Papers by Michael Giersig
Chemistry of Materials, 2007
Response. -Au-CoPt 3 , Ag-CoPt 3 , and Au-FePt nanoparticles are prepared from CoPt3 and FePt nan... more Response. -Au-CoPt 3 , Ag-CoPt 3 , and Au-FePt nanoparticles are prepared from CoPt3 and FePt nanoparticles which are transferred into water using cetyltrimethylammonium bromide as a phase-transfer agent and subsequently used as seeding materials for the reduction of Au and Pt precursors (HAuCl4 or AgNO3) using a seeded-growth method. The samples are characterized by TEM, UV/VIS spectroscopy, and magnetic measurements. By control of the growth conditions, Au-CoPt 3 nanocomposites with various morphologies (spheres, cubes, rods) are obtained, making possible to tailor the optical response of these composite nanoparticles while maintaining the magnetic properties of the original seeds, even upon transfer into water. Magnetically active nanoparticles with a tunable optical response in an aqueous environment should find applications in biological and medical research. -(PAZOS-PEREZ, N.; GAO, Y.; HILGENDORFF, M.; IRSEN, S.; PEREZ-JUSTE, J.; SPASOVA, M.; FARLE, M.; LIZ-MARZAN, L. M.; GIERSIG*, M.; Chem.
Journal of Physical Chemistry C, 2008
... figure Figure 6 Top: XANES of ZnO:Co nanorods perform Co K-edge in comparison to reference da... more ... figure Figure 6 Top: XANES of ZnO:Co nanorods perform Co K-edge in comparison to reference data of Co, CoO, and Co 3 O 4 taken from ref 39 Copyright 2006 Elsevier Limited. All spectra are normalized to unity; reference spectra are shifted vertically for clarity. ...
During the last decade, an increasing interest has been devoted to the analysis of the interplay ... more During the last decade, an increasing interest has been devoted to the analysis of the interplay between plasmon resonances and magneto-optical (MO) effects [1], since the plasmon resonances can be used to enhance the MO response [2-4] and the MO effect can be used to control the plasmon propagation [5]. A great number of the studies of the MO enhancement due to plasmon excitation have been carried out in the so-called Polar Kerr configuration for MO active nanostructures (either dots or antidots) [2] or when metal nanostructures have been put into contact with continuous films of MO active material [3]. However, in the Transverse Kerr configuration the studies focus on metallic nanostructures over continuous films [4].
The Journal of Physical Chemistry, 1994
Improved synthetic routes and sizeselective precipitation have enabled the preparation of almost ... more Improved synthetic routes and sizeselective precipitation have enabled the preparation of almost monodisperse CdS clusters. Six samples of 1-thioglycerol stabilized clusters with diameters of approximately 13, 14, 16, 19, 23, and 39 A have been prepared as fully redispersible powders and were characterized by elemental analysis, powder X-ray diffraction, electron microscopy, thermogravimetric analysis, and UV-vis spectroscopy. Smallangle X-ray scattering was used to determine the mean cluster size. The well-structured UV-vis spectra reveal that the size-dependent shift of the 1s-1s excitonic transition is in agreement with the tight-binding theory and the pseudopotential theory. Moreover, as expected by quantum mechanical calculations the oscillator strength of the transition increases proportional to l/+. UV-vis spectra taken at various temperatures between 4 and 295 K have shown that the temperature shift of the excitonic transition energy becomes stronger with decreasing particle size. Strong, reversible absorbance shifts were observed, upon transferring the clusters from their solutions onto quartz plates and vice versa. Abstract published in Aduunce ACS Abstracts, June 15, 1994.
Conference Record of the Twenty-Eighth IEEE Photovoltaic Specialists Conference - 2000 (Cat. No.00CH37036), 2000
A Zn(Se,OH) buffer layer deposited by chemical bath process on Cu(In,Ga)(S,Se)2 (CIGSS) absorbers... more A Zn(Se,OH) buffer layer deposited by chemical bath process on Cu(In,Ga)(S,Se)2 (CIGSS) absorbers is investigated. Before deposition of the actual ZnSe layer, the absorber is immersed in a Zn-containing solution (Zn treatment). Transmission electron microscopy (TEM) pictures of the buffer layer exhibit two different areas: a dark structured layer containing small crystals of ZnSe and a bright amorphous layer, which is thought to consist of Zn(OH)2 predominantly. We suggest that already during the Zn treatment an amorphous buffer layer is growing. X-ray photoelectron spectroscopy (XPS) measurements of the Cu2p and O1s peak of Zn-treated absorbers show a coverage with an OH component, attributed to Zn(OH)2. Nuclear reaction analysis (NRA) measurements reveal a peak hydrogen concentration of 8×1021 H/cm3 in the buffer layer. Micro-Raman spectra show a shift of the LO branch of ZnSe from 250 cm-1 to 258 cm-1
The Journal of Physical Chemistry, 1993
Gold was deposited onto colloidal silver (mean particle size 76 A) in aqueous solution, and the c... more Gold was deposited onto colloidal silver (mean particle size 76 A) in aqueous solution, and the composite particles were studied by spectrophotometry and electron microscopy. The deposition took place via electron transfer onto the silver particles by radiolytically generated free ...
MRS Proceedings, 2004
Gram positive (Lactoccocus lactis) and Gram negative bacteria (Escherichia coli) were used to stu... more Gram positive (Lactoccocus lactis) and Gram negative bacteria (Escherichia coli) were used to study the interaction of water-dispersible muti-walled carbon nanotubes (CNTs) with the bacterial cell envelope during microwave (MW) energy exposure. It was observed that the addition of a tiny amount of CNTs to a medium containing bacteria and subsequent exposure of the samples to MW, leads to an intimate contact between the CNT tips and the cell envelope. This phenomenon can be explained in terms of attractive forces between opposite charges of polar structures. Since CNTs under MW irradiation behave like electric dipoles, this would make it possible for the CNTs to target the cell surface without inducing changes in the cell shape and viability. Thus, the electrochemical properties of CNTs and their capillarity make them useful tools for cell manipulation, and therefore for the intracellular transport of drugs, dyes or biomolecules.
We are presenting for the first time that vertically aligned carbon nanotubes can be used for fab... more We are presenting for the first time that vertically aligned carbon nanotubes can be used for fabrication of large-scale arrays of nanocoax cables. Multicoating with insulating and metallic layers results in a coaxial structure where light can be transmitted along the nanotube axis in the visible frequency range. We have shown that unlike simple optical waveguides, coaxial nanocables exhibit subwavelength
Small, 2005
The cover picture shows an ordered array of iron nanorings, which were prepared by means of shado... more The cover picture shows an ordered array of iron nanorings, which were prepared by means of shadow nanosphere lithography. By altering the nature of the mask used in the procedure, rods, dots, as well as rings can be prepared (the insets show computer simulations of the types of shapes that might be achieved). For more information, please read "Fabrication of Nanoscale Rings, Dots, and Rods by Combining Shadow Nanosphere Lithography and Annealed Polystyrene Nanosphere Masks" by M. Giersig and co-workers on page 439ff.
The Journal of Physical Chemistry B, 1999
... Completely Green Synthesis and Stabilization of Metal Nanoparticles. ... Abstract: In the p... more ... Completely Green Synthesis and Stabilization of Metal Nanoparticles. ... Abstract: In the present Communication, a completely green synthetic method for producing silver nanoparticles is introduced. The process is simple, environmentally benign, and quite efficient. ...
Solar Energy Materials and Solar Cells, 2003
ABSTRACT Structural and compositional properties of Zn(Se,OH)/Zn(OH)2 buffer layers deposited by ... more ABSTRACT Structural and compositional properties of Zn(Se,OH)/Zn(OH)2 buffer layers deposited by chemical bath deposition(CBD) on Cu(In,Ga)(S,Se)2 (CIGSS) absorbers are investigated. Due to the aqueous nature of the CBD process, oxygen and hydrogen were incorporated into the ‘ZnSe’ buffer layer mainly in the form of Zn(OH)2 as is shown by X-ray photoelectron spectroscopy and nuclear reaction analysis (NRA) measurements leading to the nomenclature ‘Zn(Se,OH)’. Prior to the deposition of Zn(Se,OH), a zinc treatment of the absorber was performed. During that treatment a layer mainly consisting of Zn(OH)2 grew to a thickness of several nanometer. The whole buffer layer therefore consists of a Zn(Se,OH)/Zn(OH)2 structure on CIGSS. Part of the Zn(OH)2 in both layers (i.e. the Zn(Se,OH) and the Zn(OH)2 layer) might be converted into ZnO during measurements or storage. Scanning electron microscopy pictures showed that a complete coverage of the absorber with the buffer layer was achieved. Transmission electron microscopy revealed the different regions of the buffer layer: An amorphous area (possibly Zn(OH)2) and a partly nanocrystalline area, where lattice planes of ZnSe could be identified. Solar cell efficiencies of ZnO/Zn(Se,OH)/Zn(OH)2/CIGSS devices exceed 14% (total area).
Small, 2005
The application of shadow nanosphere lithography for the preparation of large-area, two-dimension... more The application of shadow nanosphere lithography for the preparation of large-area, two-dimensional, metallic nanostructures of different shape is described. Through changing the mask morphology by temperature processing and varying the evaporation conditions, particles with morphologies such as rings, rods, and dots have been produced. This process allows outstanding control of the size and morphology of the particles. The efficient technique is shown to scale down the size of metallic nanoparticles from 200 to 30 nm, while preserving the original nanosphere spacing and order. The 150-nm-diameter Fe rings produced by this method show ferromagnetic behavior, which was predicted by theoretical simulation. All the experimental results were confirmed by computer simulations, which also showed the possibility of creating periodic arrays of any other geometrical shape.
Small, 2009
A fast and cheap, large-area (>1 cm 2 ), high-coverage fabrication technique for periodic metalli... more A fast and cheap, large-area (>1 cm 2 ), high-coverage fabrication technique for periodic metallic split-ring resonator metamaterials is presented, which allows control of inner-and outer-ring diameters, gap angles, as well as thickness and periodicity. This method, based on shadow nanosphere lithography, uses tilted-angle-rotation thermal evaporation onto Langmuir-Blodgett-type monolayers of close-packed polystyrene nanospheres. Excellent agreement of the process parameters with a simplified model is demonstrated. Pronounced, tunable optical metamaterial resonances in the range of 100 THz are consistent with simulations.
Physical Chemistry Chemical Physics, 2007
Journal of the American Chemical Society, 1998
A detonation of molten (Et 3 N)Ga(N 3 ) 3 (mp = 43 °C) in a sealed 71 mL stainless steel pressure... more A detonation of molten (Et 3 N)Ga(N 3 ) 3 (mp = 43 °C) in a sealed 71 mL stainless steel pressure vessel equipped with a pressure gauge (350 bar; Parr instruments, 4740 bomb) under inert gas (N 2 ) was induced by rapid heating (30 °C/min) to 400 °C. After the observation of a ...
Journal of Physics D: Applied Physics, 2000
We present a new method for the determination of the magnetic moment distribution ρ(µ) of ferrofl... more We present a new method for the determination of the magnetic moment distribution ρ(µ) of ferrofluid particles from the magnetization curve measured on diluted ferrofluid samples in the liquid state. The method employs the solution of the standard integral equation describing the magnetization of a non-interacting particle system in the given external field as a convolution of the Langevin function with the distribution of particle moments. No a priori assumptions concerning the shape of the corresponding distribution are required. We present the reconstruction results obtained both for the computer simulated magnetization curves and for real experimental data. In the latter case we compare the distributions found using our algorithm with those calculated from the particle size distributions obtained via the electron microscopy images of the ferrofluid particles.
European Journal of Pharmacology, 2006
Nanotechnology provides new materials in the nanometer range with many potential applications in ... more Nanotechnology provides new materials in the nanometer range with many potential applications in clinical medicine and research. Due to their unique size-dependent properties nanomaterial such as nanoparticles offer the possibility to develop both new therapeutic and diagnostic tools. Thus, applied nanotechnology to medical problemsnanomedicinecan offer new concepts that are reviewed.
Journal of Materials Chemistry, 1999
... In particular, the possible role of reaction equilibria has been disregarded, as well as mutu... more ... In particular, the possible role of reaction equilibria has been disregarded, as well as mutual interference of diffusion of ALT and HAL at high concentration. ... Lett., 1998, 8, 849. 22 TJ Bastow, AF Moodie, ME Smith and HJ Whitfield, J. Mater. Chem., 1993, 3, 697. ...
Current Drug Targets, 2006
Nanoparticles are at the leading edge of the rapidly developing field of material science in nano... more Nanoparticles are at the leading edge of the rapidly developing field of material science in nanotechnology with many potential applications in clinical medicine and research. Due to their unique size-dependent properties nanoparticles offer the possibility to develop both new therapeutic and diagnostic tools. The ability to incorporate drugs into nanosystems displays a new paradigm in pharmacotherapy that could be used for cell-targeted drug delivery. Nontargeted nanosystems such as nanocarriers that are coated with polymers or albumin and solid lipid particles have been used to transport a large number of compounds. However, nowadays drugs can be coupled to nanocarriers that are specific for cells and/or organs. Thus, drugs that are either trapped within the carriers or deposited in subsurface oil layers could be specifically delivered to organs, tumors and cells. These strategies can be used to concentrate drugs in selected target tissues thus minimizing systemic side effects and toxicity. In addition to these therapeutic options, nanoparticle-based "molecular" imaging displays a field in which this new technology has set the stage for an evolutionary leap in diagnostic imaging. Based on the recent progress in nanobiotechnology, nanoparticles have the potential to become useful tools as therapeutic and diagnostic tools in the near future.
Journal of Chromatography A, 1994
Wide-bore hydrodynamic chromatography in a polyether ether ketone [PEEK) capillary (I.D. 0.7 mm, ... more Wide-bore hydrodynamic chromatography in a polyether ether ketone [PEEK) capillary (I.D. 0.7 mm, length 20 m) was used to determine the weight average diameter d, of colloidal particles. The method was applied to cadmium sulphide and gold sols in the diameter range between 3 nm and 27 nm. The method is based on the radial distribution of the analyte in the capillary due to the hydrodynamic flow profile in the capillary and due to the diffusion coefficient of the particles, which is dependent on their diameter. The diameter was calculated from the ratio of the heights of convection peak and diffusion peak. The size-quantization effect of small semiconductor particles made it possible to visualise the separation inside of the capillary. One important advantage of the applied method is the very much reduced adsorption, which often causes serious problems in the HPLC especially of inorganic colloids. The results of wide-bore hydrodynamic chromatography, size exclusion chromatography and transmission electron microscopy were compared.
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Papers by Michael Giersig