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Article

Upcycled Carbon Dots as Multifunctional Boosters for Broad-Spectrum Photostable Sunscreens

by
Gustavo Teixeira Machado
1,
Caio Rui Chiabai
1,2,
Isaac dos Santos Orgino
3,
Leticia Neves Ferraz
1,
Flavia Dayrell França
1,
Fábio Luiz Partelli
4,
Paulo Eduardo Narcizo de Souza
5,
Ana Sofia Fernandes
6,
Ana Luísa Gomes Júlio
6,
André Rolim Baby
2,
George Ricardo Santana Andrade
7,* and
Fabiana Vieira Lima Solino Pessoa
1,*
1
Department of Health Sciences, Federal University of Espírito Santo, São Mateus 29932-540, Brazil
2
Department of Pharmacy, Faculty of Pharmaceutical Sciences, University of São Paulo, São Paulo 05508-900, Brazil
3
Department of Natural Science, Federal University of Espírito Santo, São Mateus 29932-540, Brazil
4
Department of Agricultural and Biological Sciences, Federal University of Espírito Santo, São Mateus 29932-540, Brazil
5
Institute of Physics, University of Brasília, Brasilia 70910-900, Brazil
6
CBIOS, Universidade Lusófona’s Research Center for Biosciences & Health Technologies, 1749-024 Lisboa, Portugal
7
Postgraduate Program in Natural Science, Federal University of Espírito Santo, São Mateus 29932-540, Brazil
*
Authors to whom correspondence should be addressed.
Photochem 2025, 5(4), 32; https://doi.org/10.3390/photochem5040032
Submission received: 25 August 2025 / Revised: 23 September 2025 / Accepted: 6 October 2025 / Published: 13 October 2025
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Abstract

Sustainable ultraviolet (UV) filters that couple photoprotection with antioxidant activity are needed. Carbon dots (CDots) derived from agro-industrial waste have emerged as promising candidates. CDots were prepared from Coffea canephora (coffee leaf) residues by a one-pot microwave route and characterized by UV–Vis, FTIR, and TEM. Antioxidant capacity was determined by CUPRAC and DPPH-EPR. The photoprotective efficacy was assessed in vitro by diffuse reflectance spectrophotometry before and after solar-simulator exposure. Nearly spherical CDots (3.3 ± 0.7 nm) displayed a 4.16 eV optical bandgap and broad absorption from 200 to 400 nm. At 10 μg mL−1, CDots exhibited 24.62 ± 0.19% antioxidant activity relative to Trolox by CUPRAC, while by DPPH-EPR, they showed 99.9 ± 12.5% of radical quenching at 240 µg mL−1. Addition of 4.5% w/w (dry basis) CDots to the sunscreen system increased the in vitro SPF from 26 ± 13 to 161 ± 8 (p < 0.05) while maintaining the critical wavelength at 380 ± 0.64 nm. After 30 min of irradiation, the SPF dropped only 10%, versus 44% for the CDots-free sample (control), indicating superior photostability. Coffee leaf CDots acted as an efficient broadband UV absorber and antioxidant that markedly enhanced and stabilized a conventional sunscreen formulation. The work positions waste-derived CDots as an eco-friendly, next-generation multifunctional ingredient, aligning with circular economy principles.
Keywords: antioxidants; cytocompatibility; sun protection factor; photostability; Coffea canephora antioxidants; cytocompatibility; sun protection factor; photostability; Coffea canephora
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MDPI and ACS Style

Machado, G.T.; Chiabai, C.R.; Orgino, I.d.S.; Ferraz, L.N.; França, F.D.; Partelli, F.L.; de Souza, P.E.N.; Fernandes, A.S.; Júlio, A.L.G.; Baby, A.R.; et al. Upcycled Carbon Dots as Multifunctional Boosters for Broad-Spectrum Photostable Sunscreens. Photochem 2025, 5, 32. https://doi.org/10.3390/photochem5040032

AMA Style

Machado GT, Chiabai CR, Orgino IdS, Ferraz LN, França FD, Partelli FL, de Souza PEN, Fernandes AS, Júlio ALG, Baby AR, et al. Upcycled Carbon Dots as Multifunctional Boosters for Broad-Spectrum Photostable Sunscreens. Photochem. 2025; 5(4):32. https://doi.org/10.3390/photochem5040032

Chicago/Turabian Style

Machado, Gustavo Teixeira, Caio Rui Chiabai, Isaac dos Santos Orgino, Leticia Neves Ferraz, Flavia Dayrell França, Fábio Luiz Partelli, Paulo Eduardo Narcizo de Souza, Ana Sofia Fernandes, Ana Luísa Gomes Júlio, André Rolim Baby, and et al. 2025. "Upcycled Carbon Dots as Multifunctional Boosters for Broad-Spectrum Photostable Sunscreens" Photochem 5, no. 4: 32. https://doi.org/10.3390/photochem5040032

APA Style

Machado, G. T., Chiabai, C. R., Orgino, I. d. S., Ferraz, L. N., França, F. D., Partelli, F. L., de Souza, P. E. N., Fernandes, A. S., Júlio, A. L. G., Baby, A. R., Andrade, G. R. S., & Pessoa, F. V. L. S. (2025). Upcycled Carbon Dots as Multifunctional Boosters for Broad-Spectrum Photostable Sunscreens. Photochem, 5(4), 32. https://doi.org/10.3390/photochem5040032

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