Triclosan (TCS) is a bacteriostatic used in household items that promotes antimicrobial resistance and endocrine disruption effects both to humans and biota, raising health concerns. In this sense, new devices for its continuous monitoring in complex matrices are needed. In this work, sensors, based on polyelectrolyte layer-by-layer (LbL) films prepared onto gold interdigitated electrodes (IDE), were studied. An electronic tongue array, composed of (polyethyleneimine (PEI)/polysodium 4-styrenesulfonate (PSS))5 and (poly(allylamine hydrochloride/graphene oxide)5 LbL films together with gold IDE without coating were used to detect TCS concentrations (10−15–10−5 M). Electrical impedance spectroscopy was used as means of transduction and the obtained data was analyzed by principal component analysis (PCA). The electronic tongue was tested in deionized water, mineral water and wastewater matrices showing its ability to (1) distinguish between TCS doped and non-doped solutions and (2) sort out the TCS range of concentrations. Regarding film stability, strong polyelectrolytes, as (PEI/PSS)n, presented more firmness and no significant desorption when immersed in wastewater. Finally, the PCA data of gold IDE and (PEI/PSS)5 sensors, for the mineral water and wastewater matrices, respectively, showed the ability to distinguish both matrices. A sensitivity value of 0.19 ± 0.02 per decade to TCS concentration and a resolution of 0.13 pM were found through the PCA second principal component.
In the search for
alternatives to chlorine-containing gases, tetrafluoroethane,
CF3CH2F (R134a), a widely used refrigerant gas,
has been recognized as a promising substitute for dichlorodifluoromethane,
CCl2F2 (R12). When R12 is replaced by R134a,
the global warming potential drops from 8100 to 1430, the ozone depletion
potential changes from 1 to 0, and the atmospheric lifetime decreases
from 100 to 14 years. Electron interactions in the gas phase play
a fundamental role in the atmospheric sciences. Here, we present a
detailed study on electron-driven fragmentation pathways of CF3CH2F, in which we have investigated processes induced
by both electron ionization and electron attachment. The measurements
allow us to report the ion efficiency curves for ion formation in
the energy range of 0 up to 25 eV. For positive ion formation, R134a
dissociates into a wide assortment of ions, in which CF3
+ is observed
as the most abundant out of seven ions with a relative intensity above
2%. The results are supported by quantum chemical calculations based
on bound state techniques, electron-impact ionization models, and
electron-molecule scattering simulations, showing a good agreement.
Moreover, the experimental first ionization potential was found at
13.10 ± 0.17 eV and the second at around 14.25 eV. For negative
ion formation, C2F3
– was detected as the only anion formed,
above 8.3 eV. This study demonstrates the role of electrons in the
dissociation of R134a, which is relevant for an improvement of the
refrigeration processes as well as in atmospheric chemistry and plasma
sciences.
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