Preparation of nano-sized silica with solar energy conversion and storage function by immobilization of norbornadiene moieties to hyperbranched poly(amido amine)-grafted nano-sized silica

Abstract

The immobilization of norbornadiene (NBD) moieties onto nano-sized silica surface by the direct condensation of the surface terminal amino groups of hyperbranched poly(amido amine) (PAMAM)-grafted silica with 3-phenyl-2,5-norbornadiene-2-carboxylic acid is examined. It is found that the immobilization of NBD moieties onto the silica successfully proceeds in the presence of N,N′-dicyclohexylcarbodiimide (DCC) as a condensing agent. The immobilized NBD moieties onto the silica surface increases with increasing amount of amino groups of hyperbranched PAMAM-grafted silica, but the percentage of amino groups used for the immobilization of NBD moieties is decreased. The immobilized NBD moieties on the silica surface are readily isomerized to quadricyclane (QD) by photo-irradiation in n-hexane. Stored thermal energy by QD-immobilized silica is released as thermal energy by heating. The stored thermal energy of QD-immobilized silica increases with progress of the photo-irradiation time and became constant, about 30 J/g-silica, after 2 h.