Jie Hu,Hui Chen,Ruibin He,Pran Gopal Karmaker,Xiupei Yang,Fenglin Tang
Rapid and sensitive detection of picric acid (PA), a highly toxic and water-mobile nitroaromatic pollutant, is essential for environmental safety and public health protection. Herein, we fabricate a dual-emission ratiometric fluorescent probe by immobilizing high-load red-emitting carbon dots (R-CDs) onto NH₂-functionalized MIL-53(Al), forming an R-CDs/NH 2 -MIL-53(Al) composite for selective aqueous-phase PA sensing. R-CDs were hydrothermally synthesized with citric acid and neutral red as co-precursors. The loading efficiency was maximized by systematically optimizing precursor molar ratios and dilution conditions. The composite exhibits distinct selective fluorescence quenching in the presence of PA. Mechanistic characterizations, including fluorescence lifetime decay measurements and spectral overlap analysis, verify that the fluorescence quenching originates from two synergistic quenching pathways, namely competitive light absorption and fluorescence resonance energy transfer (FRET), rather than nonspecific physical interactions. This ratiometric sensing platform achieves a wide linear detection range of 0.1–70 μM and an ultralow limit of detection (LOD) of 32.9 nM. Spike-and-recovery assays using real environmental water samples (tap water, commercial bottled mineral water, and Jialing River surface water) produced recoveries of 99.7%–105.1%, with relative standard deviations (RSD) below 5.86% ( n = 3). Furthermore, a smartphone-enabled visual quantitative method based on RGB color channel analysis was constructed, enabling portable on-site detection without large-scale laboratory instrumentation.
Yu Zhu Fan,Ying Zhang,Na Li,Shi Gang Liu,Ting Liu,Nian Bing Li,Hong Qun Luo
In this work, novel water-soluble and blue fluorescent carbon dots (C-dots) were synthesized using one-pot hydrothermal method with malonic acid and urea, and were then used as a label-free fluorescent probe for selective, sensitive, and rapid determination of picric acid (PA). The sizes of the as-prepared C-dots were mainly distributed in the range of 1.5–3.0 nm with an average diameter of 2.5 nm. Moreover, the C-dots displayed blue fluorescence with an emission peak at 395 nm (320 nm excitation), which also showed good stability and anti-photobleaching ability. Interestingly, the fluorescence of C-dots could be selectively quenched by PA within 10 s. Based on this phenomenon, a label-free fluorescence assay was proposed for specific determination of PA. The fluorescence intensity of probe showed a linear response to PA in the concentration range of 0.1 to 26.5 μM with a low detection limit of 51 nM (S/N = 3). Finally, the resultant fluorescent probe was successfully applied to the detection of PA in real water samples.
New energetic transition metal complexes based on methyl carbazate (MCZ) and picric acid (PA), [M(MCZ)2(H2O)2]PA2 (M = Mn2+ (1), Fe2+ (2), Co2+ (3), Ni2+ (4), Cu2+ (5), Zn2+ (6)) and [Cd(MCZ)2(H2O)3]PA2·4H2O (7), were synthesized by a facile strategy, and characterized by FT-IR and elemental analysis. Their crystal structures were determined by single crystal X-ray diffraction. Thermal stability of the seven complexes was studied by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Decomposition onset temperatures of 1 to 7 rise in the following order: 2 < 5 < 3 < 4 < 7 < 6 < 1. The apparent activation energy (Ea) of the thermal decomposition processes of these compounds is in the range of 112.3 to 232.9 kJ mol−1, which illustrates their moderate activity of thermo-kinetics. Sensitivity tests reveal that these compounds are insensitive to friction (>360N), and the impact sensitivities of these compounds fall within the range of 2.75 (complex 7) to 40 J (complex 1). Furthermore, these compounds were examined for use as additives to promote the thermal decomposition of ammonium perchlorate. Results from DSC reveal that all of them exhibit excellent catalytic performance. Notably, when compound 5 is added to AP, there is only one exothermic peak with a peak temperature of 240 °C in its decomposition process; the endothermic crystal transformation of AP disappeared, which shows the outstanding catalytic effect of compound 5.
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