Two-photon luminescence thermometry: towards 3D high-resolution thermal imaging of waveguides

We report on the use of the Erbium-based luminescence thermometry to realize high resolution, three dimensional thermal imaging of optical waveguides. Proof of concept is demonstrated in a 980-nm laser pumped ultrafast laser inscribed waveguide in Er:Yb phosphate glass. Multi-photon microscopy images revealed the existence of well confined intra-waveguide temperature increments as large as 200 °C for moderate 980-nm pump powers of 120 mW. Numerical simulations and experimental data reveal that thermal loading can be substantially reduced if pump events are separated more than the characteristic thermal time that for the waveguides investigated is in the ms time scale.Ministerio de Economía y Competitividad of Spain (MINECO) (FIS2013-44174-P, MAT2013-47395-C4-1-R); National Natural Science Foundation of China (NSFC) (11274203)

Spectroscopic characterization of Er3+-doped CaF2 nanoparticles: Luminescence concentration quenching, radiation trapping and transition probabilities

Er3+-doped CaF2 nanoparticles (NPs) with variable dopant concentration were synthesized by a direct precipitation method. X-Ray Powder Diffraction, SEM and TEM were used to analize the crystalline structure and morphology. The spectroscopic characterization, as function of the Er3+ content, has been performed under CW and pulsed excitation. Under steady state conditions, it has been found that the intensity of the main emission bands is affected by luminescence quenching processes. The population dynamics, recorded under pulsed excitation, confirms not only the existence of quenching processes but also the occurrence of radiation trapping. The intrinsic transition probabilities of the main Er3+ emitting manifolds, in absence of quenching and radiation trapping, have been estimated through a procedure commonly used in bulk doped materials. A modified Judd-Ofelt analysis has been performed to determine the radiative transition probabilities, radiative lifetimes and branching ratios of the Er3+ levels. Finally, an estimation of the gap law in these NPs is givenThis work has been partially supported by Ministerio de Ciencia e Innovación (Spain) under project COLUMNAS (PID2019–110632RB-I00

3D Optical Coherence Thermometry Using Polymeric Nanogels

In nanothermometry, the use of nanoparticles as thermal probes enables remote and minimally invasive sensing. In the biomedical context, nanothermometry has emerged as a powerful tool where traditional approaches, like infrared thermal sensing and contact thermometers, fall short. Despite the strides of this technology in preclinical settings, nanothermometry is not mature enough to be translated to the bedside. This is due to two major hurdles: the inability to perform 3D thermal imaging and the requirement for tools that are readily available in the clinics. This work simultaneously overcomes both limitations by proposing the technology of optical coherence thermometry (OCTh). This is achieved by combining thermoresponsive polymeric nanogels and optical coherence tomography (OCT)—a 3D imaging technology routinely used in clinical practice. The volume phase transition of the thermoresponsive nanogels causes marked changes in their refractive index, making them temperature-sensitive OCT contrast agents. The ability of OCTh to provide 3D thermal images is demonstrated in tissue phantoms subjected to photothermal processes, and its reliability is corroborated by comparing experimental results with numerical simulations. The results included in this work set credible foundations for the implementation of nanothermometry in the form of OCTh in clinical practiceThis work was financed by the Spanish Ministerio de Innovación y Ciencia under project NANONERV PID2019-106211RB-I00, NANOGRANZ PID2021-123318OB-I00, PID2020-118878RB-I00, RYC2021-032913-I, and TED2021-132317-I00B and under project COLUMNAS (PID2019- 110632RB-I00), by the Instituto de Salud Carlos III (PI19/00565), by the Comunidad Autónoma de Madrid (S2022/BMD-7403 RENIM-CM and SI3/PJI/2021-00211) and co-financed by the European structural and investment fund. Additional funding was provided by COST action CA17140, supported by COST (European Cooperation in Science and Technology) and the Fundación para la Investigación Biomédica del Hospital Universitario Ramón y Cajal (IMP21_A4 (2021/0427)

Early in vivo detection of denervation-induced atrophy by luminescence transient nanothermometry

Denervation induces skeletal muscle atrophy due to the loss of control and feedback with the nervous system. Unfortunately, muscle atrophy only becomes evident days after the denervation event when it could be irreversible. Alternative diagnosis tools for early detection of denervation-induced muscle atrophy are, thus, required. In this work, we demonstrate how the combination of transient thermometry, a technique already used for early diagnosis of tumors, and infrared-emitting nanothermometers makes possible the in vivo detection of the onset of muscle atrophy at short (<1 day) times after a denervation event. The physiological reasons behind these experimental results have been explored by performing three dimensional numerical simulations based on the Pennes' bioheat equation. It is concluded that the alterations in muscle thermal dynamics at the onset of muscle atrophy are consequence of the skin perfusion increment caused by the alteration of peripheral nervous autonomous system. This work demonstrates the potential of infrared luminescence thermometry for early detection of diseases of the nervous system opening the venue toward the development of new diagnosis toolsComunidad de Madrid, Grant/Award Number: S2017/BMD-3867 RENIM-CM; COST action CA17140 (Nano2Clinic); European Structural and Investment Fund and the Ministerio de Economía y Competitividad-MINECO, Grant/Award Number: PID2019-106211RB-I00; Juan de la Cierva scholarship, Grant/Award Number: IJC2020-045229-

2D Cu(I)‑I Coordination Polymer with Smart Optoelectronic Properties and Photocatalytic Activity as a Versatile Multifunctional Material

This work presents two isostructural Cu(I)-I 2-fluoropyrazine (Fpyz) luminescent and semiconducting 2D coordination polymers (CPs). Hydrothermal synthesis allows the growth of P-1 space group single crystals, whereas solvent-free synthesis produces polycrystals. Via recrystallization in acetonitrile, P21 space group single crystals are obtained. Both show a reversible luminescent response to temperature and pressure. Structure determination by single-crystal X-ray diffraction at 200 and 100 K allows us to understand their response as a function of temperature. Applying hydrostatic/uniaxial pressure or grinding also generates significant variations in their emission. The high structural flexibility of the Cu(I)-I chain is significantly linked to the corresponding alterations in structure. Remarkably, pressure can increase the conductivity by up to 3 orders of magnitude. Variations in resistivity are consistent with changes in the band gap energy. The experimental results are in agreement with the DFT calculations. These properties may allow the use of these CPs as optical pressure or temperature sensors. In addition, their behavior as a heterogeneous photocatalyst of persistent organic dyes has also been investigatedThanks to Micro and Nanotechnology Institute CNM-CSIC for SEM images. Thanks to the SCXRD laboratory of the Interdepartmental Research Service and to Servicios Generales de Apoyo a la Investigación (SEGAI) at La Laguna University. This work has been supported by MCINN/AEI/ 10.13039/ 5011000011033 under the National Program of Sciences and Technological Materials, PID2019-108028GB-C22, PID2019- 106383GB-C41/C44, and TED2021-131132B-C22. Thanks to Gobierno d e Canarias and EU-FEDER (grant: ProID2020010067). This study forms part of the Advanced Materials program and was supported by MCIN with funding from European Union Next Generation EU (PRTR-C17.I1) and by Generalitat Valenciana (grant MFA/2022/007 and PROMETEO CIPROM/2021/075-GREENMAT). A.L. (R.T.) and D.E. thank the Generalitat Valenciana for the Ph.D. (Postdoctoral) Fellowship No. GRISOLIAP/2019/025 (CIAPOS/2021/20). J.C.G. and R. W. acknowledge the support from the Spanish Ministry of Science and Innovation (RTI2018-097508-B-I00, PID2021-128313OB-I00, TED2021- 131018B-C22) and the Regional Government of Madrid through projects NMAT2D-CM (S2018/NMT-4511). J.C.G. acknowledges support from the Regional Government of Madrid through “Proyectos Sinérgicos de I + D” (grant Y2018/NMT-5028 FULMATEN-CM) and NANOCOV-CM (REACT-UE). IMDEA Nanociencia acknowledges support from the Severo Ochoa Programme for Centres of Excellence in R&D (MINECO, grant CEX2020-001039-S