As a widely-explored subject for numerous applications, silica sol-gel has attracted

the attention of our group for sensor development. This study focused on pore surface

modification of two different types of silica sol-gel by post-grafting method, and

construction of stable silica hydrogel-like thin films. By monitoring the mobility and

photostability of rhodamine 6G (R6G) molecules in silica alcogel thin films through

single molecule spectroscopy (SMS), the guest-host interactions altered by

post-synthesis grafting were examined. Similar post-grafting method was then applied

to highly hydrated silica hydrogel monoliths; more efficient surface modification was

expected, because larger pore sizes in hydrogel provide higher accessibility of

organosilane reagents. During the study of post-grafting on alcogel thin film, a new

approach to produce stable silica hydrogel-like thin films was discovered. A lot of effort

has been made to improve the reproducibility of sample preparation, and the guest

loading capacity of silica hydrogel-like thin films. A prototype silica hydrogel-like thin

film pH sensor was also constructed and tested.

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Understanding how guest-host interactions can be affected by silane modifications

is critical to sensor development. It helps tailoring the local environments inside silica

sol-gel matrix, so that higher guest loading, longer shelf-life, higher sensitivity and

faster response of silica gel based sensors could be achieved. Stable silica hydrogel-like

thin film with a thickness only around 200 nm, which to the best of our knowledge has

never been accomplished before, is expected to be a better substrate for sensing devices

that demand faster response than thick monoliths