Additive-free size-controlled synthesis of gold square nanoplates using photochemical reaction in dynamic phase-separating media

Crumpled Versus Flat Gold Nanosheets: Temperature-Regulated Synthesis and Their Plasmonic and Catalytic Properties

We report a high-yield synthesis of gold (Au) nanosheets with tunable size and surface morphology in the aqueous phase. In particular, crumpled and flat Au nanosheets with a thickness of ∼10 nm could be selectively produced in high purity when the reaction was conducted at room temperature and in an ice-water bath, respectively. Unlike Au nanoplates/nanoprisms in the form of well-defined triangles or hexagons documented in previous studies, the current products exhibit random in-plane branches or holes, together with wavy edges. Strong absorbance in the NIR region was observed for all the Au nanosheet products. When serving as electrocatalysts for the ethanol oxidation reaction, the current products exhibited an enhanced activity and operation stability, as compared to quasi-spherical counterparts.

Laser-Induced Single-Molecule Extraction and Detection in Aqueous Poly(N-isopropylacrylamide)/1-Butanol Solutions

We report photothermal phase separation of aqueous poly(N-isopropylacrylamide) (PNIPAM)/1-butanol (BuOH) solutions by focused 1064 nm laser irradiation and subsequent single microparticle formation in the solution. The single microparticle [diameter = ∼10 μm and volume = ∼picoliter (pL)] produced by laser irradiation was optically trapped by the incident 1064 nm laser beam, and this enabled us in situ Raman/fluorescence microspectroscopies of the particle. Raman spectroscopy demonstrated that the particle produced by laser irradiation was composed of PNIPAM and BuOH. In the presence of rhodamine B (RhB) in the solution, RhB was distributed from the water phase to the PNIPAM/BuOH microparticle produced by laser irradiation, as confirmed by fluorescence microspectroscopy. Laser-induced distribution/extraction of RhB to a single PNIPAM/BuOH microparticle was shown to be possible at the RhB concentration as low as 10^-14 mol/dm³, where the RhB fluorescence intensity from the particle showed a step-by-step increase by every ∼3 min laser irradiation. This is the first demonstration of laser-induced simultaneous extraction and detection of single RhB molecules in solution.

Two-Dimensional Metal Nanomaterials: Synthesis, Properties, and Applications

As one unique group of two-dimensional (2D) nanomaterials, 2D metal nanomaterials have drawn increasing attention owing to their intriguing physiochemical properties and broad range of promising applications. In this Review, we briefly introduce the general synthetic strategies applied to 2D metal nanomaterials, followed by describing in detail the various synthetic methods classified in two categories, i.e. bottom-up methods and top-down methods. After introducing the unique physical and chemical properties of 2D metal nanomaterials, the potential applications of 2D metal nanomaterials in catalysis, surface enhanced Raman scattering, sensing, bioimaging, solar cells, and photothermal therapy are discussed in detail. Finally, the challenges and opportunities in this promising research area are proposed.

Sheetlike gold nanostructures/graphene oxide composites via a one-pot green fabrication protocol and their interesting two-stage catalytic behaviors

Au nanoplate/GO composites are facilely synthesized via a one-pot green protocol. The composites display a fascinating two-stage catalytic behavior, where the catalytic reactivity of the latter stage increases substantially by a factor of 9 times.

Micropatterned fabrication of chitosan-based thermoresponsive membranes for improving cell adhesion and gene expression

A simple, rapid, and economical method to fabricate micropatterned thermoresponsive chitosan membranes was developed. Porous polystyrene films were prepared by liquid-induced phase separation. The size of pores on polystyrene films could be regulated by adjusting the composition of coagulation bath and changing the solvent evaporation rate. Subsequently, chitosan-based thermoresponsive membranes with island protrusions were fabricated using porous polystyrene films as templates. The effects of the micropatterns on the behaviors of mouse fibroblast L929 were investigated. The presence of micropatterns altered the cell cycle distribution and enhanced the gene expression of cyclin D1 and integrin β1. The micro-convex surface could promote the adhesion and proliferation of L929 cells. These results provided valuable guidance to design appropriate topographic surfaces for tissue engineering applications.

Picosecond dynamics of hydrogen bond rearrangements during phase separation of a triethylamine and water mixture

A picosecond temperature jump experiment reveals that phase separation in a liquid triethylamine (TEA)–water mixture started from hydrogen bond scission of TEA–water aggregates in TEA-rich regions and then in water-rich regions.