Picric acid (PA) is difficult to self-degrade in the
environment
and is prone to cause soil and water pollution. Therefore, achieving
highly sensitive detection of PA in the aqueous phase is of great
importance for social security, as well as human health. Conjugated
porous polymers (CPPs) have great potential in the field of fluorescence
sensing due to their good luminescence and intrinsic porosity. In
this study, tetraarylethylene-based CPP named PX-TPA containing triphenylamine
groups was designed and synthesized via Suzuki-miniemulsion polymerization
method, combining the porosity of the CPP, good luminescence property
of tetraarylethylene, and electron-rich characteristics of triphenylamine,
which are beneficial for the interaction with PA and the diffusion/transport
of PA analyte in the polymer to realize an efficient fluorescence
sensing. Due to the miniemulsion polymerization, the nanoparticle
morphology of PX-TPA was obtained with a particle size of 75 nm, which
suggests good dispersion in the aqueous phase. PX-TPA nanoparticles
possess a specific surface area of 49.5 m2/g and a pore
size of about 5.6 nm. The sensitive and selective detection of PA
based on PX-TPA nanoparticles was obtained in pure aqueous phase,
with a Stern–Volmer quenching constant up to 7.67 × 106 M–1. Moreover, the anti-interference detection
of PA against other nitro compounds and common ions in water was realized.
Furthermore, the spike/recovery test was used for PA detection in
different water samples, and the spiked recoveries were obtained in
the range of 95.80–108.00%. The t test method
proves that the fluorescence sensing method with the nanoparticles
as the sensing material realizes reliable PA detection at the 95%
confidence level. It is concluded that the sensitive and selective
detection of PA in water by PX-TPA nanoparticles is mainly attributed
to the combination of excited-state photoinduced electron transfer,
ground-state competitive absorption, and Förster resonance
energy transfer.