Colorimetric sensor strips for lead (II) assay utilizing nanogold probes immobilized polyamide-6/nitrocellulose nano-fibers/nets.

A facile, ultrasensitive, reproductive and selective sensor strip utilizing electrospun polyamide-6/nitrocellulose (PA-6/NC) nano-fibers/nets (NFN) membranes assemble bovine serum albumin decorated Au nanoparticles (BAu probe) for naked-eye colorimetric assay of Pb²⁺ has successfully prepared through dual-component alternate distribution multifluidic electrospinning technique. Benefiting from the extremely large specific surface areas and high porosity of NFN membranes, the stability of BAu probe dramatically increased and the strips presented a significant absorbance decreasing band at 546 nm which induce the visual color changes from deep pink to white after incubated in Pb²⁺ liquor with a low detection limit of 0.2 μM without any assistance of equipment. Upon exposure to a series of metal ions, only Pb²⁺ could induce a pink-to-white color change, which clearly exhibited that BAu probe immobilized PA-6/NC membranes could act as highly selective strips to detect Pb²⁺ with little interference from other metal ions. Additionally, the colorimetric responses are represented in visualized quantitative by calculated color difference from L*a*b* coordinates which are presented with lightness and chrome values. Furthermore, the sensitivity of NFN membrane-based strips is much higher than that of film-based ones. The results indicate that this promising cost-effective sensing system could potentially allow for assaying of Pb²⁺ in human urine or blood as preliminary screening of lead poisoning.