Nitric Oxide Sensors obtained through the entrapment of iron complexes in sol-gel matrix

Abstract

Iron(III)-diethyldithiocarbamate (Fe3DETC) or iron(III)-tetra-pentafluorophenyl porphyrin (FeTFPP) was entrapped within a silica matrix by the sol-gel process. The obtained sol-gel materials SGFeDETC and SGFeTFPP were investigated as sensors for nitric oxide (NO). UV/Vis spectra of the SGFeTFPP present a Soret band at 410 nm similar to that found in the solution. The binding of gaseous NO resulted in a red shift in the Soret absorption band (410 to 419 nm) of the FeTFPP in the matrix unlike FeTFPP:NO in solution. In the case of SGFeDETC, after addition of sodium dithionite solution and bubbling NO we have good evidence that the complex is formed. The EPR spectrum of the SGFeDETC:NO in solid form exhibited a signal similar to that found in a solution of FeDETC:NO at 77K. The UV/Vis spectrum of SGFeDETC:NO shows a band at 367 nm also found in FeDETC:NO solutions. It is observed that the FeDETC:NO is more stable entrapped in the sol-gel than in aqueous solution. In the former the EPR signal decreases by a factor of 4 after one week, in the latter in 2 days the EPR signal cannot be observed anymore.