resumo
There is an increasing demand for accurate, non-invasive and self-reference temperature measurements as technology progresses into the nanoscale. This is particularly so in micro-and nanofluidics where the comprehension of heat transfer and thermal conductivity mechanisms can play a crucial role in areas as diverse as energy transfer and cell physiology. Here we present two luminescent ratiometric nanothermometers based on a magnetic core coated with an organosilica shell co-doped with Eu3+ and Tb3+ chelates. The design of the hybrid host and chelate ligands permits the working of the nanothermometers in a nanofluid at 293-320 K with an emission quantum yield of 0.38 +/- 0.04, a maximum relative sensitivity of 1.5% K-1 at 293 K and a spatio-temporal resolution (constrained by the experimental setup) of 64 x 10(-6) m/150 x 10(-3) s (to move out of 0.4 K - the temperature uncertainty). The heat propagation velocity in the nanofluid, (2.2 +/- 0.1) x 10(-3) m s(-1), was determined at 294 K using the nanothermometers' Eu3+/Tb3+ steady-state spectra. There is no precedent of such an experimental measurement in a thermographic nanofluid, where the propagation velocity is measured from the same nanoparticles used to measure the temperature.
palavras-chave
INTRACELLULAR TEMPERATURE; FLUORESCENCE LIFETIME; THERMAL-CONDUCTIVITY; THERMOMETRY; NANOPARTICLES; NANOCRYSTALS; NANOSCALE; SENSORS; MECHANISMS; RESOLUTION
categoria
Chemistry; Science & Technology - Other Topics; Materials Science; Physics
autores
Brites, CDS; Lima, PP; Silva, NJO; Millan, A; Amaral, VS; Palacio, F; Carlos, LD
nossos autores
Carlos Brites
Professor Auxiliar
Luís Carlos
Professor Catedrático
Nuno João Silva
Investigador Principal
Patrícia Pereira Lima
Bolseiro de pós-Doutoramento
Vitor Brás Sequeira Amaral
Professor CatedráticoProjectos
agradecimentos
We acknowledge Fundacao para a Ciencia e a Tecnologia (FCT, Portugal), COMPETE and FEDER programs (Pest-C/CTM/LA0011/2011, PTDC/CTM/101324/2008) and Integrated Spanish-Portuguese Action PT2009-0131 for financial support. The work in Zaragoza has been supported by the grants MAT2011-25991 and CONSOLIDER CSD2007-00010 from the Ministry of Economy and Competitivity. CDSB (SFRH/BD/38472/2007) and PPL (SFRH/BPD/34365/2006) thank FCT for grants. NJOS acknowledges FCT for the Ciencia 2008 program. The authors are grateful to Victor Sorribas (Zaragoza) and Paulo Marques (IT - Aveiro) for the collaboration with the optical microscopy observations and temperature mapping measurements, respectively.