9th annual matsurf seminar - utu · olle eriksson is the head of materials theory at uppsala ... p....
TRANSCRIPT
Turku University Centre for Materials and Surfaces(www.matsurf.utu.fi)
9th ANNUAL MATSURF SEMINAR
DEPARTMENT OF PHYSICS AND ASTRONOMY
QUANTUM AUDITORIUM
NOVEMBER 09, 2015
09.00 Opening of the seminar: Vice-Rector Prof. Kalle-Antti Suominen
09.05 Prof. Kurt Gloos
What is MatSurf?
09.10 Invited lecture: Prof. Maarit Karppinen (Aalto University, Helsinki)
Atomic/molecular layer-engineered inorganic-organic hybrid materials: from
fundamentals to energy applications
10.00 Hellen Santos (Laboratory of Materials Chemistry and Chemical Analysis)
Luminescent Non-Doped Laponites: Anionic Layered Nanosilicates
10.20 Coffee break
10.50 Bhushan Gadgil (Laboratory of Materials Chemistry and Chemical Analysis)
Viologen Based Electroactive Materials for Smart Electrochromic Windows
11.10 Invited lecture: Prof. Jesper Nygård (University of Copenhagen)
Advanced III-V nanowire designs: superconductor-semiconductor heterostructures
for quantum electronics and vertical arrays for cell biology
12.00 Lunch break
13.00 Minnamari Saloaro (Wihuri Physical Laboratory)
Improving Sr2FeMoO6 thin films towards spintronic applications
13.25 Marjukka Tuominen (Materials Research Laboratory)
Oxidized crystalline (3×1)-O surface phases of InAs and InSb studied by high-
resolution photoelectron spectroscopy
14.00 Invited lecture: Prof. Olle Eriksson (University of Uppsala)
Modeling of materials, what can and can’t be done
14.50 Oral poster presentation (max 2 minutes one slide / poster)
15.20 Poster session (open end with snacks and trinks). SPEAKERS
Prof. Maarit KarppinenMaarit Karppinen received her PhD in inorganic chemistry in 1993from Helsinki University of Technology. Currently she is a professorof inorganic chemistry and deputy head of Department of Chemistryat Aalto University in Finland. Before establishing her researchgroup at Aalto University in 2006, she was holding a regularassociate professor chair at Tokyo Institute of Technology for 5years. For 2009-2013 she was holding the academy professor statusin Finland. She is best known for her research on functional oxidematerials (both bulk and thin films) for the next-generation energyand nanotechnologies, including material categories such as high-Tcsuperconductors, thermoelectrics, multiferroics, halfmetals forspintronics, ionic conductors for fuel cells, batteries, oxygen storage,etc. Currently the research focus covers also nanocomposite materialswhere inorganics are combined down to molecular-level precisionwith e.g. organic molecules, polymers, biomaterials, nanotubes andgraphene sheets for novel thin-film structures and 3D architectures.In 2013 she received the European Research Council (ERC)Advanced Grant for her research on atomic/molecular layer-by-layer(ALD/MLD) deposited hybrid inorganic-organic thin-film materials.
Prof. Jesper NygårdJesper Nygård is professor of experimental physics at the NielsBohr Institute (NBI), University of Copenhagen. He heads theCondensed Matter Physics division and co-directs the Centerfor Quantum Devices and the Nano-Science Center.Since his PhD from NBI in 2000 Jesper Nygård’s research hasmainly focused on nanofabricated electronic devices, quantumtransport and novel materials. He has also been engaged in(unsuccessful) start-ups within biosensors and electronics. Hejoined the permanent faculty in 2003. 2005-08 he was one ofthe three Danish astronaut candidates for the European SpaceAgency.He is currently interested in hybrid electronic devicesincorporating superconducting elements andnanowires/nanotubes. His group grows the latter materials (byCVD and MBE), employs electron microscopy forcharacterization, designs submicron devices and performselectrical measurements at ultralow temperatures to reveal newquantum effects.
Prof. Olle ErikssonOlle Eriksson is the head of Materials Theory at UppsalaUniversity. His expertise lies in first principles electronicstructure theory and its application to materials. This involvesdevelopment and use of: electronic structure methods, theory ofmagnetic anisotropy, statistical methods such as Monte Carloand spin dynamics simulations, theoretical models for excitedstate properties, complex magnetism and correlated electronicstructure. He has published some 550 peer reviewed papers,and one scientific monograph.
LIST OF ABSTRACTS / POSTERS
Atomic/molecular layer-engineered inorganic-organic hybrid materials:from fundamentals to energy applications
Maarit KarppinenDepartment of Chemistry, Aalto University, Finland
On-demand-designed materials with extraordinary combinations of properties are in the forefront ofmaterials chemistry research. Hybrid inorganic-organic materials have the capacity– once carefullydesigned and fabricated – to exhibit tailored combinations of properties traditionally seen forinorganics or organics separately. An elegant, yet industrially feasible way to link the inorganic andorganic entities via strong chemical bonds to form coherent single-phase 2D hybrid materials is tomimic the state-of-the-art gas-phase thin-film deposition technique, ALD (Atomic Layer Deposition),originally developed to deposit high-quality thin films of simple inorganic materials. For theinorganic-organic hybrids, ALD cycles are combined with MLD (Molecular Layer Deposition) cyclesbased on organic precursors. This enables the atomic/molecular layer-by-layer production ofinorganic-organic hybrid thin films through sequential self-limiting gas-surface reactions with highprecision for the film thickness and composition.1
In this talk I will discuss our recent efforts towards synthesizing new functional materials by thecombined ALD/MLD technique.1,2 In particular, we have fabricated oxide-organic thin-filmsuperlattices in which the periodically introduced single/thin organic layers between oxide layersare e.g. shown to hinder phonon transport and enhance the thermoelectric properties of (Zn,Al)O3,4
and (Ti,Nb)O25 films, and to sensitize TiO2 films to visible light.6 Also discussed are the new
directions foreseen related e.g. to photoluminescence materials,7 Li-ion microbattery materials8,9
and so-called metal organic framework (MOF) materials.10
1. P. Sundberg & M. Karppinen, Organic and inorganic-organic thin film structures by molecular layerdeposition: A review, Beilstein J. Nanotechnol. 5, 1104 (2014).
2. A.J. Karttunen, T. Tynell & M. Karppinen, Atomic-level structural and electronic properties of hybridinorganic-organic ZnO:hydroquinone superlattices fabricated by ALD/MLD, J. Phys. Chem. C 119,13105 (2015).
3. T. Tynell, I. Terasaki, H. Yamauchi & M. Karppinen, Thermoelectric characteristics of (Zn,Al)O /hydroquinone superlattices, J. Mater. Chem. A 1, 13619 (2013).
4. T. Tynell, A. Giri, J. Gaskins, P.E. Hopkins, P. Mele, K. Miyazaki & M. Karppinen, Efficientlysuppressed thermal conductivity in ZnO thin films via periodic introduction of organic layers, J. Mater.Chem. A 2, 12150 (2014).
5. J.-P. Niemelä, A, Giri, P.E. Hopkins & M. Karppinen, Ultra-low thermal conductivity in TiO2:Csuperlattices, J. Mater. Chem. A 3, 11527 (2015).
6. J.-P. Niemelä & M. Karppinen, Tunable optical properties for hybrid inorganic-organic [(TiO2)m(Ti-O-C6H4-O-)k]n superlattice thin films, Dalton Transact. 44, 591 (2015).
7. Z. Giedraityte, P. Sundberg & M. Karppinen, Flexible inorganic-organic thin-film phosphors byALD/MLD, J. Mater. Chem. C, submitted (2015).
8. M. Nisula, Y. Shindo, H. Koga & M. Karppinen, Atomic layer deposition of lithium phosphorousoxynitride, Chem. Mater., in press (2015).
9. M. Nisula & M. Karppinen, Atomic/Molecular layer deposition of lithium terephthalate thin films ashigh rate capability Li-ion battery anodes, Adv. Energy Mater., submitted (2015).
10. E. Ahvenniemi & M. Karppinen, Atomic/molecular layer deposition: a direct gas-phase route tocrystalline metal-organic framework thin films, Chem. Commun., submitted (2015).
Luminescent Non-Doped Laponites: Anionic Layered Nanosilicates
Hellen S. Santos1,2*, Mika Lastusaari1,3, Tero Laihinen1,2, Antti Viinikanoja1,
Hermi F. Brito4, Lucas C.V. Rodrigues4, Hendrik C. Swart5 and Jorma Hölsä1,3,4,5
1Department of Chemistry, University of Turku, FI-20014 Turku, Finland
2Doctoral Programme in Physical and Chemical Sciences, University of Turku Graduate School
(UTUGS), Turku, Finland 3Turku University Centre for Materials and Surfaces (MatSurf), FI-20014 Turku, Finland
4Instituto de Química, Universidade de São Paulo, BR-05508-000 São Paulo-SP, Brazil
5Department of Physics, University of the Free State, Bloemfontein ZA-9300, Republic of South Africa
Layered silicates (LS) such as hectorite clays have been used as host matrices for optically functional species due to their tunable structure. Laponite is a synthetic clay that belongs to the hectorite family. It has the composition Na0.7(Si8Mg5.5Li0.3)O20(OH)4. Its layered structure can be coated onto a variety of substrates through facile self-assembly from aqueous phases [1, 2]. Luminescence has been reported for several LS doped with rare earths, mainly Eu3+ [1-4]. However, the OH- ions in the laponite structure quench luminescence efficiently. In the present work, new classes of layered silicates based on the laponite structure were synthesized by replacing OH- with Cl- or F- to avoid quenching.
The XPD patterns showed
that all LS have the same
structure consistent with the
fluorohectorite pattern. All
reflections were broad
indicating nanoscale
crystallites. The FTIR spectra
indicated water outside the
layers (3600-3630 and 1610-
1650 cm-1) [5] as well as the
formation of Si-Cl bonds (470-
550) [6] and [ClSiO1,5]x T units
(1000-1160 cm-1) [7] in LS(Cl-).
No signal was found
compatible with the formation
of Si-F bonds or presence of
water in LS(F-). For all samples, the Si-O-Si bending vibrations were observed at
1010-1090 cm-1 [6]. The luminescence measurements of non-doped LS show strong
wide band emission between 320 and 660 nm and a weaker red/NIR emission (Fig.).
This is the first time that such an emission has been reported for laponite.
References 1. J. Tronto et al., Mater. Chem. Phys. 113, 71 (2009). 2. N. Finck et al., J. Contam. Hydrol. 102, 253 (2008). 3. S. Ryu et al., Appl. Clay Sci. 101, 52 (2014). 4. M.M. Lezhnina et al., Opt. Mater. 33, 1471 (2011). 5. L. Wen-Xin et al., J. Environ. Sci. 15, 456 (2003). 6. G. Socrates, Infrared and Raman Characteristic Group Frequencies, 3
nd ed., 244 (1994).
7. B. Arkles et al., Silicone Compounds Register and Review, Petrarch Systems, 2nd
ed., 101 (1987).
Fig. Luminescence spectra of all LS materials.
300 400 500 600 700 8000
200
400
600
800
1000
Na0.7
(Si8Mg
5.5Li
0.3)O
20X
4
Wavelength / nm
Inte
nsity /
Arb
. U
nits
exc: 255 nm
293 K
Delay 0.1 ms
Gate 10 ms
12 h @ 200 oC
X: F, reflux: 24 h, basic
F, 24 h, neutral
Cl, 48 h, basic
Cl, 22 h, neutral
Viologen Based Electroactive Materials for Smart Electrochromic Windows
Bhushan Gadgila,b, Pia Damlina, Carita Kvarnströma
a Turku University Centre for Materials and Surfaces (MATSURF), Laboratory of Materials Chemistry andChemical Analysis, FI-20014, University of Turku, Finland
a University of Turku Graduate School (UTUGS), Turku, Finland
Abstract: Electrochromic materials have the property of a change of color as effected either by an electron
transfer (redox) process or by a sufficient electrochemical potential. The main classes of electrochromic
materials are the metal oxides, conjugated polymers, metal coordination complexes and the viologens.
Successful applications of electrochromic materials in devices include anti-glare windows in aircraft and
buildings, electrochromic sunglasses, switchable mirrors, camouflage materials, chameleonic fabrics, spacecraft
thermal control, an optical iris for a camera lens and light-reflective/transmissive display devices.
In our group, we develop unique viologen/polyviologen based materials, conjugated polymers with viologen
functionality and viologen-graphene composites. The viologen is synthesized from cyanopyridinium ion based
monomer precursor and reductive electropolymerization method is used to obtain an electroactive thin film
directly on the conducting substrate. The as deposited film is thoroughly characterized by different spectral,
surface and electrochemical techniques. The films are further subjected to continuous potential
charging/discharging cycles to monitor the color/bleach characteristics and long term stability. We show that the
viologen based electroactive films possess conducing properties when attached to conjugated polymers like
polythiophenes. Moreover, the electrochrome stability is better when a composite is made with graphene, in
comparison to pristine viologen/polyviologen system. Such assemblies based on electrochromic viologens would
be a valuable alternative to the conventional materials for smart windows.
References:[1] Gadgil, B., Dmitrieva, E., Damlin, P., Ääritalo, T.; Kvarnström, C. J. Solid State Electrochem. 2015, 19, 77-83.[2] Gadgil, B., Damlin, P., Ääritalo, T.; Kvarnström, C. RSC adv. 2015, 5, 42242[3] Gadgil, B., Damlin, P., Heinonen, M.; Kvarnström, C. Carbon 2015, 89, 53-62.
Advanced III-V nanowire designs: superconductor-semiconductor heterostructures for quantum
electronics and vertical arrays for cell biology
Jesper Nygård Center for Quantum Devices & Nano-Science Center Niels Bohr Institute, University of Copenhagen, [email protected], qdev.dk Molecular beam epitaxy (MBE) is well suited for manufacture of highly refined nanowire materials. In the spirit of the interdisciplinary MatSurf meeting, we will review two recent examples where careful design of the MBE grown III-V nanowires has enabled widely different studies of nanoscale superconductors and in-vitro cell biology, respectively.
We present results on epitaxial growth of semiconductor-superconductor core-shell nanowires, composed of InAs/Al, which form epitaxially matched single plane interfaces. The method provides a new route to electrical contacting of nanowires and specialized applications such as tunable superconducting electronics, quantum bits and topological superconductors. The latter is a key element in the formation of Majorana quasiparticles.
Arrays of vertical nanowires have recently emerged as an attractive platform for manipulating and probing live cells with prospects for intracellular sensing, cell guidance etc. Here, large regular nanowire arrays are needed, and the precise nanowire dimensions (density, diameter, length) turn out to be crucial for understanding the interface between cells and the nanostructured substrate. Recent work has elucidated how the optical properties of nanowires can be exploited for high resolution fluorescent imaging.
Array of InAs nanowires Epitaxial superconductor/ semiconductor interface in hybrid nanowires (Al/InAs)
Biological cells cultured on nanowire forest
These materials have been developed by several co-workers at the University of Copenhagen, in particular Jessica Bolinsson, Thomas Sand Jespersen, Peter Krogstrup, Caroline Lindberg, Morten H. Madsen and Claus Sørensen. The applications of the materials have been investigated in collaboration with colleagues at the Center for Quantum Devices, Niels Bohr Institute (Charles Marcus and co-workers) and the Nanobiotechnology laboratory, Nano-Science Center (Karen Martinez and co-workers).
Selected recent references:
“Hard Gap in Epitaxial Superconductor-Semiconductor Nanowires”, W. Chang, S.M. Albrecht, T.S. Jespersen, F. Kuemmeth, P. Krogstrup, J. Nygard, and C. M. Marcus, Nature Physics 10, 232 (2015)
“Epitaxy of semiconductor-superconductor nanowires”, Peter Krogstrup, N.L.B. Ziino, W. Chang, S.M. Albrecht, M.H. Madsen, E. Johnson, J. Nygård, C.M. Marcus and T.S. Jespersen, Nature Materials 14, 400 (2015)
“Parity lifetime of bound states in a proximitized semiconductor nanowire”, A.P. Higginbotham, S. M. Albrecht, G. Kiršanskas, W. Chang, F. Kuemmeth, P. Krogstrup, T. S. Jespersen, J. Nygård, K. Flensberg & C. M. Marcus, Nature Physics (2015)
"Modulation of Fluorescence Signals from Biomolecules along Nanowires Due to Interaction of Light with Oriented Nanostructures", R. Frederiksen, E. Alarcon-Llado, M.H. Madsen, K.R. Rostgaard, P. Krogstrup, T. Vosch, J. Nygard, A.F.i. Morral, K.L. Martinez, Nano Letters 15, 176 (2015)
"Towards a Better Prediction of Cell Settling on Nanostructure Arrays - Simple Means to Complicated Ends", N. Buch-Manson, S. Bonde, J. Bolinsson, T. Berthing, J. Nygard, K.L. Martinez, ADVANCED FUNCTIONAL MATERIALS 25, 3246 (2015)
Improving Sr2FeMoO6 thin films towards spintronic applications
Minnamari Saloaro1, Martin Hoffmann2,3, Waheed A. Adeagbo2, Sari Granroth4, Hakan Deniz3,Heikki Palonen1, Hannu Huhtinen1, Sayani Majumdar1,5, Pekka Laukkanen4, Wolfram Hergert2,
Arthur Ernst3 and Petriina Paturi1
1 Wihuri Physical Laboratory, Department of Physics and Astronomy, University of Turku, Finland2 Institut für Physik, Martin Luther University Halle-Wittenberg, Germany
3 Max Planck Institute of Microstructure Physics, Halle, Germany4Materials Research Laboratory, Department of Physics and Astronomy, University of Turku, Finland
5NanoSpin, Department of Applied Physics, Aalto University School of Science, Finland
The double perovskite Sr2FeMoO6 (SFMO) has a high potential for novel spintronic and magneto-resistive sensor applications. With high Curie temperature, TC around 410-450 K, it possesses a highspin polarization and a large magnetoresistance even at room temperature. In order to use SFMO inmultilayer devices it is essential to have high quality thin films with best magnetic and electricalproperties. However, the fabrication of the SFMO thin films is difficult and the desirable magneticproperties are weakened from the polycrystalline bulk and powder samples. The challenges in thefabrication of SFMO films are the extreme preparation conditions and easily formed defects likeimpurity phases, oxygen vacancies and anti-site disorder (ASD), in which the Fe and Mo ions aretransposed. Also, a substrate induced strain caused by the lattice mismatch between the substrateand the grown material is always affecting the properties of the thin films. To obtain high qualitySFMO thin films for novel applications, it is necessary to clarify the mechanisms behind thedeteriorated properties. The role of lattice mismatch induced defects, strain, ASD and oxygenvacancies were investigated with various experiments and compared with theoretical calculations.The key towards higher Tc in SFMO thin films was found to be the reduction of ASD together withthe increased number of oxygen vacancies.
Oxidized crystalline (3×1)-O surface phases of InAsand InSb studied by high-resolution photoelectron
spectroscopy
Marjukka Tuominen1, Jouko Lång1, Johnny Dahl1, Mikhail Kuzmin1,2,Muhammad Yasir1, Jaakko Mäkelä1, Jacek Osiecki3, Karina Schulte3,
Marko Punkkinen1, Pekka Laukkanen1, and Kalevi Kokko1
1 Department of Physics and Astronomy, University of Turku, FI-20014 Turku, Finland2 Ioffe Physical-Technical Institute, Russian Academy of Sciences,
St. Petersburg 194021, Russian Federation3 The MAX IV Laboratory, Lund University, P.O. Box 118, SE-221 Lund, Sweden
ABSTRACT
Atomic scale knowledge of the properties of oxidized III-V semiconductor layers isimportant not only in understanding the fundamental process of semiconductor oxidation butalso in engineering materials for III-V nano-electronics, since surfaces and interfaces formsuch an essential part of the device materials. However, the oxidized semiconductor layersare usually buried and amorphous, so it is not straightforward to investigate and control theirproperties with atomic resolution. The crystalline (3×1)-O structure on InAs and InSb belongsto the family of recently discovered crystalline oxidized III-V surfaces,1 which provide well-defined templates to study III-V oxidation in general. In particular, the (3×1)-O surface phasehas turned out to be of great interest, because it enhances the performance of nano-electronics devices in practice. The pre-oxidized crystalline (3×1)-O structure on InAs(100)has been found to significantly improve insulator/InAs junctions for devices like III-V metal-oxide-semiconductor field-effect transistors.2,3
Still, the formation and atomic structure of the beneficial oxide layer are not wellunderstood. Our study reveals different atomic sites and bonding environments for the(3×1)-O structure on InAs(100) and InSb(100) based on synchrotron radiation photoelectronspectroscopy experiments.4 The formation mechanisms of the structure are also elucidated.Findings suggest a two-fold oxidation process: (i) oxygen atoms diffusing to the crystalsubstitute group V atoms and (ii) the relieved group V atoms become oxidized on thesurface. This analysis provides not only valuable information for developing insulator/III-Vjunctions further, but also a stringent test for the atomic model of the (3×1)-O surfacereconstruction in future.
REFERENCES
1. M. P. J. Punkkinen, P. Laukkanen, J. Lång, M. Kuzmin, M. Tuominen, V. Tuominen, J. Dahl, M. Pessa, M. Guina, K. Kokko, J. Sadowski, B. Johansson, I. J. Väyrynen, and L. Vitos, ” Oxidized In-containing III-V(100) surfaces: Formation of crystalline oxide films and semiconductor-oxide interfaces”, Phys. Rev. B 83, 195329 (2011)2. C. H. Wang, S. W. Wang, G. Doornbos, G. Astromskas, K. Bhuwalka, R. Contreras-Guerrero, M. Edirisooriya, J. S. Rojas-Ramirez, G. Vellianitis, R. Oxland, M. C. Holland, C. H. Hsieh, P. Ramvall, E. Lind, W. C. Hsu, L.-E. Wernersson, R. Droopad, M. Passlack, and C. H. Diaz, “InAs hole inversion and bandgap interface state density of 2 × 1011 cm-2eV-1 at HfO2/InAs interfaces”, Appl. Phys. Letters 103, 143510 (2013).3. M. Passlack, S.-W. Wang, G. Doornbos, C.-H. Wang, R. Contreras-Guerrero, M. Edirisooriya, J. Rojas-Ramirez, C.-H. Hsieh, R. Droopad, and C. H. Diaz, “Lifting the off-state bandgap limit in InAs channel metal-oxide-semiconductor heterostructures of nanometer dimensions” Appl. Phys. Letters 104, 223501 (2014).4. M. Tuominen, J. Lång, J. Dahl, M. Kuzmin, M. Yasir, J. Mäkelä, J. R. Osiecki, K. Schulte, M. P. J. Punkkinen, P. Laukkanen, and K. Kokko, “Oxidized crystalline (3×1)-O surface phases of InAs and InSb studied by high-resolution photoelectron spectroscopy”, Appl. Phys. Letters 106, 011606 (2015).
Olle Eriksson
Department of Physics and AstronomyUppsala [email protected]
Modeling of materials, what can and can’t be done
In this presentation I will make a short review of the basic ideas behind electronic structure theory, leading both to the ‘conventional’ description of essentially non-correlated electronic structures, as well as to correlated electron systems where dynamical mean field theory is an important recently developed tool. Examples of how these theories perform in reproducing materials will be primarily given from the group of magnetic compounds, where recent energy relevant applications concern e.g. magnetocalorics and rare-earth free permanent magnets. Special attention will be given to the dynamics of magnetic materials, using an atomistic spin-dynamics method that is coupled to electronic structure theory via a multi-scale approach.
ABSTRACTS - POSTERS
01 Thickness dependent properties of Sr2FeMoO6 thin films grown on SrTiO3 and (LaAlO3)0.3(Sr2AlTaO6)0.7 substratesI. Angervo, M. Saloaro, H. Palonen, S. Majumdar, H. Huhtinen, P. Paturi
02 Cationic thiouronium-polythiophene spectroscopic and electrochemical propertiesSergio E. Domínguez, Timo Ääritalo, Pia Damlin, Carita Kvarnström
03 MAGNETOPHOTORESISTANCE IN Pr1−xCaxMnO3 THIN FILMSTomi Elovaara, S.Majumdar, H. Huhtinen, P. Paturi
04 Characterization of porous silicon nanoparticles in biologically relevant mediaM. Kaasalainen, E. Mäkilä, S.-M. Alatalo, E. Arasola, M. Sillanpää, J. Salonen
05 An exact differential equation for the Pauli potentialH. Levämäki, A. Nagy, K. Kokko, L. Vitos
06 Thickness dependent properties of YBCO films grown on CLO/GZO buffered NiW substratesM. Malmivirta, H. Huhtinen, Y. Zhao, J.-C. Grivel, P. Paturi
07 Effects of mesoscale confinement on indomethacin adsorbed into porous siliconErmei Mäkilä, Henri Kivelä, Hélder A. Santos, Jarno Salonen
08 PERSISTENT LUMINESCENCE AND TENEBRESCENCE IN Na8Al6Si6O24(Cl,S)2
Isabella Norrbo, Pawel Gluchowski, Fikret Mamedov, Petriina Paturi, Jari Sinkkonen, Mika Lastusaari
09 SOLVOTHERMAL SYNTHESIS IN PREPARING NaYF4:Yb3+,Er3+ UPCONVERSION NANOMATERIALSEmilia Palo, Laura Pihlgren, Minnea Tuomisto, Tero Laihinen, Iko Hyppänen, Jouko Kankare, Mika Lastusaari, Tero Soukka, Hendrik C. Swart, Jorma Hölsä
10 Graphene oxide sample support improves image contrast and resolutionin low voltage transmission electron microscopyM. Peurla, P. Kunnas, J. Kauppila, A. Viinikanoja, S. Haataja, R. M. Latonen, P. Bober, C. Xu, J. Liu, L. J. Pelliniemi, C. Kvarnström
11 ELECTROPOLYMERIZATION OF CONDUCTING POLYMER-GRAPHENE COMPOSITE FILMMilla Suominen, Pia Damlin, Suvi Lehtimäki, Sampo Tuukkanen, Donald Lupo, Carita Kvarnström
12 The low-temperature magnetostructure and magnetic field response of Pr0.9Ca0.1MnO3: The roles of Pr spins and magnetic phase separationJ. Tikkanen, M. Geilhufe, M. Frontzek, W. Hergert, A. Ernst, P. Paturi, L. Udby
13 ENHANCEMENT OF THE UP-CONVERSION LUMINESCENCE FROM NaYF4:Yb3+,Er3+ THROUGH CHROMIUM CO-DOPINGMinnea Tuomisto, Emilia Palo, Tero Laihinen, Iko Hyppänen, Mika Lastusaari, Hendrik C. Swart, Jorma Hölsä
14 Electrochemical Synthesis and Characterization of PolyviologensNianxing Wang, Anniina Kähkönen, Timo Ääritalo, Pia Damlin, Jouko Kankare, Carita Kvarnström
15 Synthesis and properties of crystalline thin film of antimony trioxideon the Si(100) substrateM. Yasir, M. Kuzmin, M.P.J. Punkkinen, J. Mäkelä, M. Tuominen, J. Dahl, P. Laukkanen, K. Kokko
Thickness dependent properties of Sr2FeMoO6 thin films grown on SrTiO3 and (LaAlO3)0.3(Sr2AlTaO6)0.7 substrates
I. Angervo (1), M. Saloaro (1), H. Palonen (1), S. Majumdar(1, 2), H. Huhtinen (1) and P. Paturi (1)
1. Wihuri Physical Laboratory, Department of Physics and Astronomy, University of Turku, Finland2. NanoSpin, Department of Applied Physics, Aalto University School of Science, Finland
Sr2FeMoO6 (SFMO), with high Curie temperature around 410 K-450 K, high spin polarization and large intrinsic magnetoresistance, is a valuable candidate for future spintronic and magnetoresistive applications. However, fabrication of SFMO thin films, which are necessary considering applications, is delicate process and qualities of SFMO thin films are worse than polycrystalline samples. One of the important parameters in thin film fabrication are film thickness and the substrate material. Using pulsed laser deposition (PLD), series of SFMO thin films with different thicknesses were fabricated on SrTiO3 (STO) and (LaAlO3)0.3(Sr2AlTaO6)0.7 (LSAT). These substrates have different lattice mismatches with SFMO (-1.05% and -1.88%, respectively). Thickness was controlled during the PLD fabrication with the number of laser pulses, numbers ranging from 500 to 10 000 pulses on different films. X-ray characterization shows that thin films are phase pure and c-axis oriented. Despite the differences in strain, magnetic properties showed similar tendency on both substrates. The saturation magnetization and Curie temperature increased until pulse number around of 2000 was reached. Semiconducting low temperature upturn in resistivity was observed in all films and it was enhanced in the thinnest films. This suggests that band gap energy increases with increasing film thickness. According to these results, pulse number of 2000 results in high quality thin films and with higher pulse numbers the properties of SFMO thin films remain close to a constant value.
Cationic thiouronium-polythiophene spectroscopic and electrochemicalproperties
Sergio E. Domínguez, Timo Ääritalo, Pia Damlin, Carita Kvarnström
Turku University Centre of Materials and Surfaces (MatSurf), Laboratory of Materials Chemistryand Chemical Analysis, University of Turku, Vatselankatu 2, 20014 Turku, Finland
*corresponding. [email protected]
Conjugated polyelectrolytes (CPEs) are hydrophilic organic semiconducting polymers containing abase structure of alternating single and double/triple bonds. Because of their solubility and alsofluorescent and semiconducting properties, these molecules offer a wide spectrum of possibleapplications, such as optoelectronic [1] and fluorescence-based sensing [2].
This contribution shows our current spectroscopic and electrochemical research, mainly focused ontwo homologous cationic thiophene-based CPEs, (poly-3-(N-N-diethyl-S-iso-thiouronium)alkoxy-4-methyl thiophene), with different chain length in the alkoxy group (i.e. “spacer group”) at the 3 rd
position of the thiophene ring (see Figure).
Figure. a) Poly-3-(N-N-diethyl-S-iso-thiouronium)ethyloxy-4-methylthiophene; b) Poly-3-(N-N-diethyl-S-iso-thiouronium)hexyloxy-4-methylthiophene
REFERENCES[1] Lee, W. et al. (2013). “Conjugated polyelectrolytes: A new class of semiconducting material fororganic electronic devices”. Polymer, 54, 5104-5121.[2] Minami, T., and Kubo, Y. (2010). “Fluorescence Sensing of Phytate in Water Using anIsothiouronium-attached Polythiophene”, Chem. Asian J. 2010, 5, 605-611.
Matsurf - Centre of Materials and Surfaces
9. November 2015 - Turku, Finland
MAGNETOPHOTORESISTANCE IN Pr1−xCaxMnO3
THIN FILMS
•Tomi Elovaara 1 S. Majumdar 1,2 H. Huhtinen 1 P. Paturi 1
1University of Turku, Department of Physi s and Astronomy, FI-20014 Turku, Finland
2Aalto University S hool of S ien e, P.O. Box 15100, FI-00076 Aalto, Finland
The olossal magnetoresistive insulator to metal swit hing of almost nine orders of
magnitude under the signi� antly redu ed magneti �eld is a hieved by illumination for the
low bandwidth manganite thin �lms. Similarly, by hanging the measuring bias voltage
through the sample the required magneti �eld for insulator-metal transition an be further
�ne-tuned. By applying a magneti �eld of suitable strength, the samples an also be
tuned to be extra sensitive to the illumination having olossal e�e t on the resistivity at
low temperatures. This kind of utilizing of multiple external stimulants, whi h together
hange the properties of the material ould have signi� ant impa t on the new generation
of phase- hange memories working under a�ordable onditions.
• tomi.elovaara�utu.fi
Characterization of porous silicon nanoparticles in biologically relevant
media
M. Kaasalainen, E. Mäkilä, S.-M. Alatalo, E. Arasola, M. Sillanpää and J. Salonen
Department of Physics and Astronomy, University of Turku, Finland
Laboratory of Green Chemistry, Lappeenranta University of Technology, Finland
Email: [email protected]
The study of porous silicon (PSi) for biological applications started in 1995 when Leigh
Canham discovered its biocompatibility [1]. It was soon noticed that PSi degrades in biological
environment into silicic acid which is the most natural form of silicon found in plants and
animals. For many animals, including human, silicic acid is an essential micronutrient
associated with bone mineralization, collagen synthesis and health of skin, hair and nails [2].
More recently, highly promising results considering the use of PSi nanoparticles in biological
applications have been published.
One of these applications is the use of PSi nanoparticles as a peptide delivery system [3].
Peptide-based drugs, in general, suffer low chemical stability and poor penetration through
biological barriers which are the reasons for administration through frequent injections [4].
Mesoporous nanoparticles could provide protecting container and controlled release for these
molecules.
The benefit of porous silicon as a nanomedical drug delivery device is the easy adjustability of
surface chemistry. As a nanostructured material, it has large surface area so the surface
chemistry is one of the key properties behind almost every biologically relevant characteristics.
These are, for example, zeta potential, hydrophobicity and biodegradation. The proper
characterization of these basic properties is of importance in first place when the formulation
is designed [5] and the certain functionality is tried to add to the drug delivery system [6], but
also when trying to predict the interactions of nanoparticles with biological systems.
In this study, the particle interaction with isotonic medium and therapeutic peptide as well as
the degradation in biologically relevant media is studied in order to understand the behavior of
formulation designed for subcutaneous peptide injection.
References [1] L. T. Canham, Adv. Mater. 7, 1033 (1995).
[2] L. M. Jurkic, I. Cepanec, S. K.Pavelic and K. Pavelic, Nutr. Metab. 10, 1743 (2013).
[3] M. Kovalainen, J. Mönkäre, M. Kaasalainen, J. Riikonen, V.-P. Lehto, J. Salonen, K.-H. Herzig
and K. Järvinen, Mol. Pharm. 10, 353 (2013).
[4] D. J. Craik, D. P. Fairlie, S. Liras and D. Price, Chem. Biol. Drug. Des. 81, 136 (2013).
[5] M. Kaasalainen, E. Mäkilä, J. Riikonen, M. Kovalainen, K. Järvinen, K.-H. Herzig, V.-P. Lehto
and J. Salonen, Int. J. Pharmaceut. 431, 230 (2012).
[6] M. Kaasalainen, J. Rytkönen, E. Mäkilä, A. Närvänen and J. Salonen, Langmuir, 31, 1722 (2015).
Thickness dependent properties of YBCO films grown onCLO/GZO buffered NiW substrates
M. Malmivirta,1,2,* H. Huhtinen,1 Y. Zhao,3,4 J.-C. Grivel3 and P. Paturi1
1Wihuri Physical Laboratory, Department of Physics and Astronomy,University of Turku, FI-20014 Turku, Finland
2University of Turku Graduate School (UTUGS), University of Turku, FI-20014, Finland
3Department of Energy Conversion and Storage, Technical University of Denmark,DK-4000 Roskilde, Denmark
4Department of Electrical Engineering, Shanghai JiaoTong University, 200240 Shanghai, China
*email: [email protected]
The properties of YBa2Cu3O7−δ (YBCO) thin films deposited on technical substrates can beenhanced by optimizing the buffer layers. The buffer affects remarkably the growth of YBCO,especially near the interface. To better understand the properties of YBCO films near the interfaceof the buffer layer, a series of pulsed laser deposited YBCO films with different thicknesses weremade. The films were deposited on high- quality biaxially textured NiW substrates with chemicalsolution deposited buffer layers: Gd2Zr2O7 barrier and Ce0.9La0.1O2 cap. The structuralcharacterizations using X-ray diffractometry and atomic force microscopy reveal increasing strainand surface roughness with film thickness. The films are well textured, mainly c-axis upwardsoriented. Additionally there are small components of 45° in-plane rotated grains both in c- and a-axis orientation. The critical current density, Jc , has the largest values at intermediate thicknesses,but the critical temperature is lowest for those samples. Although pulsed laser deposition is a goodmethod to probe the growth of the interface layer, the Jc values are much lower than on films madeusing chemical solution deposition.
A 50 x 50 μm AFM image of the buffered substrate showing NiW grainsbelow the buffer layers. The height profile at the red line is shown below the image.
A 50 x 50 μm AFM image of the 1 000 pulses sample. YBCO does not grow evenly on the substrate and the surfaceis rough.
Effects of mesoscale confinement on indomethacin adsorbed into porous silicon
Ermei Mäkilä1,2, Henri Kivelä3, Hélder A. Santos2, Jarno Salonen1
1Department of Physics and Astronomy, University of Turku, Finland
2Division of Pharmaceutical Chemistry and Technology, University of Helsinki
3Department of Chemistry, University of Turku
Adsorption of small molecules into mesoporous structures have been shown to induce formation of different phases within the pores [1]. The effects on the thermodynamic behaviour of the adsorbed molecules are closely related to the dimensions of the confinement and interactions taking place between the adsorbate and adsorbent. This appears as an e.g. gradual depression of the phase transition temperatures compared to nonconfined bulk forms [2]. In this study, the selected adsorbate molecule was indomethacin (IMC), an anti-analgesic drug with two known polymorphic forms. Thermally hydrocarbonized mesoporous silicon (THCPSi) was fabricated as the adsorbent. These choices provided a drug that has a tendency to form dimers or trimers through its different hydrogen bond acceptor and donor sites, while the pore walls of the adsorbent were terminated with –CHx groups, making the walls hydrophobic and reluctant to hydrogen bonding [3]. Differential scanning calorimetry (DSC) analysis indicated that confining the IMC molecules into pores with an average diameter of ca. 12 nm appeared to prevent nucleation of detectable amounts of partially crystalline IMC. Fourier transform infrared (FTIR) spectroscopic results showed IMC to also reside in a chemically similar state as the bulk amorphous form. Nuclear magnetic resonance spectroscopy studies confirmed the DSC and FTIR results. However, the spectra surrounding the IMC carbonyl and carboxyl carbon resonances indicated the possibility of hydrogen bonding in various configurations taking place within the pores. In contrast to drug molecules with strong interactions with the adsorbate surface, such as ibuprofen confined into mesoporous silica or oxidized silicon where both partial crystallization within pores can occur while the drug molecules still reside in a liquid-like state [1,4], confined IMC shows only limited, amorphous-like mobility with similar transverse relaxation durations [3]. These results show the behaviour of mesoscale confined IMC to follow the properties of bulk amorphous IMC, while benefiting from the physical nature of the confinement as the stabilizer of the amorphous state. References [1] T. Ukmar, T. Čendak, M. Mazaj, V. Kaučič, G. Mali, J. Phys. Chem. C, 116 2662 (2012). [2] C. Alba-Simionesco, B. Coasne, G. Dosseh, G. Dudziak, K.E. Gubbins, R. Radhakrishnan, M. Sliwinska-Bartkowiak, J. Phys. Condens. Matter, 18, R15 (2006). [3] E. Mäkilä, M. Ferreira, H. Kivelä, S. Niemi, A. Correia, M.-A. Shahbazi, J. Kauppila, J. Hirvonen, H.A. Santos, J. Salonen, Langmuir, 30, 2196 (2014). [4] J. Riikonen, E. Mäkilä, J. Salonen, V.-P. Lehto, Langmuir, 25 6137 (2009).
An exact differential equation for the Pauli potential
H. LevamakiDepartment of Physics and Astronomy, University of Turku, FI-20014 Turku, Finland, [email protected]
A. NagyDepartment of Theoretical Physics, University of Debrecen, H-4010 Debrecen, Hungary, [email protected]
K. KokkoDepartment of Physics and Astronomy, University of Turku, FI-20014 Turku, Finland.
L. VitosApplied Materials Physics, Department of Materials Science and Engineering, Royal Institute of Technology, Stock-holm SE-100 44, Sweden.Institute for Solid State Physics and Optics, Wigner Research Centre for Physics, Hungarian Academy of Sciences,P.O. Box 49, H-1525 Budapest, Hungary.Department of Physics and Astronomy, Division of Materials Theory, Uppsala University, Box 516, SE-75121 Uppsala,Sweden.
AbstractIt has been recently discovered that, for spherically symmetric systems, the exact Pauli potential (in the Kohn-Shamsense) can be calculated from a differential equation, which only involves the electron density and its derivatives[1, 2, 3]. This Pauli potential differential equation (PPDE) hence allows one to calculate the Kohn-Sham electronicstructure of a system without explicitly solving the Kohn-Sham equations. Orbital-free calculations for sphericallysymmetric systems at Kohn-Sham level of accuracy are therefore possible. In the PPDE approach the orbital-freeEuler equation is accompanied by the PPDE and together they form a system of two coupled differential equations.We show that this system is solvable in practice and numerical results for the Be atom are presented [4]. The obtainedelectronic structure and the energy components nearly perfectly agree with those derived from Kohn-Sham calculations.Generalisation of the PPDE approach for more complicated systems is in progress.
References[1] A. Nagy, Chem. Phys. Lett. 460, 343 (2008).
[2] A. Nagy, J. Chem. Phys. 135, 044106 (2011).
[3] Y. Wang and T. Wesolowski, Recent Progress in Orbital-free Density Functional Theory (WSPC, Hoboken, NewJersey, 2013).
[4] H. Levamaki, A. Nagy, K. Kokko, and L. Vitos, Phys. Rev. A (submitted).
Keywords: Pauli potential, orbital-free density functional theory,
1
PERSISTENT LUMINESCENCE AND TENEBRESCENCE IN Na8Al6Si6O24(Cl,S)2
Isabella Norrbo1*, Pawel Gluchowski2, Fikret Mamedov3, Petriina Paturi4,
Jari Sinkkonen1, Mika Lastusaari1,5
1University of Turku, Department of Chemistry, FI-20014 Turku, Finland
2Institute of Low Temperature and Structure Research Polish Academy of Sciences, PL-50422 Wroclaw, Poland
3Uppsala University, Department of Chemistry, SE-751 20 Uppsala, Sweden 4University of Turku, Department of Physics and Astronomy, Wihuri Physical Laboratory, FI-20014
Turku, Finland 5Turku Centre for Materials and Surfaces (MatSurf), Turku, Finland
Persistent luminescence is a phenomenon involving the sustained release of absorbed
energy as visible light after the removal of the excitation source. It is based on the
trapping of charge carriers and their slow release stimulated by thermal energy [1].
Tenebrescence is closely related to persistent luminescence, since it also involves the
trapping of charge carriers and their sustained release by thermal or optical energy.
The trapping of electrons creates a color center, which absorbs light until the electron
escapes from the trap as a result of thermal or optical stimulation [2].
Na8Al6Si6O24(Cl,S)2 materials have been reported to show both persistent
luminescence of one hour and tenebrescence lasting for two days [3]. In this work, the
persistent luminescence and tenebrescence in the Na8Al6Si6O24(Cl2,S) materials was
studied with photoluminescence (PL), thermoluminescence, solid state NMR, EPR as
well as persistent luminescence and tenebrescence excitation measurements
(Figure). The results and their implications are discussed.
Figure. Room temperature persistent luminescence, tenebrescence and photoluminescence excitation
spectra of Na8Al6Si6O24Cl1.6S0.10.2.
References
1. Hölsä, J., Electrochem. Soc. Interface 18(4) (2009) 42.
2. Medved, D.B., Amer. Mineral. 39 (1953) 615.
3. Norrbo, I., Gluchowski, P., Paturi, P., Sinkkonen, J., Lastusaari, M., Inorg. Chem.
54 (2015) 7717
200 250 300 350 400 450
0.0
0.2
0.4
0.6
0.8
1.0 Na8Al
6Si
6O
24(Cl
1.6S
0.1
0.2)
Re
lative
In
ten
sity
Wavelength / nm
Persistent lumin.
Excitation at RT
Tenebrescence
PL (em
= 480 nm)
6 5 4 3
Energy / eV
SOLVOTHERMAL SYNTHESIS IN PREPARING NaYF4:Yb3+,Er3+ UP-CONVERSION NANOMATERIALS
Emilia Palo1-3,*, Laura Pihlgren1, Minnea Tuomisto1-3, Tero Laihinen1-3, IkoHyppänen1,3, Jouko Kankare1,3, Mika Lastusaari1,3, Tero Soukka4, Hendrik C. Swart5
and Jorma Hölsä1,3,5
1University of Turku, Department of Chemistry, FI-20014 Turku, Finland2University of Turku Graduate School (UTUGS), Doctoral Programme in Physical and Chemical
Sciences, Turku, Finland3Turku University Centre for Materials and Surfaces (MatSurf), Turku, Finland
4University of Turku, Department of Biochemistry, FI-20014 Turku, Finland5University of the Free State, Department of Physics, Bloemfontein, Republic of South Africa, ZA9300
The up-conversion phosphors converting two or more low energy (near infra-red, NIR)photons to light or even UV radiation, have many potential applications e.g. in medicaldiagnostics [1]. The strongest up-conversion luminescence so far has been observedfrom the hexagonal NaYF4:Yb3+,Er3+ material. In this work, the solvothermal synthesiswas tested for obtaining NaYF4:Yb3+,Er3+ nanomaterials [2]. The effect of the reactiontemperature (140-185 °C) and reactor filling rate on the structure and up-conversionluminescence (λexc: 970 nm) was studied.
The X-ray powder diffraction patternsreveal both the cubic and hexagonalphases of NaYF4 and transmissionelectron microscopy (TEM) images show aset of nanoparticles (ca. 10-100 nm) thatare not very uniform in morphology. Theup-conversion luminescence spectra(Fig.) show red (640-685 nm; 4F9/2→4I15/2)and green (515-560 nm; 2H11/2, 4S3/2→4I15/2
transitions) Er3+ emissions. The strongestup-conversion luminescence is obtainedwith the NaYF4:Yb3+,Er3+ material heatedfor 8 h at 177 °C with 80 % filling rate dueto the hexagonal form, which is known tobe highly luminescent.
References1. Kuningas, K., Rantanen, T., Ukonaho, T., Lövgren, T. and Soukka, T., Anal. Chem. 77 (2005) 7348–7355.2. Chen, Z., Chen, H., Hu, H., Yu, M., Li, F., Zhang, Q., Zhou, Z., Yi, T. and Huang, C., J. Am. Chem. Soc. 130 (2008) 3023–3029.
Fig. Up-conversion luminescence spectraof the NaRF4 nanomaterial preparedwith selected reactor filling rates.
500 550 600 650 7000
100
200
300
4.4
4.6
4.8
Red
/Gre
enIn
tens
ityR
atio
5060
7080
Filling rate (%)
NaYF4:Yb3+,Er3+
Inte
nsity
/Arb
.Uni
ts
Wavelength / nm
4H11/2®4I15/2
5S3/2®4I15/2
4F9/2®4I15/2
xYb
: 0.20, xEr
: 0.028 h @ 177 °C295 Kl
exc: 970 nm
80 %
70
60
5080 %
50
Reactorfilling rate
Graphene oxide sample support improves image contrast and resolution in low voltage transmission electron microscopy
M. Peurlaa, P. Kunnasa, J. Kauppilab, A. Viinikanojab, S. Haatajac, R. M. Latonend, P. Bobere, C. Xuf, J. Liuf, L. J. Pelliniemia, C. Kvarnströmb
aLaboratory of Electron Microscopy, Department of Cell Biology and Anatomy, University of Turku, Finland bLaboratory of Materials Chemistry and Chemical Analysis, University of Turku, Finland cDepartment of Medical Biochemistry and Genetics, University of Turku, Finland dProcess Chemistry Centre, Laboratory of Analytical Chemistry, Åbo Akademi University, Turku, Finland eInstitute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic, Prague, Czech Republic fProcess Chemistry Centre, Laboratory of Wood and Paper Chemistry, Åbo Akademi University, Turku, Finland
Graphene oxide (GO) is nanometer thin sheet-like macromolecule that can have lateral dimensions up to several micrometers. Transparency for electron beam combined with low cost and easy solution based processing makes it very attractive sample supporting material for transmission electron microscopy (TEM). Main advantage of using an ultra-thin support is that use of heavy metal based staining methods (eg. uranyl acetate) can be avoided.
We demonstrate that use of graphene oxide (GO) sample support is crucial to get maximal image contrast improvement in low voltage transmission electron microscopy (LV-TEM) of unstained organic and biological specimens. TEM image contrast is improved up to 5-fold in images taken at 10 kV acceleration voltage using GO sample support film in comparison with those taken at above 60 kV or of samples deposited on carbon films. The observed difference is explained theoretically by increased multiple and inelastic electron scattering at low acceleration voltages in the carbon film in comparison with GO. Only a few atom layers thick GO causes much less electron beam scattering enabling high contrast imaging of unstained organic and biological particular specimens.
It has also been shown that samples can be sandwiched between substrate and GO to protect them from the vacuum and electron bombardment. This prevents dehydration, melting and removal of volatile substances from the sample. In principle this would enable one to do environmental-like EM with conventional equipment. We have also successfully prepared samples of GO wrapped E.Coli and S. Pneumoniae. Images reveal that GO will easily form a cling wrap resembling film over bacteria. We are currently planning experiments to evaluate extent of bacterial dehydration and viability after exposure to ultra high vacuum of TEM.
ELECTROPOLYMERIZATION OF CONDUCTING POLYMER-GRAPHENE
COMPOSITE FILM
Milla Suominen
1, Pia Damlin
1, Suvi Lehtimäki
2, Sampo Tuukkanen
3, Donald Lupo
2, Carita
Kvarnström1
1University of Turku, Department of Chemistry, Vatselankatu 2, FIN-20014 Turku, Finland
2Tampere University of Technology, Department of Electronics and Communication Engineering
3Tampere University of Technology, Department of Automation Science and Engineering,
Korkeakoulunkatu 3, FI-33101 Tampere, Finland
E-mail: [email protected]
Due to their high intrinsic redox capacitance conducting polymers (CP) have attracted great
interest as active components in energy storage devices. CPs swell and shrink as they are
charged and discharged which quickly leads to breaking of the structure and loss of
capacitance. When combined with mechanically strong graphene, synergistic effects can be
observed.
In this work CP/graphene composite materials were prepared using graphene oxide (GO) as
starting material for graphene. GO is the most common starting material for graphene, since it
can be produced in large quantities as well separated sheets and it’s stable in water solutions.
However, GO must be reduced to restore the conducting graphitic structure. In our work
electrochemical reduction method was used since it is an eco-friendly choice which offers
control of the reduction process under mild conditions. Energy rich poly(3,4-ethylenedioxy-
thiophene) (PEDOT) and polyazulene (PAz) were chosen as CPs of our composites. As
electrolyte solutions we used ionic liquids (IL). ILs are non-volatile and have negligible
vapor pressures which make them a greener choice compared to organic solvents. In addition,
they have a broad potential window allowing completeness of the electrochemical reduction
process of GO1. Reference films were prepared in aqueous solutions. As can be seen in Fig 1.
a and b ILs have a dramatic influence on the microstructure of these composites.
After the reduction process the composites (PEDOT/rGO) exhibited increased capacitance
(Fig 1c.) and cycling stability when cycled 800 times in IL2. Materials were also prepared on
top of flexible PET-substrates, and a symmetrical supercapacitor was constructed3.
Composite film capacitance was nearly 20 mF/cm2 while PEDOT-film capacitance was only
14 mF/cm2. The composite supercapacitor could also switch a small printed screen on and off
65 times with one load from a printed solar cell.
Figure 1. SEM image of PEDOT/rGO film prepared in a) aqueous solution, and b) IL. c) Cyclic
voltammograms of PEDOT/GO (black) and PEDOT/rGO (violet) composite films in IL.
1. J. Kauppila, P. Kunnas, P. Damlin, A. Viinikanoja, C. Kvarnström, Electrochim. Acta 89 (2013) 84.
2. P. Damlin, M. Suominen, M. Heinonen, C. Kvarnström, Carbon 93 (2015) 533.
3. S. Lehtimäki, M. Suominen, P. Damlin, S. Tuukkanen, C. Kvarnström, D. Lupo, ACS Appl. Mat.
Int., DOI: 10.1021/acsami.5b05937
a) b) c)
The low-temperature magnetostructure and magnetic field response ofPr0.9Ca0.1MnO3: The roles of Pr spins and magnetic phase separation
J. Tikkanen1,*, M. Geilhufe2, M. Frontzek3, W. Hergert4, A. Ernst2, P. Paturi1 and L. Udby5
1Wihuri Physical Laboratory, Dept. of Physics and Astronomy, University of Turku, FI-20014 Turku, Finland2Theory Department, Max Planck Institute of Microstructure Physics, D-06120 Halle, Germany3Laboratory for Neutron Scattering, Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland
4Naturwissenschaftliche Fakultät II, Institut für Physik, Martin-Luther-Universität Halle-Wittenberg, D-06099 Halle, Germany5X-Ray and Neutron Science, Niels Bohr Institute, University of Copenhagen, DK-2100 Copenhagen, Denmark
*Corresponding author. Email: [email protected]
With the goal of elucidating the background of photoinduced ferromagnetismphenomena observed in the perovskite structured (Pr, Ca) manganites, the low-temperaturemagnetostructure of the material Pr0.9Ca0.1MnO3 was revised using cold neutron powderdiffraction, SQUID magnetometry and ab-initio calculations. Particular emphasis was placedon determining the presence of nanoscale magnetic phase separation. Previously publishedresults of a canted A-AFM average ground state were reproduced to a good precision bothexperimentally and theoretically, and complemented by investigating the effects of an appliedmagnetic field of 2.7 T on the magnetostructure. Explicit evidence of nanoscale magneticclusters in the material was obtained based on high-resolution neutron diffractograms. Alongwith several supporting arguments, we present this finding as a justification for extending thenanoscale magnetic phase separation model of manganites to the material under discussiondespite its very low Ca doping level in the context of the model. In the light of the new data,we also conclude that the low temperature magnetic moment of Pr must be ca. 300 % largerthan previously thought in this material, close to the high spin value of 2 µB per formula unit.
Figure: Real space illustrations of the average magnetic structures experimentally found inPCMO x = 0.1 by neutron diffraction. For clarity, oxygen atoms are omitted and only a half of themagnetic unit cell is shown along c. The indicated coordinate axes correspond to those of thePbnm unit cell. The arrows on the edges of the drawn cells represent Mn magnetic moments, theones in the middle stand for the Pr moment.
ENHANCEMENT OF THE UP-CONVERSION LUMINESCENCE FROM
NaYF4:Yb3+,Er3+ THROUGH CHROMIUM CO-DOPING
Minnea Tuomisto1-3*, Emilia Palo1-3, Tero Laihinen1-3, Iko Hyppänen1,3,
Mika Lastusaari1,3, Hendrik C. Swart4, Jorma Hölsä1,3
1University of Turku, Department of Chemistry, FI-20014 Turku, Finland
2University of Turku Graduate School (UTUGS), Doctoral Programme in Physical and Chemical Sciences, Turku, Finland
3Turku University Centre for Materials and Surfaces (MatSurf), Turku, Finland 5University of the Free State, Department of Physics, Bloemfontein, Republic of South Africa
Up-conversion luminescence where two or more low energy (e.g. NIR) photons is
converted to high energy radiation (e.g. light) has numerous applications from solar
cells to medical diagnostics [1]. At present, one of the most efficient up-converting
materials is the hexagonal NaYF4:Yb3+,Er3+ material. However, the up-conversion
luminescence efficiency still requires improvement in terms of some applications such
as solar cells. For example, the commonly used absorber Yb3+ absorbs energy only in
a narrow area around 980 nm. Therefore, a wide absorption band would be highly
desired. Some d transition metals can absorb in the IR area and hereby may have the
ability to enhance the up-conversion luminescence. The aim of this work was to study
the effect of chromium co-doping on the up-conversion luminescence.
The materials were prepared with
different concentration of Cr using the co-
precipitation method [2]. The as-
prepared materials were annealed in
static N2 + 10 % H2 at 500 °C for 5 h to
get the desired hexagonal sturcture. The
materials showed red (640-670 nm) and
green (520-560 nm) up-conversion
luminescence under 976 nm excitation
(Fig.). These are due to the 4F9/2→4I15/2
and 2H11/2,4S3/2→4I15/2 transitions of Er3+,
respectively [3]. Cr co-doping clearly
enhanced the up-conversion lumi-
nescence when the doping amount of
0,1 mol-% was used.
References
1. Auzel, F., Chem. Rev., 104 (2004) 139–173.
2. Yi, G., Lu, H., Zhao, S., Ge, Y., Yang, W., Chen, D. and Guo, L.-H., Nano Lett., 4
(2004) 2191–2196.
3. Hyppänen, I., Hölsä, J., Kankare, J., Lastusaari, M., Pihlgren, L. and Soukka, T.,
Terrae Rarae, 16 (2009) 1–6.
Fig. . Up-conversion luminescence spectra of
NaYF4:Yb3+,Er3+ with and without Cr co-doping.
450 500 550 600 650 700 750 800
0
2000
4000
6000
8000
10000
12000
14000
Inte
nsity / A
rb. U
nits
Wavelength / nm
exc
: 976 nm
T: 295 K
2H
11/2
4I15/2
4S
3/2
4I15/2
4F
9/2
4I15/2
NaYF4:Yb
3+,Er
3+,Cr
3+
xYb
: 0.17; xEr
: 0.003x
Cr: 0.001
None
0.0005
0.002
x 20
Electrochemical Synthesis and Characterization of Polyviologens
Nianxing Wang1, 2*, Anniina Kähkönen 1, Timo Ääritalo 1, Pia Damlin 1, Jouko Kankare 1, CaritaKvarnström 1
1 Turku University Center for Materials and Surfaces, c/o Laboratory of Materials Chemistry andChemical Analysis, University of Turku
Vatselankatu 2, FI-20014 Turku, Finland2 University of Turku Graduate School (UTUGS), FI-20014, Turku, Finland
The viologen has been widely studied in recent years due to its unique redox property, and it has been utilized invarious applications such as electrochromic materials, sensors, and solar cells 1. The key feature of viologen isthe three redox forms: dication form, radical cation form and neutral form, which are shown in Scheme.1. Aseries of polyviologens have been synthesized and characterized in our group with variouscyanopyridine-based monomers2. The polyviologens have been characterized both withelectrochemical and spectroscopic techniques and it has been proved that the polyviologens haveunique structures, so they can be utilized in various electronics and especially as the host materials toimmobilize various macromolecules.
Scheme 1. Three redox forms of viologen
References1. Monk, P. M. S., The viologens: physicochemical properties, synthesis, and applications of the salts of4, 4'-bipyridine. John Wiley & sons Ltd: West Sussex, England, 1998.2. (a) Wang, N.; Damlin, P.; Esteban, B. M.; Ääritalo, T.; Kankare, J.; Kvarnström, C., Electrochemicalsynthesis and characterization of copolyviologen films. Electrochimica Acta 2013, 90, 171-178; (b) Wang, N.;Kähkönen, A.; Damlin, P.; Ääritalo, T.; Kankare, J.; Kvarnström, C., Electrochemical synthesis andcharacterization of branched viologen derivatives. Electrochimica Acta 2015, 154, 361-369.
Synthesis and properties of crystalline thin film of antimony
trioxideon the Si(100) substrate
M. Yasir1, M. Kuzmin
1,2, M.P.J. Punkkinen
1, J. Mäkelä
1, M. Tuominen
1, J. Dahl
1,P. Laukkanen
1, K.
Kokko1.
1Department of Physics and Astronomy, University of Turku, FI-20014 Turku, Finland.
2Ioffe Physical-Technical Institute, Russian Academy of Sciences, St. Petersburg 194021, Russian Federation.
Among various metal oxide films, antimony trioxide (Sb2O3) thin films and
nanostructures have received much attention because they have a surprisingly large
variety of applications including flame retarders, transparent conducting films,
antireflection coatings, catalysts, and dielectrics. Atomic-scale understanding and
processing of the surface and interface properties of antimony trioxide (Sb2O3) are
essential to the development of nanoscale Sb2O3 structures. Lack of atomically well-
defined, crystalline Sb2O3 templates has however hindered atomic resolution
characterization of the Sb2O3 properties. In our studies, we demonstrate the tailoring of
crystalline Sb2O3 thin films on the Si (100) substrate. Using a thermal evaporation
method we deposited a Sb film over Si (100) substrate and synthesis a Sb2O3 film with a
simple process by oxidizing Sb-covered Si (100) in proper conditions. A (1×1)
diffraction pattern confirms the film crystallinity observed in low energy electron
diffraction method. Surface morphology and surface roughness was studied using
scanning tunneling microscopy and spectroscopy, and ab initio calculations. The results
of scanning tunneling spectroscopy show that the band gap of Sb2O3 is 3.6eV around the
gamma point (i.e. Γ). Ab initio calculations reveal energetically favored Sb2O3 (100)
surface structures. The findings open a new path for the atomic-scale research of Sb2O3.
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ABSTRACT # 1
Turku University Centre for Materials and Surfaces(www.matsurf.utu.fi)
Participating laboratories:
Laboratory of Materials Research (Prof. Edwin Kukk, Prof. Kalevi Kokko)Laboratory of Industrial Physics (Doc. Jarno Salonen)Wihuri Physical Laboratory (Prof. Kurt Gloos, Prof. Petriina Paturi)Laboratory of Materials Chemistry and Chemical Analysis (Prof. CaritaKvarnström, Dr. Mika Lastusaari)Turku Clinical Biomaterials Centre – TCBC (Prof. Pekka Vallittu, DDS LippoLassila)Laboratory of Electron Microscopy (Dr. Markus Peurla, Prof. emeritus LauriPelliniemi)