The assembly of complex structures out of simple colloidal building blocks is of practical interest for building materials with unique optical properties (for example photonic crystals and DNA biosensors) and is of fundamental importance in improving our understanding of self-assembly processes occurring on molecular to macroscopic length scales. Here we demonstrate a self-assembly principle that is capable of organizing a diverse set of colloidal particles into highly reproducible, rotationally symmetric arrangements. The structures are assembled using the magnetostatic interaction between effectively diamagnetic and paramagnetic particles within a magnetized ferrofluid. The resulting multipolar geometries resemble electrostatic charge configurations such as axial quadrupoles ('Saturn rings'), axial octupoles ('flowers'), linear quadrupoles (poles) and mixed multipole arrangements ('two tone'), which represent just a few examples of the type of structure that can be built using this technique.

HKUST-1, a metal-organic framework (MOF) material containing Cu(II)-paddlewheel-type nodes and 1,3,5-benzenetricarboxylate struts, features accessible Cu(II) sites to which solvent or other desired molecules can be intentionally coordinated. As part of a broader investigation of ionic conductivity in MOFs, we unexpectedly observed substantial proton conductivity with the "as synthesized" version of this material following sorption of methanol. Although HKUST-1 is neutral, coordinated water molecules are rendered sufficiently acidic by Cu(II) to contribute protons to pore-filling methanol molecules and thereby enhance the alternating-current conductivity. At ambient temperature, the chemical identities of the node-coordinated and pore-filling molecules can be independently varied, thus enabling the proton conductivity to be reversibly modulated. The proton conductivity of HKUST-1 was observed to increase by ~75-fold, for example, when node-coordinated acetonitrile molecules were replaced by water molecules. In contrast, the conductivity became almost immeasurably small when methanol was replaced by hexane as the pore-filling solvent.

Gold nanoparticle-polymer composites are versatile and diverse functional materials, with applications in optical, electronic and sensing devices. This tutorial review focuses on the use of polymers to control the assembly of gold nanoparticles. Examples of synthetic polymers and biopolymers are provided, as well as applications of the composite materials in sensing and memory devices.

Thermotherapy is a promising technique for the minimally invasive elimination of solid tumors. Here we report the fabrication of protein-coated iron oxide NPs (12 nm core) for use as thermal therapeutic agents. These albumin-passivated NPs are stable under physiological conditions, with rapid heating and cell killing capacity upon alternating magnetic field (AMF) exposure. The mode of action is specific: no measurable cytotoxicity was observed for the particle without AMF or for AMF exposure without the particle.

The creation of ordered cellular structures is important for tissue engineering research. Here, we present a novel strategy for the assembly of cells into linear arrangements by negative magnetophoresis using inert, cytocompatible magnetic nanoparticles. In this approach, magnetic nanoparticles dictate the cellular assembly without relying on cell binding or uptake. The linear cell structures are stable and can be further cultured without the magnetic field or nanoparticles, making this an attractive tool for tissue engineering.

Microporous capsules (MCs) such as polymerosomes [1,2] feature attractive properties for potential applications in materials development, optics, electronics, and delivery. [3,4] Colloidosomes are a related class of MCs whose shells consists of densely packed colloidal particles. These systems feature useful attributes including enhanced mechanical stability and controlled pore-size distribution, [5] as well as the optical, fluorescent, and magnetic properties of their precursor particles.Colloidosomes feature an identical solvent inside and out (typically water), and have been generally synthesized using micrometer-or submicrometer-sized particles. [4a,6] However, the formation of stable colloidosomes using nanoparticles (NPs) <20 nm in diameter remains a challenge. [7] The competition between the interfacial energy and the spatial fluctuation of the NPs resulting from thermal energy causes instability of the emulsions. Recent approaches to fabricate colloidosomes have included different types of NPs, as well as the use of assembly strategies. [8,9] For example, Duan et al. have used agarose to gelate water at the water-oil interface and transferred the resultant MCs into water to create stable colloidosomes. [9] In recent studies, we and others have developed various crosslinking reactions between NPs at water-oil droplet interfaces. [10] However, to the best of our knowledge there are no reports of successful transfer of these crosslinked droplets into water to synthesize colloidosomes.Herein, we report the fabrication of stable magnetic colloidosomes by crosslinking NPs at a water-oil interface using click chemistry under ambient conditions. In this strategy, alkyne-and azide-functionalized Fe 3 O 4 NPs were coassembled at the interface and covalently linked using a Cu(I)-catalyzed Huisgen click reaction. [11,12] There are two major advantages for this interfacial crosslinking method. First, click chemistry involving alkyne and azide functional groups is highly selective and essentially inert to the many functional groups and environmental conditions (e.g., pH and solvent). [13][14][15][16][17] Second, this methodology provides dense packing of NPs on the colloidosome shell, resulting in high stability of the colloidosomes.The alkyne (IO-1) and azide (IO-2) NPs used in this study were formed by place-exchange of oleic acid from Fe 3 O 4 NPs that were 11.3 AE 2 nm in diameter (see Supporting Information, Figure S1). These NPs were dissolved in an equimolar ratio in oil (a mixture of toluene and methylene chloride with a 7:1 ratio), and an aqueous solution of the Cu(I) catalyst (a mixture of CuSO 4 and sodium L-ascorbate) was added with vigorous shaking for %30 s (Scheme 1). The colloidosomes formed by this technique were 49 AE 15 mm (Figure 1a) in diameter, and required a crosslinking time of 30 min with a catalyst concentration of 0.8 mM to form stable assemblies. The catalyst concentration had little effect on the shape and size of the colloidosomes (see Supporting Information, Figure S2), however onl...

We have explored the mechanism and differential uptake of BSA coated Fe 3 O 4 nanoparticles (NPs) by different cancerous and isogenic cell types.

Involuntary association: Anionic beta-galactosidase enzymes associate with positively charged Au nanoparticles to produce reduced-charge conjugates, which assemble at oil-water interfaces to result in stable microcapsules (see picture). The microcapsules were formed quickly and showed high enzymatic activity, which makes them promising materials for biotechnology applications.