Novel nanosized upconverting oxide materials for practical applications (2017 - 2020)

Project leader Tamara Gavrilovic

Agreement No

Research application No

The goals of this interdisciplinary project proposal are related with the resolution of problems widely investigated in the field of luminescent up-converting nanomaterials, such as: stabilization, modification, (bio)functionalization of the surface and toxicity of materials. The design and preparation of multifunctional nanomaterials with improved performance have aroused considerable interest in recent years. The development of synthetic methods which will provide materials of high purity, crystallinity, uniformity of size, morphology, and composition, is one of the most challenging problems in materials science. Several groups of luminescent up-converting nanomaterials will be produced, coated and modified. Among them are: metal oxides (TiO2, ZnO, ZrO2, HfO2), aluminates (SrAlO4), silicates (SrSiO4) and phosphates (APO4, A = La, Y, Gd, Lu). The properties of these functional nanostructures will be examined from the fundamental point of view; however, adapted for practical applications including needs for specific high-tech products required by Latvian industry. As an example, proposed structures might be employed as solid-state laser amplifiers, as well as for imaging agents, cancer detection and drug delivery. The implementation of this project will be significant not only for scientific research, but also for major society due to diverse potential in physical, biomedical and pharmaceutical applications, and various technical solutions.

Project progress


Thermo-stimulated luminescence (TSL) measurements on first YbPO4: 10mol%Eu3+ sample, induced by X-rays and recorded at 9K showed some interesting results. The research will be moved on by recording TSL emission spectra of YbPO4 systems doped with distinct Eu3+ concentrations (5mol% and 2mol%) and analysis of results.

During September, far-reaching academic study on up-conversion luminescence enhancement of optically active GdF3:Er3+,Yb3+@SiO2 core-shell nanostructure produced by green, simple, economical, co-precipitation method focused on preparation and up-conversion properties of high-intensity red light-emitting GdF3: Er3+, Yb3+ phosphor made by simple and green co-precipitation process was presented at prominent Nanophotonics and Micro/Nano Optics International Conference 2019, held in Munich, Germany. The research will be continued, toward the production of advanced phosphorescent materials with improved performances, compelling biomedical, multicolor contrast agents and temperature sensor applications. By now, phase composition, morphology and luminescence properties of obtaining GdF3: Er3+, Yb3+ and GdF3: Er3+, Yb3+@SiO2 systems were systematically investigated.

Project progress

(05.04.2019- 04.07.2019)

Phosphors based on fluoride hosts, doped with distinct rare-earth ions (Er3+, Ho3+, Yb3+) with different morphologies and sizes were successfully obtained by microwave and co-precipitation routes. Results of TGA/DTA analysis, diffuse reflectance spectra and structural examination via powder X-ray diffraction measurements and Rietvled refinement of X-ray data were acquired. The reviled size of ultra-small nanoparticles, varies from 2.96 till 9.06 nm. Aditionally, PVP modification of LaF3:Er3+, Yb3+ was achived by microwave route during mobility to the partner organization, Vinča Institute of Nuclear Sciences, Belgrade, Serbia. Also, magnesium spinel (MgAl2O4) powders doped with Yb3+ ions have been synthesized by fast and economic co-precipitation method and heat-treated at 800 °C for 2 h (crystallite size 2.96 nm). Spinel has high melting point (2135 °C), good thermal shock resistance and mechanical strength, very important material in different fields of application, especially as transparent armor ceramics, semiconductors, sensors, catalysts, phosphors and pigments. Further investigations still has to be done.

During May, comprehensive academic study investigating preparation and up-conversion properties of high-intensity red light-emitting GdF3:Er3+, Yb3+ phosphor made by simple and green co-precipitation process was presented at distinguished 8th International Conference on Nanotechnology & Materials Science, held in Amsterdam, Netherlands.

We will continue our research, geting advanced phosphorescent materials with improved performances, compelling biomedical and temperature sensor applications,  and optimistically create an actual device.

Project progress

(05.01.2019- 04.04.2019)

Samples based on fluoride hosts (GdF3 and LaF3) doped with different concentration of rare-earth ions (Er, Er/Yb) were successfully fabricated by simple, green co-precipitation route. Optical, structural and morphological properties of this obtained structures (SEM/TEM measurement, XRD and EDX analysis) were studied systematically. Also, new photonic material YbPO4:10mol%Eu3+ were obtained by fast sol-gel synthetic route.

In February, concurrently with an activity-mobility trip to partner organization, Vinča Institute of Nuclear Sciences, Belgrade, Serbia, results of structural examination via powder X-ray diffraction measurements and Rietvled refinement of YbPO4:Eu3+ nanomaterials were obtained, including luminescente emission spectra of GdF3:Er,Yb (600℃, 2h) and GdF3:Er,Yb@SiO2 (600℃, 2h) recorded over temperature range 307-473 K.

During March, the study on fabrication and down-/up-conversion properties of light-emitting YbPO4:Eu3+@SiO2 hybrid nanosctructures was presented at the 17th International Conference on Emerging Materials and Nanotechnology, Berlin, Germany.

Preparation of core-shell GdF3:Er,Yb@YbF3 structure by combination of co-precipitation route, silica layering and etching. Physico-chemical characterization: powder X-ray diffraction measurements and EDX analysis of asquired material.

Popularization of project activities and goals, filming scientific broadcast with Latvian television, invited by the State Education Development Agency.

Project progress

January 11, 2019

New up-/down conversion materials doped with distinct lanthanide ions were successfully prepared (GdF3, DyPO4 and YbPO4) via sol-gel and precipitation route which were optimized by setting the appropriate conditions (pH and temperature). Light emitting photonic materials YbPO4:Eu (has never been characterized and synthesized before) displayed uniform morphology, high crystallinity and satisfactory emission intensity even from higher excited states (5D1, 5D2, 5D3). This rarely observed results show that the phonon energies are low enough to lead to the observation of high energy lines in 450-570 region which are comparable with fluoride, germanate and tellurite glasses.

GdF3:Er, Yb showed it’s possibility to tune color with annealing temperature, valuable property for both, multicolor imaging and therapy (drug delivery). Detected Er3+ emissions under eye safe 1531 nm excitation can be used for a wide range of applications in optical communications.

Obtained samples (d~20 nm), were protected with amorphous silica. Presence of free silanol groups on the surface not only results in high solubility in water, but also allows further conjugation with various molecules, which is highly useful for medical and bio-applications of the hybrid structures.

Supplementary modifications and investigation of materials for applications as temperature sensors, enlarging and tunning the emission intensity as well as production of multifunctional core-shell structures are our next steps.

Project progress

October 11, 2018

Colloidal up-conversion LaPO4 ultra-small nanoparticles (2 nm) doped with different concentrations of sensitizer (Ho3+, Tm3+ and Er3+) and Yb3+ as activator ions were systematicaly studied by XRD, TEM, down and up-conversion luminescence spectroscopy at room and low temperature. Samples with satisfactory luminescent intensity, of each corresponding dopant, were obtained.

During September, the work ‘’Thermoluminescence and high-resolution luminescence spectroscopy of LaPO4:Eu nanoparticles’’ investigating defects effect on luminescent lanthanum nanoparticles was presented at 5th International Conference on the Physics of Optical Materials and Devices (ICOM 2018), Igalo, Montenegro.

In August, the work entitled ‘’Room temperature synthesis of ultra-small colloidal LaPO4:Eu3+ and Tm3+/Yb3+ and Er3+/Yb3+, Ho3+/Yb3+ doped – REVO4 (RE = Gd3+, Y3+, Lu3+) multifunctional down-converting and up-converting nanoparticles’’was presented at 32nd Conference of European Colloid and Interface Society.

We will continue our work, hopefully acquiring advanced phosphorescent materials with improved performances, and important (biomedical) applications.

Project progress

July 11, 2018

High resolution luminescence spectroscopy and thermoluminescence of different size LaPO4:Eu3+ nanoparticles

A new publication within ERDF Post Doc project No. which includes detailed study of particle's size effect and surface defects on the luminescence intensity, shape and structure of spectra has been published.

Tamara Gavrilović, Katrīna Laganovska, Aleksejs Zolotarjovs, Krisjanis Smits, Dragana J. Jovanović, Miroslav D. Dramićanin

Nanoparticles (5 nm) and nanorods (2 nm × 15 nm and 4 nm × 20 nm) of monoclinic monazite LaPO4:Eu3+ were prepared by reverse micelle and co-precipitation routes. Effects of the particle size and surface defects on the intensity of luminescence and the emission spectrum shapes were analyzed by high-resolution spectroscopy under laser (266 nm) and X-rays excitation. All synthesized samples showed similar spectral features with characteristic Eu3+ ions emission bands. The quantity of Stark's components is found to be the largest in the 5 nm nanoparticles. Also, in this sample, the luminescent intensity is the highest. Additionally, the thermally stimulated luminescence was studied for the most dominant peak at 611.5 nm. The TSL glow peak intensity is found to be enhanced in the case of heat-treated sample when compared with as-prepared samples. The glow curves were analyzed and trap parameters were estimated and discussed throughout the paper. The highest values of decay lifetimes (τ) and emission quantum efficiency for 5D07F2 were obtained for heat-treated sample. The elucidation of luminescence intensity dependence on the nanoparticle size is not only fundamental, but also an applied task important for estimation of possible application of nanoparticles for creation of new nanocomposite luminescence materials or even the nanoscintillators for medical use. Optical Materials

Up-conversion luminescence of GdVO4:Nd3+/Er3+ and GdVO4:Nd3+/Ho3+ phosphors under 808 nm excitation

Dragana J. Jovanovića, Tamara V. Gavrilović, Slobodan D. Dolić, Milena Marinović-Cincović, Krisjanis Smits, Miroslav D. Dramićanin

Here, in order to produce up-conversion luminescence emission of GdVO4-based materials under 808 nm excitation, double-doped GdVO4-based polycrystalline powders, GdVO4:xmol%Ho3+/1mol%Nd3+ and GdVO4:xmol%Er3+/1mol%Nd3+ (x = 0.5 and 1), were successfully prepared by a high-temperature solid-state reaction technique. By making use of an inexpensive laser diode (1 W) as an excitation source, UC luminescence emission (recorded in the 500–715 nm range) was successfully achieved in all the samples under 808 nm illumination. Near-infrared pumping produced emission bands in the green, yellow-orange and green regions of the visible spectrum. The dominant band originating from the 4G7/2 4I11/2 transition in Nd3+ ions was observed around 597 nm in all studied materials. Optical Materials

Chapter 2: SYNTHESIS OF MULTIFUNCTIONAL INORGANIC MATERIALS: FROM MICROMETER TO NANOMETER DIMENSIONS in Nanomaterials for Green Energy (Eds. Bharat A. Bhanvase, Vijay B. Pawade, Sanjay J. Dhoble, Shirish H. Sonawane, Muthupandian Ashokkumar), Elsevier, 2018, ISBN: 978-0-12-813731-4.

Describing various types of synthetic methods for preparation of multifunctional inorganic materials in connection with different application, such as: clean envirement, renewable and sustainable energy harvesting, water splitting and hydrogen generation, fuel and solar devices.

All results were orally presented in a frame of Post doc project meeting at Institute of Solid State Physics, University of Latvia

Project progress

April 3, 2018

Particle size effects on the structure and emission of Eu3+:LaPO4 and EuPO4 phosphors.

A new publication within ERDF Post Doc project No. which includes detailed study of particle's size effect on structural and luminescent properties of doped phosphate materials has been published.

Tamara Gavrilović, Jovana Periša, Jelena Papan, Katarina Vuković, Krisjanis Smits, Dragana J. Jovanović, Miroslav D. Dramićanin

Rare-earth doped LaPO4 represents an important class of luminescent nanomaterials, has proven to be suitable for production of efficient down-shifting and up-conversion phosphors. The size effect on emission intensities and decays, structure, and morphology were analyzed by steady-state and time-resolved photoluminescence spectroscopy, X-ray diffraction, scanning and transmission electron spectroscopy, and diffuse reflection spectroscopy. It was found that the particle size has significant influence on the structure and luminescent properties of particles. In particular, with a decrease in particle diameter emission bands broaden due to structural disorder and new emission bands from defect states appear in ultrasmall (2 nm) particles. Judd-Ofelt analysis showed that internal quantum yield of Eu3+ emission is strongly influenced by particle's morphology. Journal of Luminescence

Synthesis, structure and spectroscopic properties of luminescent GdVO4:Dy3+ and DyVO4 particles

Joint publication between researchers from Serbia, Latvia, Italy, Poland and Vietnam has been published.

Dragana J. Jovanović, Andrea Chiappini, Lidia Zur , Tamara V. Gavrilović, Thi Ngoc Lam Tran, Alessandro Chiasera, Anna Lukowiak, Krisjanis Smits, Miroslav D. Dramićanin, Maurizio Ferrari

GdVO4:Dy3+ and DyVO4 samples with particles of different morphology and size were prepared by four synthetic methods: high temperature solid-state, co precipitation, reverse micelle and colloidal. The size effect on the structure, Raman active modes, and photoluminescence emission intensities were analyzed by X-ray diffraction, Raman and photoluminescence spectroscopy, scanning and transmission electron microscopy, and diffuse reflection spectroscopy. Due to strong emission in the NIR spectral region, these luminescent GdVO4:Dy3+ and DyVO4 (bulk)particles incorporated in silica waveguides could find potential application for enhancement of 1.3 µm photoluminescence. Optical Materials

All results were orally presented in a frame of Workshop at Institute of Solid State Physics, University of Latvia.

Project progress

January 9, 2018

We are happy to announce that significant progress has been recently accomplished and four different methods for preparation of phosphors based on phosphate and vanadate host were developed and optimized: high temperature solid-state, co-precipitation, reverse micelle and colloidal route.
Samples with particles of different morphology and size with satisfactory luminescent intensity were obtained. At this moment, some of them incorporated in silica waveguides could find potential application for enhancement of 1.3 μm photoluminescence.

The work investigating luminescent lanthanum nanoparticles was presented at international conference ‘’Spectral shaping for biomedical and energy applications’’, SHIFT 2017, 13-17 November, Tenerife, Spain.

The article, with detailed study of nanoparticle’s size effect on structural and optical properties of doped lanthanum and europium phosphate has been accepted for publication, which can be found online. Also, very proud to report that a joint manuscript between our team and researchers from Italy, Vietnam, Poland and Serbia studying phosphors based on vanadate host has been submitted and accepted for publication.

We will continue our work, hopefully acquiring materials with improved performances, and attractive practical applications.