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- From copper-based nanoparticles to carbon-based dotsPublication . Fernandes, Joaquim Duarte Gonçalves; Pires, Pedro Filipe Duarte Louzeiro; Alves, Carla Sophia Brazão Andrade SousaNanoparticles (NPs) prepared from earth-abundant metals have attracted significant consideration for their potential as viable replacements for expensive metals used in many commercial chemical processes. In this context, copper NPs are particularly appealing since copper (Cu) is vastly abundant and cheap. Cu also displays good electronic, optical, antimicrobial, and chemical properties. Yet, CuNPs are limited due to their intrinsic instability under atmospheric conditions, making them prone to oxidation. Various efforts have been made to increase the stability of CuNPs, including investigating Cu-based NPs associated with organic structures such as polymers. This project was focused on the preparation and characterization of long-term stable Cu-based NPs using different synthesis strategies and without employing harmful reagents or solvents. Based on previously reported methods, the particles were synthesized using the environmentally friendly ascorbic acid (AA) as a reducing agent. Polyamidoamine (PAMAM) dendrimers and polyvinylpyrrolidone (PVP) were used as both templates and capping agents, and the reactions were done at room temperature and 60°C. The samples were characterized using various techniques, including Ultraviolet-Visible Spectroscopy (UV-Vis) and Scanning Electron Microscopy (SEM) coupled with EnergyDispersive X-ray Analysis (EDX). The results indicated the presence of Cu0, Cu1+, and Cu2+-based particles with diverse shapes (e.g. polyhedral, spherical, and disk-like). Moreover, other techniques like Photoluminescence Spectroscopy (PL), X-ray Photoelectron Spectroscopy (XPS), and Transmission Electron Microscopy (TEM) indicated the presence of Carbon-based Dots (C-Dots), which are responsible for the fluorescence properties of the solution. The formation of the C-Dots is thought to be the result of the side reaction of the reduction of the Cu ions (i.e., the oxidation of AA). Preliminary cytotoxic evaluation studies using the MTT assay showed that the particles obtained using PAMAM and PVP, as well as the C-Dots, did not present significant toxicity towards HEK 293T cells at concentrations below 500, 5, and 200µg/mL, respectively.