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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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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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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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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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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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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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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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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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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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 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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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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Nanovaccines for remodeling the suppressive tumor microenvironment: New horizons in cancer immunotherapy
Kai Shi, Matthew Haynes, Leaf Huang
Front. Chem. Sci. Eng.    2017, 11 (4): 676-684.
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Despite limited successes in clinical development, therapeutic cancer vaccines have experienced resurgence in recent years due to an enhanced emphasis upon co-mitigating factors underlying immune response. Specifically, reversing the immune-suppressive effects of the tumor microenvironment, mediated by a variety of cellular and molecular signaling mechanisms, has become fundamental toward enhancing therapeutic efficacy. Therein, our lab has implemented various nano-vaccines based on the lipid-coated calcium phosphate platform for combined immunotherapy, in which antigenic, epitope-associated peptides as well as immune-suppression inhibitors can be co-delivered, often functioning through the same formulation. In probing the mechanism of action of such systems in vitro andin vivo, an improved effect synergy can be elucidated, inspiring future preclinical efforts and hope for clinical success.

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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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Synthesis and in vivo nematocidal evaluation of novel 3-(trifluoromethyl)-1H-pyrazole-4-carboxamide derivatives
Wen Zhao, Jiahua Xing, Tianming Xu, Weili Peng, Xinghai Liu
Front. Chem. Sci. Eng.    2017, 11 (3): 363-368.
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Pyrazole carboxamide derivatives represent an important class of fungicides in agrochemicals. To find more novel structural pyrazole carboxamides, a novel series of 3-(trifluoromethyl)-1H-pyrazole-4-carboxamide compounds were prepared from ethyl 4,4,4-trifluoroacetoacetate and triethyl orthoformate as starting materials. All the products were characterized by Fourier transform infrared spectroscopy, 1H nuclear magnetic resonance (NMR), 13C NMR, 19F NMR and mass spectrography. The bioassay results showed these fluorine-containing pyrazole carboxamides have a weak fungicidal activity but some of them exhibit a good nematocidal activity against M. incognita.

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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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Materials sustainability for environment: Red-mud treatment
Brajendra Mishra, Sumedh Gostu
Front. Chem. Sci. Eng.    2017, 11 (3): 483-496.
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Bayer’s process revolutionized the extraction of aluminum from the bauxite ores. However, the hydrothermal extraction of alumina is associated with the generation of a byproduct, red-mud consisting of undissolved solids composed of iron oxides, sodium alumino silicates, titania, silica and rare earth elements. The accumulation of red-mud (or bauxite residue) in the world is 30 billion metric tons produced at a rate of 125 million tons per annum (2013). Utilization of red-mud for constructional purposes, wastewater treatment, metallurgical products, and pigments are listed. Metallurgical processing efforts of red-mud to generate various value added products such as pig iron, direct reduced iron slag wool, magnetite, titania, iron carbides are presented in the article.

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Engineering platelet-mimicking drug delivery vehicles
Quanyin Hu, Hunter N. Bomba, Zhen Gu
Front. Chem. Sci. Eng.    2017, 11 (4): 624-632.
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Platelets dynamically participate in various physiological processes, including wound repair, bacterial clearance, immune response, and tumor metastasis. Recreating the specific biological features of platelets by mimicking the structure of the platelet or translocating the platelet membrane to synthetic particles holds great promise in disease treatment. This review highlights recent advancements made in the platelet-mimicking strategies. The future opportunities and translational challenges are also discussed.

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Effects of preparation methods on the activity of CuO/CeO2 catalysts for CO oxidation
Huanhuan Shang, Xiaoman Zhang, Jing Xu, Yifan Han
Front. Chem. Sci. Eng.    2017, 11 (4): 603-612.
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CO oxidation has been investigated on three CuO/CeO2 catalysts prepared by impregnation, co-precipitation and mechanical mixing. The origin of active sites was explored by the multiple techniques. The catalyst prepared by impregnation has more highly dispersed CuO and stronger interactions between CuO and CeO2 to promote the reduction of CuO to Cu+ species at the Cu-Ce interface, leading to its highest catalytic activity. For the catalyst prepared by co-precipitation, solid solution structures observed in Raman spectra suppress the formation of the Cu-Ce interface, where the adsorbed CO will react with active lattice oxygen to form CO2, and thus it displays a lower catalytic performance. No Cu-Ce interface exists in the catalyst prepared by the mechanical mixing method due to the separate phases of CuO and CeO2, resulting in its lowest activity among the three catalysts.

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Shape selective catalysis in methylation of toluene: Development, challenges and perspectives
Jian Zhou, Zhicheng Liu, Yangdong Wang, Dejin Kong, Zaiku Xie
Front. Chem. Sci. Eng.    2018, 12 (1): 103-112.
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Toluene methylation with methanol offers an alternative method to produce p-xylene by gathering methyl group directly from C1 chemical sources. It supplies a “molecular engineering” process to realize directional conversion of toluene/methanol molecules by selective catalysis in complicated methylation system. In this review, we introduce the synthesis method of p-xylene, the development history of methylation catalysts and reaction mechanism, and the effect of reaction condition in para-selective technical process. If constructing p-xylene as the single target product, the major challenge to develop para-selective toluene methylation is to improve the p-xylene selectivity without, or as little as possible, losing the fraction of methanol for methylation. To reach higher yield of p-xylene and more methanol usage in methylation, zeolite catalyst design should consider improving mass transfer and afterwards covering external acid sites by surface modification to get short “micro-tunnels” with shape selectivity. A solid understanding of mass transfer will benefit realizing the aim of converting more methanol feedstock into para-methyl group.

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Predictive calculations of gas solubility and permeability in glassy polymeric membranes: An overview
Matteo Minelli, Maria Grazia De Angelis, Giulio C. Sarti
Front. Chem. Sci. Eng.    2017, 11 (3): 405-413.
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The possibility to evaluate in a predictive way the relevant transport properties of low molecular weight species, both gases and vapors, in glassy polymeric membranes is inspected in detail, with particular attention to the methods recently developed based on solid thermodynamic basis. The solubility of pure and mixed gases, diffusivity and permeability of single gases in polymer glasses are examined, considering in particular poly(2,6-dimethyl-1,4-phenylene oxide) as a relevant test case. The procedure clearly indicates what are the relevant physical properties of the polymer matrix and of the penetrants required by the calculations, which can be obtained experimentally through independent measurements. For gas and vapor solubility, the comparison with direct experimental data for mixed gases points out also the ability to account for the significant variations that solubility-selectivity experiences upon variations of pressure and/or feed composition. For gas and vapor permeability, the comparison with direct experimental data shows the possibility to account for the various different trends observed experimentally as penetrant pressure is increased, including the so-called plasticization behavior. The procedure followed for permeability calculations leads also to clear correlations between permeability and physical properties of both polymer and penetrant, based on which pure predictive calculations are reliably made.

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Metal-organic framework loaded manganese oxides as efficient catalysts for low-temperature selective catalytic reduction of NO with NH3
Minhua Zhang, Baojuan Huang, Haoxi Jiang, Yifei Chen
Front. Chem. Sci. Eng.    2017, 11 (4): 594-602.
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A mild in-situdeposition method was used to fabricate Mn-based catalysts on a UiO-66 carrier for the selective catalytic reduction of NO by NH3 (NH3-SCR). The catalyst with 8.5 wt-% MnOx loading had the highest catalytic activity for NH3-SCR with a wide temperature window (100–290 °C) for 90% NO conversion. Characterization of the prepared MnOx/UiO-66 catalysts showed that the catalysts had the crystal structure and porosity of the UiO-66 carrier and that the manganese particles were well-distributed on the surface of the catalyst. X-ray photoelectron spectroscopy analysis showed that there are strong interactions between the MnOx and the Zr oxide secondary building units of the UiO-66 which has a positive effect on the catalytic activity. The 8.5 wt-% MnOx catalyst maintained excellent activity during a 24-h stability test and exhibited good resistance to SO2 poisoning.

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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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Effects of metal ions on the morphology of calcium sulfate hemihydrate whiskers by hydrothermal method
Tianjie Liu, Hao Fan, Yanxia Xu, Xingfu Song, Jianguo Yu
Front. Chem. Sci. Eng.    2017, 11 (4): 545-553.
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The effects of Na+, Mg2+, Al3+ and Fe3+ ion concentrations on the crystal morphology of calcium sulfate hemihydrate whiskers formed via a hydrothermal method have been studied. In the presence of Al3+ concentrations higher than 1×103 mol/L the whiskers were significantly shorter and thicker and the presence of Mg2+ and Fe3+ resulted in shorter whiskers. The presence of Na+ did not affect the morphology of the whiskers. Through elemental analysis, it was determined that Mg2+ and Al3+ were selectively adsorbed on the surfaces of the crystals, whereas Fe3+ underwent a hydrolysis reaction to form a brown precipitate which decreased the ion concentration in the solution. These results indicate that in raw materials used for the industrial preparation of calcium sulfate whiskers, Al3+ and Fe3+ should be removed and the Mg2+ concentration should be less than 8 × 103 mol/L in order to obtain pure whiskers with high aspect ratios.

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Preparation and characteristics of TEMPO-oxidized cellulose nanofibrils from bamboo pulp and their oxygen-barrier application in PLA films
Bozhen Wu, Biyao Geng, Yufei Chen, Hongzhi Liu, Guangyao Li, Qiang Wu
Front. Chem. Sci. Eng.    2017, 11 (4): 554-563.
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Bleached bamboo kraft pulp was pretreated by 2,2,6,6-tetramethylpiperidine-1-oxy radical (TEMPO)-mediated oxidation using a TEMPO/NaBr/NaClO system at pH= 10 in water to facilitate mechanical disintegration into TEMPO-oxidized cellulose nanofibrils (TO-CNs). A series of TO-CNs with different carboxylate contents were obtained by varying amounts of added NaClO. An increase in carboxylate contents results in aqueous TO-CN dispersions with higher yield, zeta potential values, and optical transparency. When carboxylate groups are introduced, the DPv value of the TO-CNs remarkably decreases and then levels off. And the presence of hemicellulose in the pulp is favorable to TEMPO oxidization. After the oxidization, the native cellulose I crystalline structure and crystal size of bamboo pulp are almost maintained. TEM micrographs revealed that the degree of nanofibrillation is directly proportional to the carboxylate contents. With increasing carboxylate contents, the free-standing TO-CN films becomes more transparent and mechanically stronger. The oxygen permeability of PLA films drastically decreases from 355 for neat PLA to 8.4 mL·m−2·d1 after coating a thin layer of TO-CN with a carboxylate content of 1.8 mmol·g−1. Therefore, inexpensive and abundant bamboo pulp would be a promising starting material to isolate cellulose nanfibrils for oxygen-barrier applications.

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Combining innovative science and policy to improve air quality in cities with refining and chemicals manufacturing: The case study of Houston, Texas, USA
David T. Allen
Front. Chem. Sci. Eng.    2017, 11 (3): 293-304.
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In Houston, a combination of urban emissions from a city of 4 million people, coupled with emissions from extensive petroleum refining and chemical manufacturing, leads to conditions for photochemistry that are unique in the United States, and historically, the city had experienced some of the highest ozone concentrations recorded in the United States. Large air quality field studies (the Texas Air Quality Studies or TexAQS I and II) were conducted to determine root causes of the high ozone concentrations. Hundreds of air quality investigators, from around the world, deployed instruments on aircraft, on ships, and at fixed ground sites to make extensive air quality measurements; detailed photochemical modeling was used to interpret and assess the implications of the measurements. The Texas Air Quality Studies revealed that both continuous and episodic emissions of light alkenes, which came to be called highly reactive volatile organic compounds, played a critical role in the formation of ozone and other photochemical oxidants in the region. Understanding and quantifying the role of these emissions in regional air quality required innovations in characterizing emissions and in photochemical modeling. Reducing emissions required innovative policy approaches. These coupled scientific and policy innovations are described, and the result, substantially cleaner air for Houston, is documented. The lessons learned from the Houston air quality experience are relevant to cities with similar population and industrial profiles around the world.

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Cited: WebOfScience(1)
Molecular dynamics study of water diffusion in an amphiphilic block copolymer with large difference in the blocks’ glass transition temperatures
Yang Zhou, Phillip Choi
Front. Chem. Sci. Eng.    2017, 11 (3): 440-447.
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Isothermal-isobaric molecular dynamics simulation was used to study the diffusion mechanism of water in polyurethane-block-poly(N-isopropyl acrylamide) (PU-block-PNIPAm) with a hydrophobic PU/hydrophilic PNIPAm mass ratio of 1.4 to 1 at 298 K and 450 K. Here, the experimental glass transition temperature (Tg) of PU is 243 K while that of PNIPAm is 383 K. Different amounts of water up to 15 wt-% were added to PU-block-PNIPAm. We were able to reproduce the specific volumes and glass transition temperatures (250 K and 390 K) of PU-block-PNIPAm. The computed self-diffusion coefficient of water increased exponentially with increasing water concentration at both temperatures (i.e., following the free volume model of Fujita). It suggested that water diffusion in PU-block-PNIPAm depends only on its fractional free volume despite the free volume inhomogeneity. It is noted that at 298 K, PU is rubbery while PNIPAm is glassy. Regardless of temperature, radial distribution functions showed that water formed clusters with sizes in the range of 0.2–0.4 nm in PU-block-PNIPAm. At low water concentrations, more clusters were found in the PU domain but at high water concentrations, more in the PNIPAm domain. It is believed that water molecules diffuse as clusters rather than as individual molecules.

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Cited: WebOfScience(2)
Multi-functional 3D N-doped TiO2 microspheres used as scattering layers for dye-sensitized solar cells
Zijian Cui, Kaiyue Zhang, Guangyu Xing, Yaqing Feng, Shuxian Meng
Front. Chem. Sci. Eng.    2017, 11 (3): 395-404.
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Three-dimensional TiO2 microspheres doped with N were synthesized by a simple single-step solvothermal method and the sample treated for 15 h (hereafter called TMF) was then used as scattering layers in the photoanodes of dye-sensitized solar cells (DSSCs). The TMF was characterized using scanning electron microscopy, high resolution transmission electron microscopy, Brunauer-Emmett-Teller measurements, X-ray diffraction, and X-ray photoelectron spectroscopy. The TMF had a high surface area of 93.2 m2·g1 which was beneficial for more dye-loading. Five photoanode films with different internal structures were fabricated by printing different numbers of TMF scattering layers on fluorine-doped tin oxide glass. UV-vis diffuse reflection spectra, incident photon-to-current efficiencies, photocurrent-voltage curves and electrochemical impedance spectroscopy were used to investigate the optical and electrochemical properties of these photoanodes in DSSCs. The presence of nitrogen in the TMF changed the TMF microstructure, which led to a higher open circuit voltage and a longer electron lifetime. In addition, the presence of the nitrogen significantly improved the light utilization and photocurrent. The highest photoelectric conversion efficiency achieved was 8.08%, which is much higher than that derived from typical P25 nanoparticles (6.52%).

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