Theoretical investigations of Tamm plasmon resonance for monitoring of isoprene traces in the exhaled breath: Towards chronic liver fibrosis disease biomarkers

• The present work discusses the detection of isoprene traces in the exhaled breath. • This idea is introduced for the first time according to the best of our knowledge. • The proposed sensor is configured as, [prism/Au/air cavity/(GaN/SiO 2 ) 10 ]. • The numerical simulations are obtained based on the transfer matrix method. • The obtained numerical results investigate high sensitivity of 300000 nm/RIU. Detection of blood-carried volatile organic compounds (VOCs) existing in the exhaled breath of humans is an attractive research point for noninvasive diagnosis of diseases. In this research, we have introduced a novel design of photonic crystals (PCs) for the detection of isoprene traces in the exhaled breath as a biomarker for liver fibrosis. To the best of our knowledge, this idea has been introduced for the first time. The proposed sensor structure contains a one-dimensional (1D) PCs covered with a cavity layer of air and a thin metallic layer of Au is attached on the top surface. Hence, the proposed sensor is configured as, [prism/Au/air cavity/(GaN/SiO 2 ) 10 ]. The main idea of the detection procedure is based on the changes in the levels of isoprene traces as the dry exhaled breath (DEB) fills the cavity layer. The transfer matrix method and the Drude model are adopted to calculate the numerical simulations and reflection spectra of the design. The essential key for sensing isoprene levels is the resonant optical Tamm plasmon (TP) states within the photonic bandgap. The obtained numerical results are investigated for both high and low concentrations of the isoprene trances. Due to the optimization route, the designed sensor could receive a relatively high sensitivity (S) of 0.323 nm/ppm or 300000 nm/RIU. Also, we have obtained a quality factor of 980 for ppm levels and a pronounced value of 5042 for ppb levels. This technique can be reducing the risk of infection during the taking of blood samples by syringe. Finally, the imposed gas sensor here could be of potential interest for monitoring several diseases based on the type and level of the exogenous VOC occurring in the exhaled breath.