9 results
Search Results
Now showing 1 - 9 of 9
- ItemTime-resolved study of site-specific corrosion in a single crystalline silver nanoparticle(Berlin : SpringerOpen, 2019) Trautmann, Steffen; Dathe, André; Csáki, Andrea; Thiele, Matthias; Müller, Robert; Fritzsche, Wolfgang; Stranik, OndrejWe followed over 24 h a corrosion process in monocrystalline triangular-shaped nanoparticles at a single-particle level by atomic force microscopy and optical spectroscopy techniques under ambient laboratory conditions. The triangular-shaped form of the particles was selected, because the crystallographic orientation of the particles is well defined upon their deposition on a substrate. We observed that the particles already start to alter within this time frame. Surprisingly, the corrosion starts predominantly from the tips of the particles and it creates within few hours large protrusions, which strongly suppress the plasmon character of the particles. These observations support the crystallographic model of these particles consisting of a high-defect hexagonal closed packed layer, and they could help material scientists to design more stable silver nanoparticles. Moreover, this described technique can be used to reveal kinetics of the corrosion in the nanoscale of other materials.
- ItemStructural properties of magnetic nanoparticles determine their heating behavior - an estimation of the in vivo heating potential(New York, NY [u.a.] : Springer, 2014) Ludwig, R.; Stapf, M.; Dutz, S.; Müller, R.; Teichgräber, U.; Hilger, I.Magnetically induced heating of magnetic nanoparticles (MNP) in an alternating magnetic field (AMF) is a promising minimally invasive tool for localized tumor treatment by sensitizing or killing tumor cells with the help of thermal stress. Therefore, the selection of MNP exhibiting a sufficient heating capacity (specific absorption rate, SAR) to achieve satisfactory temperatures in vivo is necessary. Up to now, the SAR of MNP is mainly determined using ferrofluidic suspensions and may distinctly differ from the SAR in vivo due to immobilization of MNP in tissues and cells. The aim of our investigations was to study the correlation between the SAR and the degree of MNP immobilization in dependence of their physicochemical features.In this study, the included MNP exhibited varying physicochemical properties and were either made up of single cores or multicores. Whereas the single core MNP exhibited a core size of approximately 15 nm, the multicore MNP consisted of multiple smaller single cores (5 to 15 nm) with 65 to 175 nm diameter in total. Furthermore, different MNP coatings, including dimercaptosuccinic acid (DMSA), polyacrylic acid (PAA), polyethylenglycol (PEG), and starch, wereinvestigated. SAR values were determined after the suspension of MNP in water. MNP immobilization in tissues was simulated with 1% agarose gels and 10% polyvinyl alcohol (PVA) hydrogels.The highest SAR values were observed in ferrofluidic suspensions, whereas a strong reduction of the SAR after the immobilization of MNP with PVA was found. Generally, PVA embedment led to a higher immobilization of MNP compared to immobilization in agarose gels. The investigated single core MNP exhibited higher SAR values than the multicore MNP of the same core size within the used magnetic field parameters. Multicore MNP manufactured via different synthesis routes (fluidMAG-D, fluidMAG/12-D) showed different SAR although they exhibited comparable core and hydrodynamic sizes. Additionally, no correlation between ζ-potential and SAR values after immobilization was observed.Our data show that immobilization of MNP, independent of their physicochemical properties, can distinctly affect their SAR. Similar processes are supposed to take place in vivo, particularly when MNP are immobilized in cells and tissues. This aspect should be adequately considered when determining the SAR of MNP for magnetic hyperthermia.
- ItemNanoparticles prepared from porous silicon nanowires for bio-imaging and sonodynamic therapy(New York, NY [u.a.] : Springer, 2014) Osminkina, L.A.; Sivakov, V.A.; Mysov, G.A.; Georgobiani, V.A.; Natashina, U.А.; Talkenberg, F.; Solovyev, V.V.; Kudryavtsev, A.A.; Timoshenko, V.Y.Evaluation of cytotoxicity, photoluminescence, bio-imaging, and sonosensitizing properties of silicon nanoparticles (SiNPs) prepared by ultrasound grinding of porous silicon nanowires (SiNWs) have been investigated. SiNWs were formed by metal (silver)-assisted wet chemical etching of heavily boron-doped (100)-oriented single crystalline silicon wafers. The prepared SiNWs and aqueous suspensions of SiNPs exhibit efficient room temperature photoluminescence (PL) in the spectral region of 600 to 1,000 nm that is explained by the radiative recombination of excitons confined in small silicon nanocrystals, from which SiNWs and SiNPs consist of. On the one hand, in vitro studies have demonstrated low cytotoxicity of SiNPs and possibilities of their bio-imaging applications. On the other hand, it has been found that SiNPs can act as efficient sensitizers of ultrasound-induced suppression of the viability of Hep-2 cancer cells.
- ItemThe morphology of silver nanoparticles prepared by enzyme-induced reduction(Frankfurt, M. : Beilstein-Institut zur Förderung der Chemischen Wissenschaften, 2012) Schneidewind, H.; Schüler, T.; Strelau, K.K.; Weber, K.; Cialla, D.; Diegel, M.; Mattheis, R.; Berger, A.; Möller, R.; Popp, J.Silver nanoparticles were synthesized by an enzyme-induced growth process on solid substrates. In order to customize the enzymatically grown nanoparticles (EGNP) for analytical applications in biomolecular research, a detailed study was carried out concerning the time evolution of the formation of the silver nanoparticles, their morphology, and their chemical composition. Therefore, silvernanoparticle films of different densities were investigated by using scanning as well as transmission electron microscopy to examine their structure. Cross sections of silver nanoparticles, prepared for analysis by transmission electron microscopy were additionally studied by energy-dispersive X-ray spectroscopy in order to probe their chemical composition. The surface coverage of substrates with silver nanoparticles and the maximum particle height were determined by Rutherford backscattering spectroscopy. Variations in the silver-nanoparticle films depending on the conditions during synthesis were observed. After an initial growth state the silver nanoparticles exhibit the so-called desert-rose or nanoflower-like structure. This complex nanoparticle structure is in clear contrast to the auto-catalytically grown spherical particles, which maintain their overall geometrical appearance while increasing their diameter. It is shown, that the desert-rose-like silver nanoparticles consist of single-crystalline plates of pure silver. The surface-enhanced Raman spectroscopic (SERS) activity of the EGNP structures is promising due to the exceptionally rough surface structure of the silver nanoparticles. SERS measurements of the vitamin riboflavin incubated on the silver nanoparticles are shown as an exemplary application for quantitative analysis.
- ItemStructure of Ni(OH)2 intermediates determines the efficiency of NiO-based photocathodes – a case study using novel mesoporous NiO nanostars(Cambridge : RSC, 2019) Wahyuono, Ruri Agung; Dellith, Andrea; Schmidt, Christa; Dellith, Jan; Ignaszak, Anna; Seyring, Martin; Rettenmayr, Markus; Fize, Jennifer; Artero, Vincent; Chavarot-Kerlidou, Murielle; Dietzek, BenjaminWe report the wet chemical synthesis of mesoporous NiO nanostars (NS) as photocathode material for dye-sensitized solar cells (DSSCs). The growth mechanism of NiO NS as a new morphology of NiO is assessed by TEM and spectroscopic investigations. The NiO NS are obtained upon annealing of preformed β-Ni(OH)2 into pristine NiO with low defect concentrations and favorable electronic configuration for dye sensitization. The NiO NS consist of fibers self-assembled from nanoparticles yielding a specific surface area of 44.9 m2 g-1. They possess a band gap of 3.83 eV and can be sensitized by molecular photosensitizers bearing a range of anchoring groups, e.g. carboxylic acid, phosphonic acid, and pyridine. The performance of NiO NS-based photocathodes in photoelectrochemical application is compared to that of other NiO morphologies, i.e. nanoparticles and nanoflakes, under identical conditions. Sensitization of NiO NS with the benchmark organic dye P1 leads to p-DSSCs with a high photocurrent up to 3.91 mA cm-2 whilst the photoelectrochemical activity of the NiO NS photocathode in aqueous medium in the presence of an irreversible electron acceptor is reflected by generation of a photocurrent up to 23 μA cm-2 © 2019 The Royal Society of Chemistry.
- ItemPeculiarities of electronic structure and composition in ultrasound milled silicon nanowires(Amsterdam [u.a.] : Elsevier, 2020) Parinova, E.V.; Pisliaruk, A.K.; Schleusener, A.; Koyuda, D.A.; Chumakov, R.G.; Lebedev, A.M.; Ovsyannikov, R.; Makarova, A.; Smirnov, D.; Sivakov, V.; Turishchev, S.Yu.The combined X-ray absorption and emission spectroscopy approach was applied for the detailed electronic structure and composition studies of silicon nanoparticles produced by the ultrasound milling of heavily and lowly doped Si nanowires formed by metal-assisted wet chemical etching. The ultrasoft X-ray emission spectroscopy and synchrotron based X-ray absorption near edges structure spectroscopy techniques were utilize to study the valence and conduction bands electronic structure together with developed surface phase composition qualitative analysis. Our achieved results based on the implemented surface sensitive techniques strongly suggest that nanoparticles under studies show a significant presence of the silicon suboxides depending on the pre-nature of initial Si wafers. The controlled variation of the Si nanoparticles surface composition and electronic structure, including band gap engineering, can open a new prospective for a wide range Si-based nanostructures application including the integration of such structures with organic or biological systems. © 2020
- ItemSPION@polydehydroalanine hybrid particles(London : RSC Publishing, 2015) von der Lühe, Moritz; Günther, Ulrike; Weidner, Andreas; Gräfe, Christine; Clement, Joachim H.; Dutz, Silvio; Schacher, Felix H.It is generally accepted that a protein corona is rapidly formed upon exposure of nanoparticles to biological fluids and that both the amount and the composition of adsorbed proteins affect the dispersion properties of the resulting particles. Hereby, the net charge and overall charge density of the pristine nanoparticles are supposed to play a crucial role. In an attempt to control both charge and charge distribution, we report on the coating of superparamagnetic iron oxide nanoparticles (SPIONs) with different polyelectrolytes. Starting from orthogonally protected polydehydroalanine, the material can be easily transformed into a polyanion (poly(tert-butoxycarbonyl acrylic acid), PtBAA), polycation (poly(aminomethylacrylate), PAMA), or even a polyzwitterion (polydehydroalanine, PDha). While coating of SPIONs with PtBAA and PDha was shown to be successful, approaches using PAMA have failed so far. The dispersion properties of the resulting hybrid particles have been investigated using dynamic light scattering (DLS), zeta-potential, and TEM measurements – the amount of adsorbed polymer was quantified using vibrating sample magnetometry (VSM) and thermogravimetric analysis (TGA).
- ItemPropagating and localized surface plasmon resonance sensing — A critical comparison based on measurements and theory(Amsterdam [u.a.] : Elsevier, 2016) Jatschka, Jacqueline; Dathe, André; Csáki, Andrea; Fritzsche, Wolfgang; Stranik, OndrejWith its potential for ultrasensitive, label-free detection of molecular interactions, sensing methods based on the surface plasmon resonance (SPR) effect fully meet the requirements for modern analytical techniques. Already established by using propagating SPR in thin gold layers, the last years witnessed the emergence of another related technique utilizing extremely miniaturized noble metal sensor structures, based on a localized SPR. This paper provides a critical comparison of these kinds of SPR sensing, reviews the foundation of both general approaches, presents experimental data on exactly the same molecular model system using both techniques, as well as theoretical considerations in order to allow reasonable comparison. It highlights the specific features and effects, in order to provide guidance in choosing the right technique for given bioanalytical tasks. The study demonstrated the capabilities of LSPR for sensing of molecular layers even in the lower nanometer dimension. For the detection of small (bio)molecules, smaller particle diameters are favored regarding highest sensitivity. It also presents an approach to obtain refractive index and the thickness of a molecular film by analyzing the signal response of plasmonic sensors with metal nanoparticles. Moreover, an additional method for the improvement of the parameters' determination is introduced.
- ItemMechanistic insight into the non-hydrolytic sol–gel process of tellurite glass films to attain a high transmission(Cambridge : RSC, 2020) Pan, Xuanzhao; Zhao, Jiangbo; Qian, Gujie; Zhang, Xiaozhou; Ruan, Yinlan; Abell, Andrew; Ebendorff-Heidepriem, HeikeThe development of amorphous films with a wide transmission window and high refractive index is of growing significance due to the strong demand of integrating functional nanoparticles for the next-generation hybrid optoelectronic films. High-index TeO2-based glass films made via the sol-gel process are particularly suitable as their low temperature preparation process promises high compatibility with a large variety of nanoparticles and substrates that suffer from low thermal stability. However, due to the lack of in-depth understanding of the mechanisms of the formation of undesired metallic-Te (highly absorbing species) in the films, the preparation of high-transmission TeO2-based sol-gel films has been severely hampered. Here, by gaining insight into the mechanistic chemistry of metallic-Te formation at different stages during the non-hydrolytic sol-gel process, we identify the chemical route to prevent the generation of metallic-Te in a TeO2-based film. The as-prepared TeO2-based film exhibits a high transmission that is close to the theoretical limit. This opens up a new avenue for advancing the performance of hybrid optoelectronic films via incorporating a large variety of unique nanoparticles. © 2020 The Royal Society of Chemistry.