Modification of hollow core-shell particles with poly (amino) acids to induce chirality

Abstract

Due to the potential environmental applications, photocatalytic reactions occurring on the surface of photoirradiated titanium (IV) oxide (TiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ) have garnered a wide interest. Despite displaying high photocatalytic activity, the utilization of TiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> is limited by its lack of selectivity. This paper presents the synthesis of platinized TiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> core and hollow silica shell (SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> /void/Pt-TiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ), with the silica pores modified with chiral agents, namely poly (amino acid)s. The fabrication of the composite is firstly done by modifying the surface of TiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> powder with amino groups using 3-amino-propyltrimethoxysilane (APS).The resulting material and platinized TiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> is tested out in the photocatalytic redox-combined synthesis of L-PCA (pipecolinic acid) from (racemic) DL-lysine in order to obtain optically active PCA, The results show that platinized TiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> modified with poly (L-lactic acid) displays a higher optical purity of L-PCA as compared to normal platinized TiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> , although the conversion was slightly lower. Platinized TiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> modified with poly-L-lysine on the other hand, demonstrates a much lower conversion percentage among the three samples prepared.