Adsorbent sponges for water remediation were prepared using TEMPO-oxidized cellulose nanofibers (TOCNFs) as three-dimensional scaffolds, and branched polyethyleneimine (bPEI, 25 KDa) as the cross-linking agent. TOCNFs were suspended in aqueous solution in the presence of variable amounts of bPEI. The mixtures were first freeze-dried and then thermally treated (from 60 to 102 °C over 10 h) promoting the formation of amide bonds between the carboxylic groups of TOCNF and the primary amines of bPEI. The resulting materials, which were characterized by FTIR and 13C CP-MAS NMR spectroscopy, scanning electron microscopy, and elemental analysis, showed higher chemical and mechanical stability in water than non-reticulated cellulose composites. The high adsorption capability of the new sponges was verified for different organic pollutants (p-nitrophenol, 2,4,5-trichlorophenol, and amoxicillin), and heavy metal ion pollutants (Cu, Co, Ni, Cd), indicating their potential for water decontamination
Cyclodextrin nanosponges (CDNS) are a very\ud
promising class of cross-linked polymers, made up of\ud
cyclodextrins. CDNS swollen in aqueous solution give rise\ud
to cyclodextrin-based hydrogel in different states—gel or\ud
liquid suspension—depending on the hydration level of the\ud
system. Here we present a thorough inspection of the\ud
vibrational dynamics of these hydrogel by Raman scattering\ud
experiments, with the aim of clarifying the role played\ud
by the hydrogen-bond dynamics of water molecules confined\ud
into the nano-sized pores of nanosponges in determining\ud
the rigidity of the hydrogel network and their\ud
maximum water-holding capacity. Changes occurring in\ud
the spectral shape of the OH stretching band of water were\ud
interpreted by accounting the connectivity pattern of water\ud
molecules concurring to the gelation process. Spectral\ud
deconvolution analysis gives evidence of the existence of a\ud
characteristic cross-over hydration level associated to the\ud
rearrangement of water molecules in more cooperative,\ud
bulk-like networks as a consequence of saturation sites of\ud
water confinement of nanosponges. This interpretation is\ud
further confirmed by the inspection of the estimated collective\ud
intensities. These findings also support the existence\ud
of a specific phase diagram of the cyclodextrin nanosponges\ud
hydrogel, where the molecular structure of the crosslinking\ud
agent used during the synthesis of nanosponge\ud
plays a fundamental role in defining the nano- and microscopic\ud
properties of the system
Oxidized multiwalled carbon nanotubes were produced by strong acid treatment with the aid of sonication. Short-length carbon nanotubes obtained by filtration of the oxidized carbon nanotubes were analyzed by means of X-ray photoelectron spectroscopy, Raman and photoluminescence spectroscopies, and scanning electron microscopy. Direct evidence of the modifications of the electronic properties of the carbon nanotubes was obtained by the valence band analysis. The oxidation induced by the acid treatment led to deep changes of the carbon nanotubes density of states. Analysis of the photoluminescence spectra showed that the short carbon nanotubes are luminescent in the visible range. Interestingly, the spectral intensities and lineshapes are strongly dependent on the pH of the CNT solution. This effect is explained by a modification of the local environment of the defects induced by the protonation/deprotonation of the carboxylic groups formed by the oxidation process.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.