Abstract A new method is presented for the visual detection
of dicyandiamide (DCD). Gold nanoparticles (AuNPs)
capped with gallic acid (GA) were synthesized in a single step
at room temperature, using GA as both the reducing agent and
stabilizer. In the presence of DCD, the hydrogen-bonding
interaction between GA and DCD induces the aggregation
of AuNPs, associated with a color change from red to gray that
can be observed with bare eye. DCD could be quantified by
photometry as the red shift of the maximal absorption band is
linearly related to the logarithm of concentration of DCD in
the 0.1 to 500 μM concentration range, with a regression
coefficient of 0.9987 and a 80 nM detection limit (at an
SNR of 3). The proposed method was successfully applied
to the detection of DCD in spiked dairy samples.