Antonino Madonia¹,Gianluca Minervini^2,3,1,Annamaria Panniello¹,Carlo Carbonaro⁴,Teresa Sibillano¹,Cinzia Giannini¹,Angela Terracina⁵,Alice Sciortino⁵,Fabrizio Messina⁵,Maria Lucia Curri^3,1,Marinella Striccoli¹

CNR¹,Polytechnic of Bari²,University of Bari “Aldo Moro”³,University of Cagliari⁴,Università degli Studi di Palermo⁵

Abstract

CNR¹,Polytechnic of Bari²,University of Bari “Aldo Moro”³,University of Cagliari⁴,Università degli Studi di Palermo⁵

Designing functional nanomaterials useful for the development of optoelectronic devices is a challenging task. Industry standards demand careful control over both their structural and optical properties, as well as high reliability and resistance to degradation under real-world usage conditions. Furthermore, the development of cost-effective materials obtained from inexpensive, abundant, and environment-friendly sources is deemed a high priority. In this context Carbon Dots (CDs) have gained much traction. These nanoparticles, mainly composed of Carbon and other readily available elements such as Oxygen, Nitrogen, and Hydrogen, are considered extremely promising for their enticing properties: it is thanks to their intense absorbance, bright photoluminescence, low toxicity and high biocompatibility that such nanomaterials have found their way into the fields of optoelectronics, photocatalysis, and nanosensing among the others.[1] In fact, CDs are renown for being able to couple molecular-like optical properties to an enhanced photostability,[2] characteristics which work in parallel to their electron-donating capabilities towards the development of hybrid and functional materials.[3] In recent years the understanding of the relationship between synthetic conditions, structural features, and optical properties of CDs has witnessed impressive progress. Nonetheless, while we are now able to produce carbon-based nanoparticles with high photoconversion efficiencies both in the blue and green regions of the visible light spectrum,[4] the knowledge regarding how to control the synthesis of red-emitting CDs is still lagging behind;[5] as many optical applications necessitate full control over all visible wavelengths, we need to design new synthetic strategies allowing us to overcome this obstacle. It is with this purpose in mind that we have explored novel approaches aimed at enhancing the red emission of carbon nanoparticles. By developing both synthetic and post-synthetic treatments we were able to isolate CDs displaying high photoluminescence quantum yields in the red region of the light spectrum. Moreover, we have been successful in finely tuning their optical properties by the careful choice of precursors used during the solvothermal synthesis: these results have been achieved by making use of both in-situ surface passivation strategies as well as post-synthetic purification approaches. The synthesized red CDs possess exciting optical properties and result highly resistant to photobleaching under UV irratiation. An in-depth optical and morphological characterization has allowed to rationalize the mechanisms underlying the emission properties of CDs and isolate the centers responsible for the red photoluminescence. These advances can envisage the effective use of carbon dots as viable substitutes for the semiconductor nanoparticles currently used in the domain of optoelectronics, which are often based on toxic and polluting materials. As we are now able to cover the visible light spectrum in its full range, we have been exploring the possibility of using the carbon-based functional nanomaterials for the development of tunable or white light-emitting devices, as first step towards the application in many other photonic or optoelectronic devices. The Italian MIUR PRIN 2017 Candl2 Project Prot. n. 2017W75RAE is gratefully acknowledged. [1] Sciortino, A. et al. C 4, 67 (2018). [2] Terracina, A. et al. ACS Appl. Mater. Interfaces (2022). [3] Madonia, A. et al. Phys. Chem. Chem. Phys. 24, 17654–17664 (2022); Madonia, A. et al. Materials Research Bulletin 149, 111721 (2022); Madonia, A. et al. J. Phys. Chem. Lett. 11, 4379–4384 (2020). [4] Minervini, G. et al. Carbon 198, 230–243 (2022). [5] Carbonaro, C. M. et al. C 5, 60 (2019).