Fig. 1. AND logic gate 1 design and fabrication
(a) Scheme of AND logic gate 1 in the presence of no input (0, 0), Mel alone (1, 0), CTAB alone (0, 1) and both Mel and CTAB (1, 1);(b) Truth table; (c) Optical photographs; (d) Values of absorption ration (A₆₅₀/A₅₂₆) for the AND logic gate 1

Fig. 2. Transmission electron microscopy (TEM) images of AND logic gate 1
(a): (0, 0); (b): (1, 0); (c): (0, 1); (d): (1, 1)

Fig. 3. (a) The effect of the pH on melamine detection; (b) The effect of aptamer concentration on melamine detection, the concentrations of aptamer were from 0 to 36 nmol·L^-1; (c) The response time; (d) The optimization of temperature

Fig. 4. Sensitivity of the biosensor for melamine detection
The concentrations of melamine are 0.00, 0.05, 0.10, 0.15, 0.20, 0.30, 0.40, 0.50, 0.60, 0.70, 0.80, 0.90, 1.00, 1.10, 1.20, 1.30, 1.40, 1.50, 1.60, 1.70, 1.80, 1.90, 2.00 mg·L^-1. Inset: At low concentrations of melamine the data were fitted to a linear plot

Fig. 5. AND logic gate 2 design and fabrication
(a) Scheme of AND logic gate 2 in the presence of no input (0, 0), Cyr alone (1, 0), CTAB alone (0, 1) and both Cyr and CTAB (1, 1); (b) Truth table; (c) Optical photographs; (d) Values of absorption ration (A₆₅₀/A₅₂₆) for the AND logic gate 2

Fig. 6. Transmission electron microscopy (TEM) images of AND logic gate 2
(a): (0, 0); (b): (1, 0); (c): (0, 1); (d): (1, 1)

Fig. 7. (a) The effect of aptamer concentration on cyromazine detection, the concentrations of aptamer were from 0 to 36 nmol·L^-1; (b) The effect of the CTAB concentration on cyromazine detection, the concentrations of CTAB were from 0.6 to 3.0 μmol·L^-1; (c) The effect of the time on cyromazine detection, the time were from 0 to 16 min

Fig. 8. Sensitivity of the biosensor for cyromazine detection
The concentrations of cyromazine are 0.0, 0.05, 0.10, 0.15, 0.20, 0.25, 0.30, 0.35, 0.40, 0.45, 0.50, 0.60, 0.70, 0.80, 0.90, 1.0, 1.5, 2.0 mg·L^-1. Inset: At low concentrations of cyromaizne the data were fitted to a linear plot

Fig. 9. Selectivity of the assay for cyromazine detection over other veterinary drugs concentrations: cyromazine, ammelide, ammeline, aniline, L-tyrosine, cyanuric acid, L-lysine monoacetate, L-lysine monohydrochloride (500 μg·L^-1). The concentration of Tcy1 is 15 nmol·L^-1