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165. An ion exchange approach assembled multi-dimensional hierarchical Fe–TiO2composite micro-/nano multi-shell hollow spheres for bacteria lysis through utilizing visible lightElectronic supplementary information (ESI) available. See DOI: 10.1039/c8cy00078f

Author

Ang, Jeremy Koon Keong, Chua, Jestoni Song Mi, Chang, Zhong Jie, Li, Zhengtao, Bai, Hongwei, and Sun, Darren D.

Abstract

The ion exchange approach demonstrates the fabrication of the hierarchical, multi-shell, micro-/nano, Fe–TiO2composite hollow spheres (HMS). The synthesis mechanism elucidates a novel technique to achieve a Fe–TiO2composite multi-shell structure by first allowing Fe ions to penetrate the pores of carbonaceous spheres at room temperature. This is followed by ion exchange in a solvothermal treatment. Lastly, the outward diffusion of the Fe ions allows the inward diffusion of Ti ions to fill the voids created within the pores of the carbonaceous spheres and simultaneously form hierarchical thorns. The ion exchange enabled a deeper penetration of Ti ions into the pores of the carbonaceous spheres. The oxidization of the carbonaceous spheres leads to the convergence of deeply penetrated Ti–Fe ions which crystallize to form Fe–TiO2composite multi-shell spheres. The HMS spheres revealed an agglomeration of 20 nm nanoparticulates and a uniform dispersion of Fe–TiO2composite. Increasing the Fe ion penetration duration from 6 h up to 48 h was found to gradually reduce the band gap from 3.1 eV to approximately 2.7 eV. The synthesis mechanism elucidates the compaction of metal ions within the pores of the carbonaceous spheres which leads to a smoother inner sphere morphology and, consequently, the reduction in the mesopores diameter from 15 nm to 4 nm. The HMS demonstrate an enhanced physical lysis of 40% bacteria under dark conditions owing to the hierarchical thorn-like structure and an enhanced bactericidal capability to 70% under the irradiation of visible light over a period of 1 h. The initial physical lysis by the hierarchical thorn surface to the cell and the subsequent release of reactive oxygen species to degrade the ruptured bacteria wall or access the RNA/DNA led to further cell death.

Published
2018
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172. Inherent porous structure modified by titanium dioxide nanoparticle incorporation and effect on the fouling behavior of hybrid poly(vinylidene fluoride) membranes.

Author

Younas, Hassan, Shao, Jiahui, Bai, Hongwei, Liu, Liyan, and He, Yiliang

Subjects
POROUS materials, MOLECULAR structure, TITANIUM dioxide nanoparticles, FOULING, POLYVINYLIDENE fluoride, ARTIFICIAL membranes
Abstract

ABSTRACT The incorporation of nanoparticles (NPs) into a casting solution is a widely used practice for controlling the membrane fouling tendency, but the specific role of NPs in fouling control from an internal porous structure optimization has seldom been investigated. In this study, we evaluated the specific role of titanium dioxide (TiO2)-NPs (Degussa P25) in mitigating membrane organic fouling. We prepared the membranes by tailoring the concentrations of the NPs well; this resulted in an optimized membrane microstructure consisting of fingerlike voids (beneath the skin layer of the membrane) and spongy voids (adjacent to the fingerlike voids). The NP incorporation induced the formation of spongy voids beneath the skin layer, and the increase in the NP concentration increased the formation of spongy voids. Moreover, surface images obtained by scanning electron microscopy, X-ray photoelectron spectroscopy results, and contact angles confirmed that TiO2-NPs were almost absent on the skin layer. Antifouling experiments were performed with a model organic foulant in two flow orientations [fingerlike voids facing the retentate (FVR) and spongy voids facing the retentate (SVR)]. The results show that the membrane fluxes in FVR decreased more than those in SVR. The membrane with 1.5 wt % TiO2 operated in SVR exhibited the lowest flux decline; this suggested that spongy voids with TiO2 exposure could mitigate fouling to a greater extent. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43265. [ABSTRACT FROM AUTHOR]

Published
2016
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174. Three-Tier Hierarchical Clusters of Carbon-Coated Li4Ti5O12 Single Crystals as High-Power and High-Energy Anodes for Lithium-Ion Batteries.

Author

Bai, Hongwei, Zan, Xiaoli, Liu, Zhaoyang, and Sun, Darren Delai

Subjects
LITHIUM-ion batteries, ELECTROCHEMICAL electrodes, CONDUCTIVITY of electrolytes, SINGLE crystals, CRYSTALLOGRAPHY
Abstract

A novel three-tier hierarchical cluster lithium-ion battery (LIB) anode is reported here, consisting of 1) carbon-coated Li4Ti5O12 crystals as the first nano-tier (ca. 10 nm) for high-rate capability; 2) submicron spheres consisting of Li4Ti5O12 crystals as the second submicron tier (100-300 nm), facilitating electrolyte infiltration and Li+ diffusion; and 3) clusters comprising Li4Ti5O12 spheres as the third micron-sized tier (1-2 μm) to increase the packing density of active materials for high-power LIBs. The submicron tier acts as a transition zone between the nano-tier and micro-tier to further benefit Li+ diffusion, electrolyte infiltration, and electron transport. The carbon coating on Li4Ti5O12 forms a uniform and continuous conductive network for fast electron transport and Li+ diffusion to address the low electronic conductivity obstacle of the Li4Ti5O12 anode. The three-tier hierarchical clusters maximize the close contact between the electrolytes and the active materials for excellent electrochemical performance. [ABSTRACT FROM AUTHOR]

Published
2016
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