Double role of polyethylene glycol in the microwaves-assisted non-hydrolytic synthesis of nanometric TiO2: Oxygen source and stabilizing agent

The microwaves-assisted reaction between titanium(IV) tetrachloride and polyethylene glycol (PEG) represents a novel non-aqueous sol-gel route for synthesizing surface-stabilized titanium dioxide nanoparticles. X-ray powder diffraction measurements showed the exclusive presence of anatase phase. Transmission electron microscopy investigations revealed that the particles are nearly uniform in shape with sizes ranging from 4 to 8 nm and a low degree of agglomeration. The presence of covalently bonded PEG chains on the particles surface has been shown by Fourier transform infrared (FT-IR) spectroscopy. This surface functionalization greatly enhances the dispersibility of the particles in water, as observed by dynamic light scattering and zeta-potential analyses. Furthermore, the investigation of the reaction by-products by a combination of FT-IR and high-performance liquid chromatography (HPLC-Mass) techniques allowed a deeper insight into the reaction mechanism suggesting a double role of PEG as a stabilizing agent and an oxygen source. Graphical Abstract: [Figure not available: see fulltext.

Formation mechanism of LiFePO 4 sticks grown by a microwave-assisted liquid-phase process

A time-dependent study on the formation of LiFePO 4 with olivine-type structure is presented. The material is synthesized through a non-aqueous route in benzyl alcohol assisted by microwave radiation. The LiFePO 4 forms with an anisotropic morphology of microscale stick-like particles. The detailed structure of these particles and their evolution with reaction time is revealed by transmission electron microscopy; a 3D reconstruction of a particle by electron tomography provides insight into the formation mechanism of these sticks. Without applying a thermal post-annealing treatment or a carbon coating, the electrochemical behavior of the LiFePO 4 microsticks is assessed for the preparation of cathodes in lithium-ion batteries. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.D.C. thanks MICINN and Spanish Ministry of Education for a JdlC research contract and a >Jose Castillejo> Scholarship, respectively. M.D.R. and R.E. acknowledge the financial support of the Swiss COST office under the SBF project number C10.0089. Financial support by ETH Zurich and the Swiss National Science Foundation (Project No. 200021_124632) is gratefully acknowledged. We are thankful to Prof. Petr Novak, Paul Scherrer Institut, Switzerland, for providing us with the facilities to perform the electrochemical measurements.Peer Reviewe