Preparation of high-purity monodisperse silica microspheres by the sol-gel method coupled with polymerization-induced colloid aggregation

Ultra-pure mesoporous silica microspheres with good monodispersity were synthesized in two steps： nanometer-sized silica sol was produced by the sol-gel process, then micrometer-sized silica microspheres were synthesized by polymerization-induced colloid aggregation of the silica sol. The total metal content of the microspheres was extremely low, which eliminated the tailing of chromatographic peaks by chelating reagents. The pore structure of the silica microspheres could be controlled by altering the sol-gel conditions. The silica microsphere particle size could be adjusted by using different polymerizationinduced colloid aggregation conditions.

Fabrication and Characterization of Au Nanoparticle-aggregated Nanowires by Using Nanomeniscus-induced Colloidal Stacking Method

We fabricate and characterize Au nanoparticle-aggregated nanowires by using the nano meniscus-induced colloidal stacking method. The Au nanoparticle solution ejects with guidance of nanopipette/quartz tuning fork-based atomic force microscope in ambient conditions, and the stacking particles form Au nanoparticle-aggregated nanowire while the nozzle retracts from the surface. Their mechanical properties with relatively low elastic modulus are in situ investigated by using the same apparatus.

Effect of local environment in resonant domains of polydisperse plasmonic nanoparticle aggregates on optodynamic processes in pulsed laser fields

Interactions of pulsed laser radiation with resonance domains of multiparticle colloidal aggregates having an increasingly complex local environment are studied via an optodynamic model. The model is applied to the simplest configurations, such as single particles, dimers, and trimers consisting of mono- and polydisperse Ag nanoparticles. We analyze how the local environment and the associated local feld enhancement by surrounding particles affect the optodynamic processes in domains, including their photomodification and optical properties.

Coupling effect of Brownian motion and laminar shear flow on colloid coagulation:a Brownian dynamics simulation study

Simultaneous orthokinetic and perikinetic coagulations（SOPCs） are studied for small and large Peclet numbers（P e） using Brownian dynamics simulation.The results demonstrate that the contributions of the Brownian motion and the shear flow to the overall coagulation rate are basically not additive.At the early stages of coagulation with small Peclet numbers,the ratio of overall coagulation rate to the rate of pure perikinetic coagulation is proportional to P 1/2 e,while with high Peclet numbers,the ratio of overall coagulation rate to the rate of pure orthokinetic coagulation is proportional to P 1/2 e.Moreover,our results show that the aggregation rate generally changes with time for the SOPC,which is different from that for pure perikinetic and pure orthokinetic coagulations.By comparing the SOPC with pure perikinetic and pure orthokinetic coagulations,we show that the redistribution of particles due to Brownian motion can play a very important role in the SOPC.In addition,the effects of redistribution in the directions perpendicular and parallel to the shear flow direction are different.This perspective explains the behavior of coagulation due to the joint effects of the Brownian motion（perikinetic） and the fluid motion（orthokinetic）.

Characterization and stability of sedimentary colloids in different ecology regions in Taihu Lake

Colloidal particles,heterogeneous mixture with various organic components and continuous molecular weight(MW)distribution,is omnipresent in lake sediments and substantially influence the retention,transportation,and fate of contaminants in lake ecosystem.We sampled and extracted sedimentary colloids from different ecology regions in Taihu Lake,Jiangsu,East China,in June 2020,and they were further separated into four different particle size ranges by tangent ultrafiltration,and the properties of colloids were studied in various methods,including zeta potential analysis,transmission electron micrograph images(TEM),Fourier transformation infrared(FTIR),and 3D fluorescence.Results show that the surface of the colloids is covered with organic macromolecular substances,such as humuslike substances and protein-like substances.There were significant differences in molecular weight and fraction content of colloids in the sediments from macrophyte-dominant(MD)area and algae-dominant(AD)area in the lake.Colloids from MD area are mainly composed of humic acid,protein,and fulvic acid;the content of fulvic acid is lower than that of humic acid and protein.The humic acid exists mainly in small molecular weight(10-100 kDa),protein exists in mainly large molecular weight colloids(0.45-1μm).Colloids from AD area are mainly composed of humic acid,and mainly distributed in the molecular weight(10 kDa-0.45μm).The presence of humic acid inhibits effectively the agglomeration of the colloids.Especially,the stability of colloids is closely related to the molecular weight,with low molecular weight from MD area show higher stability.The existence of humic acid in colloids increases the electrostatic repulsion between colloidal particles,which can effectively inhibit the agglomeration of colloids,thus enhancing the stability of colloids.Furthermore,both monovalent and divalent electrolytes enhance colloidal aggregation,and the low-molecular-weight(LMW)colloid fraction exhibits higher stability efficiency than the high-molecular-weight(HMW)colloidal.

Colloid Thin-Layer Chromatography: A Tool for Gold Sols Validation before Used in Application

Gold nanoparticles have been increasingly used in catalysis, biomedical imaging, biological and chemical sensing, drug delivery, etc. In this study, a straightforward method that allows one to monitor the synthesis of gold sols and their aging, before their fine characterization by sophisticated techniques and before their use is described. Indeed, the “Colloid Thin-Layer Chromatography” method allows one to check the quality of gold colloidal sols during the synthesis. It is also well adapted for monitoring the aging of the sol before the visual observation of its degradation.

Restructuring of plasmonic nanoparticle aggregates with arbitrary particle size distribution in pulsed laser fields

We have studied processes of interaction of pulsed laser radiation with resonant groups of plasmonic nanoparticles（resonant domains） in large colloidal nanoparticle aggregates having different interparticle gaps and particle size distributions.These processes are responsible for the origin of nonlinear optical effects and photochromic reactions in multiparticle aggregates.To describe photo-induced transformations in resonant domains and alterations in their absorption spectra remaining after the pulse action,we introduce the factor of spectral photomodification.Based on calculation of changes in thermodynamic,mechanical,and optical characteristics of the domains,the histograms of the spectrum photomodification factor have been obtained for various interparticle gaps,an average particle size,and the degree of polydispersity.Variations in spectra have been analyzed depending on the intensity of laser radiation and various combinations of size characteristics of domains.The obtained results can be used to predict manifestation of photochromic effects in composite materials containing different plasmonic nanoparticle aggregates in pulsed laser fields.

Effects of humic acid and surfactants on the aggregation kinetics of manganese dioxide colloids

The aggregation of common manganese diox- ide （MnO2） colloids has great impact on their surface reactivity and therefore on their fates as well as associated natural and synthetic contaminants in engineered （e.g. water treatment） and natural aquatic environments. Nevertheless, little is known about the aggregation kinetics of MnO2 colloids and the effect of humic acid （HA） and surfactants on these. In this study, the early stage aggregation kinetics of MnO2 nanoparticles in NaNO3 and Ca（NO3）2 solutions in the presence of HA and surfactants （i.e., sodium dodecyl sulfate （SDS）, and polyvinylpyrrolidone （PVP）） were modeled through time-resolved dynamic light scattering. In the presence of HA, MnO2 colloids were significantly stabilized with a critical coagulation concentration （CCC） of-300mmol · L-1 NaNO3 and 4 mmol.L-1 Ca（NO3）2. Electrophoretic mobility （EPM） measurements confirmed that steric hindrance may be primarily responsible for increasing colloidal stability in the presence of HA. Moreover, the molecular and/or chemical properties of HA might impact its stabilizing efficiency. In the case of PVP, only a slight increase of aggregation kinetics was observed, due to steric reactions originating from adsorbed layers of PVP on the MnO2 surface. Consequently, higher CCC values were obtained in the presence of PVP. However, there was a negligible reduction in MnO2 colloidal stability in the presence of 20 mg·L-1SDS.

Study of asphaltene reaggregation in toluene/heptane mixture by dynamic and static light scattering

This paper presents the study of the effect of multiple ultrasonic impacts on submicron asphaltene aggregates in a toluene/heptane solution,conducted with dynamic light scattering technique.The objects of the study were four samples of asphaltenes obtained from four different oils.For all samples,the change in the average size of the asphaltene submicron aggregates with time was measured after the addition of a precipitant(heptane)to a solution of asphaltenes in toluene at an amount above the threshold concentration.Asphaltene aggregates formed in solution after the addition of the precipitant and were subjected to ultrasonic treatment,which led to the destruction of the asphaltene aggregates.Aggregation of destroyed asphaltenes was observed.The kinetics of this aggregation were similar to the kinetics of aggregation of asphaltenes after the addition of a precipitant.Multiple iterations of asphaltene aggregate destruction in the sample led to a significant change in the kinetics of aggregation:the growth of aggregates slowed and stabilized at a size of approximately 200 nm and 30 nm for the different studied samples.

Effects of low molecular weight organic acids on aggregation behavior of biochar colloids at acid and neutral conditions

Low molecular weight organic acids(LMWOAs),as active components in the rhizosphere carbon cycling,may influence the environmental behaviors of biochar colloids.This study selected the pine-wood and wheat-straw biochars(PB and WB)as two typical biochars.The effects of typical LMWOAs(oxalic acid,citric acid,and malic acid)on aggregation kinetics of PB and WB colloids were investigated under pH 4 and 6 conditions.Critical coagulation concentrations(CCCs)of both PB and WB colloids were decreased with the LMWOAs regardless of the types of biochar and the solution pH,and the most significant effect occurred in pH 4 due to more LMWOAs sorption on the biochar colloids.The different types of LMWOAs caused various CCCs changes.For example,the CCC values of PB colloids decreased from 75 mM to 56,52,and 47 mM in the pH 4 NaCl solutions when 1 mM oxalic acid,citric acid,and malic acid were present in the suspensions,respectively.The chemical structure(functional groups)and molecular weight of LMWOAs,solution pH,and the electrophoretic mobility(EPM)of biochar co-influence the interactions between biochar colloids and LMWOAs,thus affecting the stability of biochar colloids in the presence of LMWOAs.The presence of LMWOAs accelerated the aggregation of colloidal biochar by increasing the interaction of surface bridging bonds(hydrogen bonding)and decreasing the repulsive force between colloidal biochar particles.This study showed that LMWOAs could accelerate the aggregation of biochar colloids in acidic or neutral environments and reduce the mobility of biochar colloids in soil rhizosphere.

高比表面积微米级全多孔二氧化硅微球的制备

介绍了用双模板法制备全多孔硅胶纳米粒子,该法制得的纳米级二氧化硅微球孔径为18.3 nm,比表面积为589.5 m^(2)·g^(-1),孔隙率为2.7 cm^(3)·g^(-1),以制备的硅胶纳米粒子为硅源,利用聚合诱导胶体聚集法制备具有高比表面积的微米级全多孔二氧化硅微球。利用透射电子显微镜和扫描电子显微镜表征产品的形态,颗粒的尺寸分析在Mastersizer 2000上进行。结果表明,利用该方法能够制备具有较大介孔结构且具有较高比表面积的微米级全多孔二氧化硅微球,制得的二氧化硅微球具有较大介孔,为35.2 nm,比表面积达到756.2 m^(2)·g^(-1),孔隙率为2.0 cm^(3)·g^(-1)。

不同电解质体系中土壤胶体凝聚动力学的动态光散射研究

利用动态光散射技术研究在不同浓度的KNO3和Mg(NO3)2中土壤胶体颗粒的凝聚过程动力学.通过分析凝聚过程中光强和有效粒径随时间的变化得到:(1)根据凝聚过程中光强的稳定与否,可以判断土壤胶体凝聚过程中碰撞的发生是由布朗运动支配还是由重力作用支配;(2)在不同的电解质体系下土壤胶体凝聚表现为快速凝聚特征或不同的慢速凝聚特征,并且在慢速凝聚中存在一个对重力敏感的电解质浓度;(3)两种电解质作用下的土壤胶体凝聚特征相似,但对Mg(NO3)2体系浓度变化的敏感性远远大于KNO3体系.此外,通过分析凝聚平均速率随电解质浓度的变化,找到慢速凝聚与快速凝聚的电解质浓度转折点,即临界絮凝浓度(CFC),提供了一个实验测定CFC的可能方法.

白及不同提取部位对家兔血小板聚集的影响

目的探讨白及不同提取部位对家兔血小板聚集的影响。方法比浊法测定血小板聚集率。结果白及正丁醇提取部位和水溶性部位可显著升高腺苷二磷酸(ADP)诱导的血小板最大聚集率,而乙酸乙酯提取部位可显著抑制ADP诱导的血小板聚集,石油醚提取部位对ADP诱导的血小板聚集无显著影响。各提取部位对血小板数无显著影响。结论白及正丁醇提取部位和水溶性部位是白及止血作用的主要有效部位,其止血作用与其促进血小板聚集作用有关。

重力场和电解质浓度对胶体凝聚体分形结构的影响

运用李航等提出的新方法,克服了DLVO理论中无法理论计算不同电解质浓度下颗粒的表面电位这一困难,从而可以直接计算出不同电解质浓度下胶体颗粒间的位能.同时,还运用胶体颗粒动能的玻耳兹曼分布原理和蒙特卡罗方法来模拟胶体的运动,并采用非弹性碰撞理论解决了碰撞后凝聚的有效概率问题.在改进DDA模型的基础上,成功地建立了以往的模拟中未能建立的重力场中电解质浓度与碰撞凝聚概率间的联系,结果发现,(1)重力场作用下的凝聚体分形维数随电解质浓度变化的曲线完全不同于无重力条件下的曲线.无重力作用下,凝聚结构体分形维数随电解质浓度的变化比较缓慢,曲线呈“L”形;而重力作用下的分形维数则呈明显的“S”形曲线.(2)在重力条件下,慢凝聚包括两个区域,对电解质浓度不敏感区域和敏感区域.在敏感区域存在一个电解质浓度的拐点.(3)无重力条件下,不同大小的胶体颗粒在快凝聚时的分形维数都是在1.86±0.01.当电解质浓度降低,凝聚速率变慢,分形维数增加,最大达到2.01±0.02,但不会形成重力条件下的分形维数接近3的结构体.

相转化对均匀胶粒的形貌及团聚度的影响

The inflence of the additives, NaH2PO4 and 1-hydroxyethylidene-1,1’-diphosphonic acid (HEDP), the concentration of HNO3 and the temperature of reaction on the phase transfor-mation and aggregation of Fe2O3 particles obtained by the boiling reflux of 0.2mol-1 Fe(NO3)3 solution has been studied using TEM and XRD. Phosphate gave monodispersed spindle-shaped α-Fe2O3 perticles used as magnetic recording material. Nanowhiskers of α-Fe2O3 was formed in the presence of HEDP and HNO3. The method is provisionally referred to as the inhibitory sub-crystal aggregation method.

各向异性胶体基底表面的分形凝聚体

对各向异性胶体基底表面的分枝状金原子凝聚体的生长机制进行了研究。沉积在无规杂质区域的熔融玻璃表面的金原子先形成网状结构的薄膜 ,然后逐渐演变成分枝状凝聚体。根据这一实验结果 ,建立了各向异性的团簇 团簇凝聚模型 ,对此类胶体基底表面的金原子分枝状凝聚体的生长全过程进行了计算机模拟 ,研究了杂质区域对凝聚体各种参数的影响 。

正电性胶态纳米银中加入凝聚剂后的表面增强拉曼光谱

在柠檬酸还原制备的正电性胶态纳米银中加入凝聚剂HNO3和NaNO3后,用波长为633 nm的激光激发,获得了较强的表面增强拉曼散射光谱(SERS谱),通过讨论及实验明确该SERS谱是来自于还原剂中的柠檬酸根离子,并说明该方法制备的纳米银的吸附层是带正电的银离子,扩散层是带负电的柠檬酸根离子。

重迎茬大豆对土壤有机-无机复合胶体及土壤结构的影响

重、迎茬大豆对黑土和暗棕壤的影响为：有机质、重组有机质、复合有机质及复合度均为重、迎茬低于正茬，石灰性黑钙土则相反；复合体中不同结合态腐殖质及Ｅ４／Ｅ６变化不尽相同：水稳性团聚体在三种土壤中重、迎茬呈下降趋势，重迎茬对土壤结构有损伤。

重质油胶体聚集结构的耗散粒子动力学模拟

重质油是以沥青质为胶核分散于饱和油分中形成的极其复杂的胶体体系.本文采用耗散粒子动力学(DPD)方法研究重质油的胶体结构及其影响因素.根据重质油各组分的分子结构特征,构建了描述重质油组分的粗粒化模型化合物.模拟结果表明,本文构建的粗粒化模型能很好地反映重质油的胶体聚集结构.沥青质分子结构对胶体聚集结构有序性有显著影响,较高稠合程度的芳香环结构将使胶束结构有较高的有序性,烷基侧链则表现出分散作用.重质油中的胶质具有胶溶作用,胶质与沥青质的浓度比存在一个极限,当小于这个极限时,重质油将出现聚沉.

基于SERS技术检测牛奶中氨苄西林的研究

目的利用表面增强拉曼光谱(SERS)检测牛奶样品中的氨苄西林,对其进行定性及半定量分析。方法首先构建了新型氧化铝陶瓷SERS检测平台。其次对氨苄西林的拉曼特征峰进行了归属,并确定了最佳的实验条件。然后对水溶液中的氨苄西林进行了SERS检测,并获得了检测限。最后进行了牛奶样品中的氨苄西林的检测,并利用线性拟合实现了对加标牛奶样品中氨苄西林的半定量分析。结果牛奶样品中的氨苄西林的检测限为10-3g/L,在10-3~10-1g/L浓度范围内,拉曼特征峰1000cm-1的强度随牛奶样品中氨苄西林的浓度的线性关系为y=23408.93x+1801.47,相关系数为0.993,回收率在95.0%~110.0%之间。结论包括对牛奶样品的预处理过程(约5min)在内,整个SERS检测过程不超过7min。该方法对牛奶中的污染物进行定量和定性分析具有广阔的应用前景。