New direction for broadening the luminescence emission of lanthanides in solids

Modelocked femtosecond lasers require of luminescent ions with large emission bandwidth and tunability. This requirement is difficult to fulfill with lanthanides due to the inner nature of the 4f orbital. The concept of «disordered single crystals» which  is based on multiple (isovalent or heterovalent) cationic substitutions on the same lattice site has gained attention to solve the problem but results are still limited. In our recent publication in Journal of Alloys and Compounds 961 (2023) 171092 (doi 10.1016/j.jallcom.2023.171092) we show that the random orientation of the Bi3+ non-bonded 6s2 lone pair induces a large band broadening of the Yb3+ emission in monoclinic KY1-x-yBixYby(WO4)2 single crystals. The  growth of these crystals and their laser capabilities are demonstrated within the activity of our THINLAS project.




New luminescence nanoprobes for thermometry at high temperature catalysis

Most common thermometric luminescent  nanoprobres contain alkaline and/or halogen ions which poisson currently used catalysts, for instance the well known NaYF4 host based compounds. Our IMPETUSS project (PID2021-128090OB-C21) aims the development of eficient luminescence nanoprobes compatible with standardly catalyzed reactions. In this direction we develloped alkaline and halogen-free β´Gd2(MoO4)2 nanoprobes doped with Yb3+, Er3+ and Tm3+. We defined three different ratiometric  channels to determine  temperature from 20 to 600ºC with optimised sensitivity. See Journal of Alloys and Compounds 913 (2022) 165180 doi 10.1016/j.jallcom.2022.165180.


Thermal gradients in tandem catalysis are monitored by lifetime luminescence thermometry

Our recent publication in Journal of Materials Chemistry A 2023, 11, 19854 (doi 10.1039/d3ta03654e) in collaboration with the Institute of Chemical Technology (UPV-CSIC) in Valencia (among others) adresses the problem found in Tandem Catalysis of having»spatially proximate but thermally distant» catalysts contained in a single reactor.  An elegant solution arose through the specific heating of the hot catalyst by magnetic susception. A thermal gradient of 50 ºC between the hot and cold catalysts was infered by  luminescence lifetime thermometry by using Eu3+-doped and Cr3+-doped nanoprobes. A probe of concept was demostrated by direct production of propene from ethene, via sequential olefin dimerization and metathesis reactions.

We welcome new incorporations to REALM

In February 2024 Dr. Xiumei Han incorporated to the REALM group as responsible of the Top Seeded Solution Crystal Growth laboratory.

Also in February 2024  Illán Calvo Llorente  incorporated to the REAL group  hired by THINLAS project.

We wish both of you all success during your stays.


REALM coordinates IMPETUSS Project PID2021-128090OB, funded by Spanish Ministry of Science and Innovation MICIN/AEI/10.13039/501100011033 and by ERDF A way of making Europe.

“Non-conventional solutions on luminescence-based high temperature thermometry for applications of industrial interest (IMPETUSS)” Project has been awarded for the period 01/09/2022 to 31/08/2025.

This project proposes new strategies for the design of contactless photoluminescence (PL) thermal probes spanning their operation range to temperatures well above 300 K. These probes will be based either on the PL of lanthanides (Ln) incorporated in inert refractory hosts or on that of carbon quantum dots (CQDs). In combination with remote reading techniques, the new developed thermal probes will enable the creation of bidimensional temperature maps, which may prevent device failures by allowing early detection of thermally aged areas.

REALM starts THINLAS Proof of Concept Project PDC-133326-I00, funded by the Spanish Ministry of Science and Innovation MICIN/AEI/10.13039/501100011033 and by the European Union NextGeneration/PRTR.

“Valorisation of CaNbGa garnets as thin disk elements in high power, high-rate, ultrashort pulsed laser oscillators (THINLAS)” project has been granted for the period 01/12/2022 to 30/11/2024.

This Project aims the extension of thin disk laser (TDL) technology, based on Yb doped YAG single crystals, to modelocked operation by using disordered single crystal Ca3(NbGa)5O12 garnets (CNGG) doped with Yb (or Tm, Ho, and Tm+Ho for emission in the λ≈ 2 µm region), to provide laser pulse durations in the femtosecond (1 fs= 10-15 s) time scale with large pulse peak powers. This is based on the large Yb3+ bandwidth in previously developed CNGG crystals, typically FWHM= 23.5 nm (or 221 cm-1), along with an optical absorption three times more efficient than in YAG, which promises thinner disks with better cooling. The productivity of laser material processing and monitoring in various fields will be greatly improved by a laser module with the characteristics described above. Just to mention some few examples: In photovoltaic silicon cell processing for CO2-free energy harvesting, surface texture free of chemical wastes will be possible. Polymeric soft transparent materials, extensively used in biomedical health care, can be welded and mechanically processed with λ≈ 2 µm laser equipment. LIDAR systems incorporating increased high power lasers and repetition rates will have longer penetration depths and better spatial resolution. Overall, the development of high power–high repletion rate lasers with ultrashort pulse duration will provide new tools for improving the wellness of the population through routes that are compatible with a sustainable and green manufacturing.

Avoiding Degradation of Upconversion Nanoparticles by Using Hydrophobic Polymer Shells

The article «Upconverting Nanoparticles in Aqueous Media: Not a Dead-End Road. Avoiding Degradation by Using Hydrophobic Polymer Shells», published in Small, 2021, 2105652 a new strategy to coat and protect β-NaYF4 upconversion nanoparticles (UCNPs) against degradation in aqueous media by growing a hydrophobic polymer shell (HPS) through miniemulsion polymerization of styrene (St), or St and methyl methacrylate mixtures.

Stability studies reveal that these HPSs serve as a very effective barrier, impeding polar molecules to affect UCNPs optical properties. Even more, it allows UCNPs to withstand aggressive conditions such as high dilutions (5 μg mL−1), high phosphate concentrations (100 mm), and high temperatures (70 °C).


PhD degree of Jorge Omar Álvarez Pérez

On July 14th 2021 Jorge Omar Álvarez Pérez obtained his PhD degree from the Autonomous University of Madrid  with the work entitled «Caracterización física y láser de monocristales de granates desordenados tipo Ca3(NbGa)5O12 dopados con Yb3+»  (Physical and laser characterization of Ca3(NbGa)5O12 disordered single crystals doped with Yb3+). The work was awared with the «cum laude» maximum qualificatlon.

A TRILOGY on Yb:CNGG lasers

The work “A roadmap for laser optimization of Yb:Ca3(NbGa)5O12–CNGG–type single crystal garnet”  published  in Journal of Materials Chemistry C vol 9, pgs 4628-4642, 2021!divAbstract

completes a trilogy of new physical knowledge and laser performance progress of this disordered cubic crystal garnet with applications in ultrashort laser pulse oscillators.

Following the path of our original proposal of CNGG Na+ modification for charge compensation of Yb3+ doping, in a first work we introduced a crystallographic model to describe the Yb3+ optical bandwidth. In a second work we disclosed the presence of a small amount of Yb3+ in centrosymmetric octahedral position with dominant magnetic dipole transitions. In the present work we describe how to minimize the crystal coloration,  the limits for Na incorporation and the relevant parameters helping for laser performance optimization.

Na and Li codoping of Yb:CNGG is found to provide the broadest tuning range along with best laser preformances.

Refractory laser oxyorthosilicates single crystals are grown under CO2 laser irradiation without use of crucible

In a recent work published in Journal of Materials Chemistry C 8, 2065, 2020!divAbstract we show that a laser material with relatively low thermal conductivity can be grown with laser quality by the Laser Floating Zone growth technique using a CO2 laser as heat source for material melting.

Key steps for this achievement have been the selection of the  (Lu0.3Gd0.7)2SiOcomposition to obtain single phase material upon resolidification and the engineering of the heating/cooling cycles.

The lack of any crucible to hold the material allows the melting of refractory compounds above 1500 ºC in oxidizing atmospheres.  This suposses a great advantage for the devellopment of crystals for mode-locked laser producing ultrashort laser pulses.

This has been possible through the collaboration with the Aveiro University.