Zhelong Jiang

Titanate and titania nanostructured materials for environmental and energy applications: a review

Nanosized TiO2-based materials with unique structural and functional properties have already led to breakthroughs in various applications including photocatalysis, adsorption, lithium-ion batteries, etc. In this review, we present the state-of-the-art development of fabrication strategies of titanate/titania nanostructures and their corresponding environmental and energy applications. First, the structural features of titanate and titania and their correlation are explained in great detail. After which, recent research efforts on the development of multi-dimensional titanate materials are summarized. Following that, the applications of titanate/titania nanomaterials in the fields of adsorbents, photocatalysis, lithium-ion batteries, photovoltaics, electrochromic devices, self-cleaning and oil–water separation are reviewed. Finally, the future perspectives for the nanostructured titanate and titania are discussed. Continuous development in this area is essential to endow TiO2-based materials with advanced functionality and improved performance for practical applications.

Synthesis of Nanostructured Silver/Silver Halides on Titanate Surfaces and Their Visible-Light Photocatalytic Performance

Dense and uniform silver halides AgX (X = Cl, Br, I) nanoparticles were successfully fabricated on layered titanate nanowired honeycomb (TNHC) thin films. The growth of AgX nanocrystals was carried out through two steps. Firstly, ion-exchange was employed to incorporate Ag(+) ions into the interlayer of the titanate nanowires. Secondly, hydrogen halide (HX) solution was rapidly injected onto the ion-exchanged silver TNHC surface to generate nanosized AgX particles on TNHC films. The effect of the reaction time, solution pH, and concentration of halide anions on the morphology of the AgX photocatalysts has been studied. Followed by light-irradiation, the optimized Ag/AgX thin films exhibited excellent degradation performance under visible light because of localized surface plasmon resonance effect.

Specific surface area of titanium dioxide (TiO2) particles influences cyto- and photo-toxicity

The aim of this study is to examine how different specific surface areas of similar-sized titanium dioxide (TiO(2)) particles could influence both cytotoxicity and phototoxicity. TiO(2) particles of different specific surface areas were compared for their toxic effects on RAW264.7 cells in the absence and presence of UV light. From the results, TiO(2) particles with larger specific surface area were found to induce higher cyto- (UV absent) and photo-toxicity (UV activated) to cells after 24h incubation. The observed cytotoxicity from TiO(2) particles with larger surface area could be explained from their interactions with biomolecules. Upon photoactivation, a larger number of hydroxyl radicals were detected from TiO(2) particles with larger surface area, again suggesting a surface area dependent phototoxic effect. On the other hand, pre-adsorbing TiO(2) particles with extracellular proteins were found to decrease toxicity effects.

In situ identification of kinetic factors that expedite inorganic crystal formation and discovery

Navigating the kinetic landscape is a key to reaching complex inorganic phases efficiently. High-temperature treatment of elemental mixtures is the traditional method of solid-state syntheses, where thermodynamic driving forces are large, but success can be hampered by kinetic barriers. Successful inorganic crystal preparation relies on methods to either surmount such barriers, or direct the reaction to avoid them. Both approaches were utilized in our synthetic investigation with in situ X-ray diffraction (XRD) using Fe2SiS4 as the target compound. In this system, Si sulfidation is the limiting factor preventing thermodynamic Fe2SiS4 crystal formation. Through in situ XRD reaction maps, we established that superheated S liquid from the FeS2 peritectic at 743 °C was responsible for the onset of rapid Fe2SiS4 formation. Alternatively, by pre-reacting Si with Fe, we directed the chemical system via intermediate states that expedited Fe2SiS4 formation at temperatures as low as 550 °C. The utilization of these kinetic expediting factors, and those that can be uncovered by similar methods, can improve the potential of the solid state method for creating new materials and refining chemical syntheses.

Dynamic Gradient Directed Molecular Transport and Concentration in Hydrogel Films

Materials which selectively transport molecules along defined paths offer new opportunities for concentrating, processing and sensing chemical and biological agents. Here, we present the use of traveling ionic waves to drive molecular transport and concentration of hydrophilic molecules entrained within a hydrogel. The traveling ionic wave is triggered by the spatially localized introduction of ions, which through a dissipative ion exchange process, converts quaternary ammonium groups in the hydrogel from hydrophilic to hydrophobic. Through a reaction-diffusion process, the hydrophobic region expands with a sharp transition at the leading edge; it is this sharp gradient in hydrophilicity that drives the transport of hydrophilic molecules dispersed within the film. The traveling wave moved up to 450 μm within 30 min, while the gradient length remained 20 μm over this time. As an example of the potential of molecular concentration using this approach, a 70-fold concentration of a hydrophilic dye was demonstrated.

Identification of kinetic factors that expedite solid-state Fe2SiS4 crystal formation by in situ XRD

Understanding of the kinetic factors on complex crystal formation is beneficial to the efficient synthesis and discovery of inorganic materials. Here we utilized high-temperature in situ X-ray diffraction (XRD) to identify such kinetic factors in the formation of the model compound Fe2SiS4 during solid state reactions. It is observed from in situ XRD that the sulfidation kinetics differ drastically among the Fe and Si elements. The ability of this system to achieve thermodynamic equilibrium phase at low temperature is likely impeded by the slow sulfidation of Si. Here, from in situ XRD, we identified two factors that expedited the solid state reaction in forming Fe2SiS4 phase. The first factor is associated with the peritectic point of Fe-S system at 743 °C, which generated superheated S liquid and initiated fast Fe2SiS4 growth. The second factor involved the pre-bonding of Fe and Si to form intermetallics, whose subsequent sulfidation can generate Fe2SiS4 at temperatures as low as 550 °C. We expect the utilization of these two kinetic factors uncovered by in situ XRD can improve the synthesis of complex chalcogenides using solid state method, especially in those involving slowly-sulfidized elements.

Correction: Titanate and titania nanostructured materials for environmental and energy applications: a review

Correction for ‘Titanate and titania nanostructured materials for environmental and energy applications: a review’ by Yanyan Zhang et al., RSC Adv., 2015, 5, 79479–79510.