Fig. 1.

Fluorescence imaging of spontaneous generation of H₂O₂ in a typical straight-channel microfluidic chip. (A) Schematic image of experimental setup of water–solid interface in the microfluidic chip. (B) Schematic image of fluorescence microscopy setup for imaging the microfluidic chip. (C) Digital image of fluorescence emission of the microfluidic chip. The sample in the chip contains 1 mM H₂O₂-sensitive probe as shown in (B). (D) The fluorescence microscopy image of the sample in the chip highlighted in the white dashed line frame in (C) (Scale bar, 300 µm). (E) The relationship between fluorescence intensity and reaction time of sample resting in microfluidic chip. (F) Calibration curve at 400 nm from the absorption spectrum of potassium titanium oxalate (PTO) solution with added H₂O₂. Abs, absorption. The green star represents the concentration of H₂O₂ generated from the microfluidic chip. The excitation source is a green laser pointer (530 nm).