Fig. 4: Ultralow detection limit with Pd periodic array sensor.
From: Inverse designed plasmonic metasurface with parts per billion optical hydrogen detection
a Δλpeak response to stepwise decreasing H2 concentration (1000–0.25 ppm) in Ar carrier gas at room temperature. Inset: zoomed-in version of the sensor response to 250 ppb H2. The slight baseline drift likely arise from minor adjustments in the setup over the course of the experiment70. b Measured Δλpeak as a function of H2 concentration derived from (a). Gray dashed line is a guide to the eye and extrapolates the sensor response to the 3σ value (0.03 nm, red dashed line), indicating a LoD ~200 ppb (red dashed arrow). Inset: SEM image of the fabricated sensor. c and d are the data from a control quasi-random array sensor analogous to (a) and (b). The control sensor responds comparably to the periodic array sensor but suffers from its higher noise. Hence, its LoD is ~8 times higher at 1.5 ppm.
