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Turku, Finland

Hirschmann C.B.,University of Oulu | Hirschmann C.B.,VTT Technical Research Center of Finland | Lehtinen J.,University of Turku | Uotila J.,Gasera Ltd | And 3 more authors.
Applied Physics B: Lasers and Optics | Year: 2013

A novel cantilever enhanced photoacoustic spectrometer with mid-infrared quantum cascade laser was applied for selective and sensitive formaldehyde (CH2O) gas measurement. The spectrum of formaldehyde was measured from 1,772 to 1,777 cm-1 by tuning the laser with a spectral resolution of 0.018 cm-1. The band at 1,773.959 cm-1 was selected for data analysis, at which position the laser emitted 47 mW. In univariate measurement, the detection limit (3σ, 0.951 s) and the normalized noise equivalent absorption coefficient (3σ) for amplitude modulation (AM) were 1.6 ppbv and 7.32 × 10-10 W cm -1 (Hz)-1/2 and for wavelength modulation (WM) 1.3 ppbv and 6.04 × 10-10 W cm-1 (Hz)-1/2. In multivariate measurement, the detection limit (3σ) can be as low as 901 pptv (1,773.833-1,774.085 cm-1, 15 spectral points each 0.951 s) for AM and 623 pptv (1,773.743-1,774.265 cm-1, 30 spectral points each 0.951 s) for WM. Because measurement time increases in multivariate measurement, its application is justified only when interferents need to be resolved. Potential improvements of the system are discussed. © 2013 Springer-Verlag Berlin Heidelberg. Source

Hirschmann C.B.,University of Oulu | Hirschmann C.B.,VTT Technical Research Center of Finland | Uotila J.,Gasera Ltd | Ojala S.,University of Oulu | And 3 more authors.
Applied Spectroscopy | Year: 2010

The sensitivity of photoacoustic spectroscopy was improved with the invention of optical cantilever detection (PAS-OCD). However, the ability of present PAS-OCD devices to carry out multicomponent detection is poor. To overcome this, a Fourier transform infrared photoacoustic spectrometer with optical cantilever detection (FT-IR-PAS-OCD) prototype was assembled. In this article, the first evaluation and performance tests of the prototype are described. Selectivity, sensitivity, and the linearity of the signal response are evaluated. The linear response was studied for methane and carbon dioxide and confirmed in the whole analyzed concentration range from 500 to 3500 ppm and from 2500 to 17500 ppm, respectively. The calculated signal-to-noise ratio (SNR) and limit of detection were 2027 and 0.5 ppm for methane and 1362 and 4 ppm for carbon dioxide, with a measurement time of 100 seconds. Selectivity was studied with a multicomponent gas mixture of propene, methane, carbon dioxide, and methylmercaptane. The results indicate that a quantitative analysis of all components in the mixture is possible using the FT-IR-PAS-OCD. © 2010 Society for Applied Spectroscopy. Source

Sievila P.,Aalto University | Chekurov N.,Aalto University | Raittila J.,Gasera Ltd | Tittonen I.,Aalto University
Sensors and Actuators, A: Physical | Year: 2013

Silicon cantilever sensors have been designed, fabricated and tested in acoustic wave detection. The principal application of the components is photoacoustic spectroscopy (PAS) which is a highly sensitive method in solid, liquid and gas analysis. The developed microfabrication process of the sensors is based on silicon-on-insulator (SOI) wafer etching, in which the challenge is to control and minimize the residual stress related curving in thin (5 μm) but large-area (few mm2) components. The sensitivity of the fabricated cantilevers is investigated in photoacoustic measurements of solid samples, and the signal strength is shown to increase tens of percent compared with the results obtained with previously reported cantilever microphones. Improvement of the signal-to-noise ratio (SNR) verifies the advantage of the presented cantilevers in photoacoustic sensing. © 2012 Elsevier B.V. Source

Gasera Ltd | Date: 2009-12-29

Scientific, measuring, signaling apparatus and instruments, namely, gas analyzers for scientific, research, industrial, medical, safety, security, military and environmental purposes, photoacoustic detectors for solid, liquid, semi-solid and gas samples, gas sensors, Fourier transform infrared (FTIR) spectrometers; optical apparatus and instruments, namely, optical displacement measurement apparatus.

Uotila J.,Gasera Ltd | Lehtinen J.,University of Turku | Kuusela T.,University of Turku | Sinisalo S.,Gasera Ltd | And 3 more authors.
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2012

Chemical control is a crucial element for controlling the manufacturing and distribution of illegal narcotics and synthetic substances. This work is focusing on the vapor phase point detection methodology due to its applicability in customs, airport and harbor check point scenarios where inspection of trucks, cars, containers, as well as people and baggage is required. There are several techniques available that are able to screen and identify specific molecules even at very low concentration at laboratory or in controlled environment. However, a portable system which would be simple to use, sensitive, compact, and capable of providing screening over a large number of compounds and discriminate them with low probability of false alarms with short response time scale is still demanded. Our solution is to combine cantilever enhanced photoacoustic spectroscopy with external cavity quantum cascade laser (EC-QCL), which is capable of measuring infrared gas phase spectra of the analyte substances. High sensitivity in a wide dynamic range is achieved with a silicon MEMS cantilever sensor coupled with an optical readout system and high power laser source, which is operating at the fundamental vibrational absorption wavelengths. High selectivity is achieved by measuring the infrared spectra of the sample gas utilizing widely tunable EC-QCL technology and novel signal processing methods. Measurements with the breadboard demonstrator of the described system and detection limit estimation were performed to a selected drug precursor target molecules. The measurement results indicate low ppb-level gas phase sensitivity to selected drug precursor substances also in the presence of typical interfering molecules. © 2012 SPIE. Source

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