Desenvolvimento de nanofribras de policaprolactona e derivado de fluoreno para utilização como sensor óptico fluorescente na detecção de explosivos nitroaromáticos

Abstract

Polymer nanofibers produced by electrospinning are considered promising, advantageous and versatile for application as portable sensors in the detection of various chemical species. In this work, fluorescent polymer nanofibers were prepared by the electrospinning technique using polycaprolactone (PCL) as a polymer matrix and 2,2'-(9,9-dioctyl-9Hfluorene-2,7-diyl)bistiophene (FBT) as fluorophore. The so- obtained materials were characterized by scanning electron microscopy (SEM), fluorescence spectroscopy (FL), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and qualitative analysis of fluorescence extinction (quenching) towards explosive compounds of forensic interest, among them the nitroaromatic explosive TNT. The membrane formed by the PCL / FBT composite was homogeneous, with absence of visual defects and presented an uniform cyan blue light emission throughout the material, which suggests the homogeneous distribution of fluorophore into the polymer matrix. In the SEM analysis, there was an absence of structural defects and an average fiber diameter of 1046 ± 400 nm, when the 17 kV voltage was applied in the processing. The fluorescence spectra recorded that the material has fluorescent properties with emission at  = 528 nm, when excited at 400 nm. From the FTIR and DSC analysis, it was found that the addition of FBT did not significantly alter the structural characteristics of the membranes, which showed properties, similar to those of neat PCL nanofibers. In the case of thermogravimetric analysis, it was observed that the PCL / FBT composite presented a degradation process in two stages. Regarding the application as a fluorescent optical sensor, the membrane was subjected to tests against 5 compounds (TNT, HMX, PETN, emulsion and an iniciator), which were kindly provided by the laboratory of the Official Examination of Alagoas (POAL). The nanofiber exhibited the quenching mechanism after a few minutes of contact with TNT, which was visible to the naked eye with the aid of a portable UV lamp ( = 365 nm), resulting in a 32.74 % reduction in fluorescence after 12 minutes and 51.74% after 32 minutes, to  = 492 nm. Therefore, the PCL / FBT composite is pointed out as a promising material to be used as a portable fluorescent optical sensor due to its ease of electrospinning and the achieved quenching results.