Fluorinated Metal Phthalocyanines: Interplay between Fluorination Degree, Films Orientation, and Ammonia Sensing Properties.

Darya Klyamer,Sergey Gromilov,Tamara Basova,Aleksandr Sukhikh,Pavel Krasnov

doi:10.3390/s18072141

Abstract

In this work, the sensor response of MPcFx (M = Cu, Co, Zn; x = 0, 4, 16) films toward gaseous NH3 (10–50 ppm) was studied by a chemiresistive method and compared to that of unsubstituted MPc films to reveal the effects of central metals and F-substituents on the sensing properties. A combination of atomic force microscopy and X-ray diffraction techniques have been used to elucidate the structural features of thin MPcFx films deposited by organic molecular beam deposition. It has been shown that the sensor response of MPcF4 films to ammonia is noticeably higher than that of MPc films, which is in good correlation with the values of binding energy between the metal phthalocyanine and NH3 molecules, as calculated by the density functional theory (DFT) method. At the same time, in contrast to the DFT calculations, MPcF16 demonstrated the lesser sensor response compared with MPcF4, which appeared to be connected with the different structure and morphology of their films. The ZnPcF4 films were shown to exhibit a sensitivity to ammonia up to concentrations as low as 0.1 ppm, and can be used for the selective detection of ammonia in the presence of some reducing gases and volatile organic compounds. Moreover, the ZnPcF4 films can be used for the detection of NH3 in the gas mixture simulating exhaled air (N2 76%, O2 16%, H2O 5%, and CO2 3%).

Highlights

Ammonia is an important commercial chemical used to make fertilizers, household cleaners, and refrigerants, and is used to synthesize other chemicals
In our previous work [15], we studied the structure of CoPcF4 films deposited by thermal evaporation and their sensor response to ammonia
The choice of phthalocyanines of copper, cobalt, and zinc was determined by their better sensitivity to ammonia, according to the experimental data and density functional theory (DFT) calculations performed earlier by

Summary

Introduction

Ammonia is an important commercial chemical used to make fertilizers, household cleaners, and refrigerants, and is used to synthesize other chemicals. Despite its natural origin and wide distribution, ammonia is both a highly toxic and corrosive gas in its concentrated form. It is classified as an extremely hazardous substance, and is subjected to strict monitoring of its concentration in the environment, as well as in the automotive and chemical industry [1]. Interest has been escalating into the study of exhaled breath as a noninvasive method of diagnostics for bronchopulmonary, cardiovascular, gastrointestinal, and other diseases [2]. Inference can be made regarding the changes in the metabolism and about the presence of a particular disease according to changes in the ratios of substances released in human breath. An ammonia concentration of Sensors 2018, 18, 2141; doi:10.3390/s18072141 www.mdpi.com/journal/sensors

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