A photoluminescent switch based on the hybrid organized molecular films of decatungsteuropate and some amphiphiles

Hybrid organized molecular films composed of a polyoxometalate, decatungsteuropate (EuW10), and amphiphiles such as hexadecyltrimethylammonium bromide (CTAB), n-octadecylamine (ODA) and 4-hexadecylaniline (HDA) were fabricated by Langmuir–Blodgett (LB) technique and their photoluminescent properties were investigated. The hybrid films, which were formed through in situ complex formation at the air/water interface and subsequently transferred onto the solid substrate, were characterized by UV–vis, FT-IR, fluorescence, and AFM measurements. The transferred hybrid films showed red emission characteristic of the Eu(III) ion upon UV irradiation. The photoluminescence of the hybrid films was sensitive to the acid and base gases. When ODA/EuW10 and HDA/EuW10 hybrid films were exposed to HCl gas, their photoluminescence disappeared completely. Interestingly, the photoluminescence was recovered upon subsequent exposing the same film to NH3 gas. Such process could be repeated many times and a switch based on these hybrid films was proposed. On the other hand, the photoluminescent intensity of CTAB/EuW10 film decreased but never disappeared upon exposing to HCl gas. Similarly, the photoluminescence could also be partially recovered upon exposing to NH3 gas. Detailed investigation on the spectral changes of the films revealed that the interaction between EuW10 and CTAB and was different from EuW10 with ODA or HDA, and protonation of amine group in ODA or HDA induced by HCl gas played an important role in realizing the “on” and “off” photoluminescence switch of the hybrid films.

Hybrid organized molecular films containing decatungsteuropate are constructed by LB technique. The hybrid films showed switch-able fluorescence, which could be wiped out by HCl gas and recovered in NH3 gas atmosphere. Protonation of the amine group in amphiphiles was found to play an important role in the luminescent switch.Figure optionsDownload as PowerPoint slide