Fabrication of a new three-dimensional Cu(II) metal−organic framework, {[Cu 4 (4,4′-bipy) 3 (OH) 2 (mal) 3 ]• 4H 2 O} n (1a; 4,4′-bipy = 4,4′-bipyridine, H 2 mal = malonic acid; P2 1 /m), that undergoes an unprecedented redox-versatile ligandsubstitution-induced single-crystal to single-crystal transformation, for smartphone-based detection of iodide was studied. The Cu-MOF 1a has been effortlessly synthesized by the microwaveheating technique. Phase formation of the Cu-MOF 1a depended on counter-anions. The transformations can be triggered by halides to corresponding coordination polymers through both non-redox and redox-associated pathways. The changes in the local structure and oxidation state of copper during the transformation were studied by ex situ and in situ synchrotron X-ray absorption spectroscopies. The selectivity of the halide-triggered transformation was investigated. A study on smartphone-based colorimetric detection of iodide was found to be linearly proportional to the iodide concentration in the range 10−1500 mg/L with a limit of detection of 5 mg/L and good precision relative standard deviation of 1.9% (n = 11), possibly to construct the iodide test kit.
A miniaturized microfluidic hydrodynamic sequential injection system for sensitive colorimetric detection was developed for performance improvement in the measurement of phosphate, nitrite, and nitrate based on molybdenum blue and Griess methods.
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