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New nanosized upconversion oxide materials (2017 - 2020)
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Project leader Tamara Gavrilovic

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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

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.