Porous silicon microcavities with embedded conjugated polymers for explosives detection

Abstract

It is known that development of optical sensors for explosives detection is currently of great interest. Among others sensors based on the luminescence quenching of conjugated polymers caused by photoinduced electron transfer have attracted considerable attention. Embedding such polymers into porous silicon (pSi) microcavity (MC) allows modify its luminescence spectrum and increase specific surface area and sensitivity of sensor. At the same time optimization of pSi MC structure and its mode of operation are important aspects of sensors design. This study presents the results of the structure and temperature optimization of pSi MC with embedded PPV derivatives polymers. The pSi MCs were fabricated using a standard electrochemical etching process. The luminescence spectra of polymers were drastically narrowed after embedding in pSi MC. It was experimentally found that optimal thickness of the front mirror is from 4 to 5 pairs of low and high porosity layers. The optimal thickness of the rear mirror is about 15 pairs of low and high porosity layers. We also discovered that temperature of pSi MC strongly influences on the rate of the polymer luminescence quenching under exposure to TNT vapors. In particular, it was shown that a decrease of MC temperature to 5° C leads to more than three times drop of quenching time. The obtained results can be applied for the design of optical sensors of explosives based on pSi MC.