Projeto e implementação de um espectrômetro de emissão de baixo custo com sonda Raman

Abstract

This final undergraduate thesis presents the design and implementation of a low-cost spectrophotometer aimed at detecting Raman scattering. The system was developed as a standalone instrument, starting with the optical methodology, which included the development of an orthogonal Raman collection probe and a custom spectrometer based on a transmission optical configuration. The spectral calibration was performed using a two-point linear model, referencing two lasers at 532 nm and 632.8 nm. The electronic architecture was centered on two microcontrollers: an STM32F401RE, dedicated to the temporal control and data acquisition from the TCD1304DG linear CCD sensor, and an ESP32-WROOM for processing, graphical interface on a TFT display, and Wi-Fi communication via a TCP/IP server. The results demonstrated the independent success of the subsystems: the probe validated its ability to collect identifiable Raman spectra from acetone and ethanol when coupled to a commercial instrument; the transmission spectrometer validated its functionality for high-intensity signals, faithfully reproducing the reference’s spectral profile. However, in the final integration, the complete system proved incapable of detecting the Raman signal, which remained submerged in the detector noise floor. It is concluded that the low-cost approach, based on transmission optics, suffers from cumulative signal losses (low light transport efficiency) that are catastrophic for the photon-scarce regime of Raman scattering. This work empirically demonstrates that the high light transport efficiency, characteristic of reflective architectures, is a fundamental requirement for the feasibility of Raman spectroscopy.