Investigation of adsorption of dyes onto modified titanium dioxide

Titanium dioxide (TiO2) nanoparticles with different sizes and crystalloid structures produced by the thermal method and doped with silver iodide (AgI), nitrogen (N), sulphur (S) and carbon (C) were applied as adsorbents. The adsorption of Methyl Violet (MV), Methylene Blue (MB), Methyl Orange (MO) and Orange II on the surface of these particles was studied. The photocatalytic activity of some particles for the destruction of MV and Orange II was evaluated under sunlight and visible light. The equilibrium adsorption data were fitted to the Langmuir, Freundlich, Langmuir-Freundlich and Temkin isotherms. The equilibrium data show that TiO2 particles with larger sizes and doped with AgI, N, S and C have the highest adsorption capacity for the dyes. The kinetic data followed the pseudo-first order and pseudo-second order models, while desorption data fitted the zero order, first order and second order models. The highest adsorption rate constant was observed for the TiO2 with the highest anatase phase percentage. Factors such as anatase crystalloid structure, particle size and doping with AgI affect the photocatalytic activity significantly. Increasing the rutile phase percentage also decreases the tendency to desorption for N-TiO2 and S-TiO2. Adsorption was not found to be important in the photocatalytic decomposition of MV in an investigation with differently sized AgI-TiO2 nanoparticles. Nevertheless C-TiO2 was found to have higher adsorption activity onto Orange II, as the adsorption role of carbon approached synchronicity with the oxidation role.

Development of Raman microscopy methods for polymer coatings of polyfilms

Työn tavoitteena oli tutkia Raman-spektrometrin soveltuvuutta muovipäällystettyjen kartonkien syvyyssuuntaisiin mittauksiin. Lisäksi pyrittiin selvittämään voidaanko kiteisyyttä nähdä Raman-laitteistolla. Työn kirjallisessa osassa on selvitetty Raman-laitteiston teknisiä ominaisuuksia. Kokeellinen osa suoritettiin Lappeenrannan teknillisessä yliopistossa Membraanitekniikan ja teknillisen polymeerikemian laboratoriossa. Työssä käytettiin Horiban Jobin Yvon¿in valmistamaa konfokaalista Raman-spektrometri-laitteistoa (LabRam). Syvyyssuuntaisissa mittauksissa käytettiin apuna motorisoitua x-, y- ja z-suuntaan liikkuvaa tasoa. Mittaukset suoritettiin pistemäisesti tietyllä askelvälillä fokusoimalla näytteen pinnasta sisällepäin. Syvyysprofilointimittaukset aloitettiinmäärittelemällä laitteiston syvyysresoluutio eri konfokaalireikäkoolla. Lisäksityössä tehtiin syvyysprofilointimittauksia sekä läpinäkyvillä monikerrosmuoveilla että muovipäällystetyillä kartongeilla. Työssä mitatut muovipäällysteet sisälsivät pääasiassa polyeteeniä. Tulokset osoittivat, että Raman laitteistolla voidaan havainnoida Raman-aktiiviset ryhmät näytteen eri kerroksista. Lisäksi polyeteenin kiteisyysaste voidaan havaita tietyillä aallonpituuksilla.

Kromatografisen erotusfaasin huokoskoon karakterisointi

Työssä tutkittiin sulfonoitujen polystyreenidivinyylibentseenirunkoisten geeli-, meso- ja makrohuokoistenioninvaihtohartsien rakennetta käyttäen useita eri karakterisointimenetelmiä. Lisäksi työssä tutkittiin hartsien huokoskoon vaikutusta aminohappojen kromatografisessa erotuksessa. Työn pääpaino oli hartsien huokoskoon ja huokoisuuden määrittämisessä. Sen selvittämiseksi käytettiin hyväksi elektronimikroskopiaa, typpiadsorptiomittauksia, sekä käänteistä kokoekskluusiokromatografiaa. Parhaat tulokset saatiin käänteisellä kokoekskluusiokromatografialla, joka perustuu erikokoisten dekstraanipolymeerien käyttöön mallimolekyyleinä. Menetelmä sopii meso- ja makrohuokoisuuden tutkimiseen, mutta sen heikkoutena on erittäin pitkä mittausaika. Menetelmä antaa myös huokoskokojakauman, mutta yhden hartsin mittaaminen voi kestää viikon. Menetelmää muutettiin siten, että käytettiin määritettävää huokoskokoaluetta kuvaavien kahden dekstraanipolymeerin seosta. Kromatografiset ajo-olosuhteet optimoitiin sellaisiksi, että injektoidussa seoksessa olevien dekstraanien vastehuiput erottuivat toisistaan. Tällöin voitiin luotettavasti määrittää tutkittavan stationaarifaasin suhteellinen huokoisuus. Tätä työssä kehitettyä nopeaa käänteiseen kokoekskluusiokromatografiaan perustuvaa menetelmää kutsutaan kaksipistemenetelmäksi. Hartsien sulfonihapporyhmien määrää ja jakautumista tutkittiin määrittämällä hartsien kationinvaihtokapasiteetti sekä tutkimalla hartsin pintaa konfokaali-Raman-spektroskopian avulla. Sulfonihapporyhmien ioninvaihtokyvyn selvittämiseksi mitattiin K+-muotoon muutetusta hartsista S/K-suhde poikkileikkauspinnasta. Tulosten perusteella hartsit olivat tasaisesti sulfonoituneet ja 95 % rikkiatomeista oli toimivassa ioninvaihtoryhmässä. Aminohappojen erotuksessa malliaineina oli lysiini, seriini ja tryptofaani. Hartsi oli NH4+-muodossa ja petitilavuus oli 91 mL. Eluenttina käytettiin vettä, jonka pH oli 10. Paras tulos saatiin virtausnopeudella 0,1 mL/min, jolla kaikki kolme aminohappoa erottuivat toisistaan Finex Oy:n mesohuokoisella KEF78-hartsilla. Muilla tutkituilla hartseilla kaikki kolme aminohappoa eivät missään ajo-olosuhteissa erottuneet täysin.

Brightness of multilayer boards

A good appearance of a package enhances the sale of the product. The packing gives information about the content and instructions for the usage. In this master’s thesis, the optical properties of multilayer packaging board is studied. Especially means of increasing brightness of the multilayer board are evaluated. In the literature part, the effect of different factors on optical properties of a multilayer board are evaluated with the help of light scattering and absorption coefficients. The Kubelka-Munk theory can be used also in modelling brightness of the multilayer board. A large variety of different process factors, chemical aids and machine variables affect optical properties of board. In the experimental part, different methods to increase brightness of a 3-layer board were evaluated. It was discovered that brightness variation of broke (30 % share of the center layer pulp) have only minor influence on brightness of the board. The brightness variation must be high, roughly 9 % in order to alter brightness of the board by 1 %. Higher brightness can be achieved by bleaching the pulp, which holds the largest share of the center layer pulp. Here, 2,6 % increase in brightness of the pulp (60 % share of the center layer pulp) increased brightness of the board by 1 %. In a trial run at a board machine, there was no indication of decreased bulk of the board due to extended bleaching of the pulp. With pulp dyeing appearance and optical properties of a multilayer board can be influenced. By using bluish dyes the natural yellowness of pulps can be decreased and impression of whiteness is then increased. Brightness may deteriorate though, because of increasing light absorption of the dyed pulps. When the yellowness comes from the center layer pulp, the dye should be introduced there. Then the brightness decreasing effect of the dye decreases brightness of the board less. It was noticed that it is more important to maintain brightness of the top layer than brightness of the center layer, because the top layer pulp affects on brightness of the board the most. By introducing fillers into the top layer of a multilayer board it is possible to increase brightness of the board. Fillers with the highest light scattering increased the brightness of the board the most. Increasing light scattering increases brightness and also opacity. Higher opacity in the top layer decreases also the darkening effect of the center layer. Calcinated kaolin and PCC was found to increase the light scattering of the top layer the most at the filler comparison. Introducing fillers into the top layer of multilayer board may decrease bulk and modulus of elasticity of the top layer. This could lead to deteriorated bending stiffness.

Reduction and Analysis Methods of Indigo

Throughout history indigo was derived from various plants for example Dyer’s Woad (Isatis tinctoria L.) in Europe. In the 19th century were the synthetic dyes developed and nowadays indigo is mainly synthesized from by-products of fossil fuels. Indigo is a so-called vat dye, which means that it needs to be reduced to its water soluble leucoform before dyeing. Nowadays, most of the industrial reduction is performed chemically by sodium dithionite. However, this is considered environmentally unfavourable because of waste waters contaminating degradation products. Therefore there has been interest to find new possibilities to reduce indigo. Possible alternatives for the application of dithionite as the reducing agent are biologically induced reduction and electrochemical reduction. Glucose and other reducing sugars have recently been suggested as possible environmentally friendly alternatives as reducing agents for sulphur dyes and there have also been interest in using glucose to reduce indigo. In spite of the development of several types of processes, very little is known about the mechanism and kinetics associated with the reduction of indigo. This study aims at investigating the reduction and electrochemical analysis methods of indigo and give insight on the reduction mechanism of indigo. Anthraquinone as well as it’s derivative 1,8-dihydroxyanthraquinone were discovered to act as catalysts for the glucose induced reduction of indigo. Anthraquinone introduces a strong catalytic effect which is explained by invoking a molecular “wedge effect” during co-intercalation of Na+ and anthraquinone into the layered indigo crystal. The study includes also research on the extraction of plant-derived indigo from woad and the examination of the effect of this method to the yield and purity of indigo. The purity has been conventionally studied spectrophotometrically and a new hydrodynamic electrode system is introduced in this study. A vibrating probe is used in following electrochemically the leuco-indigo formation with glucose as a reducing agent.

Lanthanide Chelates as Donors in Fluorescence Resonance Energy Transfer: Exciting Prospects for Bioaffinity Assay Detection

Fluorescence resonance energy transfer (FRET) is a non-radiative energy transfer from a fluorescent donor molecule to an appropriate acceptor molecule and a commonly used technique to develop homogeneous assays. If the emission spectrum of the donor overlaps with the excitation spectrum of the acceptor, FRET might occur. As a consequence, the emission of the donor is decreased and the emission of the acceptor (if fluorescent) increased. Furthermore, the distance between the donor and the acceptor needs to be short enough, commonly 10-100 Å. Typically, the close proximity between the donor and the acceptor is achieved via bioaffinity interactions e.g. antibody binding antigen. Large variety of donors and acceptors exist. The selection of the donor/acceptor pair should be done not only based on the requirements of FRET but also the performance expectancies and the objectives of the application should be considered. In this study, the exceptional fluorescence properties of the lanthanide chelates were employed to develop two novel homogeneous immunoassays: a non-competitive hapten (estradiol) assay based on a single binder and a dual-parametric total and free PSA assay. In addition, the quenching efficiencies and energy transfer properties of various donor/acceptor pairs were studied. The applied donors were either europium(III) or terbium(III) chelates; whereas several organic dyes (both fluorescent and quenchers) acted as acceptors. First, it was shown that if the interaction between the donor/acceptor complexes is of high quality (e.g. biotin-streptavidin) the fluorescence of the europium(III) chelate could be quenched rather efficiently. Furthermore, the quenching based homogeneous non-competitive assay for estradiol had significantly better sensitivity (~67 times) than a corresponding homogeneous competitive assay using the same assay components. Second, if the acceptors were chosen to emit at the emission minima of the terbium(III) chelate, several acceptor emissions could be measured simultaneously without significant cross-talk from other acceptors. Based on these results, the appropriate acceptors were chosen for the dual-parameter assay. The developed homogeneous dual-parameter assay was able to measure both total and free PSA simultaneously using a simple mix and measure protocol. Correlation of this assay to a heterogeneous single parameter assay was excellent (above 0.99 for both) when spiked human plasma samples were used. However, due to the interference of the sample material, the obtained concentrations were slightly lower with the homogeneous than the heterogeneous assay, especially for the free PSA. To conclude, in this work two novel immunoassay principles were developed, which both are adaptable to other analytes. However, the hapten assay requires a rather good antibody with low dissociation rate and high affinity; whereas the dual-parameter assay principle is applicable whenever two immunometric complexes can form simultaneously, provided that the requirements of FRET are fulfilled.

Taivekartongin sävytys ja jälkikellertyminen

Taivekartongilta vaaditaan nykyisin korkealaatuista ja tasaista ulkonäköä. Pakkauksen tehtävänä on parantaa myyntiä hyvällä ulkonäöllä ja siisteydellä sekä antaa informaatiota ja käyttöohjeita. Tässä diplomityössä tutkittiin taivekartongin sävyttämistä, optisia ominaisuuksia sekä vaaleuden ja sävyjen pysyvyyttä. Kirjallisuusosassa käsiteltiin paperin ja kartongin optisia ominaisuuksia sekä esiteltiin Kubelka-Munkin teoria. Teoriaa voidaan käyttää mm. monikerroskartongin vaaleuden ja sävyjen mallintamisessa. Esillä oli paljon eri prosessitekijöitä, massoja ja kemikaaleja, jotka vaikuttavat kartongin vaaleuteen ja sävyyn. Työssä kärsiteltiin myös keinoja vaikuttaa kartongin sävyyn sävytyksellä ja sävytyksen eri tapoja. Toisaalta vaaleuden ja sävyn pysyvyyteen vaikuttaa kartongin jälkikellertyminen. Työssä tarkasteltiin jälkikellertymisen mekanismeja ja siihen vaikuttavia tekijöitä sekä esitettiin keinoja ennalta ehkäistä ja estää kellertymistä. Kokeellisessa osassa käsiteltiin massan ja päällystyspastan värjäyksen vaikutuksia ulkonäköön ja optisiin ominaisuuksiin. Sinertävillä tai violeteilla sävyväreillä voidaan pienentää mekaanisten massojen luonnollista kellertyvyyttä, jolloin valkoisuuden vaikutelma lisääntyy. Värien lisääminen heikentää vaaleutta, koska värien lisäys nostaa valon absorptiota. Tämän takia on tärkeää lisätä väri mielellään siihen kerrokseen, jossa kellertävä massa on, joka on tyypillisesti kartongin keskikerros. Pintakerrokset ovat valkaistua sellua ja niillä on tärkeä merkitys kartongin vaaleudelle, joten värin lisäys pintaan alentaisi vielä merkittävämmin kartongin kokonaisvaaleutta. Pastan värjäyksellä saadaan tasaisuutta värjäykseen, mutta sävyn säätö on tehtävä edelleen massavärjäyksellä. Pigmenttivärien käytöllä pystytään lisäämään mm. valonkestoa kartongille. Kartongin ja paperituotteiden valonkeston tutkimiseen ei ole olemassa standardia. Työssä tutkittiin laboratorio-olosuhteissa ja huonevalossa vanhentuneiden kartonkinäytteiden vertailtavuutta. Materiaalivalinnoilla pystytään vaikuttamaan valon-kestoon. Siihen vaikuttavat mm. massan laatu, lateksivalinta sekä pigmenttivärin käyttö. Mekaanista massaa sisältävät tuotteet kellertyvät pääasiassa ligniinin takia. Ligniini sisältää paljon UV-säteilyyn reagoivia ryhmiä, jotka muuttuvat värilliseksi lisäten kellertymistä. Valkaistujen sellujen vanhentuminen on suhteessa mekaaniseen massaan erittäin vähäistä. SA-lateksin havaittiin suojaavan vaaleuden menetykseltä ja lisäävän sävyn pysyvyyttä paremmin kuin SB-lateksi.

Studies in offset ink setting

The offset printing process is complex and involves the meeting of two essentially complex materials, printing ink and paper, upon which the final product is formed. It can therefore be expected that a multitude of chemical and physical interactions and mechanisms take place at the ink-paper interface. Interactions between ink and paper are of interest to both the papermakers and ink producers, as they wish to achieve better quality in the final product. The objective of this work is to clarify the combined influence of paper coating structure, printing ink and fountain solution on ink setting and the problems related to ink setting. A further aim is to identify the mechanisms that influence ink setting problems, and to be able to counteract them by changing properties of the coating layer or by changing the properties of the ink. The work carried out for this thesis included use of many techniques ranging from standard paper and printability tests to advanced optical techniques for detection of ink filaments during ink levelling. Modern imaging methods were applied for assessment of ink filament remain sizes and distribution of ink components inside pigment coating layers. Gravimetric filtration method and assessment of print rub using Ink-Surface-Interaction-Tester (ISIT) were utilized to study the influence of ink properties on ink setting. The chemical interactions were observed with the help of modified thin layer chromatography and contact angle measurements using both conventional and high speed imaging. The results of the papers in this thesis link the press operational parameters to filament sizes and show the influence of these parameters to filament size distribution. The relative importance between the press operation parameters was shown to vary. The size distribution of filaments is important in predicting the ink setting behaviour, which was highlighted by the dynamic gloss and ink setting studies. Prediction of ink setting behaviour was also further improved by use of separate permeability factors for different ink types in connection to filtration equations. The roles of ink components were studied in connection to ink absorption and mechanism of print rub. Total solids content and ratio of linseed oil to mineral oil were found to determine the degree of print rub on coated papers. Wax addition improved print rub resistance, but would not decrease print rub as much as lowering the total solids content in the ink. Linseed oil was shown to absorb into pigment coating pores by mechanism of adsorption to pore walls, which highlights the need for sufficient pore surface area for improved chromatographic separation of ink components. These results should help press operators, suppliers of printing presses, papermakers and suppliers to papermakers, to better understand the material and operating conditions of the press as it relates to various print quality issues. Even though paper is in competition with electronic media, high quality printed products are still in demand. The results should provide useful information for this segment of the industry.

Unidirectional fiber-reinforced composite as an oral implant abutment material: Experimental studies of E-glass fiber/BisGMA-TEGDMA polymer in vitro

Fiber-reinforced composites (FRCs) are a new group of non-metallic biomaterials showing a growing popularity in many dental and medical applications. As an oral implant material, FRC is biocompatible in bone tissue environment. Soft tissue integration to FRC polymer material is unclear. This series of in vitro studies aimed at evaluating unidirectional E-glass FRC polymer in terms of mechanical, chemical, and biological properties in an attempt to develop a new non-metallic oral implant abutment alternative. Two different types of substrates were investigated: (a) Plain polymer (BisGMA 50%–TEGDMA 50%) and (b) Unidirectional FRC. The mechanical behavior of high fiber-density FRCs was assessed using a three-point bending test. Surface characterization was performed using scanning electron and spinning disk confocal microscopes. The surface wettability/energy was determined using sessile drop method. The blood response, including blood-clotting ability and platelet morphology was evaluated. Human gingival fibroblast cell responses - adhesion kinetics, adhesion strength, and proliferation activity - were studied in cell culture environment using routine test conditions. A novel tissue culture method was developed and used to evaluate porcine gingival tissue graft attachment and growth on the experimental composite implants. The analysis of the mechanical properties showed that there is a direct proportionality in the relationship between E-glass fiber volume fraction and toughness, modulus of elasticity, and load bearing capacity; however, flexural strength did not show significant improvement when high fiber-density FRC is used. FRCs showed moderate hydrophilic properties owing to the presence of exposed glass fibers on the polymer surface. Blood-clotting time was shorter on FRC substrates than on plain polymer. The FRC substrates also showed higher platelet activation state than plain polymer substrates. Fibroblast cell adhesion strength and proliferation rate were highly pronounced on FRCs. A tissue culture study revealed that gingival epithelium and connective tissue established an immediate close contact with both plain polymer and FRC implants. However, FRC seemed to guide epithelial migration outwards from the tissue/implant interface. Due to the anisotropic and hydrophilic nature of FRC, it can be concluded that this material enhances biological events related with soft tissue integration on oral implant surface.

Computational modeling of the properties of TiO2 nanoparticles

In this study we discuss the electronic, structural, and optical properties of titanium dioxide nanoparticles, and also the properties of Ni(II) diimine dithiolato complexes as dyes in dye-sensitized TiO2 based solar cells. The abovementioned properties have been modeled by using computational codes based on the density functional theory. The results achieved show slight evidence on the structure-dependent band gap broadening, and clear blue-shifts in absorption spectra and refractive index functions of ultra-small TiO2 particles. It is also shown that these properties are strongly dependent on the shape of the nanoparticles. Regarding the Ni(II) diimine dithiolato complexes as dyes in dye-sensitized TiO2 based solar cells, it is shown that based on the experimental electrochemical investigation and DFT studies all studied diimine derivatives could serve as potential candidates for the light harvesting, but the e ciencies of the dyes studied are not very promising.

Developing Bioimage Informatics – from Microscopy to Software Solutions – with alpha2beta1 Integrin as a Case Study

Biokuvainformatiikan kehittäminen – mikroskopiasta ohjelmistoratkaisuihin – sovellusesimerkkinä α2β1-integriini Kun ihmisen genomi saatiin sekvensoitua vuonna 2003, biotieteiden päätehtäväksi tuli selvittää eri geenien tehtävät, ja erilaisista biokuvantamistekniikoista tuli keskeisiä tutkimusmenetelmiä. Teknologiset kehitysaskeleet johtivat erityisesti fluoresenssipohjaisten valomikroskopiatekniikoiden suosion räjähdysmäiseen kasvuun, mutta mikroskopian tuli muuntua kvalitatiivisesta tieteestä kvantitatiiviseksi. Tämä muutos synnytti uuden tieteenalan, biokuvainformatiikan, jonka on sanottu mahdollisesti mullistavan biotieteet. Tämä väitöskirja esittelee laajan, poikkitieteellisen työkokonaisuuden biokuvainformatiikan alalta. Väitöskirjan ensimmäinen tavoite oli kehittää protokollia elävien solujen neliulotteiseen konfokaalimikroskopiaan, joka oli yksi nopeimmin kasvavista biokuvantamismenetelmistä. Ihmisen kollageenireseptori α2β1-integriini, joka on tärkeä molekyyli monissa fysiologisissa ja patologisissa prosesseissa, oli sovellusesimerkkinä. Työssä saavutettiin selkeitä visualisointeja integriinien liikkeistä, yhteenkeräytymisestä ja solun sisään siirtymisestä, mutta työkaluja kuvainformaation kvantitatiiviseen analysointiin ei ollut. Väitöskirjan toiseksi tavoitteeksi tulikin tällaiseen analysointiin soveltuvan tietokoneohjelmiston kehittäminen. Samaan aikaan syntyi biokuvainformatiikka, ja kipeimmin uudella alalla kaivattiin erikoistuneita tietokoneohjelmistoja. Tämän väitöskirjatyön tärkeimmäksi tulokseksi muodostui näin ollen BioImageXD, uudenlainen avoimen lähdekoodin ohjelmisto moniulotteisten biokuvien visualisointiin, prosessointiin ja analysointiin. BioImageXD kasvoi yhdeksi alansa suurimmista ja monipuolisimmista. Se julkaistiin Nature Methods -lehden biokuvainformatiikkaa käsittelevässä erikoisnumerossa, ja siitä tuli tunnettu ja laajalti käytetty. Väitöskirjan kolmas tavoite oli soveltaa kehitettyjä menetelmiä johonkin käytännönläheisempään. Tehtiin keinotekoisia piidioksidinanopartikkeleita, joissa oli "osoitelappuina" α2β1-integriinin tunnistavia vasta-aineita. BioImageXD:n avulla osoitettiin, että nanopartikkeleilla on potentiaalia lääkkeiden täsmäohjaussovelluksissa. Tämän väitöskirjatyön yksi perimmäinen tavoite oli edistää uutta ja tuntematonta biokuvainformatiikan tieteenalaa, ja tämä tavoite saavutettiin erityisesti BioImageXD:n ja sen lukuisten julkaistujen sovellusten kautta. Väitöskirjatyöllä on merkittävää potentiaalia tulevaisuudessa, mutta biokuvainformatiikalla on vakavia haasteita. Ala on liian monimutkainen keskimääräisen biolääketieteen tutkijan hallittavaksi, ja alan keskeisin elementti, avoimen lähdekoodin ohjelmistokehitystyö, on aliarvostettu. Näihin seikkoihin tarvitaan useita parannuksia,

Reducing contact resistance in graphene devices

In this thesis, the contact resistance of graphene devices was investigated because high contact resistance is detrimental to the performance of graphene field-effect transistors (GFET). Method for increasing so-called edge-contact area was applied in device fabrication process, as few nanometers thick Ni layer was used as a catalytic etchant during the annealing process. Finally, Ni was also used as a metal for contact. GFETs were fabricated using electron beam lithography using graphene fabricated by chemical vapor deposition (CVD). Critical part of the fabrication process was to preserve the high quality of the graphene channel while etching the graphene at contact areas with Ni during the annealing. This was achieved by optimizing the combination of temperature and gas flows. The structural properties of graphene were studied using scanning electron microscopy, scanning confocal μ-Raman spectroscopy and optical microscopy. Evaluation of electric transport properties including contact resistance was carried out by transmission line method and four-probe method. The lowest contact resistance found was about at 350 Ωμm. In addition, different methods to transfer CVD graphene synthesized on copper were studied. Typical method using PMMA as a supporting layer leaves some residues after its removal, thus effecting on the performance of a graphene devices. In a metal assisted transfer method, metal is used as an interfacial layer between PMMA and graphene. This allows more effective removal of PMMA. However, Raman spectra of graphene transferred by metal assisted method showed somewhat lower quality than the PMMA assisted method

Methyl and ethyl chloride synthesis in microreactors

Methyl chloride is an important chemical intermediate with a variety of applications. It is produced today in large units and shipped to the endusers. Most of the derived products are harmless, as silicones, butyl rubber and methyl cellulose. However, methyl chloride is highly toxic and flammable. On-site production in the required quantities is desirable to reduce the risks involved in transportation and storage. Ethyl chloride is a smaller-scale chemical intermediate that is mainly used in the production of cellulose derivatives. Thus, the combination of onsite production of methyl and ethyl chloride is attractive for the cellulose processing industry, e.g. current and future biorefineries. Both alkyl chlorides can be produced by hydrochlorination of the corresponding alcohol, ethanol or methanol. Microreactors are attractive for the on-site production as the reactions are very fast and involve toxic chemicals. In microreactors, the diffusion limitations can be suppressed and the process safety can be improved. The modular setup of microreactors is flexible to adjust the production capacity as needed. Although methyl and ethyl chloride are important chemical intermediates, the literature available on potential catalysts and reaction kinetics is limited. Thus the thesis includes an extensive catalyst screening and characterization, along with kinetic studies and engineering the hydrochlorination process in microreactors. A range of zeolite and alumina based catalysts, neat and impregnated with ZnCl2, were screened for the methanol hydrochlorination. The influence of zinc loading, support, zinc precursor and pH was investigated. The catalysts were characterized with FTIR, TEM, XPS, nitrogen physisorption, XRD and EDX to identify the relationship between the catalyst characteristics and the activity and selectivity in the methyl chloride synthesis. The acidic properties of the catalyst were strongly influenced upon the ZnCl2 modification. In both cases, alumina and zeolite supports, zinc reacted to a certain amount with specific surface sites, which resulted in a decrease of strong and medium Brønsted and Lewis acid sites and the formation of zinc-based weak Lewis acid sites. The latter are highly active and selective in methanol hydrochlorination. Along with the molecular zinc sites, bulk zinc species are present on the support material. Zinc modified zeolite catalysts exhibited the highest activity also at low temperatures (ca 200 °C), however, showing deactivation with time-onstream. Zn/H-ZSM-5 zeolite catalysts had a higher stability than ZnCl2 modified H-Beta and they could be regenerated by burning the coke in air at 400 °C. Neat alumina and zinc modified alumina catalysts were active and selective at 300 °C and higher temperatures. However, zeolite catalysts can be suitable for methyl chloride synthesis at lower temperatures, i.e. 200 °C. Neat γ-alumina was found to be the most stable catalyst when coated in a microreactor channel and it was thus used as the catalyst for systematic kinetic studies in the microreactor. A binder-free and reproducible catalyst coating technique was developed. The uniformity, thickness and stability of the coatings were extensively characterized by SEM, confocal microscopy and EDX analysis. A stable coating could be obtained by thermally pretreating the microreactor platelets and ball milling the alumina to obtain a small particle size. Slurry aging and slow drying improved the coating uniformity. Methyl chloride synthesis from methanol and hydrochloric acid was performed in an alumina-coated microreactor. Conversions from 4% to 83% were achieved in the investigated temperature range of 280-340 °C. This demonstrated that the reaction is fast enough to be successfully performed in a microreactor system. The performance of the microreactor was compared with a tubular fixed bed reactor. The results obtained with both reactors were comparable, but the microreactor allows a rapid catalytic screening with low consumption of chemicals. As a complete conversion of methanol could not be reached in a single microreactor, a second microreactor was coupled in series. A maximum conversion of 97.6 % and a selectivity of 98.8 % were reached at 340°C, which is close to the calculated values at a thermodynamic equilibrium. A kinetic model based on kinetic experiments and thermodynamic calculations was developed. The model was based on a Langmuir Hinshelwood-type mechanism and a plug flow model for the microreactor. The influence of the reactant adsorption on the catalyst surface was investigated by performing transient experiments and comparing different kinetic models. The obtained activation energy for methyl chloride was ca. two fold higher than the previously published, indicating diffusion limitations in the previous studies. A detailed modeling of the diffusion in the porous catalyst layer revealed that severe diffusion limitations occur starting from catalyst coating thicknesses of 50 μm. At a catalyst coating thickness of ca 15 μm as in the microreactor, the conditions of intrinsic kinetics prevail. Ethanol hydrochlorination was performed successfully in the microreactor system. The reaction temperature was 240-340°C. An almost complete conversion of ethanol was achieved at 340°C. The product distribution was broader than for methanol hydrochlorination. Ethylene, diethyl ether and acetaldehyde were detected as by-products, ethylene being the most dominant by-product. A kinetic model including a thorough thermodynamic analysis was developed and the influence of adsorbed HCl on the reaction rate of ethanol dehydration reactions was demonstrated. The separation of methyl chloride using condensers was investigated. The proposed microreactor-condenser concept enables the production of methyl chloride with a high purity of 99%.

Photon Upconverting Nanophosphors: Unique Reporters for Optical Biosensing

Upconversion photoluminescence is a unique property of mostly certain inorganic materials, which are capable of converting low-energy infrared radiation into a higher-energy emission at visible wavelengths. This anti-Stokes shift enables luminescence detection without autofluorescence, which makes the upconverting materials a highly suitable reporter technology for optical biosensing applications. Furthermore, they exhibit long luminescence lifetime with narrow bandwidths also at the optical window of biomaterials enabling luminescence measurements in challenging sample matrices, such as whole blood. The aim of this thesis was to study the unique properties and the applicability of nano-sized upconverting phosphors (UCNPs) as reporters in biosensing applications. To render the inorganic nanophosphors water-dispersible and biocompatible, they were subjected to a series of surface modifications starting with silica-encapsulation and ending with a bioconjugation step with an analyte-recognizing biomolecule. The paramagnetism of the lanthanide dopants in the nanophosphors was exploited to develop a highly selective separation method for the UCNP-bioconjugates based on the magnetic selectivity of the high gradient magnetic separation (HGMS) system. The applicability of the nano-sized UCNPs as reporters in challenging sample matrices was demonstrated in two homogeneous sensing applications based on upconversion resonance energy transfer (UC-RET). A chemosensor for intracellular pH was developed exploiting UC-RET between the UCNP and a fluorogenic pH-sensitive dye with strongly increasing fluorescence intensity in decreasing pH. The pH-independent emission of the UCNPs at 550 nm was used for referencing. The applicability of the pH-nanosensor for intracellular pH measurement was tested in HeLa cells, and the acidic pH of endosomes could be detected with a confocal fluorescence microscope. Furthermore, a competitive UC-RET-based assay for red blood cell folic acid was developed for the measurement of folate directly from a whole blood sample. The optically transparent window of biomaterials was used in both the excitation and the measurement of the UC-RET sensitized emission of a near-infrared acceptor dye to minimize sample absorption, and the anti-Stokes detection completely eliminated the Stokes-shifted autofluorescence. The upconversion photoluminescence efficiency is known to be dependent on crystallite size, because the increasing surface-to-volume ratio of nano-sized UCNPs renders them more susceptible to quenching effects of the environment than their bulk counterpart. Water is known to efficiently quench the luminescence of lanthanide dopants. In this thesis, the quenching mechanism of water was studied using luminescence decay measurements. Water was found to quench the luminescence of UCNPs by increasing the non-radiative relaxation of the excited state of Yb3+ sensitizer ion, which had a very strong quenching effect on upconversion luminescence intensity.

Fiber-reinforced composite fixed dental prostheses: Studies of the materials used as pontics

Fiber-reinforced composite fixed dental prostheses – Studies of the materials used as pontics University of Turku, Faculty of Medicine, Institute of Dentistry, Department of Biomaterials Science, Finnish Doctoral Program in Oral Sciences – FINDOS, Annales Universitatis Turkuensis, Turku, Finland 2015 Fiber-reinforced composites (FRC), a non-metallic biomaterial, represent a suitable alternative in prosthetic dentistry when used as a component of fixed dental prostheses (FDPs). Some drawbacks have been identified in the clinical performance of FRC restorations, such as delamination of the veneering material and fracture of the pontic. Therefore, the current series of studies were performed to investigate the possibilities of enhancing the mechanical and physical properties of FRC FDPs by improving the materials used as pontics, to then heighten their longevity. Four experiments showed the importance of the pontic design and surface treatment in the performance of FRC FDPs. In the first, the load-bearing capacities of inlay-retained FRC FDPs with pontics of various materials and thicknesses were evaluated. Three different pontic materials were assessed with different FRC framework vertical positioning. Thicker pontics showed increased load-bearing capacities, especially ceramic pontics. A second study was completed investigating the influence of the chemical conditioning of the ridge-lap surface of acrylic resin denture teeth on their bonding to a composite resin. Increased shear bond strength demonstrated the positive influence of the pretreatment of the acrylic surfaces, indicating dissolution of the denture surfaces, and suggesting potential penetration of the monomer systems into the surface of denture teeth. A third study analyzed the penetration depth of different monomer systems on the acrylic resin denture teeth surfaces. The possibility of establishing a durable bond between acrylic pontics and FRC frameworks was demonstrated by the ability of monomers to penetrate the surface of acrylic resin denture teeth, measured by a confocal scanning type microscope. A fourth study was designed to evaluate the load-bearing capacities of FRC FDPs using the findings of the previous three studies. In this case, the performance of pre-shaped acrylic resin denture teeth used as pontics with different composite resins as filling materials was evaluated. The filling material influenced the load-bearing capacities, providing more durable FRC FDPs. It can be concluded that the mechanical and physical properties of FRC FDPs can be improved as has been shown in the development of this thesis. The improvements reported then might provide long lasting prosthetic solutions of this kind, positioning them as potentially permanent rehabilitation treatments. Key words: fiber-reinforced composite, fixed dental prostheses, inlay-retained bridges, adhesion, acrylic resin denture teeth, dental material.