Synthesis of Novel Fluorescent Cellulose Derivatives and Their Applications in Detection of Nitroaromatic Compounds

A series of fluorescent cellulose derivatives (AC-AET-DMANMs) with different degrees of substitution (DS) were successfully prepared. First, allyl cellulose (AC) was synthesized from cellulose in NaOH/urea aqueous solution, and then 2-aminoethanethiol (AET) was introduced onto the cellulose backbone via a thiol–ene click reaction. Finally, the fluorescent groups were introduced by the reaction of the AET-modified AC with 4-dimethylamine-1,8-naphthalic anhydride (DMANA). The structure and fluorescent properties of AC-AET-DMANMs were characterized by elemental analysis and FT-IR, ¹H NMR, UV–vis, and fluorescence spectroscopy. AC-AET-DMANM with lower DS_DMANM (referring to the DS of naphthalimide groups, ≤0.25) was soluble in DMSO. AC-AET-DMANM of DS_DMANM ≤ 0.09 displayed stable fluorescence in DMSO and even in the solid state. The emission of AC-AET-DMANM in DMSO quantitatively and sensitively responded to 2,4,6-trinitrophenol (TNP) and 2,4-dinitrophenylhydrazine (DNH) by fluorescence quenching, and the limits of detection were determined to be 1.4 × 10^–7 and 9.9 × 10^–8 mol/L, respectively. Moreover, a water-soluble fluorescent derivative (AC-AET-DMANM-2W) was prepared by a further thiol–ene click reaction between AC-AET-DMANM-2 and AET. It can also be applied in the detection of TNP and DNH in aqueous media with the detection limits of 2.5 × 10^–8 and 3.2 × 10^–8 mol/L, respectively. The quenching mechanism is attributed to the photoinduced electron transfer and resonance energy transfer of the fluorescent cellulose derivatives to TNP/DNH molecules. The results illustrate a high applicability of the novel fluorescent cellulose derivatives to the detection of specific chemical entities in aqueous/nonaqueous media