Highly dispersed carbon nanotube in new ionic liquid-graphene oxides aqueous dispersions for ultrasensitive dopamine detection

• New aqueous dispersions of GO-[BMIM][PF6] water formed through simply tuning pH.
• A new surfactant-free, water-processable CNT-GO-[BMIM][PF6] composite was also conveniently created by a simple sonication method at room temperature.
• This composite displays excellent sensitivity and selectivity for the detection of DA with lowest detection limit.
• This proposed method was successfully applied to detect dopamine in human serum and human urine samples.

Graphite oxide (GO) is a pH-dependent amphiphile with hydrophilic edges and a more hydrophobic basal plane. It was found that when the hydrophobic prototype ionic liquid (IL) of 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF6]) was added into GO water, it experienced changes from coagulation to being redispersed in water phase by constantly turning its pH to alkali condition. Then new aqueous dispersions of GO-[BMIM][PF6] “water” formed after facile sonicate. The introduction of [BMIM][PF6] not only minimize the defects of poor electrical conductivity of GO and more interesting is that the carbon nanotube (CNT) can be highly dispersed in this GO-[BMIM][PF6] water through a simple and facile ultrasonic method at room temperature, forming a new composite of GO-[BMIM][PF6]-CNT with high dispersibility. This novel composite enhanced its electrochemical signal obviously in the measurement of dopamine (DA) in biological systems and exhibited a wider linear response ranging from 8.0 × 10−12–1.5 × 10−5 M. The detection limit of 3.0 × 10−12 M at a signal to-noise ratio of 3 was two orders of magnitude lower than that reported previously.

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