Fluoroalkylated polysilane film as a chemosensor for explosive nitroaromatic compounds

The present paper reports a new type of polymer-based chemosensor made of stiff fluoroalkylated polysilane, poly(3,3,3-trifluoropropylmethylsilane) (1), which showed a remarkable sensitivity for explosive nitroaromatic compounds (NACs), such as 2,4,6-trinitrophenol (picric acid), 1,3,5-trinitrobenzene (TNB), 2,4-dinitrotoluene (DNT), and m-dinitrobenzene (DNB), by a decrease in the photoluminescence (PL) intensity in the near-UV region with parts per million concentration of NACs in tetrahydrofuran (THF) solution and in the solid film in water. The PL intensity was completely reversible repeatedly after the removal of NACs from the thin film by rinsing with methanol (or water). A linear Stern-Volmer relationship was observed in all of the cases with high quenching constants. The PL quenching efficiency of 1 (M-n = 3.12 x 10(4), PDI = 3.6, K = 4.15 x 10(4) M-1) for picric acid is 198 times better than that of nonfluoroalkylpolysilane, poly(n-propylmethylsilane) (2) (M-n = 2.93 x 10(4), PDI = 2.1, K = 2.09 x 10(2) M-1). The weak noncovalent interaction between Si atoms of sigma-conjugated polysilane and N and/or O atoms of electron-deficient NACs may be responsible for electron transfer from the excited state of the polysilane to the electron-deficient NACs, resulting in the PL quenching of 1 in solution and in the thin film by NACs.