Nanoarchitectonics of highly dispersed polythiophene on paper for accurate quantitative detection of metal ions.

π-Conjugated polymers such as polythiophene provide intramolecular wire effects upon analyte capture, which contribute to sensitive detection in chemical sensing. However, inherent aggregation-induced quenching causes difficulty in fluorescent chemical sensing in the solid state. Herein, we propose a solid-state fluorescent chemosensor array device made of a paper substrate (PCSAD) for the qualitative and quantitative detection of metal ions. A polythiophene derivative modified by dipicolylamine moieties (1), which shows optical changes upon the addition of target metal ions (, Cu, Cd, Ni, Co, Pb, Zn, and Hg), was highly dispersed on the paper substrate using office apparatus. In this regard, morphological observation of the PCSAD after printing of 1 suggested the contribution of the fiber structures of the paper substrate to the homogeneous dispersion of 1 ink to suppress aggregation-induced quenching. The optical changes in the PCSAD upon the addition of metal ions was rapidly recorded using a smartphone, which was further applied to imaging analysis and pattern recognition techniques for high-throughput sensing. Indeed, the printed PCSAD embedded with 1 achieved the accurate detection of metal ions at ppm levels contained in river water. The limit of detection of the PCSAD-based sensing system using a smartphone (48 ppb for Cu ions) is comparable to that of a solution-based sensing system using a stationary spectrophotometer (16 ppb for Cu ions). Therefore, the methodology based on a combination of a paper-based sensor array and a π-conjugated polymer will be a promising approach for solid-state fluorescent chemosensors.