Fig. 2. (A) UV-vis absorption spectra of AuNPs for the detection of heparin with the concentrations of 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.7, 1 μg mL−1. The top curve shows the UV-vis spectrum of bare AuNPs. The inset shows the corresponding solution colors (from left to right). (B) R650/520 of the PDDA–AuNP system versus the concentration of heparin. The inset shows the linear range. Error bars represent standard deviations of measurements (n = 3).
