Highlight Publications 2018

Origin of Negative Capacitance in Bipolar Organic Diodes
Quan Niu, N. Irina Crăciun, Gert-Jan A. H. Wetzelaer, and Paul W. M. Blom
Origin of Negative Capacitance in Bipolar Organic Diodes
An important parameter for devices as organic light-emitting diodes (OLEDs) is the capacitance, which provides information on the build-up of charges. However, in OLEDs the capacitance frequently becomes negative, a phenomenon that is poorly understood. We have revealed the origin of the negative capacitance by varying the number of electron traps in OLEDs. When adding electron traps, the negative capacitance became more pronounced, whereas the negative capacitance could be completely eliminated by reducing the number of traps by means of trap dilution. Now that the phenomenon is understood, the negative capacitance can be used to determine the number of traps in organic semiconductors.
© MPI-P (2018)
Reducing the negative capacitance in an OLED by blending with an insulating polymer
Calcium-Induced Molecular Rearrangement of Peptide Folds Enables Biomineralization of Vaterite Calcium Carbonate
Hao Lu, Helmut Lutz, Steven J. Roeters, Matthew A. Hood, Arne Schäfer, Rafael Muñoz-Espí, Rüdiger Berger, Mischa Bonn, Tobias Weidner
Calcium-Induced Molecular Rearrangement of Peptide Folds Enables Biomineralization of Vaterite Calcium Carbonate
Calcium carbonate (CaCO3) is the most abundant mineral on earth and plays an important role for life. CaCO3 is a key component of marine animals such as mollusk, mussels and sponges. The biogenesis of CaCO3-based hard tissue is tightly controlled by proteins, which exert control over the nucleation and growth of the specific phase of CaCO3, calcite, aragonite and vaterite. The latter phase occurs almost exclusively as a biomineral and has applications in drug delivery, implant design and surface coating. In this article we used surface spectroscopy and molecular dynamics simulations to determine, at the molecular level, how proteins control the formation of vaterite phase CaCO3.
© ACS (2018)
Calcium carbonate biogenesis is tightly controlled by proteins. Vaterite phase CaCO3 occurs almost exclusively as a biomineral and has applications in drug delivery and implant design. This article describes how proteins control the formation of vaterite phase CaCO3.
Precision synthesis versus bulk-scale fabrication of graphenes
Xiao-Ye Wang, Akimitsu Narita, Klaus Müllen
Precision synthesis versus bulk-scale fabrication of graphenes
Graphene is a fascinating material with unique properties, such as extreme mechanical strength, ultrahigh electrical and thermal conductivities and remarkable transparency. Further reduction in the dimensionality of graphene in the form of graphene quantum dots and graphene nanoribbons has compensated for the lack of a bandgap in the extended 2D material. These nanoscale graphenes exhibit finite bandgaps because of quantum confinement, making them attractive as next-generation semiconductors. Numerous fabrication methods for various types of graphenes have been developed, which can generally be categorized into ‘top-down’ and ‘bottom-up’ procedures. These methods afford, on different production scales, a wide range of graphene structures of different sizes, shapes and quality (defect density, edge roughness and so on). Atomically precise syntheses are indispensable for fundamental research and future technological development, but the projection of the existing methods to cost-effective bulk-scale fabrication techniques is required for upcoming industrial applications of graphenes.
© Nature Publishing Group (2018)
Precision synthesis versus bulk-scale fabrication of graphenes
Hydrophilicity regulates the stealth properties of polyphosphoester-coated nanocarriers
Johanna Simon, Thomas Wolf, Katja Klein, Katharina Landfester, Volker Mailänder and Frederik Roman Wurm
Hydrophilicity regulates the stealth properties of polyphosphoester-coated nanocarriers
Increasing the plasma half-life is an important goal in the development drug carriers. Attachment of polymers, especially poly(ethylene glycol) (PEG), is an effective method to increase the plasma half-life of drugs. Even though it was assigned to be a result of a decreased overall protein adsorption on the hydrophilic surface in combination with the adsorption of specific proteins, the molecular reasons for the success of PEG and other hydrophilic polymers are still widely unknown. We prepare poly(phosphoester)-coated nanocarriers with adjusted hydrophilicity to control the stealth properties of the polymer shell. We find that the logP-values of the copolymers control the pattern of the protein corona and the cell interaction. In spite of a significant change in hydrophilicity, the overall protein amount adsorbed from blood on the nanocarrier is unchanged, while the protein pattern is altered. This underlines the importance of the protein type in the protein corona and cell uptake.
© Wiley-VCH (2018)
A Rational Delamination Strategy towards Defect-Free, High-Mobility, Few-Layered Black Phosphorus Flakes
Sheng Yang, Ke Zhang, Antonio Gaetano Ricciardulli, Panpan Zhang, Zhongquan Liao, Martin R. Lohe, Ehrenfried Zschech, Paul W. M. Blom, Wojciech Pisula, Klaus Müllen and Xinliang Feng
A Rational Delamination Strategy towards Defect-Free, High-Mobility, Few-Layered Black Phosphorus Flakes
Based on electrochemical engineering, a simple and scalable exfoliation method was developed to bring truly defect-free black phosphorus (BP) flakes to a macroscopic scale. The delaminated flakes exhibited excellent electronic properties, well comparable with mechanically exfoliated BP flakes. This strategy paves great opportunities for the future development of BP-based devices and technologies.
© WILEY-VCH (2018)
Cathodic exfoliation of bulk black phosphorus in organic electrolytes.
CO2-Triggered Switchable Hydrophilicity of Heterogeneous Conjugated Polymer Photocatalyst for Enhanced Catalytic Activity in Water
Jeehye Byun, Wei Huang, Di Wang, Run Li, Kai A. I. Zhang
CO2-Triggered Switchable Hydrophilicity of Heterogeneous Conjugated Polymer Photocatalyst for Enhanced Catalytic Activity in Water
Water-compatibility of heterogeneous photocatalysts has been pursued for energy and environmental applications. However, there exists a trade-off between hydrophilicity and recyclability of the photocatalyst. MPIP researchers have designed a conjugated polymer photocatalyst with tertiary amine terminals that reversibly binds CO2 in water, generating a switchable hydrophilicity. The CO2-assisted hydrophilicity boosted up the photocatalytic efficiency in aqueous medium with minimum dosage. When CO2 was desorbed, the photocatalyst could be simply regenerated from reaction media, facilitating the repeated use of photocatalyst. The hydrophilicity/hydrophobicity control of the polymer photocatalyst has successfully showcased through a variety of organic photo-redox reactions under visible light irradiation in water.
© Wiley VCH (2018)
CO2-triggered switchable hydrophilicity of a conjugated polymer photocatalyst for photocatalysis in water
Hybrid silver nanowire and graphene based solution-processed transparent electrode for organic optoelectronics
Antonio Gaetano Ricciardulli, Sheng Yang, Gert-Jan A. H. Wetzelaer, Xinliang Feng, Paul W. M. Blom
Hybrid silver nanowire and graphene based solution-processed transparent electrode for organic optoelectronics
The research on transparent conductive electrodes (TCEs) is in rapid ascent in order to respond to the requests of novel optoelectronic devices. The synergic coupling of silver nanowires (AgNWs) and high-quality solution-processable exfoliated graphene (EG) enables an efficient transparent conductor with low surface roughness of 4.6 nm, low sheet resistance of 13.7 Ω sq-1 at high transmittance and superior mechanical and chemical stabilities. The developed AgNWs-EG films are versatile for a wide variety of optoelectronics. As an example, when used as bottom electrode in organic solar cell (OSC) and polymer light-emitting diode (PLED), the devices exhibit a power conversion efficiency of 6.6% and an external quantum efficiency of 4.4% respectively, comparable to their commercial ITO-counterparts.
© Wiley VCH (2018)
Flexible OSC and PLED based on spray-coated hybrid AgNWs-EG transparent electrodes.
 
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