Publications by Reinis Ignatans

Nb, Ta and Hf-The tri-dopant tournament for the enhancement of TiO2 photochromism

TiO2 quantum dot (QD) size nanoparticle colloids have shown tremendous photochromic response. Here we show that the of the photochromic response of TiO2 QDs can be further enhanced by doping. Our synthesis approach allows to reach high nominal doping level ...

ELSEVIER SCIENCE SA2023

Latent Mechanisms of Polarization Switching from In Situ Electron Microscopy Observations

Vasiliki Tileli, Reinis Ignatans

In situ scanning transmission electron microscopy enables observation of the domain dynamics in ferroelectric materials as a function of externally applied bias and temperature. The resultant data sets contain a wealth of information on polarization switch ...

WILEY-V C H VERLAG GMBH2022

Decoding the Mechanisms of Phase Transitions from In Situ Microscopy Observations

Vasiliki Tileli, Reinis Ignatans

Analysis of the temperature- and stimulus-dependent imaging data toward elucidation of the physical transformations is an ubiquitous problem in multiple fields. Here, temperature-induced phase transition in BaTiO3 is explored using the machine learning ana ...

WILEY-V C H VERLAG GMBH2022

Ferroelectric Effects Probed by in situ Transmission Electron Microscopy

Reinis Ignatans

Ferroelectric perovskite oxides are widely used in sensors, actuators and optical modulators and, at the same time, they show promise for implementation in future applications such as energy storage, memory and cooling devices. At the infancy of the discov ...

EPFL2022

A comprehensive study of structure and properties of nanocrystalline zinc peroxide

Reinis Ignatans

Nanocrystalline zinc peroxide (nano-ZnO2) was synthesized through a hydrothermal process and comprehensively studied using several experimental techniques. Its crystal structure was characterized by X-ray diffraction, and the average crystallite size of 22 ...

PERGAMON-ELSEVIER SCIENCE LTD2022

Challenges and Applications to Operando and In Situ TEM Imaging and Spectroscopic Capabilities in a Cryogenic Temperature Range

Martial Duchamp, Vasiliki Tileli, Reinis Ignatans

In this Account, we describe the challenges and promising applications of transmission electron microscopy (TEM) imaging and spectroscopy at cryogenic temperatures. Our work focuses on two areas of application: the delay of electron-beam-induced degradatio ...

AMER CHEMICAL SOC2021

Individual Barkhausen Pulses of Ferroelastic Nanodomains

Dragan Damjanovic, Vasiliki Tileli, Reinis Ignatans

Ferroelectric materials, upon electric field biasing, display polarization discontinuities known as Barkhausen jumps, a subclass of a more general phenomenon known as crackling noise. Herein, we follow at the nanoscale the motion of 90 degree needle domain ...

2021

Strong, Rapid, and Reversible Photochromic Response of Nb Doped TiO2 Nanocrystal Colloids in Hole Scavenging Media

Reinis Ignatans

Understanding photochromicity is essential for developing new means of modulating the optical properties and optical response of materials. Here, we report on the synthesis and exciting new photochromic behavior of NV doped TiO2 nanoparticle colloids (NCs) ...

AMER CHEMICAL SOC2020

Structured nanoscale metallic glass fibres with extreme aspect ratios

Giuseppe Schiavone, Güven Kurtuldu, Inès Richard, Stéphanie Lacour, Grégoire Courtine, Dang Tùng Nguyen, Fabien Sorin, Wei Yan, Yunpeng Qu, Vasiliki Tileli, Nicholas David James, Jordan Squair, Reinis Ignatans

Micro- and nanoscale metallic glasses offer exciting opportunities for both fundamental research and applications in healthcare, micro-engineering, optics and electronics. The scientific and technological challenges associated with the fabrication and util ...

Nature Publishing Group2020

Local hard and soft pinning of 180° domain walls in BaTiO3 probed by in situ transmission electron microscopy

Dragan Damjanovic, Vasiliki Tileli, Reinis Ignatans

2020

Permanent photodoping of plasmonic gallium-ZnO nanocrystals

Reinis Ignatans

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 dope ...

ROYAL SOC CHEMISTRY2020

Local structural investigation of hafnia-zirconia polymorphs in powders and thin films by X-ray absorption spectroscopy

Reinis Ignatans

Despite increasing attention for the recently found ferro- and antiferroelectric properties, the polymorphism in hafnia- and zirconia-based thin films is still not sufficiently understood. In the present work, we show that it is important to have a good qu ...

PERGAMON-ELSEVIER SCIENCE LTD2019

Stronger Reductive Environment in Solvothermal Synthesis Leads to Improved Ga Doping Efficiency in ZnO Nanocrystals and Enhanced Plasmonic Absorption

Reinis Ignatans

The key parameter for degenerated semiconductor oxide plasmonic nanocrystals is the doping level. Hydrothermal and solvothermal approaches are considered to be less effective toward achieving high concentration of aliovalent donor dopants in a host oxide w ...

Wiley-VCH Verlag2019

The Effect of Surface Reconstruction on the Oxygen Reduction Reaction Properties of LaMnO3

Vasiliki Tileli, Reinis Ignatans

Perovskites have been widely studied for electrocatalysis due to the exceptional activity they exhibit for surface-mediated redox reactions. To date, descriptors based on density functional theory calculations or experimental measurements have assumed a bu ...

AMER CHEMICAL SOC2019

Magnetic and optical properties in degenerated transition metal and Ga co-substituted ZnO nanocrystals

Reinis Ignatans

In order to study the influence of itinerant electrons on magnetic properties of transition metal substituted ZnO nanocrystals, nanopowders containing different amounts of Ga and fixed amounts of Fe, Ni and Mn ions were synthesized. The ions of different t ...

2019

Switchable Light Reflectance in Dilute Magneto-Optical Colloids Based on Nickel Ferrite Nanowires

Reinis Ignatans

2018

Yttrium-doped hematite photoanodes for solar water splitting: Photoelectrochemical and electronic properties

Reinis Ignatans

2018