Thuy-Duong Nguyen-Phan

Synthesis of hierarchical rose bridal bouquet- and humming-top-like TiO2 nanostructures and their shape-dependent degradation efficiency of dye

Novel hierarchical rose bridal bouquet- and humming-top-like nanostructured TiO(2) were successfully prepared by the simple process with the hydrothermal temperature as the morphology-controlling factor. The gradual transformation from layered titanate to brookite phase was well consistent with the formation mechanism of the hierarchical morphologies. The three-dimensional flower bouquets built from the bunches of roses with surrounding fern fronds displayed the best adsorptivity and completely degraded methylene blue within 60 min under UV irradiation, whereas the humming-top geometry composed of anisotropically elongated spindle-like crystallites was detrimental to the dye photodegradation.

Uniform distribution of TiO2 nanocrystals on reduced graphene oxide sheets by the chelating ligands

Reduced graphene oxide-TiO(2) hybrids were successfully prepared by the hydrothermal approach using triethanolamine and acetylacetone as the chelating agents. Without any additive, large aggregated TiO(2) clusters were randomly distributed dominantly at the edge and less on the basil plane of coagulated reduced graphene oxide (RGO) layers. The presence of chelating ligands remarkably facilitated the selective growth and regular spread of TiO(2) nanocrystals onto individually exfoliated RGO sheet. Such sandwich-like structure with stronger coupling and chemical interaction resulted in the surface area increase, the rearrangement of energy level, the enhanced concentration of oxygen vacancies, leading to much higher adsorbability and photocatalytic degradation of Rhodamine B under both UV and visible irradiations. These RGO-TiO(2) hybrid systems are potentially beneficial for widely practical applications in air/water purification, electronic devices, batteries, solar cells or supercapacitors.

Mesoporous titanosilicate/reduced graphene oxide composites: layered structure, high surface-to-volume ratio, doping effect and application in dye removal from water

In this study, a new system of integrated photocatalytic adsorbents (IPCAs), three-dimensional wormhole-like mesoporous titanosilicate/reduced graphene oxide layered composites, were prepared with various Ti/Si ratios. The reduced graphene oxide (RGO) nanosheets played the role of giant two-dimensional (2D) platforms for the deposition, spreading and growth of mesostructured layers, leading to a significant enhancement in mesoporosity. The substitution of titanium species into the mesoporous silica/RGO significantly changed the textural, physicochemical and optical properties. Gradually increasing the Ti doping content dramatically promoted the adsorptivity and UV-photocatalytic degradation of the dye contaminant; however, an excess dosage (20 mol%) inhibited the UV activity. This could be attributed to the changes in the coordination geometry and electronic states of Ti species in the composites. The IPCAs that dominantly contained highly dispersed and isolated Ti-oxide species in tetrahedral coordination within a mesostructured framework exhibited much higher photoactivity than those composed of aggregated and octahedrally coordinated Ti species due to the formation of efficient charge-transfer excited states.

Nitrogen-doped mesoporous reduced graphene oxide for high-performance supercapacitors

We report a simple method to prepare N-doped mesoporous reduced graphene oxide (RGO) via the pyrolysis of poly (methyl methacrylate)–graphene oxide (PMMA–GO) and PMMA–RGO composites in a mixed nitrogen and ammoniac atmosphere. The pyrolysis of the PMMA–GO resulted in a heavily nitrogen-doped RGO aerogel with a nitrogen content of more than 5.0 at%, whereas crumpled RGO with a surface area of up to 766 m2 g−1 was obtained by the pyrolysis of PMMA–RGO. A supercapacitor based on the N-doped mesoporous RGOs exhibited an excellent specific capacitance of up to 290 F g−1 at a current density of 1 A g−1 and good electrochemical stability with a capacitance retention of about 85% after 1000 cycles. Moreover, by using an ionic liquid as an electrolyte within a potential range of 0–4 V, a remarkable energy density of up to 149 W h kg−1 was achieved.

Removal efficiency of gaseous benzene using lanthanide-doped mesoporous titania.

The adsorptive removal of benzene from cerium- and lanthanum-doped mesoporous TiO2 adsorbents was performed in a continuous-flow, fixed-bed reactor. The influences of lanthanide content and adsorption temperature were investigated. The adsorption efficiency of benzene was remarkably promoted in the presence of lanthanide. The adsorption capacity for benzene increased with lanthanide dosage, which was attributed to the enhancement in a specific surface area. It was determined that 5 mol% rare earth metal was the optimal amount for the highest benzene-adsorption, irrespective of adsorption temperature. Furthermore, the drastic reduction of adsorption capacities at higher temperature implied that benzene molecules were weakly adsorbed to the adsorbents. Additionally, X-ray photoelectron spectroscopy showed a correlation between the adsorption behavior and the chemical properties of mesostructure materials, typically the interaction of surface hydroxyl groups and the pi-electron of benzene, and the formation of sigma-bonding and d-pi* back-donation between the adsorbent and gaseous adsorbate.

Adsorption of benzene onto mesoporous silicates modified by titanium

Mesoporous molecular sieve SBA-15 modified by titanium has been utilized for removing organic pollutants, such as benzene, from air. Titanium was impregnated inside SBA-15 by wetness impregnation after synthesis of SBA-15 (impregnation method) or was doped into the SBA-15 framework by the direct addition of Ti precursor into the sol during synthesis (doping method). In the breakthrough curves for gas-phase benzene adsorption, Ti addition into SBA-15 resulted in the enhancement of benzene adsorption capacity, depending on Ti loading amounts. An increase in adsorption temperature remarkably reduced the benzene adsorption capacity, indicating that the interaction between benzene and the materials was weak.

Facile microwave-assisted synthesis and controllable architecture of three-dimensional nickel titanate

A rapid, facile, one-pot microwave-assisted polyol synthesis of novel hierarchical nickel titanate (NTN) is first reported in the present study. This method successfully fabricated rhombohedral NiTiO3 in the shape of a cylindrical storage tank with two elliptical end caps that were constructed from ellipsoid-like nanoparticles. By contrast, irregular NTN aggregates composed of loose granular particles were formed through solvothermal treatment. Varying the dielectric of the solvent with water, n-butanol, acrylic acid, N,N-dimethylformamide, and an ethylene glycol : butanol mixture significantly affected the crystallographic structure and morphology of the final products due to differences in the loss tangent of each medium under microwave irradiation. Using a nickel source with acetate and halide counterions, which are more readily substituted and have better coordination ability with metal cations than nitrate, resulted in the formation of 3D hexagonal prismatic NiTiO3 and undesirable 1D rod-like TiO2 aggregates, respectively. Notably, this study provides a valuable means of developing a rapid, effective method to synthesize NiTiO3 with uniform morphology, high purity and potential photocatalysis application.