A "smart" core-shell complex is designed to combine a catalytic reaction and automatic separation through remote light control. Here, we present the induced amphiphilic behavior of a surfactant-encapsulated polyoxometalate complex with photoresponsive azobenzene units on the periphery. The reversible phase transfer of the complex shuttle between two incompatible phase termini, driven by a photoisomerization-induced polarity change, further facilitates the separation and recycle of the catalyst.

Gold nanorods are excellent anisotropic building blocks for plasmonic chiral nanostructures. The near-infrared plasmonic band of nanorods makes them highly desirable for biomedical applications such as chiral bioimaging and sensing, in which a strong circular dichroism (CD) signal is required. Chiral assemblies of gold nanorods induced by self-associating peptides are especially attractive for this purpose as they exhibit plasmonic-enhanced chiroptical activity. Here, we showed that the presence of cetyltrimethylammonium bromide (CTAB) micelles in a gold nanorod solution promoted the self-association of l-/d-glutathione (GSH) and significantly enhanced the chirality of the resulting plasmonic nanochains. Chiroptical signals for the ensemble in the presence of CTAB micelles were 20 times greater than those obtained below the critical micelle concentration of CTAB. The strong optical activity was attributed to the formation of helical GSH oligomers in the hydrophobic core of the CTAB micelles. The helical GSH oligomers led the nanorods to assemble in a chiral, end-to-end crossed fashion. The CD signal intensities were also proportional to the fraction of nanorods in the nanochains. In addition, finite-difference time-domain simulations agreed well with the experimental extinction and CD spectra. Our work demonstrated a substantial effect from the CTAB micelles on gold nanoparticle assemblies induced by biomolecules and showed the importance of size matching between the inorganic nanobuilding blocks and the chiral molecular templates (i.e., the GSH oligomers in the present case) in order to attain strong chiroptical activities.

The design and assembly of novel colloidal particles are of both academic and technological interest. We developed a wet-chemical route to synthesize monodisperse bent rigid silica rods by controlled perturbation of emulsion-templated growth. The bending angle of the rods can be tuned in a range of 0–50° by varying the strength of perturbation in the reaction temperature or pH in the course of rod growth. The length of each arm of the bent rods can be individually controlled by adjusting the reaction time. For the first time we demonstrated that the bent silica rods resemble banana-shaped liquid-crystal molecules and assemble into ordered structures with a typical smectic B2 phase. The bent silica rods could serve as a visualizable mesoscopic model for exploiting the phase behaviors of bent molecules which represent a typical class of liquid-crystal molecules.

Reversible stimuli-responsive self-assembly systems, particularly those involving photo-controlled assemblies and disassemblies, have attracted much attention over recent years, due to their diverse potentials in the fi elds of drug delivery, [ 1 ] switchable catalysis, [ 2 ] tunable sol-gel transition [ 3 ] and so forth. Various building blocks containing photo-responsive groups, [ 4 ] such as metal and metal oxide nanoparticles, [ 5 ] silica microspheres, [ 6 ] and polymers, [ 7 ] as well as small molecules, [ 3 , 8 ] were used to induce aggregation and dispersion in solution in response to the light stimulus. However, the integration of the smart response with specialized functions in a single system still remains a challenge. Polyoxometalates (POMs) as a class of nanoscale inorganic polyanionic clusters possess versatile properties in catalysis, redox reactions, medicines, etc . [ 9 ] The surface modifi cation with organic cations through electrostatic interactions makes possible the ready integration of various additional functional properties into POMs, [ 10 ] in addition to the improvement of the solubility in weakly polar solvents and the structural stability for diverse chemical environments as well as the promotion of catalytic reaction effi ciency. [ 11 ] In contrast to that only giant POMs are found to show self-assembling behavior in water, [ 12 ] most of these surfactant-encapsulated POM (SEP) and covalent hybrid complexes can self-assemble in organic media and the states at which they exist are dominated by the nature of solvents, [ 11a , 13 ] the amphiphilicity and structure of surfactants, as well as the size and charge density of POMs. [ 14 ] Up to date, none of these complexes have been found to undergo reversible assembly and disassembly processes, although they are very important in governing the catalytic and separation performance of the POM-based catalysts. To realize the high effi cient catalysis of water insoluble substrates, POMs were usually transferred into organic phase through a hydrophobic surface modifi cation of organic cations. In some reaction systems, the control for the reaction process is critical. Up to date, almost all the controllable POM catalyzed reactions depend on the additional chemicals, the oxidant exhaustion, or the temperature control. [ 15 ] It is found that the catalysis and catalytic effi ciency of POMs in organic phase are still strongly relied on their existing states. If one can control the catalytic reactions of POMs through the responsive assembly and disassembly, POMs will become more useful catalysts in some specifi c systems, such as microfl uid, patterned local reactions and catalyst separations. It is usually critical to introduce responsive groups into the SEPs for smart and switchable assemblies. [ 16 ] Considering that light can offer a convenient pathway for the direct modulation of the assembled state of SEPs without introducing chemical additives, it is of interest to develop photo-responsive SEPs for the fabrication of POM-based functional m...

Multicomponent colloidal nanostructures (MCNs) exhibit intriguing topologically dependent chemical and physical properties. However, there remain significant challenges in the synthesis of MCNs with high-order complexity. Here we show the development of a general yet scalable approach for the rational design and synthesis of MCNs with unique coaxial-like construction. The site-preferential growth in this synthesis relies on the selective protection of seed nanoparticle surfaces with locally defined domains of collapsed polymers. By using this approach, we produce a gallery of coaxial-like MCNs comprising a shaped Au core surrounded by a tubular metal or metal oxide shell. This synthesis is robust and not prone to variations in kinetic factors of the synthetic process. The essential role of collapsed polymers in achieving anisotropic growth makes our approach fundamentally distinct from others. We further demonstrate that this coaxial-like construction can lead to excellent photocatalytic performance over conventional core–shell-type MCNs.

Managing the blues: Chiral heteropoly blues of achiral polyoxometalate clusters were created through an intermolecular interaction with a chiral organic compound. Controllable chiroptical switching of the cluster complexes was possible through reversible photochromism of the polyoxometalates (see picture).

Bent colloidal rods exhibit fascinating polar ordering and chirality formation despite the achiral nature of the rods.

Flower-like gold nanoparticles (Au-NPs) were fabricated in surfactant-PMo(12) hybrid assemblies, where PMo(12) served as a UV-switchable reducing agent for producing Au-NPs and the organic surfactant matrices played the role of a soft template for the formation of flower-like structure of Au-NPs.