Metalloporphyrins into mesoporous photonic crystals: towards molecularly-tuned photonic sensing devices

Abstract Metalloporphyrins are molecules capable of optically sensing targets due to their specific reactivity, and mesoporous photonic architectures can act as environment-responsive materials. In this work, we used a metalloporphyrin, MnIII meso-tetra(N-methyl-4-pyridyl) porphyrin (MP), to add a recognition functionality to a mesoporous oxide photonic crystal (MOPC) in order to develop a versatile and portable sensing device for volatile amines exploiting both the open MOPC pore network and the high affinity of volatile amino analytes to the MP. The hybrid material MP@MOPC was prepared by immersion of the MOPC, synthesized from mesoporous silica and titania layers, in an MP solution. The system was characterized by UV-Vis absorption and FTIR spectroscopies, and SEM microscopy. Sensing of small molecules was tested using ethylenediamine (EDA) as a volatile amine model, showing an absorbance increase in the MOPC spectral window with promising analytical parameters. The hybrid material presents enhanced sensing capabilities compared to the MP or MOPC components alone. A prototype device was built, aiming for a future design of simple, low-cost equipment, with a light emitting diode and a light-dependent resistor, which includes the MP@MOPC sensor.