Double-reverse-signal ratiometric fluorescence probe for residual determination of chlorpyrifos pesticide in surface water based on scalable upcycling of rice straw to luminescent CQDs via energy-efficient alkali treatment

• Boosting the value of rice straw via upcycling to luminescent CDs. • First room temperature synthesis of CDs from rice straw by alkali treatment. • CDs as the first ratiometric fluorescence probe for chlorpyrifos insecticide. • Excellent performance in determination of chlorpyrifos in tap, river, and irrigation water. A smart, green, practical, and simple method has been developed for the preparation of blue emissive carbon dots (RS-CDs). The developed synthesis protocol is accomplished at room temperature via an instrument-free approach using the alkali treatment of rice straw. The furnished RS-CDs were thoroughly characterized via transmission electron microscopy, energy-dispersive X-ray spectrometry, x-ray photoelectron spectroscopy, UV-Vis, and fluorescence spectroscopy. The RS-CDs exhibited excellent performance as a double-response-reverse type ratiometric fluorescence probe for the widely used insecticide chlorpyrifos. By systematically investigating and optimizing the experimental conditions, a new sensitive and accurate RS-CDs-based ratiometric fluorescence probe was constructed, taking advantage of the simultaneous decrease of emission intensity at 396 nm and increase of a new emission peak at 340 nm up on adding chlorpyrifos. The ratio of fluorescence intensity at 340 and 396 nm (F 340/396 ) showed excellent correlation to chlorpyrifos concentration over the range of 7.1 – 142.4 µM with a detection limit of 2.3 µM. Excellent recovery percentages have been obtained for chlorpyrifos in tap, river, and irrigation water, 102.24 ± 1.52, 104.33±1.79, and 100.43±2.51%, respectively. The presented approach is the first to convert agricultural waste into nanomaterial by room temperature treatment. Boosting the value of rice straw via upcycling to luminescent CDs is one of the things that helps sustain the practice in limited-income labs. The environmental impact, greenness, practicality, economical, and analytical attributes of the developed method have been positively confirmed by different recent metrics.