Symposium FG
Advances in Inorganic Luminescent Materials


FG-1:IL02  Ag-Sensitized Tb3+/Yb3+ Codoped Silica-Zirconia Glasses and Glass-Ceramics
F. ENRICHI, Department of Computer Science, University of Verona, Verona, Italy

Various studies report that Tb3+/Yb3+ co-doped materials can split one UV or 488 nm (visible) photon in two near infrared (NIR) photons at 980 nm by an energy-transfer process involving one Tb3+ and two Yb3+ ions. Additionally, it was demonstrated that Ag multimers can provide an efficient optical sensitization for rare earth ions, resulting in a broadband enhanced excitation, which could have a significant technological impact, overcoming their limited spectral absorptions and small excitation cross sections. In this presentation a systematic and detailed step-by-step analysis of the energy-transfer quantum-cutting Ag-Tb3+-Yb3+ chain in glasses and glass-ceramics will be presented. Moreover, the direct Ag-Yb3+ energy-transfer will also be discussed. Results of structural, compositional, and optical characterizations will be shown, providing quantitative data for the efficient broadband Ag-sensitization of Tb3+/Yb3+ quantum cutting. A deeper understanding of the physical processes beneath the optical properties of the developed materials will allow a wiser realization of more efficient energy-related devices, such as spectral converters for silicon solar cells and light-emitting devices (LEDs) in the visible and NIR spectral regions.

FG-1:IL04  The Principles of Luminescence Thermometry – From Applications to Fundamental Questions
M. SUTA, Inorganic Photoactive Materials, Institute of Inorganic Chemistry, Heinrich Heine University Düsseldorf, Düsseldorf, Germany

There is a growing demand on remote temperature sensing with spatial resolution at the micrometer scale and below. Ratiometric luminescence thermometry is a promising and non-invasive methodology for those length scales. A particularly simple way of luminescence thermometry employs an ensemble of non-interacting luminescent centers with two thermally coupled and radiatively emitting states from the same electron configuration. The luminescence intensity ratio then follows Boltzmann’s law. Trivalent lanthanoids with their narrow line 4fn-4fn luminescence doped into crystalline powders have emerged for this type of thermometry. The ultimate desire to design such thermometers for the application of interest requires, however, a careful understanding of both thermodynamic and kinetic concepts of their performance, which is carefully compared with experiment. In this presentation, a general overview over the foundations and design guidelines of these so-called Boltzmann-type thermometers will be given. It will be demonstrated that every luminescent Boltzmann thermometer is only very precise in a small temperature window and what are strategies to overcome this obstacle. Finally, the relevance of the excited state dynamics and competition to radiative decay will be highlighted.

FG-1:IL06  Rare-earth Activated SiO2-SnO2 Photonic Glass-ceramics
THI NGOC LAM TRAN1, 2, 3, A. Szczurek1, S. Varas1, C. Armellini1, A. Carpentiero1, A. Chiappini1, E. Iacob4, G. Ischia5, S. Berneschi6, G. Nunzi Conti6, G.C. Righini6, M. Bollani7, F. Scotognella2, 8, P. Głuchowski9, A. Lukowiak9, A. Chiasera1, M. Ferrari1, 1IFN-CNR CSMFO Lab. and FBK Photonics Unit, Povo, Trento, Italy; 2Department of Physics, Politecnico di Milano, Milano, Italy; 3Department of Materials Technology, Faculty of Applied Science, Ho Chi Minh City University of Technology and Education, Thu Duc District, Ho Chi Minh City, Vietnam; 4Fondazione Bruno Kessler, Centre for Materials and Microsystems, Micro Nano Facility, Povo, Trento, Italy; 5Department of Industrial Engineering, University of Trento, Povo, Trento, Italy; 6MiPLab, IFAC-CNR, Sesto Fiorentino, Italy; 7IFN-CNR, P.zza Leonardo da Vinci, Milano, Italy; 8Center for Nano Science and Technology@PoliMi, Istituto Italiano di Tecnologia (IIT), Milan, Italy; 9Institute of Low Temperature and Structure Research, PAS, Wroclaw, Poland

In contest of light management, transparent glass-ceramics play capital importance for developing efficient photonic devices. Hereby, we present our consolidated results on novel rare-earth (RE) activated SiO2-SnO2 photonic glass-ceramics. This binary material paves a way for developing compact and efficient RE photonic devices, particularly integrated waveguide lasers, by providing possible solutions to two critical issues: (i) low absorption cross-section of RE ions, and (ii) effective strategy for fabrication of mirrors and channel waveguides. To enhance RE luminescence, wide bandgap SnO2 nanocrystals are exploited as efficient RE sensitizers. For fabricating integrated components, e.g. mirrors and channels, we exploit another appealing property of the glass-ceramics: photorefractivity with refractive index modification in the order of 10-3 under UV irradiation. The direct UV-written gratings on SiO2-SnO2:Er3+ is more energy-efficient (~ 10 times) than on the classical hydrogen loaded germanoborosilicate glasses.
Acknowledgments: This research is performed in the framework of the projects CNR-PAS “Flexible Photonics” (2020-2022); PRIN 2019 “NOMEN” (2020-2022), Polish National Agency for Academic Exchange (NAWA) grant no. PPN/IWA/2018/1/00104, and ERC-H2020 PAIDEIA GA 816313.

FG-1:IL07  TL and OSL as Research Tools in Luminescence: Possibilities and Limitations
E.G. Yukihara, Department of Radiation Safety and Security, Paul Scherrer Institute, Villigen PSI, Switzerland

Thermoluminescence (TL) and Optically Stimulated Luminescence (OSL) are complementary techniques very sensitive to defects in semiconductors and insulators. TL is usually employed for the determination of the trapping parameters (activation energy and frequency factor) of radiation-induced trapped charges in scintillators, phosphors and dosimeters. The initial rise method has been one of the most used analysis techniques. In this talk we will briefly review the status of the field with regard to the use of TL and OSL for materials research, discuss the possibilities that they offer and their limitations. Unfortunately, there are still severe limitations for the analysis of real materials. Furthermore, the TL and OSL techniques are non-specific and normally do not allow the identification of the defects involved in the process.

FG-1:IL08  Electron Transfer between Lanthanide Impurities: Insights from Multiconfigurational Calculations
J.J. Joos, LumiLab, Department of Solid State Sciences, Ghent University, Gent, Belgium; Z. Barandiarán, L. Seijo, Departamento de Química, Instituto Universitario de Ciencia de Materiales Nicolás Cabrera, and Condensed Matter Physics Center (IFIMAC), Universidad Autónoma de Madrid, Madrid, Spain

Lanthanide ions are notorious for their ability to change oxidation state. This manifests itself in the presence of low-lying excited states, so-called charge-transfer states (CTS), where an electron is transferred between the lanthanide dopant and another center in the luminescent material. Well-known are ligand-to-metal charge transfer (LMCT) states, e.g. in Eu3+-doped phosphors in fluorescence lamps that enable efficient absorption of the  254 nm Hg emission [1].  Less known are metal-to-metal charge transfers (MMCT), especially those between lanthanide impurities. In this contribution, it will be motivated that these states deserve more attention because they can dramatically impact phosphor performance. Depending on the case, they can cause additional absorption or even emission bands, quench luminescence, trap charge carriers,.…  Several examples where MMCTs between distinct lanthanides centers are important are given. In all cases, diabatic electron transfer diagrams are constructed from first principles and used for the interpretation of experimental results [2,3].
[1] C. R. Ronda, J. Lumin. 72-74, 49-54 (1997); [2] Z. Barandiarán, A. Meijerink, L. Seijo, Phys. Chem. Chem. Phys. 17, 19874-19884 (2015); [3] J. J. Joos, L. Seijo, Z. Barandiarán, J. Phys. Chem. Lett. 10, 1581-1586 (2019).

FG-1:L09  New Near-IR Optical Transitions in Sm3+ and Sm3+-Yb3+ doped Tellurite Glasses and Application in Tissue Transmission Spectroscopy
E. KUMI-BARIMAH, G. Sharma, Y. Chen, R. Tenwick, M. El-Murish, A. Jha. School of Chemical and Process Engineering, University of Leeds, Woodhouse, Leeds, UK

Tellurite glasses are known for dissolving large concentrations of RE-ions because of multiple co-ordination (pyramid, bipyramid) shell of Te6+-ionic state. The glass is known for high optical transparency in the visible to IR region up to 0.35-5 m. The glass also shows improved durability in the ambient condition, which is useful for sensing and imaging in anatomical environment. The Tellurite glasses are also known to have lower phonon energy (630-730cm-1) which may be modified by incorporating halogen ions, namely F—ions in the structure for promoting optical transitions in rare-earth ions, such as Sm3+, which is known to have strong ground state absorption in IR. We report the spectroscopic properties of Yb3+-ion, Sm3+-Yb3+ and Sm3+-Ho3+-ion co-doped tellurite glasses, fabricated by melting and quenching, for analyzing new IR optical transitions which have not been observed in oxide glass or ceramic hosts. We have analyzed the spectroscopic properties by using the visible 450 nm and near-IR 980nm laser sources. The results are also compared with the spectroscopic features, previously reported in fluoride glasses.

FG-1:IL11  Theoretical Discussion of Mn4+ Luminescence
M.G. Brik1, 2, 3, A.M. Srivastava4, M. Piasecki3, 1College of Sciences, Chongqing University of Posts and Telecommunications, Chongqing, China; 2Institute of Physics, University of Tartu, Tartu, Estonia; 3Institute of Physics, Jan Dlugosz University, Czestochowa, Poland; 4Srivastava consulting LLC, Niskayuna, NY, USA

The red-light emitting phosphors are necessary for making white light emitting diodes (LEDs) with low color correlated temperature (CCT) and high color rendering index (CRI). The Mn4+ ions are excellent activator ions to be used in those red phosphors because of several advantages, such as i) high absorption for 450 nm blue LED radiation via the 4A2g→4T2g optical transition and ii) a possibility to tune the wavelength of the 2Eg→4A2g emission transition in a wide spectral range from 620 nm (K2SiF6) to 723 nm (SrTiO3) [1]. Such remarkable tunability is caused by the nephelauxetic effect (or, in other words, by varying degree of covalency/ionicity of chemical bonds between the Mn4+ ions and their nearest environment). In this presentation several factors influencing the energy of the Mn4+ 2Eg→4A2g transition will be highlighted. Several trends across the considered compounds (related to the structure of the host materials, local symmetry of the dopant sites, and chemical bonds properties) will be indentified; in addition, practical steps towards getting red emission at a desired wavelength will be suggested [2,3]. In addition, variation of intensity of the zero-phonon line of the Mn4+ 2Eg→4A2g transition and its dependence on the local symmetry will be discussed in detail [4, 5].

FG-1:L12  Delineating the Effects of Metal Co-doping for Improved Upconversion in Inorganic Phosphors: A Case Study in Gadolinium Vanadate
A. CHAUHAN1, S. Kataria1, D. Busko1, F.A. Cardona1, A. Turshatov1, B.S. Richards1, 2, 1Institute of Microstructure Technology, Karlsruhe Institute of Technology, Eggenstein-Leopoldshafen, Germany; 2Light Technology Institute, Karlsruhe Institute of Technology, Karlsruhe, Germany

Despite recent advances, upconversion (UC) in inorganic phosphors remains relatively inefficient. Co-doping with metals is often attempted to improve UC performance, however the underlying mechanism for such improvements is still unclear and poorly investigated. Furthermore, co-doping with metal ions can often produce a host of effects such as lattice modification, size enlargement, and creation of vacancies. In this work, progress has been made to isolate and assess the relative contribution of such phenomena towards improved luminescence using GdVO4:Yb/Er as a model system. Nano-phosphors co-doped (5-25%) with Zn or Sc were prepared through aqueous precipitation. The quantum yield (QY) improved by 60× for samples co-doped with Zn, whereas only ~20× increase was noted in Sc co-doped samples for 980 nm to visible UC. Analysis revealed that despite a smaller lattice in Sc co-doped samples, Zn co-doping produced brighter luminescence owing to larger particles. Further confirmation for this was provided by (Zn/Sc-free) larger (micro) particles prepared using solid-state synthesis. These larger particles displayed comparable ~50× improvement in the QY thereby, confirming the dominating role of size-related effects. Finally, some insight into the role of defects was also inferred.

FG-2:IL02  Direct Laser Patterning as a Possible Strategy for Spatially Controlled QDs Formation
F. Antolini, F. Limosani, R. Carcione, ENEA C.R. Frascati, Fusion and Technologies for Nuclear Safety and Security Department, Physical Technologies for Safety and Health Division, Micro and Nanostructure Laboratory, Italy; L. Orazi, Department of Science and Methods for Engineering, University of Modena and Reggio Emilia, Reggio Emilia, Italy; R. Gillanders, I.D.W. Samuel, University of St. Andrews, St. Andrews, UK

In this work, the advances on Direct Laser Patterning (DLP) for the synthesis of photo-luminescent semiconductor quantum dots (QDs) is reported. Two main aspects of the DLP are taken into consideration: i) the suitable material synthesis and ii) the parameters of laser patterning to achieve the QDs formation. The synthesis and the decomposition of different precursors of II-VI QDs is described. The direct laser patterning methodology is preceded by a study of the thermal decomposition of the single/double source precursor in film together with the polymer to verify the formation of the QDs also as a function of different organic ligands. The laser patterning is then described in the same conditions studied for the film during the thermal annealing. The properties of the patterned QDs are then described as a function of laser parameters like, for example, the laser fluence. Finally, a potential application of this technique together with materials is described in the field of quantum dot display manufacturing (www.miledi-h2020.eu) in case of small/mid volumes of production.

FG-3:IL01  Tailored Upconversion Nanocrystals Optimized for High Quantum Yield or Efficient Energy Transfer
C. Homann, C. Drees, A.N. Raj, R. Kurre, J. Piehler, M. Haase, University of Osnabrück, Osnabrück, Germany; K. Busch, University of Münster, Germany; L. Krukewitt, F. Frenzel, B. Grauel, C. Würth, U. Resch-Genger, BAM, Berlin, Germany; J. Bolze, Panalytical, Almelo, The Netherlands

Upconversion nanoparticles (UCNP) convert near infrared into visible light at much lower excitation densities than used in classic two-photon absorption microscopy and can therefore be excited with negligible background, providing exciting potential as light-controlled sensors and actuators of biological processes. [1] We prepared NaYF4:Yb,Er/ NaYF4 core/shell UCNP with different mean sizes ranging from 15 to 45 nm via a modified synthesis procedure based on anhydrous rare-earth acetates. Absolute measurements of the photoluminescence quantum yield at a series of different excitation power densities show that the quantum yield of 45 nm core/shell particles is already very close to the quantum yield of microcrystalline UC phosphors. [2] UCNPs with dopant concentrations and core/shell structures optimized for higher excitation densities show efficient energy transfer (LRET) inside living cells. [3] Due to their extremely narrow size distribution, UCNPs form colloidal crystal, as confirmed by small-angle X-ray scattering (SAXS). [4]
[1] M. Haase, H. Schäfer, Angew. Chem. Int. Ed. 2011, 50, 5808. [2] C. Homann et al., Angew. Chem. Int. Ed. 2018, 57, 8765. [3] C. Drees et al., Angew. Chem. Int. Ed. 2016, 55, 11668. [4] C. Homann et al., Part. Part. Syst. Charact. 2019, 36, 1800391

FG-3:IL03  Multiphoton Fluorescence Upconversion with Hetero-structured 2D Colloidal Nanocrystals
A.H. Khan1,2, G.H.V. Bertrand2, A. Teitelboim3, A. Polovitsyn2, J. Planelles4, J.I. Climente4, D. Oron3, I. Moreels1,2, 1Department of Chemistry, Ghent University, Ghent, Belgium; 2Istituto Italiano di Tecnologia, Genova, Italy; 3Department of Physics of Complex Systems, Weizmann Institute of Science, Rehovot, Israel; 4Departament de Química Física i Analítica, Universitat Jaume I, Castelló de la Plana, Spain

Two-dimensional fluorescent colloidal nanocrystals combine the flexibility of solution-processed nanomaterials with the advantages of a (quasi-)2D band structure that offers enhanced optical properties compared to 0D quantum dots. In this presentation, we discuss the synthesis of a novel ternary heterostructure, composed of a CdSe core, laterally extended by a CdS tunneling barrier, and finally a CdTe crown. The type-II band offset between CdSe and CdTe, in combination with the CdS barrier layer, allows to separate core and crown electron and hole wave functions, yielding an emission spectrum consisting of a long-lived indirect transition at 625 nm, as well as direct CdSe and CdTe transitions around 510 nm and 575 nm, resp. Up to 2% of the total emission can be attributed to CdSe, and we were able to demonstrate two- and even three-photon fluorescence upconversion by exciting the sample with red and near-infrared photons, to yield green emission from the CdSe core.
Acknowledgments: Horizon 2020 ERC Starting Grant PHOCONA, MINECO project CTQ2017-83781-P, UJI project B2017-59, Ministero degli Affari Esteri e della Cooperazione Internazionale, Ministry of Science, Technology and Space of the state of Israel, Crown Photonics Center of the Weizmann Institute of Science.

FG-3:IL04  Band Gap Engineering in Luminescence Thermometry – Pros and Cons
E. ZYCH, P. Bolek, M. Sójka, D. Kulesza, J. Zeler, J. Jedon, J. Trojan-Piegza, A. Shyichuk, University of Wroclaw, Faculty of Chemistry, Wroclaw, Poland

The development of technology places new demands on, among other things, temperature measurement techniques. The miniaturization in biology, medicine, and in engineering is of particular importance. Temperature measurement with sub-micron resolution with high accuracy and sensitivity is a new challenge for science and technology. If we add the wide measuring range to the requirements, the problem becomes especially difficult. Wide-range luminescent thermometers are of interest in important areas such as the aerospace industry. In these areas, fast, accurate and reliable measurements of rapidly changing temperatures are of particular importance. Luminescence thermometry is believed to become the technology of choice for such purposes, as it is resistant to disturbances by an electromagnetic field and the sensitivity and accuracy of measurements may be tuned for the specific requirements. This does not mean that such designing is easy to implement.
In this presentation, we shall report a new approach toward wide-range high-quality luminescence thermometry. Phosphors activated with either Pr3+ or Eu2+ will be examined and discussed. These ions are capable of generating two types of emissions: (i) broad-band intra-configurational 5f4f and narrow-lines inter-configurational 4f4f ones. We will demonstrate that the sensitivity of such sensors may be deliberately tuned by means of band gap engineering to reach its maximum at temperatures where it is most needed. Possible expectations for further development using this approach will be discussed.
This research was supported by the Polish National Science Center (NCN) under the grant #UMO2018/29/B/ST5/00420.

FG-4:L01  Intracellular Temperature Mapping of Cancer Cells using Ln3+-based Polymeric Micelles
J. ZELER1, C.D.S. Brites2, R. Piñol3, Yuanyu Gu3, 4, P. Téllez5, A.N. Carneiro Neto2, T.E. da Silva2, 6, R. Moreno-Loshuertos7, P. Fernandez-Silva7, A. Gallego7, L. Martinez-Lostao7, A. Martínez8, L.D. Carlos2, A. Millán3, 1Faculty of Chemistry, University of Wroclaw, Wroclaw, Poland; 2Phantom-g, CICECO-Aveiro Institute of Materials, Department of Physics, University of Aveiro, Aveiro, Portugal; 3ICMA, Institute of Materials Science of Aragon, CSIC-University of Zaragoza, 50008 Zaragoza, Spain; 4School of Materials Science and Engineering. Nanjing Tech University,  Nanjing PR China; 5Servicio de Apoyo a la Investigación. University of Zaragoza, Zaragoza, Spain; 6Department of Fundamental Chemistry, Federal University of Pernambuco, Recife, PE, Brazil; 7Departamento de Bioquímica, Biología Molecular y Celular, Universidad de Zaragoza, Zaragoza, Spain; 8Departamento de Electrónica de Potencia, I3A, Universidad de Zaragoza Zaragoza, Spain

Measurement of thermogenesis in individual cells is a remarkable challenge due to the complexity of the biochemical environment and to the rapid and yet not well-understood heat transfer mechanisms throughout the cell. We will present a unique system for intracellular temperature mapping in a fluorescence microscope (uncertainty of 0.2 K) using rationally designed luminescent Ln3+-bearing polymeric micellar probes (Ln=Sm, Eu) incubated in breast cancer MDA-MB468 cells (the scheme on the Figure 1). 2D thermal images recorded increasing the temperature of the cells culture medium between 296 and 304 K shows inhomogeneous intracellular temperature progressions up to ~20 degrees and subcellular gradients of ~5 degrees between the nucleolus and the rest of the cell, illustrating the thermogenic activity of the different organelles and highlighting the potential of this tool to study intracellular processes.
References: [1] Piñol at al., Real-time intracellular temperature imaging using lanthanide-bearing polymeric micelles. Nanoletters, 20, 2020, 6466- 6472.
Acknowledgement: This project has received funding from the European Union’s Horizon 2020 FET Open programme under Grant Agreement No. 801305.

FG-4:IL02  Multi-wavelength Lanthanide-based Nanoparticles for Biomedical and Beyond Applications
E. Hemmer, University of Ottawa, Department of Chemistry and Biomolecular Sciences, Ottawa, Ontario, Canada

Based on their outstanding optical and magnetic properties, lanthanide(Ln)-based compounds have been suggested for a wide range of applications including the fields of biomedicine, optoelectronics, and solar energy conversion. For instance, the capability of Ln-based materials to emit visible and near-infrared (NIR) light under NIR excitation is highly sought after when aiming for biomedical applications. This is as NIR light penetrates deeper into biological tissue and is less phototoxic than UV light commonly used for optical bioprobes. Besides, Gd3+ ions are well-known for their capability to act as contrast agent in magnetic resonance imaging (MRI). Lanthanide fluorides (MLnF4, M = alkali metal) are an excellent choice when seeking bright emitters or magnetic properties for biomedical applications. In this vein, we developed rapid microwave-assisted strategies towards Ln3+-doped or undoped NaGdF4 nanoparticles (NPs). Controlling process parameters and precursor chemistry enables phase-selective synthesis of NPs with sizes tailored at the sub-10nm regime. Resulting NPs are shown to be promising candidates for biomedical applications, i.e. as MRI contrast agents or luminescent bioprobes, and beyond.

FG-4:IL03  Eu(III) and Tb(III) Complexes for Biosensing Applications
F. Piccinelli, C. NARDON, M. Bettinelli, Luminescent Materials Laboratory, University of Verona, Verona, Italy

Metal complexes are broadly employed as probes for optical imaging and optical sensing of biologically relevant targets. In particular, the use of luminescent lanthanide complexes shows several important advantages related to the peculiar properties of the metal centered f↔f transitions [1]. In particular, the fine tuning of the luminescent features of these complexes upon interaction with bioanalytes is of great importance in this field. In this contribution, we discuss the performance of new chiral Eu(III) and Tb(III) complexes, by analyzing the luminescence spectra, in sensing experiments towards important analytes, such as bicarbonate [2], lactate [3], citrate [4] and Bovine Serum Albumin (BSA) [5].
References: [1] J.-C. G. Bünzli Chem. Rev. 110 (2010) 2729. [2] F. Piccinelli, C. De Rosa, A. Melchior, G. Faura, M. Tolazzi, M. Bettinelli Dalton Trans. 48 (2019), 1202. [3] M. Leonzio, A. Melchior, G. Faura, M. Tolazzi, M. Bettinelli, F. Zinna, L. Arrico; L. Di Bari, F. Piccinelli New J. Chem. 42 (2018), 7931. [4] C. De Rosa, A. Melchior, M. Sanadar, M. Tolazzi, A. Duerkop, F. Piccinelli submitted for publication. [5] C. De Rosa, A. Melchior, M. Sanadar, M. Tolazzi, A. Giorgetti, R. P. Ribeiro, C. Nardon, F. Piccinelli Inorg. Chem. 2020, 59, 12564.

FG-4:L04  Pr-Activated Garnets for Wide-range Optical Thermometry
D. KULESZA, J. Zeler, E. Zych, University of Wroclaw, Faculty of Chemistry, Wroclaw, Poland

Pr-activated garnets are specific phosphors in which the Pr3+ ion can be efficiently excited optically using UV-C radiation and can produce three types of emissions, afterward. Thus, the 5d4f broadband luminescence in the UV-blue part of the spectrum is generated as well as narrow lines resulting from the 3P03HJ and 1D23H4 transitions in the bluish-green and red part of the spectrum appear, respectively. The three emissions have much different properties and, consequently, their temperature dependence is diverse. Therefore, we considered the Pr3+ luminescence very attractive for luminescence thermometry. Since garnets are mostly thermodynamically stable oxides they can withstand drastic changes of temperature from helium to above 1500 °C even. This makes them easy to operate also in quite harsh conditions.
In the presentation, we shall review in detail the possibilities to control complex electronic processes in Pr activated garnets important for luminescence thermometry. The host lattice–activator interaction will be discussed and conclusions concerning the possibility to design luminescent thermometers capable of effective serving for temperature measurements over a broad range of temperatures will be considered. We believe that Pr-doped garnets may be attractive luminescence thermometers for such demanding applications as measurements at low, intermediate, and high temperatures, which is nowadays a real challenge in this field.
Acknowledgement: This research was supported by the Polish National Science Center (NCN) under the grant #UMO2018/29/B/ST5/00420.

FG-4:L05  Facile Fabrication of Carbon Dots based Fluorescent Strips for Florimetric ON-OFF Sensor
C.M. Singaravelu, X. Deschanels, C. Rey, J. Causse, ICSM, University of Montpellier, CEA, CNRS, ENSCM, Marcoule, France

Carbon dots (CDs) are an emerging smart material that is applied in a wide range of applications including sensors, photocatalysis, bioimaging, and optoelectronic devices. In recent decades, CDs have been an alternative to semiconductor-based quantum dots due to their unique optical properties. CDs are highly fluorescent, zero in dimensional (<10 nm), sp2 and sp3 hybridized carbon core with highly surface-functionalized nanomaterials. While thousands of studies have already been published, carbon dot research is still emerging due to its unique structural and photoluminescent properties. Herein, we report a synthesis of highly fluorescent, amphiphilic, solid-state yellow luminescent, dual emissive carbon dots and their fabrication as strip probes for metal ion sensing. Remarkably, a simple tuning of the stoichiometric ratio of precursors leads to solid-state yellow luminescent and dual emissive CDs. In addition, we investigated, how nitrogen speciation, graphitization and surface functionality of carbon dots (CDs) can impact the structure-optical property relationship of CDs in solution and solid-state. We fabricated CDs-based fluorescent strips and utilized them as an ON-OFF fluorescence sensor to detect Hg2+ metal ions in an aqueous medium with great sensitivity and selectivity. These results would give an approach for tuning the fluorescence and structural characteristics of CDs to develop a simple strip-based probe without a self-quenching issue for sensor applications.
References: 1. Junjun Liu, Rui Li, and Bai Yang (2020) Carbon Dots: A New Type of Carbon-Based Nanomaterial with Wide Applications, ACS Cent. Sci. 6, 12, 2179–2195; 2. Chandra Mohan Singaravelu,  Xavier Deschanels, Cyrielle Rey, and Jérémy Causse. (2021) Solid-State Fluorescent Carbon Dots for Fluorimetric Sensing of Hg2+ ACS Appl. Nano Mater.  4, 6, 6386–6397.

FG-5:IL02  Development of Novel Chemiluminescent Materials for Cancer Treatment
C.M. Magalhães, P.G. Berdullas, J.C.G. Esteves da Silva, L. Pinto da Silva, Chemistry Research Unit of University of Porto, Porto, Portugal

Photodynamic therapy (PDT) is already in wide clinical use for certain types of cancer. It has three requirements: a nontoxic photosensitizer, light of a specific wavelength and molecular oxygen. The light is used to activate the photosensitizer, which then converts the molecular oxygen into reactive oxygen species (ROS) capable of destroying tumor cells. PDT presents significant advantages over conventional cancer therapies, such as its minimally invasive nature, fewer side effects, fast healing of healthy tissue and high spatiotemporal precision. Unfortunately, its dependence on light has limited this therapy to treating tumors on or just under the skin or on the outer lining of organs/cavities. Herein, we have developed single-molecule photosensitizers able of intracellular and tumor-selective self-activation, due to a chemiluminescent reaction triggered solely by a cancer marker. Given this, the photosensitizer is directly chemiexcited to triplet excited states capable of generating ROS, without requiring any light. Cytotoxicity assays demonstrated that these molecules present significant toxicity toward several tumor types, while not inducing toxicity toward different non-cancer cells. Thus, we have retained the advantages of PDT while solving its light-dependency.

FG-6:IL01  Simulating Out-coupling and Radiation Patterns from Luminescent Materials in Lighting Applications
Y. Meuret, B. Karadza, A. Correia, KU Leuven, ESAT, Light and Lighting Laboratory, Ghent, Belgium

Most light sources for lighting applications contain one or more luminescent materials. These are used for two main purposes: improving the color rendering performance of solid-state light sources and avoiding the green gap of both LEDs or laser diodes. However, total internal reflection at the air-material interface of the luminescent material can significantly reduce light source efficacy. It is therefore of vital importance to extract the converted light by the luminescent material as efficiently as possible. In practice two relative straightforward methods can be used: controlling the light scattering properties of the luminescent material or increasing the source étendue. In both cases certain trade-offs have to be made regarding efficacy, color uniformity and source brightness. In order to analyze these trade-offs in detail, advanced simulation tools can be used. This presentation discusses two different methods for modeling the system performance of light sources that rely on luminescent materials: the extended adding-doubling method and Monté-Carlo ray-tracing. The possibilities and limitations of both methods are discussed in detail, together with different examples of relevant out-coupling problems that have been analyzed with those methods.

FG-6:L02  Optimal Quantum Dot Luminescent Solar Concentrator Double and Triple Tandem Structures Based on Ray Tracing Simulations
T. de Bruin, W. van Sark, Copernicus Institute of Sustainable Development, Utrecht University, Utrecht, The Netherlands

Quantum dot based luminescent solar concentrators (QDSCs) are a special class of transparent photovoltaics, especially suited for building integrated photovoltaics. Photons are absorbed by luminescent species in a waveguide and emitted at red-shifted wavelength. Due to total internal reflection, 3/4 of the photons are absorbed by the solar cells attached to the sides. Successful deployment requires high conversion efficiency and high transparency, which are contradictory requirements. Studies have shown typical efficiencies of about 5% at reasonable transparency for window applications, while the apparent color of such a device may not be suited for indoor comfort. Therefore, a combination of two or three transparent LSC plates of different color are researched to reach high efficiency, high transparency, and color neutrality. We have performed Monte-Carlo ray tracing simulations to investigate double and triple QDSCs and have assessed their optical and electrical performance. To this end, eight quantum dot materials and structures have been chosen based on absorption, emission properties and Stokes’ shift. In our contribution, we will show optimum combinations with regards to key performance indicators optical efficiency, transmitted light and visual performance.

FG-6:L03  Thermometric and Pressure Independent Nano-probe via Upconversion Photoluminescence: Application to Temperature Measurement in Tribological Contacts
YUJIAO ZHOU, L. BOIS, C. JOURNET-GAUTIER, Lab. des Multimatériaux et Interfaces, UMR CNRS 5615, Université Lyon1-CNRS, Villeurbanne, France; S. DESCARTES, D. PHILIPPON. Univ Lyon, INSA Lyon, CNRS, LaMCoS - UMR5259, Villeurbanne, France; G. LEDOUX, Institut Lumière Matière, UMR CNRS 5306, Université Lyon1-CNRS, Villeurbanne, France

Reduction of friction and heat dissipation in mechanical contacts is a major concern. Experimental techniques to measure temperature at the surface of solids in contact are then a great interest. Photoluminescence probes have attracted more and more attention. Considered as an efficient, non-destructive, and high-accuracy sensor, photoluminescent upconversion (UC) probes have a great potential. Pressure is also a major parameter varying in the contact, photoluminescence's independence to pressure is important. In this study, the nano-probe has been chosen as the nanoparticles (NPs) gadolinium orthovanadate (GdVO4), doped 10% Yb and 2% Er. Thanks to the UC energy transformation from Yb to Er, these NPs (< 50 nm) emit strongly green lights under NIR laser. The thermometry calibrations are performed at 25 - 200°C at ambient pressure and under pressure (up to 1 GPa). The luminescence intensity ratio (LIR) of the thermally coupled emission peaks is shown to be independent to pressure and to range linearly with temperature, and this variation is reversible. According to these analytical results, the {GdVO4, Yb; Er} NPs can be applied as thermometer probes in tribological friction for futures in situ measurements.

FG-6:IL04  Nanomaterials and Molecular Photoanodes for Light-driven Water Splitting
J. Li, H. Chen, C.A. Triana, YONGGUI ZHAO, G.R. Patzke, University of Zurich, Department of Chemistry, Zurich, Switzerland

Photoelectrochemical water splitting is a promising route to directly store solar energy in chemical bonds. While cocatalyst loading of photoanodes facilitates the demanding oxygen evolution reaction, their precise functionalities remain to be fully understood for optimal design. As noble metal-free molecular cocatalysts keep attracting interest, we brought forward a series of flexible cobalt(II) cubane photocatalysts for water oxidation.[1] We newly immobilized them on hematite photoanodes and revealed their dynamic functionality on hybrid photoanodes as a function of the applied potential. Their transition from hole reservoir to catalytic centers was monitored with complementary photoelectrochemical analyses.[2] Further, we generated insight into the different surface states of hematite photoanodes. We analyzed their reaction kinetics and dynamic interplay and found them to depend significantly on the applied operational parameters.[3]
[1] F. Song, K. Al-Ameed, M. Schilling, T. Fox, S. Luber, G. R. Patzke, J. Am. Chem. Soc. 2019, 141, 8846. [2] J. Li, W. Wan, C. A. Triana, Z. Novotny, J. Osterwalder, R. Erni, G. R. Patzke, J. Am. Chem. Soc. 2019, 141, 12839. [3] J. Li, W. Wan, C. A. Triana, H. Chen, Y. Zhao, C. K. Mavrokefalos, G. R. Patzke, Nat. Commun. 2021, 12, 255.

FG-6:L05  Unclonable Anti-counterfeiting Based on Randomly Distributed Microphosphor Particles under Microlens Arrays
V. KUMAR, S. Dottermusch, A. Chauhan, N. Katumo, B.S. Richards, I.A. Howard, Institute of Microstructure Technology, Karlsruhe Institute of Technology, Eggenstein-Leopoldshafen, Germany Light Technology Institute, Karlsruhe Institute of Technology, Karlsruhe, Germany

Here, we demonstrate an unclonable label based on a polymer layer doped with phosphor microparticles laminated with a microlens array on top. When the label is illuminated, the illumination light is focused in a small volume under each microlens. If this volume is occupied by a microparticle, bright luminescence is produced that is easily observed by a standard camera (such as that in a smartphone). The random pattern of bright points is the fingerprint of the label used for authentication. Further, a change in angle of incidence of the illumination light shifts the location of the focal points under each microlens. This leads to another subset of focal volumes overlapping with microphosphors and different fingerprints. The label is compatible to function with an upconversion (UC) or downshifting (DS) phosphor particles. We have implemented gadolinium oxysulfide (Gd2O2S: 18% Yb3+/2% Er3+) as the UC phosphor and a commercialized Ce3+ doped yttrium aluminum garnet (YAG) phosphor as the DS particles. We demonstrate a set of 10^4 test-reference images comparison, resulting in a probability of ~10^-15 for a false positive authentication. Moreover, a validation of the label's unclonable concept is also presented using a single smartphone as an illumination and authentication device.

FG-7:IL01  It’s Getting Hot in Here: Intracellular Luminescent Thermometers
L.D. Carlos, Phantom-g, CICECO-Aveiro Institute of Materials, Physics Department, University of Aveiro, Campus Universitário de Santiago, Aveiro, Portugal

The emergence of luminescent nanothermometry during the last decade opened up the possibility of measure thermal flows at spatial scales below 10 μm, unreachable by conventional electrical methods. Diverse phosphors capable of providing a contactless thermal reading through their light emission properties have been examined, e.g., polymers, DNA or protein conjugated systems, organic dyes, quantum dots, and trivalent lanthanide (Ln3+) ions incorporated in organic-inorganic hybrids, multifunctional heater-thermometer nanoplatforms, upconverting, downconverting and downshifting nanoparticles. In the last couple of years, the focus of luminescence thermometry has gradually shifted from the fabrication of more sensitive nanoarchitectures towards the use of the technique as a tool for thermal bioimaging and the unveiling of properties of the thermometers themselves and their local surroundings. After a general perspective of the work done on luminescence nanothermometry since the explosion of the field at one decade ago, the lecture will be focused on recent examples illustrating the potential of the technology to measure the intracellular temperature.

FG-7:IL04  Photoactive Nanoclay Carriers and Functionalized Upconverting Nanoparticles for Biophotonic Applications
A. DE CAMARGO, São Carlos Institute of Physics, University of São Paulo, São Carlos, SP, Brazil

Cytotoxicity and efficient targeting are two major concerns in developing nanomaterials for biophotonic applications such as PDT and imaging. Nanodisks of Laponite RD® (LAP) clay combine the advantages of large surface areas, ability to alter polarity of attached molecules, the versatile functionalization through surface chemistry and biodegradability. By using LAP as a nanocarrier, we were able to effectively deliver SiPc-phthalocyanine molecules to MCF-7 breast cancer cells and promote very efficient (97%) photodynamic therapy (PDT). Results indicate that PDT with nanoclays is a field with auspicious potential, as LAPs are considered to be a key nanoplatform to further in vivo studies. Additionally, LAP was successfully used with the aim of masking cytotoxicity and granting stability to triplet emitting cyclometalated Ir(III) complexes, which are promising candidates for bioimaging and biosensing. By camouflaging the intrinsic complex toxicity, this method potentially extends the palette of available imaging and sensing dyes to any metal−organic complexes. Equally promising are upconversion core-shell mesoporous silica-coated NaYF4:Yb:Er NPs, studied in our group, which can carry and photosensitize PDT active molecules against tumors and bacteria, act as a bioimaging probe.


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