Chemical versus physical grafting of photoluminescent amino-functional carbon dots onto transparent nematic nanocellulose gels and aerogels

Abstract

Transparent matrices of low refractive index are promising carriers for photoluminescent nanoparticles targeting true volumetric 3D display applications. Complementation of transparency with a highly open-porous nanomorphology renders respective hybrid gels and aerogels additionally attractive for liquid and gas detection devices. Herein, we present virtually fully bio-based hybrids obtained by decorating highly transparent, nematically ordered gels and aerogels (15-20 mg cm-3) from carboxylated and individualized cellulose nanofibers (i-CNF) with amino-functional photoluminescent carbon dots (CD). The latter were obtained by microwave-assisted hydrothermolysis of lemon juice. As the way of anchoring the CDs onto the large internal surface of the porous i-CNF scaffolds (320 m 2 g-1) has a great impact on the final properties of the hybrid materials including leaching of CDs and reusability of the hybrid, this study assessed the respective pros and cons of a physical and chemical bonding approach. The results confirmed the superiority of covalent grafting. Aqueous carbodiimide coupling of aminofunctionalized CDs afforded higher yields of CDs in the final hybrid aerogels, distinctly higher specific surface values (491 m 2 g-1) and slightly enhanced mechanical properties while the high light transmittance and nanomorphology of the i-CNF precursor alcogels is virtually not compromised. Therefore, we conclude that the luminescent i-CNF/CD-chem hybrid materials of this study are promising candidates for environmentally friendly chemical sensing and volumetric display applications. Sakeena Quraishi and Sven F. Plappert contributed equally to this work.

Understanding Nanocellulose–Water Interactions: Turning a Detriment into an Asset

“…In this section, we focus on surface modification approaches that aim to decrease the hydrophilicity of nanocelluloses and the role of water in these reactions. This often-termed “hydrophobization” of nanocellulose leads to the disruption of the solvation of surface structures by water by capping the available hydroxy groups through the attachment of hydrophobic moieties, − grafted polymers, − or even nanoparticles. − Generally, the reasons to hydrophobize the surface of nanocellulose include increasing the hygromechanical stability (keeping good mechanical properties in the wet state), improving the compatibility with hydrophobic polymers or solvents or reducing the effects of hornification upon drying. ,− The palette of the available modification pathways is very diverse, and a full review of these reactions is out of the scope of this paper. The reader is encouraged to follow the details of modification reactions in the previous publications on this topic. , , , , , , ,, , , , , , , − However, a short overview of the most important routes to nanocellulose surface hydrophobization is covered here and summarized in…”

Recyclable Fe3O4/MWCNT/CNF composite nanopaper as an advanced negative electrode for flexible asymmetric supercapacitors

“…Compared to the pristine MWCNTs, the spectrum of the MWCNT/Fe 3 O 4 nanocomposite exhibits a Fe-O absorption peak at 588 cm −1 and a weak peak at around 3335 cm −1 , which is caused by the stretching vibration of O-H. 39 The peaks of CNFs at around 3335, 2902, 1606, 1324, 1056, and 899 cm −1 are observed in the case of the NFT@Fe composite nanopaper, corresponding to the O-H stretching vibration, C-H stretching vibration, C-O asymmetric stretching vibration, C-H bending vibration of sp 3 C, C-O stretching vibration, and C-H bending vibration. [45][46][47][48][49] However, the stretching vibration peak of Fe-O is not observed because it may be obscured by the complex and high-intensity ngerprint area of the CNF in the 500-800 cm −1 range. Notably, the -C]O stretching vibration peak of NFT@Fe at 1734 cm −1 is more intense than that in the spectrum of the pristine CNF because of the interaction between Fe 3 O 4 and carboxyl.…”

Current State of Applications of Nanocellulose in Flexible Energy and Electronic Devices

“…As shown is Figure 9, Quraishi et al (2019) presented highly transparent bio-based hybrid films obtained by carboxylated CNF and decorated with amino-functional photoluminescent carbon dots. They concluded that the fabricated luminescent hybrid materials are promising candidates for sustainable volumetric display applications.…”

“…FIGURE 9 | CNF aerogels with covalently coupled CDs under laser beam of 100 mW at 405 nm crossing through the soft gels, and scheme showing covalent bonds. Reprinted with permission fromQuraishi et al (2019). Copyright (2019) Springer Nature.…”