Temperature-responsive binary superlattices prepared by the selective solvent evaporation of O/W microemulsion composed of gold nanoparticles and surfactants.

Binary nanoparticle superlattices (BNSLs) are one of the important classes of nanomaterial architectures for a wide range of potential applications because they can provide synergistically enhanced properties depending on the morphology and spatial arrangement of nanoparticles (NPs). However, although many studies have been conducted on the fabrication of BNSLs, there are still several challenges in achieving BNSLs with a three-dimensional lattice due to their complicated synthesis, hindering their practical applications. Herein, we report the fabrication of temperature-sensitive BNSLs in complexes of gold nanoparticles (AuNPs), Brij 58 surfactant, and water a two-step evaporation method.

SANS characterization of time dependent, slow molecular exchange in an SDS micellar system.

We have investigated the molecular exchange of sodium dodecyl sulfate (SDS) micelles in aqueous solution by time-resolved small angle neutron scattering (TR-SANS) measurements as a function of the surfactant and salt concentration. Starting with deuterated (d-SDS) and protonated (h-SDS) SDS micelles, surfactant exchange across the micelles leads to a randomized distribution of d-SDS and h-SDS within each micelle. By employing the contrast matching technique, we have studied this randomization process which is a direct measure of the molecular exchange of this system.

Spontaneous Formation of Highly Stable Nanoparticle Supercrystals Driven by a Covalent Bonding Interaction.

Nanoparticle supercrystals (NPSCs) are of great interest as materials with emergent properties. Different types of intermolecular forces, such as van der Waals interaction and hydrogen bonding, are present in the NPSCs fabricated to date. However, the limited structural stability of such NPSCs that results from the weakness of these intermolecular forces is a challenge.

Micelle-Assisted Formation of Nanoparticle Superlattices and Thermally Reversible Symmetry Transitions.

Nanoparticle superlattices (NPSLs) are of great interest as materials with designed emerging properties depending on the lattice symmetry as well as composition. The symmetry transition of NPSLs depending on environmental conditions can be an excellent ground for making new stimuli-responsive functional materials. Here, we report a spherical micelle-assisted method to form exceptionally ordered NPSLs which are inherently sensitive to environmental conditions.

Anisotropic interaction driven surface modulation on spray-dried microgranules.

Rapid evaporation of solvent from spray colloidal droplets induces directed self-assembly among the nanoparticles, eventually interlocking them into correlated granular structures. In this work, it is demonstrated that anisotropy in colloidal interparticle interaction plays a key role in governing the surface topology of spray-dried granules. Colloidal dispersion comprised of spherical nanosilica (NS) and cylindrical carbon nanotubes (CNT) was chosen as a model system in this regard.

Spontaneous hybrids of graphene and carbon nanotube arrays at the liquid-gas interface for Li-ion battery anodes.

We demonstrate that hybrid structures of graphene and single-walled carbon nanotubes (SWNTs) are precisely controlled at the liquid-gas interface. The functionalized SWNT Langmuir monolayers anchor single-layer graphene nanosheets (GNSs) suspended in water via Coulomb interaction at the interface. This GNS/SWNT hybrid multilayer electrode can be a promising anode material for Li-ion batteries, offering high specific capacity, outstanding power capability, and excellent cyclability.

Green Synthesis of High-Purity Mesoporous Gold Sponges Using Self-Assembly of Gold Nanoparticles Induced by Thiolated Poly(ethylene glycol).

A facile and green synthesis method for mesoporous gold sponges has been developed, which involves a simple mixing of a very small amount of thiolated-poly(ethylene glycol) (SH-PEG) and citrate-covered gold nanoparticles (Au NPs) in aqueous solution at room temperature. While SH-PEG molecules have been widely used as biocompatible hydrophilic capping agents for Au NPs for stable dispersion in aqueous solution, here they are used as destabilizing agents. When SH-PEG molecules are mixed with citrate-covered Au NPs at the molar ratio ranging from 3 to 20 (SH-PEG/Au NP), mesoporous gold sponges with randomly interconnected 3D network structures are formed within 2 to 3 h.

Selective distributions of functionalized single-walled carbon nanotubes in a polymeric reverse hexagonal phase.

We have investigated the distributions of individually isolated and hydrophilically functionalized single-walled carbon nanotubes (p-SWNTs) in the Pluronic L121-water system at the reverse hexagonal phase using small-angle X-ray scattering (SAXS) and contrast-matched small-angle neutron scattering (SANS) measurements. As the p-SWNT-L121-water system is transitioned from the lamellar phase to the reverse hexagonal phase with temperature, p-SWNTs which were selectively distributed in the polar layers of the lamellar structure become selectively distributed in the cylindrical polar cores of the reverse hexagonal structure, forming a hexagonal array of p-SWNTs. This was clearly confirmed by the contrast-matched SANS measurements.

Highly ordered and highly aligned two-dimensional binary superlattice of a SWNT/cylindrical-micellar system.

We report a highly ordered intercalated hexagonal binary superlattice of hydrophilically functionalized single-walled carbon nanotubes (p-SWNTs) and surfactant (C12 E5 ) cylindrical micelles. When p-SWNTs (with a diameter slightly larger than that of the C12 E5 cylinders) were added to the hexagonally packed C12 E5 cylindrical-micellar system, p-SWNTs positioned themselves in such a way that the free-volume entropies for both p-SWNTs and C12 E5 cylinders were maximized, thus resulting in the intercalated hexagonal binary superlattice. In this binary superlattice, a hexagonal array of p-SWNTs is embedded in a honeycomb lattice of C12 E5 cylinders.