Highly Sensitive Label-Free Biosensor Based on Microbottle Cavity-Gold Nanocoated Layer for Facile Detection of COVID-19 RNA

To improve the sensitivity of the whispering-gallery mode microbottle cavity to the low-concentration solution, a nanoparticle gold film-modified microbottle cavity sensor is proposed and demonstrated by measuring the low concentration measurement of RNA virus (COVID-19) molecules. The results show that the refractive index sensitivity of the micro-bottle cavity can be effectively improved by a nano-gold film, which can reach 261 nm/RIU in the refractive index range of 1.3320 to 1.3332. In the 10 pg/ml concentration range to 100 ng/ml COVID-19 RNA, the sensor output signal has a linear relationship with the concentration, and the detection limit can reach 10 pg/ml. The sensor has high sensitivity and strong stability and has broad application prospects in the field of biosensing.