Blog

8
Jan

Tech Note – Together with Zeiss – Fabrication and Characterization of Nanofluidic Devices for DNA Optical Mapping

A a tech note entitled “Fabrication and Characterization of Nanofluidic Devices for DNA Optical Mapping” has been published by Carl Zeiss Microscopy GmbH, Germany and Parisa Bayat, Robert H. Blick, and Irene Fernández-Cuesta.

2
Jan

New Publication (Co-authorship): “Electrochemical Engineering of Nanoporous Materials for Photocatalysis: Fundamentals, Advances, and Perspectives” in MDPI Catalysts

A joined publication entitled “Electrochemical Engineering of Nanoporous Materials for Photocatalysis: Fundamentals, Advances, and Perspectives” with the group of Dr. Abel Santos (University Adelaide) has been publishedin ACS Langmuir

Abstract: Photocatalysis comprises a variety of light-driven processes in which solar energy is converted into green chemical energy to drive reactions such as water splitting for hydrogen energy generation, degradation of environmental pollutants, CO2 reduction and NH3 production. Electrochemically engineered nanoporous materials are attractive photocatalyst platforms for a plethora of applications due to their large effective surface area, highly controllable and tuneable light-harvesting capabilities, efficient charge carrier separation and enhanced diffusion of reactive species. Such tailor-made nanoporous substrates with rational chemical and structural designs provide new exciting opportunities to develop advanced optical semiconductor structures capable of performing precise and versatile control over light–matter interactions to harness electromagnetic waves with unprecedented high efficiency and selectivity for photocatalysis. This review introduces fundamental developments and recent advances of electrochemically engineered nanoporous materials and their application as platforms for photocatalysis, with a final prospective outlook about this dynamic field.

12
Nov

New Publication: “Low-Temperature Vapor-Solid Growth of ZnO Nanowhiskers for Electron Field Emission ” in MDPI Coatings

A new publication “Low-Temperature Vapor-Solid Growth of ZnO Nanowhiskers for Electron Field Emission”  from Stefanie and Carina has been published in MDPI Coatings.

Abstract:

One-dimensional zinc oxide nanostructures have aroused interest from scientists and engineers for electron field emission applications because of their experimentally accessible high aspect ratio in combination with their low work function. A comprehensive study of the vapor-solid growth of zinc oxide (ZnO) nanowhiskers by utilizing zinc acetylacetonate hydrate and oxygen at low temperature (580 °C) is reported herein. The nanowhiskers morphology was investigated by varying different growth parameters, such as temperature, substrate type and position, gas flow, precursor amount, and growth time. According to the obtained parameter dependences, the process was optimized to achieve homogenous crystalline nanowhiskers with high aspect ratios and clearly defined surface facets and tips. We show electron field emission measurements from tailor-made ZnO nanowhiskers grown on n-doped silicon, titanium thin films, and free-standing silicon nitride membranes, revealing field emission turn-on fields significantly lower compared to a perfect flat ZnO thin film. Especially the latter devices—ZnO nanowhiskers on a free-standing membrane—might pave the way into a novel nanomembrane detector unit in proteomics, which can significantly extend the mass range of current time-of-flight mass spectrometers.
12
Nov

PhD Defense: Paul Gwozdz

Paul defended his PhD thesis successfully on the 4th of November. Congratulations!

25
Sep

PhD Defense: Jonas Sichau

Jonas is going to defend his PhD thesis entitled: “Electron Spin Resonance Studies on Spin-Orbit Interactions
in Graphene” on Monday, 30.09.2019 at 1pm in CHyN (room 3.01).

Please support him and his work by showing up.

23
Aug

Open PhD Position: ALD of Superconducting Materials

We are seeking for a PhD candidate!

The aim of the project is to develop and to optimize high-quality superconductor-insulator-superconductor multilayer systems using atomic layer deposition (ALD). The work is carried out in close cooperation with the Helmholtz Center DESY, the Institute for Experimental Physics at Universität Hamburg (project management) and external project partners.

ALD and post-deposition processes of single and multilayer superconducting thin film structures shall be developed, characterized, and optimized. The characterization of thin films consists of structural investigations (AFM, spectrometric ellipsometry, XRD, SEM / EDX) as well as studies on the low-temperature, magnetic field-dependent transport properties of the superconducting thin films.

The job  includes participation in project communication and documentation, the presentation of the results at (inter)national workshops and conferences as well as their publication in peer-reviewed scientific journals.

If your are interested please contact Dr. Robert Zierold (rzierold@chyn.uni-hamburg.de).

23
Aug

New Publication: “Sculpturing wafer-scale nanofluidic devices for DNA single molecule analysis” in RSC Nanoscale

A new publication “Sculpturing wafer-scale nanofluidic devices for DNA single molecule analysis” of Irene’s ERC Starting Grant Group has been published today in RSC Nanoscale.

Abstract:

We present micro- and nanofluidic devices with 3D structures and nanochannels with multiple depths for the analysis of single molecules of DNA. Interfacing the nanochannels with graded and 3D inlets allows the improvement of the flow and controls not only the translocation speed of the DNA but also its conformation inside the nanochannels. The complex, multilevel, multiscale fluidic circuits are patterned in a simple, two-minute imprinting step. The stamp, the key of the technology, is directly milled by focused ion beam, which allows patterning nanochannels with different cross sections and depths, together with 3D transient inlets, all at once. Having such a variety of structures integrated in the same sample allows studying, optimizing and directly comparing their effect on the DNA flow. Here, DNA translocation is studied in long (160 µm) and short (5–40 µm) nanochannels. We study the homogeneity of the stretched molecules in long, meander nanochannels made with this technology. In addition, we analyze the effect of the different types of inlet structures interfacing short nanochannels. We observe pre-stretching and an optimal flow, and no hairpin formation, when the inlets have gradually decreasing widths and depths. In contrast, when the nanochannels are faced with an abrupt transition, we observe clogging and hairpin formation. In addition, 3D inlets strongly decrease the DNA molecules’ speed before they enter the nanochannels, and help capturing more DNA molecules. The robustness and versatility of this technology and DNA testing results evidence the potential of imprinted devices in biomedical applications as low cost, disposable lab-on-a-chip devices.
23
Aug

New Publication (Co-authorship): “3D Micromachined Polyimide Mixing Devices for in Situ X-ray Imaging of Solution-Based Block Copolymer Phase Transitions” in ACS Langmuir

A joined publication entitled “3D Micromachined Polyimide Mixing Devices for in Situ X-ray Imaging of Solution-Based Block Copolymer Phase Transitions” with the group of Prof. Martin Trebbin has been publishedin ACS Langmuir

Abstract: Advances in modern interface- and material sciences often rely on the understanding of a system’s structure–function relationship. Designing reproducible experiments that yield in situ time-resolved structural information at fast time scales is therefore of great interest, e.g., for better understanding the early stages of self-assembly or other phase transitions. However, it can be challenging to accurately control experimental conditions, especially when samples are only available in small amounts, prone to agglomeration, or if X-ray compatibility is required. We address these challenges by presenting a microfluidic chip for triggering dynamics via rapid diffusive mixing for in situ time-resolved X-ray investigations. This polyimide/Kapton-only-based device can be used to study the structural dynamics and phase transitions of a wide range of colloidal and soft matter samples down to millisecond time scales. The novel multiangle laser ablation three-dimensional (3D) microstructuring approach combines, for the first time, the highly desirable characteristics of Kapton (high X-ray stability with low background, organic solvent compatibility) with a 3D flow-focusing geometry that minimizes mixing dispersion and wall agglomeration. As a model system, to demonstrate the performance of these 3D Kapton microfluidic devices, we selected the non-solvent-induced self-assembly of biocompatible and amphiphilic diblock copolymers. We then followed their structural evolution in situ at millisecond time scales using on-the-chip time-resolved small-angle X-ray scattering under continuous-flow conditions. Combined with complementary results from 3D finite-element method computational fluid dynamics simulations, we find that the nonsolvent mixing is mostly complete within a few tens of milliseconds, which triggers initial spherical micelle formation, while structural transitions into micelle lattices and their deswelling only occur on the hundreds of milliseconds to second time scale. These results could have an important implication for the design and formulation of amphiphilic polymer nanoparticles for industrial applications and their use as drug-delivery systems in medicine.

15
Aug

Congratulations and a Warm Welcome to Chithra Harihara Sharma

Chithra has been awarded the prestigious Humboldt research fellowship for post doctoral research and has rcently joined our group.

8
Aug

New Publication (Co-authorship): “Transparency induced in opals via nanometer thick conformal coating” in Scientific Reports

A joined publication within the SFFB986  “Transparency induced in opals via nanometer thick conformal coating” led by Prof. Eich (TUHH) has been published in Scientific Reports.

Abstract: Self-assembled periodic structures out of monodisperse spherical particles, so-called opals, are a versatile approach to obtain 3D photonic crystals. We show that a thin conformal coating of only several nanometers can completely alter the reflection properties of such an opal. Specifically, a coating with a refractive index larger than that of the spherical particles can eliminate the first photonic band gap of opals. To explain this non-intuitive effect, where a nm-scaled coating results in a drastic change of optical properties at wavelengths a hundred times bigger, we split the permittivity distribution of the opal into a lattice function convoluted with that of core-shell particles as a motif. In reciprocal space, the Bragg peaks that define the first Brillouin zone can be eliminated if the motif function, which is multiplied, assumes zero at the Bragg peak positions. Therefore, we designed a non-monotonic refractive index distribution from the center of the particle through the shell into the background and adjusted the coating thickness. The theory is supported by simulations and experiments that a nanometer thin TiO2 coating via atomic layer deposition (ALD) on synthetic opals made from polystyrene particles induces nearly full transparency at a wavelength range where the uncoated opal strongly reflects. This effect paves the way for sensing applications such as monitoring the thicknesses growth in ALD in-situ and in real time as well as measuring a refractive index change without spectral interrogation.