Search Results
High-performance Li-O2 batteries with trilayered Pd/MnOx/Pd nanomembranes
2015, Lu, Xueyi, Deng, Junwen, Si, Wenping, Sun, Xiaolei, Liu, Xianghong, Liu, Bo, Liu, Lifeng, Oswald, Steffen, Baunack, Stefan, Grafe, Hans Joachim, Yan, Chenglin, Schmidt, Oliver G.
Trilayered Pd/MnOx/Pd nanomembranes are fabricated as the cathode catalysts for Li‐O2 batteries. The combination of Pd and MnOx facilitates the transport of electrons, lithium ions, and oxygen‐containing intermediates, thus effectively decomposing the discharge product Li2O2 and significantly lowering the charge overpotential and enhancing the power efficiency. This is promising for future environmentally friendly applications.
Synthesis, spectroscopic characterization and thermogravimetric analysis of two series of substituted (metallo)tetraphenylporphyrins
2017-6-2, Al-Shewiki, Rasha K., Mende, Carola, Buschbeck, Roy, Siles, Pablo F., Schmidt, Oliver G., Rüffer, Tobias, Lang, Heinrich
Subsequent treatment of H2TPP(CO2H)4 (tetra(p-carboxylic acid phenyl)porphyrin, 1) with an excess of oxalyl chloride and HNR2 afforded H2TPP(C(O)NR2)4 (R = Me, 2; iPr, 3) with yields exceeding 80%. The porphyrins 2 and 3 could be converted to the corresponding metalloporphyrins MTPP(C(O)NR2)4 (R = Me/iPr for M = Zn (2a, 3a); Cu (2b, 3b); Ni (2c, 3c); Co (2d, 3d)) by the addition of 3 equiv of anhydrous MCl2 (M = Zn, Cu, Ni, Co) to dimethylformamide solutions of 2 and 3 at elevated temperatures. Metalloporphyrins 2a–d and 3a–d were obtained in yields exceeding 60% and have been, as well as 2 and 3, characterized by elemental analysis, electrospray ionization mass spectrometry (ESIMS) and IR and UV–vis spectroscopy. Porphyrins 2, 2a–d and 3, 3a–d are not suitable for organic molecular beam deposition (OMBD), which is attributed to their comparatively low thermal stability as determined by thermogravimetric analysis (TG) of selected representatives.
Molecular Insights into Division of Single Human Cancer Cells in On-Chip Transparent Microtubes
2016, Xi, Wang, Schmidt, Christine K., Sanchez, Samuel, Gracias, David H., Carazo-Salas, Rafael E., Butler, Richard, Lawrence, Nicola, Jackson, Stephen P., Schmidt, Oliver G.
In vivo, mammalian cells proliferate within 3D environments consisting of numerous microcavities and channels, which contain a variety of chemical and physical cues. External environments often differ between normal and pathological states, such as the unique spatial constraints that metastasizing cancer cells experience as they circulate the vasculature through arterioles and narrow capillaries, where they can divide and acquire elongated cylindrical shapes. While metastatic tumors cause most cancer deaths, factors impacting early cancer cell proliferation inside the vasculature and those that can promote the formation of secondary tumors remain largely unknown. Prior studies investigating confined mitosis have mainly used 2D cell culture systems. Here, we mimic aspects of metastasizing tumor cells dividing inside blood capillaries by investigating single-cell divisions of living human cancer cells, trapped inside 3D rolled-up, transparent nanomembranes. We assess the molecular effects of tubular confinement on key mitotic features, using optical high- and super-resolution microscopy. Our experiments show that tubular confinement affects the morphology and dynamics of the mitotic spindle, chromosome arrangements, and the organization of the cell cortex. Moreover, we reveal that membrane blebbing and/or associated processes act as a potential genome-safety mechanism, limiting the extent of genomic instability caused by mitosis in confined circumstances, especially in tubular 3D microenvironments. Collectively, our study demonstrates the potential of rolled-up nanomembranes for gaining molecular insights into key cellular events occurring in tubular 3D microenvironments in vivo.
A size dependent evaluation of the cytotoxicity and uptake of nanographene oxide
2015, Mendes, Rafael Gregorio, Koch, Britta, Bachmatiuk, Alicja, Ma, Xing, Sanchez, Samuel, Damm, Christine, Schmidt, Oliver G., Gemming, Thomas, Eckert, Jürgen, Rümmeli, Mark H.
Graphene oxide (GO) has attracted great interest due to its extraordinary potential for biomedical application. Although it is clear that the naturally occurring morphology of biological structures is crucial to their precise interactions and correct functioning, the geometrical aspects of nanoparticles are often ignored in the design of nanoparticles for biological applications. A few in vitro and in vivo studies have evaluated the cytotoxicity and biodistribution of GO, however very little is known about the influence of flake size and cytotoxicity. Herein, we aim at presenting an initial cytotoxicity evaluation of different nano-sized GO flakes for two different cell lines (HeLa (Kyoto) and macrophage (J7742)) when they are exposed to samples containing different sized nanographene oxide (NGO) flakes (mean diameter of 89 and 277 nm). The obtained data suggests that the larger NGO flakes reduce cell viability as compared to smaller flakes. In addition, the viability reduction correlates with the time and the concentration of the NGO nanoparticles to which the cells are exposed. Uptake studies were also conducted and the data suggests that both cell lines internalize the GO nanoparticles during the incubation periods studied.
Electrically-Pumped Wavelength-Tunable GaAs Quantum Dots Interfaced with Rubidium Atoms
2017, Huang, Huiying, Trotta, Rinaldo, Huo, Yongheng, Lettner, Thomas, Wildmann, Johannes S., Martín-Sánchez, Javier, Huber, Daniel, Reindl, Marcus, Zhang, Jiaxiang, Zallo, Eugenio, Schmidt, Oliver G., Rastelli, Armando
We demonstrate the first wavelength-tunable electrically pumped source of nonclassical light that can emit photons with wavelength in resonance with the D2 transitions of 87Rb atoms. The device is fabricated by integrating a novel GaAs single-quantum-dot light-emitting diode (LED) onto a piezoelectric actuator. By feeding the emitted photons into a 75 mm long cell containing warm 87Rb vapor, we observe slow-light with a temporal delay of up to 3.4 ns. In view of the possibility of using 87Rb atomic vapors as quantum memories, this work makes an important step toward the realization of hybrid-quantum systems for future quantum networks.
Deposition of exchange-coupled dinickel complexes on gold substrates utilizing ambidentate mercapto-carboxylato ligands
2017, Börner, Martin, Blömer, Laura, Kischel, Marcus, Richter, Peter, Salvan, Georgeta, Zahn, Dietrich R. T., Siles, Pablo F., Fuentes, Maria E. N., Bufon, Carlos C. B., Grimm, Daniel, Schmidt, Oliver G., Breite, Daniel, Abel, Bernd, Kersting, Berthold
The chemisorption of magnetically bistable transition metal complexes on planar surfaces has recently attracted increased scientific interest due to its potential application in various fields, including molecular spintronics. In this work, the synthesis of mixed-ligand complexes of the type [NiII2L(L’)](ClO4), where L represents a 24-membered macrocyclic hexaazadithiophenolate ligand and L’ is a ω-mercapto-carboxylato ligand (L’ = HS(CH2)5CO2− (6), HS(CH2)10CO2− (7), or HS(C6H4)2CO2− (8)), and their ability to adsorb on gold surfaces is reported. Besides elemental analysis, IR spectroscopy, electrospray ionization mass spectrometry (ESIMS), UV–vis spectroscopy, and X-ray crystallography (for 6 and 7), the compounds were also studied by temperature-dependent magnetic susceptibility measurements (for 7 and 8) and (broken symmetry) density functional theory (DFT) calculations. An S = 2 ground state is demonstrated by temperature-dependent susceptibility and magnetization measurements, achieved by ferromagnetic coupling between the spins of the Ni(II) ions in 7 (J = +22.3 cm−1) and 8 (J = +20.8 cm−1; H = −2JS1S2). The reactivity of complexes 6–8 is reminiscent of that of pure thiolato ligands, which readily chemisorb on Au surfaces as verified by contact angle, atomic force microscopy (AFM) and spectroscopic ellipsometry measurements. The large [Ni2L] tail groups, however, prevent the packing and self-assembly of the hydrocarbon chains. The smaller film thickness of 7 is attributed to the specific coordination mode of the coligand. Results of preliminary transport measurements utilizing rolled-up devices are also reported.
Optical properties and electrical transport of thin films of terbium(III) bis(phthalocyanine) on cobalt
2014, Robaschik, Peter, Siles, Pablo F., Bülz, Daniel, Richter, Peter, Monecke, Manuel, Fronk, Michael, Klyatskaya, Svetlana, Grimm, Daniel, Schmidt, Oliver G., Ruben, Mario, Zahn, Dietrich R.T., Salvan, Georgeta
The optical and electrical properties of terbium(III) bis(phthalocyanine) (TbPc2) films on cobalt substrates were studied using variable angle spectroscopic ellipsometry (VASE) and current sensing atomic force microscopy (cs-AFM). Thin films of TbPc2 with a thickness between 18 nm and 87 nm were prepared by organic molecular beam deposition onto a cobalt layer grown by electron beam evaporation. The molecular orientation of the molecules on the metallic film was estimated from the analysis of the spectroscopic ellipsometry data. A detailed analysis of the AFM topography shows that the TbPc2 films consist of islands which increase in size with the thickness of the organic film. Furthermore, the cs-AFM technique allows local variations of the organic film topography to be correlated with electrical transport properties. Local current mapping as well as local I–V spectroscopy shows that despite the granular structure of the films, the electrical transport is uniform through the organic films on the microscale. The AFMbased electrical measurements allow the local charge carrier mobility of the TbPc2 thin films to be quantified with nanoscale resolution.
(Metallo)porphyrins for potential materials science applications
2017-8-29, Smykalla, Lars, Mende, Carola, Fronk, Michael, Siles, Pablo F., Hietschold, Michael, Salvan, Georgeta, Zahn, Dietrich R.T., Schmidt, Oliver G., Rüffer, Tobias, Lang, Heinrich
The bottom-up approach to replace existing devices by molecular-based systems is a subject that attracts permanently increasing interest. Molecular-based devices offer not only to miniaturize the device further, but also to benefit from advanced functionalities of deposited molecules. Furthermore, the molecules itself can be tailored to allow via their self-assembly the potential fabrication of devices with an application potential, which is still unforeseeable at this time. Herein, we review efforts to use discrete (metallo)porphyrins for the formation of (sub)monolayers by surface-confined polymerization, of monolayers formed by supramolecular recognition and of thin films formed by sublimation techniques. Selected physical properties of these systems are reported as well. The application potential of those ensembles of (metallo)porphyrins in materials science is discussed.
Wearable magnetic field sensors for flexible electronics
2014, Melzer, Michael, Mönch, Jens Ingolf, Makarov, Denys, Zabila, Yevhen, Bermúdez, Gilbert Santiago Cañón, Karnaushenko, Daniil, Baunack, Stefan, Bahr, Falk, Yan, Chenglin, Kaltenbrunner, Martin, Schmidt, Oliver G.
Highly flexible bismuth Hall sensors on polymeric foils are fabricated, and the key optimization steps that are required to boost their sensitivity to the bulk value are identified. The sensor can be bent around the wrist or positioned on the finger to realize an interactive pointing device for wearable electronics. Furthermore, this technology is of great interest for the rapidly developing market of eMobility, for optimization of eMotors and magnetic bearings.
Dimensionality of rolled-up nanomembranes controls neural stem cell migration mechanism
2015, Koch, Britta, Meyer, Anne K., Helbig, Linda, Harazim, Stefan M., Storch, Alexander, Sanchez, Samuel, Schmidt, Oliver G.
We employ glass microtube structures fabricated by rolledup nanotechnology to infer the influence of scaffold dimensionality and cell confinement on neural stem cell (NSC) migration. Thereby, we observe a pronounced morphology change that marks a reversible mesenchymal to amoeboid migration mode transition. Space restrictions preset by the diameter of nanomembrane topography modify the cell shape toward characteristics found in living tissue. We demonstrate the importance of substrate dimensionality for the migration mode of NSCs and thereby define rolled-up nanomembranes as the ultimate tool for single-cell migration studies.