Quartz Crystal Microbalance Sensor Research Articles

All-inorganic lead-free Cs2XCl6 (X = Hf, Zr, Te) perovskites for humidity detection

Lead halide perovskites are recently regarded as promising sensing materials owing to their sensitive surface characteristics and solution processability. However, the toxicity issue and intrinsic instability restrict their applications. Herein, lead-free Cs2XCl6 (X = Hf, Zr, Te) perovskites are employed to manufacture an environmentally friendly humidity sensor. With the assistance of quartz crystal microbalance (QCM), real-time and low-cost humidity sensors are performed. The as-prepared Cs2XCl6 (X = Hf, Zr, Te) humidity sensors exhibit ultrafast response/recovery behaviors (2.8 s/2.2 s, 3.8 s/2 s and 3.7 s/2.1 s) and considerable long-term stability (over 30 days). Furthermore, the bimodal exponential model is adopted to reveal the kinetics reactions of water molecules on the Cs2XCl6 (X = Hf, Zr, Te) coated QCM humidity sensors. All results suggest that the Cs2XCl6 (X = Hf, Zr, Te) coated QCM humidity sensors could be promising real-time humidity detection techniques.

A versatile gas transmission device with precise humidity control for QCM humidity sensor characterizations

Previously, several high-sensitivity and inexpensive humidity sensors with rapid response times have been reported. However, obtaining reliable humidity characteristics of highly sensitive devices, such as quartz crystal microbalance (QCM) sensors, requires the development of new, affordable gas transmission setups. With that in mind, we developed a novel, comprehensive gas transmission system that combined elements from two commonly used systems (saturated salts and gas mixing), which facilitated automatic gas humidity changes, reliable gas flows in closed measurement chambers, and limited the influence of the external atmosphere/pollutants. The gas transmission device performance was tested using a commercial digital hygrometer and highly sensitive QCM coated with graphene oxide for six different humidity sets in range 5.3–82.6% RH. The dynamic repeatability tests proved the superb stability of the system, as QCM frequency deviation did not exceed 2% of frequency shifts among ten switching cycles (one hour each). Therefore, this system allowed a thorough investigation of humidity sensors properties in a controlled environment with a high precision.

Effect of Electrode Thickness on Quality Factor of Ring Electrode QCM Sensor.

As a key type of sensor, the quartz crystal microbalance (QCM) has been widely used in many research areas. Recently, the ring electrode QCM sensor (R-QCM) with more uniform mass sensitivity has been reported. However, the quality factor (Q-factor) of the R-QCM has still not been studied, especially regarding the effect of electrode thickness on the Q-factor. Considering that the Q-factor is one of crucial parameter to the QCM and it is closely related to the output frequency stability of the QCM, we study the effect of different electrode thicknesses on the Q-factor of the R-QCM in this paper. On the other hand, we clarify the relationship between the electrode thickness and the Q-factor of the R-QCM. The measurement results show that the average Q-factor increases with increases in the thickness of ring electrodes generally; however, the resonance frequency of the QCM resonator decreases with increases in the thickness. The low half-bandwidth (2Γ < 1630 Hz) of the R-QCM shows that the frequency performance is good. Additionally, the R-QCM has a higher Q-factor (Q > 6000), which indicates that it has a higher frequency stability and can be applied in many research areas.

Guar Gum/Ethyl Cellulose-Polyvinyl Pyrrolidone Composite-Based Quartz Crystal Microbalance Humidity Sensor for Human Respiration Monitoring.

In this work, the guar gum (GG) and the electrospinned ethyl cellulose-polyvinyl pyrrolidone (EC-PVP) nanofibers were used as humidity-sensitive materials for fabricating a quartz crystal microbalance (QCM) sensor. Fourier transform infrared spectroscopy, scanning electron microscopy, water contact angle test, and X-ray photoelectron spectra were used to characterize the synthesized GG/EC-PVP composite material, confirming its successful preparation and good hydrophilicity. The humidity sensitivity experiments were performed at room temperature. The GG/EC-PVP-coated QCM sensor has high sensitivity (55.72 Hz/%RH) and low hysteresis (2.8% RH) in a wide relative humidity range (0-97% RH), short response/recovery time (26/2 s), excellent selectivity, good repeatability, and stability. The combined action of hydrophilic groups and porous structure enhances the humidity sensitivity. The GG/EC-PVP sensor can be used to capture and measure typical breathing patterns in different human basic emotions due to its good performance. Furthermore, a lie-detector system was also designed for judging the lying through detecting the emotional breathing pattern of the subjects.

In situ discrimination of polymorphs and phase transformation of sulfamerazine using quartz crystal microbalance

A novel strategy utilizing the quartz crystal microbalance (QCM) was developed for the in situ discrimination of polymorphic nucleation (form-I and form-II) and phase transformation of sulfamerazine (SMZ) in cooling crystallization. According to Ostwald's rule of stages, metastable form-I of SMZ is first nucleated and then shifted to stable form-II by solution-mediated phase transformation. Through surface modification with the self-assembled monolayer technique of a functional group, QCM distinctively detects the formation of the two polymorphs. The results indicated that –NH2 (among the several functional groups tested) selectively accommodated stable form-II on the QCM sensor's surface and completely prevented the adsorption of metastable form-I on the surface. Therefore, the–NH2-terminated QCM detected the formation of form-I only using the solution viscosity variation on the surface. However, it monitored the nucleation and growth of form-II via the solid mass change on the surface during the phase transformation of form-I to form-II. This strategy suggests a new and precise solution for in situ discrimination of SMZ polymorphs and their phase transformation.

Novel Trend in Development of QCM System Based on Analysis of Adsorption Kinetics

In this work, modern approach was demonstrated which is improving the performance of gas sensors that utilize the quartz crystal microbalance technique. The gas sensors based on quartz crystal microbalance (QCM) are one of the common methods using for gas sensor applications. Although, these QCM sensors posses high sensitivities, its ability to discriminate the target gas still need to develop. It does not have the ability to identify or distinguish the type of gas. The idea of this work depends on investigating and invest the kinetics of the diffusion and adsorption thermodynamics gas molecules to identify gas species. So, the relationship between the parameter of the dynamic adsorption and chemisorption thermodynamic parameter were employed to know the concentration and type of the gases. The sensor was coated Polydimethylsiloxane (PDMS) ultrathin films are prepared via spin coating system, and micro incision via lithographic methods has been created on the PDMS film. In order to enhance the selectivity of the sensor. The outcome data prove the methology was working and considerable. Nevertheless, there are insufficiency. The gas molecules distinction was made possible by analysis the response signal. In particular, observing and taking into account the difference and change in the time constant. Where note a difference in the time constant due to present of the micro-pattern layer.

Vapor Sorption-Desorption Phenomena of HD and GB Simulants from Polyurethane Thin Films on Aluminum Oxide via a Quartz Crystal Microbalance.

Protection and decontamination of surfaces after exposure to chemical warfare agents (CWAs) are of considerable interest to the homeland defense and battlespace operation communities. In this work, polyurethane was spin-coated onto aluminum oxide quartz crystal microbalance (QCM) sensors. Polyurethane film thickness was varied by altering the concentration of the polymer/chloroform solution used for spin-coating. Atomic force microscopy confirmed the formation of smooth, homogeneous films on the QCM sensor surface. Aluminum oxide QCM sensors coated with polyurethane were exposed to saturated vapors of dichloropentane (DCP), a mustard gas (HD) simulant, and dimethyl methylphosphonate (DMMP), a sarin gas (GB) simulant, and the mass uptake, diffusion coefficient, volume fraction, and partition coefficient of the simulant in the film were determined from QCM data. Results showed that both DCP and DMMP readily sorbed into the films although the mass uptake of DCP was greater than that of DMMP owing to DCP’s higher vapor pressure. Additionally, the CWA simulant uptake increased with polyurethane film thickness. Sorption diffusion coefficients were 1 × 10–13 cm2/s and 1 × 10–12 cm2/s for DCP and DMMP vapor, respectively. Simulant desorption was also measured and showed that some DMMP remained in the film/substrate system, while DCP sorption was fully reversible. Reversible desorption for both CWA simulants was relatively quick and independent over the range of film thicknesses studied, with average desorption diffusion coefficients of 2 × 10–9 cm2/s and 1 × 10–11 cm2/s for DCP and DMMP, respectively. Collectively, this study is expected to inform protection and decontamination strategies of equipment and structures upon exposure to CWAs.

Improvement in metrological performances of phthalocyanine-based QCM sensors for BTX detection in air through substituent’s effect

Molecular engineering in macrocyclic materials like metallophthalocyanines (MPc) is a powerful strategy to tune the thin film properties that can be relevant to develop high performance gas sensors. In this context, the present work reports the enhancement in BTX sensing properties of MPc-based quartz crystal microbalance (QCM) sensors through exploiting the large surface area of tertiary-butyl (ttb) substituent grafted at the periphery of CuPc. Thin films of CuPc and ttb-CuPc reveal distinct morphologies and microstructures, in which the former presents a locally organized columnar structure, while the latter has an amorphous structure, containing agglomeration of molecular clusters. Such structural variation of the MPc films has huge implications on benzene, toluene and xylenes (BTX) sensing properties of the QCM sensors, utilizing these materials as sensing layers. Responses of ttb-CuPc-based QCM sensor are amplified by ca. 4-times and response time is reduced, compared to CuPc-based sensor. Moreover, ttb-CuPc-based QCM sensor displays high repeatability, resolution better than 20 ppm, negligible hysteresis and high sensitivity with limit of detection to 2 ppm, 1 ppm and 0.7 ppm for benzene, toluene and xylenes, respectively. Such favorable metrological characteristics combined with negligible interference from other gases make this microsensors suitable for BTX detection in real environment at concentrations below the recommended guidelines.

Chitosan Coating on Quartz Crystal Microbalance Gas Sensor for Isopropyl Alcohol and Acetone Detection

The development of acoustic wave sensors was driven by the presence of modern technology. Quartzcrystal microbalance (QCM) has excellent sensing capabilitiesand has wide range ofapplications. Selection of sensing layer is crucial to ensure the performance of the QCM sensor for volatile organic compound (VOC) detection. Hence, the objective of this paper is to compare the performance of chitosan coated QCM sensor for different analyte gas: isopropyl alcohol (IPA). Finite element simulation was implemented usingCOMSOL Multiphysics to study the resonance frequency shift before and after sensing. Simulation results shows IPA detection shows a higher resonance frequency shift of 62.5 Hzcompared to acetone due to higher molar mass. Experimental work is conducted to validate the simulation results where IPA analyte gas yields in 84.8 Hz which is higher than acetone analyte gas at 41.8 Hz. The functional groups for both sensing layer and analyte gas also affects the gas detection performance. IPA analyte gas possessed hydroxyl groups that favors to hydrogen bond formation with chitosan sensing layer. Thus, the QCM sensor with chitosan as the sensing layer has the potential for VOC sensing of different molar mass and functional groups.

Immunoglobulin-Immobilized Quartz Crystal Microbalance for Staphylococcus Aureus Real-Time Detection

Quartz crystal microbalance (QCM) sensor is still a high-precision surface sensing technique. Here, we described an immunoglobulin G (IgG) biofunctionalized QCM sensor for <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Staphylococcus aureus</i> (S. aureus) sensing application. In the case of the QCM sensor, a gold-titanium (Au/Ti) electrode layer was fabricated by magnetron sputtering and sequentially immobilized with thoil self-assembled monolayer (SAM) and IgG gripper. The selectivity test showed that the rabbit IgG-based QCM sensor exhibited a good sensitivity performance. IgG immobilization optimal experiment was conducted by adjusting parameters including immobilization time, temperature, buffer pH and IgG concentration. The lower limit of detection and sensitivity of the IgG-based QCM biosensor toward <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">S. aureus</i> were suggested to be <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1.0\times {10}^{{4}}$ </tex-math></inline-formula> CFU/mL and 562.5 Hz/ng, respectively. Furthermore, the real-time monitoring and frequency response of IgG immobilization process and its sensitive adsorption behavior to <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">S. aureus</i> were performed in droplet environment. By comparison, the average sensitivity of IgG-immobilized QCM sensor in liquid phase is 2-3.5 times higher than that in air. Overall, it is indicative that IgG-based QCM sensors do have great potential for biological monitoring applications.

Synthesis and Gas Adsorption Properties of γ ‐Fe 2 O 3 Nanoparticles for Mass‐Type Sensing Application

In this study, Fe3O4 nanoparticles are prepared by the co-precipitation method. γ-Fe2O3 and α-Fe2O3 nanoparticles are obtained by calcining Fe3O4 nanoparticles for 6 h at 200 and 600 °C. The physicochemical properties of the prepared nanoparticles are investigated by field-emission scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, Brunauer–Emmett–Teller, and Barrett–Joyner–Halenda methods. The gas sensors based on a quartz crystal microbalance (QCM) coated with Fe3O4, γ-Fe2O3, and α-Fe2O3 nanoparticles are fabricated and analyzed. The as-fabricated QCM sensors displayed a high capability for detecting SO2 at room temperature. Among the sensors, the γ-Fe2O3 nanoparticles coated QCM sensor exhibited the best response. Moreover, the sensor shows good repeatability and long-term stability. The correlation between the phase composition of the iron oxide nanoparticles and SO2 sensing performance is also discussed in detail.

A lead-free K2CuBr3 microwires-based humidity sensor realized via QCM for real-time breath monitoring

Halide perovskites have recently emerged as potential humidity-detection materials due to their excellent chemical and physical properties. However, the toxicity of Pb and environmental instability of the lead halide perovskites restrict the application in humidity detection. Herein, a lead-free K2CuBr3 microwires-based quartz crystal microbalance (QCM) humidity sensor was investigated, and the application in human respiratory monitoring was developed. Coupling the high humidity sensitivity of K2CuBr3 with the high mass change sensitivity of QCM, the lead-free K2CuBr3 coated QCM humidity sensor exhibited excellent logarithmic linearity response (R2 = 0.98626, 11–95% RH). In addition, the sensor demonstrated excellent repeatability, fast response/recover time (10.63 s/4.31 s), and considerable stability. Moreover, the Fourier transform infrared spectra (FTIR) and Langmuir adsorption model were applied to reveal the corresponding humidity sensing mechanism. The results indicate the lead-free K2CuBr3-based QCM sensor reported in this work could be a promising candidate for real-time breath monitoring.

A novel metal–organic frameworks composite-based label-free point-of-care quartz crystal microbalance aptasensing platform for tetracycline detection

A novel label-free point-of-care quartz crystal microbalance (QCM) aptasensing platform based on metal–organic frameworks (MOFs) and gold nanoparticles (AuNPs) was fabricated for tetracycline (TC) detection. MOFs (HKUST-1) and AuNPs were modified onto the sensing interface of QCM sensor to enhance the sensing performance of the QCM aptasensor. TC aptamer with sulfhydryl group was fixed through Au-S bond. The recognition performance of the aptasensor was predicted and verified by the computer simulation. At the optimal conditions, the frequency change of the sensor was adopted for quantitative detection of TC. The prepared QCM aptasensor exhibited a wide linear range from 1 × 10−10 g mL−1 to 1 × 10−5 g mL−1 with low limit of detection (0.8 × 10−11 g mL−1). High sensitivity, good selectivity, acceptable recoveries (87.6–91.4%) in real samples were obtained. For the first time, MOFs were utilized in the construction of QCM aptasensing platform, providing a promising application way of MOFs in the QCM sensing.

Study on the Preparation of Estrone Molecularly Imprinted Polymers and Their Application in a Quartz Crystal Microbalance Sensor via a Computer-Assisted Design.

Computer simulations are widely used for the selection of conditions for the synthesis of molecularly imprinted polymers and can rapidly reduce the experimental cycle time and save labor and materials. In this paper, estrone molecularly imprinted polymers (E1-MIPs) are designed at the M062X/6-311+G(d,p) level with itaconic acid (IA) as the functional monomer. The imprinted molar ratio between E1 and IA was optimized, cross-linkers and solvents were screened, and the nature of interactions between E1 and IA was explored. The simulated results showed that pentaerythritol triacrylate was the best cross-linker. Meanwhile, when the imprinted molar ratio between E1 and IA was 1:4, the E1–IA complex had the largest amount of hydrogen bonds, the lowest binding energy, and the strongest stability. Using the simulation results as guidance, the E1-MIPs were prepared to modify the electrons of a quartz crystal microbalance (QCM) sensor. The experimental studies showed that the E1-MIPs-QCM sensor had the highest adsorption capacity to E1 in comparison with their analogues, and the lowest detection value of the sensor was 16.00 μg/L. The computer simulations and experimental studies could provide guidance for synthesize novel E1-MIPs materials. It also could provide important references and directions for the application of E1-MIPs.

Fullerene Rosette: Two-Dimensional Interactive Nanoarchitectonics and Selective Vapor Sensing.

The simplicity of fullerenes as assembled components provides attractive opportunities for basic understanding in self-assembly research. We applied in situ reactive methods to the self-assembly process of C60 molecules with melamine/ethylenediamine components in solution, resulting in a novel type of fullerene assemblies, micron-sized two-dimensional, amorphous shape-regular objects, fullerene rosettes. ATR–FTIR spectra, XPS, and TGA results suggest that the melamine/ethylenediamine components strongly interact and/or are covalently linked with fullerenes in the fullerene rosettes. The broad peak for layer spacing in the XRD patterns of the fullerene rosettes corresponds roughly to the interdigitated fullerene bilayer or monolayer of modified fullerene molecules. The fullerene rosettes are made from the accumulation of bilayer/monolayer assemblies of hybridized fullerenes in low crystallinity. Prototype sensor systems were fabricated upon immobilization of the fullerene rosettes onto surfaces of a quartz crystal microbalance (QCM), and selective sensing of formic acid was demonstrated as preliminary results for social-demanded toxic material sensing. The QCM sensor with fullerene rosette is categorized as one of the large-response sensors among reported examples. In selectivity to formic acids against basic guests (formic acid/pyridine >30) or aromatic guests (formic acid/toluene >110), the fullerene rosette-based QCM sensor also showed superior performance.

Affinity Recognition Based Gravimetric Nanosensor for Equilin Detection

The estrogenic hormones that are widely used in postmenopausal hormone supplements for women contaminate natural water resources. Equilin (Equ) is one of the estrogenic hormones that have a maximum contaminant level of 0.35 µg/L in the chemical pollutants list. In this study, estrogenic hormones were precisely detected in a short time by affinity-recognition-based interactions in Quartz Crystal Microbalance (QCM) sensors. The QCM sensors were modified with 11-mercaptoundecanoic acid forming a self-assembled monolayer and with amino acids, namely tyrosine, tryptophan and phenylalanine. The affinity interactions between Equ and amino acids were studied using docking tools and confirmed by QCM experiments. The LODs of Equ were obtained as 4.59, 5.05 and 6.30 ng/L for tyrosine-, tryptophan- and phenylalanine-modified QCM nanosensors, respectively, with linear dynamic detection in the range of 25–500 nM. In terms of the LOD, selectivity and sensitivity calculations, the tyrosine-modified QCM nanosensor was found to have the highest performance for Equ detection compared to the tryptophan- and phenylalanine-modified ones.

Repeatability and sensitivity of quartz crystal microbalance (QCM) sensor array modified with four sensitive materials

With continuous expansion of livestock and poultry breeding industry, the emission of harmful gases has inevitably increased which has also prompted the rapid development of research on harmful gases detection, such as quartz crystal microbalance(QCM)sensors. In this research, a gas-sensing system based on QCM sensor array modified with ethyl cellulose (EC), polyethyleneimine (PEI), tetramethylammonium fluoride tetrahydrate (TMAF), and polypyrrole (PPy) was established to detect three standard harmful gases, namely CO2, NH3, and H2S. It has been observed that the QCM sensors modified with four materials had a good repeatability and a significant response to the three standard harmful gases. Furthermore, the suitable concentrations of the sensitive materials were 20 mg/ml for EC, 10 mg/ml for TMAF, 35 mg/ml for PEI, and 7 mg/ml for PPy. The frequency shift resulted by modified mass of the sensors for the four materials with the best concentrations were 21,343.1 Hz for EC, 21,065.5 Hz for TMAF, 2736.9 Hz for PEI, and 5292.4 Hz for PPy. Additionally, there was a linear relationship between the frequency shift and the concentration of three sample gases in different ranges with a high linear fit coefficient (R2>0.92), except TMAF versus CO2. Moreover, R2 with blank quartz wafer compensation was slightly smaller than which one without compensation. Therefore, the gas-sensing system based on QCM sensor array has an ideal repeatability and recovery response to the three standard gases, and the sensitivity performance was good. This work provides basic information for the research on QCM sensor array in gas detection.

Rapid analysis to distinguish porcine and bovine gelatin using PANI/NiO nanoparticles modified Quartz Crystal Microbalance (QCM) sensor

Rapid analysis to distinguish porcine and bovine gelatin using a modified Quartz Crystal Microbalance (QCM) sensor has been studied. The PANI was deposited on the sensor surface using electropolymerization, and then nickel nanoparticles were deposited by layer by layer (LbL) technique. The modified QCM sensor's performance was compared to an unmodified sensor in porcine and bovine gelatin at neutral, acidic, and alkaline conditions. The result shows that the unmodified sensor cannot distinguish between porcine and bovine gelatin, whereas the modified QCM sensor produces a different response. Porcine gelatin shows an increasing frequency response, but in contrast, bovine gelatin decreases frequency response at the alkaline condition. The time response was 2 min with a detection limit of 51.2 ppm and 8.7 ppm for porcine and bovine gelatin, respectively. Further investigation shows that the modified sensor can analyze porcine gelatin contamination in the a mixed gelatin sample.

Identification of an efficient adsorbent for ethanol sensing at room temperature using quartz crystal microbalance

Zeolite coated quartz crystal microbalance (QCM) is proposed as an efficient sensor for the detection of ethanol at room temperature. In this work, three zeolites DaY, ZSM-5, and BEA were investigated in order to determine the most efficient adsorbent for ethanol sensing at room temperature. The sensing performances were found to be mostly influenced by the acid site density and the zeolite's pore size. The BEA coated QCM sensor exhibited the best performances with a high relative frequency shift from 9.0 × 10−7 to 2 × 10−6 for 10 ppm of ethanol. Furthermore, this sensor exhibited fast response and recovery times which makes it a suitable material for the monitoring of ethanol in the air. In addition, the ethanol diffusion order was evaluated using Fickian diffusion law and was found to be the highest for the zeolite BEA. A sensing mechanism was also proposed for the adsorption and desorption of ethanol into zeolites based on unstable protonated dimers, water and diethyle ether resides for the energy-efficient ethanol sensor.

Detection of Carvacrol Content in Oregano Essential Oil by Molecularly Imprinted Polymer Coated Quartz Crystal Microbalance Sensor

The essential oil extracted from the oregano (Origanum vulgare) is rich in phenolic compounds that have strong antioxidant and antibacterial properties. Carvacrol is the major component of oregano essential oil. The current study describes the use of a molecularly imprinted quartz crystal microbalance (QCM) sensor to detect carvacrol in oregano essential oil. For the formation of the sensing film, the surface of a quartz crystal with a silver electrode was modified by simple drop coating with a synthesized polymer solution and thermally polymerized at 95&#x00B0;C in an inert atmosphere. The polymer was synthesized by copolymerization of styrene, methyl methacrylate, acrylonitrile and divinylbenzene in an optimum ratio with template carvacrol. The analytical performance of the sensor has been observed to be reasonably good (sensitivity &#x2013; 1.24Hz/ppm) and has adequate repeatability and reproducibility. Linear calibration curves were obtained in the concentration range of carvacrol between 5&#x2013;300 ppm. The molecularly imprinted polymer structure and surface morphology were analyzed by FTIR spectroscopy, SEM and AFM. Validation of the proposed sensor with oregano essential oil samples has been performed by correlating the frequency deviation of the sensor with the estimations of carvacrol obtained from gas chromatography.