TheQuantum dots excellent optical and electronic properties of nanostructures have opened a wide range of possibilities for technological applications in renewableRenewable energy energyEnergy, especially in high efficiency solar cells. These lecture notes begin with an introduction to the different types of existing semiconductor nanostructures according to the degree of spatial confinement of the charge carriers and some examples of their optical propertiesOptical properties are given. Then, the use of carbon as an environmentally friendly alternativeAlternative for the fabrication of quantum dotsQuantum dots, which can be synthesized from algae, is discussed. This could be considered a strategy that can help mitigate, in some way, problems such as sargassumSargassum invasion events on CaribbeanCaribbean beaches. In the end, some preliminary results obtained on carbon quantum dotsQuantum dots synthesized using green, brown, and red algal pigments are discussed.