Self-Calibrated Double Luminescent Thermometers Through Upconverting Nanoparticles

Luminescent nanothermometry uses the light emission from nanostructures for temperature measuring. Non-contact temperature readout opens new possibilities of tracking thermal flows at the sub-micrometer spatial scale, that are altering our understanding of heat-transfer phenomena occurring at living cells, micro electromagnetic machines or integrated electronic circuits, bringing also challenges of calibrating the luminescent nanoparticles for covering diverse temperature ranges. In this work, we report self-calibrated double luminescent thermometers, embedding in a poly(methyl methacrylate) film Er3+- and Tm3+-doped upconverting nanoparticles. The Er3+-based primary thermometer uses the ratio between the integrated intensities of the 2H11/2→4I15/2 and 4S3/2→4I15/2 transitions (that follows the Boltzmann equation) to determine the temperature. It is used to calibrate the Tm3+/Er3+ secondary thermometer, which is based on the ratio between the integrated intensities of the 1G4→3H6 (Tm3+) and the 4S3/2→4I15/2 (Er3+) transitions, displaying a maximum relative sensitivity of 2.96% K−1 and a minimum temperature uncertainty of 0.07 K. As the Tm3+/Er3+ ratio is calibrated trough the primary thermometer it avoids recurrent calibration procedures whenever the system operates in new experimental conditions

Upconversion Nanocomposite Materials With Designed Thermal Response for Optoelectronic Devices

Upconversion is a non-linear optical phenomenon by which low energy photons stimulate the emission of higher energy ones. Applications of upconversion materials are wide and cover diverse areas such as bio-imaging, solar cells, optical thermometry, displays, and anti-counterfeiting technologies, among others. When these materials are synthesized in the form of nanoparticles, the effect of temperature on the optical emissions depends critically on their size, creating new opportunities for innovation. However, it remains a challenge to achieve upconversion materials that can be easily processed for their direct application or for the manufacture of optoelectronic devices. In this work, we developed nanocomposite materials based on upconversion nanoparticles (UCNPs) dispersed in a polymer matrix of either polylactic acid or poly(methyl methacrylate). These materials can be processed from solution to form thin film multilayers, which can be patterned by applying soft-lithography techniques to produce the desired features in the micro-scale, and luminescent tracks when used as nanocomposite inks. The high homogeneity of the films, the uniform distribution of the UCNPs and the easygoing deposition process are the distinctive features of such an approach. Furthermore, the size-dependent thermal properties of UCNPs can be exploited by a proper formulation of the nanocomposites in order to develop materials with high thermal sensitivity and a thermochromic response. Here, we thus present different strategies for designing optical devices through patterning techniques, ink dispensing and multilayer stacking. By applying upconverting nanocomposites with unique thermal responses, local heating effects in designed nanostructures were observed

Probing Surface Effects on α-NaYF4 Nanoparticles by Nuclear Magnetic Resonance

The structural properties of insulating α-NaYF4 (cubic) nanoparticles with size ranging within 4-25 nm were investigated by high-resolution 23Na and 19F solid-state nuclear magnetic resonance (NMR) spectroscopy under magic angle spinning (MAS) with single-pulse (SP-MAS), spin-echo (SE-MAS), inversion recovery, and 3Q-MAS experiments. The 23Na SP-MAS spectra show a broad peak around -18 ppm with a shoulder around -9 ppm, which becomes more prominent for the smallest nanoparticles. The 23Na nuclei resonating around -9 ppm demonstrate a longitudinal relaxation time of a few milliseconds, while the ones resonating around -18 ppm are on the order of 50-125 ms. This feature is noticed for all studied nanoparticles, but it is more evident for the smallest ones (φ ≲ 7 nm), especially among the batches with higher polydispersity. On the basis of these relaxation times, field-dependent measurements, and 23Na 3Q-MAS, we attributed the signal around -18 ppm to 23Na in the bulk of the nanoparticles and the signal around -9 ppm to surface or/and sites near defects, featuring higher fluctuations in the electric field gradient (EFG). The 23Na 3Q-MAS spectra provide evidence for two (and sometimes three) distinct Na sites in α-NaYF4 with similar quadrupole coupling but slightly different chemical shifts. The 19F SE-MAS spectra show a broad peak around -75 ppm with a small shoulder around -120 ppm corresponding to only ≈1% of the signal. The peak around -75 ppm is attributed to the stoichiometric NaYF4 composition, and its broadening is attributed to a distribution of Na- and Y-rich environments. The minor shoulder around -120 ppm is associated with the F-deficient NaYF4 structure. The 19F spin-spin relaxation time indicates some degree of mobility of the fluorine atoms, possibly due to the presence of F vacancies triggering hopping-like ion motion. The signal related to the F-deficient structure is greatly enhanced for the smallest nanoparticles (φ = 4 nm), i.e., along with the increase of 23Na surface effects and defects. Therefore, we correlate several NMR techniques to provide a fundamental structural view for nanoparticles used as upconversion host systems with prominent technological applications. Particularly for α-NaYF4, significant surface effects and defects must be expected for nanoparticles with dimensions in the order of few nanometers (φ ≲ 7 nm).Fil: de Queiroz, Thiago B.. Universidad Federal do Abc; BrasilFil: Cabrera Baez, Michael. Universidade Federal de Pernambuco; BrasilFil: Menegasso, Paulo. Universidade Estadual de Campinas; BrasilFil: Martínez, Eduardo David. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Unidad Ejecutora Instituto de Nanociencia y Nanotecnología. Unidad Ejecutora Instituto de Nanociencia y Nanotecnología - Nodo Bariloche | Comisión Nacional de Energía Atómica. Unidad Ejecutora Instituto de Nanociencia y Nanotecnología. Unidad Ejecutora Instituto de Nanociencia y Nanotecnología - Nodo Bariloche; ArgentinaFil: García Flores, Ali F.. Universidade Estadual de Campinas; BrasilFil: Rettori, Carlos. Universidad Federal do Abc; BrasilFil: Urbano, Ricardo R.. Universidade Estadual de Campinas; Brasi

Conduction electron spin resonance in AlB2

ABSTRACT: This work reports on electron spin resonance experiments in oriented single crystals of the hexagonal AlB2 diboride compound (P6/mmm, D16h structure) which display conduction electron spin resonance. The X-band electron spin resonance spectra showed a metallic Dysonian resonance with g-value and intensity independent of temperature. The thermal broadening of the anisotropic electron spin resonance linewidth 1H tracks the T-dependence of the electrical resistivity below T ' 100 K. These results confirm the observation of a conduction electron spin resonance in AlB2 and are discussed in comparison with other boride compounds. Based on our main findings for AlB2 and the calculated electronic structure of similar layered honeycomb-like structures, we conclude that any array of covalent B–B layers potentially results in a conduction electron spin resonance signal. This observation may shed new light on the nature of the non-trivial conduction electron spin resonance-like signals of complex f-electron systems such as β-YbAlB4. Keywords: AlB2, Conduction electron, Dysonian resonance, Spin resonance

Synthesis, characterization, and incorporation of upconverting nanoparticles into a dental adhesive

The purpose of this study was to describe the synthesis, characterization, and functionalization of b-NaYF4:30%Yb/0.5%Tm upconverting nanocrystals for use as nanofillers in a dental adhesive and microscopically evaluate the interface between the particles and a commercial adhesive. The upconverting nanoparticles were synthesized and purified by thermal decomposition, and their chemical composition determined by energy dispersive X-Ray spectroscopy. The crystalline structure was characterized using X-Ray diffraction and morphology and size were observed with scanning and transmission electron microscopy. Upconverting emission was evaluated by spectrophotometry irradiating the particles with a 975 nm diode laser. Particles were functionalized with polyacrylic acid and the success was confirmed by measurement of Zeta Potential and transmission electron microscopy. The results of X-ray diffraction found a pure hexagonal phase crystalline pattern. Scanning electron microscopy showed uniform dispersion of hexagonal-shaped particles of approximately 150 nm. Upconversion emission was observed in 344 nm, 361 nm, 450 nm, 474nm, 646 nm, 803 nm. Functionalization success was confirmed by formation of a stable aqueous colloid with a Zeta potential of -29.5mV and the absence of voids in the particle-adhesive interface on the transmission electron microscopy images. The reported synthesis and functionalization process produced upconverting nanoparticles emitting photons within the blue spectral region (450 nm and 474 nm).Fil: Rocha Pacheco, Rafael. University Of Detroit Mercy; Estados UnidosFil: Garcia Flores, Ali Francisco. Universidad Federal do Abc; BrasilFil: Soto Montero, Jorge Rodrigo. Universidad de Costa Rica; Costa RicaFil: Lesseux, Guilherme Gorgen. Universidade Estadual de Campinas; BrasilFil: Rocha Acosta Lancelotti, Ailla Carla. Universidade Estadual de Campinas; BrasilFil: Martínez, Eduardo David. Universidade Estadual de Campinas; Brasil. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Unidad Ejecutora Instituto de Nanociencia y Nanotecnología. Unidad Ejecutora Instituto de Nanociencia y Nanotecnología - Nodo Bariloche | Comisión Nacional de Energía Atómica. Unidad Ejecutora Instituto de Nanociencia y Nanotecnología. Unidad Ejecutora Instituto de Nanociencia y Nanotecnología - Nodo Bariloche; ArgentinaFil: Rettori, Carlos. Universidad de Costa Rica; Costa RicaFil: Rodrigues Urbano, Ricardo. Universidade Estadual de Campinas; BrasilFil: Rueggeberg, Frederick Allen. No especifíca;Fil: Giannini, Marcelo. Universidade Estadual de Campinas; Brasi

Construcción de un espectrómero superheterodino en banda X para resonancia paramagnética electrónica y su posterior aplicación al estudio de los mecanismos de relajación espin-red, a temperaturas ambiente y del helio líquido sobre los cristales paramagnéticas Mn2+:OMg y Gd3+:F2Ca, mediante experimentos de tensiones uniaxiales y relajación con microondas pulsadas

En síntesis, los trabajos llevados a ocho han dudo lugar a la construcción y puesta en funcionamiento do los medios por los cuales es posible realizar experimentos tendientes a obtener una mejor comprensión de los fenómenos de interacción entre el sistema de espinas, correspondientes a los electrones no apareados de ciertos tipos de iones, y los átomos que componen la red cristalina donde se encuentra ubicado dicho ion. Los experimetos realizados utilizan la técnica de Resonancia […] Electrónica (RPE).- Con éste motivo, la primera etapa del trabajo consistió en la construcción de un espectrómetro con dotección superheterodina, trabajando a banda X y una frecuencia intermedia (FI) do 60 MHs, que permita la obtención del espetro de absorción o dispersión entre niveles Zooman […] de elementos o compuestos que posean uno o varios electrones no no apareados. Este espectrómetro de alta sensibilidad , además de ser utilizado para los experimentos aqui realizados, puede fácilmente ser adaptado y empleado en otros tipos de estudios tales como radicales libres, resonancia ciclotrónica, experimentos de doble resonancia (RNDOR […]) etc.- Los detalles de construcción son tratados en el capítulo uno.- Los experimentos realizados con el objeto do obtener mayor información acerca de la interacción entro un sistema de espinas y la red cristalina, consisten por un lado en la observación del corrimiento de la línea de absorción de estructura fina de un ion paramagnético cuando el cristal, donde está ubicado el ión, es deformado por una presión externa y por otro en la observación de la recuperación de la línea de absorción después de haber sido saturada. El primer tipo de experimento es tratado en el capítulo dos con el título Tensiones Uniaxiales.- Allí podrán verse los detalles de la construcción y realización de la experiencia, asi como el resultado de la medición del coeficiente de in-red […] de segundo orden c3g(²) para el sistema Mn²+, Omg a temperatura ambiente.- El segundo tipo de experimento es tratado en el capítulo tres con el título Relajación […] in-Red.- Alli podrán observarse los detalles de construcción y realización de la experiencia, así cono los resultados de la medición del tiempo de relajación […] in-red T1, dado por el tiempo de recuperación de una línea de absorción previamente saturada, del Cdᶟ+ ubicado en lugares con simetría tetragonal del F2Ca a temperatura del helio liquido.-Fil:Rettori, Carlos. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina

Thermoplasmonic enhancement of upconversion in small-size doped NaGd(Y)F-4 nanoparticles coupled to gold nanostars

CAPES - COORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL E NÍVEL SUPERIORCNPQ - CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOFAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOPlasmon enhancement of luminescence is a common strategy to boost the efficiency of both fluorescence and upconversion via the augmented local electromagnetic field. However, the local heating produced when exciting the plasmon resonance of metallic nanoparticles is often overlooked. As higher temperatures are usually detrimental for radiative processes, only the electromagnetic contribution is exploited for enhancement. We show here that for small size (<20 nm) rare-earth doped -NaGd(Y)F-4 upconversion nanoparticles (UCNPs), the photothermal properties of gold nanostars (AuNSs) can be used to enhance the total emission intensity. On the contrary, for UCNPs of larger size, the thermoplasmonic effect is adverse for the emissivity. Therefore, we developed a novel strategy to enhance the emission intensity by combining the thermoplasmonic effect on AuNSs with the size-dependent thermal properties of UCNPs. Furthermore, by following the integrated intensity ratio between the emission lines of Er3+, H-2(11/2) I-4(15/2) and S-4(3/2) I-4(15/2), a direct correlation between the local temperature and the emission intensity could be established. Optical thermometry measurements show that the thermoplasmonic effect in AuNSs, with a plasmon absorption band close to the excitation wavelength, can produce an increment of the local temperature of more than 100 degrees C when exposed to 976 nm continuous-wave laser light at 50 W cm(-2) of power density. The results provided here are relevant for the design and implementation of plasmon-enhanced luminescent devices, upconversion solar-cells, bioprobes and also for hyperthermia.10301468714696CAPES - COORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL E NÍVEL SUPERIORCNPQ - CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOFAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOCAPES - COORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL E NÍVEL SUPERIORCNPQ - CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOFAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOsem informaçãosem informação2011/19924-22012/04870-72012/05903-62015/21290-22015/21289-42015/23882-

Hyperspectral imaging thermometry assisted by upconverting nanoparticles: Experimental artifacts and accuracy

We combined the sensing capabilities of Er3+-doped upconverting nanoparticles (UCNPs) with hyperspectral microscopy to construct thermal images on thermally active nanostructures. Here, we studied the heat dissipation of a percolating network of silver nanowires under controlled electric current flow. We quantified the electrothermal action by analyzing the hyperspectral data and constructing 2D maps for the emission intensity, the signal-to-noise ratio, and the thermometric parameter. By studying selected clusters in the network, we concluded that the temperature is quite uniform across the film without any significant thermal gradients. Nonetheless, the thermal evolution was clearly sensed by the UCNPs when the heat dissipation due to the Joule effect was turned on and off, validating the use of this method for studying slow-dynamic thermal processes. Finally, we discuss the accuracy of the thermal readings and the systematic limitations of the proposed method.publishe

Electrochromic switch devices mixing small- and large-sized upconverting nanocrystals

CAPES - COORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL E NÍVEL SUPERIORFAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOMCTIC - MINISTÉRIO DA CIÊNCIA, TECNOLOGIA, INOVAÇÕES E COMUNICAÇÕESThe hasty progress in smart, portable, flexible, and transparent integrated electronics and optoelectronics is currently one of the driving forces in nanoscience and nanotechnology. A promising approach is the combination of transparent conducting electrode materials (e.g., silver nanowires, AgNWs) and upconverting nanoparticles (UCNPs). Here, electrochromic devices based on transparent nanocomposite films of poly(methyl methacrylate) and AgNWs covered by UCNPs of different sizes and compositions are developed. By combining the electrical control of the heat dissipation in AgNW networks with size-dependent thermal properties of UCNPs, tunable electrochromic transparent devices covering a broad range of the chromatic diagrams are fabricated. As illustrative examples, devices mixing large-sized (>70 nm) beta-NaYF4:Yb,Ln and small-sized ( I-4(15/2) emission lines, while externally controlling the current flow in the AgNW network. Moreover, by defining a new thermometric parameter involving the intensity ratio of transitions of large- and small-sized UCNPs, a relative thermal sensitivity of 5.88% K-1 (at 339 K) is obtained, a sixfold improvement over the values reported so far.298112CAPES - COORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL E NÍVEL SUPERIORFAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOMCTIC - MINISTÉRIO DA CIÊNCIA, TECNOLOGIA, INOVAÇÕES E COMUNICAÇÕESCAPES - COORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL E NÍVEL SUPERIORFAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOMCTIC - MINISTÉRIO DA CIÊNCIA, TECNOLOGIA, INOVAÇÕES E COMUNICAÇÕES0012011/19924-2; 2012/04870-7; 2012/05903-6; 2015/21289-4; 2015/21290-2; 2015/23882-4FCT UID/CTM/50011/2013; PTDC/CTM-NAN/4647/2014; POCI-01-0145-FEDER-016687Authors are grateful to Prof. G. J. A. A. Soler-Illia for his help in establishing this international collaboration and to Prof. Daniel Jaque for helpful discussions. This study was financed in part by the Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior-Brazil (CAPES)-Finance Code 001 and FundacAo de Amparo a Pesquisa do Estado de SAo Paulo (FAPESP) under Grant Nos. 2011/19924-2, 2012/04870-7, 2012/05903-6, 2015/21290-2, and 2015/21289-4. This work was partially developed in the scope of the project CICECO-Aveiro Institute of Materials (Ref. FCT UID/CTM/50011/2013), financed by Portuguese funds through the FundacAo para a Ciencia e a Tecnologia/Ministerio da EducacAo e Ciencia (FCT/MEC) and when applicable cofinanced by FEDER under the PT2020 Partnership Agreement. The financial support from FCT (PTDC/CTM-NAN/4647/2014 and POCI-01-0145-FEDER-016687) is also acknowledged and the project has received funding from the European Union's Horizon 2020 FET Open programme under Grant No. 801305. E.D.M. acknowledges the postdoctoral FAPESP fellowship 2015/23882-4 and BEPE 2018/12489-8. C.D.S.B. acknowledges the grant financed by the SusPhotoSolutions project CENTRO-01-0145-FEDER-000005. The SEM, TEM, and AFM data were acquired at LNNano, Centro Nacional de Pesquisa em Energia e Materiais (CNPEM) in Campinas, SP, Brazil