QCM Gas Sensor Research Articles

Diabetes Detection Using Carbon Nanomaterial Coated QCM Gas Sensors and a Convolutional Neural Network through Urine Sample

Diabetes Detection Using Carbon Nanomaterial Coated QCM Gas Sensors and a Convolutional Neural Network through Urine Sample

Tin sulfides heterostructure modified quartz crystal microbalance sensors with high sensitivity for hazardous trimethylamine gas

P-type SnS and n-type SnS2 can form SnSx heterostructure and the unique structure has been proved to possess better sensing properties. In this work, a series of SnSx was synthesized by a one-step hydrothermal method at different S/Sn molar ratios. And the QCM transducer provided a platform for SnSx samples to realize high sensitivity detection of TMA gas at low concentration (below 10 ppm threshold limit). The TMA sensing sensitivity improved as the content of SnSx heterostructure increased in 40 % RH at 25 ℃. The SnSx prepared in the S/Sn ration of 6 exhibited the best sensitivity (−22.29 Hz/ppm), good selectivity and stability with the limit of detection (LOD) of 770 ppb, suggesting the TMA sensing enhancement of SnSx heterostructure. Density functional theory (DFT) simulations verified the improved sensing response of SnSx heterostructure was ascribed to the p-n junction and weak hydrogen bonds. This heterostructure may contribute to the further development of QCM gas sensors for TMA sensing in the monitoring of food freshness and environment.

Nanoporous Functionalized WS2/MWCNTs Nanocomposite for Trimethylamine Detection Based on Quartz Crystal Microbalance Gas Sensor.

We have developed a tungsten disulfide (WS2)/multiwall carbon nanotubes (MWCNTs) nanocomposite based QCM gas sensor for (trimethylamine) TMA gas sensing of low concentrations. WS2/MWCNTs nanocomposite was synthesized via the hydrothermal method and was characterized for surface morphology, nanostructure, thermal stability, and elementary composition. The TMA-sensing properties of WS2/MWCNTs nanocomposite based QCM sensor were investigated. The composite based QCM sensor showed faster response time, strong response amplitude, good gas capacity, and good selectivity and stability compared with as prepared WS2 and MWCNTs-1 based QCM sensor. The response time of WS2/MWCNTs based QCM sensor was 294.1 and 142.9 s shorter than WS2 and MWCNTs-1 for 500 ppb TMA gas. And the response of the WS2/MWCNTs based QCM sensor was almost stable over 40 days, and the limit of detection (LOD) was 76 ppb calculated by the ICH method. This was ascribed to the fact that MWCNTs provided a skeleton for the growth of WS2 nanosheets and avoided agglomeration. The special structure could not only improve the structure ability but also expose more active adsorption sites. In order to further investigate the adsorption mechanism of the TMA molecule on (pure/functionalized) WS2 materials, density functional theory (DFT) calculations based on first-principle were conducted in the Vienna Ab-initio Simulation Package under ideal conditions.

Polydopamine-modified SnO2 nanofiber composite coated QCM gas sensor for high-performance formaldehyde sensing

This paper introduces a quartz crystal microbalance sensor (QCM) based on SnO2 NFs/PDA composite with multi-layer stacked fiber nanostructure, which possesses high sensitivity and selectivity to formaldehyde gas. SnO2 NFs/PDA composite was synthesized via electrospinning and further oxidative polymerization. The morphology and chemical compositions of the as-prepared composite nanomaterials were confirmed by a series of material characterization technologies. The QCM sensor based on SnO2 NFs/PDA nanomaterials exhibited excellent sensing characteristics over a wide range of formaldehyde concentration (0.5 − 50 ppm), such as high sensitivity (12.2 Hz/ppm), short response/recovery times (25 s/38 s), high linearity and selectivity. The frequency shift characteristics and electrical parameters of the prepared sensors were confirmed by impedance analysis. The adsorption mechanism of formaldehyde gas could be attributed to hydrogen bonding and the combination of aldehyde ammonia Schiff base interactions. This work indicated that SnO2 NFs/PDA based QCM possessed great potential in actual formaldehyde sensing, which provided a feasible solution for designing highly sensitive and selective formaldehyde sensor.

Identification of plastic toys contaminated with volatile organic compounds using QCM gas sensor array

In this paper, we propose a fast and easy-to-use analytical method to identify the children toys contaminated with potentially dangerous substances from the class of volatile organic compounds (VOCs). It is shown that the use of cross-sensitive gas sensor array based on piezoelectric sensors, modified with different sorbents, allows reliable recognition of items with the elevated levels of VOCs. Applying chemometric methods for processing of the sensor array data, it is possible to classify the toys into clean and hazardous ones with sensitivity and accuracy around 96%. Taking into account the simplicity of the suggested procedure, it appears to be an attractive option for cost-effective pre-screening of potentially dangerous plastic toys in comparison with the expensive and time-consuming chromatographic methods.

Digital ammonia gas sensor based on quartz resonator tuned by interdigital electrode coated with polyaniline film

Abstract This paper reported an ammonia gas sensor which was constructed by an interdigital electrode (IDE) coated with PANI thin film connected to quartz resonator in series. The sensor could convert concentration change of ammonia into frequency shift of the quartz resonator through the frequency tuning effect of IDE. Test result showed that the digital ammonia gas sensor exhibited a large frequency shift approximately 1500 Hz in ammonia concentration range of 20–1200 ppm, namely the proposed sensor showed higher frequency change compared with the majority of QCM ammonia sensors. The experiment suggested that the resistance of IDE coated with PANI film increased and meanwhile its capacitance decreased with increasing of ammonia gas concentration. Simulation on Butterworth-van Dyke (BVD) circuit of the sensor revealed that the capacitance of IDE coated with PANI played a major role in tuning of the quartz resonator although the capacitance changed little, while the resistance tuning effect was relatively weak. Compared with the traditional QCM gas sensors, the proposed sensor had a very fast response speed and a good anti-interference ability to pollutants and electromagnetic fields due to encapsulation of quartz crystal.

Sulfur dioxide adsorbed on pristine and Au dimer decorated γ-graphyne: A density functional theory study

In this work, we investigated the adsorption behaviour of sulfur dioxide on pristine and Au dimer decorated γ-graphyne (γ-GY). From comparing the adsorption energy, electron transfer and band gap, the most energetically adsorption configurations were gained. Then we made a further discussion of charge density difference, electron localization function (ELF), band structure, density of states (DOS) to evaluate the chemical and physical interactions between the SO2 and the γ-GY. The results indicated that the SO2 adsorption on the pristine γ-GY just exhibited van der Waals force with very weak chemical interactions. But SO2 could be adsorbed on Au dimer decorated γ-GY with relatively stronger chemical interactions due to the larger adsorption energy, larger electron transfer, the obvious change of SO2 molecular orbitals and many hybridizations between the Au and the S atom in DOS. Because of the unchanged band gap of Au dimer decorated γ-GY, it is more suitable for Au2-GY to be applied in QCM gas sensor to detect SO2 rather than resistance type gas sensor.

High performance formaldehyde detection based on a novel copper (II) complex functionalized QCM gas sensor

In order to construct highly sensitive and stable QCM gas sensor, we present an innovative strategy. Firstly, we employ a physical vapor deposition (PVD) method to coat a thin layer of copper on the surface of QCM silver electrode. Then, a novel metal complex as sensing material, [Cu(DDS)2(Cl)2(MeOH)2], is grown in-situ on the copper layer to ensure a strong coupling between metal complex sensing materials and QCM electrode. The sensing material is characterized through following instruments: elemental analysis, single crystal XRD, SEM, PXRD, IR spectra and TGA. The sensing test results indicate that the QCM sensor exhibit high sensitivity and selectivity toward gaseous formaldehyde because of a reversible interaction between amino group and HCHO molecule. The detection limit reaches down to 50ppb. This implies the facile-fabricated sensor has a great potential in the area of rapid, stable, sensitive, and selective formaldehyde on-site detection. Based on the temperature-varying micro-gravimetric experiment, enthalpy change is quantitatively obtained, which indicates that the interaction between the complex and HCHO molecules belongs to chemical adsorption. The values of ΔH calculated by Gaussian 09 indicate that chemical adsorption between NH2 group and aldehyde group play a leading role in detecting selectively formaldehyde gas.

Graphene Oxide / TiO2 Composite functionalized QCM gas sensor based on different TiO2 nanoparticles

Graphene Oxide / TiO2 Composite functionalized QCM gas sensor based on different TiO2 nanoparticles

Fabrication and design of a toxic gas sensor based on polyaniline/titanium dioxide nanocomposite film by layer-by-layer self-assembly

A QCM gas sensor was fabricated by a self-assembly approach with ultrathin nanocomposite PANI/TiO2. It was demonstrated to be sensitive to toxic gases (10 ppm) and to be effective in shelf-life evaluation.

Adsorption–desorption noise in QCM gas sensors

There are several mechanisms that are related to the fluctuation phenomena in QCM. The aim of our research is to study the sensitivity and the influence of different kinds of noise on sensor resolution. Our experiments are performed on sensors with a sorption layer of polypyrrole which is suitable for detection of water vapor. Based on these experiments, we conclude that 1/f noise caused by quartz internal friction and adoption–desorption (generation–recombination) noise from analyzed gas cause the main components of the measured noise spectral density. The adoption–desorption noise power depends on the physical and chemical parameters of the analyzed gas and it is proportional to the gas density. The adsorption–desorption kinetics is described by Kolmogorov's equation and is compared with the Wolkenstein and Langmuir equations.

QCM Gas Sensor with Organic Nanowire Film as Molecular Recognition Membrane

QCM Gas Sensor with Organic Nanowire Film as Molecular Recognition Membrane

P2-9 Analysis Method of QCM Gas Sensor's Response Curve and It's Application(Short presentation for poster)

P2-9 Analysis Method of QCM Gas Sensor's Response Curve and It's Application(Short presentation for poster)

P2-C-2 Study on Gas Adsorption Property Evaluation of Sensing Film for QCM Gas Sensor by Sensor Response Analysis

P2-C-2 Study on Gas Adsorption Property Evaluation of Sensing Film for QCM Gas Sensor by Sensor Response Analysis

Improvement of olfactory video camera: gas/odor flow visualization system

The “olfactory video camera” is a sensing system that helps locate a source of gas or odor. It consists of a portable homogeneous array of QCM gas sensors, and presents the visualized images of gas/odor flow reaching the array from the source location. In this paper, an improved version of the system is reported. A multichannel reciprocal frequency counter is implemented into a programmable LSI chip, and is employed to achieve a higher sampling rate of sensor responses while keeping the frequency resolution same as that of the conventional counter in the previous system. As a result, the temporal resolution of the visualized gas/odor flow has been improved and the maximum detectable flow velocity has been raised. The performance of the system has been tested in a clean room and a laboratory with regard to the system’s capability in capturing gas flow directions and pinpointing source locations. The experimental results have shown that the system can be applied in a variety of indoor environments.

Study to Increase the Sensitivity of QCM Gas-Sensor Coated with Plasma Polymerization Film

Fundamental and overtone modes of quartz resonators with high frequencies have been studied to increase the sensitivity of QCM gas-sensor. Polystyrene film was plasma-polymerized onto the electrode surface of an AT-cut quartz resonator and then used as a molecular recognition membrane to detect gas-phase analytes. In this study, handmade oscillators with superior stability were used to vibrate each mode of AT-cut quartz resonators. Deriving the theoretical mass sensitivity of an AT-cut quartz resonator vibrating at the overtone mode, confirmed the fact that the theoretical value was the same as the result obtained from the experiments.

Recording of Oder Recipe Using Active Odor Sensing System.

Odor recorder, where an odor with its recipe electronically recorded is reproduced by an odor blender, was developed. The odor recipe can be determined within a minute by the active odor sensing system with a QCM gas sensor array and an internal blender. The odor recipe can be obtained after minimizing the difference between the sensor-array output pattern of the target odor and that of the internally blended one using multiple-input multiple-output feedback control. The recipe of an apple flavor made up of four component odors with the impressions such as softly green note, sour sweet, fruity and the smell of grass was successfully determined by the system. Furthermore, it was confirmed that the odor the same as the target odor was reproduced using the internal odor blender. The principle and the fundamental experiments on odor recording are presented here.

Vapor supply method in odor sensing system and analysis of transient sensor responses

In an odor sensing system, a flow-type measurement system has been used to supply odorant vapors to the sensor cell since the measurement system is quite simple and enables the rapid measurement. Although we have used the peak frequency shifts of QCM gas sensors during the vapor exposure as the sensor outputs, the shapes of the transient responses may be useful to discriminate odor samples. Moreover, the sensing system should be robust when the measurement condition such as supplied vapor concentration fluctuates. Then, we proposed pulse vapor supply method and modelled the measurement system to extract the information for odor identification. Since the variation of the vapor concentration could be ignored in the pulse vapor supply method, the system model became simple enough to be robust to the fluctuation. The pattern separation among various samples with artificially fluctuated concentrations was improved when the model parameters of transient responses after the pulse vapor supply were used.

Study on the behavior of oscillation circuit for QCM gas sensor

Study on the behavior of oscillation circuit for QCM gas sensor