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Research interests

Confocal microscopy, semiconductor nanowires.

Publications

1. Near-infrared and short-wavelength infrared photodiodes based on dye-perovskite composites,
   QQ Lin, ZP Wang, M Young, JB Patel, RL Milot, LM Maestro, RR Lunt, HJ Snaith, MB Johnston, LM Herz
   Adv. Funct. Mater., 27:1702485 (2017) [ abstract | pdf | doi:10.1002/adfm.201702485 ]
   Organohalide perovskites have emerged as promising light-sensing materials because of their superior optoelectronic properties and low-cost processing methods. Recently, perovskite-based photodetectors have successfully been demonstrated as both broadband and narrowband varieties. However, the photodetection bandwidth in perovskite-based photodetectors has so far been limited to the near-infrared regime owing to the relatively wide band gap of hybrid organohalide perovskites. In particular, short-wavelength infrared photodiodes operating beyond 1 mu m have not yet been realized with organohalide perovskites. In this study, narrow band gap organic dyes are combined with hybrid perovskites to form composite films as active photoresponsive layers. Tuning the dye loading allows for optimization of the spectral response characteristics and excellent charge-carrier mobilities near 11 cm(2) V-1 s(-1), suggesting that these composites combine the light-absorbing properties or IR dyes with the outstanding charge-extraction characteristics of the perovskite. This study demonstrates the first perovskite photodiodes with deep near-infrared and short-wavelength infrared response that extends as far as 1.6 mu m. All devices are solution-processed and exhibit relatively high responsivity, low dark current, and fast response at room temperature, making this approach highly attractive for next-generation light-detection techniques.
2. Dielectric anomalous response of water at 60 degrees c,
   QQ Lin, ZP Wang, M Young, JB Patel, RL Milot, LM Maestro, RR Lunt, HJ Snaith, MB Johnston, LM Herz, E Camarillo, LM Maestro, JA Gonzalo, C Arago, M Marques, D Jaque, G Lifante, JG Sole, K Santacruz-gomez, RC Carrillo-torres, F Jaque
   Philos. Mag., 95:683-690 (2015) [ abstract | pdf | doi:10.1080/14786435.2014.1000419 ]
   Recently, the paraelectric response of water was investigated in the range 0-100 degrees C. It showed an almost perfect Curie-Weiss behaviour up to 60 degrees C, but a slight change in slope of 1/epsilon(d) versus T at 60 degrees C was overlooked. In this work, we report optical extinction measurements on metallic (gold and silver) nanoparticles dispersed in water, annealed at various temperatures in the range from 20 to 90 degrees C. An anomalous response at 60 degrees C is clearly detectable, which we associate to a subtle structural transformation in the water molecules at that temperature. This water anomaly is also manifested by means of a blue shift in the longitudinal surface plasmon resonance of the metallic nanoparticles for the solutions annealed at temperatures higher than about 60 degrees C. A reanalysis of 1/epsilon(d) (T) for water in the whole temperature range leads us to conclude that the water molecule undergoes a subtle transformation from a low temperature (0-60 degrees C) configuration with a dipole moment mu(1)=2.18 D (close to the molecular dipole moment of ice) to a high temperature (60-100 degrees C) configuration with mu(2)=1.87 D (identical to the molecular dipole moment in water vapour).
3. Quantum-dot based nanothermometry in optical plasmonic recording media,
   LM Maestro, QM Zhang, XP Li, D Jaque, M Gu
   Appl. Phys. Lett., 105:181110 (2014) [ abstract | pdf | doi:10.1063/1.4901258 ]
   We report on the direct experimental determination of the temperature increment caused by laser irradiation in a optical recording media constituted by a polymeric film in which gold nanorods have been incorporated. The incorporation of CdSe quantum dots in the recording media allowed for single beam thermal reading of the on-focus temperature from a simple analysis of the two-photon excited fluorescence of quantum dots. Experimental results have been compared with numerical simulations revealing an excellent agreement and opening a promising avenue for further understanding and optimization of optical writing processes and media. (C) 2014 AIP Publishing LLC.
4. Fluorescent nanothermometers for intracellular thermal sensing,
   D Jaque, EM Rodriguez, LM Maestro, P Haro-gonzalez, JG Sole
   Nanomedicine, 9:1047- (2014) [ abstract | pdf | doi:10.2217/NNM.14.59 ]
   The importance of high-resolution intracellular thermal sensing and imaging in the field of modern biomedicine has boosted the development of novel nanosized fluorescent systems (fluorescent nanothermometers) as the next generation of probes for intracellular thermal sensing and imaging. This thermal mapping requires fluorescent nanothermometers with good biocompatibility and high thermal sensitivity in order to obtain submicrometric and subdegree spatial and thermal resolutions, respectively. This review describes the different nanosized systems used up to now for intracellular thermal sensing and imaging. We also include the later advances in molecular systems based on fluorescent proteins for thermal mapping. A critical overview of the state of the art and the future perspective is also included.
5. Quantum dot thermometry evaluation of geometry dependent heating efficiency in gold nanoparticles,
   LM Maestro, P Haro-gonzalez, A Sanchez-iglesias, LM Liz-marzan, JG Sole, D Jaque
   Langmuir, 30:1650-1658 (2014) [ abstract | pdf | doi:10.1021/la403435v ]
   Quantum dot based thermometry, in combination with double beam confocal microscopy, was used to investigate the absorption/heating efficiency of gold nanoparticles with different morphologies (nanorods, nanocages, nanoshells, and nanostars), all of them with an intense localized surface plasmon resonance within the first biological window, at around 808 nm. The heating efficiency was found to be strongly dependent on the geometry of the nanostructure, with the largest values found for gold nanorods and long-edge gold nanostars, both of them with heating efficiencies dose to 100%. Gold nanorods and nanocages were found to have the largest absorption cross section per unit mass among all the studied geometries, emerging as optimum photothermal agents with minimum metal loading for biosystems.
6. Gold nanorods for optimized photothermal therapy: the influence of irradiating in the first and second biological windows,
   LM Maestro, E Camarillo, JA Sanchez-Gil, R Rodriguez-oliveros, J Ramiro-bargueno, AJ Caamano, F Jaque, JG Sole, D Jaque
   RSC Adv., 4:54122-54129 (2014) [ abstract | pdf | doi:10.1039/c4ra08956a ]
   The light-to-heat conversion efficiency of gold nanorods (GNRs) with surface plasmon resonances in the first (700-950 nm) and second (1000-1350 nm) biological windows has been studied by Quantum Dot based Fluorescence Nanothermometry. It has been found that red-shifting the GNR longitudinal surface plasmon resonance wavelength (lambda(SPR)) from the first to the second biological window is accompanied by a remarkable (close to 40%) reduction in their heating efficiency. Based on numerical simulations, we have concluded that this lower heating efficiency is caused by a reduction in the absorption efficiency (ratio between absorption and extinction cross sections). Thermal stability and ex vivo experiments have corroborated that GNRs with lSPR at around 800 nm seem to be especially suitable for efficient photothermal therapies with minimum collateral effects.
7. Response to ,
   LM Maestro, C Jacinto, UR Silva, F Vetrone, JA Capobianco, D Jaque, JG Sole
   Small, 9:3198-3200 (2013) [ abstract | pdf | doi:10.1002/smll.201300569 ]
8. Fluorescent nanothermometers provide controlled plasmonic-mediated intracellular hyperthermia,
   LM Maestro, P Haro-gonzalez, F Sanz-rodriguez, A Juarranz, JG Sole, D Jaque
   Nanomedicine, 8:379-388 (2013) [ abstract | pdf | doi:10.2217/NNM.12.122 ]
   Aim: This article demonstrates how controlled hyperthermia at the cellular level can be achieved. Materials & methods: The method is based on the simultaneous intracellular incorporation of fluorescence nanothermometers (CdSe quantum dots) and metallic nanoheaters (gold nanorods). Results: Real-time spectral analysis of the quantum dot emission provides a detailed feedback about the intracellular thermal loading caused by gold nanorods excited at the plasmon frequency. Based on this approach, thermal dosimetry is assessed in such a way that the infrared laser (heating) power required to achieve catastrophic intracellular temperature increments in cancer cells is identified. Conclusions: This pure optical method emerges as a new and promising guide for the development of infrared hyperthermia therapies with minimal invasiveness. Original submitted 6 March 2012; Revised submitted 3 July 2012; Published online 2 December 2012
9. Fluorescent nano-particles for multi-photon thermal sensing,
   D Jaque, LM Maestro, E Escudero, EM Rodriguez, JA Capobianco, F Vetrone, F Sanz-rodriguez, C Jacinto, U Rocha, JG Sole
   J. Lumines., 133:249-253 (2013) [ abstract | pdf | doi:10.1016/j.jlumin.2011.12.022 ]
   In this work we report on the ability of Er/Yb co-doped NaYF4 nano-crystals and CdTe Quantum Dots as two-photon excited fluorescent nano-thermometers. The basic physical phenomena causing the thermal sensitivity of the two-photon excited emission bands have been discussed and the maximum thermal resolution achievable in each case has been estimated. The practical application of both systems for thermal sensing at the micro-scale in biological systems is demonstrated. In particular, they have been used to evaluate the thermal loading induced by tightly focused laser beams in both living cells and fluids. (c) 2011 Elsevier B.V. All rights reserved.
10. Heating efficiency of multi-walled carbon nanotubes in the first and second biological windows,
    LM Maestro, P Haro-gonzalez, J Ramiro, AJ Caamano, E Carrasco, A Juarranz, F Sanz-rodriguez, JG Sole, D Jaque
    Nanoscale, 5:7882-7889 (2013) [ abstract | pdf | doi:10.1039/c3nr01398g ]
    Quantum dot based-thermometry, in combination with double beam confocal microscopy and infrared thermal imaging, has been used to investigate the heating efficiency of multi-walled carbon nanotubes (MWCNTs) under optical excitation within the first (808 nm) and second (1090 nm) biological windows as well as in the spectral region separating them (980 nm). It has been found that for the three excitation wavelengths the heating efficiency of MWCNTs (10 nm in diameter and 1.5 mu m in length) is close to 50%. Despite this "flat" heating efficiency, we have found that the excitation wavelength is, indeed, critical during in vivo experiments due to the spectral dependence of both tissue absorption and scattering coefficients. It has been concluded that efficiency and selectivity of in vivo photothermal treatments based on MWCNTs are simultaneously optimized when laser irradiation lies within the first or second biological window.
11. Optical trapping of nayf4:er3+,yb3+ upconverting fluorescent nanoparticles,
    P Haro-gonzalez, LM Maestro, EM Rodriguez, R Naccache, JA Capobianco, K Dholakia, JG Sole, D Jaque
    Nanoscale, 5:12192- (2013) [ abstract | pdf | doi:10.1039/c3nr03644h ]
    We report on the first experimental observation of stable optical trapping of dielectric NaYF4:Er3+,Yb3+ upconverting fluorescent nanoparticles (similar to 26 nm in diameter) using a continuous wave 980 nm single-beam laser. The laser serves both to optically trap and to excite visible luminescence from the nanoparticles. Sequential loading of individual nanoparticles into the trap is observed from the analysis of the emitted luminescence. We demonstrate that the trapping strength and the number of individual nanoparticles trapped are dictated by both the laser power and nanoparticle density. The possible contribution of thermal effects has been investigated by performing trapping experiment in both heavy water and into distilled water. For the case of heavy water, thermal gradients are negligible and optical forces dominate the trap loading behaviour. The results provide a promising path towards real three dimensional manipulation of single NaYF4:Er3+,Yb3+ nanoparticles for precise fluorescence sensing in biophotonics experiments.
12. Evaluation of rare earth doped silica sub-micrometric spheres as optically controlled temperature sensors,
    P Haro-gonzalez, LM Maestro, M Trevisani, S Polizzi, D Jaque, JG Sole, M Bettinelli
    J. Appl. Phys., 112:054702 (2012) [ abstract | pdf | doi:10.1063/1.4751349 ]
    We report on the evaluation of rare earth (Er3+, Eu3+, and Tb3+ ions) SiO2 sub-micrometric spheres as potential optically controllable temperature sensors. Details about fabrication, optical manipulation and spectroscopic characterization of the sub-micrometric spheres are presented. The fluorescence properties of the micros-spheres in the biological range (25-60 degrees C) have been systematically investigated. From this systematic study, the thermal resolution potentially achieved in each case has been determined and compared to previous works. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4751349]
13. Absorption efficiency of gold nanorods determined by quantum dot fluorescence thermometry,
    LM Maestro, P Haro-gonzalez, JG Coello, D Jaque
    Appl. Phys. Lett., 100:201110 (2012) [ abstract | pdf | doi:10.1063/1.4718605 ]
    In this work quantum dot fluorescence thermometry, in combination with double-beam confocal microscopy, has been applied to determine the thermal loading of gold nanorods when subjected to an optical excitation at the longitudinal surface plasmon resonance. The absorbing/heating efficiency of low (approximate to 3) aspect ratio gold nanorods has been experimentally determined to be close to 100%, in excellent agreement with theoretical simulations of the extinction, absorption, and scattering spectra based on the discrete dipole approximation. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4718605]
14. Optimum quantum dot size for highly efficient fluorescence bioimaging,
    LM Maestro, C Jacinto, U Rocha, F Sanz-rodriguez, A Juarranz, JG Sole, D Jaque
    J. Appl. Phys., 111:023513 (2012) [ abstract | pdf | doi:10.1063/1.3676251 ]
    Semiconductor quantum dots of few nanometers have demonstrated a great potential for bioimaging. The size determines the emitted color, but it is also expected to play an important role in the image brightness. In this work, the size dependence of the fluorescence quantum yield of the highly thermal sensitive CdTe quantum dots has been systematically investigated by thermal lens spectroscopy. It has been found that an optimum quantum yield is reached for 3.8-nm quantum dots. The presence of this optimum size has been corroborated in both one-photon excited fluorescence experiments and two-photon fluorescence microscopy of dot-incubated cancer cells. Combination of quantum yield and fluorescence decay time measurements supports that the existence of this optimum size emerges from the interplay between the frequency-dependent radiative emission rate and the size-dependent coupling strength between bulk excitons and surface trapping states. (C) 2012 American Institute of Physics. [doi:10.1063/1.3676251]
15. Deep tissue bio-imaging using two-photon excited cdte fluorescent quantum dots working within the biological window,
    LM Maestro, JE Ramirez-hernandez, N Bogdan, JA Capobianco, F Vetrone, JG Sole, D Jaque
    Nanoscale, 4:298-302 (2012) [ abstract | pdf | doi:10.1039/c1nr11285f ]
    A new approach to deep tissue imaging is presented based on 8 nm CdTe semiconductor quantum dots (QDs). The characteristic 800 nm emission was found to be efficiently excited via two-photon absorption of 900 nm photons. The fact that both excitation and emission wavelengths lie within the "biological window" allows for high resolution fluorescence imaging at depths close to 2 mm. These penetration depths have been used to obtain the first deep tissue multiphoton excited fluorescence image based on CdTe-QDs. Due to the large thermal sensitivity of CdTe-QDs, one may envisage, in the near future, their use in high resolution deep-tissue thermal imaging.
16. Cdte quantum dots as nanothermometers: towards highly sensitive thermal imaging,
    LM Maestro, C Jacinto, UR Silva, F Vetrone, JA Capobianco, D Jaque, JG Sole
    Small, 7:1774-1778 (2011) [ abstract | pdf | doi:10.1002/smll.201002377 ]
17. Nanoparticles for highly efficient multiphoton fluorescence bioimaging,
    LM Maestro, EM Rodriguez, F Vetrone, R Naccache, HL Ramirez, D Jaque, JA Capobianco, JG Sole
    Opt. Express, 18:23544- (2010) [ abstract | pdf | doi:10.1364/OE.18.023544 ]
    In this paper, we demonstrate for the first time that the new class of fluoride-based inorganic upconverting nanoparticles, NaYF4:Er3+, Yb3+, are the most efficient multiphoton excited fluorescent nanoparticles developed to date. The near-infrared-to-visible conversion efficiency of the aforementioned nanoparticles surpasses that of CdSe quantum dots and gold nanorods, which are the commercially available inorganic fluorescent nanoprobes presently used for multiphoton fluorescence bioimaging. The results presented here open new perspectives for the implementation of fluorescence tomography by multiphoton fluorescence imaging. (C) 2010 Optical Society of America
18. Temperature sensing using fluorescent nanothermometers,
    F Vetrone, R Naccache, A Zamarron, F Sanz-rodriguez, LM Maestro, EM Rodriguez, D Jaque, JG Sole, JA Capobianco
    ACS Nano, 4:3254-3258 (2010) [ abstract | pdf | doi:10.1021/nn100244a ]
    Acquiring the temperature of a single living cell is not a trivial task. In this paper, we devise a novel nanothermometer, capable of accurately determining the temperature of solutions as well as biological systems such as HeLa cancer cells. The nanothermometer is based on the temperature-sensitive fluorescence of NaYF(4):Er(3+),Yb(3+) nanoparticles, where the intensity ratio of the green fluorescence bands of the Er(3+) dopant ions ((2)H(11/2) -> (4)I(15/2) and (4)S(3/2) -> (4)I(15/2)) changes with temperature. The nanothermometers were first used to obtain thermal profiles created when heating a colloidal solution of NaYF(4):Er(3+),Yb(3+) nanoparticles in water using a pump-probe experiment. Following incubation of the nanoparticles with HeLa cervical cancer cells and their subsequent uptake, the fluorescent nanothermometers measured the internal temperature of the living cell from 25 degrees C to its thermally induced death at 45 degrees C.
19. Ultrafast laser inscription of bistable and reversible waveguides in strontium barium niobate crystals,
    D Jaque, ND Psaila, RR Thomson, F Chen, LM Maestro, A Rodenas, DT Reid, AK Kar
    Appl. Phys. Lett., 96:191104 (2010) [ abstract | pdf | doi:10.1063/1.3429584 ]
    We report the fabrication of buried optical channel waveguides in strontium barium niobate nonlinear ferroelectric crystals by direct ultrafast laser inscription. These waveguides are strongly polarized and can be reversibly switched on and off by changing the temperature of the crystal, a characteristic we attribute to the bistable enhancement of the electro-optic coefficients at the ferro to paraelectric phase transition. (C) 2010 American Institute of Physics. [doi:10.1063/1.3429584]
20. Anisotropic lattice changes in femtosecond laser inscribed nd3+:mgo:linbo3 optical waveguides,
    A Rodenas, LM Maestro, MO Ramirez, GA Torchia, L Roso, F Chen, D Jaque
    J. Appl. Phys., 106:013110 (2009) [ abstract | pdf | doi:10.1063/1.3168432 ]
    We report on the fabrication and microspectroscopy imaging of femtosecond laser written double-filament based Nd3+:MgO:LiNbO3 optical waveguides. The waveguiding high refractive-index regions are identified by blueshifts of the Nd3+ ion fluorescence lines with no deterioration in the fluorescence efficiency, whereas filamentary low-index regions are identified by both a Nd3+ line redshift and a fluorescence efficiency reduction. The lattice structural micromodifications at the origin of both waveguide formation and Nd3+ fluorescence changes have been investigated by means of confocal micro-Raman experiments. We have found that the direct laser written filaments are mainly constituted by a large density of defects, together with a marked axial compression perpendicular to the filaments (along the optical c-axis). Conversely, the high-index waveguiding regions are characterized by a pronounced anisotropic dilatation of the LiNbO3 lattice xy-planes.