Polyelectrolyte brush templated multiple loading of PD nanoparticles onto TiO₂ nanowires via regenerative counterion exchange-reduction

In this paper, a novel strategy was reported to produce ternary nanocomposite containing TiO₂ nanowires, poly[(dimethylamino)ethyl methacrylate] (PDMAEMA) brush and Pd nanoparticles. PDMAEMA brushes were grafted from catecholic initiator anchored on TiO₂ nanowires via surface-initiated atom transfer radical polymerization (SI-ATRP) at ambient conditions. The PDMAEMA uniformly covered the surface of TiO₂ nanowires and the two component of PDMAEMA and TiO₂ shows clear boundary interface. PDMAEMA brushes were derived with CH₃I to form quaternized-PDMAEMA (Q-PDMAEMA) so as to facilitate anion exchange with PdCl₄^2-, which was followed by in situ reduction with NaBH₄ to obtain the TiO₂ nanowires- Q-PDMAEMA/Pd(0) ternary nanocomposite. Pd nanoparticles have very small size of about 2-4nm and monodisperse, uniformly distributed among polymer brush network. Interestingly, after reduction reaction, concurrent with generation of Pd nanoparticles, the ammonium cations were largely recovered, which allows further breath-in PdCl₄^2- counterions and uploads more Pd nanopaticles by repeated steps. The responsivity of both PDMAEMA and Q-PD-MAEMA decorated TiO₂ nanowires was studied in response to pH and salt solution. The electrocatalytic behavior of the ternary nanocomposite was investigated.