Exploring smartphone-based environmental sensors through applying perovskite quantum dots

• Perovskite QDs was successfully applied to extend the sensing range of Si-cameras. • Smartphone-based environmental sensors were explored based on perovskite QDs. • A smartphone-based solar UV radiation sensor was developed to detect UV index. • A smartphone-based water COD sensor was developed to measure water quality. Smartphone have been applied to develop various sensors. However, because of the limitations of the Si detectors used in smartphone cameras, they can only detect visible light, which greatly restricts their functions for advanced sensor development. Herein, we extended the detection range of smartphone cameras to ultraviolet (UV) region by using perovskite quantum dots (QDs), which have excellent down-converting properties. We realized two smartphone-based environmental sensors. (1) A solar UV radiation sensor in which the perovskite QDs convert UV light to visible light that is detected by the smartphone camera. Coupled with app , this ingenious sensor can detect the solar UV index and also visualize the UV-radiation distribution. (2) A water chemical oxygen demand sensor that based on UV absorption. The sensor was realized by adding a simple attachment to the front of the smartphone camera. It can be used as an in-pocket sensor to measure water quality anytime and anywhere.