Chiroptical materials found in butterflies, beetles, stomatopod crustaceans, and other creatures are attributed to biocomposites with helical motifs and multiscale hierarchical organization. These structurally sophisticated materials self-assemble from primitive nanoscale building blocks, a process that is simpler and more energy efficient than many top-down methods currently used to produce similarly sized three-dimensional materials. Here, we report that molecular-scale chirality of a CdTe nanoparticle surface can be translated to nanoscale helical assemblies, leading to chiroptical activity in the visible electromagnetic range. Chiral CdTe nanoparticles coated with cysteine self-organize around Te cores to produce helical supraparticles. D-/L-Form of the amino acid determines the dominant left/right helicity of the supraparticles. Coarse-grained molecular dynamics simulations with a helical pair-potential confirm the assembly mechanism and the origin of its enantioselectivity, providing a framework for engineering three-dimensional chiral materials by self-assembly. The helical supraparticles further self-organize into lamellar crystals with liquid crystalline order, demonstrating the possibility of hierarchical organization and with multiple structural motifs and length scales determined by molecular-scale asymmetry of nanoparticle interactions.

Copper chalcogenide nanoparticles (NPs) represent a promising material for solar energy conversion, electrical charge storage, and plasmonic devices. However, it is difficult to achieve high-quality NP dispersions in experimentally convenient and technologically preferred aqueous media. Also problematic is the transition from NP dispersion to continuously crystalline nanoscale materials, for instance, nanowires, nanoribbons, or similar high aspect ratio nano/microstructures capable of charge transport necessary for such applications. All previous examples of copper sulfide assemblies contained insulating gaps between NPs. Here we show that aqueous synthesis of high-quality monodispersed high-chalcocite β-Cu2S NPs, with sizes from 2 to 10 nm, is possible. When reaction time increased, the NP shape evolved from nearly spherical particles into disks with predominantly hexagonal shape. Moreover, the monodispersed β-Cu2S NPs were found to spontaneously self-assemble into nanochains and, subsequently, to nanoribbons. The width and length of the nanoribbons were 4-20 nm and 50-950 nm, respectively, depending on the assembly conditions. We observed the formation of the nanoribbons with continuous crystal lattice and charge transport pathways, making possible the utilization of self-assembly processes in the manufacturing of photovoltaic, plasmonic, and charge storage devices.

Single-crystal a-MnO 2 ultralong nanowires ($40 mm in length, $15 nm in diameter), which were synthesized by a simple polyvinylpyrrolidone (PVP) assisted hydrothermal route, exhibited a better electrical conductivity, a highest specific capacitance of 345 F g À1 at a current density of 1 A g À1 with high rate capability (54.7% at 10 A g À1 ) and good cycling stability.

Well-defined faceted zinc stannate, including cubic ZnSnO 3 and octahedral Zn 2 SnO 4 , microcrystals were synthesized in a large scale by a one-step chemical solution route, in which the phase control was simply accomplished by only changing stannic precursors. These faceted cubic ZnSnO 3 and octahedral Zn 2 SnO 4 microcrystals are easily converted to faceted hollow structures with a shape preserved through an acid etching process. Possible growth and etching mechanisms of these faceted microcrystals have been proposed. The hollow structures of zinc stannate were exploited as gas sensors and exhibit improved sensing performances to a series of gases (especially with regard to H 2 S and C 2 H 5 OH); moreover, the sensitivity and recovery time of Zn 2 SnO 4 hollow octahedral structures to H 2 S and C 2 H 5 OH are both higher than those of the cubic structures, which may find potential industrial applications in detecting gases.