Peng-peng Wang

Three-Dimensional Assembly of Single-Layered MoS2

Assembly of single layers: Three-dimensional assembly of single-layered MoS2 is achieved on a large scale via a solution method. The as-prepared tubular architectures have tunable size and mesopores in the shell, which are desirable for applications. As a example, they exhibit excellent lithium storage properties and are highly active for hydrodesulfurization of thiophene resulting from their structural advantages.

Hydrothermal Synthesis of Hollow Silica Spheres under Acidic Conditions

It is well-known that silica can be etched in alkaline media or in a unique hydrofluoric acid (HF) solution, which is widely used to prepare various kinds of hollow nanostructures (including silica hollow structures) via silica-templating methods. In our experiments, we found that stöber silica spheres could be etched in generic acidic media in a well-controlled way under hydrothermal conditions, forming well-defined hollow/rattle-type silica spheres. Furthermore, some salts such as NaCl and Na(2)SO(4) were found to be favorable for the formation of hollow/rattle-type silica spheres.

A 1D/2D Helical CdS/ZnIn2S4 Nano-Heterostructure†

Multidimensional nano-heterostructures (NHSs) that have unique dimensionality-dependent integrative and synergic effects are intriguing but still underdeveloped. Here, we report the first helical 1D/2D epitaxial NHS between CdS and ZnIn2S4. Experimental and theoretical studies reveal that the mismatches in lattice and dangling bonds between 1D and 2D units govern the growth procedure. The resulting well-defined interface induces the delocalized interface states, thus facilitate the charge transfer and enhance the performance in the photoelectrochemical cells. We foresee that the mechanistic insights gained and the electronic structures revealed would inspire the design of more complex 1D/2D NHSs with outstanding functionalities.

Fine tuning of the structure of Pt-Cu alloy nanocrystals by glycine-mediated sequential reduction kinetics.

Uniform Pt-Cu alloy nanocrystals in the shape of dendrite, yolk-cage, and box structures are prepared via a facile wet-chemical reduction route in which glycine is demonstrated to alter the reduction kinetics of metal cations, critical to the morphology of the obtained product. These alloy nanocrystals exhibit superior specific activity and stability in the electro-oxidation of methanol.

Family of multifunctional layered-lanthanum crystalline nanowires with hierarchical pores: hydrothermal synthesis and applications.

A family of layered-lanthanum crystalline NWs with hierarchical pores was synthesized via a facile hydrothermal route. The diameter of the pores ranged from 2 to 50 nm, covering both the micropore and the mesopore scale. Luminescence was introduced by doping nanowires with Eu(3+) ion. By combining the merits of hierarchical porous nanowires and layered hydroxides, these as-synthesized products have shown a unique bioengineering application of capturing and releasing short DNA fragments rapidly in dilute solution, and environmental engineering applications due to their remarkable capability to remove organic dye from water.

Biomimetic Multifunctional Nanochannels Based on the Asymmetric Wettability of Heterogeneous Nanowire Membranes

A charged heterogeneous nanowire membrane with asymmetric wettability serves as a biomimetic passive channel when the bilayer is hydrophilic; It also functions as pH valve based on the hydrophobic CaWO4 layer (contact angle of 145.3˚±0.3˚) and hydrophilic MnO2 layer. Moreover, a reversible ionic rectification is realized in the above-mentioned semi-hydrophobic and hydrophilic state with strong acid environment or in the complete hydrophobic stage with a moderate discrepancy (CA of CaWO4 and MnO2 layer are 141.3˚±0.3˚ and 157.6˚±2.0˚, respectively) in near neuter condition.

Inorganic Nanostructures with Sizes down to 1 nm: A Macromolecule Analogue

Ultrathin nanostructures exhibit many interesting properties which are absent or less-pronounced in traditional nanomaterials of larger sizes. In this work, we report the synthesis of ultrathin nanowires and nanoribbons of rare earth hydroxides and demonstrate some new phenomena caused by their atomic-level lateral size (1 nm), including ligand-induced gelation, self-assembly framework, and conformational diversity. These features are typically, although not exclusively, found in polymer solutions. The properties of the inorganic backbone and the emerging polymeric characteristics combined prove to be very promising in the design of new hybrid materials.

Self-Adjustable Crystalline Inorganic Nanocoils

Biomacromolecules such as proteins, although extremely complex in microstructure, can crystallize into macro-sized crystals after self-adjusting their shapes, based on which the structure of biology is built. Inorganic nanowires/nanoribbons with a similar one-dimensional topology but much simpler structures can hardly be as flexible as macromolecules when constructing superlattice structures because of their inherent rigidity. Here we report the synthesis of crystalline indium sulfide nanoribbon-based nanocoils that are formed by spontaneous self-coiling of ultrathin nanoribbons. The nanostructures are flexible and appear as relatively random coils because of their ultrathin ribbon structures (~0.9 nm in thickness) with high aspect ratios. Moreover, the nanocoils can self-adjust their shapes and assemble into two-dimensional superlattices and three-dimensional supercrystals in solution. The ultrathin nanocoils are expected to bring new insights into the use of flexible nanocrystals as building blocks for constructing superstructures.

Hydrogen Bond Nanoscale Networks Showing Switchable Transport Performance

Hydrogen bond is a typical noncovalent bond with its strength only one-tenth of a general covalent bond. Because of its easiness to fracture and re-formation, materials based on hydrogen bonds can enable a reversible behavior in their assembly and other properties, which supplies advantages in fabrication and recyclability. In this paper, hydrogen bond nanoscale networks have been utilized to separate water and oil in macroscale. This is realized upon using nanowire macro-membranes with pore sizes ~tens of nanometers, which can form hydrogen bonds with the water molecules on the surfaces. It is also found that the gradual replacement of the water by ethanol molecules can endow this film tunable transport properties. It is proposed that a hydrogen bond network in the membrane is responsible for this switching effect. Significant application potential is demonstrated by the successful separation of oil and water, especially in the emulsion forms.

Multivalent assembly of ultrasmall nanoparticles: One-, two-, and three-dimensional architectures of 2 nm gold nanoparticles

AbstractThe assembly of nanoparticles (NPs) into complex structures is a fundamental topic in nanochemistry. Although progress has been made in this respect, the classical treatment of NPs as hard building blocks that lack the ability to anisotropically “bond” to each other limits the construction of more complex assemblies. More importantly, extension of methods of assembly of robust NPs to the assembly of ultrasmall ones with size below 2 nm is still challenging. Here we report the controlled self-assembly of ∼2 nm gold NPs into one-dimensional (1D) nanochain, two-dimensional (2D) nanobelt and three-dimensional (3D) nanocomet architectures by kinetically controlling the diffusion of ultrasmall gold NPs with anisotropic surfaces in solution. This process is presumed to allow selective ligand exchange with linkers at different binding sites on the NP surface, and results in “multivalent” interactions between NPs. Different from the assembly of “hard building blocks”, our results demonstrate the significance of surface effects for ultrasmall NPs (or clusters) in determining the structure of complex self-assemblies, and suggest the possibility of assembling these “molecule-like” ultrasmall nanocrystals into novel complex materials on a nanoscale approaching that of real atoms or molecules.