ABSTRACT
Ionogel are versatile materials, as they present the electrical properties of ionic liquids and also dimensional stability, since they are trapped in a solid matrix, allowing application in electronic devices such as gas sensors and electronic noses. In this work, ionogels were designed to act as a sensitive layer for the detection of volatiles in a custom-made electronic nose. Ionogels composed of gelatin and a single imidazolium ionic liquid were doped with bare and functionalized iron oxide nanoparticles, producing ionogels with adjustable target selectivity. After exposing an array of four ionogels to 12 distinct volatile organic compounds, the collected signals were analyzed by principal component analysis (PCA) and by several supervised classification methods, in order to assess the ability of the electronic nose to distinguish different volatiles, which showed accuracy above 98%.
ABSTRACT
As consumption of fish and fish-based foods increases, non-destructive monitoring of fish freshness also becomes more prominent. Fish products are very perishable and prone to microbiological growth, not always easily detected by organoleptic evaluation. The analysis of the headspace of fish specimens through gas sensing is an interesting approach to monitor fish freshness. Here we report a gas sensing method for monitoring Tilapia fish spoilage based on the application of a single gas sensitive gel material coupled to an optical electronic nose. The optical signals of the sensor and the extent of bacterial growth were followed over time, and results indicated good correlation between the two determinations, which suggests the potential application of this simple and low cost system for Tilapia fish freshness monitoring.
ABSTRACT
The cooperative assembly of biopolymers and small molecules can yield functional materials with precisely tunable properties. Here, the fabrication, characterization, and use of multicomponent hybrid gels as selective gas sensors are reported. The gels are composed of liquid crystal droplets self-assembled in the presence of ionic liquids, which further coassemble with biopolymers to form stable matrices. Each individual component can be varied and acts cooperatively to tune gels' structure and function. The unique molecular environment in hybrid gels is explored for supramolecular recognition of volatile compounds. Gels with distinct compositions are used as optical and electrical gas sensors, yielding a combinatorial response conceptually mimicking olfactory biological systems, and tested to distinguish volatile organic compounds and to quantify ethanol in automotive fuel. The gel response is rapid, reversible, and reproducible. These robust, versatile, modular, pliant electro-optical soft materials possess new possibilities in sensing triggered by chemical and physical stimuli.
ABSTRACT
We describe the construction of an electronic nose, comprising four chemiresistive sensors formed by the deposition of thin conductive polymer films onto interdigitated electrodes, attached to a personal computer via a data acquisition board. This e-nose was used to detect biodeterioration of oranges colonized by Penicillium digitatum. Significant responses were obtained after only 24 h of incubation i.e. at an early stage of biodeterioration, enabling remedial measures to be taken in storage facilities and efficiently distinguishing between good and poor quality fruits. The instrument has a very low analysis time of 40 s.
Subject(s)
Electronics , Fruit/microbiology , Penicillium/isolation & purification , Polymers/chemistryABSTRACT
Polarization-Modulation Infrared Reflection Absorption Spectroscopy (PM-IRRAS) was employed to observe the changes in the molecular conformation of poly(2-phenyl-1,4-xylylene) (PPPX) films that occurred after exposure to organic solvent vapors. The PPPX films were supported on solid matrixes by casting, spin-coating, and Langmuir-Blodgett (LB) techniques. The results show that the polymer is sensitive to the solvent vapors, which affect some of the vibration dipole moments, as detected by PM-IRRAS. The sensitivity depends on the method employed to immobilize the polymer, with more significant changes in films formed using techniques that result in a less systematically organized conformation. This feature enables the use of surface vibration spectroscopy to detect organic solvent vapors and may be applied in an artificial nose.
