Detection of tea polyphenols based on a taper-in-taper infrared fiber sensor

Accurate detection of tea polyphenols is essential for tea quality control and authenticity identification. Conventional methods involve complex pretreatment, high costs, and susceptibility to interference, while standard infrared spectroscopy is limited by strong water absorption in liquid samples. This study presents an infrared fiber evanescent wave sensor based on Ge 15 As 27 Se 40 Te 18 glass for highly sensitive, rapid detection of tea polyphenols. Through evanescent field simulation, a micro-ring structure was fabricated within a taper-in-taper fiber region (waist diameter: 200/50 μm, bending radius: 0.75 mm) to enhance sensitivity. The sensor demonstrated high sensitivity (1.52 a.u./(vol%)) and a low limit of detection (LoD = 0.18 vol%), representing a 3.26-fold improvement over pre-optimized configurations. Leveraging infrared spectroscopy and evanescent wave sensing, the sensor successfully analyzed tea polyphenols in commercial products and tablets, achieving a sensitivity of 0.062 a.u./(mg·mL −1 ) and a LoD of 0.25 mg/mL.This method enables quantitative analysis and functional group identification in food.