Quartz Crystal Microbalance Sensor Research Articles

Construction of Self-Assembled Polyelectrolyte/Cationic Microgel Multilayers and Their Interaction with Anionic Dyes Using Quartz Crystal Microbalance and Atomic Force Microscopy.

This study aimed to reveal the interaction between self-assembled multilayers and dye molecules in the environment, which is closely related to the multilayers’ stable performance and service life. In this work, the pH-responsive poly (N-isopropylacrylamide-co-2-(dimethylamino) ethyl methacrylate) microgels were prepared by free-radical copolymerization and self-assembled with sodium alginate (SA) into multilayers by the layer-by-layer deposition method. Quartz crystal microbalance (QCM) and atomic force microscopy (AFM) results confirmed the construction of multilayers and the absorbed mass, resulting in a decrease in the frequency shift of the QCM sensor and the deposition of microgel particles on its surface. The interaction between the self-assembled SA/microgel multilayers and anionic dyes in the aqueous solution was further investigated by QCM, and it was found that the electrostatic attraction between dyes and microgels deposited on the QCM sensor surface was much larger than that of the microgels with SA in multilayers, leading to the release of the microgels from the self-assembled structure and a mass loss ratio of 27.6%. AFM observation of the multilayer morphology exposed to dyes showed that 29% of the microgels was peeled off, and the corresponding microgel imprints were generated on the surface. In contrast, the shape and size of the remaining self-assembled microgel particles did not change.

Identification of Mint Scents Using a QCM Based E-Nose

Mints emit diverse scents that exert specific biological functions and are relevance for applications. The current work strives to develop electronic noses that can electronically discriminate the scents emitted by different species of Mint as alternative to conventional profiling by gas chromatography. Here, 12 different sensing materials including 4 different metal oxide nanoparticle dispersions (AZO, ZnO, SnO2, ITO), one Metal Organic Frame as Cu(BPDC), and 7 different polymer films, including PVA, PEDOT:PSS, PFO, SB, SW, SG, and PB were used for functionalizing of Quartz Crystal Microbalance (QCM) sensors. The purpose was to discriminate six economically relevant Mint species (Mentha x piperita, Mentha spicata, Mentha spicata ssp. crispa, Mentha longifolia, Agastache rugosa, and Nepeta cataria). The adsorption and desorption datasets obtained from each modified QCM sensor were processed by three different classification models, including Principal Component Analysis (PCA), Linear Discriminant Analysis (LDA), and k-Nearest Neighbor Analysis (k-NN). This allowed discriminating the different Mints with classification accuracies of 97.2% (PCA), 100% (LDA), and 99.9% (k-NN), respectively. Prediction accuracies with a repeating test measurement reached up to 90.6% for LDA, and 85.6% for k-NN. These data demonstrate that this electronic nose can discriminate different Mint scents in a reliable and efficient manner.

Finite element analysis on the quartz plate due to the placement of quartz crystal microbalance on printed circuit board

Quartz Crystal Microbalance (QCM) is a high sensitivity piezoelectric sensor that enables it to detect loads in the nanogram order. QCM usually consists of a thin quartz plate with an AT-cut orientation. The sensor resonance frequency and its stability are affected by the sensor parameter and its placement in the reaction cell. Previous studies have shown that the physical parameters and geometric shapes of the QCM sensor greatly affected the sensitivity and stability of the sensor. As the sensor is thin, only in the order of hundredths micrometer, pressure, or force on top of the sensor surface also affects the sensor resonance frequency. In this study, we conducted a deformation analysis due to the placement of QCM on the Printed Circuit Board (PCB). The simulation is done by Finite Element Method using ANSYS 19.2. Variations in the shape of the electrodes on the PCB and O-ring elastic modulus that used in the QCM system has been investigated O-rings that have a smaller elastic modulus that will cause greater deformation. From the two types of PCB electrodes, electrodes in the form of ¾ circular arcs give smaller deformations than electrodes in the form of ½ circular arcs. The deformation occurs in the order of 10−6 m.

Easy detection of chloroform in drinking water by quartz crystal microbalance sensor

Bu calismada, sebeke suyunda fazla bulunmasi halinde insan sagligina zararli olan kloroformun Kuvars Kristal Mikroterazi (QCM) sensor ile kolay tespiti icin iki farkli yuzey modifikasyonu yontemi denenmistir. Ilk kaplama yonteminde, 3-Merkaptopropiltrimetoksisilan’in (MPS) etil alkol icerisinde sirasiyla asidik ve bazik solusyonlari uygulanmistir. Ikinci kaplama yonteminde ise; ilk asamada asidik MPS uygulanmis ve daha sonra 2-Merkaptoetanol (ME) kullanilarak yuzey modifikasyonu tamamlanmistir. Kaplama-1’de, asidik MPS, bazik MPS ve 10 ng/mL kloroform icin sirasiyla -180(±30) Hz, -200(±40) Hz ve +40(±10) Hz ortalama frekans kaymalari kaydedilmistir. Kaplama-2’de, kloroform molekulleri tiyol gruplari ile kovalent baglar olusturmus ve asidik MPS, ME ve 10 ng/mL kloroform icin elde edilen ortalama frekans kaymalari sirasiyla -180(±30) Hz, -80(±15) Hz ve -70(±8) Hz olmustur. Ampirik sonuclara gore, kaplama-2 yontemi, kaplama-1 yonteminden daha iyi bir yuzey modifikasyonu sunmustur. MPS + ME ile modifiye edilmis QCM sensor kullanarak, 0.1, 1, 10 ve 100 ng/mL kloroform konsantrasyonlarinda, sirasiyla -2.5(±1), -12(±4), -70(±8) ve -356(±87) Hz rezonans frekansi kaymalari elde edilmistir.

GC-like Graphene-Coated Quartz Crystal Microbalance Sensor with Microcolumns.

Many research groups have been interested in the quartz crystal microbalance (QCM)-based gas sensors due to their superb sensitivity originated from direct mass sensing at the ng level. Despite such high sensitivities observed from QCM sensors, their ability to identify gas compounds still needs to be enhanced. Herein, we report a highly facile method that utilizes microcolumns integrated on a QCM gas-responsive system with enhanced chemical selectivity for sensing and ability to identify volatile organic compound single gases. Graphene oxide (GO) flakes are coated on the QCM electrode to substantially increase the adsorption of gas molecules, and periodic polydimethylsiloxane microcolumns with micrometer-scale width and height were installed on the GO-coated QCM electrode. The observed frequency shifts upon sensing of various single gas molecules (such as ethanol, acetone, hexane, etc.) can be analyzed accurately using a simple exponential model. The QCM sensor system with and without the microcolumn both exhibited high detection response values above 50 ng/cm2 for sensing of the gases. Notably, the QCM sensor equipped with the microcolumn features gas identification ability, which is observed as distinct diverging behavior of time constants upon detection of different gases caused by the difference in diffusional transfer of molecules through the microcolumns. For example, the difference in the calculated time constant between ethanol and acetone increased from 22.6 to 92.1 s after installation of the microcolumn. This approach provides an easy and efficient method for identification of single gases, and it may be applied in various advanced sensor systems to enhance their gas selectivity.

Electrospun zinc oxide nanofibers for UV sensing with quartz crystal microbalance technique

An ultraviolet (UV) sensor consisting of a zinc oxide (ZnO) nanofiber sensing membrane and a quartz crystal microbalance (QCM) was fabricated. ZnO nanofibers were prepared by electrospinning and calcination. The morphology and structure of the nanofiber sensing membrane were characterized by scanning electron microscopy and X-ray diffraction. The QCM sensor based on ZnO nanofibers was found to be sensitive to 254-nm UV light in nitrogen, oxygen and air atmospheres. When the QCM sensor was placed under UV irradiation, the resonant frequency difference rapidly decreased. When the light was removed, the frequency difference recovered until reaching 0 Hz. The stability and repeatability of the proposed ZnO nanofiber-based QCM sensor were demonstrated, and the sensing mechanism was briefly discussed.

Rational Design of Molecularly Imprinted Polymers Using Quaternary Ammonium Cations for Glyphosate Detection.

Molecularly imprinted polymers have emerged as cost-effective and rugged artificial selective sorbents for combination with different sensors. In this study, quaternary ammonium cations, as functional monomers, were systematically evaluated to design imprinted polymers for glyphosate as an important model compound for electrically charged and highly water-soluble chemical compounds. To this aim, a small pool of monomers were used including (3-acrylamidopropyl)trimethylammonium chloride, [2-(acryloyloxy)ethyl]trimethylammonium chloride, and diallyldimethylammonium chloride. The simultaneous interactions between three positively charged monomers and glyphosate were preliminary evaluated using statistical design of the experiment method. Afterwards, different polymers were synthesized at the gold surface of the quartz crystal microbalance sensor using optimized and not optimized glyphosate-monomers ratios. All synthesized polymers were characterized using atomic force microscopy, contact angle, Fourier-transform infrared, and X-ray photoelectron spectroscopy. Evaluated functional monomers showed promise as highly efficient functional monomers, when they are used together and at the optimized ratio, as predicted by the statistical method. Obtained results from the modified sensors were used to develop a simple model describing the binding characteristics at the surface of the different synthesized polymers. This model helps to develop new synthesis strategies for rational design of the highly selective imprinted polymers and to use as a sensing platform for water soluble and polar targets.

Molecularly Imprinted Polymer-Based Quartz Crystal Microbalance Sensor for the Clinical Detection of Insulin.

In this study, we reported the design of a quartz crystal microbalance (QCM) sensors for selective insulin detection. In the first step, N-methacryloyl-(L) 3-histidine methyl ester (MAH) monomer was formed a complex with insulin. Then, 2-hydroxyethyl methacrylate and ethylene glycol dimethacrylate were mixed with MAH:insulin complex. Insulin-imprinted and non-imprinted QCM sensors were synthesized by ultraviolet polymerization for the insulin detection. Insulin-imprinted QCM sensors was characterized by the contact angle measurements, atomic force microscopy and ellipsometry. Limit of detection (LOD) was found as 0.00158ng/mL for the insulin-imprinted QCM sensors. Selectivity of insulin-imprinted and non-imprinted QCM sensors was carried in the presence of glucagon and aprotinin. Insulin-imprinted QCM sensor for insulin detection was also examined in the artificial plasma.

Low-fouling CNT-PEG-hydrogel coated quartz crystal microbalance sensor for saliva glucose detection.

Saliva glucose detection based on a quartz crystal microbalance (QCM) sensor has emerged as a promising tool and a non-invasive diagnostic technique for diabetes. However, the low glucose concentration and strong protein interference in the saliva hinder the QCM sensors from practical applications. In this study, we present a robust and simple anti-fouling CNT-PEG-hydrogel film-coated QCM sensor for the detection of saliva glucose with high sensitivity. The CNT-PEG-hydrogel film consists of two layers; the bottom base PBA-hydrogel film is designed to recognize the glucose while the top CNT-PEG layer is used to restrict protein adsorption and improve the biocompatibility. Our results show that this CNT-PEG-hydrogel film exhibited a 10-fold enhancement on the detection limit compared to the PBA-hydrogel. Meanwhile, the adsorption of proteins on the surface of the CNT-PEG-hydrogel film, including bovine serum albumin (BSA), mucin (MUC), and fibrinogen (FIB), were reduced by 99.1%, 77.8%, and 83.7%, respectively. The CNT-PEG-hydrogel film could detect the typical saliva glucose level (0–50 mg L−1) in 10% saliva with a good responsivity. To sum up, this new tool with low-fouling film featuring high stability, specificity, and selectivity holds great potential for non-invasive monitoring of saliva glucose in human physiological levels.

Development of Molecularly Imprinted Quartz Crystal Microbalance (QCM) Sensor Including Two-Dimensional Hexagonal Boron Nitride (2D-hBN) Nanosheets and its Application to Ascorbic Acid Detection

A new quartz crystal microbalance (QCM) sensor based on two-dimensional hexagonal boron nitride (2D-hBN) nanosheets including molecular imprinted polymers (MIP) was formed for ascorbic acid (AA) sensing. Some characterization methods such as X-ray diffraction (XRD), scanning electron microscopy (SEM), fourier-transform infrared spectroscopy (FTIR), atomic force microscopy (AFM), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were performed for characterizations of sensor structure. After formation of AA imprinted QCM chip, AA imprinted QCM sensor showed high sensing performance and linear range of 1.00 × 10−10–1.00 × 10−7 M and detection limit (LOD) of 3.0 × 10−11 M were obtained. Finally, AA imprinted sensor was applied to plasma samples for AA analysis.

Application of Innovative Analytical Modeling for the Physicochemical Analysis of Adsorption Isotherms of Silver Nitrate on Helicenes: Phenomenological Study of the Complexation Process

The interaction between the silver ion and the cyclic aromatic molecules, namely, the helicenes, is the subject of this paper. In fact, a silver complexation system based on quartz crystal microbalance (QCM) sensor with a functional film of helicenes has been designed and developed at four temperatures. The developed system, in which the sensor response reflects the adsorption of the hexahelicene and the heptahelicene, was able to control the complexed mass of silver for each concentration. Experimental outcomes indicated that the quartz crystal coated with heptahelicene is the adequate material for silver adsorption. Then, a theoretical study has been performed through two statistical physics models (SMPG and SMRG) in order to analyze the experimental adsorption isotherms of the two helicenes at the ionic scale. The SMRG model was developed using the real gas law and was satisfactorily applied for the microscopic investigation of the hexahelicene isotherms indicating that the lateral interactions between the adsorbates are responsible of the decrease of the adsorbed quantity at saturation. The interpretation of the two models’ parameters indicated that the adsorption of the two helicenes is an endothermic phenomenon. Interestingly, the heptahelicene is recommended for silver complexation because it shows the highest adsorption energies involving chemical bonds during the complexation process. The SMPG model and the SMRG model also allow prediction of three thermodynamic functions (configurational entropy, Gibbs free enthalpy, and internal energy) which govern the adsorption mechanism of silver on the two helicenes.

A humidity sensing and respiratory monitoring system constructed from quartz crystal microbalance sensors based on a chitosan/polypyrrole composite film

This paper reviews the experimental device and results of the CS/PPy QCM humidity sensor. An app was designed to accurately determine the type of breathing and demonstrate the potential respiratory monitoring of patients.

Ultra thick polystyrene coating on quartz crystal microbalance sensor

Abstract Quartz Crystal Microbalance (QCM) sensor coating layer as selective and sensitive material was usually made in a thin layer to avoid any damping effect on the sensor. The coating thickness in the range of nanometer was typical. The used of a thick polymer coating was known in the range of less than 3 μm. Usually the coating layer was prepared to support the QCM sensor to work as a mass sensitive device based on the Sauerbrey equation. A targetted biomolecule or chemical molecule was seen as a pure deposited mass on top of the sensor in the vertical direction. In our work, an ultra-thick polystyrene coating was done. The polystyrene film was formed using a spin coating method. A high concentration of polystyrene solved in toluene was used for the coating. The impedance spectrum of the QCM sensor before and after coating was measured. The fundamental resonance frequency of the sensor changed bigger than 2% and less than 5% of its initial frequency. We observed that the coating contributed little effect to the electrical impedance of the QCM sensor. The calculated film thickness was up to 8.8 μm, which was ten times thicker than the typical film coating used on a QCM sensor. The impedance of the sensor shows that the coating was still considered as glassy film.

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.