Abstract:
Because of its high surface area and combination of various functional groups, graphene oxide (GO) is
currently one of the most actively studied materials for electroanalytical applications. It is not practical to
utilize self-supported GO on its own and thus it is commonly integrated with different supporting
carriers. Having a large lateral size, GO can only wrap the particles of the support and thus can
significantly reduce the surface area of porous materials. To achieve synergy from the high surface area
and polyfunctional nature of GO, and the rigid structure of a porous support, the lateral size of GO must
essentially be decreased. Recently reported graphene oxide quantum dots (GOQDs) can fulfil this task.
Here we report the successful preparation of an SiO2-GOQDs hybrid, where GOQDs have been
incorporated into the mesoporous network of silica. The SiO2-GOQDs emit a strong luminescence with
a band maximum at 404 nm. The Raman spectrum of SiO2-GOQDs shows two distinct peaks at
1585 cm1 (G-peak) and 1372 cm1 (D-peak), indicating the presence of a graphene ordered basal plane
with aromatic sp2-domains and a disordered oxygen-containing structure. Covalent immobilization of
GOQDs onto aminosilica via such randomly structured oxygen fragments was proven with the help of
Fourier transform infrared spectroscopy, solid-state cross-polarization magic angle spinning 13C nuclear
magnetic resonance, and X-ray photoelectron spectroscopy. SiO2-GOQDs were used as a modifier of
a carbon paste electrode for differential pulse voltammetry determination of two antibiotics
(sulfamethoxazole and trimethoprim) and two endocrine disruptors (diethylstilbestrol (DES) and estriol
(EST)). The modified electrodes demonstrated a significant signal enhancement for EST (370%) and DES
(760%), which was explained by a p–p stacking interaction between GOQDs and the aromatic system of
the analytes.
