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Accurate and rapid detection and isolation become indispensable to restrict the spread of COVID-19. Since the start of COVID-19 pandemic in December 2019, many indisposal diagnostic tools are being developed incessantly. Out of all presently used tools, the gold standard rRT- PCR tool having very high sensitivity and specificity is a time consuming complicated molecular technique having requirements of special expensive equipment. Here, the main focus of this work is to develop rapid disposal paper capacitance sensor having simple and easy detection. We discovered a strong interaction between limonin and Spike-glycoprotein of SARS-COV-2 in comparison to its interaction with other similar viruses such as HCOV-OC43, HCOV-NL63, HCOV-HKU1, Influenza B and A viruses. The antibody free capacitive sensor having comb electrode structure was fabricated on whatman paper with drop coating of limonin (extracted using green method from pomelo seeds) and calibrated with known swab samples. The Blind test with unknown swab samples shows high sensitivity of 91.5% and high specificity of 88.37%. Requiring low sample volume and detection time and using biodegradable materials in the sensor fabrication assure the potential application as a point of care disposal diagnostic tool. [Display omitted] • A rapid COVID-19 detection kit based on capacitive sensor based has been developed. • Limonin extracted from plant seeds has been used as sensing material. • The sensor exhibited high sensitivity of 91.5%(clinical) with high specificity of 88.37%. • Detection time for the sensor is ∼182s with sample volume requirement of 10 μL. • This paper-based sensor assures inexpensive, easy, onsite detection of COVID-19. [ABSTRACT FROM AUTHOR]

Fish freshness plays a vital role in the fish industry and also affects human health from a nutrition point of view. Here, an Au metal patch electrode capacitive sensor is introduced for rapid and accurate detection of volatile gases generated from raw fish to determine its freshness status. The MIS structured sensor was fabricated on a silicon substrate using Ag–SnO 2 as sensing material over SiO 2 layer and Au as a metal electrode. The calibration of the sensor was carried out with known composition of volatile gases (NH 3 , TMA, DMA and H 2 S) in the ppb-ppm regime. Our sensor using the proposed technique delivers sensor response to raw fish within 4 min, reflecting its freshness status in comparison to the TVB-N and TVC method which takes many hours to complete involving many sophisticated steps. The sensor response to volatile gases from Rohu (Labeo Rohita), Tilapia (Oreochromis Niloticus) and Illish (Tenualosa Ilisha) obtained by using our developed sensor system at 20 °C, 25 °C, and 30 °C, shows high correlation with TVB-N and TVC results. The acceptance limit for safe consumption of Tilapia, Rohu, and Illish at 30 °C was found to be 11 h, 12.5 h, and 10 h of storage time respectively. The result in this work assures a portable low-cost sensor for onsite monitoring of fish freshness at room temperature. • Au patch electrode Ag–SnO 2 SiO 2 /Si MIS capacitive sensor is fabricated. • LOD obtained as 25 ppb (NH 3) and 50 ppb (H 2 S, TMA, and DMA). • Sensor response/recovery time is obtained as ~55/140 s. • Highly correlated with TVB-N and TVC. [ABSTRACT FROM AUTHOR]

• Synthesis of Ag-doped SnO 2 nanoparticles. • Au patch electrode Ag-SnO 2 /SiO 2 /Si MIS capacitive gas sensor was fabricated. • Quality assessment of chicken meat at different temperatures. • Significant correlation with TVB-N, TVC, pH, SE analysis. An Au patch electrode Ag-SnO 2 /SiO 2 /Si MIS capacitive sensor equipped with a microcontroller was designed and developed to sense low concentration (ppb to ppm regime) of volatiles (NH 3 , TMA, ethanol, and H 2 S) generated from chicken meat spoilage at room temperature. The quality threshold or the acceptance limit for consumption of chicken meat samples stored at 4 °C, 15 °C and 25 °C using our proposed technique was found to be 105 h, 48 h, and 17 h respectively, highly correlated with TVB-N, TVC, pH and sensory evaluation analysis. When these well established standard methods (TVB-N, TVC and pH analysis) take many hours to complete the analysis involving many complicated steps, our fabricated sensor takes 55 sec to deliver sensing response reflecting the meat spoilage status. The sensor calibrated with our compact technique promises portable and inexpensive onsite rapid and accurate quality assessment of meat spoilage at room temperature. [ABSTRACT FROM AUTHOR]