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Cyanobacterial harmful algal blooms in freshwater systems can produce cyanotoxins, such as microcystins (MCs) and nodularins (NODs), presenting serious threats to human health and ecosystems. Required routine monitoring of cyanotoxins in water samples, as posed by U.S. EPA drinking water contaminant candidate list 5 (CCL5), demands for cost-effective, reliable and sensitive MCs/NODs detection methods. We report the development of a colorimetric paper-based immunochip assisted by nanozyme catalysis with a smartphone readout system for rapid detection of cyanotoxins in water. We show that the introduction of biorthogonal click reaction enables in situ facile self-assembly of multi-layers of peroxidase-like nanozyme onto the anti-MCs/NODs monoclonal antibody. We can detect 13 variants of MCs/NODs even in the sub-microgram per liter range with detection limit of below 0.7 μg/L and satisfactory recovery percentages between 88 and 120% in different water matrices. Our technology shows a good correlation with the well-developed ELISA technology, demonstrating its great potential applications in resource-limited or less-developed regions for on-site and large-scale screening of cyanotoxins in water environment. [Display omitted] • A paper-based biochip with high sensitivity and throughput for cyanotoxins. • A layer-by-layer bioorthogonal click reaction for nanozyme amplification. • Limit of detection below 0.7 μg/L towards 13 variants of cyanotoxins. • Satisfactory recoveries in various water environments. • An entire detection cycle time of less than 60 min. [ABSTRACT FROM AUTHOR]

A novel U-shaped fiber-optic evanescent-wave fluorescent immunosensor was designed that exploits light-sheet excitation of skew rays in a passive fiber for sensitive microcystin-LR (MC-LR) detection in real-time. In particular, a light sheet comprising a thin plane of light can be concentrated into exciting the optimum ray group, resulting in enhanced interaction between light and fluorophores. Meanwhile, skew rays excited by transmitting light into an optical fiber with an angle offset allow a much higher number of total-internal-reflections with increased interaction length along the fiber interface, which strengthens the light-matter interactions. Under the optimal angle offset, the proposed evanescent wave fluorescent immunosensor is the first demonstration of integrating light-sheet skew rays and a U-shaped fiber-optic probe for enhanced sensitivity. The results show that fluorescence sensitivity of the U-shaped fiber-optic probe with light-sheet skew rays excitation is 16 times higher than that of collimated skew rays excitation. Combined with this newly designed light-sheet skew rays enhanced U-shaped fiber-optic fluorescent immunosensor, a sensitive and real-time MC-LR detection method was established based on the indirect competitive immunoassay principle. Real environmental water samples spiked with MC-LR were determined by the immunosensor with recovery rates between 85% and 112%. The present system could be an alternative tool for the on-site environmental monitoring, in-field food safety assurance and clinical diagnostics. It also advances the fiber-optic sensors field in terms of experimental design. 1. The first to apply light-sheet excitation of skew rays in optical fiber based evanescent wave fluorescent immunosensor for immunoassay towards MC-LR in water samples. 2. Fluorescence sensitivity of the U-shaped fiber-optic probe with light-sheet skew rays excitation is 16 times higher than that of collimated skew rays excitation. 3. An indirect competitive immunoassay is adopted for sensitive real-time microcystin-LR (MC-LR) detection. 4. Application of this system was confirmed with high recoveries in real environmental water samples. 5. Optical fiber surface can be reused for about 100 times. [ABSTRACT FROM AUTHOR]

The α-MoO 3 -based materials have been intensively investigated as chemiresistive-type gas sensors due to their excellent sensing performances for gas sensing applications. However, there still remains formidable challenges for developing a simple and scalable approach to synthesize α-MoO 3 with controllable structures. Herein, we demonstrated a glucose-assisted combustion synthesis strategy for the synthesis of α-MoO 3 materials with controllable structures. They were obtained by heat treatment of the gels containing ammonium heptamolybdate tetrahydrate and glucose. Owing to the coordination interactions between glucose and heptamolybdate, α-MoO 3 -2 sample obtained by adding 1.8 g of glucose featured the highest oxygen vacancy concentration with an O/Mo atomic ratio of 2.61. The gas sensing measurements indicated that α-MoO 3 -2 had excellent sensing performances for detecting ethanol. Such ethanol sensor displayed the lowest detection concentration of 5 ppm ethanol, high response of 3.86 toward 20 ppm ethanol, and wide detection range of 5–100 ppm. This study sheds light on preparation of metal oxides with controllable structures on a scalable way for various applications. • A glucose-assisted combustion synthesis method have been developed to preparation of MoO3 samples. • The MoO3 sample thus obtained possesses high oxygen vacancy concentration and surface chemical-adsorbed oxygen species. • The MoO3 sample exhibits excellent sensing performances for ethanol sensing. [ABSTRACT FROM AUTHOR]