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- ItemA novel precursor system and its application to produce tin doped indium oxide(Cambridge : Royal Society of Chemistry, 2011) Veith, Michael; Bubel, Carsten; Zimmer, MichaelA new type of precursor has been developed by molecular design and synthesised to produce tin doped indium oxide (ITO). The precursor consists of a newly developed bimetallic indium tin alkoxide, Me2In(OtBu)3Sn (Me = CH3, OtBu = OC(CH3)3), which is in equilibrium with an excess of Me2In(OtBu). This quasi single-source precursor is applied in a sol–gel process to produce powders and coatings of ITO using a one-step heat treatment process under an inert atmosphere. The main advantage of this system is the simple heat treatment that leads to the disproportionation of the bivalent Sn(II) precursor into Sn(IV) and metallic tin, resulting in an overall reduced state of the metal in the final tin doped indium oxide (ITO) material, hence avoiding the usually necessary reduction step. Solid state 119Sn-NMR measurements of powder samples confirm the appearance of Sn(II) in an amorphous gel state and of metallic tin after annealing under nitrogen. The corresponding preparation of ITO coatings by spin coating on glass leads to transparent conductive layers with a high transmittance of visible light and a low electrical resistivity without the necessity of a reduction step.
- ItemSolvent influence on the surface morphology of P3HT thin films revealed by photoemission electron microscopy(Cambridge : Royal Society of Chemistry, 2019) Niefind, Falk; Karande, Shubhangi; Frost, Frank; Abel, Bernd; Kahnt, AxelOnly rigorous understanding of the relationship between the nanoscale morphology of organic thin films and the performance of the devices built from them will ultimately lead to design rules that can guide a structured development on the field of organic electronics. Despite great effort, unraveling the nanoscale structure of the films is still a challenge in itself. Here we demonstrate that photoemission electron microscopy can provide valuable insights into the chain orientation, domains size and grain boundary characteristics of P3HT films spun cast from different solvents at room as well as at elevated temperatures. © 2019 The Royal Society of Chemistry.
- ItemA crystalline anionic complex of scandium nitride endometallofullerene: Experimental observation of single-bonded (Sc3N@Ih-C80−)2 dimers(Cambridge : Royal Society of Chemistry, 2016) Konarev, Dmitri V.; Zorina, Leokadiya V.; Khasanov, Salavat S.; Popov, Alexey A.; Otsuka, Akihiro; Yamochi, Hideki; Saito, Gunzi; Lyubovskaya, Rimma N.Reduction of scandium nitride clusterfullerene, Sc3N@Ih-C80, by sodium fluorenone ketyl in the presence of cryptand[2,2,2] allows the crystallization of the {cryptand[2,2,2](Na+)}2(Sc3N@Ih-C80−)2·2.5C6H4Cl2 (1) salt. The Sc3N@Ih-C80˙− radical anions are dimerized to form single-bonded (Sc3N@Ih-C80−)2 dimers.
- ItemAnalysis of fatty acids and triacylglycerides by Pd nanoparticle-assisted laser desorption/ionization mass spectrometry(Cambridge : Royal Society of Chemistry, 2015) Silina, Yuliya E.; Fink-Straube, Claudia; Hayen, Heiko; Volmer, Dietrich A.In this study, we propose a simple and rapid technique for characterization of free fatty acids and triacylglycerides (TAG) based on palladium nanoparticular (Pd-NP) surface-assisted laser desorption/ionization (SALDI) mass spectrometry (MS). The implemented Pd-NP material allowed detection of free fatty acids and TAGs exclusively as [M + K]+ ions in positive ion mode. Under negative ionization conditions, unusual trimetric structures were generated for free fatty acids, while TAGs underwent irreproducible degradation reactions. Importantly, the mass spectra obtained from Pd-NP targets in positive ion mode were very clean without interferences from matrix-derived ions in the low m/z range and readily enabled the detection of intact TAGs in vegetable oils without major fragmentation reactions as compared to conventional MALDI-MS, requiring only a minimal amount of sample preparation.
- ItemIn situ tracking of the nanoscale expansion of porous carbon electrodes(Cambridge : Royal Society of Chemistry, 2013) Arruda, Thomas M.; Heon, Min; Presser, Volker; Hillesheim, Patrick C.; Dai, Sheng; Gogotsi, Yury; Kalinin, Sergei V.; Balke, NinaElectrochemical double layer capacitors (EDLC) are rapidly emerging as a promising energy storage technology offering extremely large power densities. Despite significant experimental progress, nanoscale operation mechanisms of the EDLCs remain poorly understood and it is difficult to separate processes at multiple time and length scales involved in operation including that of double layer charging and ionic mass transport. Here we explore the functionality of EDLC microporous carbon electrodes using a combination of classical electrochemical measurements and scanning probe microscopy based dilatometry, thus separating individual stages in charge/discharge processes based on strain generation. These methods allowed us to observe two distinct modes of EDLC charging, one fast charging of the double layer unassociated with strain, and another much slower mass transport related charging exhibiting significant sample volume changes. These studies open the pathway for the exploration of electrochemical systems with multiple processes involved in the charge and discharge, and investigation of the kinetics of those processes.
- ItemHigh-throughput screening Raman microspectroscopy for assessment of drug-induced changes in diatom cells(Cambridge : Royal Society of Chemistry, 2019) Rüger J.; Mondol A.S.; Schie I.W.; Popp J.; Krafft C.High-throughput screening Raman spectroscopy (HTS-RS) with automated localization algorithms offers unsurpassed speed and sensitivity to investigate the effect of dithiothreitol on the diatom Phaedactylum tricornutum. The HTS-RS capability that was demonstrated for this model system can be transferred to unmet analytical applications such as kinetic in vivo studies of microalgal assemblages. © 2019 The Royal Society of Chemistry.
- ItemVanadia–titania multilayer nanodecoration of carbon onions via atomic layer deposition for high performance electrochemical energy storage(Cambridge : Royal Society of Chemistry, 2016) Fleischamann, Simon; Tolosa, Aura; Zieger, Marco; Krüner, Benjamin; Peter, Nicolas J.; Grobelsek, Ingrid; Quade, Antje; Kruth, Angela; Presser, VolkerAtomic layer deposition has proven to be a particularly attractive approach for ecorating mesoporous carbon substrates with redox active metal oxides for lectrochemical energy storage. This study, for the first time, capitalizes on the cyclic character of atomic layer deposition to obtain highly conformal and atomically controlled decoration of carbon onions with alternating stacks of vanadia and titania. The addition of 25 mass% TiO2 leads to expansion of the VO2 unit cell, thus greatly enhancing lithium intercalation capacity and kinetics. Electrochemical characterization revealed an ultrahigh discharge capacity of up to 382 mA h g^-1 of the composite electrode (554 mA h g^-1 per metal oxide) with an impressive capacity retention of 82 mA h g^-1 (120 mA h g^-1 per metal oxide) at a high discharge rate of 20 A g^-1 or 52C. Stability benchmarking showed stability over 3000 cycles when discharging to a reduced potential of ^-1.8 V vs. carbon. These capacity values are among the highest reported for any metal oxide system, while in addition, upercapacitor-like power performance and longevity are achieved. At a device level, high specific energy and power of up to 110 W h kg^-1 and 6 kW kg^-1, respectively, were achieved when employing the hybrid material as anode versus activated carbon cathode.
- ItemPhase change thin films for non-volatile memory applications(Cambridge : Royal Society of Chemistry, 2019) Lotnyk, A.; Behrens, M.; Rauschenbach, B.The rapid development of Internet of Things devices requires real time processing of a huge amount of digital data, creating a new demand for computing technology. Phase change memory technology based on chalcogenide phase change materials meets many requirements of the emerging memory applications since it is fast, scalable and non-volatile. In addition, phase change memory offers multilevel data storage and can be applied both in neuro-inspired and all-photonic in-memory computing. Furthermore, phase change alloys represent an outstanding class of functional materials having a tremendous variety of industrially relevant characteristics and exceptional material properties. Many efforts have been devoted to understanding these properties with the particular aim to design universal memory. This paper reviews materials science aspects of chalcogenide-based phase change thin films relevant for non-volatile memory applications. Particular emphasis is put on local structure, control of disorder and its impact on material properties, order-disorder transitions and interfacial transformations. © 2019 The Royal Society of Chemistry.
- ItemAn electrochemical in situ study of freezing and thawing of ionic liquids in carbon nanopores(Cambridge : Royal Society of Chemistry, 2014) Weingarth, Daniel; Drumm, Robert; Foelske-Schmitz, Annette; Kotz, Rüdiger; Presser, VolkerRoom temperature ionic liquids (RTILs) are an emerging class of electrolytes enabling high cell voltages and, in return, high energy density of advanced supercapacitors. Yet, the low temperature behavior, including freezing and thawing, is little understood when ions are confined in the narrow space of nanopores. This study shows that RTILs may show a tremendously different thermal behavior when comparing bulk with nanoconfined properties as a result of the increased surface energy of carbon pore walls. In particular, a continuous increase in viscosity is accompanied by slowed-down charge-discharge kinetics as seen with in situ electrochemical characterization. Freezing reversibly collapses the energy storage ability and thawing fully restores the initial energy density of the material. For the first time, a different thermal behavior in positively and negatively polarized electrodes is demonstrated. This leads to different freezing and melting points in the two electrodes. Compared to bulk, RTILs in the confinement of electrically charged nanopores show a high affinity for supercooling; that is, the electrode may freeze during heating.
- ItemBi-phasic nanostructures for functional applications(Cambridge : Royal Society of Chemistry, 2012) Veith, Michael; Lee, Juseok; Miro, Marina Martinez; Akkan, C. Kaan; Dufloux, Cecile; Aktas, O. CenkBiphasic solid state composites of the type metal/metal oxide or element/element oxide can be synthesized in one pot chemical reactions using so called molecular "single source precursors". Due to their singular genesis these composites show peculiar hetero-structures based on core-shell hierarchies such as superlattices and composite nanospheres or nanowires. They exhibit superior or new functional properties compared to their individual constituent compounds. In the current work, we review in particular the synthetical and mechanistical approach of bi-phasic (Al/Al2O3) nanostructures such as nanospheres, nanowires and nanoloops using a single source precursor. Other bi-phasic materials of the general formula M/MOx (for example M = Ge, Sn, Pb) are addressed for comparison. The impact of different synthetical conditions as well as of modification of surfaces by laser techniques and their technological relevance are presented briefly. Additionally, functional applications of the prepared surfaces are explained with some outstanding case studies. These case studies are primarily concerned with their use as biomaterials and their application in medicine as well as with their use as thin films for optics and functional surfaces.