Zhenquan Tan

Fullerene Fine Crystals with Unique Shapes and Controlled Size

The preparation of fullerene fine crystals with uniform size and shape would permit the control of their specific electronic energy levels and the fabrication of materials with completely new properties. To this end, we have successfully fabricated, for the first time, shape- and size-controlled C60 fine crystals using a reprecipitation method developed in our laboratory. The C60 fine crystals obtained were clearly monodisperse and came in an interesting diversity of shapes such as spherical, rodlike, fibrous, disk, and octahedral. We were able to selectively control these sizes and shapes by simply changing the combination of solvents used and the reprecipitation conditions.

Multibranched C60 Micro/Nanocrystals Fabricated by Reprecipitation Method

We found that monodispersed C60 micro/nanocrystals (M/NCs) with unique multibranched structures can be fabricated by reprecipitation method, using m-xylene and 2-propanol as good and poor solvents, respectively. The resulting C60 M/NCs had a hexagonal crystal structure and was found to be a kind of crystal solvates in which the molar ratio of C60 to m-xylene was 3:2. C60 M/NCs seem to be important nanoparts in an integrated device.

Arrangement of palladium nanoparticles templated by supramolecular self-assembly of SDS wrapped on single-walled carbon nanotubes

We report a facile route to selectively deposit and arrange palladium (Pd) nanoparticles on single-walled carbon nanotubes (SWCNTs) having sub 10 nm diameter by using supramolecular self-assembly of sodium dodecyl sulfate (SDS) as a soft template.

Supramolecular Hydrogel of Bile Salts Triggered by Single‐Walled Carbon Nanotubes

IO N Supramolecular self-assembly is a branch of smart chemistry that focuses on chemical systems made up of a discrete number of assembled molecular subunits or components. [ 1 ] It has been applied to carbon nanotubes (CNTs) for the development of new materials and molecular systems. [ 2 ] Many organic surfactants are reported to form supramolecular self-assemblies on the surface of CNTs when the concentration is higher than the critical micelle concentration (CMC). [ 3 ] This phenomenon is generally used to disperse CNTs in water and to change the surface physical/chemical behavior of CNTs. Here, we report the synthesis of a supramolecular hydrogel based on singlewalled carbon nanotubes (SWCNTs) triggered by a bile salt biosurfactant, sodium deoxycholate (NaDC). We found that this supramolecular hydrogel had excellent viscoelastic properties. The shearing modulus was found to be ≈ 2 × 10 5 Pa over the shear stress range from 1 to 1000 Pa, and the dynamic elastic modulus ( G ′) and viscous modulus ( G ′′) were 10 5 Pa and 10 4 Pa, respectively, at 20 ° C. We prepared nanowires and nanopatterns by a direct print method that using the hydrogel as a “solid” ink. The electrical conductivity ( σ ) of such nanowire was ≈ 55 S cm − 1 . It suggests that the hydrogel is a suitable material to construct SWCNT-based devices by the top-down process. The supramolecular hydrogel has the potential for use in rheological materials [ 4 ] and fl exible, stretchable electronics applications. [ 5 ] NaDC is a bile salts that is an anionic biological surfactant widely used in biomedicine. NaDC is a surfactant often used to dissolve and stabilize individual SWCNTs in water. [ 6 ] The stabilization mechanism can be explained by the adsorption of NaDC molecules onto the surface of SWCNTs driven by the hydrophobic interaction. NaDC has a large, rigid, and planar hydrophobic moiety consisting of a steroid nucleus with two hydroxyl groups. This unique structure helps NaDC molecules adsorb stably onto the surfaces of SWCNTs through hydrophobic interactions, resulting in the dissolution and dispersion of SWCNTs in water. However, NaDC exhibits a rich and complex phase behavior in aqueous solution because of its unique molecular structure. It forms primary micelles with a small size of 1 nm at a CMC of 0.05% and forms secondary micelles (large rod-like self-assemblies) at a CMC of 0.1%. [ 7 ] The secondary self-assembly can be phase transformed into hydrated nanotubes and hexagonal liquid crystals

Raman scattering of linear chains of strongly coupled Ag nanoparticles on SWCNTs

We compare the Raman scattering properties of hybrid nanostructures consisting of Ag nanoparticles (NPs) in disordered and aligned arrangements on single-walled carbon nanotubes (SWCNTs) as a result of chemical and photoreduction methods. In the latter case, the unique structure of the very small Ag NP (from 4 to 7 nm) chains generated an extremely large mode at 969 cm−1 that was assigned to the sulphate-silver interaction at the NP surface. Another strong mode was present at 1201 cm−1 and was assigned to an IR-active mode of sodium dodecyl sulphate (SDS); this mode was observed because the symmetry changes altered the selection rules. We demonstrate that both the UV photoreduction of silver and the presence of SWCNTs are necessary to produce this very strong Raman scattering. The Raman modes of the SWCNTs are also significantly modified by the presence of Ag NP chains along the nanotubes.

Particle size for photocatalytic activity of anatase TiO2 nanosheets with highly exposed {001} facets

Size-controllable TiO2 nanosheets with highly exposed {001} facets were synthesized by a hydrothermal method. The particle sizes ranged from 25 nm to submicrometres by carefully adjusting the F/Ti molar ratio. TiO2 nanosheets smaller than 100 nm have higher photocatalytic activity and are highly stable in degradation of organic dyes.

Ordered deposition of Pd nanoparticles on sodium dodecyl sulfate-functionalized single-walled carbon nanotubes

We report here a novel chemical solution method to site-selectively deposit and arrange palladium (Pd) nanoparticles (NPs) on single-walled carbon nanotubes (SWCNTs). Sodium dodecyl sulfate (SDS) formed supramolecular self-assemblies on the SWCNTs. The SDS then acted as adsorption sites for Pd(II) ions. Pd(II) was reduced to Pd NPs by photo-reduction, and the NPs formed helices with different helix angles on the surface of the SWCNTs. The pitch of the Pd NPs helix was 4.5 nm. The parameters of the Pd NPs helix (pitch, angle, and chirality) were determined by the supramolecular self-assembly of SDS on the SWCNTs. Increasing the concentration of Pd(II) ions resulted in high-density deposition of Pd NPs on the SDS-functionalized SWCNTs.

Oriented growth behavior of Ag nanoparticles using SDS as a shape director.

We report a chemical approach for synthesizing shape-controlled Ag nanoparticles by using the surfactant SDS as a soft template. The experimental approach includes a two-step reaction: the first step is quickly generating Ag seed clusters by a chemical reaction using sodium borohydride as a reducing reagent; the second is the slow growth of controllable Ag nanoparticles by a mild chemical reaction using hydroxylamine hydrochloride as a reducing reagent. Spherical, polyhedral, and fibrous Ag nanoparticles are synthesized successfully in aqueous solution having SDS concentrations of 0.01, 0.02, and 0.2 wt.%, respectively. Size, morphology, and dispersion stability of these Ag nanoparticles depend on the concentrations of both SDS and AgNO(3).

Synthesis and processing of graphene hydrogels for electronics applications

Synthesis of a graphene hydrogel, in which the elastic modulus can be changed from ∼10 to ∼105 Pa and the electrical conductivity can be controlled in a range from ∼0.01 to ∼6 S cm−1 by carefully adjusting the graphene content, allowing for direct processing and patterning of graphene for many electrical applications.

INTERSTELLAR ANALOGS FROM DEFECTIVE CARBON NANOSTRUCTURES ACCOUNT FOR INTERSTELLAR EXTINCTION

Because interstellar dust is closely related to the evolution of matter in the galactic environment and many other astrophysical phenomena, the laboratory synthesis of interstellar dust analogs has received significant attention over the past decade. To simulate the ultraviolet (UV) interstellar extinction feature at 217.5 nm originating from carbonaceous interstellar dust, many reports focused on the UV absorption properties of laboratory-synthesized interstellar dust analogs. However, no general relation has been established between UV interstellar extinction and artificial interstellar dust analogs. Here, we show that defective carbon nanostructures prepared by high-energy collisions exhibit a UV absorption feature at 220 nm which we suggest accounts for the UV interstellar extinction at 217.5 nm. The morphology of some carbon nanostructures is similar to that of nanocarbons discovered in the Allende meteorite. The similarity between the absorption feature of the defective carbon nanostructures and UV interstellar extinction indicates a strong correlation between the defective carbon nanostructures and interstellar dust.