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Advances in nanoscale science and engineering are providing new opportunities to develop promising adsorbents for environmental remediation. Here, hybrid aerogels are assembled from cellulose nanofibrils (CNFs) and carbon nanomaterials to remove cationic dye methylene blue (MB) and anionic dye Congo red (CR) in single and binary systems. Two classes of carbon nanomaterials, carbon nanotubes (CNTs) and graphene nanoplates (GnPs), are incorporated into CNFs with various amounts, respectively. The adsorption, mechanics and structure properties of the hybrid aerogels are investigated and compared among different combinations. The results demonstrate CNF–GnP 3:1 hybrid exhibits the best performance among all composites. Regarding a single dye system, both dye adsorptions follow a pseudo-second-order adsorption kinetic and monolayer Langmuir adsorption isotherm. The maximal adsorption capacities of CNF–GnP aerogels for MB and CR are 1178.5 mg g−1 and 585.3 mg g−1, respectively. CNF–GnP hybrid show a superior binary dye adsorption capacity than pristine CNF or GnP. Furthermore, nearly 80% of MB or CR can be desorbed from CNF–GNP using ethanol as the desorption agent, indicating the reusability of this hybrid material. Hence, the CNF–GnP aerogels show great promise as adsorption materials for wastewater treatment.

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In this study, we reported an environmentally benign method for the synthesis of silver nanoparticles (AgNPs) by using 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-oxidized cellulose nanofibrils (CNFs) as the only reducing agent and stabilizer under mild aqueous conditions. The AgNPs were tightly adhered to the CNF surface, and the resulting stable CNF–AgNP suspension can be used for rapid and selective detection of l-cysteine (Cys). The efficacy of the process relies upon the surface plasmon resonance properties of AgNPs and the aggregation effect of AgNPs in the presence of Cys. Under optimal ionic strength provided by NaCl, Cys interacted with AgNPs, leading to a change in yellow color of the CNF–AgNP to purple. The colloidal suspension showed high sensitivity (limit of detection of 49 nM) and rapid (5 min) and selective detection of Cys among 20 amino acids that make up human proteins, hence demonstrating great potential for analyzing practical samples.