Persistence in major in relation to learning approaches – development of a questionnaire for university chemistry students

Increasing persistence in university level studies is a major concern worldwide. For example, in the United States an average of 70 % of students drop out from university studies, whereas in Europe the average drop-out rate is ca. 40 %. In Finland, university level chemistry education shows also a drop-out rate of ca. 40 %, and a half of this number consists of students who change their major subject. The major changers thus constitute an important part of the Finnish drop-out student population. With such high drop-out rates, it is of utmost importance to find ways for the early identification of students at risk of dropping completely or changing their major. The ultimate aim of this dissertation was to develop an instrument that could be used for the prediction of students at risk. This instrument, the ChemApproach questionnaire, was designed in such a way that it probes the learning approach features of chemistry students. As an additional feature in comparison with traditional learning approach instruments, ChemApproach also takes into account approaches to laboratory work. The results obtained during this thesis work indicate that the degree of the presence of certain learning approach features, namely the submissive surface and the practical deep approach features, strongly predict the students’ persistence, drop-out and change of major subject. It was confirmed that these features even override the initial intention of wanting to change major subject. The high impact of the practical deep approach highlights the high importance laboratory work in persistence and it serves as an indication of the good functionality of the ChemApproach questionnaire. As a consequence of the present thesis work, it was possible to propose institutional and teaching practices that can be used to decrease the level of the submissive surface approach and increase the level of the practical deep approach and thus increase persistence in chemistry studies.Yliopistotason opintojen keskeyttäminen on maailmanlaajuinen huolenaihe. Esimerkiksi Yhdysvalloissa keskimäärin 70 % opiskelijoista keskeyttää yliopistoopinnot ja Euroopassa näin käy keskimäärin 40 prosentille. Suomessa yliopistotason kemian opetuksen keskeyttäneiden osuus on myös luokkaa 40 % ja puolet tästä määrästä aiheutuu siitä, että opiskelijat vaihtavat pääainettaan. Pääaineen vaihtajien määrä on siis Suomen kemianopetuksen kannalta merkittävän suuri. Koska opintojen keskeyttäjien määrä on suuri, on tärkeää löytää välineitä, joilla voidaan tunnistaa keskeyttämis- ja vaihtamisvaarassa olevat opiskelijat mahdollisimman ajoissa. Tämän väitöskirjatyön päätavoite olikin kehittää työkalu, jonka avulla voitaisiin tunnistaa juuri nämä keskeyttämis- ja vaihtamisvaarassa olevat opiskelijat. Työssä kehitetty työkalu, ChemApproach-kyselykaavake, lähestyy asiaa opiskelijoiden oppimisen lähestymistapojen kautta. Perinteisiin lähestymistapaa kartoittaviin kaavakkeisiin nähden ChemApproach sisältää lisäksi osion, joka ottaa huomioon laboratoriotyöskentelyssä oppimisen. Tässä työssä saadut tulokset osoittavat selvästi, että tiettyjen lähestymistapojen piirteiden voimakkuus on vahvasti kytköksissä opintojen keskeyttämiseen ja pääaineen vaihtamiseen. Nämä piirteet, alistuvan pintaoppimsen ja käytännöllisen syväoppimisen piirteet, osoittautuivat merkittävämmiksi kuin opiskelijan ilmoittama halu vaihtaa pääainetta. Käytännöllisen syväsuuntautumisen merkityksen suuruus osoittaa laboratoriotyöskentelyn suuren merkityksen kemian oppimisessa, ja se myös osoittaa että ChemApproach on hyvin toimiva kemian opiskelijoiden tutkimuksessa. Tämän työn tuloksien ansiosta voitiin ehdottaa institutionaalisia sekä opetuksellisia käytänteitä, joiden avulla voitaisiin saada alistuneen pintasuuntautumisen määrää vähennettyä ja käytännöllisen syväoppimisen määrää lisättyä. Näiden käytänteiden avulla voidaan mahdollisesti lisätä kemian opintojaan jatkavien määrää

MATEMATIIKAN JA LUONNONTIETEIDEN OPETUKSEN TUTKIMUSSEURAN TUTKIMUSPäIVäT 2015 - ANNUAL SYMPOSIUM OF THE FINNISH MATHEMATICS AND SCIENCE EDUCATION RESEARCH ASSOCIATION 2015

Kemian oppiaineen ongelmana suomalaisissa yliopistoissa on ollut pääainettavaihtavien määrän suuruus. Tässä tutkimuksessa selvitettiin erityisesti kemianopiskeluun liittyvällä lomakkeella kemian opiskelijoiden lähestymistapoja oppimiseenja niiden yhteyttä halukkuuteen vaihtaa pääainetta. Tutkimuksen tuloksena oli, ettäpääaineen vaihtoa haluavilla on pinnallisempi lähestymistapa oppimiseen kuin niillä,jotka jatkavat opintojaan kemia pääaineenaan. Siirryttäessä perusopinnoistaaineopintoihin vaihtohalukkaiden määrä laskee huomattavasti ja käytännöllinensyväoppimisen lähestymistapa lisääntyy. Vaihtohalukkuutta voitaisiin mahdollisestivähentää kehittämällä opiskelijoiden syväoppimisen lähestymistapaa.</p

Restraining fluoride loss from NaYF4:Yb3+,Er3+ upconverting nanoparticles in aqueous environments using crosslinked poly(acrylic acid)/poly(allylamine hydrochloride) multilayers

The use of upconverting nanoparticles in various applications in aqueous media relies on their surface modifications as most synthesis routes yield hydrophobic particles. However, introducing upconverting nanoparticles in aqueous solutions commonly results in the quenching of their luminescence intensity and in the worst case, disintegration of the nanoparticles. We demonstrate the use of poly(acrylic acid) and poly(allylamine hydrochloride) as a protecting layer-by-layer coating for the upconverting NaYF4:Yb3+,Er3+ nanoparticles. The formation and crosslinking of the bilayer coating was confirmed with Fourier transform infrared spectroscopy, thermal analysis and zeta potential. The release of internal fluoride ions from the nanoparticle structure and subsequent particle disintegration was decelerated especially by crosslinking the bilayer coating on the surface. In addition, we studied the effect of the coating on the upconversion luminescence properties and learned that with additional fluoride ions present during the layer-by-layer assembly the most intense enhancement in the luminescent intensity is obtained. This is due both to not allowing the disintegration of the particles during the surface modification process as well as preventing the water molecules accessing the surface by crosslinking the bilayer coating.</p

Amorphous-to-crystalline transition and photoluminescence switching in guest-absorbing metal-organic network thin films

An amorphous metal-organic framework (aMOF) is an oxymoron as the porosity derived from the ordered network of the metal and organic moieties is the main characteristic of conventional crystalline MOFs. However, amorphous metal-organic materials can be synthesized from gaseous precursors through atomic/molecular layer deposition (ALD/MLD). We demonstrate an exciting interplay between luminescence properties and amorphous-to-crystalline transition realized upon water absorption in ALD/MLD aMOF films

Layered Double Hydroxide-Cellulose Hybrid Beads: A Novel Catalyst for Topochemical Grafting of Pulp Fibers

Cellulose-based materials are very attractive for emerging bioeconomy as they are renewable, inexpensive, and environmentally friendly. Cellulose beads are spherical and porous and can be highly engineered to be used as catalyst support material. This type of inorganic catalysts is cost-effective and suitable for multiple re-usage and has been rarely explored in cellulose reaction research. In this work, NiFe-layered double hydroxide (LDH) was tailor-made in situ on anionic cellulose beads to form a hybrid, supported photocatalyst for the first time. The hybrid beads were prepared in a size larger than the pulp fibers in order to make the catalysis reaction heterogeneous in nature. Hydrophilic pulp fibers were converted into hydrophobic pulp by photocatalytic topochemical grafting of ethyl acrylate using the LDH-cellulose bead catalyst. The approach identified for the modification of the pulp fibers is the “hydrogen abstraction–UV photografting” because the low-energy, UV radiation-induced grafting offers advantages, such as a reduced degradation of the backbone polymer and a control over the grafting reaction. After grafting, the pulp fibers showed increased water repellency and unaltered thermal stability, indicating the hydrophobic, plasticizing nature of the pulp, which in turn accounts for its thermoformable behavior. These acrylated pulp fibers can be further designed/customized for waterproof or oil absorption applications.</p

Lanthanide-based inorganic-organic hybrid materials for photon-upconversion

Photon-upconversion materials are capable of converting low energy infrared light into higher energy visible or ultraviolet light. Such materials are demanded for applications such as deep-tissue imaging, cancer therapy, nano-thermometry, biosensing, display and solar-cell technologies, and beyond. Trivalent lanthanide ions are promising materials for upconversion due to their suitable f-orbital energy levels allowing absorption in the near-infrared and emission in the visible wavelength range. The major obstacle in realizing the full potential of the Ln-based upconverters is their characteristically small absorption cross-sections. As many organic molecules possess much larger absorption cross-sections, their combination with Ln3+ ions could bring about remarkable mutual benefits. Additionally, the organic ligands can also function as spacers to yield metal–organic framework type upconverting materials. Indeed, superior upconverting properties have already been reported for a diverse family of Ln-based inorganic–organic hybrids. Here we present an account of the recent developments in the field of Ln-based inorganic–organic upconverting materials and their emerging applications

Upconversion Properties of Nanocrystalline ZrO 2 :Yb 3+ , Er 3+ Phosphors

Combustion and sol-gel methods were used to prepare the upconverting nanocrystalline ZrO 2 :Yb 3+ ,Er 3+ phosphors. The crystal structure was studied by X-ray powder diffraction and the crystallite sizes were estimated with the Scherrer formula. Impurities and nanomaterials&apos; thermal degradation were analyzed with FT-IR spectroscopy and thermal analysis, respectively. Upconversion luminescence and luminescence decays were studied with IR-laser excitation at 977 nm. All nanomaterials possessed the cubic ZrO 2 fluorite-type structure except for a small monoclinic impurity obtained with the sol-gel method. The conventional NO − 3 and OH − impurities were observed for the combustion synthesis products. The ZrO 2 :Yb 3 ,Er 3+ nanomaterials showed red (630-710 nm) and green (510-570 nm) upconversion luminescence due to the 4 F 9/2 → 4 I 15/2 and ( 2 H 11/2 , 4 S 3/2 ) → 4 I 15/2 transitions of Er 3+ , respectively. The products of the combustion synthesis exhibited the most intense luminescence intensity and showed considerable afterglow. It was concluded that excitation energy is partially trapped in the system and subsequently bleached thermally to the luminescent Er 3+ center to yield &quot;persistent upconversion&quot;

Advances in upconversion enhanced solar cell performance

AbstractPhotovoltaics (PV) is the leading renewable energy harvesting technology. Thus, there is a remarkable strive to enhance the light harvesting capability of the state-of-the-art solar cells. The major issue common to all solar cell types is that they utilize only a limited portion of the solar spectrum, mostly in the visible range, as the active semiconductor materials suffer from intrinsic light absorption thresholds. As a result, photons below and above these threshold values do not contribute to the electricity generation. A plausible solution to enhance the performance is to integrate the PV cell with an upconverting (UC) component capable of harvesting lower energy photons in the infrared (IR) range and emitting visible light. The concept was first introduced in 1990s, but major progress in the field has been made in particular in the recent few years. In this overview our intention is to provide the readers with a comprehensive account of the progress in the research on the UC-enhanced solar cells. Lanthanide ions embedded in different host lattices constitute the most important UC material family relevant to the PV technology; we first summarize the design principles and fabrication routes of these materials. Then discussed are the different approaches taken to integrate the UC layers in actual PV device configurations. Finally, we will highlight the most prominent results obtained, give some future perspectives and outline the remaining challenges in this scientifically intriguing and application-wise important field.</p

Preparation of glass-based composites with green upconversion and persistent luminescence using modified direct doping method

AbstractNew oxyfluorophosphate glass-based composites which exhibit not only green upconversion under 980 nm pumping but also green persistent luminescence (PeL) after being UV charged were successfully prepared using the direct doping method. The composites are composed of a glass-ceramic with Er3+ doped CaF2 crystals and of the persistent luminescent particles with the SrAl2O4:Eu,Dy composition. In the standard direct doping method, the glass melt is quenched few minutes after adding the PeL particles in the melt held at a temperature lower than the melting temperature. It is demonstrated that the direct doping method should be modified when preparing oxyfluoride glasses with PeL particles to limit not only the decomposition of the PeL particles in the glass but also the fluorine evaporation occurring during the glass preparation. Here, the composites were prepared by quenching the melt right after adding the PeL particles. The modified direct doping method allows the preparation of glass-based composites with strong green upconversion and homogeneous green persistent luminescence.</p