Abstract
(1) Background: A quest for a highly sensitive and reliable humidity monitoring system for a diverse variety of applications is quite vital. Specifically, the ever-increasing demand of humidity sensors in applications ranging from agriculture to healthcare equipment (to cater the current demand of COVID-19 ventilation systems), calls for a selection of suitable humidity sensing material. (2) Methods: In the present study, the TPPNi macromolecule has been synthesized by using a microwave-assisted synthesis process. The layer structure of the fabricated humidity sensor (Al/TPPNi/Al) consists of pair of planar 120 nm thin aluminum (Al) electrodes (deposited by thermal evaporation) and ~160 nm facile spin-coated solution-processable organic TPPNi as an active layer between the ~40 µm electrode gap. (3) Results: Electrical properties (capacitance and impedance) of sensors were found to be substantially sensitive not only on relative humidity but also on the frequency of the input bias signal. The proposed sensor exhibits multimode (capacitive and conductometric) operation with significantly higher sensitivity ~146.17 pF/%RH at 500 Hz and 48.23 kΩ/%RH at 1 kHz. (4) Conclusions: The developed Al/TPPNi/Al surface type humidity sensor’s much-improved detecting properties along with reasonable dynamic range and response time suggest that it could be effective for continuous humidity monitoring in multi environmental applications.
Highlights
We report a facile realization of surface type humidity sensor (Al/TPPNi/Al) based on 5,10,15,20-tetraphenylporphyrinatonickel(II)
Fabrication and characterization of TPPNi thin films for their use as surface type humidity sensors have been studied for the TPPNi synthesized by microwave-assisted method
The observed “halo” pattern in X-ray Diffraction (XRD) structural characterization has clearly demonstrated that the fabricated thin films possess amorphous, glassy, or disordered structures
Summary
Effective and reliable humidity monitoring is of prime significance in an increasing number of industrial sectors such as in the chemical, electronics, pharmaceutical, agricultural, and HVAC (heating, ventilation, and air conditioning) sectors [1,2,3]. With the recent emergence of the internet of things (IoT) technology, humidity sensors are the utmost important components in developing state-of-the-art systems such as in smart farming, storage monitoring, healthcare equipment (CPAP machines and ventilators), and home automation [4,5,6,7]. Available humidity monitoring devices typically resort to measurements of moisture-related changes in temperature, pressure, mass, or mechanical or electrical parameters of the active sensing material from which the moisture content can later be indicated [8,9]. The most ubiquitously utilized transduction techniques rely either on a variation in the conductivity or dielectric constant of the hygroscopic humidity sensing material [10]
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