Ulva rigida, a common green seaweed, was used as a feedstock for the production of bioethanol in a simultaneous saccharification and fermentation (SSF) process carried out under sonication. Sonication provided a faster way for the simultaneous release of glucose from Ulva rigida and its conversion into bioethanol. Within 3 h, 196 ± 2.5 mg glucose per gram of dry weight of biomass and 333.3 ± 4.7 mg bioethanol per gram of glucose were produced in the SSF process under sonication. In addition to being fast, the process was devoid of any chemical pretreatment and involves only a single stage of sonication for the release of glucose from algae by the action of enzymes and also for the simultaneous fermentation of glucose to ethanol using Saccharomyces cerevisiae.

In the recent decade, carbon dots have drawn immense attention and prompted intense investigation. The latest form of nanocarbon, the carbon nanodot, is attracting intensive research efforts, similar to its earlier analogues, namely, fullerene, carbon nanotube, and graphene. One outstanding feature that distinguishes carbon nanodots from other known forms of carbon materials is its water solubility owing to extensive surface functionalization (the presence of polar surface functional groups). These carbonaceous quantum dots, or carbon nanodots, have several advantages over traditional semiconductor-based quantum dots. They possess outstanding photoluminescence, fluorescence, biocompatibility, biosensing and bioimaging, photostability, feedstock sustainability, extensive surface functionalization and bio-conjugation, excellent colloidal stability, eco-friendly synthesis (from organic matter such as glucose, coffee, tea, and grass to biomass waste-derived sources), low toxicity, and cost-effectiveness. Recent advances in the synthesis and characterization of carbon dots have been received and new insight is provided. Presently known applications of carbon dots in the fields of bioimaging, drug delivery, sensing, and diagnosis were highlighted and future applications of these astounding materials are speculated.