Nano
Filtern
Dokumenttyp
- Zeitschriftenartikel (351)
- Vortrag (339)
- Posterpräsentation (102)
- Forschungsdatensatz (53)
- Sonstiges (19)
- Beitrag zu einem Tagungsband (16)
- Buchkapitel (10)
- Beitrag zu einem Sammelband (10)
- Forschungsbericht (9)
- Zeitschriftenheft (Herausgeberschaft für das komplette Heft) (6)
Sprache
- Englisch (880)
- Deutsch (52)
- Spanisch (2)
- Mehrsprachig (1)
Schlagworte
- Nanoparticles (124)
- Nano (70)
- SAXS (64)
- XPS (60)
- Laser-induced periodic surface structures (LIPSS) (59)
- Fluorescence (52)
- Quantum yield (52)
- Nanoparticle (49)
- Electron microscopy (48)
- X-ray scattering (46)
Organisationseinheit der BAM
- 6 Materialchemie (666)
- 6.1 Oberflächen- und Dünnschichtanalyse (348)
- 1 Analytische Chemie; Referenzmaterialien (185)
- 1.2 Biophotonik (161)
- 6.6 Physik und chemische Analytik der Polymere (136)
- 6.5 Synthese und Streuverfahren nanostrukturierter Materialien (131)
- 6.2 Material- und Oberflächentechnologien (90)
- 5 Werkstofftechnik (62)
- 4 Material und Umwelt (46)
- 5.4 Multimateriale Fertigungsprozesse (33)
Paper des Monats
- ja (16)
A heat treated glass that formed crystals under controlled conditions can be a glass ceramic. A proper understanding of crystallization in glassy melts is needed yet still lacking. Involved processes include the mobility of Elements within the glass during heat treatment and the reorganization of atomic bonds during crystallization. This change in coordination number of certain elements is easily observable in bulk glass samples during heat treatment with XAS. Our plan was to monitor these reorganization processes in situ at the immediate surface during heat treatment with PEEM to get time and spatial resolved data.
A summery of previous research regarding surface crystallization is given as well as results regarding thecurrent DFG project are presented.
Laser-induced periodic surface structures (LIPSS) are a universal phenomenon and can be generated on almost any material by irradiation with linearly polarized radiation. This chapter reviews the current state in the field of LIPSS, which are formed in a “self-ordered” way and are often accompanying materials processing applications. LIPSS can be produced in a single-stage process and enable surface nanostructuring and, in turn, adaption of optical, mechanical, and chemical surface properties. Typically, they feature a structural size ranging from several micrometers down to less than 100 nm and show a clear correlation with the polarization direction of the light used for their generation. Various types of LIPSS are classified, relevant control parameters are identified, and their material-specific formation mechanisms are analyzed for different types of inorganic solids, i.e., metals, semiconductors, and dielectrics. Finally, technological applications featuring surface functionalization in the fields of optics, fluidics, medicine, and tribology are discussed.
Biofilm formation in industrial or medical settings is usually unwanted and leads to serious health problems and high costs. Inhibition of initial bacterial adhesion prevents biofilm formation and is, therefore, a major mechanism of antimicrobial action of surfaces. Surface topography largely influences the interaction between bacteria and surfaces which makes topography an ideal base for antifouling strategies and eco-friendly alternatives to chemical surface modifications. Femtosecond laser-processing was used to fabricate sub-micrometric surface structures on silicon and stainless steel for the development of antifouling topographies on technical materials.
Amphiphilic polymer nanogels (NGs) are promising drug delivery vehicles that extend the application of conventional hydrophilic NGs to hydrophobic cargoes. By randomly introducing hydrophobic groups into a hydrophilic polymer network, loading and release profiles as well as surface characteristics of these colloids can be tuned. However, very little is known about the underlying internal structure of such complex colloidal architectures. Of special interest is the question how the amphiphilic network composition influences the internal morphology and the “fuzzy” surface structure. To shine light into the influence of varying network amphiphilicity on these structural features, we investigated a small library of water-swollen amphiphilic NGs using small-angle X-ray scattering (SAXS). It was found that overall hydrophilic NGs, consisting of pure poly(N-(2-hydroxypropyl)methacrylamide) (PHPMA), display a disordered internal structure as indicated by the absence of a SAXS peak. In contrast, a SAXS peak is present for amphiphilic NGs with various amounts of incorporated hydrophobic groups such as cholesteryl (CHOLA) or dodecyl (DODA). The internal composition of the NGs is considered structurally homologous to microgels. Application of the Teubner–Strey model reveals that hydrophilic PHPMA NGs have a disordered internal structure (positive amphiphilicity factor) while CHOLA and DODA samples have an ordered internal structure (negative amphiphilicity factor). From the SAXS data it can be derived that the internal structure of the amphiphilic NGs consists of regularly alternating hydrophilic and hydrophobic domains with repeat distances of 3.45–5.83 nm.
Understanding the correlation between the morphological and functional properties of particulate materials is crucial across all fields of physical and natural sciences. This manuscript reports on the investigation of the effect of polyethylene glycol (PEG) employed as a capping Agent in the synthesis of SrTiO3 crystals. The crucial influence of PEG on both the shape and size of the strontium titanate particles is revealed, highlighting the effect on the photocurrents measured under
UV–Vis irradiation.
Implant-associated infections present severe and difficult-to-treat complications after surgery, related to implant biofilm colonization. Systemic administration of antibiotics cannot reach sufficient concentrations at the infected site and may be toxic. Here we describe how mussel-inspired dendritic material coated on a titanium surface can locally activate a prodrug of daptomycin (pro-dapto) to treat methicillin-resistant Staphylococcus aureus. The mechanism of the prodrug activation is based on bio-orthogonal click chemistry between a tetrazine (Tz) and trans-cyclooctene (TCO). The former is attached to the dendritic polymer, while the later converts daptomycin into a prodrug. Characterization of the material's properties revealed that it is hydrophobic, non-toxic, and stable for a prolonged period of time. We envision that the titanium coated dendritic material will be able to improve the treatment of implant-associated infections by concentrating systemically administered antibiotic prodrugs, thus converting them into active localized medicines.
Metal-Assisted and Solvent-Mediated Synthesis of Two-Dimensional Triazine Structures on Gram Scale
(2020)
Covalent triazine frameworks are an emerging material class that have shown promising performance for a range of applications. In this work, we report on a metal-assisted and solvent-mediated reaction between calcium carbide and cyanuric chloride, as cheap and commercially available precursors, to synthesize two-dimensional triazine structures (2DTSs). The reaction between the solvent, dimethylformamide, and cyanuric chloride was promoted by calcium carbide and resulted in dimethylamino-s-triazine intermediates, which in turn undergo nucleophilic substitutions. This reaction was directed into two dimensions by calcium ions derived from calcium carbide and induced the formation of 2DTSs. The role of calcium ions to direct the two-dimensionality of the final structure was simulated using DFT and further proven by synthesizing molecular intermediates. The water content of the reaction medium was found to be a crucial factor that affected the structure of the products dramatically. While 2DTSs were obtained under anhydrous conditions, a mixture of graphitic material/2DTSs or only graphitic material (GM) was obtained in aqueous solutions. Due to the straightforward and gram-scale synthesis of 2DTSs, as well as their photothermal and photodynamic properties, they are promising materials for a wide range of future applications, including bacteria and virus incapacitation.
The oxides, hydroxides, and oxo-hydroxides of iron belong to the most abundant materials on earth. They also feature a wide range of practical applications. In many environments, they can undergo facile phase transformations and crystallization processes.
Water appears to play a critical role in many of these processes. Despite numerous attempts, the role of water has not been fully revealed yet. We present a new approach to study the influence of water in the crystallization and phase transformations of iron oxides.
The approach employs model-type iron oxide films that comprise a defined homogeneous nanostructure. The films are exposed to air containing different amounts of water reaching up to pressures of 10 bar. Ex situ analysis via scanning electron microscopy, Transmission electron microscopy, selected area electron diffraction, and X-ray diffraction is combined with operando near-ambient pressure X-ray photoelectron spectroscopy to follow water-induced changes in hematite nd ferrihydrite. Water proves to be critical for the nucleation of ematite domains in ferrihydrite, the resulting crystallite orientation, and the underlying crystallization mechanism.
Most real core-shell nanoparticle (CSNP) samples deviate from an ideal core-shell structure potentially having significant impact on the particle properties. An ideal structure displays a spherical core fully encapsulated by a shell of homogeneous thickness, and all particles in the sample exhibit the same shell thickness. Therefore,
analytical techniques are required that can identify and characterize such deviations.
This study demonstrates that by analysis of the inelastic background in X-ray photoelectron spectroscopy (XPS) survey spectra, the following types of deviations can be identified and quantified: the nonuniformity of the shell thickness within a nanoparticle sample and the incomplete encapsulation of the cores by the shell material. Furthermore, CSNP shell thicknesses and relative coverages can be obtained. These results allow for a quick and straightforward comparison between several batches of a specific CSNP, different coating approaches, and so forth. The presented XPS methodology requires a submonolayer distribution of CSNPs on a substrate.
Poly(tetrafluoroethylene)-poly(methyl methacrylate) and poly(tetrafluoroethylene)-polystyrene polymer CSNPs serve as model systems to demonstrate the applicability of the approach.
Phage display biopanning with Illumina next-generation sequencing (NGS) is applied to reveal insights into peptide-based adhesion domains for polypropylene (PP). One biopanning round followed by NGS selects robust PP-binding peptides that are not evident by Sanger sequencing. NGS provides a significant statistical base that enables motif analysis, statistics on positional residue depletion/enrichment, and data analysis to suppress false-positive sequences from amplification bias. The selected sequences are employed as water-based primers for PP-metal adhesion to condition PP surfaces and increase adhesive strength by 100% relative to nonprimed PP.
Identifying nanomaterials (NMs) according to European Union Legislation is challenging, as there is an enormous variety of materials, with different physico-chemical properties. The NanoDefiner Framework and its Decision Support Flow Scheme (DSFS) allow choosing the optimal method to measure the particle size distribution by matching the material properties and the performance of the particular measurement techniques. The DSFS leads to a reliable and economic decision whether a material is an NM or not based on scientific criteria and respecting regulatory requirements. The DSFS starts beyond regulatory requirements by identifying non-NMs by a proxy Approach based on their volume-specific surface area. In a second step, it identifies NMs. The DSFS is tested on real-world materials and is implemented in an e-tool. The DSFS is compared with a decision flowchart of the European Commission’s (EC) Joint Research Centre (JRC), which rigorously follows the explicit criteria of the EC NM definition with the focus on identifying NMs, and non-NMs are identified by exclusion. The two approaches build on the same scientific basis and measurement methods, but start from opposite ends: the JRC Flowchart starts by identifying NMs, whereas the NanoDefiner Framework first identifies non-NMs.
In this paper one refined approach is applied to determine the exact orientation of bipyramidal TiO2 nanoparticles prepared with good dispersion as almost isolated particles on a carbon TEM grid. The advantages of the recently developed high-throughput Transmission Kikuchi Diffraction (TKD) are used to identify quickly and reliably the geometrical orientation of the crystalline TiO2 nanoparticle bipyramids (anatase) on a statistically relevant number of particles.
In this contribution different ways are explored with the aim to generate suitable training data for ‘non-ideal’ samples using various approaches, e.g., computer-generated images or unsupervised learning algorithms such as generative adversarial networks (GANs). We used these data to train simple CNNs to produce segmentation masks of SEM images and tested the trained networks on real SEM images of complex nanoparticle samples. The novel use of CNN for the automated analysis of the size of nanoparticles of complex shape and with a high degree of agglomeration has proved to be a promising tool for the evaluation of particle size distribution on a large number of constituent particles. Further development and validation of the preliminary model, respectively larger training and validation data sets are necessary.
The present study addresses the capability of measurement of relative particle number concentration by scanning electron microscopy for model bimodal silica and gold samples prepared in the frame of the European research project “nPSize - Improved traceability chain of nanoparticle size measurements” as candidate reference nanoparticles.
Herein, Ti6Al4V alloy is surface modified by femtosecond laser ablation. The microstructure image obtained by secondary electron microscopy reveals a combination of micrometer spikes or cones superimposed by nanoripples (laser‐induced periodic surface structures). To make the surface hydrophilic, anodization is performed resulting in further smoothness of microstructure and a final thickness of 35 ± 4 nm is estimated for oxide produced after anodization at 10 V (scan rate = 0.1 V s−1) versus standard hydrogen electrode. The obtained electrochemically active surface area (ECSA) is approximately 8 times larger compared with flat mirror polished Ti6Al4V surface. Combined chemical analysis by Pourbaix diagram and X‐ray photoelectron spectroscopy (XPS) analyses reveal that titanium and aluminum are passivating into TiO2 and Al2O3, but the dissolution of aluminum in the form of solvated ion is inevitable. Finally, cell seeding experiments on anodized and laser‐treated titanium alloy samples show that the growth of murine fibroblast cells is significantly suppressed due to unique surface texture of the laser‐treated and anodized titanium alloy sample.
While noncovalent interactions at two-dimensional nanobiointerfaces are extensively investigated, less knowledge about covalent interactions at this interface is available. In this work, boronic acid-functionalized 2D MoS2 was synthesized and its covalent multivalent interactions with bacteria and nematodes were investigated. Polymerization of glycidol by freshly exfoliated MoS2 and condensation of 2,5-thiophenediylbisboronic acid on the produced platform resulted in boronic acid-functionalized 2D MoS2. The destructive interactions between 2D MoS2 and bacteria as well as nematodes were significantly amplified by boronic acid functional groups. Because of the high antibacterial and antinematodal activities of boronic acid-functionalized 2D MoS2, its therapeutic efficacy for diabetic wound healing was investigated. The infected diabetic wounds were completely healed 10 days after treatment with boronic acid-functionalized 2D MoS2, and a normal structure for recovered tissues including different layers of skin, collagen, and blood vessels was detected.
Irradiation with a single spatially Gaussian-shaped nanosecond laser pulse in the melting regime can result in a characteristic annular change in the surface morphology of crystalline silicon. This has been verified experimentally in a variety of situations, where dimple-shaped surface topographies are produced. In a recent work we have investigated the induced changes in the surface topography upon exposure to wavelengths in the visible and near infrared spectral region. Irradiation in the UV requires a more detailed analysis due to the enhanced absorption of the material. In the present analysis, we determine under which conditions our previous model can be used and the corresponding results are presented.
The SPONGE
(2020)