Interactions Between Polymers and Nanoparticles: Formation of “Supermicellar” Hybrid Aggregates

Abstract

When polyelectrolyte‐neutral block copolymers are mixed in solutions to oppositely charged species (e.g., surfactant micelles, macromolecules, proteins, etc.), there is the formation of stable “supermicellar” aggregates combining both components. The resulting colloidal complexes exhibit a core‐shell structure, and the mechanism yielding to their formation is electrostatic self‐assembly. In this contribution, we report on the structural properties of “supermicellar” aggregates made from yttrium‐based inorganic nanoparticles (radius 2 nm) and polyelectrolyte‐neutral block copolymers in aqueous solutions. The yttrium hydroxyacetate particles were chosen as a model system for inorganic colloids, and also for their use in industrial applications as precursors for ceramic and opto‐electronic materials. The copolymers placed under scrutiny are the water‐soluble and asymmetric poly(sodium acrylate)‐b‐poly(acrylamide) diblocks. Using static and dynamical light‐scattering experiments, we demonstrate the analogy between surfactant micelles and nanoparticles in the complexation phenomenon with oppositely charged polymers. We also determine the sizes and the aggregation numbers of the hybrid organic–inorganic complexes. Several additional properties are discussed, such as the remarkable stability of the hybrid aggregates and the dependence of their sizes on the mixing conditions.     

Preparation and characterization of a polystyrene/bovine serum albumin nanoparticle‐coated capillary for chiral separation using open‐tubular capillary electrochromatography

Polystyrene (PS) nanoparticles coated by BSA, hereafter denoted as PS/BSA, were prepared and chemically immobilized for the first time onto a capillary inner wall for open‐tubular CEC (OTCEC). EOF and scanning electron micrography were used to characterize the prepared nanoparticle‐coated capillaries. To investigate the performance of the prepared columns in OTCEC, chiral separation of d ,l ‐tryptophan (dl ‐Trp) was performed in monolayer BSA‐modified capillary and PS/BSA nanoparticle‐coated columns. The results indicated that the nanoparticle‐modified column afforded a higher resolution compared with the monolayer type. Rapid enantioseparation of dl ‐Trp (within 3 min) was achieved with the PS/BSA‐immobilized column using an electroosmotic pump‐assisted CEC. Enantiomer separations of other compounds like dl ‐tyrosine and warfarin were also achieved with the column. Besides, run‐to‐run and column‐to‐column repeatabilities of the PS/BSA‐coated column in the chiral separation were systematically introduced.     

Human Calcitonin Delivered Orally by Means of Nanoparticles Composed of Novel Graft Copolymers

Abstract

The ability of nanoparticles having surface hydrophilic polymeric chains to enhance the oral absorption of human calcitonin was examined in rats. The oral relative bioavailability of calcitonin against its subcutaneous administration was 0.01% without nanoparticles, but increased significantly when it was administered with nanoparticles. Nanoparticles having cationic poly(vinylamine) (PVAm) chains on their surfaces had a relatively stronger enhancing effect than did other nanoparticles. When divinylbenzene was added to the nanoparticle preparation, PVAm nanoparticles with a crosslinked hydrophobic polystyrene core were synthesized. The addition of divinylbenzene resulted in nanoparticles with larger zeta potential through the efficient accumulation of hydrophilic PVAm chains on their surfaces; however, inadequate amounts decreased the zeta potential. Changes in the bioavailability proportional to the zeta potential indicated that the cationic moiety is indispensable for inducing the significant enhancement of calcitonin absorption. The chemical structure of nanoparticles could be optimized by introducing nonionic poly(N‐isopropylacrylamide) (PNIPAAm) or anionic poly(methacrylic acid) chains onto the PVAm nanoparticle surface to effectively further improve the absorption‐enhancing function of PVAm nanoparticles. Finally, the maximum bioavailability of 1.1% was achieved after oral administration of calcitonin with PVAm–PNIPAAm nanoparticles whose components, VAm macromonomer, N‐isopropylacrylamine (NIPAAm) macromonomer, and styrene were copolymerized in the molar ratio of 1.5:0.5:10.     

Polymer Chain Conformation on Deuterated Polystyrene Nanoparticles Investigated by SANS

We previously reported that grafted polystyrene (PS) chains on silica nanoparticles at a low grafting density show similar conformations to free PS chains in the same solvent, THF (diameter ?50 nm, Colloid.poly.Sci. (2013), 291, 9, 2087–2099). As an extension of our previous study we choose an organic nanoparticle (deuterated polystyrene, dPS) instead of inorganic nanoparticle to see the impact of the substrate material on chain conformation. Additionally, a wider range of molecular weights were prepared to investigate the conformation feature of grafted PS chains more in detail. Small angle neutron scattering (SANS) experiments were performed to characterize PS grafted dPS particles in good solvent condition, with deuterated toluene and deuterated THF as solvent. To get insight into the conformation of the grafted PS layer we apply a scaling law describing the dimension of free PS polymer in good solvent condition to the obtained thickness of the grafted PS layer. We find an overall agreement with the scaling law where the thickness of the grafted PS layer is slightly larger than 2R_g of the free polymer chains in the respective solvent giving hint for semi dilute polymer brush (SDPB) situation.     

铱单原子和纳米粒子在N2O分解反应中的协同催化

原子捕获法是在高温条件下制备高热稳定单原子催化剂的有效方法之一. 但该方法制备的单原子催化剂通常面临着催化活性低、 反应适用范围窄的问题. 因此, 拓展这类单原子催化剂的应用是亟待解决的难点. 本文采用高温捕获法制备的铱(Ir)单原子催化剂在氮氧化物分解反应中的催化活性较低, 但是在继续负载纳米粒子后, 单原子与纳米粒子之间表现出显著的协同催化作用. X射线光电子能谱(XPS)和CO吸附的原位漫反射红外光谱(CO-DRIFTs)表征结合反应动力学分析揭示了反应的活性中心是金属态的Ir纳米粒子. 虽然氧化态的Ir单原子不能直接活化N₂O分子, 但是可以改变Ir纳米粒子的电子结构和吸附性能. 氧气程序升温脱附(O₂-TPD)实验证实, 单原子的存在可以促进O₂从Ir纳米粒子上脱附, 从而提高催化剂的反应活性.     

Synthesis and characterization of CuO nanoparticles utilizing waste fish scale and exploitation of XRD peak profile analysis for approximating the structural parameters

In this research, we strived to utilize waste fish scale (labeo rohita) for synthesizing CuO nano-particles (CuO NPs), which gained much attention due to its distinctive properties and versatile applications. Upon the heat treatment, the collagen content of the fish scale got transformed into gelatin which in turn converted the precursor material into CuO NPs. The X-Ray diffraction (XRD) analysis confirmed the formation of CuO NPs and revealed the structure to be of monoclinic lattice. The structural parameters i.e. crystallite size, lattice parameters, microstrain, dislocation density was evaluated for the synthesized CuO NPs using the XRD data. Scherrer’s Method (SM), Scherrer Equation Average Method (SEAM), Linear Straight Line Method (LSLM), Straight Line Passing the Origin Method (SLPOM), Monshi Scherrer Method (MSM), Williamson-Hall Method (WHM), Size-Strain Plot Method (SSPM), Halder-Wagner Method (HWM) was exploited for the estimation of crystallite size. According to the calculations, the crystallite size was found to be 87 nm, 41 nm, 1980 nm, 62 nm, 66 nm, 28 nm, 13 nm, 13 nm respectively and the dislocation density was found to be 1.32 × 10^-4, 5.95 × 10^-4, 0.002 × 10^-4, 2.60 × 10^-4, 2.29 × 10^-4, 12.75 × 10^-4, 59.17 × 10^-4 and 59.17 × 10^-4 respectively. UV–Vis absorption analysis also confirmed the formation of CuO NPs based on the absorption peak at 262 nm (λ_max) and Tauc Plot method was used to calculate the optical band gap which was 3.84 eV. Functional group, especially the Cu-O bonding was confirmed by the Attenuated Total Reflectance-Fourier Transform Infrared Spectroscopy (ATR-FTIR) data. Field Emission Scanning Electron Microscopy (FESEM) showed three different shapes of CuO NPs which was also confirmed by Transmission Electron Microscopy (TEM). Particle size was determined based on FESEM and TEM image using imageJ software and also by the Dynamic Light Scattering (DLS) technique. Thermal analysis showed a four stage weight loss in case of Thermogravimetric (TGA) analysis and three conversion steps was observed in Differential Scanning Calorimetric (DSC) analysis. Such synthesis pathway is evidently green and facile for synthesizing CuO NPs with potentiality of various applications and also utilization of waste fish scale is a perquisite.     

Differentiating bulk nanobubbles from nanodroplets and nanoparticles

History has shown that it is not as easy as one might think to differentiate between bulk nanobubbles and nanodroplets or nanoparticles. It is generally easy to detect colloids (i.e. something that looks different, e.g. scatters light differently than its surrounding solvent), but less easy to determine the nature of these colloids. This has led to misinterpretations in the literature, where nanodroplets or nanoparticles have mistakenly been assumed to be nanobubbles. In this paper, we review a multitude of experimental methods and approaches to prove the existence of bulk nanobubbles. We conclude that combinations of optical detection with physical perturbations such as pressure or ultrasound, or phase-sensitive holographic methods are the most promising and convenient approaches.     

Advanced Nanomaterials for Multimodal Molecular Imaging

The development of multimodal molecular imaging contrast agents based on versatile nanomaterials has recently attracted much attention in disease diagnosis and therapeutic delivery. Contrast agents made from nanoparticles and used for multimodal imaging in vivo provide a multidimensional pathophysiological overview of diseases. This review summarizes recently developed advanced nanomaterials for multimodal molecular imaging. We comprehensively discuss these nanoparticle contrast agents in terms of their targeting modalities, limitations in clinical translation and future directions.     

纳米氧化锌的过饱和控制生长与大小分布控制.

"在非水介质中合成了纳米氧化锌,测定了纳米氧化锌的紫外吸收光谱,并用有效质量模型计算了粒子大小,开发并命名了一种称之为纳米粒子过饱和控制生长的技术,该技术涉及将小的纳米粒子悬浊液加入到大的粒子悬浊液中,结果因为不同大小粒子间的溶解度差异小的粒子将全部溶解,大的粒子将整体长大,大粒子悬浊液的粒子数将保持不变,大粒子的生长速度显著比Ostwald老化的高．该技术最显著的特征是只要最初两悬浊液粒子大小的差异足够大,分布不是太宽,则粒子大小的分布将会因为粒子如此长大而变窄．"