Controllable self-assembly of nanoscale building blocks into larger specific structures provides an effective route for the fabrication of new materials with unique optical, electronic, and magnetic properties. The ability of nanoparticles (NPs) to self-assemble like molecules is opening new research frontiers in nanoscience and nanotechnology. We present a new class of amphiphilic "colloidal molecules" (ACMs) composed of inorganic NPs tethered with amphiphilic linear block copolymers (BCPs). Driven by the conformational changes of tethered BCP chains, such ACMs can self-assemble into well-defined vesicular and tubular nanostructures comprising a monolayer shell of hexagonally packed NPs in selective solvents. The morphologies and geometries of these assemblies can be controlled by the size of NPs and molecular weight of BCPs. Our approach also allows us to control the interparticle distance, thus fine-tuning the plasmonic properties of the assemblies of metal NPs. This strategy provides a general means to design new building blocks for assembling novel functional materials and devices.

Amphiphilic plasmonic micelle-like nanoparticles (APMNs) composed of gold nanoparticles (AuNPs) and amphiphilic block copolymers (BCPs) structurally resemble polymer micelles with well-defined architectures and chemistry. The APMNs can be potentially considered as a prototype for modeling a higher-level self-assembly of micelles. The understanding of such secondary self-assembly is of particular importance for the bottom-up design of new hierarchical nanostructures. This article describes the self-assembly, modeling, and applications of APMN assemblies in selective solvents. In a mixture of water/tetrahydrofuran, APMNs assembled into various superstructures, including unimolecular micelles, clusters with controlled number of APMNs, and vesicles, depending on the lengths of polymer tethers and the sizes of AuNP cores. The delicate interplay of entropy and enthalpy contributions to the overall free energy associated with the assembly process, which is strongly dependent on the spherical architecture of APMNs, yields an assembly diagram that is different from the assembly of linear BCPs. Our experimental and computational studies suggested that the morphologies of assemblies were largely determined by the deformability of the effective nanoparticles (that is, nanoparticles together with tethered chains as a whole). The assemblies of APMNs resulted in strong absorption in near-infrared range due to the remarkable plasmonic coupling of Au cores, thus facilitating their biomedical applications in bioimaging and photothermal therapy of cancer.

The hydrodynamics of laminar flow in a microfluidic device has been used to control the continuous self-assembly of gold nanoparticles (NPs) tethered with amphiphilic block copolymers. Spherical micelles, giant vesicles (500 nm-2.0 μm), or disk-like micelles could be formed by varying the flow rates of fluids. Such vesicles can release encapsulated hydrophilic species by using near-IR light.

This paper describes an effective approach to order gold nanorods (NRs) within cylindrically confined microdomains of block copolymer-(BCP-) based supramolecular assemblies. Individual BCP micelles encapsulated with wellordered NRs can be obtained by disassembling the supramolecular structures. The mismatch of binary polymer brushes with different lengths on the surface of the NRs was used to effectively improve the dispersion of the NRs within polymer matrix, due to enhanced wetting of the brushes by surrounding mismatch polymers. This enables us to quantitatively explore the location and orientation of the NRs within confined geometries. By varying the content of NRs, the aspect ratio of the NRs, or the diameter of the cylindrical BCP micelles, the orientation of the NRs within micelles can be tuned to form one-dimensional nanostrings with end-to-end organization of NRs along the micelles or with side-by-side twisted arrangement of NRs perpendicular to the micelles. UV−vis spectroscopy measurements and finitedifference time-domain (FDTD) calculations confirm that our approach provides a simple yet versatile route to tune the optical properties of the hybrid micelles by controlling the ordering of the NRs. This work provides guidelines for dispersing other functional anisotropic NPs, and lays groundwork for the fabrication of optical and electronic devices.

This communication reports the amphiphilic block copolymer driven self-assembly of Au nanoflowers into nanoparticle vesicles and the near-infrared light triggered release of hydrophilic molecules encapsulated in vesicles.