Rational construction of a robust nanoprobe for highly selective and sensitive nitrite and formaldehyde detection and imaging in real foods

Nitrite (NO2-) and formaldehyde (FA) are practice common food hazards, seriously threatening human health. Herein, for the first time a de novo nanoprobe, named MTB, with a single response group exhibiting different optical signals for NO2-/FA was reported, which had the following characteristics: i) An adamantane-labeled small molecule NI-adH grafted with polycyclodextrin (Poly-β-CD) to form MTB with excellent water-solubility and biocompatibility. ii) O-phenylenediamine (OPD) with photoinduced electron transfer (PET) played both a fluorescence quencher and as NO2-/FA trappers. Interestingly, fixed on pH6.0, OPD rapidly reacted with NO2- forming triazoles, inhibiting the PET effect and releasing bright fluorescence at 530 nm. While adding FA, OPD ultrafast formed Schiff-base, and MTB absorption red-shifted from 452 nm to 545 nm. Moreover, MTB exhibited excellent selectivity, high sensitivity (21.8 nM/17.1 nM), and rapid response towards (60 s/65 s) NO2-/FA. Impressively, MTB has been successfully adopted to detect NO2-/FA in real foods with satisfactory results.