Template-assisted spray-drying method for the fabrication of porous particles with tunable structures

Developing strategies for the production of porous particles with controllable structures using a spray-drying method has attracted attention of researchers for decades. Although many papers have reported their successful production of porous particles using this method, information on how to create and control the porous structures as well as what parameters involving and what formation mechanism occurring during the synthesis process are still not clear. To meet these demands, the present review covers strategies in the spray-drying developments for the fabrication of porous particles with controllable structure. This information is important for optimizing the production of porous particles with desirable properties. Regulation of process conditions and precursor formulations are also explained, including composition, type, and physicochemical properties of droplet and raw components used (i.e., host component, template, and solvent). The electrostatic interactions between the individual components and the droplets are also presented, while this information tends to be neglected in the conventional spray-drying process. To clarify how the porous particles are designed, current experimental results completed with illustrations for the proposal particle formation mechanism are presented. The review also completed with the opportunities and potential roles of the changing porous structures in practical uses. This review would provide information on how to produce porous particles that can be used for advanced functional materials, such as catalysts, adsorbents, and sensors.     

An enzyme-loaded reactor using metal-organic framework-templated polydopamine microcapsule

Ultrathin polydopamine microcapsules with hierarchical structure and porosity were prepared for the immobilization of multienzymes using metal-organic framework (MOF) as the template. The multienzyme/MOF composite was first prepared using a “one-pot” co-precipitation approach via the coordination and self-assembly of zinc ions and 2-methylimidazole in the presence of enzymes. The obtained nanoparticles were then coated with polydopamine thin layer through the self-polymerization of dopamine under alkaline condition. The polydopamine microcapsules with an ultrathin shell thickness of ~48 nm were finally generated by removing the MOF template at acidic condition. Three enzymes were encapsulated in PDA microcapsules including carbonic anhydrase (CA), formate dehydrogenase (FateDH), and glutamate dehydrogenase (GDH). FateDH that catalyzed the main reaction of CO₂ reduction to formic acid retained 94.7% activity of equivalent free FateDH. Compared with free multienzymes, the immobilized ones embedded in PDA microcapsules exhibited 4.5-times higher of formate production and high catalytic efficiency with a co-factor-based formate yield of 342%.     

Impregnated active layer combustion synthesis of nano MgFe2O4 using green template

Nano-Magnesium ferrite (MgFe₂O₄) powders have been prepared by a modified combustion synthesis method named impregnated active layer combustion (IALC). The effects of five important parameters such as main fuel to oxidizer ratio (F/O), main fuel type, added fuel type, template type and main fuel (Added F/MF) to the added fuel ratio have been studied using Taguchi design. Xylitol, D-mannitol, ethylene diamine tetra acetic acid (EDTA) and diethylene triamine penta acetic acid (DTPA) were used as fuels. Besides, waste newspaper and Platanus orientalis leaf (POL) were used as new green templates. Samples were characterized by XRD, XRF, SEM, TEM, BET and VSM analyses. Results showed that the average crystallite size of the sample prepared under optimized condition (mixture of Xylitol and DTPA as fuel, POL as template, and Added F/MF ratio of 0.75) was 17.66?nm. The result was confirmed by TEM. The saturated magnetization of the optimum sample was 21?emu/g and the specific surface area was 15.377?m²/g.     

Synthesis and Reactivity of Iron(II) Complexes with a New Tripodal Imine Ligand

A new tripodal imine ligand tris(2-(propan-2-ylideneamino)ethyl)amine (imine₃tren) was prepared in order to stabilize high valent iron-oxido complexes. Iron complexes were synthesized in template reactions from iron(II) salts, tris(2-aminoethyl)amine (tren) and acetone. Due to the reversibility of the imine formation, complexes with different ligands were obtained depending on the reaction conditions. Three complexes, [Fe(imine₃tren)(OAc)₂] ( 1 ), [Fe(imine₃tren)(OAc)]OTf ( 2 ) and [(imine₃tren)₂Fe₂(F)₂](SbF₆)₂ ( 3 ), could be synthesized and structurally characterized. However, reactions with hydrogen peroxide, iodosobenzene or ozone did not lead to any kind of “oxygen adduct” complex that could be spectroscopically observed.     

纳米颗粒氧化铈的制备研究

氧化铈由于具备独特的redox性能,在催化剂制备方面倍受关注。本文介绍了水热法、模板剂诱导均相沉淀法制备纳米颗粒氧化铈的合成工艺。在NaOH、NH3反应体系中,120℃、24h可获得肩峰较宽、具有CeO2、Ce3O3固溶峰的纳米结构氧化铈颗粒。粒径在5～15nm,比表面积为128 52m2/g;模板诱导沉淀法在(NH2)2CO为0 44mol、SDS为0 02mol、Ce(NO3)3·6H2O为0 01mol、反应72h,可制备出比表面积为155 08m2/g,粒径为10nm、孔径(poresize)为10 07nm的氧化铈。两种合成方法均可制备出具有催化剂所要求的、较高内比表面积和较好纳米结构相的氧化铈颗粒。     

嵌段共聚物及其在制备高比表面积介孔材料中的应用

介孔材料因具有比表面积大、孔径分布均一及结构有序的特性,被广泛应用在催化剂载体、吸附材料及分离介质等领域。本文介绍了嵌段共聚物的结构特征及其在选择性溶剂中的自组装行为,综述了以嵌段共聚物为模板剂,采用溶胶-凝胶(sol gel)法制备高比表面积、高热稳定性介孔材料的控制过程,影响因素及制备非硅体系介孔材料的技术特性。     

Modified supercritical CO2 extraction of amine template from hexagonal mesoporous silica (HMS) materials: Effects of template identity and matrix Al/Si molar ratio

In this work, the primary amine template has been extracted from freshly synthesized hexagonal mesoporous silica (HMS) materials by means of modified supercritical carbon dioxide at 60–85 °C under 10.0–20.0 MPa. The influences of amine identity and matrix Al/Si ratio on the extraction efficiencies and structural properties of HMS thus obtained are investigated in detail. The results show that the extraction efficiency is strongly dependent on the pore size of the HMS materials produced by five different templates. For aluminium-incorporated samples, the extraction efficiency is observed to decrease with the Al/Si molar ratio since as the Al/Si molar ratio increases, more amine will get protonated and the matrix/template interactions become stronger, subsequently rendering the extraction more difficult and the efficiency decrease. The formic acid modifier has resulted in better extraction performance than methanol, yielding higher extraction efficiencies. The SFE-treated materials exhibit better structural properties like higher pore volume and specific surface area as compared to those prepared by conventional calcinations. Besides, results of pyridine adsorption and conversion of 2-propanol to propylene suggest that the SFE-treated HMS materials may have higher acidity than the directly calcined samples.     

以聚苯乙烯为模板制备有序大孔氧化铝

采用少皂乳液聚合法成功制备了单分散的聚苯乙烯微球,以微球自组装后的聚苯乙烯胶体晶体为大孔模板,铝溶胶为前驱体填充模板,干燥焙烧除去模板后制备了氧化铝载体。用激光粒度仪、扫描电镜、X射线衍射和氮气吸脱附对聚苯乙烯胶体晶体和氧化铝载体进行了表征。结果表明:少皂乳液聚合法制备的聚苯乙烯微球具有粒径较小(100~350 nm)、单分散性好(0.005)、收率高(约80%)等优点;自组装的胶体晶体呈规则有序排列,微球表面光滑洁净,并以此为模板成功制备了具有三维有序结构的、大孔孔径可调的氧化铝材料。     

凹凸棒NaY分子筛模板炭材料的制备及其电化学性能研究

以凹凸棒为原料,采用水热原位晶化法合成了NaY分子筛,然后采用模板法以制备得到的纳米级NaY分子筛为模板,麦芽糖为碳源,制备得到一种微孔模板炭材料。采用XRD、FESEM、N2吸附/脱附等手段对NaY分子筛和微孔模板炭材料的物理性能进行表征。测试结果表明,NaY分子筛的粒径小于100 nm,比表面积为487 m2/g;模板炭材料的比表面积为789.2 m2/g、总孔容为0.62 m3/g,平均孔径为1.5 nm。随后,采用恒电流充放电测试、循环伏安测试对模板炭材料的电化学性能进行测试。恒电流充放电测试表明,当电流密度为600 m A/g时,材料的比电容可达163.3 F/g,循环伏安测试中材料表现出了良好的循环伏安曲线的矩形特征,较好的说明了材料具有良好的倍率性能。     

Hand gesture recognition using valley circle feature and Hu’s moments technique for robot movement control

Hand gesture recognition is a simpler and more natural way of human computer interaction. The goal of this paper is to detect the continuous gestures and use them to convey information for the robot movement control. So the hand gesture recognition requires fast and extremely robust. In this paper, three strategies were used to realize the hand gesture recognition: (1) the valley circle (VC) was created for the first stage of 6 fingertip numbers classification; (2) the hybrid feature vector of Hu’s moments, convexity and compactness (HCC) were constructed for the second stage of gesture recognition of the remainder unknown gesture classes; (3) a new template matching recognition (NTMR) algorithm was proposed to realize 10 gesture classes recognition. To test the hand gesture recognition method, the robot movement control system was built. It is experimental proved that the NTMR algorithm is effective and corrective for the hand gesture recognition. It increased the recognition accuracy by 4% and decreased the recognition duration by 112 ms compared with Hu’s moment method. It had good performances of the real-time hand gesture acquisition and information conveyance, and it had the invariant properties when the gesture was rotated and shifted and scaled.