Characterization of Sub‐Micron Perovskite Suspensions Formed Through Cavitation Processing

The size distribution within and electrokinetic properties of aqueous perovskite (LaCoO₃) suspensions, have been characterized as a function of processing conditions. Submicron–sized perovskite particles have been obtained using a cavitation technique in which the suspension is passed through a series of small orifices under extreme driving pressure drops. When no additives were used, the zeta potential of the particles was found to be positive over the entire pH range studied. Use of an acrylic copolymer surfactant with multiple negatively charged sites during the cavitation processing was found to improve dispersion stability. The observed variations in zeta potential and particle size for the suspensions are explained in terms of electrostatic interactions between particles, the tendency for the surfactant to adsorb onto the particles, and the degree of steric stabilization provided by the surfactant.     

Analysis of Anionic Polymer Dispersant Behavior in Dense Silicon Nitride and Carbide Suspensions Using an AFM

The paper focuses on the interaction mechanism caused by anionic polymer dispersants in dense silicon nitride and silicon carbide suspensions. An atomic force microscope (AFM) was used to determine the relationship between the macroscopic suspension viscosity and the microscopic structure adsorbing of a polymer dispersant at the solid/liquid interface. The surface interactions within the suspensions were analyzed under various dispersant pH values and additive conditions. The addition of an anionic polymer dispersant decreased the viscosity of silicon nitride and silicon carbide suspension and increased the electrosteric repulsive force on the non-oxide surface in solution at pH > 6, which was the isoelectric point of the materials. Based on the above results, we estimated the adsorption mechanism of anionic polymer dispersants on each solid surface in solution under relatively high pH conditions.     

SMA-g-MPEG comb-like polymer as a dispersant for Al2O3 suspensions

SMA-g-MPEG comb-like polymer is first employed as the dispersant of Al₂O₃ suspensions in this paper. The comb-like polymer has anionic polycarboxylate backbone, which makes the polymer easily absorbed on the cationic surface of Al₂O₃ particles; on the other hand, the comb-like polymer has hydrophilic MPEG side chains, which extend into the solution to provide steric repulsion after the comb-like polymer is absorbed on the surface of Al₂O₃ particles. The adsorption behavior, zeta potential, apparent viscosity, granularity and TEM images of the Al₂O₃ suspensions using SMA-g-MPEG as dispersant are investigated. The addition of SMA-g-MPEG improves the dispersibility and decreases the apparent viscosity of the Al₂O₃ suspension observably. The impacts of the length of side chains on the dispersion of Al₂O₃ suspensions are particularly discussed. The adsorbed molecular number of the dispersant decreased by increasing the length of side chains. The zeta potential of Al₂O₃ suspension is more negative by using comb-like polymer with shorter side chains. Based on the steric repulsion and adsorbed molecular number, SMA-g-MPEG with moderate length of side chain is found to have the best dispersibility for Al₂O₃ suspension.     

Dispersion of nano-silicon carbide (SiC) powder in aqueous suspensions

The dispersion characteristics of nanosize silicon carbide (SiC) suspension were investigated in terms of surface charge, particle size, rheological measurement and adsorption study. Ammonium polycarboxylate has been used as dispersant to stabilize the suspension. It was found that the isoelectric point (iep) of SiC powder was pH_iep (4.9). The surface charge of powder changed significantly in presence of the ammonium polycarboxylate dispersant and iep shifted significantly towards lower acidic pH (3.6). The shift in iep has been quantified in terms of ΔG ⁰ _SP, the specific free energy of adsorption between the surface sites and the adsorbing polyelectrolyte (APC). The values of ΔG ⁰ _SP (−10.85 RT unit) estimated by the electro kinetic data compare well with those obtained from adsorption isotherms (−9.521 RT unit). The experimentally determined optimum concentration of dispersant required for maximizing the dispersion was found to be 2.4 mg/g of SiC (corresponding to an adsorbed amount of 1.10 mg/g), at pH 7.5. This is much below the full monolayer coverage (corresponding to adsorbed amount of 1.75 mg/g) of the particles surface by the dispersant. The surface charge quantity, rheological, pH, electro kinetic and adsorption isotherm results were used to explain and correlate the stability of the nanosize silicon carbide in aqueous media. At pH 7.5, where both SiC surface and APC are negatively charged, the adsorption of APC was low because of limited availability of favourable adsorption sites. In addition, the brush-like configuration of the adsorbed polymer prevented close approach of any additional dispersant; hence stabilization of the slurry happens at a comparatively lower concentration than the monolayer coverage.     

Electrostatically mediated adsorption by nanodiamond and nanocarbon particles

Nanodiamond (ND) and other nanocarbon particles are popular platforms for the immobilization of molecular species. In the present research, factors affecting adsorption and desorption of propidium iodide (PI) dye, chosen as a charged molecule model, on ND and sp ² carbon nanoparticles were studied, with a size ranging from 75 to 4,305 nm. It was found that adsorption of PI molecules, as characterized by ultraviolet–visible spectroscopy, on ND particles is strongly influenced by sorbent-sorbate electrostatic interactions. Different types of NDs with a negative zeta potential were found to adsorb positively charged PI molecules, while no PI adsorption was observed for NDs with a positive zeta potential. The type and density of surface groups of negatively charged NDs greatly influenced the degree and capacity of the PI adsorbed. Ozone-purified NDs had the highest capacity for PI adsorption, due to its greater density of oxygen containing groups, i.e., acid anhydrides and carboxyls, as assessed by TDMS and TOF–SIMS. Single wall nanohorns and carbon onion particles were found to adsorb PI regardless of their zeta potential; this is likely due to π bonding between the aromatic rings of PI and the graphitic surface of the materials and the internal cavity of the horns.     

In Situ Evaluation of Nanoparticle–Protein Interactions by Dynamic Magnetic Susceptibility Measurements

The use of dynamic magnetic susceptibility measurements is reported to study nanoparticle–protein interactions in situ. The technique consists of measuring the rotational diffusivity of thermally blocked magnetic nanoparticles (MNPs) in protein solutions. To illustrate the technique, the effect of nanoparticle zeta potential in carboxymethyl‐dextran‐coated MNPs and their interaction with model anionic and cationic proteins, such as bovine serum albumin (BSA), immunoglobulin G (IgG), fibrinogen (FIBR), apo‐transferrin (TRANS), lysozyme (LYZ), and histone (HIS), in a range of protein concentrations is studied. Experiments indicate that interactions between the negatively charged particles and the negatively charged proteins BSA, IgG, FIBR, and TRANS are negligible. However, positively charged proteins LYZ and HIS readily absorb onto the nanoparticles, as evidenced by an increase in size and eventual aggregation of the particles. Onset of this effect seems to happen at a lower concentration of HIS compared with LYZ. The technique could be applied to other particle surface coatings and to particles in complex protein mixtures, such as whole blood and serum, allowing systematic in situ studies of nanoparticle–protein interactions.     

FTIR，XPS和SEM研究聚羧酸盐分散剂在吡唑醚菌酯颗粒表面的吸附性能

采用傅里叶变换红外光谱、X射线光电子能谱和扫描电子显微镜相结合的方式，从微观角度研究梳状聚羧酸盐分散剂在吡唑醚菌酯颗粒表面的吸附性能，为聚羧酸盐分散剂在吡唑醚菌酯悬浮剂中的应用提供理论依据。研究结果表明：吡唑醚菌酯吸附聚羧酸盐分散剂后，红外谱图未出现新的吸收峰，聚羧酸盐分散剂与吡唑醚菌酯之间主要是物理吸附，范德华力是聚羧酸盐分散剂与吡唑醚菌酯颗粒表面结合的主要作用力。吡唑醚菌酯颗粒吸附聚羧酸盐分散剂后，吡唑醚菌酯颗粒界面的N和Cl电子峰强度减弱，C和O电子峰强度明显增强，还出现了Na的电子峰，这主要是聚羧酸盐分散剂中C，O和Na的贡献，说明聚羧酸盐分散剂在吡唑醚菌酯颗粒表面形成了良好的吸附。并以Cl元素为特征元素，计算出聚羧酸盐分散剂在吡唑醚菌酯颗粒表面的吸附层厚度约为1.22 nm。用扫描电子显微镜研究了样品的形貌，吸附聚羧酸盐分散剂后，原本光滑的吡唑醚菌酯颗粒表面吸附了很多细小的颗粒，且有序分布，这是由于分散剂疏水集团对吡唑醚菌酯颗粒形成了包覆，亲水基团充分外露，从而有效阻止吡唑醚菌酯颗粒间的团聚，提高了吡唑醚菌酯悬浮剂的物理稳定性。     

Amino-containing magnetic nanoemulsions: elaboration and nucleic acid extraction

Amino-containing magnetic colloids were prepared from highly magnetic oil-in-water (O/W) emulsions. The functionalization was performed by controlling the adsorption of polyethyleneimine onto negatively charged magnetic emulsions. The cationic magnetic nanodroplets were characterized in terms of chemical composition, particle size, size distribution, zeta potential and colloidal stability as a function of storage time. These amino-containing magnetic emulsions were assessed as a new tool for nucleic acid extraction and amplification. The adsorption of nucleic acids was mostly controlled by attractive electrostatic interactions. The adsorption efficiency of a model RNA was found to be encouraging and the captured nucleic acid molecules were directly enzymatically amplified in the presence of the magnetic particles without any elution step.     

悬浮液进样端视电感耦合等离子体发射光谱法直接测定二氧化钛中铌

用聚丙烯酸胺(NH₄PAA)为分散剂制备二氧化钛悬浮液,并以悬浮液进样端视电感耦合等离子体发射光谱法直接测定了二氧化钛中痕量杂质铌。研究了分散剂及分散剂的量和pH对二氧化钛悬浮液稳定性的影响,通过优化条件制备得到稳定和均匀的悬浮液。研究了端视电感耦合等离子体发射光谱分析悬浮液进样的性能。本方法的检出限为3.0 μg·L-1, 相对标准偏差为3.1%(n=3, c=0.3 mg·L-1)。     

Choice of dispersants for the nano-apatite filler of polylactide-matrix composite biomaterial

The aim of this study is to compare de-aggregative ability of common organic dispersants for the acicular nano-apatite crystallite with main composition of calcium hydroxyapatite (HA) as a filler of composite containing polylactide (PLA) matrix. Firstly, the acicular nano-apatite powders with an average length of 70–120 nm were synthesized based on traditional chemical co-precipitation and freeze-drying techniques. Common organic dispersants including tetrahydrofuran, acetone, chloroform, N,N-dimethyl formamide (DMF) and ethanol were then employed to disperse synthetic freeze-dried ultra-fine nano-powders. The observations and weight of sediments showed that nano-apatite suspension dispersed by DMF and ethanol presented homogeneous and stable colloid after vigorly stirred for 24 h and then kept still for same time, respectively. Results of particle measurements and viscosity measurement illuminated that a large number of the nano-apatite particles with an average dimension of 297.86 nm and viscosity of 0.8872 cP in DMF suspension could be dispersed up to 91.28 nm by the DMF dispersant and the DMF dispersant could minimize agglomeration between the apatite ultra-fine nano-powders. DMF is a more effective and appropriate dispersant to disperse the apatite nano-fillers than chloroform, tetrahydrofuran, acetone and ethanol, when the nano-apatite/PLA composite biomaterials were prepared.     

带电多孔二氧化硅纳米颗粒在硫醇/磷脂混合双层膜上的非特异性吸附

制备了表面带阴/阳离子的多孔二氧化硅纳米颗粒, 通过QCM-D研究了颗粒在不同pH值环境下与磷脂膜的非特异性吸附情况. 结果表明, NH₂-MSN 在4–8的pH值范围内与磷脂膜相互吸引, 而COOH-MSN由于与磷脂膜的电性始终保持一致而无法发生吸附现象. 本研究能够帮助理解和预测纳米颗粒与细胞膜间的相互作用, 为药物输运提供载体, 有助于多孔二氧化硅纳米颗粒在药物输运体系中的应用. 关键词： 多孔二氧化硅纳米颗粒 磷脂膜 非特异性吸附 QCM-D     

Degree of Flocculation and Interparticles Charges of Conditioned Municipal Activated Sludge using Mixed Polymers

The present research work focuses on a new conditioning and flocculation mechanism of municipal fresh activated sludge using a dual polymer system combining cationic and anionic polyelectrolytes. Various pairs of three different types of polyelectrolytes, low molecular weight cationic polyacrylamide (CPAM-10), high molecular weight cationic polyacrylamide (CPAM-80) and an anionic polyacrylamide (APAM-30), were selected, being used either individually or as cationic-anionic pairs. The results of use of the dual systems indicated that using mixed polymers for conditioning gave lower turbidity with better settling when compared to that of using individual pure polymers. The mixed polymers improved the sludge volume index (SVI) by 62%. The zeta potentials of the supernatant and solid-like samples of conditioned activated sludge were measured. Slight increases in zeta potential, from –12 to –9, of the mixed polymers for all supernatants were observed. On the other hand, zeta measurements showed that the sludge solid-like particles retained their negative charges despite the addition of the individual cationic polymers in the mixture. This phenomenon was explained in terms of the addition of the polyelectrolytes attracting, primarily, the carboxylic groups of the fine suspended sludge particles, while hydrogen bonds between the larger sludge particles resulted in attraction in accordance with the Van der Waals mechanism, and both attractions caused an immediate dewatering that led to flocculation, but with low compactness. As a result of retaining negative charges on the large sludge particles, dissolved metals were partially attracted, causing reduction in conductivities of the supernatants of 10% to 15% for all pairs. Rheological tests showed that the formed flocs had low shear stress resistances, ranging between 0.2 and 0.4 Pa, and weak flocs strength.     

负电性纳米银的制备及性质研究

制备了一种表面带负电的胶态纳米银,用透射电镜,吸收光谱,SERS谱对该纳米银进行了研究,发现纳米银的粒径分布均匀,平均粒径为11nm,吸收峰为422nm,常温下放置7个月仍具有较强的SERS活性,当阴离子型分子吲哚丁酸,阳离子型分子碱性品红,亚甲兰及中性分子邻菲罗邻分别吸附在其上时,观察到阳离子型分子碱性品红和亚甲兰及中性分子邻菲罗邻的SERS谱,而阴离子型分子吲哚丁酸则无SERS谱出现。     

超分散剂在莠去津颗粒表面吸附的红外和拉曼光谱学研究

聚羧酸型梳状共聚物超分散剂在农药环保剂型悬浮剂的研究中起着重要的作用,可使其理化稳定件得到明显改善,因此研究聚羧酸型梳状共聚物超分散剂在莠去津颗粒表『疗i的吸附行为具有重要的理论和实际意义.利用傅里叶红外光谱(FTIR)和傅里叶拉曼光谱(FT-Raiman)对超分散剂在莠上津表面的吸附行为进行了光谱学表征,结果表明,氢...     

Adsorption of polyelectrolytes on silica and gold surfaces

The results of a study that helps understand the mechanisms of adsorption of polyelectrolytes on particles, using numerical simulation methods, specifically the one known as dissipative particle dynamics are reported here. The adsorption of cationic polyelectrolytes of two different polymerisation degrees interacting with two types of surfaces, one made of gold and the other of silica, is predicted and compared. We find that a more negatively charged wall does not necessarily adsorb more cationic polyelectrolytes because the electrostatic repulsion between the wall and the polyelectrolytes is stronger. Additionally, intra-chain repulsion plays an important role, because the largest polyelectrolyte chains have larger excluded volume than the shorter ones. In regard to the adsorption dependence on the polyelectrolyte polymerisation degree, we find that the excluded volume drives the adsorption throughout the intra-chain electrostatic repulsion, because the SiO₂ surface is strongly negative. These results are expected to be useful for several nanotechnological applications of current interest, such as in gene therapy and in the improvement of drug delivering mechanisms.     

Sonochemical preparation of polyaniline@TiO2 and polyaniline@SiO2 for the removal of anionic and cationic dyes

Polyaniline (PANI) synthesized by simple CDs (carbon dots) initiated polymerization has formed a composite with TiO₂ and SiO₂, respectively via a sonochemical method. These PANI@TiO₂ and PANI@SiO₂ composites were proven as effective adsorbent materials to rapidly adsorb the anionic and cationic dyes from wastewater at neutral pH and ambient temperature. Selected popular cationic and anionic organic dyes consisted of methylene blue (MB), brilliant blue (BB), Evans blue (EB), crystal violet (CV), Congo red (CR), rhodamine B (RB), and rhodamine 6G (R6G). The adsorption equilibria were governed by Langmuir and Freundlich isotherms. The kinetic results revealed that the PANI@TiO₂ and PANI@SiO₂ composite materials synthesized via the sonochemical method are efficient adsorbents compared to other adsorbent materials for the removal of organic dyes from the water. The adsorbed dyes were effectively desorbed from the composites, rendering the reusability of PANI@TiO₂ and PANI@SiO₂. The estimated adsorption capacities of PANI@TiO₂ and PANI@SiO₂ composites were 89, 93, 80, 94 and 74, 71, 61, 61 mg/g for MB, CR, CV, and R6G, respectively.     

Nanoparticle Probes for Quantifying Supramolecular Determinants of Biosurface Affinity

Interactions between macromolecular systems and biosurfaces are complicated by the complexity of these multivalent interactions and challenges in quantifying affinities. In this study, a library of gold nanoparticles (AuNPs) with different functional head groups as multivalent probes to quantify biosurface affinity, using hair as a model targeted substrate, is used. The adhesion of the AuNPs is quantified by inductively coupled plasma mass spectrometry. Using this method it is demonstrated that multiple supramolecular forces affect affinity. As expected, electrostatic interaction is a strong driving force for adhesion of the nanoparticle tags onto hair in aqueous solution, evidenced by a much higher level of gold adsorption for cationic AuNPs compared to anionic or neutral AuNPs. Functionalized cationic AuNPs are synthesized with systematically varied terminal groups and are screened for deposition onto hair. AuNP adhesion onto hair in water generally decreases as a function of increasing hydrophobicity; however, electron‐rich aromatic rings provide significantly enhanced attachment. Although the intact, healthy hair cuticle is considered negatively charged and hydrophobic, the findings indicate that hydrophobic interactions are not as critical to deposition of AuNPs onto hair as the electrostatic component from the presence and accessibility of the cationic moieties, which are the greatest drivers for deposition onto hair.     

Viscosity of Some Cationic Polyelectrolyte and its Potential Use as Flocculant in Solid/Liquid Separation Processes

Intrinsic viscosities of a cationic polyelectrolyte were determined in salt-free aqueous solution and aqueous/organic solvent mixtures. The investigated polyelectrolyte contains quaternary ammonium salt groups (N, N-dimethyl-2-hydroxypropylenammonium chloride), located along the main chain. In order to obtain the intrinsic viscosities, the experimental data were plotted based on the Wolf method. The results showed that the experimental data fit well with the Wolf model. From the estimated values of the intrinsic viscosities, the dependences of the polyion conformation on the polyelectrolyte concentration as well as on solvent composition were revealed. The flocculating efficiency of this polycation on a model clay suspension was studied by turbidity and zeta potential measurements as well. Moreover, flocs size measurement at the optimum polycation dose was carried out using laser diffraction technology. The results point to simultaneous contributions from both neutralization and patch mechanisms for flocculation process and a unimodal distribution in floc size.     

负电性纳米银溶胶SERS活性及稳定性的比较研究

用单宁还原硝酸银可制得表面带负电的、对阳离子型分子具有较强SERS效应的纳米银。为了进一步测试负电性纳米银溶胶的SERS活性及稳定性,在室温下用制针剂的封装机将样品(old NCS)封装并保存。两年后与新制备的负电性纳米银溶胶(new NCS)比较,用透射电镜观测发现old NCS与new NCS相比银粒子尺寸增大;用紫外可见吸收光谱测定old NCS的吸收峰为431 nm,new NCS的吸收峰为418 nm,old NCS与new NCS相比吸收峰发生红移。为比较old NCS及new NCS的SERS活性选取阳离子型分子、中性分子及阴离子型分子作为测试分子,用拉曼光谱仪测试这些分子在两种纳米银上的SERS谱,结果发现,阳离子型分子碱性品红、中性分子吖啶橙在old NCS及new NCS上SERS较强,阳离子型分子亚甲基蓝在old NCS上与在new NCS上相比SERS较弱,阴离子型分子苯甲酸在old NCS及new NCS均未观察到SERS信号。     

Enhanced Fluorescence of Graphene Oxide by Well-Controlled Au@SiO2 Core-Shell Nanoparticles

Graphene and graphene derivatives, including graphene oxide (GO) and reduced GO (rGO), have attracted remarkable attention in different fields due to their unique electronic, thermal, and mechanical properties, whereas the fluorescence property is rarely been studied. This paper reports on metal-enhanced fluorescence Au@SiO₂ composite nanoparticles adsorbed graphene oxide nanosheets, where the silica-shell is used to control the distance between gold-core and fluorophore GO, and a positively charged polyelectrolyte poly(allylamine hydrochloride) (PAH) is used to adsorb the negatively charged silica-shell and GO by layer-by-layer assembly (LbL) approach. The silica-shell around the 80 nm gold-core can be well-controlled by ending the reaction at different times. Various analytical techniques were applied to characterize the morphology and optical characters of the as-prepared particles. A more than three-fold increase of the fluorescence intensity of GO was obtained.