Banca de QUALIFICAÇÃO: HITALO DE JESUS BEZERRA DA SILVA

Uma banca de QUALIFICAÇÃO de DOUTORADO foi cadastrada pelo programa.
STUDENT : HITALO DE JESUS BEZERRA DA SILVA
DATE: 21/03/2024
LOCAL: Programa de Pós-Graduação em Ciência de Materiais
TITLE:

DEVELOPMENT OF NANOSENSORS FOR ANIONS BASED ON QUANTUM DOTS

KEY WORDS:

anions, detection, nanossensors, multivariate optimization, quantum dots.

PAGES: 111
BIG AREA: Outra
AREA: Multidisciplinar
SUMMARY:

Quantum dots (QDs) are fluorescent semiconductor nanocrystals which have gained attention for their unique optical and electronic properties, being employed in different applications. These nanometric semiconductors (2–10nm) exhibit optimal features for the development of sensors for a variety of analytes, as they possess a chemically active surface allowing the conjugation of molecules that could enhance their affinity with the analyte. Within the vast sensor landscape, an important branch is that comprising ion sensors based on QDs. These nanoprobes are appreciated for presenting high sensitivity and selectivity. Nevertheless, the development of sensors for metal cations is notably more explored than for anions, due to the greater complexity associated with the detection of these species. Despite the evident efficiency and great potential of sensors based on quantum dots (QDs), most of the QDs studied so far use nanocrystals that contain heavy metals in their composition (such as Pb and Cd), and are often prepared in organic media. In this context, this project main goal is the development of QDs-based sensors for anions. Moreover, it is expected to develop synthetic methodologies more sustainable to produce QDs in an aqueous medium and without heavy metals, which could be further used as sensors. Initially, aiming to develop hydrophilic nanosensors for anions, attempts were made using CdTe QDs stabilized with cysteamine (CYA), mercaptosuccinic acid (MSA), and glutathione (GSH) for the detection of CO32-, HCO3-, SO32-, and HSO4-anions. In parallel, studies were also carried out for the development of AgInSe2QDs in water through multivariate optimization. The sensors based on CdTe-CYAQDs showed superior performance to CdTe-MSA and CdTe-GSH QDs, demonstrating favorable optical properties and high photostability. The detection results revealed a gradual increase in the emission intensity of CdTe-CYAQDs, proportional to the addition of higher concentrations of anions, and furthermore, the QDs also showed selectivity towards the target anions, especially CO32-. On the other hand, multivariate optimization of the synthesis of AgInSe2QDs enabled the determination of optimal conditions for obtaining nanocrystals with enhanced emission intensity. For validation purposes, ANOVA and Ftest were used, demonstrating that the models have statistical significance and show no evidence of lack of fit at a 95% confidence level. Optical and structural characterizations demonstrated that the QDs have a broad absorption spectrum, characteristic of ternary QDs, and emission band at 735 nm, as well as effective surface passivation and formation of the orthorhombic crystal phase of AgInSe2. Finally, it is emphasized that it is of interest for this research to further functionalize these QDs with optimized emission for future applications, among which, detection of anions in aqueous media. 

COMMITTEE MEMBERS:
Externo à Instituição - IVO MILTON RAIMUNDO JUNIOR - UNICAMP
Presidente - 3218211 - MARCELLA AUXILIADORA DE MELO LUCENA
Externo ao Programa - 1271372 - MARCOS VINÍCIUS FOGUEL - null