Abstract:
This keynote talk will focus on discussing room temperature magnetic ordering of very Small Carbon Dots (CDs), Mat-Like Polyaniline Nanofibers (Mat-PANI) and a composite comprising CDs and Mat-PANI (CDs@Mat-PANI), the latter containing a small fraction (less than 1 wt%) of CDs. It will be explored the saturation magnetization (MS) of CDs, Mat-PANI and CDs@Mat-PANI at increasing temperature, from 5 K to 300 K, revealing a systematic decreasing trend, with a huge synergic effect demonstrated in the CDs@Mat-PANI system. The impressive MS enhancement in the CDs@Mat-PANI system (about 200% at 5 K and 40% at 300 K) will be discussed in terms of an electron transfer mechanism from Mat-PANI imine nitrogen-atoms to the encapsulated CDs. Changes in MS values revealed that a substantial electron density is transferred to the CDs at low (5 K) as well as at high (300 K) temperatures, which is supported by observation of CDs Photoluminescence (PL) redshift while within the CDs@Mat-PANI system. Band-bending and bandgap-renormalization calculations are claimed suitable to predict the observed redshift at higher (300 K) temperature as a result of the electron transfer mechanism, which is in excellent agreement with the PL data. Raman, x-ray diffraction and x-ray photoelectron spectroscopy data are used to support the electron transfer mechanism as well as the strong interaction of CDs with PANI within the CDs@Mat-PANI system, which double the crystalline domain size of Mat-PANI while reducing the tensile strain from about one third.
Biography:
Paulo Cesar de morais (H-62), PhD, was full Professor of Physics at the University of Brasilia (UnB) Brazil up to 2013, appointed as UnB’s Emeritus Professor (2014),appointed as Guest Professor of Huazhong University of Science and Technology China (2011), visiting Professor at Huazhong University of Science and Technology (HUST) China (2012-2015), appointed as Distinguished Professor at Anhui University (AHU) China (2016-2019),appointed as Full Professor at Catholic University of Brasília (UCB) Brazil (2018), appointed as CNPq-1A Research Fellowship since 2010. 2007 Master Research Prize from UnB, 2008-member of the European ERA NET Nanoscience Committee, Member of the IEEE-Magnetic Society Technical Committee, Senior Member of the IEEE Society, 2012 China’s 1000 Foreign Expert Recipient, and 2012 Academic Excellence Award from Brazilian Professor’s Union. He held two-years(1987-1988) post-doc position with Bell Communications Research New Jersey, USA and received his Doctoral degree in Solid State Physics (1986) from the Federal University of Minas Gerais Brazil. He graduated in both Chemistry (1976) and Physics (1977) at UnB. Professor Morais is member of the Brazilian Physical Society and the Institute of Electrical and Electronics Engineers IEEE. He has served as referee for more than 50 technical journals, takes part of the Editorial Board of more than 15 technical journals and has conducted research on nanomaterials for over 40 years. He is known for his research in preparation, characterization and applications of nanosized materials magnetic fluid, magnetoliposome, magnetic nanoemulsion, magnetic nanocapsule, magnetic nanofilm, magnetic nanocomposite, nanosized semiconductors, polymeric dots, carbon dots, and graphene quantum dots. With more than 500 published papers in peer reviewed journals, more than 14,500 citations, more than 250 international invited talks (35 countries), and 16 filed patents. He has appeared in recent World ranking of top scientists, such as 2020 Stanford, 2022-Research.com, 2023-AD Scientific Index, 2023 Research.com, 2024-Elsevier, ONE Research Community, 2025-AD Scientific Index, 2025-Research.com, and 2025 Stanford Elsevier.
