Qian Wang

While oxidative reactive species (RS) have been extensively studied for their critical role in trace organic contaminant (TrOC) degradation, the mechanistic contributions of reductive RS in aquatic environments remain poorly understood. In this study, we report a previously unrecognized photochemical pathway for generating a highly reductive carbon dioxide radical anion (CO₂^{• -}) through synergistic interactions between excited triplet-state dissolved organic matter (³DOM*) and ubiquitous low-molecular-weight carboxylic acids (LCAs) in surface waters. Using carbamazepine (CBZ) as a model compound, electron paramagnetic resonance confirmed photogenerated CO₂^{• -} in mixed oxalic acid and anthraquinone-2-sulfonate (AQ2S) systems, driving a 429% increase in the CBZ photodegradation rate with respect to AQ2S alone. The CO₂^{• -}-driven enhancement was generalizable across diverse ³DOM* surrogates and LCAs as well as natural DOM samples. By combining advanced ab initio molecular dynamics simulations, quantum chemical calculations, and mass spectrometry analysis, we demonstrate that photogenerated CO₂^{• -} initiates ultrafast (within picoseconds) electron transfer reactions with CBZ, leading to the formation of degradation products. This study not only reveals a new source of reductive CO₂^{• -} in surface waters but also suggests the important role of reductive RS in the TrOC transformation in sunlit surface waters.

Copper is an important environmental pollutant that poses a significant threat to human health and environmental safety. Therefore, the development of methods for detecting Cu²⁺ is of great significance. A novel fluorometric/colorimetric dual-mode sensor for detecting Cu²⁺ was synthesized by Schiff base reaction using fluorescein hydrazide and 8-hydroxyjulonidine-9-carboxaldehyde as raw materials. Cu²⁺ could form a complex with the probe in a stoichiometric ratio of 1:1. Within 1 min, the fluorescence of the probe rapidly quenched at 540 nm, and the absorbance reached a stable state at 452 nm. The color of the solution changed from light yellow to yellow, achieving real-time and visual detection of Cu²⁺. This probe exhibited exceptional selectivity for Cu²⁺. Within the range of 0–12 μM, the fluorescence intensity of the probe demonstrated a strong linear correlation with the concentration of Cu²⁺ (R² = 0.994), with a detection limit of 0.22 µM. In the ultraviolet colorimetric method, when the Cu²⁺ concentration reached 14 μM, the absorbance stabilized (R² = 0.996), and the detection limit for Cu²⁺ was determined to be 0.38 µM. Furthermore, this probe enabled reversible detection of Cu²⁺, and its performance in real water sample analysis and cellular bioimaging was proven to be highly satisfactory.

Mercury is a highly toxic heavy metal that poses serious threats to human health and environmental safety, highlighting the critical importance of accurate Hg²⁺ detection. In this study, a novel fluorescent probe AP was synthesized by conjugating fluorescein, serving as the luminescent group, with pyridine-2-carboxaldehyde to enable selective Hg²⁺ detection. Hg²⁺ binds to AP in a 1:2 stoichiometric ratio, inducing the opening of the spiro-lactam ring and resulting in a significant fluorescence enhancement. The probe exhibited excellent selectivity and sensitivity toward Hg²⁺. A strong linear correlation was observed between its fluorescence intensity and Hg²⁺ concentration (R² = 0.99952), with a detection limit of as low as 9.75 × 10⁻⁸ mol/L. The average recoveries of Hg²⁺ across various water matrices ranged from 95.23% to 103.40%, with relative standard deviations (RSDs) below 3.07%. These results indicate that the probe performs effectively in real water-sample testing.