Agradecimentos: The authors are grateful to the Brazilian agencies Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES (Finance code 001), Conselho Nacional de Desenvolvimento Científico e Tecnológico - CNPq (315838/2021-3, 409680/2021-4, 405620/2021-7, and 163330/2020-4), Brazilian Institute of Science and Technology in Bioanalytics (INCTBio) (CNPq grant no. 465389/2014–7), Brazilian Institute of Science and Technology (INCT) in Carbon Nanomaterials FAPEMIG, Fundação de Amparo à Pesquisa do Estado de Minas Gerais - FAPEMIG (RED-00042-16, APQ-03141-18, APQ-01207-17, and APQ-00282-21) for the financial support. W.T.P dos Santos wishes to thank CNPq (405620/2021-7) and FAPEMIG (PPM-00142-18) for financial support. K.F. da Cunha and J.L. Costa thank to the São Paulo Research Foundation – FAPESP (2018/00432-1 and 2018/11849-0) for financial support and W. O. Soté, and M. Comar Jr thank to Prof. Luiz Guilherme Machado de Macedo (UFSJ) for granting access to the computational infrastructure used for the simulations. R.V. Gelamo is grateful to FAPEMIG (APQ-01359-21) and CNPq (302582/2021-5). O.F. Lopes acknowledges Alexander von Humboldt Foundation by Return Fellowship. The authors also thank Prof. Valmor R. Mastelato (IFSC-USP) and Prof Waldir Avansi Jr (UFSCar) for XPS facilities, respectively. The authors would like to acknowledge the Multiuser Laboratories of the Universidade Federal de Uberlândia (RELAM-UFU) for providing the equipment and technical support for experiments involving electron microscopy (FAPEMIG grant APQ-02391-22) Ver menos

Abstract: 3,4-methylenedioxymethamphetamine (MDMA) is a drug of abuse, known as ecstasy, and it is among the most consumed drugs worldwide. The presence of MDMA and new psychoactive substances has been widely reported in seized forensic samples. The development of an elective and sensitive screening method for MDMA detection is very important in the current scenario of illicit drugs. In this paper, we present affordable graphite sheet (GS) electrodes a new sensing platform for MDMA detection. Importantly, a surface treatment protocol for these electrodes using cold plasma improves the electrochemical response of MDMA. The XPS results showed that O2 plasma treatment changed the GS electrode surface, creating oxide groups. GSs were characterized before and after treatment by scanning electron microscopy and electrochemical impedance spectroscopy, and the results suggested a higher surface area and lower resistance to the charge transfer for treated GS electrodes. Using differential pulse voltammetry, it was possible to achieve a linear range from 0.5 to 15.0 µmol L-1 with a low limit of detection (0.09 µmol L-1). Higher interaction of MDMA with the plasma-treated GS surface (in comparison with the pristine surface) was confirmed by computational simulations (molecular dynamics), which may explain the improved sensing properties provided by the plasma treatment. Additionally, the interference study with other drugs usually found in seized ecstasy tablets showed high selectivity which enabled MDMA detection in human saliva (collected in parties and electronic music festivals) and seized samples. Therefore, plasma-treated GS can be used as a simple, fast, low-cost, and portable screening device for application in real-world forensic samples Ver menos