Quartz Crystal Microbalance Sensor Research Articles

Development of QCM sensor to detect α-terpinyl acetate in cardamom

α-terpinyl acetate (aTA) is an organic volatile compound present in cardamom and it majorly makes this spice gracefully flavoured. Quartz crystal microbalance (QCM) sensor with tailor-made sensitivity provides a wide range of linear responses and is generally used for aroma sensing based on the deviation of the resonant frequency. In this present work, a QCM gas sensor (aTA-MIP-QCM) has been developed by coating the quartz crystal with a molecularly imprinted polymer (MIP) containing polymethacrylic acid (PMAA) to detect α-terpinyl acetate in small cardamom. Extensive experimentation has been carried out for the study of sensitivity, selectivity, repeatability, reproducibility, and stability of the decorated sensor and the results demonstrate that the sensor is exclusively sensitive and selective to aTA. The sensor was exposed to the aroma of cardamom samples and a significant correlation was obtained of the sensor response with the gas chromatography-mass spectrometry (GC–MS) estimations.

A Fast Method for Monitoring the Shifts in Resonance Frequency and Dissipation of the QCM Sensors of a Monolithic Array in Biosensing Applications

Improvement of data acquisition rate remains as an important challenge in applications with Quartz Crystal Microbalance (QCM) technology where high throughput is required. To address this challenge, we developed a fast method capable of measuring the response of a large number of sensors and/or overtones, with a high time resolution. Our method, which can be implemented in a low-cost readout electronic circuit, is based on the estimation of $\Delta {f}_{r}$ (frequency shift) and $\Delta {D}$ (dissipation shift) from measurements of the sensor response obtained at a single driving frequency. By replacing slow fitting procedures with a direct calculation, the time resolution is only limited by the physical characteristics of the sensor (resonance frequency and quality factor), but not by the method itself. Capabilities of the method are demonstrated by monitoring multiple overtones with a single 5 MHz sensor and a Monolithic QCM array comprising 24 50MHz-sensors. Accuracy of the method is validated and compared with the state-of-the-art, as well as with a reference method based on impedance analysis.

QCM Sensor Arrays, Electroanalytical Techniques and NIR Spectroscopy Coupled to Multivariate Analysis for Quality Assessment of Food Products, Raw Materials, Ingredients and Foodborne Pathogen Detection: Challenges and Breakthroughs.

Quality checks, assessments, and the assurance of food products, raw materials, and food ingredients is critically important to ensure the safeguard of foods of high quality for safety and public health. Nevertheless, quality checks, assessments, and the assurance of food products along distribution and supply chains is impacted by various challenges. For instance, the development of portable, sensitive, low-cost, and robust instrumentation that is capable of real-time, accurate, and sensitive analysis, quality checks, assessments, and the assurance of food products in the field and/or in the production line in a food manufacturing industry is a major technological and analytical challenge. Other significant challenges include analytical method development, method validation strategies, and the non-availability of reference materials and/or standards for emerging food contaminants. The simplicity, portability, non-invasive, non-destructive properties, and low-cost of NIR spectrometers, make them appealing and desirable instruments of choice for rapid quality checks, assessments and assurances of food products, raw materials, and ingredients. This review article surveys literature and examines current challenges and breakthroughs in quality checks and the assessment of a variety of food products, raw materials, and ingredients. Specifically, recent technological innovations and notable advances in quartz crystal microbalances (QCM), electroanalytical techniques, and near infrared (NIR) spectroscopic instrument development in the quality assessment of selected food products, and the analysis of food raw materials and ingredients for foodborne pathogen detection between January 2019 and July 2020 are highlighted. In addition, chemometric approaches and multivariate analyses of spectral data for NIR instrumental calibration and sample analyses for quality assessments and assurances of selected food products and electrochemical methods for foodborne pathogen detection are discussed. Moreover, this review provides insight into the future trajectory of innovative technological developments in QCM, electroanalytical techniques, NIR spectroscopy, and multivariate analyses relating to general applications for the quality assessment of food products.

Complex characterization of human urine using super-nonwettable soot coated quartz crystal microbalance sensors

The laboratory dipstick analysis of human urine is among the frequently ordered medical tests due to the profusion of biomarkers that can be used to indicate the occurrence of health problems. Regrettably, the authenticity of these assays is compromised at low biomarker concentrations or when obtaining quantitative results is mandatory. Here, we reveal the first of its kind super-nonwettable soot coated quartz crystal microbalance (QCM) based biosensors with strong potential for in-situ quantification of human urine. Unlike the existing counterparts, the signal generated by the as-developed devices seems to reverberate the joint effect of a few biochemical components of the urine (pH, protein, urea, creatinine and uric acid) via visible changes in the rate of super-nonwetting to super-wetting state transition of the interfacial soot coating. In turn, the developed QCM sensors are endowed with the ability of recognizing subtle differences (e.g., tenths or units of mmol/L) in the urine’s biochemistry at minimized noise levels, by registering fundamentally distinct resonance responses in terms of quantitative values and course of the signal. Our invention rises additional questions, whose answer is pending, but may inspire the research society for dedicating efforts in future fabrication of facile, time-efficient and flexible platforms for complex urinalysis.

Kuvarz Kristal Mikroterazi Sensör ile İçme Sularında Kloroform Tespiti için Yüzey Modifikasyon Yöntemlerinin Değerlendirilmesi

In this study, two different surface modification methods have been tested for easy detection of chloroform, which is harmful to human health in case of excess in the mains water, with a Quartz Crystal Microbalance (QCM) sensor. In the first coating method, acidic and basic solutions of 3-mercaptopropyltrimethoxysilane (MPS) in ethyl alcohol were applied respectively. In the second coating method; Acidic MPS was applied in the first step and then surface modification was completed using 2-mercaptoethanol (ME). In Coating-1, average frequency shifts of -180(±30) Hz, -200(±40) Hz and +40(±10) Hz were recorded for acidic MPS, basic MPS and 10 ng mL chloroform, respectively. In Coating-2, chloroform molecules formed covalent bonds with thiol groups and the mean frequency shifts obtained for acidic MPS, ME and 10 ng / mL chloroform were -180(±30) Hz, -80(±15) Hz, and -70(± 8) Hz, respectively. According to empirical results, coating-2 method provided a better surface modification than coating-1 method. Resonance frequency shifts of -2.5(±1), -12(±4), -70(±8) and -356(±87) Hz respectively were obtained at chloroform concentrations of 0.1, 1, 10, and 100 ng/mL by using QCM sensor modified with MPS + ME.

Quartz crystal microbalance sensor based on 11-mercaptoundecanoic acid self-assembly and amidated nano-titanium film for selective and ultrafast detection of phosphoproteins in food

A novel quartz crystal microbalance (QCM) sensor for trace-phosphoprotein ultrafast detection was constructed based on the bridge interactions between the NH2-TiO2 sites enriched on Au-electrode and phosphate groups. Herein, 11-mercaptoundecanoic acid (MUA) modified by Au-S bond acted as carrier for immobilizing NH2-TiO2. Functionalized NH2-TiO2 to absorb phosphoproteins. Under the optimal conditions, the proposed sensor showed a linear frequency shift to the concentration of α-casein ranging from 1.0 × 10−3 to 1.0 mg mL−1 with a low detection limit of 5.3 × 10−6 mg mL−1 (S/N = 3), and the limit of quantitation was 0.001 mg mL−1. Compared with traditional Ti4+-IMAC/MOAC-system, the analysis process of NH2-TiO2/MUA/AuE-QCM sensor was simpler and faster which could complete within 5 min. Additionally, the constructed biosensor was successfully used for the non-fat milk and chicken egg white. This proposed sensor presents a great prospective strategy for the evaluation of the nutrition in different foods.

Detection of amoxicillin residues in egg extract with a molecularly imprinted polymer on gold microchip using surface plasmon resonance and quartz crystal microbalance methods.

In this study, surface plasmon resonance (SPR) and quartz crystal microbalance (QCM) sensors were prepared for the detection of amoxicillin from the commercial and local chicken eggs by using molecular imprinting technique. Amoxicillin imprinted poly(hydroxyethyl methacrylate-methacrylic acid) polymeric film was synthesized onto the surface of the SPR and QCM chips by ultra violet polymerization to determine lower concentrations of amoxicillin. Ellipsometry, contact angle analysis, and atomic force microscopy measurements were used for the surface morphology of the polymeric film layer. The ellipsometric thickness of AMOX imprinted and nonimprinted SPR and QCM chip surfaces were measured as 35 ± 0.9nm,32.89 ± 1.9nm,30 ± 0.6nm, and 28 ± 0.22nm,respectively. Contact angles of bare gold surfaces, AMOX imprinted SPR and QCM chip surfaces were measured to be as 82.3° ± 0.15, 79.2° ± 0.14, 75.01° ± 1.07, and 69.11° ± 0.89, respectively. The range of linearity was measured as 0.1 to 10ng/mL for amoxicillin imprinted SPR and QCM sensors. The maximum residue limit of AMOX in eggs is at 10µg/kg in accordance with the "Positive List System for Agricultural Chemical Residues in Foods." The response time for the test, including adsorption, desorption, and regeneration, was approximately 45min. The limit of detections for SPR and QCM sensors were found to be 0.0005 and 0.0023ng/mL, respectively. The reusabilities of amoxicillin imprinted SPR and QCM sensors were observed by the equilibration-binding-regeneration. Validation studies of the AMOX imprinted SPR and QCM sensors were performed by liquid chromatography-tandem mass spectrometry.

High Sensitivity and High Stability QCM Humidity Sensors Based on Polydopamine Coated Cellulose Nanocrystals/Graphene Oxide Nanocomposite.

In this paper, a high sensitivity and high stability quartz crystal microbalance (QCM) humidity sensor using polydopamine (PDA) coated cellulose nanocrystal (CNC)/graphene oxide (GO) (PDA@CNC/GO) nanocomposite as sensitive material is demonstrated. The PDA@CNC was prepared by the self-polymerization action on the surface of CNC, and it acted as filler material to form functional nanocomposite with GO. The material characteristics of PDA@CNC, CNC/GO and PDA@CNC/GO were analyzed by transmission electron microscope (TEM) and Fourier transform infrared spectroscopy (FTIR), respectively. The experimental results show that the introduction of PDA@CNC into GO film not only effectively enhanced the sensitivity of GO-based nanocomposite-coated QCM sensor but also significantly maintained high stability in the entire humidity range. The PDA@CNC/GO30-coated QCM humidity sensor exhibited a superior response sensitivity up to 54.66 Hz/% relative humidity (RH), while the change rate of dynamic resistance of the sensor in the humidity range of 11.3–97.3% RH is only 14% that is much smaller than that of CNC/GO-coated QCM. Besides, the effect of the PDA@CNC content on the sensitivity and stability of GO-based nanocomposite-coated QCM humidity was also studied. Moreover, other performances of PDA@CNC/GO-coated QCM humidity sensor, including humidity hysteresis, fast response and recovery and long-term stability, were systematically investigated. This work suggests that PDA@CNC/GO nanocomposite is a promising candidate material for realizing high sensitivity and high stability QCM humidity sensor in the entire humidity detection range.

Intelligent Mobile Electronic Nose System Comprising a Hybrid Polymer-Functionalized Quartz Crystal Microbalance Sensor Array.

We devised a low-cost mobile electronic nose (e-nose) system using a quartz crystal microbalance (QCM) sensor array functionalized with various polymer-based thin active films (i.e., polyacrylonitrile, poly(vinylidene fluoride), poly(vinyl pyrrolidone), and poly(vinyl acetate)). It works based on the gravimetric detection principle, where the additional mass of the adsorbed molecules on the polymer surface can induce QCM resonance frequency shifts. To collect and process the obtained sensing data sets, a multichannel data acquisition (DAQ) circuitry was developed and calibrated using a function generator resulting in a device frequency resolution of 0.5 Hz. Four prepared QCM sensors demonstrated various sensitivity levels with high reproducibility and consistency under exposure to seven different volatile organic compounds (VOCs). Moreover, two types of machine learning algorithms (i.e., linear discriminant analysis and support vector machine models) were employed to differentiate and classify those tested analytes, in which classification accuracies of up to 98 and 99% could be obtained, respectively. This high-performance e-nose system is expected to be used as a versatile sensing platform for performing reliable qualitative and quantitative analyses in complex gaseous mixtures containing numerous VOCs for early disease diagnosis and environmental quality monitoring.

Grafen Kaplı Kimyasal Sensörlerin Şişme Davranışları ve Matematiksel Modelleme

Bu çalışmada, grafen kaplı Langmuir-Blodgett (LB) ince filmlerin şişme davranışları Kuartz Kristal Mikrobalans (KKM) tekniği kullanılarak incelenmiştir. Bu filmler, bazı organik buharların (aseton, etanol ve metanol) difüzyon katsayı değerlerinin hesaplanması (Fick’in erken-zaman difüzyon kanunu kullanılarak) için oda sıcaklığında etkileşmeye bırakılmıştır. Difüzyon katsayı değerleri sırası ile aseton, etanol ve metanol için 20.43 x 10−16, 1.30 x 10−16 ve 0.91 x 10−16 cm2 s−1 olarak hesaplanmıştır. Benzer sıralama grafen kaplı KKM sensörünün tepkisi (frekans değişimi, Δf) için de aseton (342 Hz) > etanol (76 Hz) > metanol (51 Hz) olarak elde edilmiştir.

Rapid detection of d-limonene emanating from citrus infestation by Bactrocera dorsalis (Hendel) using a developed gas-sensing system based on QCM sensors coated with ethyl cellulose

D-limonene is one of the main olefin gas compounds released from citrus and its relative content changes most obviously with the infection time of Bactrocera dorsalis (Hendel). Thus, it is necessary to detect d-limonene content released from citrus, which may lead to detect the presence of early infestation by B. dorsalis in citrus. In this study, a gas-sensing system based on quartz crystal microbalance (QCM) sensors coated with ethyl cellulose (EC) was developed to detect d-limonene aromas emanating from Australian citrus. There was a linear relationship between the frequency shift and d-limonene concentrations ranging from 60 mg m−3 to 6000 mg m−3 with a determination coefficient (R2) of 0.9899, and the limit of detection for d-limonene in pure gas was 300 mg m−3. It has also been observed that the QCM sensor has better selectivity towards d-limonene aroma. Additionally, the sensor was found to be repeatable with an average R value of 96.31 %, and the lifetime of the sensor can be extended at least to one month with an acceptable drift (3.40 %) in their sensing characteristics. Furthermore, it was confirmed that there was high consistency between the QCM sensor’s response and the GC–MS for d-limonene aroma. The six VOCs contributing the most to differentiating citrus infested with B. dorsalis were identified. The gas-sensing system based on QCM sensors has potential feasibility for the rapid detection of the presence of B. dorsalis infestations in postharvest citrus.

Nanoarchitectured porous carbons derived from ZIFs toward highly sensitive and selective QCM sensor for hazardous aromatic vapors

Metal-organic frameworks (MOFs) are a versatile source of carbon nanoarchitectures in gas sensing applications (Torad et al., 2019). Herein, several types of nanoporous carbons (NPCs) have been prepared by in-situ carbothermal treatment of zeolitic imidazolate frameworks (ZIFs) under different inert atmospheres to achieve a highly sensitive discrimination of vaporized aromatic compounds. In this study, we demonstrate how different carbonization conditions under the flow of N2 or H2 gases affect the surface area and the degree of graphitization of the resulting NPCs polyhedrons, and their consequent effect on the sensing performance in terms of sensitivity and selectivity toward toxic volatile hydrocarbons. A growth of carbon nanotubes (CNTs) is observed on the surface of polyhedral NPCs after careful carbonization of ZIF crystals under H2 atmosphere. The fabricated quartz crystal microbalance (QCM) sensor with CNT-containing NPCs demonstrates increased sensitivity and selectivity towards toxic volatile aromatic hydrocarbons over the aliphatic analogues, suggesting the rich growth of hairy graphitic-like CNTs on the surface of carbon framework act as highly selective sensing antennae for vapor molecular discrimination of toxic aromatic hydrocarbons. Despite of increased selectivity towards volatile aromatic compounds, however, the surface area of CNT-rich NPCs derived from hybrid ZIFs and ZIF-67 is greatly sacrificed as compared to CNT-free NPCs from ZIF-8 polyhedron. In the case of Co-containing ZIF-67, the rich growth of hair-like CNTs, which is induced by the presence of Co, is observed during carbothermal reduction under a flow of H2 gas, thus allowing ultra-selective detection of aromatic hydrocarbons in the vapor phase, such as benzene (C6H6) and toluene (C6H5CH3) over their aliphatic analogue, c-hexane (c-C6H12) of same molecular mass, size and vapor pressure.

Determination of blood glucose parameter from human blood serum by using a quartz crystal microbalance sensor coated with phthalocyanines compounds

Determining the blood glucose level is important for the prevention and treatment of diabetes mellitus. We developed a sensor system using Quartz Crystal Microbalance (QCM) to determine the blood glucose level from human blood serum. This study consists of two experimental stages: artificial glucose/pure water solution tests and human blood serum tests. In the first stage of the study, the QCM sensor with the highest performance was identified using artificial glucose solution concentrations. In the second stage of the study, human blood serum measurements were performed using QCM to determine blood glucose levels. QCM sensors were coated with phthalocyanines (Pcs) by jet spray method. The blood glucose values of 96 volunteers, which ranged from 71 mg/dL to 329 mg/dL, were recorded. As a result of the study, human glucose values were determined with an average error of 3.25%.

Passive characterization of quartz crystal microbalance sensors in highly viscous media

The objective of this work is to perform and verify a method for the characterization of QCM sensors in passive mode using a network analyzer. The system allows the measurement of the series resonance frequency and the motional resistance of QCM resonators in highly viscous media in which the oscillators (QCM sensors in active mode) present operating problems. A calibration of the sensor system was carried out, finding sensitivities very close to the theoretical ones. The obtained results are compared with those of other authors.

A Novel Multi-purpose MIP for SPE-HPLC and QCM Detection of Carbaryl Residues in Foods

In this work, two detection methods of solid-phase extraction–high-performance liquid chromatography (SPE-HPLC) and quartz crystal microbalance (QCM) were established, based on a surface molecularly imprinted polymer material (MIP). The material can be used as a selective solid-phase extraction filler and as a coating for sensitive quartz crystal microbalances by virtue of the polyhydroxy structure of grafted silicon spheres together with the network structure from cross-linked polymerization. The adsorption properties of the prepared MIP were analysed by dynamic and static adsorption tests, and the experimental conditions for SPE-HPLC and QCM analysis were optimized. Under the optimal conditions, the linear range of MIP-SPE-HPLC for the detection of carbaryl was 0.5–60 μg L−1 (R2 = 0.99913), and the detection limit was 0.0573 μg L−1. The proposed QCM sensor displayed a linear relationship between the frequency shift and the concentration of carbaryl ranging from 5 to 80 μg L−1 with a low detection limit of 0.6845 μg L−1 (signal-to-noise ratio, S/N = 3). Through a series of experiments, it was shown that the prepared MIP has good adsorption and selectivity for carbaryl, and the MIP-based HPLC and QCM sensor can be applied to the detection of actual food samples.

Stability evaluation of quartz crystal microbalances coated with polyvinyl acetate nanofibrous mats as butanol vapor sensors

Stability is one of the crucial sensor properties to be applicable in real condition and yet hardly investigated. In this communication, we evaluated the stability of butanol vapor sensors that were constructed using quartz crystal microbalance (QCM) platforms coated with electrospun polyvinyl acetate (PVAc) nanofibers. The reliability test was performed by monitoring the sensor frequency characteristics in a long-term measurement, in which the frequency shift was found to decrease by ∼7% after the sensors have been tested for 100 times. This performance degradation was mainly attributed to the reduction of active membrane surface area caused by swelling of the nanofibers, which was confirmed by scanning electron microscopy (SEM) images. This finding does not only allow us to better understand the nanofiber-coated QCM sensor limitation and degradation process, but also to design appropriate strategies for mitigating the device stability issues.

Self-assembled graphene oxide/polyethyleneimine films as high-performance quartz crystal microbalance humidity sensors

As humidity is one of the most widely demanded environmental parameters, the precision of its detection is significant. An advanced humidity sensor will improve the validity of the humidity monitoring system. In this study, a facile chemical layer-by-layer self-assembly (CLS) method was developed for fabricating graphene oxide (GO)/polyethyleneimine (PEI) multilayer films. Owing to the chemical bonding between the PEI and GO, and the intrinsic stickiness of the PEI, layered films with different numbers of layers were successfully prepared using the CLS method and confirmed through ultraviolet–visible (UV–Vis) spectroscopy and the mass loading of quartz crystal microbalance (QCM). Morphological measurements revealed that the roughness and thickness of the films increased exponentially with the number of bilayers. The GO/PEI films were deposited on QCM electrodes using the CLS method to produce the humidity sensors. The humidity measurement results showed a high sensitivity (37.84 Hz/%RH) and rapid response/recovery (< 5 s/8 s) of the optimal sensor, which was superior to that of recently developed QCM sensors.

Zinc Oxide/Reduced Graphene Oxide Nanocomposites for Rapid Detection of Toluene Gas at Room Temperature

In this study, a nanostructured zinc oxide/reduced graphene oxide (ZnO/rGO) composite was deposited on a quartz crystal microbalance (QCM) as a toluene gas sensor at room temperature. A series of ZnO, rGO and ZnO/rGO sensing materials was fabricated and characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), and Raman spectroscopy. There was significant efficiency of the ZnO/rGO composite on the sensing performance for toluene. For specific gas fluxes, the nanostructured ZnO/rGO offered sufficient paths and region for vapor diffusion and adsorption. The sensing test results illustrated that the nanostructured ZnO/rGO composite showed significant enhancement in the frequency shifts (△f) for toluene comparing to pure ZnO and rGO. Also, the ZnO/rGO-coated QCM sensor displayed a fast response (both the response and recovery times &lt; 30 s) and reproducibility for sensing toluene gas at room temperature. We believe that the novel insights on ambient temperature gas sensing on nanostructured ZnO/rGO composite could provide a new strategy for preparing a highly efficient sensing materials.

Effect of the phase composition of iron oxide nanorods on SO2 gas sensing performance

α-FeOOH nanorods were synthesized by a facile precipitation method. γ-Fe2O3 and α-Fe2O3 nanorods were then obtained by calcining for 6 h at 200 and 600 °C in ambient air, respectively. A mass-type sensor was developed based on the different iron oxide phase compositions of α-FeOOH, γ-Fe2O3 and α-Fe2O3 coating a quartz crystal microbalance (QCM). The gas sensing properties of three as-prepared sensors were systematically examined for detecting sulphur dioxide gas (SO2) at room temperature. The effect of phase composition of iron oxide nanorods on sensing properties was also discussed. Although as-prepared iron oxides have a similar morphologic structure, the sensor based on γ-Fe2O3 exposes the highest response to SO2. The sensing results show that the γ-Fe2O3 coated QCM sensors had an extremely good performance for SO2 gas in the 2.5–20 ppm range at room temperature.

A study on the discrimination of xylene isomers vapors by quartz crystal microbalance sensors

A series of quartz crystal microbalance (QCM) gas sensors were developed for discrimination of the vapor of xylene isomers (ortho-xylene, meta-xylene and para-xylene). The investigated QCM sensors included an Au-bare sensor and those modified by self-assemble monolayer (SAM) formation by 1-butanethiol and 3-methyl-1-butanethiol in the presence of xylene isomers, as reaction solvent. The presence of the investigated thiols made a slight difference on the polarity of the sensors surface, estimated by measuring the contact angles. Although the modified sensors with 1-butanethiol were selective toward ortho-xylene vapors as that presented by Au-bare sensor, the sensitivity of the 1-butanethiol-modified sensors was significantly improved with respect to that demonstrated by the unmodified sensor. The sensors modified with 3-methyl-1-butanethiol presented different demeanor for the xylene isomers vapor. This attitude varied with the solvent used through SAM formation process. It was suggested that the observed attitude of the sensors is a reflection of the solvent effect on the structure and decoration of the formed SAM on the sensor surface and the polarity of the sensors’ surface. The results allowed suggesting the fabrication of sensitive sensor arrays for the discrimination of xylene isomers vapors.