Carbon Dot‐Based Hydrogels: Preparations, Properties, and Applications

Abstract

heat, electricity, magnetism, mechanics, and chemistry. For example, the involvement of nanoparticles has proved to be an effective strategy to impart multifunctional properties to the hydrogels. [11] As a composite material, nanoparticle hydrogel composites have made remarkable progress in the fields of biomedicine, [12,13] sensing, [14,15] advanced energy technology, [16] environment and industry. [17] For another example, fluorescent hydrogels have been constructed by introducing organic dyes, [18,19] lanthanides, [20,21] or semiconductor quantum dots [22] into the hydrogel system.CDs are a novel class of carbon-based nanomaterials, which can be viewed as the relatives of nanoparticles with contractible sizes (typically <10 nm). Compared with other nanoparticles, CDs have high photostability, [23] low cost, [24] good biocompatibility, [25] high water solubility, and tunable photoluminescence. [26] These intriguing properties afford CDs many potential applications in biomedicine, [27,28] sensing, [29,30] catalysis, [31,32] optoelectronic devices, [33][34][35] and anticounterfeiting. [36] The emergence of CDs solved the long-lasting drawbacks of traditional PL materials, such as the poor photostability of organic dyes, the high cost of lanthanides, and the toxicity of semiconductor quantum dots. Generally, CDs can be obtained by two strategies. One is the top-down route, in which the CDs are broken off from larger carbon species. The other is the bottomup route, in which the CDs are synthesized by using molecular precursors. [37] According to the micro-/nanostructure, formation mechanism, and precursors used, CDs are mainly divided into four categories: [38] graphene quantum dots (GQDs), carbon quantum dots (CQDs), carbon nanodots (CNDs), and carbonized polymer dots (CPDs). GQDs with one or multiple-layer graphite structure and apparent graphene lattices are generally gained by "top-down" prepared routes: oxidation of cutting bulky graphitized carbon materials. CQDs, CNDs, and CPDs are usually synthesized from biomass, small molecules, or polymers by assembling, polymerization, crosslinking, and carbonization by "bottom-up" routes. CQDs have graphitelike crystal lattices with surface functional groups, showing internal state luminescence and the quantum size confinement. CNDs also have a large number of functional groups on the surface, but the cores of CNDs contain amorphous carbon without apparent crystal lattices. [39] CPDs have unique "core-shell" nanostructures, consisting of carbon cores with Hydrogels have extremely high moisture content, which makes it very soft and excellently biocompatible. They have become an important soft material and have a wide range of applications in various fields such as biomedicine, bionic smart material, and electrochemistry. Carbon dot (CD)-based hydrogels are based on carbon dots (CDs) and auxiliary substances, forming a gel material with comprehensive properties of individual components. CDs embedding in hydrogels could not only solve their aggregation-caused quenching (A...

Room Temperature Phosphorescence Carbon Dots: Preparations, Regulations, and Applications

“…[11][12][13] At present, CDs can be broadly divided into graphene quantum dots (GQDs), carbon quantum dots (CQDs), carbon nanodots (CNDs), and carbonized polymer dots (CPDs) according to the distinct structures and properties. [14,15] GQDs have one or more layers of graphene sheets connected chemical groups on the surface, which usually obtained by "top-down" prepared methods. The lateral dimension of GQDs is generally much larger than their height.…”

Cellulose Luminescent Hydrogels Loaded with Stable Carbon Dots for Duplicable Information Encryption and Anti-counterfeiting

“…In view of the similar trends, the concentration of CDs had a significant impact on fluorescence intensity, consistent with the ACQ effect. 26,57 The differences between hydrogels and solutions lie in that the ACQ effect can be suppressed via CDs dispersion into polymer crosslinked network (solid matrix). 58 According to a previous report, 59 the molecular fluorophore of green fluorescing CDs based on citric acid and urea was 4-hydroxy-1H-pyrrolo[3,4-c]pyridine-1,3,6-(2H,5H)-trione.…”

“…on CDs surface provide the possibility of chemical fixation inside the hydrogel matrix. On the one hand, three-dimensional (3D) networks of hydrogel can provide the CDs with chemical stability, also contribute to inhibit the aggregation-caused-quenching (ACQ) effect of high concentration CDs . On the other hand, the introduced CDs improves the mechanical properties of the hydrogel as well as confers the material additional functionality such as information storage and anti-counterfeiting …”

“…On the one hand, three-dimensional (3D) networks of hydrogel can provide the CDs with chemical stability, also contribute to inhibit the aggregation-caused-quenching (ACQ) effect of high concentration CDs. 26 On the other hand, the introduced CDs improves the mechanical properties of the hydrogel as well as confers the material additional functionality such as information storage and anti-counterfeiting. 27 Based on the concepts of a green economy and sustainable development, the utilization of natural renewable resources as CDs carriers is a reasonable choice.…”

Synthetic strategies, properties and sensing application of multicolor carbon dots: recent advances and future challenges

“…Since then, developing fascinating CDs with versatile properties has received great attention in many fields. [7][8][9][10][11] The most predominant characteristic of CDs is that they have remarkable properties, such as tunable photoluminescence, 12 high fluorescence quantum yield (QY), 13,14 ease of surface functionalization, 15 good aqueous solubility, 16 superior biocompatibility, 17 and high photostability, 18,19 have received immense research attention, which enables CDs to be an excellent alternative to semiconductor quantum dots (QD) with a wide variety of promising applications in the fields of sensing, 20 bioimaging, 21 biomedicine, 22 electronic devices, 23 and anti-counterfeiting. 24 In the initial development stage of CDs, the main research focuses on the preparation of carbon dots, utilizing a large number of carbon sources and numerous approaches.…”