Permanent photodoping of plasmonic gallium-ZnO nanocrystals

This work was supported by the Latvian Council of Science in the framework of FLPP (Plasmonic oxide quantum dots for energy saving smart windows, lzp-2018/1-0187). Tanel Käämbre acknowledges financial support for the XPS instrumentation maintenance from the Estonian Centre of Excellence in Research project “Advanced materials and high- technology devices for sustainable energetics, sensorics and nanoelectronics” (TK141).Donor dopants in oxide semiconductors are compensated not only by valuable electrons but also by other point defects, leading to a decrease in electric conductivity and infrared absorption. We demonstrate that the electron compensation mechanism in Ga doped ZnO nanocrystals can be promoted by photodoping. Unexpectedly, the electrons from photodoping are stable in the open air for months.Latvian Council of Science lzp-2018/1-0187; Estonian Centre of Excellence in Research TK141; Institute of Solid State Physics, University of Latvia as the Center of Excellence has received funding from the European Union’s Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART

Amorphous Calcium Phosphate and Amorphous Calcium Phosphate Carboxylate: Synthesis and Characterization

The authors acknowledge financial support from the European Union’s Horizon 2020 Research and Innovation Program under grant agreement no. 857287 and Baltic Research Programme Project No. EEA-RESEARCH-85 “Waste-to-resource: eggshells as a source for next generation biomaterials for bone regeneration (EGGSHELL)” under the EEA Grant of Iceland, Liechtenstein and Norway No. EEZ/BPP/VIAA/2021/1. Institute of Solid State Physics, University of Latvia, received funding from the European Union’s Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART. 2Amorphous calcium phosphate (ACP) is the first solid phase precipitated from a supersaturated calcium phosphate solution. Naturally, ACP is formed during the initial stages of biomineralization and stabilized by an organic compound. Carboxylic groups containing organic compounds are known to regulate the nucleation and crystallization of hydroxyapatite. Therefore, from a biomimetic point of view, the synthesis of carboxylate ions containing ACP (ACPC) is valuable. Usually, ACP is synthesized with fewer steps than ACPC. The precipitation reaction of ACP is rapid and influenced by pH, temperature, precursor concentration, stirring conditions, and reaction time. Due to phosphates triprotic nature, controlling pH in a multistep approach becomes tedious. Here, we developed a new ACP and ACPC synthesis approach and thoroughly characterized the obtained materials. Results from vibration spectroscopy, nuclear magnetic resonance (NMR), X-ray photoelectron spectroscopy (XPS), true density, specific surface area, and ion release studies have shown a difference in the physiochemical properties of the ACP and ACPC. Additionally, the effect of a carboxylic ion type on the physiochemical properties of ACPC was characterized. All of the ACPs and ACPCs were synthesized in sterile conditions, and in vitro analysis was performed using MC-3T3E1 cells, revealing the cytocompatibility of the synthesized ACPs and ACPCs, of which the ACPC synthesized with citrate showed the highest cell viability. © 2023 The Authors. Published by American Chemical Society --//-- https://pubs.acs.org/doi/10.1021/acsomega.3c00796. Published under the CC BY 4.0 licence.EEA Grant of Iceland EEZ/BPP/VIAA/2021/1; Horizon 2020 Framework Programme 857287, EEA-RESEARCH-85; institute of Solid State Physics, University of Latvia, received funding from the European Union’s Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART.

Latvijas Universitātes vēsturiskais studentu karceris: video

The University of Latvia has 19th-century historical witness regarding the daily life of students during studies - the historical student solitary confinement cell. The origins of the student solitary confinement cell are found in medieval Germany, when universities were entitled to turn students into cells for the misdeeds during the studies. The idea was realized in the 19th century, which coincided with the time when German academic influence spread in the Baltics. During the occupation of the USSR, this history phenomenon was forgotten or distorted, but it is now rehabilitated. The Museum of the University of Latvia has filmed a video with subtitles in English about the student solitary confinement cell, which introduces everyone with this forgotten history page in the history of Latvia's higher education.Latvijas Universitātē atrodās 19. gs. vēstures liecinieks par studentu ikdienas dzīvi studiju laikā - vēsturiskais Studentu karceris. Studentu karcera aizsākumi meklējami viduslaiku Vācijā, kad universitātēm bija tiesības ieslēgt studentus cellēs par izdarītajiem pārpākumiem studiju laikā. Ideja realizējās 19. gs., kas sakrita ar laiku, kad vācu akadēmiskā ietekme izplatījās arī Baltijā. PSRS okupācijas laikā šis vēstures fenomens tika aizmirsts vai sagrozīts, taču tagad tas ir reabilitēts. LU Muzejs ar LU Akadēmisko apgādu ir izdevis bukletu par LU vēsturisko Studentu karceri, kas ļauj iepazīties ikvienam interesentam par šo aizmirsto vēstures lappusi Latvijas augstākās izglītības vēsturē.Baltische-Deutsches Hochsculkanto

Investigation of TiO2 Ceramic Surface Conductivity Using Conductive Atomic Force Microscopy

Dense TiO2 (rutile) ceramic samples were prepared by sintering compacts of titanium dioxide anatase powder at 1500 °C for 5h. Sintered samples were polished and annealed in vacuum at 1000 °C for 1h. Structural properties of the samples were studied by X-ray diffraction, polarized light and scanning electron microscopy. The surface topography and local electrical conductivity of the samples were investigated by atomic force microscopy technique under atmospheric conditions. Enhanced electrical conductivity was observed at grain boundaries while the polished, vacuum annealed grains surface showed non-homogeneous conductivity

Dissolution-precipitation synthesis and cold sintering of mussel shells-derived hydroxyapatite and hydroxyapatite/chitosan composites for bone tissue engineering

In the present work, seafood by-products and derivates were exploited as raw materials to produce nanocrystalline calcium phosphates-based composites in light of the rising demand for waste recovery and valorisation. Mussel shells were transformed into hydroxyapatite by dissolution-precipitation synthesis at 45 °C, whereas chitosan from shrimp shells was introduced as a reinforcing biopolymer to produce hydroxyapatite/chitosan composites. The synthesised hydroxyapatite and hydroxyapatite/chitosan composite powders were cold sintered at room temperature under 1 GPa pressure for 10 min. The materials were consolidated up to ∼90% relative density and characterized mechanically. By increasing the polymer content up to 10 wt%, the flexural strength of the sintered pellets increases from ∼45 MPa to ∼57 MPa while the hardness decreases from ∼1.1 GPa to ∼0.8 GPa, thus better addressing the mechanical properties of cortical bone. Furthermore, hydroxyapatite/chitosan composites were proven to be bioactive, this demonstrating their potential use in bone tissue engineering applications

The Influence of Extrusion Process on the Microstructure of Ceramic Obtained

Titanium dioxide ceramic powder with the average particle size of 200 nm was used for the preparation of ceramic rods. Industrial scale equipment was used to perform the preparation of extrusion mass and extrusion. Microstructure of samples before sintering and after sintering in different temperatures was investigated. In current research sintering temperatures from 1100 °C up to 1450 °C was used. Results obtained showed that the microstructure of the samples after sintering depends on the mass preparation and extrusion parameters. At low temperatures sintered samples exhibit different microstructure and porosity in the inner and outer part of the samples. Scanning electron microscopy, high temperature microscope and X-ray diffraction was used for the characterisation of the samples obtained. The changes in density and microstructure after sintering was investigated and related to the extrusion process parameters

Effect of Shaping Method and Heat Treatment on Microstructure and Thermoelectric Properties of Titanium Dioxide

Effect of shaping method and heat treatment on microstructure and thermoelectric properties of titanium dioxid

The Influence of Shaping Technique and Heat Treatment Conditions on the Microstructure and Thermoelectric Properties of TiO2 Ceramic

It is well known that shaping technique can considerably affect various properties of ceramic materials. In the field of thermoelectrics, microstructure is one of the factors that has a great influence on materials thermoelectric properties. Although nowadays various advanced shaping techniques such as spark plasma sintering and hot presing have been widely used for preparation of thermoelectric materials, in the present work the effect of different convential shaping techniques: cold isostatic pressing and extrusion, as well as heat treatment conditions, on the microstructure and thermoelecric properties of TiO2 ceramic have been studied