Imaging of anti-counterfeiting devices: An 850 nm LED from Thorlabs (M850L3) was used as the excitation source. A camera (Kiralux 8.9 MP Color CMOS Camera) was mounted with an imaging lens to take pictures of the substrates. Images were taken under 200 ms exposure time. See SI Figure . Excitation power was measured using a power meter (PM100D meter with S120VC sensor). NOTE: the image of Memorial Church was taken under waveguided excitation due to the large size (2 inch x 2 inch) of the substrate. The absorption spectrum of 50 mg/mL PbS on glass (encapsulated) was collected on a UV-vis-NIR spectrometer. After background subtracting, the absorbance at 808 nm (SI Figure ) was converted to percent absorption using SI equation 1. The absorption of 25, 10, and 5 mg/mL were calculated as described below. %Absorption = 100 × (1-10 -Abs ) SI Equation Method 1: Percent absorption based on solid-state absorption spectrum.