Fotoaktivne nanokompozitne tanke plasti na steklu in termično neobstojnih podlagah

Photocatalysis is a well-known process for the last few decadesit is predominantly used for water and air purification, but also for self-cleaning and antibacterial surfaces. The photocatalytic process is one of the advanced oxidation processes, where semiconductors are mainly used as photocatalysts. The most known and used semiconductor is nanosized titania, which can non-selectively decompose organic matters. One of the side effects of nano TiO2 under UV irradiation is photoinduced hydrophilicity, which furthermore improves the self-cleaning effect. The main drawback of TiO2 is that for its activation UV light is needed, which represents only 5 percent of the solar spectrum. Consequently, actinic irradiance power is low and the response of photocatalyst is limited. Novel approaches are being introduced to improve TiO2 response to visible light such as doping, coupling, modification of surface morphology and others. The thesis consists of five principal chapters. The first chapter is focused on a short literature review and explanation of some basic terms and principles that are related to this thesis. The aim of the research was to prepare transparent photocatalytically active thin films on glass and thermosensitive substrates. Four thermosensitive substrates were used: polyvinyl chloride (PVC) foil, polymethyl methacrylate (PMMA) sheet and polyester (PES) fabric coated with a polyvinyl and acrylic coating, with (D1) or without (D2) an additional polyvinylidene fluoride topcoat. The synthesis of films was modified with the introduction of zirconium aiming at improving the photocatalytic activity of the TiO2 films, and the final films had a SiO2 phase present for increased mechanical robustness. The third chapter is dedicated to the experimental part of the thesis. The detailed process of synthesis is described. The sol-gel process was used to prepare initial Ti-Zr sols, colloidal aqueous solutions with TiO2 and ZrO2 nanoparticles derived from titanium and zirconium alkoxides. The four different Ti-Zr sols were prepared with 0, 5, 10 and 20 molar % of Zr according to Ti. The depositing solution was prepared by mixing Ti-Zr sol, SiO2 sol binder, 1-propanol and 2-propoxyethanol, and then thin films were deposited by dip-coating technique. After the deposition, samples did not require high-temperature calcination since the photocatalytic anatase phase was present already after drying the deposited layers. Coated glass slides were put into a furnace at 150 °C, while samples on thermosensitive substrates were just treated by a heat gun. Samples in powder and thin film form were characterized by UV-Vis, FTIR-ATR and laser beam deflection spectroscopy, X-ray diffraction, scanning electron microscopy and thermal analysis. One of the main aspects of the photocatalyst is its activity. Photocatalytic activity of the thin films was determined, either quantitatively by the formation of fluorescent hydroxyterephthalic acid, one of the first degradation products of terephthalic acid deposit, or qualitatively by a visual-based method where degradation of resazurin ink was observed. Two additional methods were used on glass samples, electron paramagnetic resonance, and degradation of methyl stearate by observing the change in water contact angle under UVA irradiation. Mechanical stability of films on various substrates is an essential factor, describing how successful was immobilization of the photocatalytic materials on the substrate. It was determined by the pencil hardness test, i.e., Wolff-Wilborn method. In the fourth chapter, titled “Results and Discussion,” the most important part of the thesis is placed. Materials characterization and associated discussion of the results are divided into three major parts: i) powder samples characterizationii) characterization of thin films on a glass substrate, and iii) characterization of films on thermosensitive substrates. In the conclusions, the main findings of the Ph.D. research work are summarized. One of our initial hypotheses was disapproved, thin films were not more active with a higher content of zirconium. However, they were more durable. All the obtained films were transparent and photoactive, despite the low-temperature synthesis procedure. Besides commonly used glass substrate, immobilization on thermosensitive substrates was also successful.Fotokataliza je postala v zadnjih nekaj desetletjih zelo razširjenauporablja se predvsem za čiščenje vode in zraka, za samočistilne ter protibakterijske površine. Fotokatalitski proces spada med napredne oksidacijske procese in kot fotokatalizatorji so največkrat uporabljeni polprevodniki. Najbolj znan in najpogosteje uporabljen polprevodnik je (nano) titanov dioksid, ki lahko neselektivno razgradi organske snovi ob UV sevanju. Pri obsevanju TiO2 z UV svetlobo se pojavi tudi fotovzbujena hidrofilnost, ki še dodatno izboljša samočistilni učinek. Ena od glavnih pomanjkljivosti TiO2 je, da se za njegovo fotoaktivacijo uporablja UV svetloba, ki predstavlja le pet odstotkov sončnega spektra. Za boljši odziv TiO2 na vidno svetlobo se razvijajo novi postopki, na primer dopiranje, kombiniranje z drugimi polprevodniki, modifikacija morfologije površine itd. Doktorsko delo ima pet glavnih poglavij. Prvo poglavje je osredotočeno na krajši pregled obstoječe literature in razlago nekaterih osnovnih pojmov. V drugem poglavju je predstavljen namen doktorskega dela. Pripravila sem transparentne fotoaktivne tanke plasti na steklu in temperaturno občutljivih podlagah. Izbrala sem štiri različne občutljive podlage: polivinil kloridna (PVC) folija, polimetil metakrilat (PMMA) plošča in poliesterska (PES) tkanina, prevlečena s slojem polivinila in akrila z (D1) ali brez (D2) dodatne poliviniliden fluoridne (PVDF) prevleke. Postopek priprave filmov smo obogatili z vpeljavo cirkonija, tako naj bi izboljšali aktivnost samih TiO2 filmov, končni raztopini je bil dodan tudi SiO2, ki je izboljšal mehanske lastnosti filmov. Tretje poglavje je posvečeno eksperimentalnemu delu. V poglavju je opisan podroben proces sinteze tankih plasti. Sol-gel postopek sem uporabila za pripravo začetnih Ti-Zr solov izhajajoč iz titanovega in cirkonijevega alkoksida. Pripravila sem štiri različne Ti-Zr sole z 0, 5, 10 in 20 množinskimi % cirkonija glede na titan. Raztopine za nanašanje so vsebovale Ti-Zr sol, SiO2 vezivo, 1-propanol in 2-propoksietanoltanke plasti pa so bile nanešene s tehniko potapljanja. Tanke filme po nanosu ni bilo potrebno termično obdelati na visoki temperaturi, ker je fotoaktivna anatazna faza že prisotna po sušenju vzorcev. Tako so bili vzorci na steklu toplotno obdelani v peči pri 150 ° C, vzorce na termično neobstojnih podlagah pa sem utrdila zgolj s toplotno pištolo. Praškaste vzorce in tanke plasti smo karakterizirali z naslednjimi metodami: UV-Vis, FTIR-ATR spektroskopijo in spektroskopijo z odklonom laserskega žarka, rentgensko praškovno difrakcijo, presevno elektronsko mikroskopijo in termično analizo. Najpomembnejša lastnost fotokatalizatorja je fotoaktivnost, ta je bila določena na tankih plasteh z dvema različnima metodamakvantitativno z merjenjem koncentracije hidroksiteraftalne kisline po razgradnji teraftalne kislinein kvalitativno, z opazovanjem razgradnje barvila resazurin. Z dvema dodatnima metodama smo izmerili fotoaktivnost tankih plasti na stekleni podlagi, z elektronsko paramagnetno resonanco in z merjenjem kontaktnega kota po razgradnji metil stearata pri UV obsevanju. Zelo pomembna lastnost tankih plati je mehanska odpornost in z merjenjem le te lahko ocenimo, če je bila imobilizacija na podlago uspešna. Mehansko stabilnost filmov smo določili z Wolff-Wilborn-ovo metodo. V četrtem poglavju je opisana karakterizacija materialov s spremljajočo razpravo o rezultatih, ki je razdeljena na tri glavne dele: i) karakterizacija praškastih vzorcevii) karakterizacija tankih plasti na stekleni podlagi in iii) karakterizacija tankih plasti na termično neobstojnih podlagah. V zaključku so povzete glavne ugotovitve. Ena od naših začetnih hipotez ni bila potrjena, saj tanke plasti z višjo vsebnostjo cirkonija niso bile aktivnejše, izkazovali pa so večjo mehansko odpornost. Vsi vzorci so bili, kljub nizki temperaturi pripravi, transparentni in fotoaktivni. Imobilizacija fotokatalizatorjev je bila uspešna na steklu kot tudi na termično neobstojnih podlagah

FUNCTIONALIZATION OF FIBRES FOR BIOACTIVE PROPERTIES

Poudarek pri razvoju inovativnih sanitetnih materialov ter medicinskih tekstilij je v uporabi biorazgradljivih vlaknotvornih materialov, kot so celulozna vlakna (naravna ter regenerirana celulozna vlakna). Eden izmed pomembnih kriterijev uporabnosti celuloznih materialov za posebne namene je predvsem njihova površinska in biološka aktivnost, kakor tudi biološka razgradljivost. Tako je celuloza idealni izhodni material za funkcionalizacijo z namenom pridobitve protimikrobnih lastnosti materialov, ter posledično ustvarjanja medicinskih izdelkov. Dejstvo je, da je veliko število proti-mikrobnih spojin, ki se uporabljajo za funkcionalizacijo celuloznih vlaken v tekstilni industriji, vendar se sklepa, da mnoga od teh ne zagotavljajo popolne varnosti za varovanje zdravja ljudi in okolja. Na razpolago je množica učinkovitih proti-mikrobnih spojin, ki se razlikujejo po mehanizmu delovanja, vendar se znanost pospešeno posveča iskanju spojin in razvoju postopkov, ki bi temeljili izključno na rabi naravnih materialov, ki zagotavljajo popolno varnost za ljudi kakor tudi okolje. Ena izmed najbolj obetavnih naravnih spojin z odličnimi proti-mikrobnimi lastnostmi je hitozan. Delovanje tega naravnega polisaharida, ki se pridobiva iz hitina, je odvisno deleža in, predvsem, dostopnosti aminskih skupin hitozana, ki jim pripisujemo proti-mikrobno delovanje. V raziskavi smo uporabili različna regenerirana celulozna vlakna, kot so: viskoza, liocel in modal, ki spadajo v skupino regeneriranih celuloznih vlaken za katere je znano da so, v primerjavi z bombažem, ki vsebuje znaten delež voskov, pektinov, naravnih barvil in nemalokrat obremenjenost s pesticidi, večje čistosti in zato za potrebe protibakterijskih obdelav še posebej zanimiva. Našteta vlakna smo protimikrobno funkcionalizirali s 1% raztopino hitozana. Uspešnost funkcionalizacije smo merili s potenciometrično titracijo, spektrofotometrično metodo C.I. Acid Orange 7 in z mikrobiološkim testiranjem. Rezultati obeh analiznih metod dobro sovpadajo. Največjo vsebnost aminskih skupin kaže viskoza, sledi modal in nato liocel. Rezultati obeh tehnik dobro sovpadajo. Vsebnost aminskih skupin vpliva na protimikrobni značaj vlaken. Dokazali smo, da je v povprečju pri vlaknih, z višjo vsebnostjo aminskih skupin dosežena boljša redukcija patogenih bakterij, kakor patogenih gliv. Funkcionalizirana vlakna kažejo potencialno uporabo na številnih področji kot so medicinske tekstilije, tehnične tekstilije, tekstilije za dom in prosti čas, oblačila za zaščito in šport itd.The emphasis of innovative sanitary materials and medical textiles is given on the development of renewable fiber-forming materials e.g. cellulose natural and regenerated fibers. One of the most important criteria of cellulose material for special use is, most of all, its surface and biological activity and biological degradability. For this purpose cellulose is an ideal substrate for anti microbial treatment and, consequently for medical materials production. There are a lot of antimicrobial substances nowadays which are suitable for cellulose fibers functionalization in the textile industry area but most of them are not ecologically acceptable. In the commercial use a lot of efficient antimicrobial substances are in the market but due to the restrictions according to the ecology, researches are forced to find and to develop substances and procedures which are safe for humans and environment. One of the most promising substances with excellent antimicrobial properties is chitosan. Activity of this polysaccharide isolated from chitin depends on the amount and, most of all, on the accessibility of amino groups which present antimicrobial sites of chitosan. In this research different regenerated cellulose fibers were used as: viscose, lyocel and modal. If compared to the cotton which possesses certain amount of waxes, pectines, natural pigments and pesticides, regenerated fibers are purer and therefore very interesting scope for antimicrobial application. All fibers used in the research were antimicrobial functionalized with the 1% solution of chitosan. Estimation in the sense of antimicrobial activity was performed with the potentiometric titration, the spectrophotometric method Acid orange 7 supported by microbiological testing. Both methods results are in good accordance. The highest amount of amino groups show viscose followed by modal and, finally by lyocel. The amount of amino groups strongly influences antimicrobial character of functionalized fibers. It is confirmed that fibers with higher content of amino groups show better reduction of pathogenic bacteria as well as pathogenic fungi. Functionalized fibers show potential use in the different fields of application e.g. medical textiles, technical textiles, textiles for home and casual wear, clothes for protection and sport, etc

The influence of fibre physico-chemical parameters onto their antimicrobial properties

Potreba in zahteva po protimikrobni obdelavi tekstilij je zelo velika. Raziskanih je že precej različnih spojin, ki imajo te lastnosti, vendar jih je veliko škodljivih za ljudi in okolje. Zato je trend v iskanju naravnih in neškodljivih protimikrobnih sredstev. Žal pa je njihova vezava na tekstilno matrico in tudi stopnja učinkovitosti po navadi slabša. Problem s katerim smo se soočili že v diplomskem delu je, da smo dobili redukcijo mikroorganizmov na vzorcih, ki sploh niso bili obdelani s protimikrobnim sredstvom. Učinkovitost obdelanih tekstilij s protimikrobnimi sredstvi se določa z različnimi metodami, standardiziranimi in nestandardiziranimi. Vsaka od teh metod ima različen pristop k vrednotenju. Najbolj pogosto uporabljene so AATCC 100, AATCC 147, ASTM E 2149 in JIS L 1902. Problem pri nekaterih metodah je, da so rezultati pokazali nerazumljivo inhibicijo patogenih organizmov, kjer naj ne bi bila prisotna kot na primer pri neobdelanem vzorcu. Velikokrat prihaja tudi do napačne interpretacije rezultatov. Zato smo se v tem magistrskem delu osredotočili na testiranje neobdelanih tekstilnih vzorcev po različnih metodah. Izbrali smo najbolj pogoste in nam dostopne metode ASTM E 2149, ASTM E 2315 in JIS L 1902. Vzorce smo dali testirati v različne laboratorije. Kot vidimo v poglavju, Rezultati in meritve v preglednici 4.10 smo kljub temu dobili redukcijo mikroorganizmov. Zato smo preučili vpliv fizikalno-kemijskih parametrov vlaken, na mikrobiološke lastnosti vlaken.Antimicrobial treatment of textiles is nowadays widespread. On market there are a lot of different substances, which have that kind of properties, but a lot of them are dangerous for people and environment. That is way there is a need for explore natural and harmless agents. But their properties of binding and level of their effectiveness is not so good. The problem, which we also have in my bachelor work, was that we get the inhibition of microorganisms on samples, which were not antimicrobial treated. Efficiency of treated textiles with antimicrobial agents is measure with varied methods, standardized and non- standardized. Each of these methods has a different way to evaluate an antimicrobial treatment. The most used methods are AATCC 100, AATCC 147, ASTM E 2149 and JIS L 1902. Antimicrobial test methods should be performed under controlled, standardised conditions to guarantee reproducibility of the results. A back draw of the standardized tests is also that, they are performed in conditions that are rarely found during the normal use of textile product. Problem of some methods are that, some of the results show illogical inhibition of pathogenic microorganisms, where it should not, for example at untreated samples. Or the interpretation of their results is wrong. Regarding all this many laboratories apply, in addition to standardized methods, also other tests for screening antimicrobial activity of functionalized surfaces. In this master’s work we decided to focus on testing the untreated samples with various standardized methods. We selected the one that are most used and were in our access, ASTM E 2149, ASTM E 2315 in JIS L 1902. As you can see in fourth chapter in table 4.10, in spite of all that sometimes we still got the inhibition of microorganisms. Because we want to know the reasons, we studied physic-chemical properties

Self-cleaning and photoactive TiO2 – ZrO2 – SiO2 films on thermosensitive and glass substrates

Nanosized TiO2 is well-known for its photocatalytic property. From the combination of photocatalysis and photoinduced hydrophilicity properties, thin films of this material have also anti-fogging, self-cleaning and antimicrobial properties. There are numerous deposition techniques e.g. spin-coating, dip-coating, spraying, the most suitable one is chosen based on substrate or solution characteristics. Thin films are often required to be transparent for visible light, especially if we use them on transparent substrates, or they should not affect the color of the substrate. Radicals that are produced during photosensitizing process are able to destroy structure of a substrate and substrate can lose mechanical stability [1,2]. Some studies show that adding a SiO2 protective layer can prevent the damage of the substrate [3–5]. Ti-Zr containing sols were prepared with sol-gel process, where titanium(IV) isopropoxide, zirconium(IV) butoxide and ethanol were hydrolyzed with aqueous solution of perchloric acid. Solution was then refluxed for 48 hours. During that time crystallization and deaggregation took place and that resulted in a stable final solution [6]. To prepare suitable solution for production of durable films silica binder was added. On glass and plastic substrates, thin films were deposited with the dip-coating method and dried with a heat-gun. Thin films were characterized by measurements of photocatalytic activity with terephthalic acid as model organic pollutant subjected to oxidation via fluorescent degradation product, photoinduced superhydrophilicity phenomena, UV-Vis and ATR-FTIR spectroscopy, SEM images, as well as mechanical properties measurements. References [1] H. Schmidt, M. Naumann, T.S. Müller, M. Akarsu, Thin Solid Films (2006) 502, 132– 137. [2] W. A. Daoud, J.H. Xin, Y.H. Zhang, Surf. Sci. (2005) 599, 69–75. [3] Ž. Senić, S. Bauk, M. Vitorović-Todorović, N. Pajić, A. Samolov, D. Rajić, Sci. Tech. Rev. (2011) 61, 63–72. [4] T. Yuranova, R. Mosteo, J. Bandara, D. Laub, J. Kiwi, J. Mol. Catal. A: Chem. (2006) 244, 160–167. [5] T. Yuranova, D. Laub, J. Kiwi, Catal. Today (2007) 122, 109–117. [6] N. Vodišek, K. Ramanujachary, V. Brezová, U. Lavrenčič Štangar, Catal. Today (2017) 287, 142–147

Transparent titania-zirconia thin films for self-cleaning and photocatalytic application

Thin films were prepared by sol-gel process, where different amount of zirconia were added to titania. Photocatalytic activity of thin films was measured by two methods i) determination of degradation ration of methyl stearate with measuring the contact angle and ii) formation of hydroxyterephthalic acid was measured by spectrofluorometer. Prepared samples were characterized by UV-Vis spectrophotometer, SEM, XRD, FT-IR ATR, and BET. The result of measurements of photocatalytic activity shows that the highest activity has a sample without addition of zirconia, but mechanical stability of that sample is worse

Transparent photocatalytic thin films on flexible polymer substrates

Self-cleaning and/or photocatalytic films on polymer substrates have found numerous applications during the past decades. However, the common demand for high-temperature post synthesis treatment limits the application to temperature resistant substrates only. Herein, we prepared self-cleaning photocatalytic films on four thermosensitive polymeric substrates: polyvinyl chloride (PVC), polymethyl methacrylate (PMMA), and acryl coated polyester (PES) fabric (D2) with poly(vinylidene fluoride) (PVDF) containing lacquer (D1). TiO$_2$ was prepared via a low-temperature sol-gel process using titanium(IV) isopropoxide and zirconium(IV) butoxide as precursors with various loading levels of Zr0, 5, 10, and 20 mol.%, and deposited on the substrates by using a SiO$_2$ binder in form of thin films (ca. 200 nm thick) via dip-coating. The films were characterized by SEM, hardness test, UV-Vis, photothermal beam deflection spectroscopy, and IR spectroscopy, while photocatalytic activity was measured by the fluorescence-based method of the terephthalic acid probe and wetting by contact angle measurements. Films containing 10 mol.% of Zr showed the best compromise regarding photocatalytic activity and mechanical stability while from substrates point of view PVC performed the best, followed by PMMA, D1, and D2. The beneficial role of SiO$_2$ binder was not only guaranteeing excellent mechanical stability, but also to prevent the D1 polymer from deteriorationthe latter was found to be labile to long-term solar-light exposure due to degradation of the top PVDF layer

Transparent Photocatalytic Thin Films on Flexible Polymer Substrates

Self-cleaning and/or photocatalytic films on polymer substrates have found numerous applications during the past decades. However, the common demand for high-temperature post synthesis treatment limits the application to temperature resistant substrates only. Herein, we prepared self-cleaning photocatalytic films on four thermosensitive polymeric substrates: polyvinyl chloride (PVC), polymethyl methacrylate (PMMA), and acryl coated polyester (PES) fabric (D2) with poly(vinylidene fluoride) (PVDF) containing lacquer (D1). TiO2 was prepared via a low-temperature sol-gel process using titanium(IV) isopropoxide and zirconium(IV) butoxide as precursors with various loading levels of Zr; 0, 5, 10, and 20 mol.%, and deposited on the substrates by using a SiO2 binder in form of thin films (ca. 200 nm thick) via dip-coating. The films were characterized by SEM, hardness test, UV-Vis, photothermal beam deflection spectroscopy, and IR spectroscopy, while photocatalytic activity was measured by the fluorescence-based method of the terephthalic acid probe and wetting by contact angle measurements. Films containing 10 mol.% of Zr showed the best compromise regarding photocatalytic activity and mechanical stability while from substrates point of view PVC performed the best, followed by PMMA, D1, and D2. The beneficial role of SiO2 binder was not only guaranteeing excellent mechanical stability, but also to prevent the D1 polymer from deterioration; the latter was found to be labile to long-term solar-light exposure due to degradation of the top PVDF layer

Field test of self-cleaning Zr-modified-TiO2_2-SiO2_2 films on glass with a demonstration of their anti-fogging effect

The number of commercial products claiming self-cleaning properties is rising and testing of long-term activity and durability of such coatings needs to be addressed more. The time-dependent changes of different characteristics like haze, transparency, and color are essential for transparent glazing materials. Herein, we aimed to examine whether the laboratory results obtained on the Zr-modified-titania-silica (TiZr) self-cleaning materials would translate to larger-scale outdoor-exposed testing. TiZr thin films were deposited via spraying onto float glass window surfaces and exposed into three different environments for 20 months. For comparison, a commercially available active SGG BIOCLEAN$^{TM}$ glass and standard float glass were simultaneously exposed in the same conditions. It was shown that the self-cleaning property of either a commercial product or TiZr-coated float glass was not considerably effective in real field test conditions, although the previous laboratory tests showed pronounced photocatalytic activity of TiZr thin films. The inclination anglehowever, was shown to have a considerable effect on the self-cleaning ability of samples, as did the rain patterns during the testing period. On the other hand, the anti-fogging effect of our TiZr material was very well expressed in controlled laboratory conditions (measuring droplet formation time) as well as in the real outdoor environment