Nanosensors are chemical and mechanical sensors that can be used to detect the presence of chemical species and nanoparticles. These are any biological or surgery sensory points used to convey information about nanoparticles to the macroscopic world. A sensor is an instrument that responds to a physical stimulus. It collects and measures data regarding some property of a phenomenon, object, or material. Particles that are smaller than the characteristic lengths associated with the specific phenomena often display new chemistry and new physics that lead to new properties that depend on size. Nanosensors can be chemical sensors or mechanical sensors. Amongst other applications they can be used: To detect various chemicals in gases for pollution monitoring, for medical diagnostic purposes either as blood borne sensors or in lab-on-a-chip type devices, to monitor physical parameters such as temperature, displacement and flow. Typically nanosensors work by monitoring electrical changes in the sensor materials.