We
report here the fast fabrication of fluorescent carbon dots
(CDs) within several minutes by magnetic hyperthermia. This method
offers an alternative platform to prepare excitation-dependent fluorescent
CDs without any surface modification from various kinds of precursors
varying from polymers like poly(vinyl alcohol) (PVA) and polyethylene
glycol (PEG) to small organic molecules and salts like amino acid,
glucose, EDTA, citrate acid–urea, sodium citrate, zinc stearate,
and ammonium citrate. As an example, the magnetic hyperthermia synthesis,
characterization, optical properties, and in vitro cytotoxicity of
CDs obtained from ammonium citrate are thoroughly investigated. The
excitation-dependent fluorescence mechanism is discussed based on
the UV–vis absorption, excitation, and emission spectra as
well as the photoluminescence (PL) response to metal ions and pH.
These CDs are further used as ink for inkjet printing to produce fluorescent
patterns with uniform and stable PL useful for anticounterfeit and
optoelectronic applications. This magnetic hyperthermia method allows
the rapid fabrication of versatile CDs from a wide range of carbon
sources in a simple, low-cost, and easy-to-perform way.