Sensitive colorimetric detection of Pb2+ by geometric field amplification and surface plasmon resonance visualization

Pb2+ is one of the major environmental pollutants, which can be visually detected by surface plasmon resonance of nanoparticles. Paper based analytical device, as a newly developed microfluidic detection platform, is featured in cost-effective and suitable for on-site analysis. In this paper, a sensitive and portable detection method for Pb2+ was proposed, in which Pb2+ was electrokinetically stacked on the paper fluidic channel by geometric field amplification effect and visualized online by glutathione-modified silver nanoparticles. Colorimetric quantification of the visualized stacking band was conducted by smart phone camera. To avoid unfavorable influence from pH change on the surface plasmon resonance visualization, field amplification effect was introduced by geometric design of the paper fluidic channel. The enriched Pb2+ was clearly visible on the paper substrate, and the stacking band intensity was about four orders of magnitude enhanced, comparing to the intensity without stacking. A linear response to Pb2+ was observed in the range of 0.3-7.0 mu M (R-2 = 0.997) with a limit of detection of 86 nM and a limit of quantity of 0.28 mu M. The established method was used in the detection of Pb2+ from river and lake water samples, and the results were confirmed by atomic absorption spectroscopy method.