DNAzyme amplified dispersion state change of gold nanoparticles and its dual optical channels for ultrasensitive and facile detection of lead ion in preserved eggs

•Dual optical signals of gold nanoparticles, absorption and scattering, caused by the changes in dispersion state are used for analysis.•A dual-channel sensing platform based on fluorescence and Tyndall effect is achieved for Pb2+ detection in preserved eggs.•The amplification of DNAzyme pushes down the detection limit of Pb2+ in both modes to pM level. A dual-mode sensing platform for Pb2+ was constructed based on the dual optical channels of Au NPs system with the amplification of DNAzyme, and it was successfully applied for Pb2+ determination in preserved egg with satisfactory results. The presence of Pb2+ activated the DNAzyme and induced the dispersion change of Au NPs in high salt concentration. The sequent absorption change of Au NPs was translated to the fluorescence change of carbon dots through FRET, and the scattering change was transferred to grey value of images involving the Tyndall effect. Thus, a sensing platform based on fluorescence and colorimetric dual-technique was achieved for Pb2+ detection, under the optimized conditions. With the assistance of DNAzyme, the linear range of fluorometric and colorimetric method were 2.0 × 10-14 ∼ 8.0 × 10-10 mol/L and 2.4 × 10-13 ∼ 9.5 × 10-9 mol/L, respectively. The dual-mode sensing platform demonstrated its promising application in the environmental monitoring and food safety field.