Universal
Multilayer Assemblies of Graphene in Chemically
Resistant Microtubes for Microextraction
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Abstract
Graphene is a new kind of two-dimensional
carbon nanomaterial with
excellent properties and is promising for solid-phase microextraction
(SPME). Plastic microtubes such as poly(tetrafluoroethylene) (PTFE)
and poly(ether ether ketone) are ideal substrates for in-tube SPME.
However, immobilization of graphene layers onto these materials is
still a problem due to their nature of chemical resistance. In order
to solve the problem, we proposed a novel method based on universal
mussel-inspired polydopamine (PD) and layer-by-layer assembly of graphene
in this work. To make a graphene assembly layer inside PTFE, the strategy
includes two major steps. First, a PD layer is made on the PTFE surface
by noncovalent interaction. Second, multilayer graphene is assembled
on the PD layer by covalent interaction. By repeating these two steps,
a functional graphene oxide (FGO)-modified PTFE tube with a controllable
number of layers can be obtained. Morphology of the multilayer structure
of graphene has been confirmed by scanning electronic microscopy.
Formation of the covalent layer has also been characterized by Foourier
transform infrared and X-ray photoelectron spectroscopy. It is very
interesting that (FGO-PD)<sub>3</sub>-PTFE shows exceptional efficiency
for SPME. Enrichment from 1082- to 2331-fold was achieved for six
polyaromatic hydrocarbons (PAHs). An online SPME-HPLC-fluorescent
detection method has been developed on the basis of (FGO-PD)<sub>3</sub>-PTFE. For qualitative analysis of PAHs, the method has low limits
of detection of 0.05–0.1 pg/mL, which is significantly lower
(up to 1000 times) than that reported in literature. The method shows
wide linear range (0.3–200 pg/mL), good linearity (<i>R</i><sup>2</sup> ≥ 0.9968), and good reproducibility
(relative standard deviation < 3.4%). The method has been applied
to determine PAHs in environmental samples. Good recoveries were obtained,
ranging from 85.1% to 96.7%