Formation of metal (nano-)particles in drying latex films by means of a reducing plasma: a route to auto-stratification

Römermann, Heike; Müller, Alexander; Bomhardt, Karolin; Höfft, Oliver; Bellmann, M.P.; Viöl, Wolfgang; Johannsmann, Diethelm

doi:10.1088/1361-6463/aabf2c

Cited by 6 publications

(6 citation statements)

References 31 publications

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“…We recently proved that, in aqueous bimodal blends of large and small polymer particles, a stratified film with predominantly small particles on top can be produced through evaporation driven self-assembly. , Different studies agree that this phenomenon is driven by concentration gradients across the wet film thickness which result in downward forces or cross-interactions that are stronger on large particles and push them down. ,, There have been significant experimental and modeling efforts to understand several aspects of this process such as the effect of temperature gradients and evaporation rates, probing the local microstructure using scattering techniques, exploiting the process for producing particles with a stratified internal composition, and expanding the concept to polymer–polymer and polymer–colloid mixtures . Despite the enormous potential of this directed self-assembly method, applications of stratification in colloidal blends have been scarcely reported and limited to its relevance when controlling the pigment and metal nanoparticle distribution in latex coatings. More importantly, and to our knowledge, the application of stratification to fabricate antibacterial surfaces has not been reported yet.…”

Section: Introductionmentioning

confidence: 96%

“…29,31,32 There have been significant experimental and modeling efforts to understand several aspects of this process such as the effect of temperature gradients 33 and evaporation rates, 34 probing the local microstructure using scattering techniques, 35 exploiting the process for producing particles with a stratified internal composition, 36 and expanding the concept to polymer− polymer and polymer−colloid mixtures. 37 Despite the enormous potential of this directed self-assembly method, applications of stratification in colloidal blends have been scarcely reported and limited to its relevance when controlling the pigment 38 and metal nanoparticle 39 distribution in latex coatings. More importantly, and to our knowledge, the application of stratification to fabricate antibacterial surfaces has not been reported yet.…”

Section: ■ Introductionmentioning

confidence: 99%

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Zinc Oxide Superstructures in Colloidal Polymer Nanocomposite Films: Enhanced Antibacterial Activity through Slow Drying

Dong

Argaiz

et al. 2020

ACS Appl. Polym. Mater.

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Achieving control over the distribution of biocides across the thickness of polymer nanocomposite films is one of the largest challenges to develop efficient antibacterial surfaces. In such applications, it is key to maximize the biocide presence at the film top surface to ensure contact with bacteria. Here, we make use of evaporation driven colloidal self-assembly to control the vertical distribution of biocides in polymer composite films cast from colloidal blends of polymer and zinc oxide (ZnO) nanoparticles. We present a thorough study which shows that the evaporation rate and ZnO volume fraction have a strong impact on the final film architecture and on its wetting and antibacterial properties. For high enough ZnO volume fraction, the ZnO nanoparticles assemble in superstructures on top of the film, which are higher the slower the evaporation rate used, and maximum ZnO surface coverage achieved through slow film drying. At high ZnO volume fraction (ϕ = 0.29), the zone of inhibition diameter against Escherichia coli increases as evaporation rate decreases, with the nanocomposite films having the strongest antibacterial activity when formed at slow evaporation rate. We propose a model for the formation of these colloidal superstructures based on the segregation of large (polymer) and small (ZnO) particles during drying, followed by the assembly of small particles around packed large particles due to differences in the surface charge of the two populations. Our work provides valuable guidelines for the design and assembly of not only antibacterial colloidal films but also a wider range of functional colloidal polymer films including abrasion resistant, self-cleaning, and others.

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Section: Introductionmentioning

confidence: 96%

Section: ■ Introductionmentioning

confidence: 99%

Zinc Oxide Superstructures in Colloidal Polymer Nanocomposite Films: Enhanced Antibacterial Activity through Slow Drying

Dong

Argaiz

et al. 2020

ACS Appl. Polym. Mater.

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“…[ [13][14][15][16][17][18][19][20][21][25][26][27] Plasma as a tool for the redox state alteration of metal compounds and thin films Nanoparticles of various metal compounds (TaC, TaN, Ag, Au, Ir) were mostly synthesized from metal salt solution or directly from the elemental state by the application of plasma technology. This technology also causes reductive changes in thin films of oxidized metals.…”

Section: Referencementioning

confidence: 99%

“…Plasma can also be used for direct synthesis [16][17][18][19][20][21]. For this reason, this study deals with the plasma-assisted modification of the oxidation state of thin metal salt layers, which can be applied from a solution in a relatively straightforward manner.…”

Section: Introductionmentioning

confidence: 99%

Low-Pressure Microwave Plasma Reduction of Iron and Copper Salt Compounds at Low Temperatures for Oxidation State Alteration and Functional Applications

Weber

Scheglov²,

Dörries³

et al. 2023

Materials

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The influence of plasma-reduction treatment on iron and copper compounds at different oxidation states was investigated in this study. For this purpose, reduction experiments were carried out with artificially generated patina on metal sheets and with metal salt crystals of iron(II) sulfate (FeSO4), iron(III) chloride (FeCl3), and copper(II) chloride (CuCl2), as well as with the metal salt thin films of these compounds. All the experiments were carried out under cold low-pressure microwave plasma conditions; the main focus was on plasma reduction at a low pressure in order to evaluate an implementable process in a parylene-coating device. Usually, plasma is used within the parylene-coating process as a supporting tool for adhesion improvement and micro-cleaning efforts. This article offers another useful application for implementing plasma treatment as a reactive medium in order to apply different functionalities by an alteration in the oxidation state. The effect of microwave plasmas on metal surfaces and metal composite materials has been widely studied. In contrast, this work deals with metal salt surfaces generated from a solution and the influence of microwave plasma on metal chlorides and sulfates. While the plasma reduction of metal compounds commonly succeeds with hydrogen-containing plasmas at high temperatures, this study shows a new reduction process that reduces iron salts at temperatures between 30 and 50 °C. A novelty of this study is the alteration in the redox state of the base and noble metal materials within a parylene-coating device with the help of an implemented microwave generator. Another novelty of this study is treating metal salt thin layers for reduction purposes in order to provide the opportunity to include subsequent coating experiments to create parylene metal multilayers. Another new aspect of this study is the adapted reduction process of thin metal salt layers consisting of either noble or base metals, with an air plasma pre-treatment prior to the hydrogen-containing plasma-reduction procedure.

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“…To this end, there have been several experimental studies showing how stratification can be applied to tune properties. Examples of properties include surface wetting, 30 abrasion resistance, 38 antibacterial properties, 39 blocking resistance, 40 and nanopigment 41 and metal nanoparticle 42 distribution. Despite these numerous examples, there is no prior work purposefully applying colloidal stratification mechanisms to optimize adhesive properties.…”

Section: Introductionmentioning

confidence: 99%

Diffusiophoresis-Driven Stratification in Pressure-Sensitive Adhesive Films from Bimodal Waterborne Colloids

Palmer

Kooij

Bakar

et al. 2023

ACS Appl. Polym. Mater.

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The uses of pressure-sensitive adhesives (PSAs) are wide ranging, with applications including labels, tapes, and graphics. To achieve good adhesion, a PSA must exhibit a balance of viscous and elastic properties. Previous research has found that a thin, elastic surface layer on top of a softer, dissipative layer resulted in greater tack adhesion compared with the single layers. Superior properties were achieved through a bilayer obtained via successive depositions, which consume energy and time. To achieve a multilayered structure via a single deposition process, we have stratified mixtures of waterborne colloidal polymer particles with two different sizes: large poly(acrylate) adhesive particles (ca. 660 nm in diameter) and small poly(butyl acrylate) (pBA) particles (ca. 100 nm). We used two types of pBA within the particles: either viscoelastic pBA without an added cross-linker or elastic pBA with a fully cross-linked network. Stratified surface layers of deuterium-labeled pBA particles with thicknesses of at least 1 μm were found via elastic recoil detection and qualitatively verified via the analysis of surface topography. The extent of stratification increased with the evaporation rate; films that were dried slowest exhibited no stratification. This result is consistent with a model of diffusiophoresis. When the elastic, cross-linked pBA particles were stratified at the surface, the tack adhesion properties made a transition from brittle failure to tacky. For pBA without an added cross-linker, all adhesives showed fibrillation during debonding, but the extent of fibrillation increased when the films were stratified. These results demonstrate that the PSA structure can be controlled through the processing conditions to achieve enhanced properties. This research will aid the future development of layered or graded single-deposition PSAs with designed adhesive properties.

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Formation of metal (nano-)particles in drying latex films by means of a reducing plasma: a route to auto-stratification

Cited by 6 publications

References 31 publications

Zinc Oxide Superstructures in Colloidal Polymer Nanocomposite Films: Enhanced Antibacterial Activity through Slow Drying

Zinc Oxide Superstructures in Colloidal Polymer Nanocomposite Films: Enhanced Antibacterial Activity through Slow Drying

Low-Pressure Microwave Plasma Reduction of Iron and Copper Salt Compounds at Low Temperatures for Oxidation State Alteration and Functional Applications

Diffusiophoresis-Driven Stratification in Pressure-Sensitive Adhesive Films from Bimodal Waterborne Colloids

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