  In nanomechanical photothermal absorption spectroscopy and microscopy, the
measured substance becomes a part of the detection system itself, inducing a
nanomechanical resonance frequency shift upon thermal relaxation. Suspended,
nanometer-thin ceramic or 2D material resonators are innately highly-sensitive
thermal detectors of localized heat exchanges from substances on their surface
or integrated into the resonator itself. Consequently, the combined
nanoresonator-analyte system is a self-measuring spectrometer and microscope:
responding to a substances transfer of heat over the entire spectrum for which
it absorbs, according to the intensity it experiences. Limited by their own
thermostatistical fluctuation phenomena, nanoresonators have demonstrated
sufficient sensitivity for measuring trace analyte as well as single particles
and molecules with incoherent light or focused and unfocused coherent light.
They are versatile in their design, support various sampling methods and
hyphenation with other spectroscopic methods, and are capable in a wide range
of applications including fingerprinting, separation science, and surface
sciences.
