Desenvolvimento e aplicação de sensores ópticos miniaturizados para análise de gases e voláteis em amostras ambientais, alimentícias e biológicas

Abstract

The real-time detection of gases and volatile compounds is of extreme importance for ensuring safety in enclosed environments (e.g., methane and sulfur dioxide) and even for diagnosing diseases (e.g., isoprene and acetone). In this context, the development of portable sensors is essential for preventive interventions and risk reduction. This work advances in that direction by developing innovative optical analytical platforms, exploring various regions of the electromagnetic spectrum and combining different technologies, such as waveguides, portable spectrometers, quantum cascade lasers (QCLs), LEDs, and photodetectors. The first study focused on the development and validation of a portable platform for the direct monitoring of ozone in indoor environments. Using a low-pressure mercury vapor mini-lamp as the radiation source and an aluminum sample cell based on an integrated hollow waveguide (iHWG), this platform proved effective in real-time ozone detection. The system, coupled with a portable USB spectrometer, was able to detect ozone concentrations at levels that meet safety requirements for enclosed environments, proving to be a fast and portable solution for continuous air quality monitoring. In the second study, a portable solution was developed for the quantification of sulfite in beverage samples. Utilizing an iHWG as the gas cell, an LED emitting at 280 nm, and a photodiode as the detector, the device minimizes the use of chemical reagents and offers a fast, sustainable, and cost-effective alternative for sulfite analysis. This approach enabled the detection of sulfite concentrations in a compact device. The third study explored the fabrication of iHWGs through 3D printing for the detection of isoprene and acetone vapors, two important biomarkers. Using a deuterium lamp as the UV radiation source and a portable spectrometer, the innovation of 3D printing to create customized and efficient gas cells highlights technological advancements, allowing the analysis of volatile organic compounds through a low-cost, portable analytical platform. Finally, the fourth study focused on developing a portable sensor for detecting toxic gases in underground mines. Combining quantum cascade lasers, iHWGs, and MCT detectors, the sensor was effective in detecting gases such as CH₄, SO₂, H₂S, and CO₂. The system’s high sensitivity and specificity, along with its portability, make it ideal for continuous and remote monitoring, allowing for quick interventions in hard-to-reach areas and reducing the risk of accidents in mining environments. Each study explored different combinations of radiation sources and detectors, optimizing their detection capabilities through strategies like gas conversion (H₂S to SO₂) and volatilization. The multidisciplinary approach and technological innovations achieved in this work open new horizons for the rapid and precise detection of toxic and volatile gases, providing viable and accessible solutions for challenges in both industrial and biomedical environments and environmental safety contexts.