Conjugated grafting of 1, 4-diethynylbenzene on mesoporous silicon nanowires by modest thermal mono-silylation

Mesoporous silicon nanowires (mp-SiNWs) are increasingly attracting scientific and technical attention, due to the porosification-induced quantum confinement and increase of surface areas. The fundamental studies in mp-SiNWs mainly focus on the intrinsic properties, but there is little report on surface modification highly desired for SiNW-based device applications. This work reports that at modest temperature of 110 °C, 1,4-diethynylbenzene (DEBZ) is mono-silylatedly grafted on mp-SiNWs via Si-C=C contacts to retain the molecular conjugation structures as confirmed by ATR-FTIR. The modest mono-silylation can be adapted to solid SiNWs(100) and SiNWs(111) without pore, and renders the photoluminescence (PL) of DEBZ blueshift on the grafted surfaces. By the evaluation of surface coverage and anti-oxidation effect via XPS, the grafting of diverse SiNWs is optimized by the mono-silylation not shorter than 12 hr. Compared to relatively smooth surfaces of solid SiNWs, mp-SiNWs appear to have porosified rough surfaces with numerous surface defects, leading to the deterioration in surface coverage and stability of the mono-silylated conjugation layers. The DEBZ-grafted monolayers retain C=C bonds at the free ends; hence, this work comes up with a modest thermal method to modify mp-SiNWs with chemically active monolayers that will be facilely subjected to further chemical modification and surface functionalization. Furthermore, the mono-silylation encodes mp-SiNWs with molecular PL, opening a door to flexibly engineer the optical properties of mp-SiNWs for optoelectronic and bio-detection applications.