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Rui Zhang, Kenneth S Schweizer
The Elastically Collective Nonlinear Langevin Equation theory for one-component viscous liquids and suspensions is generalized to treat coupled slow activated relaxation and diffusion in glass-forming binary sphere mixtures of any composition, size ratio and inter-particle interactions. A trajectory-level dynamical coupling parameter concept is introduced to construct two coupled dynamic free energy functions for the smaller penetrant and larger matrix particle. A two-step dynamical picture is proposed where the first step process involves matrix-facilitated penetrant hopping quantified in a self-consistent manner based on a temporal coincidence condition...
January 18, 2018: Journal of Physical Chemistry. B
Qinghua Zhao, Tianshuo Zhao, Jiacen Guo, Wenxiang Chen, Mingliang Zhang, Cherie R Kagan
Doping, as a central strategy to control free carrier type and concentration in semiconductor materials, suffers from low efficiency at the nanoscale, especially in systems having high permittivity (ϵ) and large Bohr radii, such as lead chalcogenide nanocrystals (NCs) and nanowires (NWs). Here, we study dielectric confinement effects on the doping efficiency of lead chalcogenides nanostructures by integrating PbSe NWs in the platform of field effect transistors (FETs). Elemental Pb or In or elemental Se is deposited by thermal evaporation to remotely n- or p-dope the NWs...
January 18, 2018: ACS Nano
Sabrina Simoncelli, Yi Li, Emiliano Cortes, Stefan A Maier
Self-assembly processes allow designing and creating complex nanostructures using molecules as building blocks and surfaces as scaffolds. This autonomous driven construction is possible due to a complex thermodynamic balance of molecule-surface interactions. As such, nanoscale guidance and control over this process is hard to achieve. Here we use the highly localized light-to-chemical-energy conversion of plasmonic materials to spatially cleave Au-S bonds on pre-determined locations within a single nanoparticle, enabling a high degree of control over this archetypal system for molecular self-assembly...
January 18, 2018: ACS Nano
Xiangkai Liu, Shuangyi Zhao, Wei Gu, Yuting Zhang, Xvsheng Qiao, Zhenyi Ni, Xiaodong Pi, Deren Yang
Colloidal silicon quantum dots (Si QDs) hold ever-growing promise for the development of novel optoelectronic devices such as light-emitting diodes (LEDs). Although it has been proposed that ligands at the surface of colloidal Si QDs may significantly impact the performance of LEDs based on colloidal Si QDs, little systematic work has been carried out to compare the performance of LEDs that are fabricated by using colloidal Si QDs with different ligands. Here colloidal Si QDs with rather short octyl ligands (Octyl-Si QDs) and phenylpropyl ligands (PhPr-Si QDs) are employed for the fabrication of LEDs...
January 18, 2018: ACS Applied Materials & Interfaces
Anže Lošdorfer Božič
The importance of electrostatic interactions in soft matter and biological systems can often be traced to non-uniform charge effects, which are commonly described using a multipole expansion of the corresponding charge distribution. The standard approach when extracting the charge distribution of a given system is to treat the constituent charges as points. This can, however, lead to an overestimation of multipole moments of high order, such as dipole, quadrupole, and higher moments. Focusing on distributions of charges located on a spherical surface - characteristic of numerous biological macromolecules, such as globular proteins and viral capsids, as well as of inverse patchy colloids - we develop a novel way of representing spherical surface charge distributions based on the von Mises-Fisher distribution...
January 18, 2018: Soft Matter
Deqiang Yin, Yang Liu, Chaochao Dun, David L Carroll, Mark T Swihart
Tin chalcogenides have shown promise in applications including energy storage, optoelectronics, photovoltaics, and thermoelectrics. Here, we present a colloidal synthesis strategy to produce tin dichalcogenide nanocrystals (NCs) with controllable stoichiometry, vacancies, shape, and crystal structure. Compared with previously reported methods, we use less expensive precursors, such as tin(iv) chloride and sulfur or selenium powder, to produce tin(iv) chalcogenide NCs. SnS2 and SnSe2 NCs with novel NC morphologies including SnS2 nanoflowers/nanoflakes, SnSe2 nanosheets with circular and hexagonal shapes, as well as mixtures of nanospheres and nanoflakes were prepared by varying the solvents and anion precursors...
January 18, 2018: Nanoscale
Lígia Nunes de Morais Ribeiro, Verônica Muniz Couto, Leonardo Fernandes Fraceto, Eneida de Paula
Elucidation of the structural properties of colloids is paramount for a successful formulation. However, the intrinsic dynamism of colloidal systems makes their characterization a difficult task and, in particular, there is a lack of physicochemical techniques that can be correlated to their biological performance. Nanoparticle tracking analysis (NTA) allows measurements of size distribution and nanoparticle concentration in real time. Its analysis over time also enables the early detection of physical instability in the systems not assessed by subtle changes in size distribution...
January 17, 2018: Scientific Reports
Marion Dubald, Sandrine Bourgeois, Véronique Andrieu, Hatem Fessi
The last fifty years, ophthalmic drug delivery research has made much progress, challenging scientists about the advantages and limitations of this drug delivery approach. Topical eye drops are the most commonly used formulation in ocular drug delivery. Despite the good tolerance for patients, this topical administration is only focus on the anterior ocular diseases and had a high precorneal loss of drugs due to the tears production and ocular barriers. Antibiotics are popularly used in solution or in ointment for the ophthalmic route...
January 13, 2018: Pharmaceutics
Wei-Yuan Wang, Xiu-Fen Zhao, Xiao-Han Ju, Ping Liu, Jing Li, Ya-Wen Tang, Shu-Ping Li, Xiao-Dong Li, Fu-Gui Song
Au-methotrexate (Au-MTX) conjugates induced by sugar molecules were produced by a simple, one-pot, hydrothermal growth method. Herein, the Au(III)-MTX complexes were used as the precursors to form Au-MTX conjugates. Addition of different types of sugar molecules with abundant hydroxyl groups resulted in the formation of Au-MTX conjugates featuring distinct characteristics that could be explained by the diverse capping mechanisms of sugar molecules. That is, the instant-capping mechanism of glucose favored the generation of peanut-like Au-MTX conjugates with high colloidal stability while the post-capping mechanism of dextran and sucrose resulted in the production of Au-MTX conjugates featuring excellent near-infrared (NIR) optical properties with a long-wavelength plasmon resonance near 630-760 nm...
January 13, 2018: International Journal of Pharmaceutics
D Heckendorf, K J Mutch, S U Egelhaaf, M Laurati
We have investigated concentrated suspensions of polydisperse hard spheres and have determined the dynamics and sizes of individual particles using confocal microscopy. With increasing concentration, the dynamics of the small and large particles start to differ. The large particles exhibit slower dynamics and stronger localization. Moreover, as the particle size increases, the local volume fraction ϕ_{loc} also increases. In the glass state, the localization length significantly decreases beyond ϕ_{loc}≈0...
July 28, 2017: Physical Review Letters
Neil Y C Lin, Matthew Bierbaum, Itai Cohen
By combining confocal microscopy and stress assessment from local structural anisotropy, we directly measure stresses in 3D quiescent colloidal liquids. Our noninvasive and nonperturbative method allows us to measure forces ≲50  fN with a small and tunable probing volume, enabling us to resolve the stress fluctuations arising from particle thermal motions. We use the Green-Kubo relation to relate these measured stress fluctuations to the bulk Brownian viscosity at different volume fractions, comparing against simulations and conventional rheometry measurements...
September 29, 2017: Physical Review Letters
M Chaudhuri, E Allahyarov, H Löwen, S U Egelhaaf, D A Weitz
At the triple point of a repulsive screened Coulomb system, a fcc crystal, a bcc crystal, and a fluid phase coexist. At their intersection, these three phases form a liquid groove, the triple junction. Using confocal microscopy, we resolve the triple junction on a single-particle level in a model system of charged PMMA colloids in a nonpolar solvent. The groove is found to be extremely deep and the incommensurate solid-solid interface to be very broad. Thermal fluctuations hence appear to dominate the solid-solid interface...
September 22, 2017: Physical Review Letters
Sheryhan F Gad, Joonyoung Park, Ji Eun Park, Gihan N Fetih, Sozan S Tous, Wooin Lee, Yoon Yeo
Intravenous delivery of poorly water-soluble anticancer drugs such as docetaxel (DTX) is challenging due to the low bioavailability and the toxicity related to solubilizing excipients. Colloidal nanoparticles are used as alternative carriers, but low drug loading capacity and circulation instability limit their clinical translation. To address these challenges, DTX nanocrystals (NCs) were prepared using Pluronic F127 as an intermediate stabilizer and albumin as a functional surface modifier, which were previously found to be effective in producing small and stable NCs...
January 17, 2018: Molecular Pharmaceutics
Daniel Schneditz, Georgios Sarikakis, Maria Kontodima, Notburga Sauseng
The aim of this study was to examine the relationship between hydrostatic trans-membrane pressure (TMPh ) and colloid osmotic pressure (COP) in low-flux (LF) and high-flux (HF) dialyzers. Hydrostatic pressures were measured in dialyzers distinguished by their ultrafiltration coefficient Kuf (16 and 85 mL/h/mm Hg) under constant dialysate flow and variable blood flow (Qb ) ranging from 0 to 400 mL/min using (i) alginate (70 kDa) dissolved in dialysate, (ii) diluted, undiluted, and concentrated plasma, or (iii) whole blood at different hematocrit, all in absence of ultrafiltration (UF)...
January 17, 2018: Artificial Organs
Min-Da Yu, Xiao-Song He, Bei-Dou Xi, Ru-Tai Gao, Xian-Wei Zhao, Hui Zhang, Cai-Hong Huang, Wenbing Tan
Fluorescence excitation-emission matrix (EEM) spectroscopy combined with principal component analysis (PCA) and parallel factor analysis (PARAFAC) were used to investigate the compositional characteristics of dissolved and particulate/colloidal organic matter and its correlations with nitrogen, phosphorus, and heavy metals in an effluent-dominated stream, Northern China. The results showed that dissolved organic matter (DOM) was comprised of fulvic-like, humic-like, and protein-like components in the water samples, and fulvic-like substances were the main fraction of DOM among them...
January 17, 2018: Environmental Science and Pollution Research International
Jérôme Burelbach, Daan Frenkel, Ignacio Pagonabarraga, Erika Eiser
We use the dynamic length and time scale separation in suspensions to formulate a general description of colloidal thermophoresis. Our approach allows an unambiguous definition of separate contributions to the colloidal flux and clarifies the physical mechanisms behind non-equilibrium motion of colloids. In particular, we derive an expression for the interfacial force density that drives single-particle thermophoresis in non-ideal fluids. The issuing relations for the transport coefficients explicitly show that interfacial thermophoresis has a hydrodynamic character that cannot be explained by a purely thermodynamic consideration...
January 16, 2018: European Physical Journal. E, Soft Matter
Irma Liascukiene, Gabriel Amselem, Deniz Z Gunes, Charles N Baroud
Foams can be stabilized for long periods by the adsorption of solid particles on the liquid-gas interfaces. Although such long-term observations are common, mechanistic descriptions of the particle adsorption process are scarce, especially in confined flows, in part due to the difficulty of observing the particles in the complex gas-liquid dispersion of a foam. Here, we characterise the adsorption of micron-scale particles onto the interface of a bubble flowing in a colloidal aqueous suspension within a microfluidic channel...
January 17, 2018: Soft Matter
Hongyu Guo, Gheorghe Stan, Yun Liu
Nanoparticles typically have an inherent wide size distribution that may affect the performance and reliability of many nanomaterials. Because the synthesis and purification of nanoparticles with desirable sizes are crucial to the applications of nanoparticles in various fields including medicine, biology, health care, and energy, there is a great need to search for more efficient and generic methods for size-selective nanoparticle purification/separation. Here we propose and conclusively demonstrate the effectiveness of a size-selective particle purification/separation method based on the critical Casimir force...
January 17, 2018: Soft Matter
Amane Kobayashi, Yuki Sekiguchi, Tomotaka Oroguchi, Masaki Yamamoto, Masayoshi Nakasako
X-ray free electron lasers (XFEL) provide intense and almost coherent X-ray pulses. They are used for various experiments investigating physical and chemical properties in materials and biological science because of their complete coherence, high intensity, and very short pulse width. In XFEL experiments, specimens are irradiated by XFEL pulses focused by mirror optics. The focused pulse is too intense to measure its coherence by placing an X-ray detector on the focal spot. Previously, a method was proposed for evaluating the coherence of focused pulses from the visibility of the diffraction intensity of colloidal particles by the speckle visibility spectroscopy (SVS)...
January 16, 2018: Scientific Reports
Ian Williams, Francesco Turci, James E Hallett, Peter Crowther, Chiara Cammarota, Giulio Biroli, C Patrick Royall
A quasi two-dimensional colloidal suspension is studied under the influence of immobilisation (pinning) of a random fraction of its particles. We introduce a novel experimental method to perform random pinning and, with the support of numerical simulation, we find that increasing the pinning concentration smoothly arrests the system, with a cross-over from a regime of high mobility and high entropy to a regime of low mobility and low entropy. At the local level, we study fluctuations in area fraction and concentration of pins and map them to entropic structural signatures and local mobility, obtaining a measure for the local entropic fluctuations of the experimental system...
January 17, 2018: Journal of Physics. Condensed Matter: An Institute of Physics Journal
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