Over the past several decades, the disposal of dyes from the industrial manufacturing sector has had an inadvertent impact on water ecology as polluted water bodies with these hazardous dyes...

Carbon quantum dots (CQDs), a new family of photoluminescent 0D NPs, have recently received a lot of attention. They have enormous future potential due to their unique properties, which include low toxicity, high conductivity, and biocompatibility and accordingly can be used as a feasible replacement for conventional materials deployed in various optoelectronic, biomedical, and energy applications. The most recent trends and advancements in the synthesizing and setup of photoluminescent CQDs using environmentally friendly methods are thoroughly discussed in this review. The eco-friendly synthetic processes are emphasized, with a focus on biomass-derived precursors. Modification possibilities for creating newer physicochemical properties among different CQDs are also presented, along with a brief conceptual overview. The extensive amount of writings on them found in the literature explains their exceptional competence in a variety of fields, making these nanomaterials promising alternatives for real-world applications. Furthermore, the benefits, drawbacks, and opportunities for CQDs are discussed, with an emphasis on their future prospects in this emerging research field.

Over the past few decades, the disposal of various industrial pollutants such as organic dyes, heavy metal ions, pesticides, and phenolic compounds has led to the deterioration of the quality of freshwater; even with the 70% water coverage over the earth, there is meager access to freshwater sources. Against the drawbacks of conventional water purification methods such as sludge production and generation of toxic byproducts, the adsorption process is regarded as an efficient and economical strategy for the treatment of wastewater. Among various available adsorbents, cyclodextrin-based nanosponges have evolved as prominent adsorbents for treating wastewater and are considered a cost-effective option with minimal energy and time requirements. Owing to their porous nature, cone-like structure, cross-linked three-dimensional network, and special architecture of the hydrophilic and hydrophobic moieties wherein the hydrophobic core can form inclusion complexes with pollutants via host−guest interactions while hydrophilic edges interact with pollutants through hydrogen-bonding and electrostatic interactions, they are effective adsorbents for the removal of a variety of pollutants such as heavy metals, organic dyes, phenols, and pesticides. Additionally, the number of active sites in these nanosponges could be enhanced by hybridizing with other adsorbents or by functionalization with magnetic nanoparticles. This review deliberates various water purification methods and underlines the limitations of using other conventional methods over adsorption. The strategies to synthesize β-cyclodextrin-based nanosponges deploying various cross-linkers and their further modifications have been discussed in detail. Finally, the application of these nanosponges for the effective removal of assorted pollutants from wastewater highlighting the adsorption mechanism in certain cases is cogitated.

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