In Situ GISAXS Observation and Large Area Homogeneity Study of Slot-Die Printed PS-b-P4VP and PS-b-P4VP/FeCl₃ Thin Films

Abstract

Mesoporous hematite (α-Fe2O3) thin films with high surface-to-volume ratios show great potential as photoelectrodes or electrochemical electrodes in energy conversion and storage. In the present work, with the assistance of an up-scalable slot-die coating technique, locally highly ordered α-Fe2O3 thin films are successfully printed based on the amphiphilic diblock copolymer poly­(styrene-b-4-vinylpyridine) (PS-b-P4VP) as a structure-directing agent. Pure PS-b-P4VP films are printed under the same conditions for comparison. The micellization of the diblock copolymer in solution, the film formation process of the printed thin films, the homogeneity of the dry films in the lateral and vertical direction as well as the morphological and compositional information on the calcined hybrid PS-b-P4VP/FeCl3 thin film are investigated. Because of convection during the solvent evaporation process, a similar dimple-type structure of vertically aligned cylindrical PS domains in a P4VP matrix developed for both printed PS-b-P4VP and hybrid PS-b-P4VP/FeCl3 thin films. The coordination effect between the Fe3+ ions and the vinylpyridine groups significantly affects the attachment ability of the P4VP chains to the silicon substrate. Accordingly, distinct feature sizes and homogeneity in the lateral direction, as well as the thicknesses in the perpendicular direction, are demonstrated in the two printed films. By removing the polymer template from the hybrid PS-b-P4VP/FeCl3 film at high temperature, a locally highly ordered mesoporous α-Fe2O3 film is obtained. Thus, a facile and up-scalable printing technique is presented for producing homogeneous mesoporous α-Fe2O3 thin films.

Mesoporous ordered films via self-assembly: trends and perspectives

“…The interest is still high and some new methods have been developed. One of these is the slot-die printing that has been successfully applied to deposit mesoporous titania 65,66 and hematite 67 (Fig. 8) mesostructured lms.…”

Block Copolymer-Templated, Single-Step Synthesis of Transition Metal Oxide Nanostructures for Sensing Applications

“…Potential drawbacks of directly blending the inorganic precursor with the BCP are limited metal loading and the risk of disturbing the targeted BCP morphology at a too-high precursor content . Additionally, in the case of reactive precursors, metallic species can adversely impact the chain mobility of the BCP by their complexation and chemical cross-linking, which results in defective nanostructures that have a low degree of lateral order (i.e., small-grained morphologies) …”

“…42 An alternative approach to ordered arrays of inorganic nanomaterials consists of blending presynthesized nanoparticles (NPs) with the BCP casting solution; such an approach has been demonstrated for iron oxide, 43,44 Au, 45 PbS, 46 and CdSe 46,47 NPs. Muller-Buschbaum et al explored the synthesis of transition metal oxide nanostructures (TiO 2 , ZnO, SnO 2 , and Fe 2 O 3 ) using the polystyrene-block-poly(ethylene oxide) (PS-b-PEO) 48,49 and polystyrene-block-poly(4-vinylpyridine) (PS-b-P4VP) 50,51 BCPs, monitoring the hybrid-film formation with in situ grazing-incidence small-angle X-ray scattering (GISAXS) measurements. 51 Potential drawbacks of directly blending the inorganic precursor with the BCP are limited metal loading and the risk of disturbing the targeted BCP morphology at a too-high precursor content.…”

“…Muller-Buschbaum et al explored the synthesis of transition metal oxide nanostructures (TiO 2 , ZnO, SnO 2 , and Fe 2 O 3 ) using the polystyrene-block-poly(ethylene oxide) (PS-b-PEO) 48,49 and polystyrene-block-poly(4-vinylpyridine) (PS-b-P4VP) 50,51 BCPs, monitoring the hybrid-film formation with in situ grazing-incidence small-angle X-ray scattering (GISAXS) measurements. 51 Potential drawbacks of directly blending the inorganic precursor with the BCP are limited metal loading and the risk of disturbing the targeted BCP morphology at a too-high precursor content. 52 Additionally, in the case of reactive precursors, metallic species can adversely impact the chain mobility of the BCP by their complexation and chemical crosslinking, which results in defective nanostructures that have a low degree of lateral order (i.e., small-grained morphologies).…”

Strategy to simulate and fit 2D grazing-incidence small-angle X-ray scattering patterns of nanostructured thin films

“…The compatibility of the GISAXS method with a large number of sample environments enables in situ investigations. Systems investigated using GISAXS include, among others, nanostructures from metals or semi-conductors (Renaud et al, 2009), magnetic layers (Wang et al, 2017), nanoporous or nanocomposite films (Doshi et al, 2003;Gibaud et al, 2003;Lee, Park et al, 2005;Li et al, 2018;Alvarez-Fernandez et al, 2020), surface gratings (Soccio et al, 2015), layers of colloids or nanoparticles (Ukleev et al, 2017;Wu et al, 2018;Saxena & Portale, 2020;Engstro ¨m et al, 2020;Qdemat et al, 2020;Schaper et al, 2021), molecular layers (Guennouni et al, 2017), organic electronics from perovskites or polymers (Mu ¨ller-Buschbaum, 2018;Yin et al, 2022), and block copolymer thin films (Smilgies et al, 2002;Mu ¨ller-Buschbaum, 2003;Kim et al, 2004;Mu ¨ller-Buschbaum, Hermsdorf et al, 2004;Cavicchi et al, 2005;Lee, Park et al, 2005;Busch et al, 2007;Paik et al, 2010;Di et al, 2012;Ree, 2014;Mu ¨ller-Buschbaum, 2016;Posselt et al, 2017;Smilgies, 2021). Synchrotron radiation affords high time resolution (sub-second), and time-resolved investigations have elucidated growth and restructuring processes in a number of systems, such as the adsorption of sputtered metals on various substrates (Schwartzkopf et al, 2013), the crosslinking of nanoparticles into superlattices (Maiti et al, 2019), the structural changes in solar cells during storage and operation (Mu ¨ller-Buschbaum, 2014…”