Label-Free LSPR Detection of Trace Lead(II) Ions in Drinking Water by Synthetic Poly(mPD-<i>co</i>-ASA) Nanoparticles on Gold Nanoislands

Using self-assembly gold nanoislands (SAM-AuNIs) functionalized by poly­(<i>m</i>-phenylenediamine-<i>co</i>-aniline-2-sulfonic acid) (poly­(mPD-<i>co</i>-ASA)) copolymer nanoparticles as specific receptors, a highly sensitive localized surface plasmon resonance (LSPR) optochemical sensor is demonstrated for detection of trace lead cation (Pb­(II)) in drinking water. The copolymer receptor is optimized in three aspects: (1) mole ratio of mPD:ASA monomers, (2) size of copolymer nanoparticles, and (3) surface density of the copolymer. It is shown that the 95:5 (mPD:ASA mole ratio) copolymer with size less than 100 nm exhibits the best Pb­(II)-sensing performance, and the 200 times diluted standard copolymer solution contributes to the most effective functionalization protocol. The resulting poly­(mPD-<i>co</i>-ASA)-functionalized LSPR sensor attains the detection limit to 0.011 ppb toward Pb­(II) in drinking water, and the linear dynamic range covers 0.011 to 5000 ppb (i.e., 6 orders of magnitude). In addition, the sensing system exhibits robust selectivity to Pb­(II) in the presence of other metallic cations as well as common anions. The proposed functional copolymer functionalized on AuNIs is found to provide excellent Pb­(II)-sensing performance using simple LSPR instrumentation for rapid drinking-water inspection