Contribuição ao projeto de sistemas multianalíticos baseados em ressonância de plasmons de superfície.

Abstract

This work presents the development of a Surface Plasmon Resonance (SPR) portable system. The proposed solution aims to transform a portable commercial computing device, such as smartphone, tablet or a notebook, in an instrument able to analyze organic and inorganic substances. In this way considerably reduces the cost compared with conventional devices based on SPR , besides providing the use in remote locations and turn possible to applying in several purposes by any users, such as residencial exams for disease prevention and water quality analysis. It was demonstrated the possibility to use the device’s screen to generate the light source for excite the SPR effect, which turns the system flexible to modify the light wavelength used and acquire additional information compared to conventional systems. The results showed that it is possible to excite SPR effect through a polychromatic light to the angular interrogation mode, finding the desired influence of wavelength component using a software filter in captured image signal. Furthermore it was proposed to use SPR curve morphological analysis for substance identification to be measured, which reduces the computational complexity and increases the instrument sensitivity. The morphological analysis results demonstrated the possibility of identify characteristics didn’t observed by monitoring the resonance condition. Monitoring the values of the SPR line broadening Gamma and asymmetry G, it was observed effects of changes in solute and surface conditions. To minimize the spurious variables effect, it was proposed a mathematical model that allow analyze the signal noise relationship of the system that was decomposed in each basic component. In this model was considered the control variables available, as light source’s current and camera integration time, further the temperature influence. Based in this model it was demonstrated that light source wavelength drifts is more critical than temperature effect. Thus it was proposed two ways for control the light source, changing the current for maintain constant the wavelength without temperature control.