability and capacities at different temperatures.

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The preparation and performance of lignin-based activated carbon fiber adsorbents for treating gaseous streams
Min Song, Wei Zhang, Yongsheng Chen, Jinming Luo, John C. Crittenden
Front. Chem. Sci. Eng.    2017, 11 (3): 328-337.
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Two types of lignin-based carbon fibers were prepared by electrospinning method. The first was activated with Fe3O4 (LCF-Fe), and the second was not activated with Fe3O4 (LCF). Gas phase adsorption isotherms for toluene on LCF-Fe and LCF were studied. The gas phase adsorption isotherm for 0% RH showed LCF-Fe have about 439 mg/g adsorption capacity which was close to that of commercially available activated carbon (500 mg/g). The Dubinin-Radushkevich equation described the isotherm data very well. Competitive adsorption isotherms between water vapor and toluene were measured for their RH from 0 to 80%. The effect of humidity on toluene gas-phase adsorption was predicted by using the Okazaki et al. model. In addition, a constant pattern homogeneous surface diffusion model (CPHSDM) was used to predict the toluene breakthrough curve of continuous flow-packed columns containing LCF-Fe, and its capacity was 412 mg/g. Our study, which included material characterization, adsorption isotherms, kinetics, the impact of humidity and fixed bed performance modeling, demonstrated the suitability of lignin-based carbon fiber for volatile organic compound removal from gas streams.

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Visual chiral recognition of 1,1′-binaphthol through enantioselective collapse of gel based on an amphiphilic Schiff-base gelator
Xuhong Zhang, Haimiao Li, Xin Zhang, Meng An, Weiwei Fang, Haitao Yu
Front. Chem. Sci. Eng.    2017, 11 (2): 231-237.
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A novel gelator that contained both Schiff base and L-lysine moieties was synthesized and its gelation behavior was tested. This gelator can form gels in various organic solvents. The resulting gel can be applied as a fascinating platform for visual recognition of enantiomeric 1-(2-hydroxynaphthalen-1-yl)naphthalen-2-ol (BINOL) through selective gel collapse. In addition, the mechanism for the reaction of the gel with chiral BINOL was investigated by scanning electron microscope and 1H nuclear magnetic resonance.

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Molecular engineering of dendrimer nanovectors for siRNA delivery and gene silencing
Yu Cao, Xiaoxuan Liu, Ling Peng
Front. Chem. Sci. Eng.    2017, 11 (4): 663-675.
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Small interfering RNA (siRNA) therapeutics hold great promise to treat a variety of diseases, as long as they can be delivered safely and effectively into cells. Dendrimers are appealing vectors for siRNA delivery by virtue of their well-defined molecular architecture and multivalent cooperativity. However, the clinical translation of RNA therapeutics mediated by dendrimer delivery is hampered by the lack of dendrimers that are of high quality to meet good manufacturing practice standard. In this context, we have developed small amphiphilic dendrimers that self-assemble into supramolecular structures, which mimic high-generation dendrimers synthesized with covalent construction, yet are easy to produce in large amount and superior quality. Indeed, the concept of supramolecular dendrimers has proved to be very promising, and has opened up a new avenue for dendrimer-mediated siRNA delivery. A series of self-assembling supramolecular dendrimers have consequently been established, some of them out-performing the currently available nonviral vectors in delivering siRNA to various cell types in vitro and in vivo, including human primary cells and stem cells. This short review presents a brief introduction to RNAi therapeutics, the obstacles to their delivery and the advantages of dendrimer delivery vectors as well as our bio-inspired structurally flexible dendrimers for siRNA delivery. We then highlight our efforts in creating self-assembling amphiphilic dendrimers to construct supramolecular dendrimer nanosystems for effective siRNA delivery as well as the related structural alterations to enhance delivery efficiency. The advent of self-assembling supramolecular dendrimer nanovectors holds great promise and heralds a new era of dendrimer-mediated delivery of RNA therapeutics in biomedical applications.

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Large-scale industrial manufacturing of carbon nanotubes in a continuous inclined mobile-bed rotating reactor via the catalytic chemical vapor deposition process
Sophie L. Pirard, Sigrid Douven, Jean-Paul Pirard
Front. Chem. Sci. Eng.    2017, 11 (2): 280-289.
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This article reports the different steps of the design, development and validation of a process for continuous production of carbon nanotubes (CNTs) via catalytic chemical vapor deposition from the laboratory scale to the industrial production. This process is based on a continuous inclined mobile-bed rotating reactor and very active catalysts using methane or ethylene as carbon source. The importance of modeling taking into account the hydrodynamic, physicochemical and physical phenomena that occur during CNT production in the process analysis is emphasized. The impact of this invention on the environment and human health is taken into consideration too.

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Microfluidic synthesis of renewable biosorbent with highly comprehensive adsorption performance for copper (II)
Yong Zhu, Zhishan Bai, Bingjie Wang, Linlin Zhai, Wenqiang Luo
Front. Chem. Sci. Eng.    2017, 11 (2): 238-251.
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A microsphere biosorbent with uniform size (CV= 1.52%), controllable morphology and component, and high mechanical strength was synthesized from chitosan by microfluidic technology combining with chemical crosslinking and solvent extraction. This chitosan microsphere (CS-MS) was prepared with a two-step solidification process, which was acquired by drying for the enhancement of mechanical property in final. The adsorption behavior of CS-MS towards copper (II) and main influencing factors on adsorption performance were investigated by batch experiments. Kinetic data highlighted dominant chemical bonding along with electrons transferring in adsorption process. Isothermal analysis indicated that adsorption capacity was relevant to the number of active site. All these explorations provided a new direction for preparing highly comprehensive performance sorbent used in heavy metal treatment via microfluidic technology.

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Design, synthesis, biological activity and density function theory study of pyrazole derivatives containing 1,3,4-thiadiazole moiety
Xiaoming Ding, Zhiwen Zhai, Luping Lv, Zhaohui Sun, Xinghai Liu
Front. Chem. Sci. Eng.    2017, 11 (3): 379-386.
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A variety of pyrazole derivatives containing 1,3,4-thiadiazole moiety were synthesized under microwave irradiation, and their structures were confirmed by 1H NMR and HRMS. They were evaluated for herbicidal and antifungal activities, and the results indicated that two compounds with a phenyl group (6a) and 4-tert-butylphenyl group (6n) possess good herbicidal activity for dicotyledon Brassica campestris and Raphanus sativus with the inhibition of 90% for root and 80%–90% for stalk at 100 ppm respectively. The structure-activity relationship of compounds 6a and 6n was also studied by density function theory method.

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Gene delivery into isolated Arabidopsis thaliana protoplasts and intact leaves using cationic, α-helical polypeptide
Nan Zheng, Ziyuan Song, Yang Liu, Lichen Yin, Jianjun Cheng
Front. Chem. Sci. Eng.    2017, 11 (4): 521-528.
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The application of gene delivery materials has been mainly focused on mammalian cells while rarely extended to plant engineering. Cationic polymers and lipids have been widely utilized to efficiently deliver DNA and siRNA into mammalian cells. However, their application in plant cells is limited due to the different membrane structures and the presence of plant cell walls. In this study, we developed the cationic, α-helical polypeptide that can effectively deliver DNA into both isolated Arabidopsis thaliana protoplasts and intact leaves. The PPABLG was able to condense DNA to form nanocomplexes, and they exhibited significantly improved transfection efficiencies compared with commercial transfection reagent Lipofectamine 2000 and classical cell penetrating peptides such as poly(L-lysine), HIV-TAT, arginine9, and poly(L-arginine). This study therefore widens the utilities of helical polypeptide as a unique category of gene delivery materials, and may find their promising applications toward plant gene delivery.

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The feasibility of coating by cooling crystallization on ibuprofen naked tablets
Fatima Mameri, Ouahiba Koutchoukali, Mohamed Bouhelassa, Anne Hartwig, Leila Nemdili, Joachim Ulrich
Front. Chem. Sci. Eng.    2017, 11 (2): 211-219.
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Sugar spray coating is a frequently used process in the pharmaceutical industry. However, this process presents the disadvantage to form an amorphous coating around the active ingredient. A crystalline coating formed on the surface of a tablet is highly desirable. Recently, a new process of coating by cooling crystallization has been developed and applied on bisacodyl pastilles obtained by melt crystallization. In this work, we investigated the feasibility of coating by cooling crystallization on ibuprofen “naked tablets” manufactured by compression. In the first part of this work, the solubility and the metastable zone width have been determined experimentally for the coating solution because they are essential factors for any crystallization process. In the second part, the coating process is investigated on the operating conditions that affect the surface morphology and the crystal growth rate. These experimental conditions include concentration of the coating solution, degree of sub-cooling, agitation speed, retention time, and surface properties of the naked ibuprofen tablets. The results show that naked tablet coating by cooling crystallization is feasible and can be applied in the pharmaceutical industry.

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Preparation and characterization of hydrothermally engineered TiO2-fly ash composite membrane
Kanchapogu Suresh, G. Pugazhenthi, R. Uppaluri
Front. Chem. Sci. Eng.    2017, 11 (2): 266-279.
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This work targets the preparation and characterization of an inexpensive TiO2-fly ash composite membrane for oily wastewater treatment. The composite membrane was fabricated by depositing a hydrophilic TiO2 layer on a fly ash membrane via the hydrothermal method, and its structural, morphological and mechanical properties were evaluated. The separation potential of the composite membrane was evaluated for 100–200 mg·L–1 synthetic oily wastewater solutions. The results show that the composite membrane has excellent separation performance and can provide permeate stream with oil concentration of only 0.26–5.83 mg·L–1. Compared with the fly ash membrane in the average permeate flux and performance index (49.97 × 10–4 m3·m–2·s–1 and 0.4620%, respectively), the composite membrane exhibits better performance (51.63 × 10−4 m3·m−2·s−1 and 0.4974%). For the composite ash membrane, the response surface methodology based analysis inferred that the optimum process parameters to achieve maximum membrane flux and rejection are 207 kPa, 200 mg·L–1 and 0.1769 m·s–1 for applied pressure, feed concentration and cross flow velocity, respectively. Under these conditions, predicted responses are 41.33 × 10–4 m3·m−2·s−1 permeate flux and 98.7% rejection, which are in good agreement with the values obtained from experimental investigations (42.84 × 10−4 m3·m−2·s−1 and 98.82%). Therefore, we have demonstrated that the TiO2-fly ash composite membrane as value added product is an efficient way to recycle fly ash and thus mitigate environmental hazards associated with the disposal of oily wastewaters.

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Removal of dyes from wastewater by growing fungal pellets in a semi-continuous mode
Tao Lu, Qilei Zhang, Shanjing Yao
Front. Chem. Sci. Eng.    2017, 11 (3): 338-345.
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To increase the efficiency of dye removal from wastewater using mycelial pellets, a bubble column reactor with a simple structure was designed and efficiently used to remove dyes from solution containing dyes. The mycelial pellets were prepared by marine fungus Aspergillus niger ZJUBE-1. Eight dyes were tested as dye targets for the adsorption capacity of mycelial pellets and good removal results were obtained. Eriochrome black T was selected as a model dye for characterizing the adsorption processes in detail. The measurement results of Zeta potential and FT-IR analysis indicate that the electrostatic attraction may play a key role in the biosorption process. The bubble column reactor was utilized to study the batch dye-removal efficiency of mycelial pellets. A re-culture process between every two batches, which was under non-sterile condition, successfully enhanced the utilization of mycelium biomass. The dye removal rate is 96.4% after 12 h in the first batch and then decreases slowly in the following batches. This semi-continuous mode, which consists of commutative processes of dye-removal and re-culture, has some outstanding advantages, such as low power consumption, easy operation, high dye removal rate, and efficient biomass utilization.

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