Hybrid Colloidal Particles Research Articles

Photo‐ and pH‐Responsive Hybrid Colloidal Particles

AbstractMaterials that respond to environmental changes in a predictable manner are called “smart”. Here, smart dual‐responsive hybrid colloidal particles were prepared using the interface‐mediated reversible addition–fragmentation chain‐transfer (RAFT) polymerization method. The structure and morphology of the prepared poly(methacrylated‐spiropyran) (p(MMASP)) colloids were characterized by FTIR, 1H‐NMR and GPC spectroscopies, and SEM. The molecular weight and polydispersity were determined as 7877 g mol−1 and 1.16, respectively. Heterocyclic ring cleavage of the spiropyran (SP) pendant group enables the pH‐ and light‐responsive behavior with a reversible conversion between the hydrophobic and hydrophilic states. The isomerization from SP to merocyanine (MC) form proceeds in 7 min, while the reverse action takes 9 min. The pronounced photochromic effect and high fatigue resistance make these colloids suitable for smart applications.

3D printing of non-iridescent structural color inks for optical anti-counterfeiting.

In this work, structural color inks with practical significance in anti-counterfeiting applications have been successfully manufactured by facilely mixing SiO2@PDA@PHEMA hybrid colloidal particles with the mediated molecules of HEMA. The appropriate rheological properties of these photonic inks provide high viscosity and self-supporting performance, ensuring sufficient interaction between particles to form short-range ordered arrays during the mixing and shearing process and thus generating non-iridescent colors. The strong and broad uniform light absorption capabilities of polydopamine (PDA) not only suppress the incoherent multiple scattering of the photonic inks, but also impart surprising optical anti-counterfeiting properties, i.e. black color under ambient illumination and dazzling reflective coloration under strong illumination. With the 3D printing technique, complicated angle-independent patterns with visualization and high fidelity are expected to be fabricated with the as-prepared photonic inks for real-life applications in smart anti-counterfeiting labels, thus encoding encrypted information and selective color rendering accessories.

Encapsulation of doxorubicin in magnetic‐polymer hybrid colloidal particles of Eudragit E100 and their hyperthermia and drug release studies

Water‐soluble magnetite Fe3O4 nanoparticles were synthesized by coprecipitation that exhibit spherical morphology and superparamagnetic behavior with a saturation magnetization of 46 emu/g. These nanoparticles were coated with amino methacrylate copolymer (Eudragit E100) along with encapsulation of Doxorubicin drug under the action of sonication via a double emulsion solvent evaporation method. The prepared magnetic colloids were evaluated for particle size, surface morphology, surface charge, drug loading capacity, and entrapment efficiency. The drug release studies indicated the sustained release of drug of 92% in 24 hours at physiological pH of 7.4 and drug release kinetics followed first order. The prepared nanoparticles and their colloids were also investigated for magnetic hyperthermia and specific absorption rate values were found to be 2.41, 2.71, and 4.28 W/g at 259, 327, and 518 kHz, respectively. The developed magnetic colloids have the potential to perform controlled hyperthermia and drug release to the target sites.

Elucidation of Titanium Dioxide Nucleation and Growth on a Polydopamine-Modified Nanoporous Polyvinylidene Fluoride Substrate via Low-Temperature Atomic Layer Deposition.

Interfaces combining polydopamine (PDA) and nanoparticles have been widely utilized for fabricating hybrid colloidal particles, thin films, and membranes for applications spanning biosensing, drug delivery, heavy metal detection, antifouling membranes, and lithium ion batteries. However, fundamental understanding of the interaction between PDA and nanoparticles is still limited, especially the impact of PDA on nanoparticle nucleation and growth. In this work, PDA is used to generate functional bonding sites for depositing titanium dioxide (TiO2) via atomic layer deposition (ALD) onto a nanoporous polymer substrate for a range of ALD cycles (<100). The resulting hybrid membranes are systematically characterized using water contact angle, scanning electron microscopy, atomic force microscopy, nitrogen adsorption and desorption, and X-ray photoelectron spectroscopy (XPS). An intriguing nonlinear relationship was observed between the number of ALD cycles and changes in surface properties (water contact angle and surface roughness). Together with XPS study, those changes in surface properties were exploited to probe the nanoparticle nucleation and growth process on complex PDA-coated porous polymer substrates. Molecular level understanding of inorganic and polymer material interfaces will shed light on fine-tuning nanoparticle-modified polymeric membrane materials.

Synthesis of raspberry-like polymer@silica hybrid colloidal particles through biphasic sol-gel process

We report a simple process for the synthesis of raspberry-like hybrid colloidal particles through biphasic sol-gel process. Poly(ethylene oxide)- (PEO-) functionalized latexes with different morphologies (sphere, vesicle and fiber) were prepared through nitroxide mediated surfactant-free emulsion polymerization. In the biphasic sol-gel process, polymer latexes were first dispersed in aqueous solution of L-arginine, a basic amino acid used as catalyst. As the silica source, tetraethyl orthosilicate (TEOS) was carefully added on top of the reactor to get a two-phase solution. TEOS is slowly delivered in the aqueous solution to form silica particles which can adsorbed on the latex surface due to the hydrogen bonding between PEO and Si−OH. The size of silica shell particles can be easily controlled by tuning the TEOS content. The effect of latex sizes, content and morphologies on the morphologies of hybrid particles were investigated in this work. Both raspberry-like spheres, vesicles and fibers were fabricated with different latex templates.

Structural Control of Hybrid Colloidal Particle Surface by Plasma-etching Treatment

A reactive-ion etching system was used to control the surface of gold–polystyrene hybrid colloidal particles with an eccentric structure, and a function of the etched particles was demonstrated as ...

Controllable Synthesis and Surface Wettability of Flower-Shaped Silver Nanocube-Organosilica Hybrid Colloidal Nanoparticles.

Synthesis of hybrid colloidal particles with complex and hierarchical structures is attracting much interest theoretically and technically in recent years, but still remains a tremendous challenge. Here, we present a mild and controllable wet-chemical method for the synthesis of silver nanocube (Ag NC)-organosilica hybrid particles with finely tuned numbers (with one, two, three, four, five, or six) and sizes of organosilica petals, by simply controlling the affinity with Ag NC/nature, amount, and prehydrolysis process of alkoxysilanes. The morphologies of hybrid colloidal particles have an obvious influence on the surface wettability of the hybrid particle-based films. More and larger organosilica petals can increase the surface hydrophobicity of the hybrid particle-based films.

TGA and magnetization measurements for determination of composition and polymer conversion of magnetic hybrid particles

Magnetic hybrid colloidal particles can be characterized using various techniques and numerous tools leading generally to particles size, size distribution, and electrokinetic properties. However, the chemical composition of these hybrid particles can be estimated using thermal gravimetric analysis (TGA). More interestingly, the combination of this quantitative technique with the magnetization measurement leads not only to chemical composition but also to the overall polymerization conversion and more precisely to the polymerization conversion on the seed particles. In fact, the TGA performed on dried magnetic particles leads to exact organic/inorganic chemical composition. Regarding the magnetization, the amount of magnetic material can be deduced, and consequently, the amount of non‐magnetic material can be also estimated. Thus, TGA and magnetization measurements are considered as complementary techniques for characterization of magnetic hybrid colloidal particles. Copyright © 2015 John Wiley &amp; Sons, Ltd.

Hybrid Au–SiO2Core–Satellite Colloids as Switchable SERS Tags

Gold–silica self-assembled nanostructures are reported as multiplex surface enhanced Raman scattering (SERS) tags for bioimaging applications. These hybrid colloidal particles were obtained by heteroassembly of Au–SiO2 Janus particles with smaller Au spheres and two Raman-active molecules that can be independently imaged by varying the wavelength of the excitation laser. The Janus structure of Au–SiO2 not only directs the assembly but also provides physical separation of the Raman tags and colloidal stability thereby facilitating complete silica encapsulation. The bioimaging capabilities of this system are demonstrated through SERS mapping of individual cells.

Polyelectrolyte complex-silica hybrid colloidal particles decorated with different polyelectrolytes

We report the synthesis of polyelectrolyte-decorated hybrid colloidal particles by using negatively charged polyelectrolyte complex (PEC) micelles as colloidal templates for silica mineralization under ambient conditions. The negatively charged polyelectrolytes including poly(acrylic acid) (PAA), poly(L-glutamic acid) (PLGA), and poly(styrene sulfonate) (PSS) were complexed with poly(L-lysine) at non-stoichiometric mixing weight percentage to form negatively charged PEC micelles. Varying the mixing weight percentage and molecular weight of polyelectrolytes led to the changes in the size and charge of the PEC particles. Silica mineralization in the complex core resulted in the colloidally stable hybrid particles decorated with different negatively charged polyelectrolytes. The colloidal properties of these polyelectrolyte-decorated hybrid particles were determined by the composition and decorated polyelectrolyte. This approach provided a simple and facile method to prepare polymer-decorated hybrid colloidal particles comprised of different polymers and their colloidal properties can be easily tuned by varying the decorated polymer and synthesis condition.

Quick and easy synthesis of a novel kind of luminescent organic–inorganic hybrid colloidal particles

A new kind of organic–inorganic hybrid colloidal Tb(OH)CO3 particles encapsulated different Tb3+ sensitizer (p-aminosalicylic acid and salicylic acid) has been fabricated in a quick and easy way. The guest ligand can sensize the host Tb3+ of Tb(OH)CO3, and the colloidal particles present strong green luminescence.We also investigated the encapsulation both rhodamine B (RhB) and p-aminosalicylic acid (asa), partially fluorescence resonance energy transfer (FRET) may happened from Tb3+ to RhB. The results show that organic–inorganic hybrid colloidal particles can be used as functional matrices for the encapsulation of a large variety of substances. The organic–inorganic hybrid colloidal particles have many merits and may open up new avenues in various fields, such as cell biology, drug delivery, diagnostics, and so on.

Optoelectrofluidic behavior of metal–polymer hybrid colloidal particles

Behavior of metal–polymer hybrid colloidal particles in an optoelectrofluidic device has been investigated theoretically and experimentally. In the application of hundreds of kHz ac voltage, a variety of optically induced electrokinetic and electrostatic mechanisms affect the movement of gold-coated polystyrene microspheres. The particles repel from the light pattern, and their mobility increases as the amount of gold increases. We apply this model to develop an optoelectrofluidic immunoassay, in which the corresponding metal–polymer hybrid particles are formed by a reaction of antibody-coated gold nanoparticles, antigens, and antibody-coated polystyrene microspheres.

Coating carbon fiber using polyimide–silica nanocomposite by electrophoretic deposition

Polyamic acid–silica hybrid colloidal emulsion with an average particle size of 200 nm was prepared by dispersing nano-silica into polyamic acid colloidal particles. The polyimide–silica hybrid nanocomposite coating was fabricated onto carbon fiber through electrophoretic deposition. The properties of polyamic acid–silica hybrid colloidal emulsion and polyimide–silica hybrid nanocomposite coating onto carbon fiber were characterized using laser diffraction, ZetaPlus Particle Sizing, transmission electron microscopy, field-emission scanning electron microscope, Fourier transform infrared spectroscopy and thermal gravimetric analysis. The results indicated that the small amount of nano-silica would be effectively dispersed in polyamic acid colloidal particles without aggregation and the nano-silica played an important role on keeping stability of polyamic acid–silica hybrid colloidal particles. The polyimide–silica hybrid nanocomposite coating carbon fiber displayed an excellent thermal stability up to 600 °C in the air (less than 5% weight loss for 8 h).

Metal−Polymer Hybrid Colloidal Particles with an Eccentric Structure

We have synthesized metal-polymer hybrid colloidal particles characterized by an eccentric structure by precipitation polymerization in the presence of metal colloids. The key to the formation of an eccentric core-shell structure was to introduce metal colloids a few minutes after (rather than before) starting the polymerization. The hybrid particles were uniform in size, and each one of them contained only one metal nanoparticle at its surface after the experimental procedures had been optimized. This method could be extended to a number of different metal colloids stabilized by small molecules, and the yield was found to be more or less independent of the size of the metal nanoparticles. In addition, the position of the metal nanoparticle in the hybrid particle could be controlled by changing the concentration of cross-linker, and the overall size of the hybrid particles could be altered by solvent treatment. Because of the simplicity of this procedure, it should be possible to use it for the large-scale production of colloidal particles having a hybrid, complex structure.

A Facile Synthesis of Asymmetric Hybrid Colloidal Particles

This paper describes a simple approach to the synthesis of asymmetric, hybrid colloidal particles by precipitation polymerization. The key is to introduce Au or Ag colloids 2 min after (rather than before) starting the polymerization. The hybrid particles were uniform in size, and each one of them only contained one Au (or Ag) nanoparticle in its surface. Due to the simplicity of this procedure, it should be possible to use it for large-scale production. This method can be extended to metal nanoparticles other than Au and Ag and with a range of sizes, as long as they have appropriate stabilizers on the surface.

Self-Assembly of Polyhedral Hybrid Colloidal Particles

ABSTRACTWe have developed a new method to produce hybrid particles with polyhedral shapes in very high yield (liter quantities at up to 70% purity) using a combination of emulsion polymerization and inorganic surface chemistry. The procedure has been generalized to create complex geometries, including hybrid line segments, triangles, tetrahedra, octahedra, and more. The optical properties of these particles are tailored for studying their dynamics and self-assembly. For example, we produce systems that consist of index-matched spheres allowing us to define the position of each elementary particle in three-dimensional space. We present some preliminary studies on the self-assembly of these complex shaped systems based on electron and optical microscopy.

Nucleobase−Metal Hybrid Materials: Preparation of Submicrometer-Scale, Spherical Colloidal Particles of Adenine−Gold(III) via a Supramolecular Hierarchical Self-Assembly Approach

We report a simple and effective supramolecular route for facile synthesis of submicrometer-scale, hierarchically self-assembled spherical colloidal particles of adenine−gold(III) hybrid materials at room temperature. Simple mixture of the precursor aqueous solutions of adenine and HAuCl4 at room temperature could result in spontaneous formation of the hybrid colloidal particles. Optimization of the experimental conditions could yield uniform-sized, self-assembled products at 1:4 molar ration of adenine to HAuCl4. Transmission electron microscopy results reveal the formation of hierarchical self-assembled structure of the as-prepared colloidal particles. Concentration dependence, ratio dependence, time dependence, and kinetic measurements have been investigated. Moreover, spectroscopic evidence [i.e., Fourier transform infrared (FTIR) and UV−vis spectra and wide-angle X-ray scattering data] of the interaction motives causing the formation of the colloidal particles is also presented. The as-prepared nucle...

Semiconductor–polymer hybrid colloidal nanoparticles

A simple conventional emulsion polymerization approach is developed to synthesize hybrid colloidal particles consisting of semiconductor nanocrystals and organic polymers. A uniform distribution of CdSe nanocrystals in composite hybrid particles of ∼20 nm diameter with relatively narrow size distribution is obtained. Transmission electron microscopy, dynamic light scattering and spectroscopic measurements are carried out to elucidate possible mechanisms of hybrid colloidal nanoparticle formation. The effect of crosslinking on the robustness of hybrid colloidal nanoparticles is examined. The versatility of our emulsion polymerization approach is demonstrated by synthesizing hybrid colloids with different monomers. To address photoluminescence loss, a ZnS coating on CdSe nanocrystals is employed to preserve the photoluminescence while maintaining the same average size, size distribution, and composition of the final hybrid nanoparticles. These semiconductor–polymer hybrid colloidal nanoparticles with relatively narrow size distribution may be useful in incorporating semiconductor nanocrystals into conventional lithographic techniques for developing novel nanoscale patterning schemes as well as in extending currently available self-assembly methods.

Preparation of hydroxyapatite rod-like crystals by protein precursor method

Hydroxyapatite (HAP) rod-like crystals were successfully prepared by thermolysis of bovine serum albumin (BSA)/calcium-phosphate (CaP) colloidal precursors. The precursors were obtained by precipitation method from Ca(H 2PO 4) 2 and Ca(OH) 2, in which BSA was added as regulation additive and ultrasound irradiation was utilized as assistant technology. The properties of the precursors, such as size distribution, morphology, thermodynamic changes, were determined by DLS, SPM and TGA–DTA. The characterization results from DLS, SPM, TG–DTA, XRD and SEM indicated that BSA interacted with CaP particles and formed about 7–130 nm BSA/CaP hybrid colloidal particles between 2 and 4 g/L of BSA concentration. With the increasing of sintering temperature, BSA disintegrated and burned out, and rod-like HAP crystals formed at about 600 °C. With the increasing of BSA concentration, the phase composition of products did not change and the HAP crystals became more uniform and smaller. The ratio of length to width ranged from 7.6 to 12 at 4 g/L BSA concentration. This method provides for a controllable bottom-up fabrication of HAP rod-like crystals.

Adhesion Forces between Hybrid Colloidal Particles and Concanavalin A

Hybrid particles of poly(methyl methacrylate) and carboxymethylcellulose, PMMA/CMC, were attached to atomic force microscopy cantilevers and probed against concanavalin A (ConA) films formed either on Si wafers or on CMC substrate. Regardless of the substrate, the approach curves showed different inclinations, indicating that the probe first touches a soft surface and then a hard substrate. The distance corresponding to the soft layer was estimated as 20 +/- 10 nm and was attributed to the CMC layers attached to the hybrid particles surfaces. Probing PMMA/CMC particles against ConA adsorbed onto Si wafers yielded retract curves with a sawlike pattern. The average range of adhesion forces (maximum pull-off distance) and mean adhesion force were estimated as 100 +/- 40 nm and -11 +/- 7 nN, respectively, evidencing multiple adhesions between CMC sugar residues and ConA. However, upon probing against ConA adsorbed onto CMC substrates, the mean pull-off distance and mean adhesion force were reduced to 37 +/- 18 nm and -3 +/- 1 nN, respectively, indicating that the ConA molecules immobilized onto CMC films are less available to interact with the hybrid particle than the ConA molecules adsorbed onto Si wafers. Another set of experiments, where PMMA/CMC particle probed against ConA-covered Si wafers in the presence of mannose, showed that the addition of mannose led to a considerable decrease in the mean adhesion force from -11 +/- 7 to -3 +/- 1 nN. Two hypotheses have been considered to explain the effect caused by mannose addition. The first suggested the desorption of ConA from the substrate so that the hybrid particle would probe bare Si wafer (weak adhesion). The second proposed the adsorption of mannose onto the ConA layer so that mannose layer would probe against another mannose layer, leading to low adhesion forces. In situ ellipsometry and capillary electrophoresis have been applied to check the hypotheses.