title: Electrochromic properties of asymmetric 4,4'-bipyridinium nanocomposites with inorganic nanoparticles.
abstract: Asymmetric mono cationic 4,4'-bipyridiniums, 1-butyl-4,4'-bipyridinium bromide (BUBP) and 1-methyl-4,4'-bipyridinium iodide (MEBP) showed electrochromic properties from blue to transparent yellow. The electrochromic bipyridiniums, BUBP and MEBP, were introduced to solid state electrochromic cells by using a solution of the bipyridinium, TiO2, and polymer electrolyte composite. The 4,4'-bipyridinium derivatives was attached to TiO2 nanoparticles and decreased aggregation of TiO2 to afford EC dye-TiO2 nanoparticles with average diameter smaller than 20 nm, as determined by FE-SEM. An all solid state electrochromic cells prepared from the dye-TiO2 nanoparticles showed improved electrochromic response compared to that without TiO2. Thus the cell from the BUBP- TiO2 nanoparticles responded to a step potential of +/-2 V within 7 sec with coloration efficiency of 117. The redox cyclability of the bipyridinium-TiO2 nanoparticles cell was longer than that of the TiO2 free cells. The enhanced properties were attributed to the conductivity and the large surface area of TiO2 nanoparticles.
authors.affiliation: Department of Chemical and Biomolecular Engineering, Yonsei University, 262 Seongsanno, Seodaemun-gu, Seoul, 120-749, Republic of Korea.
authors.forename: Yuna
authors.initials: Y
authors.lastname: Kim
authors.forename: Si Young
authors.initials: SY
authors.lastname: Yang
authors.forename: Eunkyoung
authors.initials: E
authors.lastname: Kim
mesh_terms: D003116:Color; D004563:Electrochemistry; D008855:Microscopy, Electron, Scanning; D053761:Nanocomposites / Q000737:chemistry*; D010880:Piperidines / Q000737:chemistry*; D013499:Surface Properties; D014025:Titanium / Q000737:chemistry*
chemical_list: C505213:4,4'-bipiperidine; D010880:Piperidines; C009495:titanium dioxide; D014025:Titanium