超临界抗溶剂法制备金属氧化物纳米颗粒的研究进展

具有纳米尺寸的金属氧化物因其优异的催化性能而在电化学、生物医学和其他科学领域备受瞩目.目前,制备金属氧化物纳米颗粒的传统方法主要有水热法、溶剂热法、沉淀法、微乳液法、溶胶凝胶法和模板法等.然而,这些方法往往因成本偏高、存在有机溶剂残留等问题而限制了其进一步发展.为此,迫切需要开发一种制备金属氧化物纳米颗粒的新型技术来弥补传统方法的不足,促进金属氧化物纳米颗粒制备技术的发展.超临界流体是温度和压力处在物质的临界温度和临界压力之上的一种处于特殊状态的流体,其兼具气体和液体的某些性质,具有独特的溶剂化特征、近乎于零的表面张力、低粘度、易调变,具有接近液体的密度与溶解度和类似气体的扩散性质.近年来,超临界流体技术由于其温和的操作条件和独特的性质而广泛应用于化工、环境、制药等领域.其中,超临界抗溶剂法造粒因具有操作条件温和、制备颗粒大小可控、颗粒无有机溶剂残留等优点而备受瞩目.金属氧化物纳米颗粒因其本身的尺寸效应,在催化、传感、生物医学等领域具有较为良好的应用前景.本文介绍了超临界抗溶剂法制备金属氧化物纳米颗粒的基本原理、制备流程及应用,并着重探讨了不同温度、压力和溶液浓度对超临界抗溶剂法制备金属纳米颗粒粒径大小以及形貌的影响,最后对该方法面临的问题和挑战以及发展前景进行了展望.     

超临界CO_2抗溶剂法制备依折麦布颗粒

以乙醇为溶剂、超临界CO_2为抗溶剂,通过曲面响应实验设计,分别研究依折麦布质量浓度、结晶釜温度及结晶釜压力对颗粒粒径和分布的影响,对所制备的颗粒进行表征,并优化颗粒工艺参数。实验结果表明:依折麦布颗粒粒径随依折麦布质量浓度的增大而增大,随结晶釜温度的增加先减小后增大,随结晶釜压力的增加而减小;优化后的颗粒制备工艺条件为:依折麦布质量浓度为40 g/L,结晶釜温度为60.46℃,结晶釜压力为13.81 MPa,优化后依折麦布颗粒平均粒径为10.1μm。     

Pr掺杂Mg2SnO4纳米颗粒的制备及其光致发光性能

采用水热合成和低温煅烧两步法工艺制备了不同浓度(0~1.5mol%)镨掺杂锡酸镁, 通过X射线衍射(XRD)、扫描电子显微镜(SEM)及荧光光谱仪对合成的样品进行表征, 研究了Pr掺杂量对锡酸镁微观形貌的影响, 并讨论了其光致发光性能。结果表明, 所制备的Mg₂SnO₄: Pr³⁺为立方反尖晶石结构的立方纳米颗粒; 与未掺杂的Mg₂SnO₄相比, Pr掺杂浓度的增加使颗粒尺寸变大, 并使颗粒边角锐化。不同浓度Mg₂SnO₄: Pr³⁺的发射光谱表明Mg₂SnO₄: Pr³⁺样品中存在530、570 nm两处发射峰, 前者与Mg₂SnO₄基质中的氧空位有关, 后者由Pr元素³P₀-³H₅能级的跃迁造成。随着Pr掺杂浓度增加, 锡酸镁颗粒尺寸变大、发光中心增多, 使得Pr掺杂锡酸镁纳米颗粒在570 nm处的发光强度增强。     

纳米TiO2的制备、醋酸改性及催化性能研究

在硬脂酸介质中，450－900℃温度下，得到不同结构的纳米TiO2；将纳米TiO2进行醋酸处理。用X射线衍射（XRD）和透射电子显微镜（TEM）对纳米TiO2的微结构进行表征，发现，在相同温度下，经醋酸改性的纳米TiO2具有较好的均匀和分散性。纳米TiO2成功用于马来酸酐聚合反应，用红外（ＩＲ）和核磁共振（ＮＭＲ）研究了相关单体和聚合物的结构。此外，对醋酸改性纳米TiO2进行了光催化降解甲基橙研究。     

纳米Cu颗粒的制备及其微观结构

采用磁控溅射与液氮冷凝方法,在表面沉积有方华膜的电镜载网上制备支撑纳米Ｃｕ颗粒;对样品的微观结构进行了ＴＥＭ／ＥＤ观察。结果表明,用该方法制备的Ｃｕ颗粒呈球状,其尺寸基本服从正态分布。当Ｃｕ颗粒的直径为２ｎｍ时,其电子衍射花样为弥散环;当其直径大于８ｎｍ时,则一般表现出晶体结构。具有晶体结构的Ｃｕ颗粒晶格常数随其直径大小的不同,呈现出不同程度的收缩效应,与块状Ｃｕ材料相比,最大收缩量为５％。     

超临界CO2抗溶剂法制备紫杉醇缓释微球

采用超临界流体强制分散溶液技术,以D,L-聚乳酸和D,L-聚乳酸-聚乙二醇共聚物为载体材料,分别制备了紫杉醇缓释微球.通过扫描电镜、激光粒度仪检测微球外形及粒径分布;紫外吸光度法测量其载药量和包封率,恒温振荡透析法检测药物的体外释放性能;MTT法检测载药微球对Hela细胞的抑制作用.实验表明,两种载体的缓释微球球形度均较好,表面光滑,平均粒径较小,且粒径分布较窄.以聚乳酸和共聚物为载体的缓释微球载药量分别为5.4%±0.3%和5.3%±0.4%,包封率分别为51%±3%和45%±3%;药物释放呈缓释模式,共聚物载药微球药物释放速率较快.MTT法检测结果表明,载药微球对Hela细胞的增殖有明显抑制,共聚物载药微球对细胞增殖抑制更为明显.     

反相微乳技术制备MoS_2纳米颗粒

采用CTAB/甲苯/正丁醇/水反相微乳体系,以四硫代钼酸铵(ATTM)为前驱体,盐酸羟铵作为还原剂,合成了纳米MoS2半导体材料。研究了在常温常压下ω0、反应体系酸度、退火温度对产物MoS2晶相、形貌和尺寸的影响,并探讨了其有关光学性能。     

纳米CoFe_2O_4颗粒制备及性能研究

铁酸钴具有很多优良特性,应用广泛,其制备方法多为微乳液法,本文中用化学共沉淀法制备了纳米CoFe2O4颗粒。将Co2+和Fe3+的混合液加入沉淀剂溶液中,选用NaOH作为沉淀剂,探讨了温度、保温时间以及NaOH的加入方式对颗粒粒径的影响。用激光粒度分析仪、SEM、XRD、VSM测试了颗粒的大小、形貌、分散状况及饱和磁化强度。结果表明:在制备过程中,适当降低反应温度,缩短反应时间,快速加入NaOH可减小颗粒的粒径,且用此法制备出的CoFe2O4粉末饱和磁化强度为46.776A·m2/kg。     

纳米颗粒分布对镁基复合材料强化机制的影响

Orowan强化、热错配强化和Hall-Petch强化是纳米颗粒增强镁基复合材料的主要强化机制,纳米颗粒在基体中的分布状态对起主导作用的强化机制具有重要影响.本文中对现有强化机制模型进行了适当修正,以纳米SiC颗粒增强AZ91D复合材料为例,通过理论计算分析了纳米颗粒完全分布于晶内、完全分布于晶界、在晶内晶界上均有分布的三种状态对镁基复合材料屈服强度的影响,并与实验结果进行对比.结果表明:颗粒完全分布于晶内时,增强效果最好,主要增强机制为Orowan强化;颗粒完全分布于晶界上时,增强效果最差,主要增强机制为Hall-Petch强化.颗粒在晶内晶界上均有分布时,多种强化机制共同发挥作用,增强效果随着晶内与晶界上颗粒比例的减小而逐渐减弱.     

超临界抗溶剂法纳米Al_2O_3-ZrO_2颗粒的制备与表征

以CO2为抗溶剂介质,无水乙醇为溶剂,采用超临界抗溶剂法(SAS)制备了纳米Al2O3-ZrO2复合氧化物颗粒的前驱体—纳米Al(NO3)3-Zr(NO3)4颗粒,系统考察了温度和压力等因素对制备过程的影响,并对前驱体中Al、Zr组分的共抗溶剂效应进行了研究,通过焙烧前驱体Al(NO3)3-Zr(NO3)4制得了纳米Al2O3-ZrO2球形颗粒.采用热重质谱(TG-MS)、X射线衍射(XRD)、X射线光电子能谱(XPS)、场发射透射电镜(FEG-TEM)和程序升温还原(TPR)等技术对所制备的前驱体Al(NO3)3-Zr(NO3)4和Al2O3-ZrO2纳米颗粒的物化性能进行了表征,初步考察了Al2O3-ZrO2纳米颗粒负载Ni催化剂的还原性能.研究发现,该纳米复合氧化物比用浸渍?沉淀法制得的Al2O3-ZrO2载体对活性组分Ni具有更好的分散性能,作为新型催化剂载体材料有良好的应用前景.     

Supercritical Antisolvent Process Applied to the Pharmaceutical Industry

Pharmaceutical preparations are the final product of a technological process that gives the drugs the characteristics appropriate for easy administration, proper dosage, and enhancement of the therapeutic efficacy. The design of pharmaceutical preparations in nanoparticulate form has emerged as a new strategy for drug delivery (Pasquali, Bettini, and Giordano, 2006 Pasquali , I. , R. Bettini , and F. Giordano . 2006 . Solid-state chemistry and particle engineering with supercritical fluids in pharmaceutics . Eur. J. Pharm. Sci. 27 : 299 – 310 .[Crossref], [PubMed], [Web of Science ®] , [Google Scholar]). Particle size (PS) and particle size distribution (PSD) are critical parameters that determine the rate of dissolution of the drug in the biological fluids and, hence, have a significant effect on the bioavailability of those drugs that have poor solubility in water, for which the dissolution is the rate-limiting step in the absorption process (Perrut, Jung, and Leboeuf, 2005 Perrut , M. , J. Jung , and F. Leboeuf . 2005 . Enhancement of dissolution rate of poorly-soluble active ingredients by supercritical fluid processes: Part I: Micronization of neat particles . Int. J. Pharm. 288 : 3 – 10 .[Crossref], [PubMed], [Web of Science ®] , [Google Scholar]; Van Nijlen et al., 2003 Van Nijlen , T., G. Van Den Mooter , R. Kinget , P. Augustijns , N. Blaton , and K. Brennan . 2003 . Improvement of the dissolution rate of artemisinin by means of supercritical fluid technology and solid dispersions . Int. J. Pharm. 254 : 173 – 181 .[Crossref], [PubMed], [Web of Science ®] , [Google Scholar]). Supercritical antisolvent (SAS) processes have been widely used to precipitate active pharmaceutical ingredients (APIs) (Chattopadhyay and Gupta, 2001 Chattopadhyay , P. , and R. B. Gupta . 2001 . Production of antibiotic nanoparticles using supercritical CO₂ as antisolvent with enhanced mass transfer . Ind. Eng. Chem. Res. 40 : 3530 – 3539 .[Crossref], [Web of Science ®] , [Google Scholar]; Rehman et al., 2001 Rehman , M. , B. Y. Shekunov , P. York , and P. Colthorpe . 2001 . Solubility and precipitation of nicotinic acid in supercritical carbon dioxide . J. Pharm. Sci. 90 : 1570 – 1582 .[Crossref], [PubMed], [Web of Science ®] , [Google Scholar]) with a high level of purity, suitable dimensional characteristics, narrow PSD, and spherical morphologies. The SAS process is based on the particular properties of the supercritical fluids (SCFs). These fluids have diffusivities two orders of magnitude larger than those of liquids, resulting in a faster mass transfer rate SCF properties (solvent power and selectivity) can be also adjusted continuously by altering the experimental conditions (temperature and pressure). As a consequence, SCFs can be removed from the process by a simple change from the supercritical to room conditions, which avoids difficult post-treatments of waste liquid streams. Carbon dioxide (CO₂) at supercritical conditions, among all possible SCFs, is largely used because of its relatively low critical temperature (31.1°C) and pressure (73.8 bar), low toxicity, and low cost. In this article, we show some results about processed antibiotics (ampicillin and amoxicillin), two of the world's most widely prescribed antibiotics, when they are dissolved in 1-methyl-2-pyrrolidone (NMP) and carbon dioxide is used as antisolvent.     

Formation of PLLA-PEG-PLLA Microparticles by Supercritical Antisolvent Process

A biodegradable triblock copolymer of poly(L-lactide)–poly(ethylene glycol)–poly(L-lactide) (PLLA-b-PEG-b-PLLA) was synthesized via a new process by the ring-opening polymerization of L-lactide with PEG as macroinitiator and Sn(Oct)₂ as catalyst. The structure and molecular weight of the polymer were characterized by ¹H NMR spectra, Fourier transform infrared spectroscopy (FTIR), and gel permeation chromatography (GPC). Then the microparticles were prepared with the synthesized copolymer by supercritical antisolvent (SAS) process. The optimal operating conditions were explored using an orthogonal array design. The effects of the mixed organic solvent, the concentration of polymer solution and the flow rate of polymer solution on the morphology and thermal properties of the microparticles were investigated experimentally. The morphology, size and thermal properties of microparticles were characterized by scanning electron microscopy (SEM), laser particle size analyzer, x-ray diffractometer (XRD) and differential scanning calorimeter (DSC) respectively. The results indicated that the use of mixed solvent (dichloromethane/acetone) and the polymer concentration played important roles on particle morphology, size and size distribution. In addition the PLLA-PEG-PLLA particles prepared by supercritical antisolvent process have less crystalline.     

Preparation of Theophylline-Hydroxypropylmethylcellulose Matrices Using Supercritical Antisolvent Precipitation: A Preliminary Study

ABSTRACT

Several controlled release systems of drugs have been elaborated using a supercritical fluid process. Indeed, recent techniques using a supercritical fluid as a solvent or as an antisolvent are considered to be useful alternatives to produce fine powders. In this preliminary study, the effect of Supercritical Anti Solvent process (SAS) on the release of theophylline from matrices manufactured with hydroxypropylmethylcellulose (HPMC) was investigated. Two grades of HPMC (HPMC E5 and K100) as carriers were considered in order to prepare a sustained delivery system for theophylline which was used as a model drug. The characterization of the drug before and after SAS treatment, and the coprecipitates with carriers, was performed by X-ray Diffraction (XRD) and Differential Scanning Calorimetry (DSC). The dissolution rate of theophylline, theophylline-coprecipitates, and matricial tablets prepared with coprecipitates were determined. The physical characterizations revealed a substantial correspondence of the drug solid state before and after supercritical fluid treatment while drug-polymer interactions in the SAS-coprecipitates were attested. The dissolution studies of the matrices prepared compressing the coprecipitated systems showed that the matrices based on HPMC K100 were able to promote a sustained release of the drug. Further, this advantageous dissolution performance was found to be substantially independent of the pH of the medium. The comparison with the matrices prepared with untreated substances demonstrated that matrices obtained with SAS technique can provide a slower theophylline release rate. A new mathematical model describing the in vitro dissolution kinetics was proposed and successfully tested on these systems.     

超临界抗溶剂技术在制备超细微粒中的应用研究进展

超临界流体抗溶剂技术可以用于制备微细材料,在高分子、医药、电子和化学工业中都具有广阔的应用前景.综述了超临界抗溶剂技术在制备超细微粒方面的应用研究进展.尤其详细介绍了利用超临界抗溶剂技术在制备生物降解聚合物及药物制剂方面的研究现状.     

Supercritical Antisolvent Precipitation of Ethyl Cellulose

Supercritical antisolvent (SAS) technique is an appropriate process to obtain micro- and nanoparticles. The application of this process has, until now, been explored in a variety of different fields including: explosives, polymers, pharmaceutical compounds, colouring matter, superconductors, catalysts, and inorganic compounds. Biocompatible and biodegradable polymers are playing more and more important roles in pharmaceutical areas such as tissue engineering and drug delivery. Formulation of these polymers into suitable solid-state forms plays an important role in safety, stability, and efficiency of the products. Ethyl cellulose is commonly used as drug carrier in controlled delivery systems. In this work, particles of ethyl cellulose have been precipitated by SAS using CO₂ as antisolvent and dichloromethane (DCM) as solvent. We studied the effects of concentration on the particle size distribution (PSD) of the precipitates. Ethyl cellulose size-controlled particles have been produced in the micrometer range 3.8–5.0 μm, and an increase of the mean particle diameter (MPD) was observed with the increase of the concentration of the solution.     

超临界CO2制备三元乙丙橡胶微孔泡沫

本工作采用超临界CO2作为物理发泡剂,通过快速泄压法制备了三元乙丙橡胶(EPDM)微孔泡沫材料,并系统深入地研究了发泡条件及硫化条件对EPDM泡沫结构等方面的影响.通过一系列的实验发现:硫化条件决定EPDM基体的强度、交联度以及弹性,是泡孔结构形成的关键因素,预硫化程度过高或过低都不利于形成较好的泡孔结构;scCO2饱和温度降低有利于制备孔径更小的泡孔;scCO2饱和压力的增大明显改善了泡孔形貌的规整度,提高了泡孔的均匀性,泡孔的密度随饱和压力的升高而呈指数级增加;不同硫化条件和发泡条件下制得的EPDM基微孔泡沫,其最小平均孔径达到了1.24μm,最大孔密度达到了1.33×1011个/cm3.     

Recent Developments in Materials Synthesis and Processing Using Supercritical CO2

The chemical and physical properties of carbon dioxide in the liquid or supercritical state differ quite strongly from those of conventional liquid organic solvents. These differences may be exploited in a wide variety of materials applications. Here we describe recent research involving the use of dense carbon dioxide in the areas of porous organic materials, coatings and lithography, metal nanoparticle synthesis, and biomaterials processing.     

超临界干燥制备PSNB气凝胶及其超疏水性能研究

以聚硼硅氮烷为原料,二乙烯苯为交联剂,通过硅氢加成反应结合超临界干燥工艺制备聚硼硅氮烷气凝胶。利用红外光谱、扫描电镜、比表面积与孔径分析仪对所制备气凝胶的形成及微观结构进行了分析,并通过接触角仪对样品的疏水性能进行了研究。结果表明:聚硼硅氮烷和二乙烯苯通过硅氢加成反应制得聚硼硅氮烷气凝胶;所制备的气凝胶的比表面积为307~458cm~2/g,孔体积为1.20~2.17cm~3/g,孔径分布为2.0~100nm,是一种具有三维网状结构的介孔材料,并具有超疏水性能,且当起始溶剂体积分数为85%时,气凝胶疏水性能最佳,接触角为151.5°。     

琼脂糖醋酸酯纳米粒子的制备及药物缓释性

通过纳米沉淀法制备了一种粒径均一的琼脂糖醋酸酯纳米粒子,并对影响粒径的相关因素进行了研究。结果表明,纳米粒子分别随着二甲基亚砜(DMSO)与水的比率、姜黄素含量及琼脂糖醋酸酯(AA)的浓度的增加而增大,随转速的增加而下降,异丙醇和聚乙烯醇(PVA)浓度也有一定的影响。同时研究了载体对姜黄素的包载情况及缓释行为。结果显示,无异丙醇组中姜黄素载药率和包封率均比异丙醇组中的高。但两组都表明,随着姜黄素的含量增加,载药粒子的载药率不断增加,包封率不断降低。载药粒子大大延长了姜黄素的缓释时间。获得的琼脂糖醋酸酯纳米粒子可望用于姜黄素的控释。     

超临界二氧化碳介质中纳米颗粒合成研究进展

在超临界流体介质中制备纳米颗粒是一项纳米颗粒合成的新技术.介绍了超临界流体的特性,综述了超临界流体快速膨胀、超临界流体抗溶剂、超临界流体干燥、超临界流体微乳液、超临界二氧化碳制动沉降法等技术的原理、影响因素、应用研究及发展前景.利用超临界流体较好的溶解、扩散和传质能力,可制备出性能优异的纳米颗粒.