<p>Metalloporphyrins
are molecules capable of optically sensing targets due to their
specific reactivity. Shifts in metalloporphyrins spectra are usually
in the order of 30 nm, requiring a spectrophotometer for transducing
the analyte concentration. Mesoporous oxide thin films photonic
crystals (PC) act as optical filters, while their pores can host
molecular moieties. In this work used a metalloporphyrin, Mn<sup>III</sup>
meso-tetra(N-methyl-4-pyridyl) porphyrin (MP), to add a recognition
functionality to a PC and, at the same time, retain their pore
network, in order to develop a versatile and portable sensing device
for volatile amines. The hybrid material MP@PC was prepared by
immersion of the PC, synthesized from two mesoporous oxides with
different refractive index, 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 PC spectral window with promising
analytical parameters. The hybrid material presents enhanced sensing
capabilities compared to MP or PC 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, including the MP@PC
sensor.
The device is capable of sensing with only 1.52 μg of MP on a 1 cm<sup>2</sup>
glass slide and it is easily prepared and showed a very small
detection limit.</p>
