All-in-one strategy for the nano-engineering of paper-based bifunctional fluorescent platform for robustly-integrated real-time monitoring of food and drinking-water safety.

Cu2+ contamination and food spoilage raise food and drinking water safety issues, posing a serious threat to human health. Besides, Cu2+ and H2S levels indicate excess Cu2+-caused diseases and protein-containing food spoilage. Herein, a coumarin-containing bifunctional paper-based fluorescent platform integrated with a straightforward smartphone color recognition app is developed by an all-in-one strategy. The proposed fluorescent materials can simultaneously detect Cu2+ and H2S for on-demand food and drinking water safety monitoring at home. Specifically, a coumarin-derived fluorescence sensor (referred to as CMIA) with a low detection limit (0.430 µM) and high-selectivity/-sensitivity for Cu2+ is synthesized through a simple one-step route and then loaded onto commercially used cellulose fiber filter paper to engineer a biomass-based fluorescent material (CMIA-FP). The CMIA-FP offers user-friendly, high-precision, fast-responsive, and real-time visual monitoring of Cu2+. Moreover, CMIA forms a chemically stable complex with Cu2+, loaded onto filter paper to prepare another biomass-based fluorescent platform (CMIA-CU-FP) for visual real-time monitoring of H2S. Based on the exquisite composition design, the proposed dual-function paper-based fluorescent materials equipped with a smartphone color recognition program concurrently realize fast, accurate, and easy real-time monitoring of Cu2+ in drinking water and H2S in chicken breast-/shrimp-spoilage, demonstrating an effective detection strategy for the Cu2+ and H2S monitoring and presenting the new type of biomass-based platforms for concentrated reflection of drinking water and food safety.

Converting commonly-used paper into nano-engineered fluorescent biomass-based platform for rapid ClO- quantitative detection in living cells and water sources.

Hypochlorous acid (HClO) and derivative ionic form (ClO-) are significant components of reactive oxygen species, and thus various diseases are correlatively related to the concentration of ClO-. Recently, paper-based indicators have been confirmed to be efficient strategy for sensing hazardous and noxious substances. However, most of these materials can only achieve qualitative detection of the substrates. Herein, an extremely simple manufacturing strategy was proposed to convert commonly-used paper into nano-engineered fluorescent biomass-based platform (CMJL-FP) integrated with on-demand self-assembled colorimetric and ratiometric fluorescence sensor (CMJL) for rapid ClO- quantitative detection in organisms or water sources using smartphones. The CMJL exhibited a highly selective and sensitive ratiometric response to ClO- at a low detection limit (LOD = 92.6 nM). The associating interactions between the fluorescence nano-particles and micro-nano fibers of CMJL-FP ensure good-stability during ClO- detection. It has been experimentally demonstrated that CMJL-FP allows one to realize the rapid quantitative detection of ClO- ions in living cells and large-scale water sources by using color recognition software as part of a simple smartphone. Therefore, integrating the proposed fluorescent paper with smartphones provides an effective, sustainable, cheap and conceptual strategy for quantitative detection of hazardous and noxious substances in organisms and environments.

Fly-antennae-inspired biomass-based fluorescent platform for NH3 quantitative detection and visual real-time monitoring of seafood spoilage.

Traditional strategies for quantitative detection of NH3 and monitoring of seafood spoilage still have some pervasive issues of cumbersome operation, time-consuming, high-cost, and inefficient real-time monitoring, and visualization. Integration of biomass-based materials and aggregation-induced emission (AIE) fluorescence probes exhibit conceivable potential in seafood detection and environmental monitoring. Herein, a fly-antennae-inspired biomass-based solid-state fluorescent platform (PAA-FP) with effective, easy-to-use, reusable, low-cost and highly sensitive characteristics is nanoengineered for NH3 quantitative detection (detection limit = 0.5 ppm) and visual real-time monitoring of seafood spoilage using smartphones. The PAA-FP possesses an anticipative "fly-antennae-like" microstructure and offers selective recognition of NH3 by naked eyes in daylight with excellent solid-state fluorescence properties. Moreover, PAA-FP is simply reused at least 5 times after AcOH fumigation. Comprehensive application experiments substantiate that PAA-FP successfully achieves quantitative detection of NH3 and realizes the visual real-time daylight monitoring of food spoilage using a simple color recognizing smartphone software. The present study demonstrates an effective fabrication strategy to explore various multifunctional biomass-based materials for sensing hazardous and noxious substances.

A Schiff-based AIE fluorescent probe for Zn2+ detection and its application as "fluorescence paper-based indicator".

A Schiff-based aggregation induced emission (AIE) fluorescent probe with excited intramolecular proton transfer (ESIPT) mechanism was synthesized by grafting 2-hydrazinobenzothiazole onto 2,6-diformyl-4-methylphenol. The probe recognizes Zn2+ selectively and sensitively, accompanied by a significant fluorescence emission increasement change from light yellow-green to strong green. Additionally, a stabilization time of at least 30 min was kept in the recognition process. Besides, a linear relationship was observed between the concentration of Zn2+ and the fluorescence intensity at 525 nm (0.05-10 µM). And thus, the probe can detect Zn2+ quantitatively in aqueous solution with a low detection limit of 1.9 × 10-8 M. Based on the AIE property and the selective recognition of Zn2+, SCH was strategically loaded on the filter paper to develop a novel paper-based indicator for on-site and high-efficiency detection of Zn2+. The results showed that the paper-based indicator could be conveniently applied to the visual inspection of Zn2+ as expected and SCH in the paper-based indicators fortunately exhibited a better stability. Furthermore, our comprehensive application evaluations have confirmed that SCH was capable of detecting Zn2+ in real water samples and imaging Zn2+ in living cells roundly.

A novel chemosensor for the distinguishable detections of Cu2+ and Hg2+ by off-on fluorescence and ratiometric UV-visible absorption.

A novel dual-functional chemosensor, derived from the conjugation of rhodamine B with a quinoline derivative (RHQ), was firstly synthesized with high efficiency and cost-effectiveness for the distinguishable detections of Cu2+ and Hg2+ via ring-opening and ring-forming mechanism. The chemosensor exhibits highly selective and distinguishable responses for Cu2+ and Hg2+ in CH3CN-H2O (4:1, v/v) with off-on fluorescence and ratiometric ultraviolet-visible (UV-Vis) absorption changes. Additionally, Cu2+ is identified by opening a rhodamine spirocycle with a UV-Vis absorption band, at around 560 nm and fluorescence turn-on. Interestingly, Hg2+ is discerned by opening the rhodamine spirocycle and by generating a new special cycle for the quinoline unit. Resultantly, there were two UV-Vis absorption bands at around 365 nm and 560 nm, which were accompanied by fluorescence turn-on. Moreover, the chemosensor can quantitatively detect Cu2+ and Hg2+ by off-on fluorescence and ratiometric UV-Vis absorption changes, respectively. Furthermore, the chemosensor with low cytotoxicity could be successfully administered to monitor Cu2+ and Hg2+ in living cells. This work may pay the way for the development of dual-functional chemosensor for quantificationally detecting metal ions in environmental and biological systems.