Colloidal Particles In Solution Research Articles

Structure Formation in Soft-Matter Solutions Induced by Solvent Evaporation.

Solvent evaporation in soft-matter solutions (solutions of colloidal particles, polymers, and their mixtures) is an important process in material making and in the printing and coating industries. The solvent-evaporation process determines the structure of materials and strongly affects their performance. Solvent evaporation involves many physicochemical processes: flow, diffusion, crystallization, gelation, glass transition, etc. and is quite complex. Here, recent progress in this important process is reported, with a special focus on theoretical and simulation studies.

Physical retardation mechanism of latex polymer on the early hydration of cement

The physical retardation effects of styrene/butyl acrylate copolymer latex on the early hydration of cement were investigated, with emphasis of the deformation of polymer particles adsorbed on cement. Five latexes with different glass transition temperatures were prepared by changing the soft monomer (butyl acrylate) content. The diameter of the polymer particles in colloidal solution was studied by dynamic light scattering and the diameter of the polymer particles adsorbed on cement was observed by environmental scanning electron microscopy. It was found that the diameters of polymer particles adsorbed on cement were larger than those in colloidal solution, especially for polymer particles with a high content of soft monomer. The ‘real coverage area’ of polymer particles on cement was theoretically calculated according to the number average diameter of polymer particles adsorbed on cement. It was found that, instead of the adsorption amount of polymer on cement, the real coverage area of polymer on cement is positively correlated with the setting time of latex-modified cement paste. A higher content of soft monomer led to easier deformation of the polymer particles adsorbed on cement, so that the retardation effect of latex on the early hydration of cement increased.

Optical Dispersion, Permittivity Spectrum and Thermal-Lensing Effect in Nickel-Doped Zinc Sulfide Nanoparticles

In this paper, Ni-doped ZnS (ZnS:Ni2+) nanoparticles (NPs) have been prepared through a chemical method. The average size of the particle is 45 nm. Thin films of the particles have been prepared by using the spin-coating method. The linear and nonlinear optical properties of Ni-doped ZnS thin films and the colloidal solution of them have been studied widely. Using a precise numerical method, the refractive index curve (dispersion curve), absorption coefficient and optical permittivity of Ni-doped ZnS film have been obtained. Using these values, the absorption coefficient of the colloidal solution of Ni-doped ZnS particles has been simulated and compared with experimental results. Finally, using the z-scan method at low laser irradiation, the thermo-optical effect has been studied and the nonlinear refractive index due to this effect has been reported.

Investigation of ring polymers in confined geometries

The investigation of a dilute solution of phantom ideal ring polymers and ring polymers with excluded volume interaction (EVI) in a good solvent confined in a slit geometry of two parallel repulsive walls and in a solution of colloidal particles of big size were performed. Taking into account the correspondence between the field theoretical ϕ4 O(n)-vector model in the limit n → 0 and the behavior of long-flexible polymers, the depletion forces and the forces which exert phantom ideal ring and ring polymer with EVI on the walls were obtained in the framework of the massive field theory approach at fixed space dimensions d=3 up to one-loop order. Additionally, the investigation of a dilute solution of phantom ideal ring polymers in the slit geometry of two inert walls and mixed walls with one repulsive and one inert wall were performed. Taking into account the Derjaguin approximation the depletion forces between big colloidal particle and a wall as well as between two big colloidal particles were calculated. The obtained results give possibility to understand the complexity of physical effects arising from confinement and chain topology and can find practical application in new types of micro- and nano-electromechanical devices.

Facile synthesis of cationic polymer functionalized nanodiamond with high dispersity and antibacterial activity

In this work, a cationic polymer, N-alkylated poly (4-vinylpyridine) was applied for the surface functionalization of nanodiamond (ND). The facile route not only settled the problems of agglomeration and poor dispersion stability of ND but also rendered the nanomaterial antibacterial property. Chemical modification of the particles was confirmed by FT-IR spectroscopy and 1HNMR, and the cationic polymer contents were determined by TGA studies. The particle diameters and dispersity of functionalized NDs were investigated by TEM and DLS measurements. It was found that extremely tight core aggregates (100–200 nm) were broken into tiny nanoparticles (20–30 nm) through functionalization with NPVP-propyl or NPVP-hexyl, which gave stable and homogeneous functionalized ND particles in colloidal solution. The antibacterial tests against Gram-positive Staphylococcus aureus (S. aureus) and Gram-negative Escherichia coli (E. coli) showed that the cationic polymer-modified ND exerted certain antibacterial activity. The FE-SEM images indicated that NPVP-hexyl-ND particles were attached to the cell wall surface of E. coli, which subsequently led to the formation of nanoscale holes on cell membrane and eventually the serious destruction of cell wall. We suspected that the interaction of NPVP-hexyl-ND with bacteria may come from the electrostatic interactions, the intermolecular and surface forces between functionalized nanoparticles and cell membranes, which may damage the outer membranes of bacteria and result in cell death.

Reducing spurious flow in simulations of electrokinetic phenomena.

Electrokinetic transport phenomena can strongly influence the behaviour of macromolecules and colloidal particles in solution, with applications in, e.g., DNA translocation through nanopores, electro-osmotic flow in nanocapillaries, and electrophoresis of charged macromolecules. Numerical simulations are an important tool to investigate these electrokinetic phenomena, but are often plagued by spurious fluxes and spurious flows that can easily exceed physical fluxes and flows. Here, we present a method that reduces one of these spurious currents, spurious flow, by several orders of magnitude. We demonstrate the effectiveness and generality of our method for both the electrokinetic lattice-Boltzmann and finite-element-method based algorithms by simulating a charged sphere in an electrolyte solution and flow through a nanopore. We also show that previous attempts to suppress these spurious currents introduce other sources of error.

High electrochemical performance of nanostructured CoOOH grown on nickel foam by hydrothermal deposition for application in supercapacitor

In this work, nanostructured CoOOH grown on nickel foam as an electrode material for application in supercapacitor was prepared by a hydrothermal deposition strategy. The synthetic procedure includes formation of α-Co(OH)2 by epoxide precipitation, transformation of α-Co(OH)2 suspension to CoOOH colloidal solution and deposition of CoOOH particles on nickel foam by hydrothermal treatment. Due to the unique chemistry, the CoOOH particles deposited on nickel foam own extremely small size of about 3 nm. Induced by the small particle size and high conductivity of CoOOH, the as-prepared electrode material presents high electrochemical performance. It is demonstrated that the electrode material is capable of delivering high specific capacitance of 2165.1 F g−1 at scan rate of 5 mV s−1 with excellent cycle stability. It is surprising that this material presents high specific capacitance at very high current density (482.3 A g−1 at 63.9 A g−1). Nanostructured CoOOH was grown on nickel foam as an electrode material for application in supercapacitor through a hydrothermal deposition strategy. Due to the small particle-composed nanostructure and the high conductivity of CoOOH, the as-prepared electrode material presents high electrochemical performance.

Preparation of a Colloid Solution of Au/Silica Core-Shell Nanoparticles Surface-Modified with Cellulose and its X-ray Imaging Properties

Preparation of a Colloid Solution of Au/Silica Core-Shell Nanoparticles Surface-Modified with Cellulose and its X-ray Imaging Properties Objective: The aim of this paper is to describe the preparation of a colloid solution of Au nanoparticles that are coated with silica and simultaneously surface modified with carboxymethylcellulose (CMC) (Au/SiO2/CMC) and to investigate the X-ray imaging of mice using the colloid solution. Methods: The reduction of Au ions (III) with sodium citrate produced Au nanoparticles, and amino groups were introduced on the surface of the Au nanoparticles by using (3-aminopropyl)-trimethoxysilane. The Au nanoparticles with amino groups were silica coated by a sol-gel process using tetraethylorthosilicate, (3-aminopropyl)- triethoxysilane, water and sodium hydroxide in ethanol (Au/SiO2- NH2). After concentrating the as-prepared Au/SiO2-NH2 particle colloid solution by centrifugation, CMC was immobilized on the Au/ SiO2-NH2 particle surface with the addition of CMC to the Au/SiO2- NH2 particle colloid solution. Results: The Au/SiO2/CMC particles, with a size of 67.4 ± 5.4 nm containing a core of a single Au nanoparticle with a size of 17.9 ± 1.3 nm, were produced using the preparation conditions adopted in the present work. A computed tomography (CT) value that was as high as 344 ± 12 Hounsfield units (HU) was recorded for the Au/SiO2/CMC particle colloid solution with an Au concentration of 0.043 M. Its converted value was calculated by dividing the Au concentration into the recorded CT value and was 8.0×103 HU/M. This value was larger than that of Iopamiron 300, a commercial X-ray contrast agent. The Au/SiO2/CMC particle colloid solution was injected into the tail vein of a mouse and could be used to image the tissues. Conclusion: The Au/SiO2/CMC particle colloid solution obtained in the present work was successfully used for X-ray imaging.

Colloids in the study of fundamental physics

Colloidal particles in solution exhibit rich phase behaviors and behavior like big-atom. In the past decades, as modelling systems, colloids have been widely employed in the study of nucleation, crystallization, glass transition and melting. A number of advances have been achieved. These advances to a large extent extend and complete the understanding of various phase transitions. Recently, a number of active fields are emerging with colloidal model systems. In this review, the advances and the emerging fields are summarized. At the end, the potential directions and the challenges for future studies are suggested.

Rapid calculation of hydrodynamic and transport properties in concentrated solutions of colloidal particles and macromolecules

A new method for calculating the resistance tensors of arbitrarily shaped particles and the translational and rotational self-diffusivity in suspensions of such particles is developed. This approach can be harnessed to efficiently and accurately predict the hydrodynamic and transport properties of large macromolecules such as antibodies in solution. Particles are modeled as a rigid composite of spherical beads, and the continuum equations for low Reynolds number fluid mechanics are used to calculate the drag on the composite or its diffusivity in a solution of other composites. The hydrodynamic calculations are driven by a graphics processing unit (GPU) implementation of the particle-mesh-Ewald technique which offers log-linear scaling with respect to the complexity of the composite-bead particles modeled as well as high speed execution leveraging the hyper-parallelization of the GPU. Matrix-free expressions for the hydrodynamic resistance and translational and rotational diffusivity of composite bead particles are developed, which exhibit substantial improvements in computational complexity over existing approaches. The effectiveness of these methods is demonstrated through a series of calculations for composite-bead particles having a spherical geometry, and the results are compared to exact solutions for spheres. Included in the supplementary material is an implementation of the proposed algorithm which functions as a plug-in for the GPU molecular dynamics suite HOOMD-blue (http://codeblue.umich.edu/hoomd-blue) [J. A. Anderson, C. D. Lorenz, and A. Travesset, “General purpose molecular dynamics simulations fully implemented on graphics processing units,” J. Comput. Phys. 227(10), 5342–5359 (2008) and Glaser et al., “Strong scaling of general-purpose molecular dynamics simulations on GPUs,” Comput. Phys. Commun. 192, 97–107 (2015)].

Fabrication of quantum dot/silica core–shell particles immobilizing Au nanoparticles and their dual imaging functions

The present work proposes preparation methods for quantum dot/silica (QD/SiO2) core–shell particles that immobilize Au nanoparticles (QD/SiO2/Au). A colloid solution of QD/SiO2 core–shell particles with an average size of 47.0 ± 6.1 nm was prepared by a sol–gel reaction of tetraethyl orthosilicate in the presence of the QDs with an average size of 10.3 ± 2.1 nm. A colloid solution of Au nanoparticles with an average size of 17.9 ± 1.3 nm was prepared by reducing Au3+ ions with sodium citrate in water at 80 °C. Introduction of amino groups to QD/SiO2 particle surfaces was performed using (3-aminopropyl)-triethoxysilane (QD/SiO2-NH2). The QD/SiO2/Au particles were fabricated by mixing the Au particle colloid solution and the QD/SiO2-NH2 particle colloid solution. Values of radiant efficiency and computed tomography for the QD/SiO2/Au particle colloid solution were 2.23 × 107 (p/s/cm2/sr)/(μW/cm2) at a QD concentration of 8 × 10−7 M and 1180 ± 314 Hounsfield units and an Au concentration of 5.4 × 10−2 M. The QD/SiO2/Au particle colloid solution was injected into a mouse chest wall. Fluorescence emitted from the colloid solution could be detected on the skin covering the chest wall. The colloid solution could also be X-ray-imaged in the chest wall. Consequently, the QD/SiO2/Au particle colloid solution was found to have dual functions, i.e., fluorescence emission and X-ray absorption in vivo, which makes the colloid solution suitable to function as a contrast agent for dual imaging processes.

Preparation of Au/silica/poly(ethylene glycol) nanoparticle colloid solution and its use in x-ray imaging process

In this work, the authors performed X-ray imaging of mice using a colloid solution of Au nanoparticles that are coated with silica and subsequently surface-modified with poly(ethylene glycol) (PEG) (Au/SiO2/PEG). The silica-coating for Au nanoparticles and the amination for silica-coated particles were simultaneously performed in the presence of the Au nanoparticles, which were prepared by reducing Au ions (III) with sodium citrate in water at 80°C and by surface-modifying the Au nanoparticles with (3-aminopropyl)-trimethoxysilane (APMS), by a sol–gel process using tetraethylorthosilicate (TEOS), (3-aminopropyl)-triethoxysilane, water and sodium hydroxide (Au/SiO2-NH2). The surface modification of Au/SiO2-NH2 particles with PEG was performed by simply adding PEG with a functional group that reacts with an amino group to the Au/SiO2-NH2 particle colloid solution. A computed tomography value of the Au/SiO2/PEG colloid solution with an Au concentration of 0.129M was as high as 895 ± 8 HU. Mouse tissues were imaged following injection of the Au/SiO2/PEG particle colloid solution.

Effect of silver nanoparticles on fluorescence and nonlinear properties of naturally occurring betacyanin dye

We present the linear and nonlinear optical studies of a natural dye betacyanin extracted from red beet root in the presence of silver nano particles in colloidal solution. We synthesized silver nano particles and characterized by XRD and HRTEM. We show how appropriate concentration of silver nanoparticles can enable tuning of dye fluorescence efficiency. Nonlinear properties are studied using open aperture Z scan technique with Nd:YAG laser (532nm, 7ns, 10Hz). We show modification of nonlinear properties for the dye to the desired level can be achieved in the presence of silver nanoparticles. High nonlinearity we also demonstrated in PVA/Ag nano/Betacyanin composite films. Theoretical analysis is performed using model based on nonlinear absorption of materials and scattering of metal nanoparticles.

Synthesis of a colloid solution of silica-coated gold nanoparticles for X-ray imaging applications

This work proposes a method for fabricating silica-coated gold (Au) nanoparticles, surface modified with poly(ethylene glycol) (PEG) (Au/SiO2/PEG), with a particle size of 54.8 nm. X-ray imaging of a mouse is performed with the colloid solution. A colloid solution of 17.9 nm Au nanoparticles was prepared by reducing Au ions (III) with sodium citrate in water at 80 °C. The method used for silica-coating the Au nanoparticles was composed of surface-modification of the Au nanoparticles with (3-aminopropyl)-trimethoxysilane (APMS) and a sol–gel process. The sol–gel process was performed in the presence of the surface-modified Au nanoparticles using tetraethylorthosilicate, APMS, water, and sodium hydroxide, in which the formation of silica shells and the introduction of amino groups to the silica-coated particles took place simultaneously (Au/SiO2–NH2). Surface modification of the Au/SiO2–NH2 particles with PEG, or PEGylation of the particle surface, was performed by adding PEG with a functional group that reacted with an amino group in the Au/SiO2–NH2 particle colloid solution. A computed tomography (CT) value of the aqueous colloid solution of Au/SiO2/PEG particles with an actual Au concentration of 0.112 M was as high as 922 ± 12 Hounsfield units, which was higher than that of a commercial X-ray contrast agent with the same iodine concentration. Injecting the aqueous colloid solution of Au/SiO2/PEG particles into a mouse increased the light contrast of tissues. A CT value of the heart rose immediately after the injection, and this rise was confirmed for up to 6 h.

Tuning porous silica nanofibers by colloid electrospinning for dye adsorption

Porous silica nanofibers were prepared by electrospinning alkoxide precursors and sacrificial polystyrene nanoparticles (PSNs). The multi-compartmented fibers were electrospun from a mixed solution of colloidal particles and poly (vinyl pyrrolidone), added with tetraethyl orthosilicate and acetic acid. The colloidal particles were embedded into the resultant fibers with a close-packing structure. After air calcination, the removal of polymeric particles created porous silica nanofibers. The pore size of the silica nanofibers ranges from micropores (∼3 nm) to mesopores (∼50 nm), and can be precisely controlled by changing the weight ratio of the PSNs. Such hierarchical porous nanofibers have been demonstrated as a promising candidate for dye adsorption. The dye absorption ability was enhanced as more mesopores were created, although the specific surface area simultaneously decreased with the decrease of micropores.

Imaging Processes Using Core-Shell Particle Colloid Solutions for Medical Diagnosis

This paper describes our studies on development of methods for preparing colloid solutions of core-shell particles composed of core of materials with imaging ability and shell of silica that is inert to living bodies, and on their imaging properties. The methods for silica-coating are based on hydrolysis and condensation of silicone alkoxide in the presence of particles. AgI nanoparticles fabricated by mixing AgClO4 aqueous solution with KI aqueous solution were silica-coated with an aid of silane coupling agent. The silica-coated AgI particle colloid solution revealed X-ray imaging ability. Au nanoparticles, which were produced with reduction of HAuCl4 using citrate as reducing reagent and then surface-modified with silane coupling agent, were coated with silica. Images of the colloid solution were successfully taken through X-ray irradiation. For Gd compound, silica nanoparticles fabricated by a Stober method were coated with Gd compound shell by a homogeneous precipitation method, and then coated with silica shell. The colloid solution was successfully imaged through magnetic resonance. Commerciallyavailable Cd-related semiconductor nanoparticles were surfacemodified with silane coupling agent, and then coated with silica. Tissues of mouse were imaged by injecting their colloid solution and using an in vivo fluorescence imaging system (IVIS).

Preparation of silica-coated gadolinium compound particle colloid solution and its application in imaging

A preparation method for gadolinium compound (GdC) nanoparticles coated with silica (GdC/SiO2) is proposed. GdC nanoparticles were prepared with a homogeneous precipitation method at 80oC using 1.0x10-3 M Gd(NO3)3, 0.5 M urea and 0-3.0x10-4 M ethylenediaminetetraaceticacid disodium salt dihydrate (ETDA) in water. As a result of preparation at various EDTA concentrations, GdC nanoparticles with a size as small as 40.5+-6.2 nm, which were colloidally stable, were prepared at an EDTA concentration of 2.0x10-4 M. Silica-coating of the GdC nanoparticles was performed by a Stober method at 35oC using 1.0-10.0x10-3 M tetraethylorthosilicate (TEOS), 11 M H2O and 1.5x10-3 M NaOH in ethanol in the presence of 1.0x10-3 M GdC nanoparticles. Performance of preparation at various TEOS concentrations resulted in production of GdC/SiO2 particles with an average size of 106.1+-11.2 nm at a TEOS concentration of 5.0x10-3 M. The gadolinium (Gd) concentration of 1.0x10-3M in the as-prepared GdC/SiO2 particle colloid solution was increased up to a Gd concentration of 0.2 M by concentrating with centrifugation. The core-shell structure of GdC/SiO2 particles was undamaged, and the colloid solution was still colloidally stable, even after the concentrating process. The concentrated GdC/SiO2 colloid solution showed images of X-ray and magnetic resonance with contrast as high as commercial Gd complex contrast agents.

X-ray imaging technique using colloid solution of Au/silica core-shell nanoparticles

This work describes X-ray imaging of mouse using a colloid solution of silica-coated Au (Au/SiO2) nanoparticles. A colloid solution of Au nanoparticles with a size of 16.9 nm was prepared using hydrogen tetrachloroaurate (III) trihydrate as Au source and sodium citrate as reducing reagent. Silica coating of the Au nanoparticles was performed by modifying the Au nanoparticle surface with (3-aminopropyl)trimethoxysilane and then by depositing silica nuclei generated through a sol–gel reaction of tetraethyl orthosilicate in water/ethanol initiated with sodium hydroxide on the surface-modified surface, which produced Au/SiO2 particles with a size of 136.4 nm. A computed tomography value of the Au/SiO2 colloid solution with an Au concentration of 0.036 M was as high as 1,184.8 Hounsfield units, which was quite higher than that of a commercial X-ray contrast agent with the same iodine concentration as the Au concentration. Tissues of mouse could be imaged by injecting the Au/SiO2 particle colloid solution into them.

The Action of Ligands in the Aggregation Process of Soft Colloidal Solution Monitored by Raman Spectroscopy

The formation of soft colloidal particles in solution and their aggregation process has been studied by Raman spectroscopy. The soft colloidal particles makes up at room temperature by the Sodium Dodecyl Sulfate (SDS) solution over the critical micellar concentration, while the micellar clustering is obtained adding in solution two different ligands: the Kryptofix 2.2.2 (K222) and crown ether 18-Crown-6 (18C6). The chosen ligands molecules are able to interact with the micellar interface inducing the cluster phase formation. Vibrational peaks fingerprints of the micelles formation have been observed and the evidences of the cluster-phase formation have been also achieved in the case of micelles solution doped with the two different macro-cyclic ligands. The ligands action is however different in the two cases as evinced by the careful analysis of the intensity and wavenumber evolution of characteristic Raman peaks at different ligants concentration values. The cluster phase formation and the effects induced on the hydration layer are analyzed showing how Raman spectroscopy is able to gain insight into self-assembly of soft colloidal particles.

Fabrication of hollow particles composed of silica containing gadolinium compound and magnetic resonance imaging using them

A preparation method for hollow particles composed of silica shell containing gadolinium compound (GdC) is proposed. GdC nanoparticles with an average size of 40.5 ± 6.2 nm were prepared with a homogeneous precipitation method at 80°C using 1.0 × 10−3 M Gd(NO3)3 and 0.5 M urea in the presence of 2.0 × 10−4 M ethylenediaminetetraacetic acid disodium salt dihydrate. Silica-coated GdC (GdC/SiO2) nanoparticles with an average size of 100.9 ± 9.9 nm were fabricated with a sol-gel method at 35°C using 5.0 × 10−3 M tetraethylorthosilicate, 11 M H2O, and 1.5 × 10−3 M NaOH in ethanol in the presence of 1.0 × 10−3 M GdC nanoparticles. The GdC/SiO2 particles were aged at 80°C in water after replacement of solvent of the as-prepared GdC/SiO2 particle colloid solution with water, which provided diffusion of GdC into the silica shell and then formation of a hollow structure. The hollow particle colloid solution revealed good MRI properties. A relaxivity value for longitudinal relaxation time-weighted imaging was as high as 3.38 mM−1 · s−1 that attained 80% of that for a commercial Gd complex contrast agent.