Ultrasmall titania nanocrystals and their direct assembly into mesoporous structures showing fast lithium insertion.
Ultrasmall and highly soluble anatase nanoparticles were synthesized from TiCl(4) using tert-butyl alcohol as a new reaction medium. This synthetic protocol widens the scope of nonaqueous sol-gel methods to TiO(2) nanoparticles of around 3 nm with excellent dispersibility in ethanol and tert-butanol. Microwave heating was found to enhance the crystallinity of the nanoparticles and to drastically shorten the reaction time to less than 1 h at temperatures as low as 50 degrees C. The extremely small size of the nanoparticles and their dispersibility make it possible to use commercial Pluronic surfactants for evaporation-induced self-assembly of the nanoparticulate building blocks into periodic mesoporous structures. A solution of particles after synthesis can be directly used for preparation of mesoporous films without the need for particle separation. The mesoporous titania coatings fabricated using this one-pot procedure are crystalline and exhibit high surface areas of up to 300 m(2)/g. The advantages of the retention of the mesoporous order with extremely thin nanocrystalline walls were shown by electrochemical lithium insertion. The films made using microwave-treated nanoparticles showed supercapacitive behavior with high maximum capacitance due to quantitative lithiation with a 10-fold increase of charging rates compared to a standard reference electrode made from 20 nm anatase particles.
Szeifert
Johann M
JM
Department of Chemistry and Center for NanoScience, University of Munich (LMU), Munich, Germany.
Feckl
Johann M
JM
Fattakhova-Rohlfing
Dina
D
Liu
Yujing
Y
Kalousek
Vit
V
Rathousky
Jiri
J
Bein
Thomas
T
D008094:Lithium / Q000737:chemistry*; D015394:Molecular Structure; D053758:Nanoparticles / Q000737:chemistry*; D010316:Particle Size; D016062:Porosity; D013499:Surface Properties; D014025:Titanium / Q000737:chemistry*
C009495:titanium dioxide; C025096:titanium tetrachloride; D008094:Lithium; D014025:Titanium