An Engineered Au-MXene Sorption Trap Enables Dual-Channel Ultrafast and Selective Detection of Trace Gaseous Elemental Mercury

Accurate detection of trace atmospheric mercury is critical for toxicological assessment and environmental protection. However, achieving parts per billion-level sensitivity with high selectivity between gaseous elemental mercury (Hg⁰) and oxidized mercury (Hg²⁺) remains a significant challenge. Here, we present a novel dual-channel enrichment trap system that selectively captures Hg⁰ by using a layered Au-MXene (Ti₃C₂T_<i>x</i>) composite as the sorption trap. This composite demonstrates exceptional selectivity for Hg⁰, with a selectivity ratio of up to 76.7 over Hg²⁺, and achieves 99.7% ± 0.3% (<i>n</i> = 3) sorption efficiency for ppb-level Hg⁰ within 30 min at room temperature. Complete desorption is achieved in just 90 s at 300 °C, demonstrating a response time of 45 s for Hg⁰ detection through the dual-electrothermal Hg⁰ channel. The Au-Ti₃C₂T_<i>x</i> preconcentration cartridge exhibits excellent moisture resistance, high-temperature stability, and long-term durability. Density functional theory (DFT) calculations reveal that the built-in electric field at the Au-Ti₃C₂T_<i>x</i> interface accelerates electron transfer, reducing preconcentration and regeneration times. This technology integrates seamlessly with the cold vapor atomic absorption spectrophotometer (CVAAS) method to form a mercury dual-channel continuous emission measurement system (Hg DCEMS), ensuring highly selective and precise trace Hg⁰ detection. This advancement provides a device for accurately measuring the Hg⁰ concentration, enabling better mercury pollution control.