Banca de DEFESA: JEFFERSON AUGUSTO DE OLIVEIRA GALINDO

Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.
STUDENT : JEFFERSON AUGUSTO DE OLIVEIRA GALINDO
DATE: 30/03/2022
TIME: 09:00
LOCAL: https://meet.google.com/iwx-xymv-twf
TITLE:

Luminescence-based nanothermometry with single lanthanide codoped yttria nanoparticles and individual nitrogen-vacancy defects in nanodiamonds

KEY WORDS:

Luminescence nanothermometry. Lanthanide ions. Nanodiamond. Electron spin resonance. Scanning optical microscopy.

PAGES: 137
BIG AREA: Ciências Exatas e da Terra
AREA: Física
SUMMARY:

In the last two decades, the development of luminescent materials at nanoscale presenting temperature-dependent optical properties have led to the emergence of the so-called luminescence-based nanothermometers. Nowadays, these sensing devices are the main responsible for unveiling the temperature related phenomena at the sub-micron scale being used, for instance, to measure temperature distributions inside living cells and to detect hotspots on nano/microcircuits. However, despite temperature measurements with nanometric spatial resolutions can be achieved with these thermometers, most of the current literature on luminescence nanothermometry report ensemble average data. The careless about the particular characteristics of each nanothermometer may lead to important inaccuracies in the temperature measurements. Therefore, in this work, the thermal sensing capabilities of individual luminescent nanothermometers are investigated through the use of two different techniques in a temperature range compatible with biological systems.  More specifically, this Thesis reports and discuss two experimental studies on nanothermometry, which the first one relies on characterize the same five individual Yb³⁺/Er³⁺ codoped yttria nanocrystals (NCs) as nanothermometers when embedded in different environments (air, water and ethylene glycol) applying the Luminescence Intensity Ratio (LIR) technique. The second study reports on the characterization of three individual nanodiamonds containing a single negatively charged nitrogen-vacancy defect () as nanothermometers via Optically Detected Magnetic Resonance (ODMR) technique. The obtained results implementing the intensity ratio show that the thermometric behavior of each NC in air and water are equivalent, returning relative sensitivities and thermal resolutions as high as 2.3 % K^-1 and 0.4 K, respectively. It was also observed that the measured thermometric parameters, as thermal resolution and relative sensitivity, from each nanothermometer can be much more precisely determined than those from the average on the set of five NCs. The increased uncertainties of the average parameters are related to the nanocrystals' size variations, which manifests through the differences on the surface/volume ratio between the selected NCs. This assumption is reinforced by the observation of a correlation between the single-NC thermometric parameters with the NC brightness, with a dependence that is consistent with the expected variation in the surface/volume ratio. Besides, the relevance of the NC-solvent interaction becomes evident when the NCs are embedded in ethylene glycol, for which molecular vibrational modes can resonantly interact with the Er³⁺ ions electronic excited states used in the present experiments. Meanwhile, results on nanothermometry with single  defects on nanodiamonds also present differences on the measured thermal parameters between the selected nanothermometers. A linear dependence of the electron spin resonances with temperature were observed through ODMR measurements for the three nanodiamonds and varies from 88 kHz K^-1 to 110 kHz K^-1. The distinct thermal responses may be due to the presence of structural defects, impurities and inner strain of each nanodiamond. This argument is reinforced by the observed correlation between the measured strain parameter and the temperature dependency of the ESR frequencies for each nanodiamond. The obtained results corroborate those obtained for the individual lanthanide-doped nanothermometers. Also, an Arduino-based ESR tracking system is implemented to monitor continuous temperature changes of the sample with a nanodiamond during long times (~1h), resulting in thermal resolutions as high as 1.7 K. Such system may be implemented to measure the spatial temperature inhomogeneities of nanometric structures with spatial resolution limited only by the size of the nanothermometer (~25 nm). Therefore, the results reported in this Thesis point out to the importance of the calibration of individual luminescent nanothermometers and its interaction with the surrounding medium, reinforcing the thermal sensing capabilities with ultra-high spatial resolution of individual NCs codoped with lanthanide ions and single  defects on nanodiamonds.

BANKING MEMBERS:
Externo à Instituição - NIKIFOR RAKOV GOMEZ - UNIVASF
Externo à Instituição - ANDRE DE LIMA MOURA - UFAL
Presidente - 2199294 - LEONARDO DE SOUZA MENEZES
Interno - 1133583 - LUCIO HORA ACIOLI
Interno - 1452123 - MARCIO HERACLYTO GONCALVES DE MIRANDA