Preparation and characterization of hydrophobic porphyrin nanoaggregates dispersed in polyvinyl alcohol films

Abstract

It is known that among other applications porphyrin aggregates can be used in the detection of volatile organic compounds (VOC) and gases and vapors in general. However, the use of porphyrins for this purpose has been limited by the fact that usually the porphyrin and the polymer employed as a matrix are soluble in different media, such as polyvinyl alcohol and tetraphenylporphyrin, respectively. In this paper, we discuss how starting from stable aqueous solutions of hydrophobic porphyrins one can use the drop coating method to prepare polyvinyl alcohol polymer matrices containing porphyrin aggregates. The resulting solid films were characterized by optical techniques, and we have used UV-vis absorption spectroscopy to analyze how they interact with vapors of HCl , NO2 and NH3 .

Elucidating the Reaction Kinetics of Hydrophobic Porphyrin Nanoaggregates Dispersed in PVA Films Exposed to HCl Vapors

“…The resulting films had a thickness of about 5 μm. A closed gas chamber where the PVA/porphyrins films were exposed to an atmosphere containing vapors emanating from concentrated solutions of the reagent of interest (HCl) was adopted . The experiment was performed at room temperature after the chamber was saturated with HCl vapor, a situation attained within less than 10 min.…”

“…where γ 5 [ZnTPP] t=0 0.70 ± 0.02, and k 3 = (0.36 ± 0.05) min −1 . As for the 444-nm TPPH 2+ 4 · 2Cl − absorbance, the best fitting expression is…”

“…In a previous work, we reported the preparation of films of hydrophobic porphyrinic nanoaggregates dispersed in polyvinyl alcohol (PVA), which presented promising potential for application as optical gas sensor for HCl and NO 2 [5]. In the present work, we examine in more detail the properties of two of the porphyrins previously employed by us (5,10,15,20tetraphenylporphyrin (TPPH 2 ) and zinc 5,10,15,20tetraphenylporphyrinate (ZnTPP)), looking for a better understanding of the mechanism by which the HCl gas molecules interact with the porphyrin rings.…”

“…Porphyrins present absorption and fluorescence bands in the visible region that are associated with electronic transitions involving the aromatic electronic distribution. Interactions of analytes with porphyrin nanoaggregates affect both the optically active transitions of single porphyrin molecules and the π–π interactions between neighboring macrocycles, giving rise to detectable changes in the optical absorption and emission spectra . Also, the use of hydrophobic nanoaggregates as active materials can favor a sensor's performance, since their reduced size and elevated surface/volume ratio contribute to foster a large number of parallel reactions.…”

A fluorescent and colorimetric sensor based on a porphyrin doped polystyrene nanoporous fiber membrane for HCl gas detection

“…[11][12][13] Porphyrin is a common organic dye and has attracted much interest as the uorescent sensing materials for toxic gas detection due to its highly conjugated p-electron structure, distinctive uorescence bands in the visible region as well as selectivity of the designated gas. [14][15][16] Most of these porphyrinbased optochemical sensors mainly incorporate porphyrin into glasses, sol-gel, solid state lms, etc. [17][18][19][20][21][22] It is well known that the efficiency of these gas sensor is greatly dependent on the structure of the sensing materials.…”