An effective strategy for controlled fabrication and self-assembled modification of template-supported silica...

Silica nanosheets (SiO₂NSs) were successfully fabricated on the superelastic nickel-titanium alloy (NiTi) wire as a novel fiber for solid-phase microextraction (SPME). Before sol-gel coating, the NiTi wire was hydrothermally treated in alkaline solution for the in situ growth of NiO/TiO₂ nanosheets (NiO/TiO₂NSs). The sol-gel coating of SiO₂ on the surface of NiO/TiO₂NSs template was investigated and a thin shell of SiO₂ was found to cover NiO/TiO₂NSs, which can enlarge the effective surface area of the SiO₂ coating. This SiO₂ capped NiO/TiO₂NSs coated NiTi (NiTi@NiO/TiO₂@SiO₂NSs) fiber shows good extraction selectivity for polycyclic aromatic hydrocarbons (PAHs) and enhanced mechanical stability. After the self-assembled modification of SiO₂NSs by phenyltrichlorosilane, the NiTi@NiO/TiO₂@SiO₂NSs@Ph fiber shows higher extraction capability for non-polar PAHs. Thus, the conditions for the extraction of PAHs were investigated and optimized coupled to HPLC with UV detection. Under the optimized conditions, the analytical parameters of the SPME-HPLC methods with the NiTi@NiO/TiO₂@SiO₂NSs and the NiTi@NiO/TiO₂@SiO₂NSs@Ph fibers were determined and compared. The SPME-HPLC method with the NiTi@NiO/TiO₂@SiO₂NSs@Ph fiber was developed for the concentration and the determination of PAHs in environment water samples. The relative recovery of PAHs in real water samples spiked at 5 μg L^-1, 10 μg L^-1 and 30 μg L^-1 ranged from 88.1% to 109%. Furthermore, this fiber is stable due to the chemical bonding between different coatings and NiTi substrates. The fabrication of the NiO/TiO₂@SiO₂NSs@Ph coating on the NiTi fiber substrate is precisely controllable.