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

Mechanical reinforcement of electrospun poly(vinyl alcohol) by α‐FeOOH nanowires

The authors kindly acknowledge the financial support of the Estonian Research Council for the post-doctoral research grants of personal research funding in projects PUT1096 and PUTJD578 as well as Institutional Research Funding Projects, IUT20-17, and IUT23-7.We report the mechanical performance of α‐FeOOH nanowire reinforced poly(vinyl alcohol) (PVA) composite nanofiber mat, fabricated using straightforward aqueous processing methods. Goethite (α‐FeOOH) nanocrystals have a high elastic modulus and –OH rich surface, ensuring strong interactions with hydrophilic polymers and effective reinforcement. Needle‐less electrospinning resulted in alignment of the nanowires along fibre axis, as confirmed by transmittance electron microscopy studies. Produced composite PVA nanofibers containing 10 wt% goethite nanoparticles exhibited an outstanding fivefold increase in Young's modulus and 2.5‐fold improvement of tensile strength compared to mats of neat PVA. The addition of α‐FeOOH had a significant influence on glass transition temperature indicating formation of interphase regions around nanowire inclusions. Observed properties are explained by nanowire grafting in the precursor solution, extensive interactions between the adsorbed PVA chains and the matrix and percolation of interphase regions at 10 wt% α‐FeOOH.Estonian Research Council PUT1096 and PUTJD578; Institutional Research Funding Projects, IUT20-17, and IUT23-7; 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

Hybrid Tribo-Piezo-Electric Nanogenerator with Unprecedented Performance Based on Ferroelectric Composite Contacting Layers

This research was supported by the European Regional Development Fund within the project ‘‘Hybrid energy harvesting systems’’ 1.1.1.1./16/A/013.It was recently reported that more efficient triboelectric nanogenerator (TENG)-like devices can be prepared using inversely polarized ferroelectric films made of same material as the contacting layers. In the present work, a clear correlation between the piezoelectric response of inversely polarized ferroelectric PVDF/BaTiO3 nanocomposite films and the performance of the TENG-like device based on these films is demonstrated. This observation is explained by magnified electrostatic induction that is driven by piezoelectric charges and ferroelectric properties of these films. A double capacitor model is proposed that effectively portrays the interactions between ferroelectric layers during contact-separation and subsequent charge redistributions in the external circuit. The new understanding has allowed the result of 3-fold higher open circuit voltages (2.7 kV from 5 cm2) as compared to that of a state of the art TENG. Furthermore, findings uncover the potential for vast improvement in the field of nanogenerators for mechanical energy harvesting as a significantly better piezoelectric performance of flexible nanogenerators has been reported elsewhere.ERDF 1.1.1.1./16/A/013; 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

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

ORR activity and stability of Co-N/C catalysts based on silicon carbide derived carbon and the impact of loading in acidic media

This work was supported by the EU through the European Regional Development Fund under projects TK141 “Advanced materials and high-technology devices for energy recuperation systems” (2014-2020.4.01.15-0011), NAMUR ”Nanomaterials - research and applications” (3.2.0304.12-0397) and by the Estonian institutional research grant No. IUT20-13.A simple and facile synthesis method was used to produce two Co-N/C type oxygen reduction reaction (ORR) catalysts. The materials were initially characterized by utilizing a variety of physical methods. Most importantly, the XPS analysis revealed high amounts of pyridinic nitrogen and Co-Nx species in the case of both studied Co-N/C catalysts. The electrochemical characterization showed that both of the synthesized Co-N/C catalysts have a high ORR activity in acidic media, displaying a half-wave potential of 0.70 V vs RHE. Additionally, the effect of varying the catalyst loading was studied and it was found that increasing the catalyst loading from 0.1 to 1.8 mg cm−2 significantly improved the ORR activity and the electron transfer number. Finally, several catalysts were subjected to a week-long stability test in order to establish their activity degradation rates. It was found that increased degradation rates of the Co-N/C catalysts were established at decreased catalyst loadings.European Commission; ERDF 2014-2020.4.01.15-0011,TK141, NAMUR 3.2.0304.12-0397; Estonian institutional research grant No. IUT20-13; 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

Event organization website

Kvalifikācijas darbā izstrādāta un aprakstīta pasākumu organizēšanas vietne. Vietnē lietotājs var izveidot pasākuma aprakstu, ar mērķi informēt pasākuma dalībniekus, vai piesaistītu potenciālos dalībniekus. Pastāv divi pasākuma veidi – publisks, kur jebkuram reģistrētam lietotājam ir tiesības kļūt par organizatoru, tādējādi iegūstot tiesības mainīt pasākuma informāciju, un privāts pasākums, kurā lietotāji nevar iegūt tiesības mainīt pasākuma informāciju. Lietotājs var reģistrēties izmantojot vietnes reģistrāciju, vai arī pieslēgties izmantojot facebook vai draugiem.lv sociālo tīklu profilu. Nereģistrētam lietotājam ir tiesības tikai apskatīt pasākuma informāciju. Vietnes operatoriem ir pieejams operatora panelis, no kura var administrēt vietnes saturu un lietotājus.In this qualification work an event organization system is developed and documented. User can create event description, with goal to inform events participiants or atract potential participiants. There are two types of events – public event where registered user can become organizator, thereby gaining access to change events description, and private event, where user can't gain access to changing events description. User can register using system registration or login usin facebook or draugiem.lv social network profile. Unregistered user can only view event description. System administrators have access to administrator panel from where they can administrate system content and users

Luminescense of zirconia nanocrystals

Anotācija Veikti cirkonija dioksīds (ZrO2) nanokristālu luminiscences pētījumi ar laika izšķirtspēju. Pašvielas defektu luminiscences ierosmes diapazons ir plašs aizliegtās zonas apgabals, kā arī zona-zona pārejas, pie tam ierosmes fotonu enerģijas izmaiņai seko nepārtraukta luminiscences joslas maiņa. Pašvielas defektu luminiscences centri veido kvazinepārtrauktu enerģētisko spektru aizliegtajā zonā . Minētie centri saistīti ar skābekļa vakanču radīto kristāliskā režģa perturbāciju. Pirmo reizi novērota elektronu kūļa inducēta absorbcija ZrO2:Y2O3 monokristālā. Pētīts Eu3+ luminiscences spektrālais sadalījums atkarībā no Eu koncentrācijas ZrO2 nanokristālos. Atrasts, ka palielinot Eu3+ koncentrāciju, tas darbojas kā ZrO2 tetragonālās un iespējams arī kubiskās fāzes stabilizators. Veiktie pētījumi dod jaunas ziņas par luminiscenci ZrO2 nanokristālos un iegūtos rezultātus iespējams izmantot luminiscento sensoru izveidei skābekļa koncentrācijas noteikšanai.Abstract The study of time-resolved luminescence of zirconia (ZrO2) was carried out. It is found that the excitation of intrinsic defect luminescence band is possible within band gap and also band – to- band excitation is possible. The continuous shift of luminescence band position on excitation photon energy was observed. This effect was suggested to be due to the quasi-continuous energy spectrum in band gap. The transient absorption measurements for ZrO2:Y2O3 single crystal was carried out for first time. The Eu3+ luminescence spectral dependence on activators concentration in ZrO2 nanocrystlas is shown. It is found that with increase of Eu concentration the phase transition occurs and tetragonal and even cubic phase is stabilized. These new results about zirconia nanocrystal luminescence properties gives additional information about physical processes in zirconia and is possible to use in futher investigations for applications in oxygen sensors

DBpedia system research and creation of the Latvian version

Mūsdienās praktiski visa informācija atrodas tīmeklī un tīmeklis ir arī galvenais informācijas avots. Gan ikdienā cilvēku izmantotās lietotnes, gan dažādas specifiskas un sarežģītas lietotnes un servisi izmanto šo plašo tīmekļa informāciju. Datu strukturēšana un sasaistīšana būtiski uzlabo šo lietotņu kvalitāti un iespējas. Liela vispārēju zināšanu krātuve un bāze ir atvērtā enciklopēdija Vikipēdija. Šī zināšanu bāze ir nestrukturēta, tādēļ komūnas veidots projekts DBpedia nodarbojas ar šo zināšanas bāzes strukturēšanu. Šie iegūtie strukturētie dati nopietni uzlabo lietotņu un servisu informācijas izmantošanas kvalitāti. DBpedia latviskā versija būtu nopietns ieguvums latviešu lietotņu attīstībā, kas atvērtu iespējas izmantot plašu zināšanas krājumu. Bakalaura darba mērķis ir izpētīt DBpedia darbošanās principus un tās zināšanu krājuma uzbūvi. Darba teorētiskajā daļā ietilpst DBpedia izpēte un raksturošana, bet praktiskajā daļā ietilpst DBpedia lokalizēšanas izpētīšana latviešu valodai un latviešu Vikipēdijas datiem.Nowadays virtually all of the information is available on the web and the web is also the main source of information. Both people everyday apps and various specific and complex applications and services uses this vast web information. Data structuring and interlinking significantly improves the quality and capabilities of these applications and services. Wikipedia is an open encyclopedia and large general knowledge base. Because this knowledge base is unstructured, community created DBpedia project deals with structuring of this knowledge base. This structured data severely improves quality of applications and services. Latvian version of DBpedia would be a significant benefit for Latvian application development which would open opportunities to use a rich knowledge base. Aim of this bachelor thesis is to explore DBpedia working principles and structure of its knowledge base. Theoretical part includes DBpedia research and characterization but practical part includes DBpedia research of localization for Latvian language and Latvian Wikipedia knowledge base

Core–Shell Engineering to Enhance the Spectral Stability of Heterogeneous Luminescent Nanofluids

This work was supported by the Spanish Ministerio de Educación y Ciencia (MAT2016-75362-C3-1-R) and by COST Action CM1403. L.L.-P. thanks the Universidad Autónoma de Madrid for the ‘‘Formación de Personal Investigador (FPI-UAM)’’program. P.H.-G. thanks the Spanish Ministerio de Economia y Competitividad for the Juan de la Cierva program (IJCI-2015-24551). M.P. and A.S. thank University of Verona (Italy) for financial support in the framework of the ‘‘Cooperint 2016’’ and “Ricerca di Base 2015” projects. The work of K.S. was supported by Latvian National Research Program IMIS2 (Grant No. 302/2012).The tendency to the miniaturization of devices and the peculiar properties of the nanoparticles have raised the interest of the scientific community in nanoscience. In particular, those systems consisting of nanoparticles dispersed in fluids, known as nanofluids, have made it possible to overcome many technological and scientific challenges, as they show extraordinary properties. In this work, the loss of the spectral stability in heterogeneous luminescent nanofluids is studied revealing the critical role played by the exchange of ions between different nanoparticles. Such ion exchange is favored by changes in the molecular properties of the solvent, making heterogeneous luminescent nanofluids highly unstable against temperature changes. This work demonstrates how both temporal and thermal stabilities of heterogeneous luminescent nanofluids can be substantially improved by core–shell engineering. This simultaneously avoids the leakage of luminescent ions and the effects of the solvent molecular changes.Ministerio de Ciencia Tecnología y Telecomunicaciones MAT2016-75362-C3-1-R, 302/2012; University of Verona (Italy); European Cooperation in Science and Technology CM1403; 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