Chiral Carbon Dots Synthesized on Cellulose Nanocrystals

Abstract

Hybrid nanoparticles composed of cellulose nanocrystals (CNCs) and carbon‐dots (C‐dots) have promising applications in chemistry, biology, and nanomedicine, owing to the photoluminescence, sensory properties, and cytocompatibility of C‐dots, and chirality, cytobiocompatibility, and high cellular uptake of CNCs. The possibility of circularly polarized luminescence in such nanoparticles is particularly attractive. Herein, scalable and straightforward hydrothermal synthesis of nitrogen‐doped fluorescent C‐dots under reflux condition by using CNCs as a carbon source and chiral substrate is reported. Under ultraviolet irradiation, hybrid C‐dot/CNC nanoparticles exhibit stronger emission of left‐handed, than right‐handed, circularly polarized light, with high dissymmetry factor up to 0.2. The nanoparticles are biocompatible: the normalized proliferation index above 100% is determined for MCF 7 cells cultured in the suspension of C‐dot/CNC nanoparticles. These hybrid nanoparticles can find applications as biotags for labeling, sensing, and therapeutics and as building blocks of photoluminescent cholesteric CNC films with photonic applications.

Carbon Dots: An Emerging Smart Material for Analytical Applications

“…Based on the significant findings, these hybrids have a promising application to remove autofluorescence drawbacks in bioimaging. The CD/CNC hybrids can also be effectively employed in sensing, drug delivery, and photonic applications as mirror-free cholesteric lasers [ 88 ]. In another interesting study, using the concept of donor–acceptor complex formation between CDs and porphyrins, the chirality of the carbon nanodots was transferred to the porphyrin.…”

Thermal Management by Engineering the Alignment of Nanocellulose

“…[ 63 ] For the applications discussed here, nanocellulose in the forms of isolated elementary nanofibrils and microfibrils is typically desired. [ 23–28 ] The geometry of nanofibers derived from different feedstocks also depends on the source of nanocellulose. For example, elementary nanofibrils derived from wood have lengths of 10–300 nm and diameters of 3–5 nm whereas those produced by bacteria have rectangular 5–10 nm by 30–50 nm cross‐sections and 100–1000 nm lengths, though the latter can be modified to achieve sub‐10 nm cross‐sections.…”

“…[ 1–5 ] Recently researchers used self‐assembly of cellulose nanocrystals to obtain helicoidal organizations that mimic naturally occurring reflectors found in the wings of beetles, like the ones shown in Figure 1d, where reflectivity of these films can be tuned in visible and near‐infrared regions ( Figure ). [ 23,25,27,29,42 ] Colloidal spindle‐shaped cellulose nanoparticles (Figure 2a,b) can be prepared from bacterial, wood or other sources. In concentrated aqueous colloidal dispersions, these anisotropic nanoparticles spontaneously self‐assemble into a cholesteric LC while continuously rotating around the helical axis χ (Figure 1e), with the distance of 2π‐rotation called “helical pitch”, p .…”

“…Such materials can be made from the most abundant biopolymer, cellulose, when derived from wood and even from dirty initial feedstocks like waste. [ 23–25 ] These bioinspired material designs can not only allow for more efficient energy uses, but also may enable solar heat harvesting, effectively transforming the current energy‐consuming buildings into power plants in the future. Moreover, the energy management within buildings can be combined with safe geoengineering [ 26 ] to mitigate the global climate change and local heat waves (especially in urban areas) by reflecting the excess solar radiation back into the space.…”

“…Moreover, the energy management within buildings can be combined with safe geoengineering [ 26 ] to mitigate the global climate change and local heat waves (especially in urban areas) by reflecting the excess solar radiation back into the space. While this research news mainly focuses on tunable solar reflectors and passive thermal barriers, [ 23–25,27–31 ] we note that the capabilities of radiative cooling can be potentially also added to these designs, including the ones based on wood‐derived naturally aligned cellulose. [ 32,33 ] While being developed to solve energy management problems here on Earth, various thermal management solutions are also needed for the exploration of space, like in extraterrestrial habitats.…”