2.2. Synthesis of β-cyclodextrin functionalized graphene (Grp-β-CD)
from graphene oxide
Grp-β-CD was synthesized following the method reported
earlier (Guo et al., 2010) with some minor modification. Aqueous
solution of GO (5 mg/mL) was prepared by the modified Hummer's
method (Marcano et al., 2010). In a separate vial, 400 mg of β-
cyclodextrin was dissolved in 10 mL water and mixed with 200 μL
NH4OH and 1 mL GO solution. The whole solution was
continuously stirred for an hour, followed by addition of 20 μL
hydrazine monohydrate solutions (0.04 M). Next, the solution was
heated to 80–90 °C for an hour with constant stirring. The stable
black solution was then dialysed against distilled water with
cellulose membrane for overnight. Finally, the solution was diluted
with 0.1 M Phosphate Buffered Saline (PBS) of pH 7.4 and used as
stock solution for the cholesterol sensing.
For the physical characterization of the sensing material,
Transmission Electron Microscopy (TEM), FT-IR and Raman spectroscopy
were carried out. The TEM images were taken using a
transmission electron microscope (FEI model Tecnei G2 20 S with
200 kV accelerating voltage and resolution range of 50 nm to
1 mm). FT-IR