Photocatalytic Activity of TiO2 Coatings Obtained at Room Temperature on a Polymethyl Methacrylate Substrate

Titanium dioxide (TiO2) coatings have a wide range of applications. Anatase exhibits hydrophilic, antimicrobial, and photocatalytic properties for the degradation of organic pollutants or water splitting. The main challenge is to obtain durable anatase nanoparticle coatings on plastic substrates by using straightforward approaches. In the present study, we revealed the preparation of a transparent TiO2 coating on polymethylmethacrylate (PMMA), widely used for organic optical fibres as well as other polymer substrates such as polypropylene (PP), polystyrene (PS), and polycarbonate (PC). The films were spin-coated at room temperature without annealing; therefore, our approach can be used for thermo-sensitive substrates. The deposition was successful due to the use of stripped ultra-small (<4 nm) TiO2 particles. Coatings were studied for the photocatalytic degradation of organic pollutants such as MB, methyl orange (MO), and rhodamine B (RB) under UV light. The TiO2 coating on PMMA degraded over 80% of RB in 300 min under a 365 nm, 100 W mercury lamp, showing a degradation rate constant of 6 × 10−3 min−1. The coatings were stable and showed no significant decrease in degradation activity even after five cycles. © 2022 by the authors. --//-- This is an open access article Iesalnieks M, Eglītis R, Juhna T, Šmits K, Šutka A. "Photocatalytic Activity of TiO2 Coatings Obtained at Room Temperature on a Polymethyl Methacrylate Substrate", Int J Mol Sci. 2022 Oct 26;23(21):12936. doi: 10.3390/ijms232112936 published under the CC BY 4.0 licence.European Union’s Horizon 2020 FET Open program under Grant Agreement No. 899528; Institute of Solid-State Physics, University of Latvia has received funding from the European Union's Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-Teaming Phase 2 under grant agreement No. 739508, project CAMART2

Permanent photodoping of plasmonic gallium-ZnO nanocrystals

This work was supported by the Latvian Council of Science in the framework of FLPP (Plasmonic oxide quantum dots for energy saving smart windows, lzp-2018/1-0187). Tanel Käämbre acknowledges financial support for the XPS instrumentation maintenance from the Estonian Centre of Excellence in Research project “Advanced materials and high- technology devices for sustainable energetics, sensorics and nanoelectronics” (TK141).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 doped ZnO nanocrystals can be promoted by photodoping. Unexpectedly, the electrons from photodoping are stable in the open air for months.Latvian Council of Science lzp-2018/1-0187; Estonian Centre of Excellence in Research TK141; Institute of Solid State Physics, University of Latvia as the Center of Excellence has received funding from the European Union’s Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART

Identifying iron-bearing nanoparticle precursor for thermal transformation into the highly active hematite photo-fenton catalyst

Funding: This reseach was funded by the European Regional Development Fund within the Activity 1.1.1.2 “Post-doctoral Research Aid” of the Specific Aid Objective 1.1.1 “To increase the research and innovative capacity of scientific institutions of Latvia and the ability to attract external financing, investing in human resources and infrastructure” of the Operational Programme “Growth and Employment” (No. 1.1.1.2/VIAA/1/16/157).The hematite photo-Fenton catalysis has attracted increasing attention because it offers strong oxidation of organic pollutants under visible light at neutral pH. In the present work, aqueous synthesis of hematite photo-Fenton catalysts with high activity is demonstrated. We compare photo-Fenton activity for hematite obtained by hydrolyzation at 60◦C or by a thermally induced transformation from iron-bearing nanoparticles, such as amorphous iron oxyhydroxide or goethite. A link between their structure and visible light photo-Fenton reactivity is established. The highest activity was observed for hematite obtained from goethite nanowires due to oblong platelet-like structure, high surface area and the presence of nanopores.European Regional Development Fund 1.1.1.2/VIAA/1/16/157; Institute of Solid State Physics, University of Latvia as the Center of Excellence has received funding from the European Union’s Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART

Pašattīroši audumi: kas tie ir un kāpēc tādi nepieciešami?

Pašattīroši audumi ir tekstilmateriāli, kuriem piemīt  spēja  ārēju vides faktoru iedarbībā atbrīvot savu virsmu no dažādiem piesārņojumiem. Šādi audumi ļauj samazināt ūdens un enerģijas patēriņu, kas saistīts ar drēbju mazgāšanu, samazināt infekciju risku, pateicoties to biocīdām īpašībām, kā arī pasargā cilvēkus no UV starojuma. Papildus tam šādus audumus arī būtu grūtāk saslapināt; tas mūsdienu mitrajā klimatā samazinātu diskomfortu no salijušām drēbēm. Šādus efektus pašattīroši audumi iegūtu ar tādiem mehānismiem kā fotokatalīze un superhidrofobitāte. Lai audumi iegūtu augstāk minētās īpašības, piemērotākie ir ZnO un TiO2 nanodaļiņu veidotie pārklājumi. Savukārt pārklājumu ieguvei jāizmanto sola-gēla metode, kas sniedz iespēju izveidot homogēnus pārklājumus pie temperatūrām, kuras iztur organiskas dabas materiāli. Kopš 2011. gada ar šādu audumu izstrādi ir nodarbojies Rīgas Tehniskās universitātes Dizaina tehnoloģiju institūts. Kopš 2016. gada ar šādiem pārklājumiem nodarbojas arī Rīgas Tehniskās universitātes Silikātu materiālu institūtā. Izmantojot savas gadu desmitu laikā iegūtās zināšanas sola-gēla tehnoloģijā un nanostrukturētu pārklājumu ieguvē, sekmīgi uzsākti pētījumi rūpnieciski izmantojamu tehnoloģiju izstrādei kokvilnas audumiem.Self-Cleaning Fabrics: What Are They and How Are They Used?Self-cleaning fabrics are textile materials, which under the influence of various external environmental factors have the ability to rid their surface from various contaminants. Such fabrics make it possible to reduce water and energy consumption associated with washing clothes, to reduce the risk of infections due to their biocidal properties, and to protect people from UV radiation. In addition, such fabrics would also be more difficult to wet. This would reduce the possibility of wet clothes in damp climates. Such effects by self-cleaning fabrics could be achieved through mechanisms of photocatalysis and superhydrophobicity. To develop textiles with above mentioned properties, the most suitable approach is the deposition of coatings formed by ZnO and TiO2 nanoparticles. In turn, the sol-gel method should be used to obtain coatings. This would make it possible to create homogeneous coatings at temperatures that organic materials can withstand. Institute of Design Technologies, Riga Technical University, has been working on the development of such fabrics since 2011. The research in the field of such coatings at the Institute of Silicate Materials, Riga Technical University, has been performed since 2016. Thanks to decades long research in sol-gel technology and nanostructured coatings, the development of commercially available technologies for cotton fabrics has been successfully launched at the Institute of Silicate Materials.Keywords: self-cleaning fabrics, sol-gel method, TiO2, Zn