RESUMO
A green, fast and effective multivariate method for the determination of atrazine (ATZ) was developed using conventional infrared equipment furnished with an attenuated total reflectance module (ATR-IR), providing limit of detection (LOD) and limit of quantification (LOQ) in the ranges from 1.9 to 4.6 µg/mL and from 5.6 to 14 µg/mL, respectively. Furthermore, the surface-enhanced infrared absorption (SEIRA) approach was investigated to improve the sensitivity of the measurements and detect ATZ at low concentrations, addressing the compatibility with reference methods. To this end, a substrate formed by silver selenide quantum dots stabilized with mercaptopropionic acid (Ag2Se/MPA), synthesized in aqueous medium by an one-pot synthesis, was used. The spectral data were investigated by univariate and multivariate calibrations, allowing to calculate the enhancement factor (EF) and the multivariate enhancement factor (MEF), respectively. The SEIRA strategy proved to be able to enhance the atrazine signal up to 86-fold, allowing the detection of ATZ at concentrations as low as 0.001 µg/mL.
RESUMO
The development of multimodal nanoprobes has been growing in recent years. Among these novel nanostructures are bimodal systems based on quantum dots (QDs) and low molecular weight Gd3+ chelates, prepared for magnetic resonance imaging (MRI) and optical analyses. MRI is a technique used worldwide that provides anatomic resolution and allows distinguishing of physiological differences at tissue and organ level. On the other hand, optical techniques are very sensitive and allow events to be followed at the cellular or molecular level. Thus, the association of these two techniques has the potential to achieve a more complete comprehension of biological processes. In this review, we present state-of-the-art research concerning the development of potential multimodal optical/paramagnetic nanoprobes based on Gd3+ chelates and QDs, highlighting their preparation strategies and overall properties.