Banca de DEFESA: ANA CAROLINA COSTA SOARES

Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.
STUDENT : ANA CAROLINA COSTA SOARES
DATE: 15/06/2023
TIME: 09:00
LOCAL: Auditório do IF
TITLE:

Luminescent nanoparticles for sensing in the SWIR region

KEY WORDS:

Luminescent nanothermometers; Core-shell engineering; Biological
windows; Fluorescent imaging; Thermal imaging; Luminescent sensors.

PAGES: 94
BIG AREA: Ciências Exatas e da Terra
AREA: Física
SUMMARY:

Research on luminescent nanothermometers (LNTs) is constantly growing due to the
need to read and control the temperature of various physiological processes that occur,
among others, in biological systems such as tissues, cells and living organisms, enabling
the diagnosis and treatment of diseases. In this sense, nanoparticles (NPs) doped with rare
earths ions have stood out for presenting several advantages such as having a wide
spectral range from ultraviolet to infrared. Thus, they have luminescent properties within
the three biological windows (BWs), which are regions where autofluorescence,
dispersion and absorption of light by biological tissues are minimized, allowing less
influence of the environment under study. In this thesis, we explore emissions and
excitations within the BWs, as both are extremely important. The main focus of our study
was the short-wave infrared (SWIR) emissions/excitation, which basically operates from
0.7 to 2.5 μm, mainly within the BW-II (1, 0 - 1.35 μm) and BW-III (1.5 - 1.9 μm).
However, in an early part of our work, which focused on the effects of core-shell structure
engineering, we explored emissions at BW-I (0.65 – 0.94 μm) under excitation at the
minimum of the BW-I. In this part we demonstrate that the core-shell engineering, which
allows the spatial separation of the emitting elements and, therefore, a control of the
energy transfer processes between ions and ions to defects, has a very important role to
maintain the spectral form of the NPs emissions in the presence of biological material.
Despite the promising applications of LNTs, concerns have arisen about their reliability
due to tissue-induced spectral distortions that are present even in BW-II that have been
heavily exploited recently. We present an innovative solution to this problem,
demonstrating the effectiveness of shifting the operating range of these LNTs to BW-III.
Through experimental evidence using CaF2 NPs tri-doped with ytterbium, erbium and
thulium, we demonstrate that the luminescence spectra acquired in BW-III are minimally
distorted by the presence of tissue, paving the way for reliable LNTs. In addition,
advanced analysis (Multiple Linear Regression) of the emission spectra allows obtaining
subdegree thermal uncertainties. Aware of the strong absorption of water in the spectral
region between BWs II and III (1.4 and 1.5 μm), we explored single-doped LaF3 NPs
with Tm3+ as a potential humidity sensor through the use of emissions at 1230 (in JB -II)
and 1470 nm. The results showed a reduction greater than 97% in the emission intensity
at 1470 nm with the presence of a 2 mm water film, resulting in a relative sensitivity
between 0.083 – 0.125 %μm-1

for the smallest water films, demonstrating to be a potential
luminescent humidity sensor. Experiments are underway for a comparative study with
commercial and other humidity sensors.

BANKING MEMBERS:
Interno(a) - 1695829 - ANDRE DE LIMA MOURA
Presidente - 1545463 - CARLOS JACINTO DA SILVA
Externo(a) à Instituição - ERVING CLAYTON XIMENDES
Externo(a) à Instituição - NELSON GUILHERME CASTELLI ASTRATH
Externo(a) à Instituição - TASSO DE OLIVEIRA SALES