Download Title: Ultrathin Growth of SiO2 Shells on Fluorescent High

Title: Ultrathin Growth of SiO2 Shells on Fluorescent High-Temperature High-Pressure
Nanodiamonds
Institution: San Jose State University, Department of Chemistry
Authors: Andres Arreola, Anida Len, Perla Sandoval, Abraham Wolcott
Abstract:
Early cancer detection is needed to ensure life-saving cancer therapies can be
implemented. Improved diagnostics are important for ovarian and pancreatic cell lines, in
which late stage detection is common. We aim to develop new biolabeling and biosensing
tools based on high-pressure, high-temperature (HPHT) fluorescent nanodiamonds
(FNDs). FNDs are an attractive tool for cancer detection because of their comparable size
to antibodies, surface tunability, and lack of photobleaching. Specifically, our goals are to
investigate the fundamental properties of FNDs’ surface chemistry using silica
functionalization and produce high ND-conjugate yields. Previous work revealed that the
surface of oxidized HPHT NDs had an alcohol (-OH) rich surface and silica (SiO2) based
chemistry has been used in this study to grow ultrathin shells. Tetraethylorthosilicate
(TEOS) is hydrolyzed to Si(OH)4 which leads to a nucleophilic attack by an alcohol
groups on the ND surface producing a silyl ether bond (C-O-Si) that primes the surface
for further SiO2 growth. Silica shell thickness is controlled by adjusting reaction times.
Size and surface features of our particles were determined by dynamic light scattering
(DLS) and atomic force microscopy (AFM), while surface characterization was
determined by Fourier transform infrared (FTIR) spectroscopy. Further determination of
composition will be accomplished through energy dispersive X-ray spectroscopy (EDS).
Future work includes grafting polyethylene glycol and amine moieties for colloidal
stabilization and bioconjugation to cancer-specific antibodies.