Green and transparent cellulose nanofiber substrate-supported luminescent gold nanoparticles: A stable and sensitive solid-state sensing membrane for Hg(II) detection

Abstract Mercury(II) pollution is a growing threat to the environment and humanity. But most of the solution-based Au nanomaterial sensors suffer from low stability seriously. Here, inspired by high-affinity metallophilic Hg2+–Au(I) interaction mechanism, we introduced a transparent cellulose nanofiber matrix-supported luminescent gold nanoparticle (AuNPs) stable sensing membrane. In this solid-state membrane, the AuNPs with strong red fluorescence emission were synthesized as the sensor unit. Cellulose nanofibrilatted (CNF) matrix was fabricated as the supporting substrate. With a large specific surface area, the nanostructured CNF matrix offers abundant immobilizing spots to the sensor unit of AuNPs. More importantly, the excited fluorescence can escape directly without apparent scattering loss due to the high transparency of the CNF substrate. With strong emission of the AuNPs, coupled with abundant AuNP immobilizing spots and high transparency of the CNF substrate, the fluorescence signaling path was manipulated sequentially from signal generation, transmission until to quenching, resulting in the membrane demonstrates high sensitivity, selectivity, and stability. The detection limit of 1.0 nM is markedly lower than the threshold level of 10.0 nM permitted by US EPA. Aided with the high-performance membrane, the detection of Hg(II) becomes simple, fast, easy handing, and green. We envision the membrane will be an attractive material for Hg(II) monitor.