title: Toxicological impact of cadmium-based quantum dots towards aquatic biota: Effect of natural sunlight exposure.
abstract: Cadmium-based quantum dots (QDs) are increasingly applied in existent and emerging technologies, especially in biological applications due to their exceptional photophysical and functionalization properties. However, they are very toxic compounds due to the high reactive and toxic cadmium core. The present study aimed to determine the toxicity of three different QDs (CdS 380, CdS 480 and CdSeS/ZnS) before and after the exposure of suspensions to sunlight, in order to assess the effect of environmentally relevant irradiation levels in their toxicity, which will act after their release to the environment. Therefore, a battery of ecotoxicological tests was performed with organisms that cover different functional and trophic levels, such as Vibrio fischeri, Raphidocelis subcapitata, Chlorella vulgaris and Daphnia magna. The results showed that core-shell type QDs showed lower toxic effects to V. fischeri in comparison to core type QDs before sunlight exposure. However, after sunlight exposure, there was a decrease of CdS 380 and CdS 480 QD toxicity to bacterium. Also, after sunlight exposure, an effective decrease of CdSeS/ZnS and CdS 480 toxicity for D. magna and R. subcapitata, and an evident increase in CdS 380 QD toxicity, at least for D. magna, were observed. The results of this study suggest that sunlight exposure has an effect in the aggregation and precipitation reactions of larger QDs, causing the degradation of functional groups and formation of larger bulks which may be less prone to photo-oxidation due to their diminished surface area. The same aggregation behaviour after sunlight exposure was observed for bare QDs. These results further emphasize that the shell of QDs seems to make them less harmful to aquatic biota, both under standard environmental conditions and after the exposure to a relevant abiotic factor like sunlight.
authors.affiliation: Department of Biology, Faculty of Science, University of Porto, Rua do Campo Alegre, 4169-007 Porto, Portugal; CIIMAR, Interdisciplinary Centre of Marine and Environmental Research, Rua dos Bragas, 289, 4050-123 Porto, Portugal.
authors.forename: B F
authors.initials: BF
authors.lastname: Silva
authors.affiliation: Centro de Investigação em Química da Universidade do Porto, Rua do Campo Alegre, 687, 4169-007 Porto, Portugal; Department of Chemistry and Biochemistry, Faculty of Science, University of Porto, Rua do Campo Alegre, 4169-007 Porto, Portugal; CITAB - Centre for Research and Technology of Agro-Environmental and Biological Sciences, University of Trás-os-Montes e Alto Douro, UTAD, Vila Real, Portugal.
authors.forename: T
authors.initials: T
authors.lastname: Andreani
authors.affiliation: Department of Biology, Faculty of Science, University of Porto, Rua do Campo Alegre, 4169-007 Porto, Portugal; CIIMAR, Interdisciplinary Centre of Marine and Environmental Research, Rua dos Bragas, 289, 4050-123 Porto, Portugal. Electronic address: anacsgavina@gmail.com.
authors.forename: A
authors.initials: A
authors.lastname: Gavina
authors.affiliation: Department of Biology, Faculty of Science, University of Porto, Rua do Campo Alegre, 4169-007 Porto, Portugal; CIIMAR, Interdisciplinary Centre of Marine and Environmental Research, Rua dos Bragas, 289, 4050-123 Porto, Portugal.
authors.forename: M N
authors.initials: MN
authors.lastname: Vieira
authors.affiliation: Centro de Investigação em Química da Universidade do Porto, Rua do Campo Alegre, 687, 4169-007 Porto, Portugal; Department of Chemistry and Biochemistry, Faculty of Science, University of Porto, Rua do Campo Alegre, 4169-007 Porto, Portugal.
authors.forename: C M
authors.initials: CM
authors.lastname: Pereira
authors.affiliation: Department of Chemistry and Centre for Environmental and Marine Studies (CESAM), University of Aveiro, Campus de Santiago, 3810-193 Aveiro, Portugal.
authors.forename: T
authors.initials: T
authors.lastname: Rocha-Santos
authors.affiliation: Department of Biology, Faculty of Science, University of Porto, Rua do Campo Alegre, 4169-007 Porto, Portugal; CIIMAR, Interdisciplinary Centre of Marine and Environmental Research, Rua dos Bragas, 289, 4050-123 Porto, Portugal.
authors.forename: R
authors.initials: R
authors.lastname: Pereira
mesh_terms: D048908:Aliivibrio fischeri / Q000187:drug effects; D000818:Animals; D019187:Cadmium Compounds / Q000528:radiation effects / Q000633:toxicity*; D000460:Chlorophyta / Q000187:drug effects; D003621:Daphnia / Q000187:drug effects; D045663:Quantum Dots / Q000528:radiation effects / Q000633:toxicity*; D013440:Sulfides / Q000528:radiation effects / Q000633:toxicity*; D013472:Sunlight; D014874:Water Pollutants, Chemical / Q000633:toxicity*; D017967:Zinc Compounds / Q000633:toxicity
chemical_list: D019187:Cadmium Compounds; D013440:Sulfides; D014874:Water Pollutants, Chemical; D017967:Zinc Compounds
keywords: Bacteria; Daphnia; Ecotoxicity; Microalgae; Quantum dots; Sunlight