posted on 2021-03-23, 05:33authored byYintao Li, Zisheng Luo, Gangfeng Li, Tarun Belwal, Li Li, Yanqun Xu, Bin Su, Xingyu Lin
In the present study, a novel electrochemical
sensor for the direct
detection of caffeine in the crude sample has been prepared by plasma-triggered
polydimethylsiloxane (PDMS) deposition on the indium tin oxide electrodes
supported with silica nanochannels. The deposited PDMS contains both
the original hydrophobic and oxidized hydrophilic PDMS oligomers.
Nanochannels modified with these two kinds of PDMS with opposite wettability
only allow the passage of small amphiphilic molecules such as caffeine,
while other molecules including hydrophilic, hydrophobic, and large
ones were all rejected. With the excellent shielding properties, the
modified nanochannel electrode exhibits excellent anti-interference
and antifouling capability, which could be directly used for the detection
of caffeine in real crude food such as tea, milk, coffee, and coke
without sample pretreatments. Moreover, the modified electrode has
good repeatability and stability. In contrast, severe interference
was observed when conventional electrodes were used directly in these
unprocessed samples. The linear ranges of caffeine were determined
to be between 50 nmol/L and 700 μmol/L, with a limit of detection
of 20 nmol/L. The developed sensor provides a very simple, rapid,
and cost-effective way for the interference-free and fouling-free
analysis of specific amphiphilic compounds and can be extended to
a wide range of applications.