Coated QCM Sensors Research Articles

A Study of an n-TiO<sub>2</sub> Coated QCM Sensor’s Response and Reversibility under CO<sub>2</sub> Exposure

A Study of an n-TiO<sub>2</sub> Coated QCM Sensor’s Response and Reversibility under CO<sub>2</sub> Exposure

Highly sensitive ammonia sensor based on PSS doped ZIF-8-derived porous carbon/polyaniline hybrid film coated on quartz crystal microbalance

This paper demonstrates a QCM ammonia gas sensor based on PSS-doped ZIF-8-derived porous carbon and polyaniline decorated nanocomposite (PSS/ZIF-C/PANI). The PSS/ZIF-C/PANI composite was successfully prepared by MOFs template-carbonization and in-situ polymerization. The morphology and structure composition of the prepared samples were completely tested by various material characterization methods. The ammonia sensing properties of PSS/ZIF-C/PANI coated QCM sensor at room temperature were systematically studied. Experimental results show that the sensor possesses quite sensitivity (5.67 Hz/ppm), excellent linearity, high response/recovery capability (28 s/17 s) and selectivity towards ammonia. Meanwhile, the electrical parameters and quality factor of QCM were verified by impedance analysis. Furthermore, the potential ammonia adsorption mechanism can be mainly related to the synergistic effect of composite nanomaterials. This work confirms that the PSS/ZIF-C/PANI composite provides a new avenue for QCM ammonia sensing, and the sensor is expected to become a potential candidate for ammonia detection.

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 United States Environmental Protection November 2002 M. Pinheiro, E. Touraud, and O. Thomas, Dye. Pigment., 61, 121–139 (2004) http://www.sciencedirect.com/science/article/pii/S0143720803002092. 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. Önal, Food Chem., 103, 1475–1486 (2007) http://www.sciencedirect.com/science/article/pii/S0308814606006972. E. Speight and M. A. Cooper, J. Mol. Recognit., 25, 451–473 (2012) https://doi.org/10.1002/jmr.2209. Zhang and K. S. Suslick, J. Am. Chem. Soc., 127, 11548–11549 (2005) https://doi.org/10.1021/ja052606z. 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

Comparative Study of a Sensing Platform via Functionalized Calix[4]resorcinarene Ionophores on QCM Resonator as Sensing Materials for Detection of Heavy Metal Ions in Aqueous Environments

AbstractA flow type quartz crystal microbalance with impedance analysis capability (QCM‐I) chemical sensor was tested for heavy metal (HM) ions detection in aqueous solutions. The sensor development is based upon the complexing ability of the functionalized AT‐cut quartz resonator gold surface, by calixresorcinarenes, towards the HM ions. These calixresorcinarenes coated QCM sensors were tested for selectively adsorbing HM ions, such as copper, lead, mercury, and cadmium, from solution over a wide range of concentration (5‐1000 ppm) through complexation with functional groups in the coating layers. QCM‐Calix based chemosensors, C‐dec‐9‐en‐1‐ylcalix[4]resorcinarene (ionophore I), C‐undecylcalix[4]resorcinarene (ionophore II), C‐dec‐9‐enylcalix[4]resorcinarene‐O‐(S‐)‐α‐methylbenzylamine (ionophore III) and C‐dec‐9‐enylcalix[4]resorcinarene‐O‐(R+)‐α‐methylbenzylamine (ionophore IV), were synthesized and immobilized to detect HM ions of Pb2+, Cd2+, Hg2+, and Cu2+ in aqueous solutions. Using the impedance analysis, which facilitates a complete description of the acoustic loading of the crystal surface, the full width at half maximum of the QCM resonance peak (FWHM) values are obtained from the impedance spectra. FWHM variations revealed the effectiveness of the proposed ionophores in detecting HM at different levels. Sensitivities and wide linear relationships between HM concentration and FWHM were interpreted. Detection limits of (0.32, 0.57, 0.37, 0.89 ppm) and (1.63, 0.18, 0.76, 0.2 ppm) were determined for ionophore I and II, for Cd2+, Cu2+, Hg2+ and Pb2+ ions, respectively. Ionophore (I) showed binding preferences towards Cd2+ ions where ionophore (II) produced similar selectivity toward Cu2+ and Pb2+ ions. Ionophores III and IV were used for the assessment of ▵FWHM values to comprehend the detection affinities of the ionophores toward HM ions.

In-situ polymerization of metal organic frameworks-derived ZnCo2O4/polypyrrole nanofilm on QCM electrodes for ultra-highly sensitive humidity sensing application

A metal organic frameworks (MOFs)-derived ZnCo2O4/polypyrrole (ZnCo2O4/PPy) nanocomposite coated QCM humidity sensor with high performance was demonstrated in this paper. The element composition, morphology and nanostructure of the ZnCo2O4/PPy nanocomposite were characterized by energy dispersive spectroscopy (EDS), FT-IR spectrums, X-ray diffraction (XRD), scanning electron microscopy (SEM), and atomic force microscopy (AFM). All humidity sensing tests of ZnCo2O4/PPy QCM sensor were performed under room temperature environment. The experimental results revealed that the ZnCo2O4/PPy sensor exhibits excellent humidity sensing behavior. Comparing with pure PPy and pure ZnCo2O4 sensor, ZnCo2O4/PPy film coated QCM humidity sensor displays higher sensitivity (58.4 Hz/%RH) and better response/recovery properties (8 s/7 s). Besides, the equivalent circuit elements parameters of ZnCo2O4/PPy coated QCM sensor at various RH environments were determined by the modified Butterworth-Van-Dyke (BVD) equivalent circuit model. And the adsorption kinetics of water molecules was investigated by bimodal exponential kinetic adsorption model.

QCM sensors coated with calix[4]arenes bearing sensitive chiral moieties for chiral discrimination of 1-phenylethylamine enantiomers

This article describes the enantiomeric discrimination properties of new chiral calix[4]arene derivatives bearing (S)-/(R)-1-phenylethylamine moieties (5a and 5b, respectively) towards the 1-phenylethylamine enantiomers on QCM surface. Initial experiments demonstrated that the 5b coated QCM sensor was the most effective sensing material for enantiomeric discrimination of (R)-/(S)-1-phenylethylamine by exhibiting much more sensing ability towards (R)-enantiomer than (S)-enantiomer. Sensitivity, detection limit and time constant of the 5b coated QCM sensor has been were calculated as 0.082 Hz/µM, 2.7 µM, and 319.2 s, respectively. Additionally, effects of calixarene content and different coating technique on enantiomeric discrimination, and Langmuir and Freundlich isotherms of the sensing results also were studied. As a result, it has been demonstrated that the coating of QCM sensor with a chiral calix[4]arene (5b) having (S)-1-phenylethylamine moieties provides substantially enantiomeric discrimination of 1-phenylethylamine enantiomers.

Sensing abilities of functionalized calix[4]arene coated QCM sensors towards volatile organic compounds in aqueous media

This study presents the sensing studies of QCM sensors which coated with calix[4]arene derivatives bearing different functional groups towards some selected Volatile Organic Compounds (VOCs). Initial experiments revealed that QCM sensor coated with calix-3 bearing bromopropyl functionalities was relatively more effective sensor for methylene chloride (MC) emissions than the other calix[4]arene coated QCM sensors, in aqueous media. In further experiments, this effective calix-3 coated QCM sensor were used in detailed sensing studies of selected VOCs. However, the results demonstrated that calix-3 coated QCM sensor was most useful sensor for toluene (TOL) emissions among all. Moreover, the sensing of TOLs with calix-3 coated QCM sensor was also evaluated in terms of sorption phenomena. Consequently, calix-3 coated QCM sensor was good sensor for TOL emissions, and thus it demonstrated that the coating of QCM sensor surface with calixarenes was good approach for sensing of the VOCs.

Calix[4]arene coated QCM sensors for detection of VOC emissions: Methylene chloride sensing studies

This paper describes the sensing studies of QCM sensors with coated some calixarene derivatives bearing different functional groups for some selected Volatile Organic Compounds (VOCs) such as acetone, acetonitrile, carbon tetrachloride, chloroform, methylene chloride (MC), N,N-dimethylformamide, 1,4-dioxane, ethanol, ethyl acetate, xylene, methanol, n-hexane and toluene. The initial experiments have revealed that whole the calix[4]arene modified QCM sensors exhibited strongest sensing ability to MC emissions. Thus, the detailed studies were performed for only MC emissions after the determination of relatively more effective calix-coated QCM sensors for MC emissions in aqueous media. The results demonstrated that QCM sensor coated with calix-7 bearing both amino and imidazole groups was most useful sensor for MC emissions with 54.1ppm of detection limit. Moreover, it was understood that cyclic structures, H-bonding capabilities and also good preorganization properties of calixarene derivatives played an important role in VOC sensing processes.

Selective detection of trace p-xylene by polymer-coated QCM sensors

Two types of polymer-coated QCM sensors were developed, which exhibited high sensitivity, stability and selectivity for the detection of trace p-xylene vapor in air over toluene, butyl acetate and 1-butanol, which are usually produced in the coating process of films on the back of solar cell array. The polymers were poly(4-vinylbenzyl chloride) (PVBC) and poly(4-vinylbenzyl chloride-co-methyl methacrylate) (P(VBC-co-MMA)), respectively. Both PVBC and P(VBC-co-MMA)-coated QCM sensors were reusable and can be reactivated by releasing the adsorbed vapor in vacuum. The QCM data also indicated that the incorporation of MMA can enhance the sensitivity of the polymer-coated QCM sensor toward p-xylene vapor. The lowest detection limit can reach 54ppm for the QCM sensor coated with 119nm thick P(VBC-co-MMA) thin film, leading to the frequency shift of 9.6Hz (−ΔF3). These two types of polymer-coated QCM sensors may find potential application in the monitoring and controlling the concentration of p-xylene vapor in the coating process of thin films on the back of solar cell array, ensuring the health of the related personnel in the factory of solar cell array.

Selective detection of trace 1-butanol by QCM sensor coated with copolymer P(HEMA- co-MA)

A novel copolymer P(HEMA- co-MA) was successfully designed and synthesized for the fabrication of copolymer-coated QCM sensors to detect vapor of organic pollutant in air. The QCM results indicated that the P(HEMA- co-MA)-coated sensors exhibited high sensitivity, stability and selectivity for the detection of 1-butanol vapor in air over toluene, p-xylene and butyl acetate, which are usually produced in the coating process of films on the back of solar cell array. The lowest detection limit of 1-butanol can reach 72 ppm, which can result in the frequency shift of 4.0 Hz (Δ F 3) for the QCM sensor coated with 161 nm thick P(HEMA- co-MA) thin film. Furthermore, such P(HEMA- co-MA)-coated QCM sensor was reusable and can be reactivated by releasing the adsorbed vapor in vacuum. These P(HEMA- co-MA)-coated QCM sensor may have potential application in the monitoring and controlling the concentration of 1-butanol vapor in the factory of back-film producer of solar cell array, which may be helpful for the healthy of the related personnel in the production of solar cell array.

Characteristics and Mechanism for Host–Guest Recognition of Isopropanol Vapor Based on Calixarene Supramolecules

The adsorption characteristics of four calixarene supramolecular compounds, like RCT, PCT, MRCT, and TBCA, as coating materials of quartz crystal microbalance sensors responding to isopropanol vapor have been investigated in this paper. The results showed that the RCT was the best coating material for isopropanol vapor when the coating mass reached 20.41 μg. The frequency shift of RCT coated QCM and the concentration of isopropanol vapor had a good linear relationship and sensitivity. Comparing with the gas chromatography, the QCM sensor could be well used for the determination of isopropanol vapor with a recovery rate of 95.22~108.1 %, and the two methods showed a well consistent examination result. Also, the sensor possessed good reversibility, reproducibility and stability, indicating that the RCT coated QCM sensor can be applied for the detection of the atmospheric polutant of isopropanol vapor in practice. The mechanism of the calixarene derivative for recognition of the isopropanol molecule has been preliminarily discussed.

Detection of heavy metal ions in aqueous solution by P(MBTVBC- co-VIM)-coated QCM sensor

A novel copolymer P(MBTVBC- co-VIM) was designed and successfully synthesized for the fabrication of copolymer-coated QCM sensors to detect the heavy metal ions in aqueous solution. The copolymer P(MBTVBC- co-VIM) contains many nitrogen (N) and sulfur (S) atoms in the side groups as electron donors, which can easily form complexes with heavy metal ions. The strong interaction between the S atom and Au electrode of quartz crystal further assures the stability of copolymer thin films on the quartz crystal surface in aqueous media. The QCM results indicated that the P(MBTVBC- co-VIM)-coated sensor exhibited high sensitivity, stability and selectivity for the detection of Cu 2+ in aqueous solution. The lowest detection limit can reach 10 ppm Cu 2+ in aqueous solution, which resulted in the frequency shift of 3.0 Hz (Δ F 3/3). The P(MBTVBC- co-VIM)-coated QCM sensors had porous surface morphologies as revealed by AFM investigation. Such porous structures enhanced the surface areas of the copolymer thin films, which increased the contacting probability of N and S atoms with heavy metal ions in solution and improved the detection sensitivity of the copolymer-coated QCM sensors.

Detection of explosives vapours using a multi-quartz crystal microbalance system

This study focused on the detection of vapours of 2, 4, 6 trinitrotoluene (TNT), 2, 4 dinitrotoluene (DNT) and pentaerythrite tetranitrate (PETN) with quartz crystal microbalances operated at 100 MHz. In the selected configuration of the multi-sensors chamber, the behaviour of 4 coated QCM sensors was shown to be equivalent in presence of explosive vapours, which is a major requirement for a multi-sensors system.The high sensitivity and selectivity of the QCMs operated at 100 MHz were demonstrated. The detection signals measured with polypentiptycene coated QCMs in presence of TNT and PETN vapours were considerably increased in comparison with 9 MHz QCMs.

Anesthetic Level Prediction Using a QCM Based E-Nose

Anesthetic level measurement is a real time process. This paper presents a new method to measure anesthesia level in surgery rooms at hospitals using a QCM based E-Nose. The E-Nose system contains an array of eight different coated QCM sensors. In this work, the best linear reacting sensor is selected from the array and used in the experiments. Then, the sensor response time was observed about 15 min using classic method, which is impractical for on-line anesthetic level detection during a surgery. Later, the sensor transition data is analyzed to reach a decision earlier than the classical method. As a result, it is found out that the slope of transition data gives valuable information to predict the anesthetic level. With this new method, we achieved to find correct anesthetic levels within 100 s.

Detection of organic amines in liquid with chemically coated quartz crystal microbalance devices

Six kinds of materials, i.e. three self-assembled monolayers with terminal functional groups, a polymer incorporating acid groups, and two supramolecules of calixarene derivatives were applied as QCM sensor coatings for selective detection of organic amines in liquid phases. The specific interactions such as acid-base interaction, complexation interaction between the coating materials and analytes make the coated QCMs sensitive to organic amines in aqueous phase. The characteristics of the coated QCM sensors varied with the detection media because of the changes of the physico-chemical properties of the coating surfaces. Reversible changes in resonance frequency of the coated QCMs were found in neutral water solution for acid-base interaction and hydrogen bonding; quasi-irreversible frequency changes were found for salt-complex forming reaction in buffer solution. The relative selectivity of the analytes decreased with the increase of the hydrophobic part of the solute molecules in aqueous phases when acid-base interaction between the coating materials and analytes were employed. Shape-discrimination of analytes were achieved by the usage of supramolecules as sensor coatings owing to the cavity inclusion of the supramolecules.