Browsing by Author "Nguyen, Hoang M."

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Bio‐Templated Silver Nanopatterns for Photothermal and Antifogging Coatings
(2024-02-23) De, Swarnalok; Nguyen, Hoang M.; Zou, Fangxin; Basarir, Fevzihan; Mousavi, Maryam; Mäkinen, Kristiina; Kostiainen, Mauri A.; Vapaavuori, Jaana
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Transparent photothermal coatings based on plasmonic noble metals often face a trade-off between achieved temperatures and transmittances. This challenge arises from the fact that plasmonic nanoparticles (NPs), which rely on their size and structures, selectively absorb light of various wavelengths and convert it into heat. In the cases of randomly arranged plasmonic NPs, absorbances are predominantly in the visible range, leading to lowered transmittances. In this work, the self-assembly behavior of a biotemplate containing flexible potato virus A (PVA) is used to produce network-like surface patterns with controllable intermittent vacancies. These templates effectively anchor silver nanoparticles (AgNPs), forming dense arrays of plasmonic hotspots interspersed with vacant regions. With this approach, a temperature increase of 21 °C above ambient temperature under 1-sun radiation is achieved while maintaining a visible light transmittance as high as 78% measured at 550 nm wavelength. The PVA biotemplated AgNPs show excellent potential as antifogging coating, exhibiting 2–3 times faster defogging rates compared to uncoated samples in both indoor and outdoor conditions. Overall, a platform is presented for biotemplating metal NPs, the development of long-range surface patterns with controlled vacancies, and the demonstration of transparent photothermal activity with an antifogging application.
Controlling the Self-Assembly of Hierarchical PS-b-P4VP Structures Prepared by Dip-Coating and Emulsion Breath Figure Techniques
(2023-04-04) Nguyen, Hoang M.; Mader, Ariane; De, Swarnalok; Basarir, Fevzihan; Vapaavuori, Jaana
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
The breath figure (BF) method is a common laboratory-scale pathway for fabricating porous structures. The emulsion BF approach, one of the BF variations, has attracted increasing attention since it bypasses the high humidity requirement, which is characteristic for the conventional BF method. In this paper, we used the emulsion BF technique with PS-b-P4VP block copolymer (BCP) and SiO2 nanoparticles (NPs) as the stabilizers for water droplets. We combined this with the dip-coating technique to obtain a hierarchical structure consisting of BF pores and BCP nanodomains. By altering the dip-coating speeds and the NPs’ surface wetting properties and size, the average diameters of BF pores could be controlled. Notably, we were able to achieve both nano and microscale BF pores in the network. The effect of NPs for stabilization and dip-coating parameters on BF pores and BCP nanodomains formation was established, extending the comprehension of this underdeveloped subject.
Potato virus A particles – A versatile material for self-assembled nanopatterned surfaces
(2023-01) De, Swarnalok; Nguyen, Hoang M.; Liljeström, Ville; Mäkinen, Kristiina; Kostiainen, Mauri; Vapaavuori, Jaana
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Potato virus A (PVA) is a plant-infecting RNA virus that produces flexible particles with a high aspect ratio. PVA has been investigated extensively for its infection biology, however, its potential to serve as a nanopatterning platform remains unexplored. Here, we study the liquid crystal and interfacial self-assembly behavior of PVA particles. Furthermore, we generate nanopatterned surfaces using self-assembled PVA particles through three different coating techniques: drop-casting, drop-top deposition and flow-coating. The liquid crystal phase of PVA solution visualized by polarized optical microscopy revealed a chiral nematic phase in water, while in pH 8 buffer it produced a nematic phase. This allowed us to produce thin films with either randomly or anisotropically oriented cylindrical nanopatterns using drop-top and flow-coating methods. Overall, this study explores the self-assembly process of PVA in different conditions, establishing a starting point for PVA self-assembly research and contributing a virus-assisted fabrication technique for nanopatterned surfaces.
Thin films of self-assembled materials by dip-coating technique
(2023) Nguyen, Hoang M.
School of Chemical Engineering | Doctoral dissertation (article-based)
Self-assembly processes, which manifest in various natural phenomena, involve the constituents merging to construct intricate and well-structured material systems. Motivated by nature's elegance, synthetic self-assembled materials have experienced remarkable progress over the past two decades, facilitating the creation of structures spanning diverse length scales, ranging from the molecular level to larger macromolecular systems and microscale particles. An essential determinant for the practical application of self-assembled materials lies in the ability to fine-tune their self-assembly behavior, within which various complex physicochemical processes can take place. Among the techniques for depositing self-assembled thin films, dip-coating emerges as a particularly promising candidate. It shares the simplicity and expediency of drop-casting and spin-coating, while retaining the exceptional control over film thickness characteristic for layer-by-layer deposition. Moreover, it offers unrestricted substrate shape and size as well as permits the minimization of solution waste. Dip-coating, therefore, appears as an ideal approach for generating self-assembled thin films. Nevertheless, research efforts in this area remain limited, and a thorough comprehension of the interplay between dip-coating parameters and self-assembly behavior remains elusive. This thesis attempts to fill this knowledge gap by expanding the scope of materials combining dip-coating and self-assembly process. The thesis begins with an extensive review of the dip-coating technique, followed by distinct chapters exploring the self-assembly of various materials, including block copolymers, breath figure, and virus nanoparticles. Within these chapters, the thesis strives to establish systematic relationship between dip-coating parameter and the behavior of the specific material, thereby providing valuable insights that can steer future research in this field.
Understanding nanodomain morphology formation in dip-coated PS-b-PEO thin films
(2021-09-07) Nguyen, Hoang M.; Mader, Ariane; De, Swarnalok; Vapaavuori, Jaana
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Block copolymer (BCP) thin films prepared by dip-coating are increasingly investigated, owing to the many promising application areas, the facility, and the industrial scalability of this technique. Yet, the effect of different dip-coating parameters on BCP nanostructure formation is still underdeveloped and the results of previous literature are limited to a few block copolymers. Here, we study the effect of the withdrawal rate and solvent selectivity on the morphology evolution of dip-coated polystyrene-b-poly(ethylene oxide) thin films by applying a wide range of dip-coating speeds and altering the volume ratio of the tetrahydrofuran-water solvent system. The dip-coated films were characterized using atomic force microscopy and ellipsometry. The nanodomain morphology, its feature sizes, its spanning, and the degree of ordering were investigated with regard to different dip-coating parameters. Notably, we have obtained a hexagonally packed BCP pattern with long-range order without the need for post-annealing processes. Overall, a solid understanding of the parameters affecting the formed surface patterns and their interplay was attained and explained, extending the knowledge of this field to more materials.