Electrical Impedance Measurements of DNA Molecules and Gold Nanoparticles at low Temperatures

• Autor(a) principal: Martins, Alexandre Olas de Sousa
• Data de Publicação: 2019
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10362/91155
• topic: Impedance Spectroscopy; Electrical Impedance; DNA; Gold Nanoparticles; Interdigitated Sensor; Low Temperatures; Domínio/Área Científica::Engenharia e Tecnologia::Outras Engenharias e Tecnologias

Strand breaks occur naturally in the deoxyribonucleic acid (DNA) chain. Studies have shown that the amount of breaks increases with exposure to ultraviolet (UV) light. Additionally, it has been shown that low energy electrons, with energies below DNA’s ionization energy, are capable of also inducing strand breaks on DNA. These breaks alter the length of the DNA molecule which in turn alters its electrical impedance. As such, the amount of strand breaks can be indirectly measured through an impedance spectroscopy (IS). This work presents the construction of a cryogenic unit capable to hold an interdigitated sensor, with a sample of DNA or DNA with gold nanoparticles (AuNPs), allowing IS measurements to occur. This cryogenic unit is able to withstand temperatures in the range of 77 to 300 K, while monitoring the temperature at which its sample is. Liquid nitrogen was used as the cold source, allowing the low temperatures mentioned above to be reached. Since the heating process lasts around 8 h, depending on the amount of liquid nitrogen used, it becomes hard to manually start a measurement at the appropriate time. To counter this, a user interface was developed that monitors the temperature, automatically starting a measurement when a temperature defined by the user is reached. Overall, a cryogenic system was built which can be applied in the future for the study of DNA and DNA+AuNPs thin films.