Espectroscopia Raman amplificada por superfície com nanopartículas de Ni, Co e Bi para a detecção de biomoléculas e microrganismos

Abstract

In this dissertation we demonstrate plasmonic activity of Ni, Co and Bi nanoparticles, with emphasis on Surface-Enhanced Raman Scattering (SERS), for the detection of biomolecules (amino acids and urea) and microorganisms such as fungi (C. Albicans, C. Glabrata, C. Kefyr, C. Tropicalis, C. Guilliermondii and Fusarium sp., F. Pedrosoi, F. Pugnacius and F. Monophora). Nanoparticles were synthesized via laser ablation in liquid medium and the obtained colloids were used to intensify Raman signals in experiments in which drops of nanoparticles were added to the analytes, allowing the mixture to dry to obtain the SERS spectra. The colloids were also used for the production of substrates, through the “drop-casting” technique, with nanoparticles being deposited on glass slides in the presence of magnetic fields, in order to produce homogeneous films with potential for application in SERS experiments. In the former case, the analytes were also deposited onto substrates for SERS spectra measurements. Several characterization techniques were used: UV-Vis spectroscopy, dynamic light scattering (DLS), transmission (TEM) and scanning electron microscopy (SEM), energy dispersion spectroscopy (EDS), atomic force microscopy (AFM) and optical profilometry. To obtain the vibrational spectra of the analytes, a confocal Raman spectrometer was used, with an excitation laser at 532nm. SERS spectra were compared to those obtained using Au nanoparticles, showing that Ni, Co and Bi are promising materials for the development of SERS-based biosensors. In particular, our results demonstrate that these nanoparticles have the potential to be used for the identification and differentiation of fungi (genus and species).