Sensor and method for detecting mercury

Organosilane functionalised carbon nanoparticles comprising a carbon dot bonded to a first organosilane functionalization agent, the organosilane functionalization agent having a free end and a fixed end, wherein the organosilane functionalization agent is bonded to the carbon dot in a first orientation in which one or more functional groups capable of binding mercury are located at or proximal to the free end and the fixed end of the organosilane functionalization agent is bonded to the surface of the carbon dot with Si—O—Si and/or Si—O—C bonds;

• and
• a second organosilane functionalization agent that neighbors the first organosilane functionalization agent and has a functional group that neighbors the functional group in the first organosilane functionalization agent, wherein the neighboring functional groups from the neighboring organosilane functionalization agents together form a coordinating cage that binds mercury.