Special Issue "Quartz-Enhanced Photoacoustic and Photothermal Spectroscopy"

A special issue of Applied Sciences (ISSN 2076-3417). This special issue belongs to the section "Quantum Science and Technology".

Deadline for manuscript submissions: closed (5 July 2020).

Special Issue Editors

Dr. Angelo Sampaolo
Website
Guest Editor
Polysense Lab – Dipartimento di Fisica, Politecnico di Bari, Bari, Italy
Interests: optoelectronics and nanotechnology, innovative optical gas sensor systems and their application to environmental monitoring, industrial process analysis, control, medical diagnostics
Dr. Hongpeng Wu
Website
Guest Editor
Institute of Laser Spectroscopy, Shanxi University, Taiyuan, China
Interests: photoacoustic spectrometry; photothermal Spectroscopy; laser applications in environmental monitoring, industrial process control and medicine
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Special Issue Information

Dear Colleagues,

The detection and measurement of trace gas concentrations is crucial for the understanding and monitoring of chemical and physical processes for a wide variety of applications, such as environmental monitoring, industrial process control, combustion processes, medicine, detection of toxic and flammable gases, as well as explosives. Laser-based spectroscopic techniques for trace gas detection are capable of high sensitivity and selectivity. These features are required in atmospheric science for the monitoring of different trace gas species including greenhouse gases and ozone, and in breath diagnostics to detect nitric oxide, ethane, ammonia and numerous other biomarkers. For the in-situ and real time measurements, the high sensitivity and selectivity must be combined with compactness and robustness of the sensors. In this landscape, photoacoustic and photothermal spectroscopy based on quartz tuning forks (QTF) have been proving through the last 15 years all the advantages of avoiding the use of optical detectors by employing acoustic resonators, which are immune to environmental noise and wavelength insensitive.

The present Special Issue was conceived with the aim of collecting and connecting all the provided contributions, works and analysis that are currently pushing quartz-enhanced photacoustic and phototermal spectroscopy to the state of art. The topics of focus will embrace the new generation of custom resonators, novel experimental approaches, smart solutions to real-world challenges, as well as theoretically-oriented issues, such as simulation of QTF vibrational dynamics, analysis of broadband absorbers, the effects of gas matrix changes, and gas relaxation dynamics.

Dr. Angelo Sampaolo
Dr. Hongpeng Wu
Guest Editors

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Keywords

  • Quartz-enhanced photoacoustic spectroscopy
  • Quartz-enhanced photothermal spectroscopy
  • Quartz tuning forks
  • Trace gas detection
  • In-situ real-time applications

Published Papers (11 papers)

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Research

Open AccessArticle
Quartz Enhanced Conductance Spectroscopy for Polymer Nano-Mechanical Thermal Analysis
Appl. Sci. 2020, 10(14), 4954; https://doi.org/10.3390/app10144954 - 18 Jul 2020
Abstract
A fast and highly sensitive polymer nano-mechanical thermal analysis method for determining the melting temperature (Tm) of polymer microwires was proposed. In this method, a small-size, low-cost quartz tuning fork was used as a piezoelectric transducer to analyze the thermodynamics [...] Read more.
A fast and highly sensitive polymer nano-mechanical thermal analysis method for determining the melting temperature (Tm) of polymer microwires was proposed. In this method, a small-size, low-cost quartz tuning fork was used as a piezoelectric transducer to analyze the thermodynamics of polymer microwires at the nanogram level without changing its own properties. Due to the thin wire sample, which has a length of 1.2 mm and a diameter of ~5 µm, which is bridged across the prongs of the tuning fork, the nanogram-level sample greatly reduces the thermal equilibrium time for the measurement, resulting in a fast analysis for the melting temperature of the polymer sample. Compared with the traditional method, the analysis method based on the quartz enhanced conductivity spectrum (QECS) does not require annealing before measurement, which is an essential process for conventional thermal analysis to reduce the hardness, refine the grain, and eliminate the residual stress. In this work, the melting temperatures of three of the most commonly used polymers, namely polymers polymethyl methacrylate, high-density polyethylene, and disproportionated rosin, were obtained under the temperature from room temperature to >180 °C, proving the QECS method to be a useful tool for nano-mechanical thermal analysis. Full article
(This article belongs to the Special Issue Quartz-Enhanced Photoacoustic and Photothermal Spectroscopy)
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Open AccessArticle
Improving the Signal to Noise Ratio of QTF Preamplifiers Dedicated for QEPAS Applications
Appl. Sci. 2020, 10(12), 4105; https://doi.org/10.3390/app10124105 - 15 Jun 2020
Abstract
The signal-to-noise ratio (SNR) is a major factor that limits the detection sensitivity of quartz-enhanced photoacoustic spectroscopy (QEPAS) sensors. The higher the electrical signal level compared to the noise amplitude is the lower the concentration of gases that can be detected. For this [...] Read more.
The signal-to-noise ratio (SNR) is a major factor that limits the detection sensitivity of quartz-enhanced photoacoustic spectroscopy (QEPAS) sensors. The higher the electrical signal level compared to the noise amplitude is the lower the concentration of gases that can be detected. For this reason the preamplifier circuits used in QEPAS should be optimized for low-frequency narrow-band applications. Moreover, special care should be taken when choosing a particular operational amplifier in either a transimpedance or voltage (differential) configuration. It turns out that depending on the preamp topology different operational amplifier parameters should be carefully considered when a high SNR of the whole QEPAS system is required. In this article we analyzed the influence of the crucial parameters of low-noise operational preamplifiers used in QEPAS applications and show the resulting limitations of transimpedance and voltage configurations. Full article
(This article belongs to the Special Issue Quartz-Enhanced Photoacoustic and Photothermal Spectroscopy)
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Open AccessArticle
Front-End Amplifiers for Tuning Forks in Quartz Enhanced PhotoAcoustic Spectroscopy
Appl. Sci. 2020, 10(8), 2947; https://doi.org/10.3390/app10082947 - 24 Apr 2020
Abstract
A study of the front-end electronics for quartz tuning forks (QTFs) employed as optoacoustic transducers in quartz-enhanced photoacoustic spectroscopy (QEPAS) sensing is reported. Voltage amplifier-based electronics is proposed as an alternative to the transimpedance amplifier commonly employed in QEPAS experiments. The possibility to [...] Read more.
A study of the front-end electronics for quartz tuning forks (QTFs) employed as optoacoustic transducers in quartz-enhanced photoacoustic spectroscopy (QEPAS) sensing is reported. Voltage amplifier-based electronics is proposed as an alternative to the transimpedance amplifier commonly employed in QEPAS experiments. The possibility to use differential input/output configurations with respect to a single-ended configuration has also been investigated. Four different architectures have been realized and tested: a single-ended transimpedance amplifier, a differential output transimpedance amplifier, a differential input voltage amplifier and a fully differential voltage amplifier. All of these amplifiers were implemented in a QEPAS sensor operating in the mid-IR spectral range. Water vapor in ambient air has been selected as the target gas species for the amplifiers testing and validation. The signal-to-noise ratio (SNR) measured for the different configurations has been used to compare the performances of the proposed architectures. We demonstrated that the fully differential voltage amplifier allows for a nearly doubled SNR with respect to the typically used single-ended transimpedance amplifier. Full article
(This article belongs to the Special Issue Quartz-Enhanced Photoacoustic and Photothermal Spectroscopy)
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Open AccessFeature PaperArticle
Quartz-Enhanced Photoacoustic Detection of Ethane in the Near-IR Exploiting a Highly Performant Spectrophone
Appl. Sci. 2020, 10(7), 2447; https://doi.org/10.3390/app10072447 - 03 Apr 2020
Abstract
In this paper the performances of two spectrophones for quartz-enhanced photoacoustic spectroscopy (QEPAS)-based ethane gas sensing were tested and compared. Each spectrophone contains a quartz tuning fork (QTF) acoustically coupled with a pair of micro-resonator tubes and having a fundamental mode resonance frequency [...] Read more.
In this paper the performances of two spectrophones for quartz-enhanced photoacoustic spectroscopy (QEPAS)-based ethane gas sensing were tested and compared. Each spectrophone contains a quartz tuning fork (QTF) acoustically coupled with a pair of micro-resonator tubes and having a fundamental mode resonance frequency of 32.7 kHz (standard QTF) and 12.4 kHz (custom QTF), respectively. The spectrophones were implemented into a QEPAS acoustic detection module (ADM) together with a preamplifier having a gain bandwidth optimized for the respective QTF resonance frequency. Each ADM was tested for ethane QEPAS sensing, employing a custom pigtailed laser diode emitting at ~1684 nm as the exciting light source. By flowing 1% ethane at atmospheric pressure, a signal-to-noise ratio of 453.2 was measured by implementing the 12.4 kHz QTF-based ADM, ~3.3 times greater than the value obtained using a standard QTF. The minimum ethane concentration detectable using a 100 ms lock-in integration time achieving the 12.4 kHz custom QTF was 22 ppm. Full article
(This article belongs to the Special Issue Quartz-Enhanced Photoacoustic and Photothermal Spectroscopy)
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Open AccessArticle
Narrowband Perfect Absorber Based on Dielectric-Metal Metasurface for Surface-Enhanced Infrared Sensing
Appl. Sci. 2020, 10(7), 2295; https://doi.org/10.3390/app10072295 - 27 Mar 2020
Cited by 1
Abstract
We proposed a narrowband perfect absorber that was based on dielectric-metal metasurface for wide-band surface-enhanced infrared sensing. It is found that the narrowband perfect absorber can generate the hybrid guided modes with high quality-factor at infrared frequencies, which make the absorber highly sensitive [...] Read more.
We proposed a narrowband perfect absorber that was based on dielectric-metal metasurface for wide-band surface-enhanced infrared sensing. It is found that the narrowband perfect absorber can generate the hybrid guided modes with high quality-factor at infrared frequencies, which make the absorber highly sensitive to the surrounded analyte. Moreover, tuning the incident angle can actively modulate the resonant wavelength of absorber. Such an absorber with excellent features is employed to realize both refractive index sensing and infrared vibrational fingerprint sensing on a single substrate. It is demonstrated that a refractive index sensitivity of 1800 nm/RIU and figure of merit of 62 RIU−1 can be obtained as the refractive index sensor. While, as a surface enhanced infrared absorption spectroscopy substrate, two closed vibrational modes of analyte with nanometer thick layers can be effectively identified and selectively detected with 50-folds enhancement by actively tuning the incident angle without any change in the structural parameters (periodicity, width, height, and refractive index of the grating) of the device after fabricating. Our study offers a promising approach for designing high-performance surface-enhanced infrared optical sensors in the infrared region. Full article
(This article belongs to the Special Issue Quartz-Enhanced Photoacoustic and Photothermal Spectroscopy)
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Open AccessArticle
Quartz Enhanced Photoacoustic Detection Based on an Elliptical Laser Beam
Appl. Sci. 2020, 10(4), 1197; https://doi.org/10.3390/app10041197 - 11 Feb 2020
Abstract
A quartz enhanced photoacoustic spectroscopy (QEPAS) sensor system based on an elliptical laser beam for trace gas detection was demonstrated. A Powell lens was exploited to shape the circular laser beam into an elliptical laser beam for the full utilization of the quartz [...] Read more.
A quartz enhanced photoacoustic spectroscopy (QEPAS) sensor system based on an elliptical laser beam for trace gas detection was demonstrated. A Powell lens was exploited to shape the circular laser beam into an elliptical laser beam for the full utilization of the quartz tuning fork (QTF) prong spacing. Based on the finite element modeling (FEM) simulation software COMSOL, the distribution of acoustic pressure on QTF prongs with different beam shapes was simulated theoretically. The experimental results showed that the QEPAS signal based on the elliptical laser beam had a 1.4-fold improvement compared with the circular laser beam, resulting in a minimum detection limit of 418.6 ppmv and the normalized noise equivalent absorption (NNEA) of 1.51 × 10−6 cm−1 W/√Hz at atmospheric pressure. Full article
(This article belongs to the Special Issue Quartz-Enhanced Photoacoustic and Photothermal Spectroscopy)
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Open AccessArticle
Anomalous Humidity Dependence in Photoacoustic Spectroscopy of CO Explained by Kinetic Cooling
Appl. Sci. 2020, 10(3), 843; https://doi.org/10.3390/app10030843 - 24 Jan 2020
Cited by 2
Abstract
Water affects the amplitude of photoacoustic signals from many gas phase molecules. In quartz-enhanced photoacoustic (QEPAS) measurements of CO excited at the fundamental vibrational resonance of CO, the photoacoustic signal decreases with increasing humidity, reaches a pronounced minimum at ~0.19%V, and [...] Read more.
Water affects the amplitude of photoacoustic signals from many gas phase molecules. In quartz-enhanced photoacoustic (QEPAS) measurements of CO excited at the fundamental vibrational resonance of CO, the photoacoustic signal decreases with increasing humidity, reaches a pronounced minimum at ~0.19%V, and increases with humidity for higher water contents. This peculiar trend is explained by competing endothermal and exothermal pathways of the vibrational relaxation of CO in N2 and H2O. Near-resonant vibrational–vibrational transfer from CO to N2, whose vibrational frequency is 188 cm−1 higher than in CO, consumes thermal energy, yielding a kinetic cooling effect. In contrast, vibrational relaxation via H2O is fast and exothermal, and hence counteracts kinetic cooling, explaining the observed trend. A detailed kinetic model for collisional relaxation of CO in N2 and H2O is presented. Simulations using rate constants obtained from literature were performed and compared to humidity dependent QEPAS experiments at varying pressure. Agreement between the experiments and simulations confirmed the validity of the model. The kinetic model can be used to identify optimized experimental conditions for sensing CO and can be readily adapted to include further collision partners. Full article
(This article belongs to the Special Issue Quartz-Enhanced Photoacoustic and Photothermal Spectroscopy)
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Open AccessArticle
Phase Optimized Photoacoustic Sensing of Gas Mixtures
Appl. Sci. 2020, 10(2), 438; https://doi.org/10.3390/app10020438 - 07 Jan 2020
Cited by 2
Abstract
In this paper, we report on the progress of the auto-triggered quartz-enhanced photoacoustic spectroscopy (QEPAS) technique which operates without external frequency generators and ensures permanent locking to the current resonance frequency of the tuning fork. This is obtained by incorporating the tuning fork [...] Read more.
In this paper, we report on the progress of the auto-triggered quartz-enhanced photoacoustic spectroscopy (QEPAS) technique which operates without external frequency generators and ensures permanent locking to the current resonance frequency of the tuning fork. This is obtained by incorporating the tuning fork in an oscillator circuit that autonomously oscillates at the present resonance frequency that shifts with changing environmental conditions, e.g., density and viscosity of the surrounding gas, temperature, and pressure. Both, the oscillation amplitude as well as the frequency can be read from the oscillator circuit. The photoacoustic signal appears as an offset of the electrically induced signal amplitude. Since the sum amplitude depends on the phase relation between the electrical and photoacoustic driving forces, the phase is permanently modulated, enabling the extraction of the photoacoustic component by use of a second lock-in amplifier stage which is being referenced with the phase modulation frequency. The functionality of this method is demonstrated for methane detection in a carbon dioxide atmosphere in a concentration range from 0 to 100% and ammonia in synthetic air employing a pulsed mid infrared QCL around 1280 cm−1. The gas mixtures are motivated by the demands in biogas-analysis. Full article
(This article belongs to the Special Issue Quartz-Enhanced Photoacoustic and Photothermal Spectroscopy)
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Open AccessArticle
Near-Infrared Quartz-Enhanced Photoacoustic Sensor for H2S Detection in Biogas
Appl. Sci. 2019, 9(24), 5347; https://doi.org/10.3390/app9245347 - 06 Dec 2019
Abstract
A quartz-enhanced photoacoustic spectroscopy (QEPAS) sensor for H2S detection operating in near-infrared spectral range is reported. The optical source is an erbium-doped fiber amplified laser with watt-level optical power. The QEPAS spectrophone is composed of a quartz tuning fork with a [...] Read more.
A quartz-enhanced photoacoustic spectroscopy (QEPAS) sensor for H2S detection operating in near-infrared spectral range is reported. The optical source is an erbium-doped fiber amplified laser with watt-level optical power. The QEPAS spectrophone is composed of a quartz tuning fork with a resonance frequency of 7.2 kHz, a quality factor of 8500, and a distance between prongs of 800 µm, and two tubes with a radius of 1.3 mm and a length of 23 mm acting as an organ pipe resonator. With this spectrophone geometry, the photothermal noise contribution of the spectrophone was removed and the theoretical thermal noise level was achieved. The position of both tubes with respect to custom quartz tuning fork has been investigated as a function of signal amplitude, Q-factor, and noise of the QEPAS sensor when a high-power laser was used. Benefit from the linearity of the QEPAS signal to the excitation laser power, a detection sensitivity of 330 ppb for H2S detection was achieved at atmospheric pressure and room temperature, when the laser power was 1.6 W and the signal integration time was set to 300 ms, corresponding to a normalized noise equivalent absorption of 3.15 × 10−9 W cm−1/(Hz)1/2. The QEPAS sensor was then validated by measuring H2S in a biogas sample. Full article
(This article belongs to the Special Issue Quartz-Enhanced Photoacoustic and Photothermal Spectroscopy)
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Open AccessArticle
Precise Photon Correlation Measurement of a Chaotic Laser
Appl. Sci. 2019, 9(22), 4907; https://doi.org/10.3390/app9224907 - 15 Nov 2019
Cited by 1
Abstract
The second order photon correlation g(2)(τ) of a chaotic optical-feedback semiconductor laser is precisely measured using a Hanbury Brown–Twiss interferometer. The accurate g(2)(τ) with non-zero delay time is obtained experimentally from the photon pair time [...] Read more.
The second order photon correlation g(2)(τ) of a chaotic optical-feedback semiconductor laser is precisely measured using a Hanbury Brown–Twiss interferometer. The accurate g(2)(τ) with non-zero delay time is obtained experimentally from the photon pair time interval distribution through a ninth-order self-convolution correction. The experimental results agree well with the theoretical analysis. The relative error of g(2)(τ) is no more than 5‰ within 50 ns delay time. The bunching effect and coherence time of the chaotic laser are measured via the precise photon correlation technique. This technique provides a new tool to improve the accuracy of g(2)(τ) measurement and boost applications of quantum statistics and correlation. Full article
(This article belongs to the Special Issue Quartz-Enhanced Photoacoustic and Photothermal Spectroscopy)
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Open AccessCommunication
Quartz-Enhanced Photothermal-Acoustic Spectroscopy for Trace Gas Analysis
Appl. Sci. 2019, 9(19), 4021; https://doi.org/10.3390/app9194021 - 26 Sep 2019
Cited by 3
Abstract
A crystal quartz tuning fork (QTF) was used as a detector to collect and amplify laser-induced photoacoustic and photothermal waves simultaneously for trace chemical analysis. A wavelength modulation technique was applied to the proposed quartz-enhanced photothermal-acoustic spectroscopy (QEPTAS) to improve the detection signal-to-noise [...] Read more.
A crystal quartz tuning fork (QTF) was used as a detector to collect and amplify laser-induced photoacoustic and photothermal waves simultaneously for trace chemical analysis. A wavelength modulation technique was applied to the proposed quartz-enhanced photothermal-acoustic spectroscopy (QEPTAS) to improve the detection signal-to-noise ratio. The QTF detector was exposed to the illumination of a near-infrared distributed feedback laser at distances of 1 m and 2 m to evaluate the QEPTAS sensor performance. The QEPTAS sensor performance was determined by detecting water vapor in ambient air using a near-infrared distributed feedback laser with a power of ~10 mW and a wavelength of 1.39 μm. With an optimized modulation depth of 0.47 cm−1, the normalized noise equivalent absorption (NNEA) coefficients of 8.4 × 10−7 W·cm−1·Hz−1/2 and 3.7 × 10−6 W·cm−1·Hz−1/2 were achieved for a distance of 1 m and 2 m, respectively. The developed QEPTAS technique reduces the requirements for laser beam quality, resulting in a simple but robust sensor structure and demonstrates the ability of remote sensing of gas concentrations. Full article
(This article belongs to the Special Issue Quartz-Enhanced Photoacoustic and Photothermal Spectroscopy)
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