Han Jia

Controlled synthesis of α-Fe2O3 nanostructures with the assistance of ionic liquid and their distinct photocatalytic performance under visible-light irradiation

Well-dispersed α-Fe2O3 nanostructures with controlled dimensionality and shape have been successfully prepared via a facile and environmentally friendly solvothermal route with the assistance of 1-N-butyl-3-methylimidazolium benzoate ([Bmim][PhCOO]). A significant advancement has been made in tailoring dendritic α-Fe2O3 nanostructures along {110} directions. The dendrites can be tailored to hexagonal plates and rods only by changing the molar ratio of [Bmim][PhCOO] to K3[Fe(CN)6] from 0 : 1 to 2 : 1, and 5 : 1. [Bmim][PhCOO] is found to play a key role in the evolution of α-Fe2O3 with different shapes: the nucleation rate is influenced by the hydrolysis of [PhCOO]− anions, and the [Bmim]+ cations can favorably stabilize the {110} facets due to the hydrogen bond-co-π–π stacking interaction. A possible mechanism was proposed. Furthermore, the visible light induced photodegradation of RhB reveals that α-Fe2O3 rods exhibit higher photocatalytic activity compared to dendrites and plates. Interestingly, with the process proceeding, the photoactivity of these samples increases successively. The enhancement of photocatalytic performance may be due to the different exposed crystal facets of α-Fe2O3 nanostructures and the degree of crystallinity. The tailoring process gives us an in-depth understanding of the formation mechanism of dendritic α-Fe2O3 structures, which is not possibly achieved by the traditional time-dependent method, and it is highly expected that this study will suggest a promising new strategy for engineering practical photocatalysts for wastewater treatment.

Facile construction of gemini-like surfactants at the interface and their effects on the interfacial tension of a water/model oil system

The application of supramolecular chemistry may be a promising and convenient approach to construct desired surfactants via noncovalent interactions in various fields, including chemical enhanced oil recovery (EOR). Gemini-like surfactants were fabricated by combining sodium dodecyl benzene sulfonate (SDBS) and butane-1,4-bis(methylimidazolium bromide) (BBMB) at the interface and evaluated for their ability to reduce the interfacial tension (IFT) between water and a model oil (toluene and n-decane, v/v = 1 : 1). The SDBS/BBMB molar ratio at the interface, but not in the bulk phase, was the crucial factor in the construction of gemini-like surfactants and the reduced level of IFT. Based on the synergistic effect between electrostatic attraction and other intermolecular or intramolecular interactions (π–π stacking and hydrophobic interaction), the formation mechanism of gemini-like surfactants was proposed. The effects of temperature and salinity on the IFT were systematically investigated. Moreover, the (SDBS)2/BBMB gemini-like surfactant system showed the desired ability to reduce the IFT of water/crude oil and a great improvement in crude oil recovery.

Facile one-step preparation of hierarchical α-Fe2O3 nanostructures with enhanced performance in energy and environmentally related applications

Hierarchical α-Fe2O3 nanostructures have been successfully synthesized in aqueous solution of sodium dodecyl sulfonate (SDS), 1-dodecyl-3-methylimidazolium bromide (C12mimBr) and ethylene glycol (EG) on the basis of a polyol process. Based on a series of experiments, the possible growth mechanism and fabrication process of the hierarchical structures were proposed. The addition of EG and utilizing Fe2+ ions as the source of iron were our “protection” reactions to guarantee the equilibrium between hydrolysis and oxidation of Fe3+. Furthermore, electrochemical measurements demonstrated that the as-prepared hierarchical α-Fe2O3 nanocrystals are ideal candidates for lithium-ion batteries. In addition, the photocatalytic activity of the as-prepared α-Fe2O3 was superior to that of the previously reported hierarchical α-Fe2O3 nanomaterials and the Fe2O3-based photocatalyst (α-Fe2O3/SnO2).

Effects of additional salts on the interfacial tension of crude oil/zwitterionic gemini surfactant solutions

Abstract Zwitterionic gemini surfactants, which have the advantages of both zwitterionic and gemini surfactants, have been widely used in various disciplines. Sulfobetaine-type zwitterionic gemini surfactants consisting of 1,2-bis[N-methyl-N-(3-sulfopropyl)-alkylammonium]ethane (2CnSb with 6, 8 and 10 carbon atoms) were evaluated for their interfacial activities at the water/crude oil interface. The 2C10Sb molecules showed a remarkable ability to decrease the interface tension (IFT) of water/crude oil, and the degree of decrease was much greater than those in either zwitterionic or gemini surfactant systems by at least two orders of magnitude. Furthermore, the effects of salts (NaCl, CaCl2, and MgCl2) on the IFT of the 2C10Sb system were thoroughly investigated. Interestingly, the delicate balance between the effects of additional cations and the intramolecular interactions of 2C10Sb molecules played crucial roles in the interfacial arrangements of 2C10Sb molecules, which were mainly dependent on the bonding abilities of the cations. Moreover, a zwitterionic surfactant and a cationic gemini surfactant were employed in control experiments to verify the proposed mechanisms. GRAPHICAL ABSTRACT

Controlled synthesis of gold nanorings with structural defects assisted by elastic induction of mixed surfactants

Controlled synthesis of gold nanorings was realized by reducing chloroauric acid in aqueous mixed solutions of cetyltrimethyl ammonium bromide (CTAB) and sodium dodecyl sulfate (SDS). It is revealed that the gold nanowires are induced to fabricate the gold nanorings with an average diameter of ~300 nm. The synthesis of the nanowires and the formation of the nanorings can be achieved in one step. A variety of gold nanostructures, such as short nanowires, nanorings, nanostars with a number of soft protuberances and nanopolyhedra, could be readily obtained by simply changing the CTAB/SDS molar ratio. Both the “structural defects” and the “elastic induction”, which are closely related to the mixed bilayers (CTAB/SDS), are indispensable for the final formation of the gold nanorings. Four surfactants with similar structures were also used to further verify the formation mechanism.