Residual toxicant detection device

A residual toxicant detection device, comprising:

• a first space cavity, comprising:
• a light source configured to emit a light with a specific wavelength range and disposed on a substrate;
• a lens separated from the light source by a first distance;
• and
• a fixing ring whose top configured to fix the lens, wherein the fixing ring has a funnel-shaped structure at an end by which the fixing ring fixes the lens, and a side wall of the funnel-shaped structure has an angle of inclination extended upwards at a part close to the light source:
• a second space cavity, comprising:
• a photo sensor configured to receive the light with the specific wavelength range and obtain a sensing signal;
• and
• a circuit module electrically connected to the light source and the photo sensor;
• a connecting frame configured to connect the first space cavity and the second space cavity;
• and
• a sensing cavity formed between the first space cavity and the second space cavity and on one side of the connecting frame and configured to receiving an aqueous solution, wherein the light emitted by the light source of the first space cavity passes through the sensing cavity to enter the photo sensor of the second space cavity.