Within the ERC project 'NANO-INSITU', Work package 1 dealt with the development of in-situ TEM technology for Liquid TEM, and was mainly owned by PhD student Tom Welling. Although the research was much aided by technological developments conducted at the in-situ EM companies, great challenges still needed to be overcome to prevent charging effects from the electron beam, both on the thin SiN windows containing the thin fluid, and in the fluid itself. By choosing low-dose electron beam conditions, and a solvent with a high dielectric permittivity (glycerol carbonate), we have been the first to achieve self-diffusion rates of titania and gold nanoparticles in liquids that follow the theoretical expectation for Brownian motion. (T.A.J. Welling et al., Particle and Particle Systems Characterization 37 (2020) 2000003).Furthermore, so-called rattle particles were studied which consist of a moveable core inside a larger silica shell. The mobility of the core nanoparticles inside the liquid-filled shell was manipulated by changing the ion concentration in the liquid, and by applying AC electric fields of different frequencies. This enables spectacular control over the motion of nanoparticles in liquid confinement.[T.A.J. Welling et al., ACS Nano 15 (2021) 11137-11149]
Work package 2 concerned the in-situ study of cation exchange reactions in heterogeneous nanocrystals. First, much time was invested in the synthesis of large PbSe nanocubes and CdS nanorods, which are very suitable to perform cation exchange on. Investigations of in-situ cation exchange in liquid were conducted, with much focus on mitigating the effect of secondary nucleation of metal nanoparticles from metal precursors. Also the wet chemical etching of silica nanoparticles was investigated, which required extensive research into low-dose imaging conditions, and which was published in a methods-type paper.[A. Grau-Carbonell, ACS Applied Nano Materials 4 (2021) 1136-1148]
Work package 3 on the in-situ study on self-assembly of nanoparticles was owned by PhD student Dnyaneshwar Gavhane, who intensively investigated the assembly and transformations of chalcogenide nanosystems such as CoSe2, NiSe2, and MoSe2. Already spectacular findings were recorded during in-situ TEM experiments, showing a successive transformation from orthorhombic CoSe2 to cubic CoSe2 to hexagonal CoSe to tetragonal CoSe.[D.S. Gavhane et al., npj 2D Materials and Applications 5 (2021) 24] Furthermore, the in-situ horizontal or vertical growth of the 2D material WS2 was deciphered in detail and published in the high-ranking journal Advanced Functional Materials.[D.S. Gavhane, et al., Adv. Funct. Mater. 32 (2022) 202106450] This paper also featured on the cover of the journal.
Work package 4 on the in-situ study of reduction, oxidation, and hydration of metal oxides was mainly owned by PhD student Xiaodan Chen. She investigated the thermal stability of anatase and brookite TiO2 nanorods [X.D. Chen et al., ACS Applied Nano Materials 5 (2022) 1600-1606], and witnessed the transformation of Co3O4 nanoparticles to CoO [X.D. Chen et al., J. Mater. Chem. C 9 (2021) 5662-5675], and massive temperature-induced delamination of MoO3 nanocrystals into MoO2 nanoflakes. A paper with density functional theory (DFT) calculations on the thermal stability of transition metal oxides (TMOs) was published in a high-ranking journal [H. van Gog et al., npj 2D Materials and Applications 3 (2019) 18].
