Naked‐Eye Heterogeneous Sensing of Fluoride Ions by Co‐Polymeric Nanosponge Systems Comprising Aromatic‐Imide‐Functionalized Nanocellulose and Branched Polyethyleneimine

Abstract

Heterogeneous colorimetric sensors for fluoride ions were obtained by cross‐linking TEMPO‐oxidized cellulose nanofibers (TOCNF) with chemically modified branched polyethyleneimine 25 kDa (bPEI). Functionalization of bPEI primary amino groups with aromatic anhydrides led to the formation of the corresponding mono‐ and bis‐imides on the grafted polymers (f‐bPEI). A microwave‐assisted procedure allowed the optimization of the synthetic protocol by reducing reaction time from 17 h to 30 minutes. Hydrogels obtained by mixing different ratios of TOCNF, bPEI and f‐bPEI were lyophilized and thermally treated at about 100 °C to promote the formation of amide bonds between the amino groups of poly‐cationic polymers and the carboxylic groups of cellulose nanofibers. This approach generated a series of cellulose nanosponges S1‐S3 which were characterized by FT‐IR and by solid state 13C CPMAS NMR. These sponge materials can act as colorimetric sensors for the selective naked‐eye recognition of fluoride ions over chloride, phosphate and acetate ions at concentrations of up to 0.05 M in DMSO. Moreover, when the sponges were functionalized with perylene tetracarboxylic diimide, successful naked‐eye detection was achieved with only 0.02 % w/w of chromophore units per gram of material.

TEMPO-Nanocellulose/Ca2+ Hydrogels: Ibuprofen Drug Diffusion and In Vitro Cytocompatibility

“…The TOUS-CNFs obtained are of about 10 nanometers width and a length in the range of 200-400 nm (Figure 2a), in line with data reported in the literature [15,16]. It has been reported how aqueous dispersions of these nanofibers exhibit rheological properties typical of thixotropic materials [28]. By varying TOUS-CNFs concentrations, the rheological behavior moves from low viscous suspensions to highly viscous gels when increasing the amounts of dispersed nanofibers (Figure 2b).…”

“…Obtaining aqueous dispersions of nano-dimensioned fibers is facilitated by the use of a ultra-sonication process [20][21][22][23]. TEMPO oxidized and ultra-sonicated cellulose nanofibers (TOUS-CNFs) have been reported as versatile building blocks for the design of nanostructured materials with a wide range of potential applications [24][25][26][27][28][29][30][31][32].…”

Suitability of a Cellulose-Based Nanomaterial for the Remediation of Heavy Metal Contaminated Freshwaters: A Case-Study Showing the Recovery of Cadmium Induced DNA Integrity Loss, Cell Proliferation Increase, Nuclear Morphology and Chromosomal Alterations on Dreissena polymorpha

“…These materials possess a 2D sheet-like morphology and are characterized by a high micro-porosity, as revealed by scanning electron microscopy (SEM) [28] and microcomputed tomography (µCT) analysis [27]. More interestingly, CNS also shows a nano-porosity, as revealed by in-depth small angle neutron scattering (SANS) and Fourier Transform Infrared Spectroscopy (FT-IR) studies [29], and can be also easily functionalized to confer the material additional properties, including ion sensing [30]. The high porosity allows to favor the contacting between metal ion analytes and active sites of the sponge, consisting in the cooperative chelating action of vicinal amino groups.…”

Nanostructured Cellulose-Based Sorbent Materials for Water Decontamination from Organic Dyes

“…In recent years, we modified the CNS formulation by adding an optimized amount of citric acid (CA) as an additional source of carboxylic groups, in order both to strength the mechanical properties of the final material by increasing cross-linking nodes [ 12 ], and to better fix bPEI into the network, so that it was also possible to reduce the amount of the same polymer and to support an eco-safe and sustainable design [ 13 , 14 ]. Moreover, we also demonstrated the versatility of the system, with the possibility of grafting bPEI with suitable moieties before undergoing cross-linking, in order to give the material additional functional properties, such as the sensing of fluoride ions [ 15 , 16 ].…”