Novel fluorescent nanocellulose hydrogel based on gold nanoclusters for the effective adsorption and sensitive detection of mercury ions

Mercury is a major pollutant of water. An efficient adsorbent for mercury ions is urgently needed. In this study, we developed a novel fluorescent nanocellulose hydrogel (NH) based on cellulose nanocrystals and gold nanoclusters with high adsorption ability (maximum adsorption capacity: 95.7 mg/g for Hg(II)) and high detection sensitivity and selectivity for Hg(II). The chemical structure, physical structure, and Hg(II) adsorption and detection characteristics of novel NH were characterized. Moreover, the mechanism analysis confirmed that cellulose nanocrystals provided a natural skeleton to construct the three-dimensional (3D) porous structure for accelerating Hg(II) adsorption and provided chemical functional groups to increase the number of effective sorption sites for improving Hg(II) adsorption capacity; gold nanoclusters wrapped in the 3D porous structure of the NH served not only as a fluorescent probe for a visual response for Hg(II), but also as sorption sites facilitating the adsorption of Hg(II) ions. Owing to these factors, the novel NH has considerable potential for use in the removal of Hg(II) ions from wastewater.