Triethylamine sensors

The sensors were exposed to the following VOC n-pentane, methanol, benzene, triethylamine and acetic acid. 

Other sensors are mostly grouped towards the triethylamine. In the case of porphyrins 6-8, 13 the coordinated metal is no longer able to drive the selectivity pattern and the presence of the peripheral alkyl chains completely shadows the coordination interactions. This result can explain the failure to observe the coordination interaction in the sensing mechanism of the metal complexes of the closely related alkyl chains functionalized phthalocyanines reported in the past by Gopel and coworkers [22]. 

There are shortcomings in this work, however, and we expect to solve these soon. Adsorption is a slower process than most of us realize (25), and at 25°C the adsorption of pyridine onto iron oxide takes about three days to reach equilibrium. The results of Figure 7 with pyridine and those with triethylamine were obtained in about one hour. However Fm was the same for the two temperatures, for the slopes are exactly equal for the two lines. We are now using a flow microcalorimeter to measure the evolution of heat upon adsorption and we are adding a UV sensor to detect concentration changes this combination should give accurate heats of adsorption and desorption. We will then be able to compare these direct measurements of heats of adsorption with those obtained from the temperature coefficients of adsorption isotherms. 

Composites of PANI-NFs, synthesized using a rapid mixing method, with amines have recently been presented as novel materials for phosgene detection [472]. Chemiresistor sensors with nanofibrous PANI films as a sensitive layer, prepared by chemical oxidative polymerization of aniline on Si substrates, which were surface-modified by amino-silane self-assembled monolayers, showed sensitivity to very low concentration (0.5 ppm) of ammonia gas [297]. Ultrafast sensor responses to ammonia gas of the dispersed PANI-CSA nanorods [303] and patterned PANI nanobowl monolayers containing Au nanoparticles [473] have recently been demonstrated. The gas response of the PANI-NTs to a series of chemical vapors such as ammonia, hydrazine, and triethylamine was studied [319,323]. The results indicated that the PANI-NTs show superior performance as chemical sensors. Electrospun isolated PANI-CSA nanofiber sensors of various aliphatic alcohol vapors have been proven to be comparable to or faster than those prepared from PANI-NF mats [474]. An electrochemical method for the detection of ultratrace amount of 2,4,6-trinitrotoluene with synthetic copolypeptide-doped PANI-NFs has recently been reported [475]. PANI-NFs, prepared through the in situ oxidative polymerization method, were used for the detection of aromatic organic compounds [476]. 

Finally, the surprising sensitivity of CSPT based sensors when compared with the performance of the most common transducers used as chemical sensors must be commented upon. For instance, with a standard CSPT set up, the minimum detectable amount of triethylamine absorbed in a layer of Zn-TPP is 33 femtomoles per pixel the correspondent value for the same sensing layer on a 20-MHz Quartz Microbalance is about 5 picomoles [45]. In this regard, a caveat is necessary to indicate that these figures are the resolution in terms of absorbed mass and not in terms of the concentration in air and that this also turns out to depend on the active sensor area. 

Fig. 13.7 (Top) transient signals of two QCM sensors with a vic-dioxime coating to pulses of ethyl acetate (EtOAc) vapor. (Bottom) superimposed response curves of a QCM sensor with a vic-diojdme coating to pulses of (Jeff) triethylamine (Et3N) and (right) n-propanol (nPAOH) vapors (Reprinted with permission from Harbeck et aL (2011). Copyright 2011 Elsevier)...

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