Uniform stain pattern of robust MOF-mediated probe for flexible paper-based colorimetric sensing toward environmental pesticide exposure

Excessive residual pesticides have raised overall environmental damage and health hazard issues, thus the development of facile and sensitive means for pesticide monitoring in different environmental field is desperately needed but challenging. In this work, a flexible paper-based colorimetry beating coffee-ring effect is achieved toward sensing environmental pesticide exposure in user-friendly mode. First, to circumvent poor performance of biomolecules, robust probe is designed by imprinting metal-organic frameworks (MOFs) with specific pockets, enabling to provide "key-lock" identification and sensitive quantitative information under harsh environment. Innovatively, integrating the MOF-mediated probe with filter paper, a well-distributed sensing interface is harvested to reduce colorimetric signal fluctuation for reliable detection properties, which is ascribed to superior wetting behavior of filter paper for avoiding ring-like deposit formation. Additionally, the uniform profile is simulated by Fluent numerical software. Further exploiting smartphone-assisted image acquisition and selfadaptive signal model, the simple-to-perform system exhibits good accuracy toward ppb-level thiacloprid free of colored background interference. A low limit of detection of 0.04 mu M thiacloprid (corresponding to 0.01 mu g g-1 by weight) is achieved. Moreover, it allows for in-filed monitoring thiacloprid exposure in agricultural wastewater, soil, fresh vegetables with satisfactory recoveries ranging from 92.7 % to 109.0 %, verifying the broad potential applications for point-of-use tracking of environmental pesticide and eventually bringing benefits to ecosystem protection in resource-deficient settings.