Comment to the paper “Development of a novel upconversion fluorescence nanosensor based on metalloporphyrin element for sensitive detection of N-nitrosodimethylamine”

A recent Research article in this journal by Ouyang and co-workers (Sens. Actuators, B 393 (2023) 134260) reported a novel cobalt porphyrin-based upconversion fluorescence nanosensor to detect N-nitrosodimethylamine. However, Ouyang et al. did not properly present the mechanism of interaction between the nanosensor and the analyte in the context of cobalt porphyrin moiety based on previous literature reports. Moreover, they did not properly determine the structure of the presented nanosensor in the context of cobalt porphyrin moiety as evidenced by our spectroscopic data and previous literature reports. In addition, the interaction of the presented nanosensor with acidic and basic species, that can be present in N-nitrosodimethylamine or can originate from the sample, was not investigated. All this puts the structure and assigned sensing ability of the porphyrin-based fluorescence nanosensor under question.