Microsteganography on WS Monolayers Tailored by Direct Laser Painting.

We present scanning focused laser beam as a multipurpose tool to engineer the physical and chemical properties of WS microflakes. For monolayers, the laser modification integrates oxygen into the WS microflake, resulting in ∼9 times enhancement in the intensity of the fluorescence emission. This modification does not cause any morphology change, allowing "micro-encryption" of information that is only observable as fluorescence under excitation.