Fluorescent Spherical Sponge Cellulose Sensors for Highly Selective and Semiquantitative Visual Analysis: Detection of Hg²⁺ and Cu²⁺ ions

Abstract

In this work, a novel sponge cellulose fluorescence spherical (CS–CDs) was prepared by an in situ microwave method using cellulose as a base material, polyethylenimine (PEI) as a nitrogen-doping reagent, and citric acid (CA) as an external carbon source. The CS–CDs were used for highly sensitive selective detection of Hg2+ and semiquantitative visual detection of Cu2+ in aquatic environments. Their excellent fluorescence properties and porous structure enable the CS–CDs to adsorb and detect these ions quickly and sensitively, and they can detect Hg2+ selectively with a detection limit of 26 nM. Additionally, an interesting phenomenon was observed where the color of the cellulose sphere changes continuously from inherent pale yellow to deep green as the Cu2+ adsorption increases from 3 to 60 μM, indicating that the CS–CDs can be used for semiquantitative visual detection of Cu2+. The fluorescence and visual detection limits for Cu2+ are 0.11 and 3 μM, respectively; these are both considerably lower than the allowable content of Cu2+ (20 μM) in potable water. The discoloration mechanism of Cu2+ adsorption by CS–CDs was studied. It can be considered that after CS–CDs adsorb Cu2+, a large amount of Cu2+ amine complexes form, aggregate, and concentrate on the cellulose sphere substrate to develop the color. Finally, we used the CS–CDs to analyze tap and river water based on highly reproducible results. This cellulose sponge-based device could be used to protect probes from environmental interference and is sufficiently stable to withstand at least 22 cycles of exposure to ethylenediaminetetraacetic acid.

N-alkylation briefly constructs tunable multifunctional sensor materials: Multianalyte detection and reversible adsorption

“…The XPS spectra of SPBI products were measured according to a previously reported method ( Yu et al., 2019 ; Li et al., 2021 ). As shown in Figure S11 A, the peaks located at 285.1, 397.6, and 528.1 eV were attributed to C1s, N1s, and O1s, respectively, in the backbone of SPBI-c .…”

Carbon dots crosslinked chitosan/cellulose sponge capture of methyl blue by an adsorption process

“…[ 12 ] The peak at about 1064 cm −1 can be assigned to the C–O–C vibrations from MCC. [ 32 ] The above results indicated the presence of –NH 2 , –COOH, and –OH groups on the surface of the CS/MCC/CA‐CDs sponge.…”

“…[ 39 ] The adsorption capacity increased significantly due to –NH 2 deprotonation at pH = 10. However, the structure of the CS/MCC/CA‐CDs sponge was destroyed due to the weakened hydrogen bonding under a strong alkali environment (pH > 10), [ 32 ] resulting in the sharp decrease in the adsorption capacity. The results showed the excellent adsorption performance of the CS/MCC/CA‐CDs sponge at pH 10.…”

Nanomaterial-Integrated Cellulose Platforms for Optical Sensing of Trace Metals and Anionic Species in the Environment

“…Applications have been mainly focused on Hg(II), Cu(II), and Se(IV). Table 2 shows main applications [ 72 , 73 , 74 , 75 , 76 , 77 , 78 , 79 , 80 , 81 , 82 , 83 , 84 , 85 , 86 , 87 , 88 , 89 , 90 , 91 , 92 ] where luminescent nanoreceptors are immobilized onto cellulose substrates for sensing trace elements. Direct deposition of the sample onto the PAD is considered here.…”