Abstract
Pyroelectrics are a wide class of materials that change their polarization when the system temperature varies. This effect is utilized for a number of different commercial and industrial applications ranging from simple thermal sensors and laser interferometers to water vapor harvesting. Electron paramagnetic resonance (EPR) spectroscopy is a powerful tool for studying the structure and dynamics of materials with unpaired electrons. Since heating accompanies a resonant change of the orientation of electron spins in an external magnetic field, pyroelectrics can be utilized as versatile detectors for so-called indirect detection of the EPR signal. In this work, we investigated three different types of PVDF (polyvinylidene difluoride) standard pyroelectric films with indium tin oxide, Cu/Ni, and Au coatings to determine their sensitivity for detecting EPR signals. All the films were shown to be able to detect the EPR spectra of about 1 μg of a standard stable free radical by heat release. A comparative study based on the calculation of the noise-equivalent power and specific detectivity from experimental spectra showed that the Au coated PVDF film is the most promising active element for measuring the EPR signal. Using the best achieved sensitivity, estimation is given whether this is sufficient for using a PVDF-based pyrodetector for indirectly detecting EPR spectra by recombination heat release or not.
Highlights
Pyroelectric and piezoelectric sensors made on the basis of flexible PVDF films are successfully used in many fields of technology, medicine, and scientific research [1,2,3,4,5,6,7,8]
In order to measure the intensity of constant radiation flux, it should be modulated in intensity by a spatial beam modulator since the pyroelectric sensor responds to the change in temperature, not to absolute temperature
This work aims to investigate the behavior of pyroelectric sensors made of PVDF films under experimental conditions of Electron paramagnetic resonance (EPR) spectroscopy, to determine their sensitivity to the desired signal and various external interference of electromagnetic or acoustic nature, and to calculate their attainable signal-to-noise ratio
Summary
The pyroelectric properties of such films, which are previously poled in a strong electric field to enhance their performance, are used for the detection of radiation in various energy ranges, mainly in infrared and terahertz. These detectors can have different shapes and are cut from PVDF films with a thickness of several microns (most often 28 μm) that are metalized on both sides to register a pyroelectric signal. A transimpedance operational amplifier circuit, operating in current mode, is used as LNA
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