Iptycenes and Their Derivatives in Sensors

Abstract

Generally speaking, the higher performance fluorescent chemosensors based on the conjugated polymers could be achieved through the amplification of the inherent sensitivity of the fluorescent material (Zhou and Swager, J Am Chem Soc 117(50):12593–12602, 1995; Zhou and Swager, J Am Chem Soc 117(26):7017–7018, 1995). In the iptycene-incorporated conjugated polymers, the rigid structure of iptycene can block the p–p stacking and the excimer formation in the solid state and these features make them potential candidates for fluorescent chemosensors. In 1998, Yang and Swager (J Am Chem Soc 120(21):5321–5322, 1998) took advantage of the films of pentiptycene-based conjugated polymers 1–3 with high fluorescence quantum yields and stabilities to act as the sensing materials for fluorescent chemosensors. These fluorescent chemosensors displayed wonderful abilities for the trace detection of the electron-deficient unsaturated species such as 2,4,6-trinitrotoluene (TNT), 2,4-dinitrotoluene (DNT), and benzoquinone (BQ). Especially, the polymer 1 exhibited high sensitivity to high-explosive vapors (TNT, DNT), and repetitively great spectroscopic stability along with a fast response time. All of the excellent performances made it a commercially available device called “Fido”, which had been applied for the detection technology of robotic and hand-held explosive sniffers. The electron transfer from the excited polymer to the electron acceptors leading to the fluorescence quenching seemed to be regarded as the detection mechanism. Further studies (Yang and Swager, J Am Chem Soc 120(46):11864–11873, 1998) suggested that the electron-rich environment, good balance of the electrostatic interactions, and the porous structures in the films played the key roles in the high sensitivity. Moreover, there were also varied factors that could determine the degree of fluorescence quenching, including the porosity and thickness of the film itself, the vapor pressure and the diffusion ability of analytes, and the exergonicity of electron transfer, the strength of binding between the polymer and the analytes.