Zhihong Tang

Synthesis, optical and electrochemical properties of ZnO nanowires/graphene oxide heterostructures.

Large-scale vertically aligned ZnO nanowires with high crystal qualities were fabricated on thin graphene oxide films via a low temperature hydrothermal method. Room temperature photoluminescence results show that the ultraviolet emission of nanowires grown on graphene oxide films was greatly enhanced and the defect-related visible emission was suppressed, which can be attributed to the improved crystal quality and possible electron transfer between ZnO and graphene oxide. Electrochemical property measurement results demonstrated that the ZnO nanowires/graphene oxide have large integral area of cyclic voltammetry loop, indicating that such heterostructure is promising for application in supercapacitors.

Structure control of ultra-large graphene oxide sheets by the Langmuir–Blodgett method

As a unique type of soft building block, graphene oxide (GO) dispersions are easy to process to produce electronic devices. Developing methods to produce large sized GO with controllable structure is the key for these applications. Here, ultra-large graphene oxide (UL-GO) sheets (up to ∼100 μm in lateral size) were produced in aqueous media and deposited onto substrates with controllable structure, including flat, rippled, standing collapsed, folded, over folded, highly curved, and scrolled morphologies, via the Langmuir–Blodgett (L–B) technique. The MD simulations show that the GO becomes much softer than pristine graphene sheets due to the sp3-hybridization caused by oxygen containing functional groups and this is the reason why a series of distinct structures were observed. To demonstrate the fabrication of a transparent conductor, the close-packed flat UL-GO films on poly(ethylene terephthalate) (PET) were reduced with a low-temperature chemical reduction process in a hydriodic (HI) acid aqueous solution, achieving a sheet resistance as low as 8.1 kΩ/sq with 90% transparency.

One-step synthesis of hydrophobic-reduced graphene oxide and its oil/water separation performance

Graphene oxide (GO) was functionalized to form hydrophobic-reduced graphene oxide (rGO) by a one-step hydrothermal method, and oleylamine was used as both reductant and modifier of GO. X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, X-ray diffraction, Raman spectroscopy, and contact angle measurement were used to determine the successful functionalization and reduction of GO. Results indicated that the color of obtained sample was changed from yellow brown to black, and contact angle between water and the graphene paper was over 130°, which was close to the typical hydrophobic material of PTFE; at the same time, the functionalized rGO can be dispersed in some of the typical organic solvents, such as cyclohexane, chloroform, and benzene, proving that oleylamine was effective for the reduction and functionalization of GO. Based on the results, the possible reactions were proposed. Furthermore, the hydrophobic rGO was assembled to film by filtration, which demonstrated its efficient separation ability for oil/water.

Preparation of nanoporous carbons with hierarchical pore structure for CO2 capture

Abstract Nanoporous carbons with a hierarchical pore structure were prepared by a combination of hard-templating of a thermosetting phenolic resin containing silica nanoparticles, pyrolysis and KOH activation. The influence of the amount of KOH on the pore structure of the templated and activated carbons was investigated by N2 adsorption and the effect of pore structure on the CO2 adsorption capacity was investigated by thermogravimetric analysis. Results indicated that KOH activation promoted the formation of micropores and small mesopores for the templated carbon. The utilization ratio of mesopores for the capture of CO2 is high compared with that of micropores. The porous carbon prepared under a mass ratio of KOH to templated carbon of 2:1 has both developed mesopores and micropores, and has a largest adsorption capacity for CO2 among all samples investigated.

The comparison of macroporous ceramics fabricated through the protein direct foaming and sponge replica methods

The macroporous ceramic samples fabricated using the sponge replica and protein direct foaming methods were compared in terms of porosity, density, compressive strength and microstructure. The egg white protein was applied in both fabrication methods as the binder or foaming agent. The samples fabricated using the protein direct foaming method were stronger and more uniform pore structures in the similar porosity. This result was supported through the Weibull modulus analysis and the scanning electron microscope microstructure observation.

Controllable crumpling of N-doped graphene induced by capillary force resistance

Turning the 2D nanosheets into three-dimensional (3D) crumpled balls driven by the capillary force arising from water surface tension has proved to be an effective way to solve restacking. However, such a spherical form has a closed structure and the utilization of the inner surface is limited. Preparing crumpled graphene with an open structure, which can improve the utilization of the inner surface as well as maintain the excellent dispersion ability, is still a challenge. Herein, N-doped crumpled graphene (NCG) with controllable morphology and open structure is achieved by heating a microdroplet containing graphene oxide (GO) and urea; GO is the precursor of crumpled graphene and urea acts as both soft template to control the morphology of graphene and the nitrogen donor after template removal. u200bN-doped crumpled graphene (NCG) with controllable morphology and open structure is achieved by heating a microdroplet containing graphene oxide (GO) and urea; GO is the precursor of crumpled graphene and urea acts as both soft template to control the morphology of graphene and the nitrogen donor after template removal. During the drying process, GO diffuses on the liquid–vapor interface and urea is adsorbed on the surface of GO driven by its different diffusion rate and free energy reduction. Results indicate that when the mass ratio of urea to GO is less than 10, a completely crumpled ball is formed; an open structure is obtained at the mass ratio of 100; a semi-open NCG ball is collected when the mass ratio is 50. NCG with different morphologies shows different dispersibility and electrochemical performance. The NCG ball can be dispersed in almost all the selected solvents, semi-open and open NCG can be dispersed in the majority of solvents, but the open one precipitates faster than the semi-open NCG. Semi-open NCG demonstrates better electrochemical performance than that of the crumpled NCG ball and open NCG because of its higher effective surface area and suitable morphology.

Preparation of ordered mesoporous carbons with an intergrown p6mm and cubic Fd3m pore structure using a copolymer as a template

Ordered mesoporous carbons (OMCs) with an intergrown two-dimensional p6mm and three-dimensional Fd3m pore structure have been prepared by the carbonization of reverse copolymer-phenolic resin composites, which were themselves formed by a soft-template method by simply adjusting the ratios of ethanol and hexane. The microstructure of the OMCs was analyzed by small-angle X-ray scattering, nitrogen adsorption isotherms, and transmission electron microscopy. The results showed the structure of the OMCs obtained have the mesophase transition from p6mm to the intergrowth of p6mm/Fd3m and finally to Fd3m as the ratio of ethanol to hexane is changed.

Self-catalyzed synthesis of mesoporous carbons with tunable pore size and structure by soft-templating method

A series of mesoporous carbons (MCs) have been obtained through organic–organic self-assembly method by using phloroglucinol–formaldehyde as carbon precursor and a reverse amphiphilic triblock copolymer as a template. Because of its acidity, the phloroglucinol was used as a catalyst itself. Results show that the pore size and structure of MCs were tailored by simply tuning the weight content of formaldehyde while keeping other reactants constant. A cylindrical mesostructure was obtained when the weight content was 1.0, 1.2 and 1.4. Further increasing the weight content to 1.6 or 2.0, a three-dimensional cage-like mesostructure was obtained. Specific surface area and pore volume up to 485xa0m2/g and 0.78xa0cm3/g can be reached, respectively. In addition, the pore size can be tuned in the range of 4.9–14.8xa0nm by changing the content of formaldehyde.

Direct fabrication of ordered mesoporous carbons with super-micropore/small mesopore using mixed triblock copolymers.

Ordered mesoporous carbons (OMCs) have been prepared by the strategy of evaporation-induced organic-organic self-assembly method by employing a mixture of amphiphilic triblock copolymers poly(ethylene oxide)-b-poly(propylene oxide)-b-poly(ethylene oxide) (PEO-PPO-PEO) and reverse PPO-PEO-PPO as templates, with soluble in ethanol, low-molecular-weight phenolic resin as precursor, followed by carbonization. It has been found that the as prepared OMCs with porosity that combines super-micropore and small mesopore size distributed from 0.8 to 4 nm, which bridges the pore size from 2 to 3 nm and also for the diversification of the soft-templating synthesis of OMCs. Furthermore, the results showed that the OMCs obtained have mesophase transition from cylindrical p6 mm to centered rectangular c2 mm structure by simply tuning the ratio of PPO-PEO-PPO/PEO-PPO-PEO.