Ultra-low concentrations of detection for fluoride and trivalent chromium ions by multiple biomimetic nanochannels in a PET membrane

Abstract

The development of a detection method for fluoride and chromium (III) ions using a PET membrane with multiple biomimetic nanochannels is descibed. An asymmetric chemical etching technique was used to create conical nanochannels with a PET (polyethylene terephthalate) nuclear track membrane. SEM images showed that the pore diameter of the tip and base sides of the nanochannel were ∼40 nm and ∼180 nm, respectively. The compounds (4-aminophenyl) boronic acid (APBA) and 5-amino-2-nitrobenzoic acid (ANBA), with a specific recognition for F− and Cr3+ respectively, were modified by a conventional method with EDC and NHS. The current-voltage (I–V) curves of the modified PET membranes in response to the target ions at different concentrations were measured with a picoammeter. Excellent linear relationships between the current value of the I–V curve at −2 V and the concentration of Cr3+ and F− were established to obtain standard detection curves for Cr3+ and F−. From these relationships unknown concentrations of Cr3+ and F− can be quantitatively detected, and the results showed that the detection limits of Cr3+ and F− were as low as 4.10 nM and 0.46 nM, respectively. The performance of the novel method was compared to conventional ICP-MS analysis by the determination of Cr3+ in tap water and samples of the Jing Mi diversion canal, and good agreement was found between the two methods. The accuracy and reliability of the method has demonstrated its potential applicability to a wide range of other ionic contaminants.