Development of a novel label-free NIR aptasensor based on triphenylmethane dyes for rapid and sensitive detection of copper ions†

Heavy metal pollution, particularly from copper ions (Cu²⁺), poses a significant threat to both the ecological environment and human health. However, traditional copper ion analysis techniques are often hindered by the need for expensive equipment, labor-intensive sample preparation and skilled operation, which limits their effectiveness for field and real-time applications. In this work, we report a novel near-infrared aptamer sensor (NIRApt) that originates from the binding reaction between the DNA aptamer Apt_Cu and the fluorescent small molecule crystal violet (CV), enabling rapid detection of Cu²⁺ through the competitive effect of Cu²⁺ with Apt_Cu. This sensor shows a significant enhancement in NIR fluorescence after aptamer binding. NIRApt exhibits superior performance, requiring only three core components to achieve a fast response time and operational simplicity in less than a minute. The sensor shows high sensitivity with a detection limit as low as 61 nM, making it suitable for the detection of trace amounts of Cu²⁺ in diverse samples. The efficacy of NIRApt has been validated through successful applications in real water samples, highlighting its promising potential for environmental monitoring.