Local structure of titania decorated double-walled carbon nanotube characterized by scanning transmission X-ray microscopy

Superior shuttling of lithium and sodium ions in manganese-doped titania @ functionalized multiwall carbon nanotube anodes

In order to improve the electrochemical kinetics of anatase titania (TiO₂), Mn-doped TiO₂ incorporated with functionalized multiwall carbon nanotubes (MWCNTs) has been prepared by a modified hydrothermal method and tested for both lithium (LIB) and sodium-ion battery (SIB) anodes. The size of the TiO₂ particles is controlled to ∼35-40 nm, with almost even distribution on the MWCNTs surface. The nanostructuring and appropriate doping of cost-effective manganese into the TiO₂ host improved the electrochemical performance in terms of high rate capability and specific capacity for both the rechargeable battery systems. For the LIBs, the charge capacity of the 5% Mn-TiO₂/MWCNT anode is 226.3 mA h g^-1 in the first cycle, and is retained at 176.4 mA h g^-1 after 80 cycles as compared with the SIBs, in which the charge capacity is 152.1 mA h g^-1 in the first cycle, and is retained at 121.4 mA h g^-1 after 80 cycles. After testing the electrodes at a high current rate of 20C, the nanocomposite electrode can still demonstrate charge capacities of 131.2 and 117.2 mA h g^-1 at a 0.1C rate for LIBs and SIBs, respectively. The incorporation of Mn-ions (2+, 4+) is found to play a crucial role in terms of defects and vacancy creation, increasing conduction band electrons and lattice expansion to facilitate alkali metal ion diffusion for superior electrochemical performance. The combination of heteroatom doping and use of a highly conductive additive in the form of MWCNTs has resulted in excellent electrode integrity, high ion accessibility, and fast electron transport. Its outstanding cycling stability and remarkable rate performance make the 5% Mn-TiO₂/MWCNT a promising anode material for high-performance LIBs and SIBs.

Soft X-ray spectromicroscopy for speciation, quantitation and nano-eco-toxicology of nanomaterials

There is a critical need for methods that provide simultaneous detection, identification, quantitation and visualization of nanomaterials at their interface with biological and environmental systems. The approach should allow speciation as well as elemental analysis. Using the intrinsic X-ray absorption properties, soft X-ray scanning transmission X-ray spectromicroscopy (STXM) allows characterization and imaging of a broad range of nanomaterials, including metals, oxides and organic materials, and at the same time is able to provide detailed mapping of biological components. Thus, STXM offers considerable potential for application to research on nanomaterials in biology and the environment. The potential and limitations of STXM in this context are discussed using a range of examples, focusing on the interaction of nanomaterials with microbial cells, biofilms and extracellular polymers. The studies outlined include speciation and mapping of metal-containing nanomaterials (Ti, Ni, Cu) and carbon-based nanomaterials (multiwalled carbon nanotubes, C60 fullerene). The benefits of X-ray fluorescence detection in soft X-ray STXM are illustrated with a study of low levels of Ni in a natural river biofilm.