Synthesis of Hollow Asymmetrical Silica Dumbbells with a Movable Inner Core

Abstract

Hollow asymmetrical silica dumbbells containing a movable inner core were fabricated by a template-assisted method. Three different templates were employed for the fabrication of the hollow asymmetrical dumbbells. For the preparation of the first template, silica particles were uniformly covered with a cross-linked polymethylmethacrylate (PMMA) shell and the polymerization of styrene was conducted to induce a protrusion of polystyrene (PSt) from the PMMA shell. Anisotropic colloids composed of silica, PMMA, and PSt were used as templates, coated with a silica shell, and held at 500°C for 2 h to remove the polymer interior components of the template colloid. The heat treatment successfully produced hollow asymmetrical silica dumbbells containing an inner silica core. After being dried, approximately 50% of the inner silica particles that were originally coated with PMMA ended up in the other hollow sphere in which the PSt component existed before heat treatment, indicating that the inner silica particles could pass through the hollow asymmetrical dumbbells' necks and were free to move in the interior. In the preparation of the second and third asymmetrical dumbbell templates, magnetic silica particles and titania particles, respectively, were covered with a PMMA shell to incorporate externally responsive particles into the hollow silica shells as above. The successful syntheses demonstrated the generality of our approach. The passage of the responsive particles through the dumbbell's neck enabled active control of the position of the responsive particles inside the asymmetrical dumbbells by external fields.

Surface roughness directed self-assembly of patchy particles into colloidal micelles

“…Besides the one-patch model particles presented here, a wide variety of synthetic routes for colloids with more complex patterns of rough and smooth surfaces is readily available in literature (28,(34)(35)(36)(37)(38)(39)(40). In particular, we emphasize that size, number and even the angle between patches can be controlled (38)(39)(40).…”

Polarizability and alignment of dielectric nanoparticles in an external electric field: Bowls, dumbbells, and cuboids

“…5(c) as a function of the number of atoms N for several values for d/σ , for an electric field strength E 0 = 100 V mm −1 , an atomic polarizability α 0 = 5.25 Å 3 , and at room temperature (T = 293 K). To the numerical results, linear functions of form (20) have been fitted to determine f , which we now find to be negative. This implies that the axis of rotational symmetry is, for bowl-shaped particles, the least favorable direction for the external field.…”

“…Rodlike particles in a liquid dispersion, for instance, can spontaneously align at sufficiently high concentrations solely due to their excluded volume interactions, 11 but their self-organisation has also been driven by external magnetic or electric fields, [12][13][14][15][16] by substrates that preferentially orient the rods, 17,18 or by fluid flow. 19 Also, more complicated shapes have been synthesized and studied, for instance, dumbbells, 2,[20][21][22] cubes, 23 and bowls. 21,24,25 In this article we study the electric-field assisted alignment of anisotropic nanoparticles by calculating their polarizability tensor starting from a microscopic picture of polarizable units that we call "united atoms" or just briefly "atoms," even though also larger units could have been taken.…”

Direct Template Approach for the Formation of (Anisotropic shape) Hollow Silicate Microparticles

“…This process can generate most complicated structures with good structural control of various sizes and shapes wherein the colloidal templates coated with different materials by means of sol-gel process [4], layer by layer approach [5] or chemical deposition [6], after then by calcinations or acid dissolution, hollow particles formed. Also, different anisotropic templates (such as inorganic {gold, hematites, silica, bimetallic} [7,8] , organic [9] [10,11] and biotemplates {cellusose, collagen/silk, and DNA/virus} [12,13]) had been utilized in fabricating anisotropic hollow particles.…”