V₂O₅ Thin Film Coated QCM for Amine Sensing in Liquid Media

Amine and amine derivatives are known to have carcinogenic effects and recognized as priority pollutants on the United States Environmental Protection Agency (EPA) [1]. It is very important to detect amines, which are known to have carcinogenic effects, in natural water sources (drinking water, lakes, seas) where they can interact with humans quickly, transportably and with high sensitivity. Industrial establishments such as petroleum refineries, synthetic polymers, paints, tires, pharmaceuticals and explosives are the main sources of amine release into the nature. Hair dyes, exhaust gases, burning or degradation of protein-rich plants, and meat consumption, which are thought to cause cancer development and have been investigated intensely, can be considered as non-industrial sources of amine release [1, 2]. Although methods such as gas chromatography (GC), high performance liquid chromatography (HPLC), photometry, ion mobility chromatography, capillary electrophoresis are used to detect amine and amine derivative compounds (aromatic amines, aliphatic amines) in liquid [1, 3, 4]. These methods are very complex, require expert users and alternative techniques are being investigated due to their cumbersome structure.

The development of sensor systems in analytical chemistry for the identification and detection of organic compounds still poses a major problem. While the interest in QCM-based sensors is increasing day by day, it has become a proven transducer platform for sensing applications in liquid [5]. Sensor systems with different structures are produced to selectively detect each compound. These sensor systems need to be redesigned as they often exhibit low sensor characteristics directly in liquid. In response, Suslick et al. showed that pH indicators, solvatochromic molecules and colored metal complexes were used to decompose organic compounds in water [6]. In addition, QCM-based studies on the determination of chemical pollutants in liquid directly continue increasingly today.

The preliminary results were patented [7]. V₂O₅ thin film was deposited on one side of transducers via thermal evaporation method as active material with 20 nm thicknesses. AT-cut QCMs of 5 MHz fundamental frequency with gold electrodes were used as transducers. Structural and optical analyses of the V₂O₅ thin films were performed. SEM image of V₂O₅ thin film is given in fig. a and clearly seen that smooth surface morphology.

V₂O₅ thin film coated QCM sensor were tested to amine and amine derivatives and other chemical pollutants can be seen in nature due to some industrial process residue in water media. The tested analytes were chloramine T, butylamine, hexylamine, thrietylamine, dichloromethane, chloroform, chlorbenzene, trichlorethylene, tetrachlorethylene, p-xylene, bisphenol A, methiocarb, propoxur, triadimenol, tebuconazole, iprodine and triadimefon. Sensor tests were performed with QCM-Z500 (KSV Instruments, Finland) device which has thermostated measurement system for a single QCM sensor. The KSV QCM-Z500 device determines the resonance frequency of the quartz crystal in the liquid in the frequency range of 5-55 MHz and the quality factor (Q) of the resonance by impedance analysis.

Typical real-time sensor response of the QCM sensor coated with V₂O₅ to chloramine in water can be seen in fig b. The frequency variation changes rapidly in the negative direction when the analyte is sent to the test cell and reaches its maximum value. The average response time (t₉₀) of the developed sensor all concentrations tested is around 3s. In addition, it is seen that the test cell quickly returns to the baseline with the sending of pure water and it is seen in fig b that there is no drift at the baseline level during the whole test. The sensitivity of the developed sensor against chloramine T in water is calculated as 12 Hz/ppm and the limit of detection (LOD) value is 80 ppb. The LOD value is 50 times below the limit value specified in the EPA standards. The developed sensor was selectively respond to amine derivatives.

References

1. United States Environmental Protection November 2002

2. M. Pinheiro, E. Touraud, and O. Thomas, Dye. Pigment., 61, 121–139 (2004) http://www.sciencedirect.com/science/article/pii/S0143720803002092.

3. G. Snyderwine, R. Sinha, J. S. Felton, and L. R. Ferguson, Mutat. Res. Mol. Mech. Mutagen., 506–507, 1–8 (2002) http://www.sciencedirect.com/science/article/pii/S002751070200146X.

4. Önal, Food Chem., 103, 1475–1486 (2007) http://www.sciencedirect.com/science/article/pii/S0308814606006972.

5. E. Speight and M. A. Cooper, J. Mol. Recognit., 25, 451–473 (2012) https://doi.org/10.1002/jmr.2209.

6. Zhang and K. S. Suslick, J. Am. Chem. Soc., 127, 11548–11549 (2005) https://doi.org/10.1021/ja052606z.

7. Erbahar, et. al, Use of piezoelectric transducers modified with metal oxide-based thin films for direct detection of amine derivatives in liquid media, (2018) US20180080902A1.

Figure 1