10 results on '"Prymak, O."'
Search Results
2. Structural Evolution of Silver Nanoparticles duringWet-Chemical Synthesis.
- Author
-
Banerjee, S., Loza, K., Meyer-Zaika, W., Prymak, O., and Epple, M.
- Published
- 2014
- Full Text
- View/download PDF
3. The Molecular Footprint of Peptides on the Surface of Ultrasmall Gold Nanoparticles (2 nm) Is Governed by Steric Demand.
- Author
-
Wagner LS, Prymak O, Schaller T, Beuck C, Loza K, Niemeyer F, Gumbiowski N, Kostka K, Bayer P, Heggen M, Oliveira CLP, and Epple M
- Subjects
- Surface Properties, Particle Size, Gold chemistry, Metal Nanoparticles chemistry, Peptides chemistry
- Abstract
Ultrasmall gold nanoparticles were functionalized with peptides of two to seven amino acids that contained one cysteine molecule as anchor via a thiol-gold bond and a number of alanine residues as nonbinding amino acid. The cysteine was located either in the center of the molecule or at the end (C-terminus). For comparison, gold nanoparticles were also functionalized with cysteine alone. The particles were characterized by UV spectroscopy, differential centrifugal sedimentation (DCS), high-resolution transmission electron microscopy (HRTEM), and small-angle X-ray scattering (SAXS). This confirmed the uniform metal core (2 nm diameter). The hydrodynamic diameter was probed by
1 H-DOSY NMR spectroscopy and showed an increase in thickness of the hydrated peptide layer with increasing peptide size (up to 1.4 nm for heptapeptides; 0.20 nm per amino acid in the peptide).1 H NMR spectroscopy of water-dispersed nanoparticles showed the integrity of the peptides and the effect of the metal core on the peptide. Notably, the NMR signals were very broad near the metal surface and became increasingly narrow in a distance. In particular, the methyl groups of alanine can be used as probe for the resolution of the NMR spectra. The number of peptide ligands on each nanoparticle was determined using quantitative1 H NMR spectroscopy. It decreased with increasing peptide length from about 100 for a dipeptide to about 12 for a heptapeptide, resulting in an increase of the molecular footprint from about 0.1 to 1.1 nm2 .- Published
- 2024
- Full Text
- View/download PDF
4. Integrated In Situ Fabrication of CuO Nanorod-Decorated Polymer Membranes for the Catalytic Flow-Through Reduction of p -Nitrophenol.
- Author
-
Hesaraki SAH, Prymak O, Heidelmann M, Ulbricht M, and Fischer L
- Abstract
We developed a novel method to fabricate copper nanorods in situ in a poly(ether sulfone) (15 wt %) casting solution by a sonochemical reduction of Cu
2+ ions with NaBH4 . The main twist is the addition of ethanol to remove excess NaBH4 through Cu(0) catalyzed ethanolysis. This enabled the direct use of the resulting copper-containing casting dispersions for membrane preparation by liquid nonsolvent-induced phase separation and led to full utilization of the copper source, generating zero metal waste. We characterized the copper nanorods as presented in the membranes via scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and UV/vis spectroscopy. We could demonstrate that the rapid immobilization from reducing conditions led to the membrane incorporation of copper nanorods in a state of high reactivity, which also promoted the complete oxidation to CuO after fabrication. We further observed a large aspect ratio and crystal straining of the nanorods, likely resulting from growth around the matrix polymer. The entanglement with poly(ether sulfone) further facilitated a selective presentation at the pore surface of the final CuO-decorated membranes. The membranes also exhibit high water permeances of up to 2800 L/m2 hbar. Our catalytic membranes achieved exceptionally high activities in the aqueous flow-through reduction of p -nitrophenol ( p -NP), with turnover frequencies of up to 115 h-1 , even surpassing those of other state-of-the-art catalytic membranes that incorporate Pd or Ag. Additionally, we demonstrated that catalytic hydrolysis of the reducing agent in water can lead to hydrogen gas formation and blocking of active sites during continuous catalytic p -NP hydrogenation. We illustrated that the accompanying conversion loss can be mitigated by facilitated gas transport in the water-filled pores, which is dependent on the orientation of the pore size gradient and the flow direction.- Published
- 2024
- Full Text
- View/download PDF
5. Ultrastructure and Surface Composition of Glutathione-Terminated Ultrasmall Silver, Gold, Platinum, and Alloyed Silver-Platinum Nanoparticles (2 nm).
- Author
-
Wolff N, Loza K, Heggen M, Schaller T, Niemeyer F, Bayer P, Beuck C, Oliveira CLP, Prymak O, Weidenthaler C, and Epple M
- Abstract
Alloyed ultrasmall silver-platinum nanoparticles (molar ratio Ag:Pt = 50:50) were prepared and compared to pure silver, platinum, and gold nanoparticles, all with a metallic core diameter of 2 nm. They were surface-stabilized by a layer of glutathione (GSH). A comprehensive characterization by high-resolution transmission electron microscopy (HRTEM), electron diffraction (ED), X-ray diffraction (XRD), small-angle X-ray scattering (SAXS), differential centrifugal sedimentation (DCS), and UV spectroscopy showed their size both in the dry and in the water-dispersed state (hydrodynamic diameter). Solution NMR spectroscopy (
1 H,13 C, COSY, HSQC, HMBC, and DOSY) showed the nature of the glutathione shell including the number of GSH ligands on each nanoparticle (about 200 with a molecular footprint of 0.063 nm2 each). It furthermore showed that there are at least two different positions for the GSH ligand on the gold nanoparticle surface. Platinum strongly reduced the resolution of the NMR spectra compared to silver and gold, also in the alloyed nanoparticles. X-ray photoelectron spectroscopy (XPS) showed that silver, platinum, and silver-platinum particles were at least partially oxidized to Ag(+I) and Pt(+II), whereas the gold nanoparticles showed no sign of oxidation. Platinum and gold nanoparticles were well crystalline but twinned (fcc lattice) despite the small particle size. Silver was crystalline in electron diffraction but not in X-ray diffraction. Alloyed silver-platinum nanoparticles were almost fully amorphous by both methods, indicating a considerable internal disorder.- Published
- 2023
- Full Text
- View/download PDF
6. Tuning the Fluorescence in Dynamic Covalent Bonded Liquid Crystals.
- Author
-
Blanke M, Neumann T, Gutierrez Suburu ME, Prymak O, Wölper C, Strassert CA, and Giese M
- Abstract
A series of emissive liquid crystalline materials based on salicylidene derivatives is reported and investigated with respect to their thermoresponsive and mechanochromic properties. Single-crystal analysis and temperature-dependent powder X-ray diffraction measurements allowed us to correlate the intermolecular organization of the mesogens with thermoresponsive changes in the fluorescence behavior. As a proof-of-principle study, we employed the dynamics of the imine bond in transamination reactions for postsynthetic tuning of the fluorescence behavior as a further step toward the development of adaptive materials.
- Published
- 2022
- Full Text
- View/download PDF
7. Water-Based Synthesis of Ultrasmall Nanoparticles of Platinum Group Metal Oxides (1.8 nm).
- Author
-
Wetzel O, Prymak O, Loza K, Gumbiowski N, Heggen M, Bayer P, Beuck C, Weidenthaler C, and Epple M
- Subjects
- Platinum chemistry, Water chemistry, X-Ray Diffraction, Metal Nanoparticles chemistry, Oxides chemistry
- Abstract
Ultrasmall nanoparticles of platinum group metal oxides (core diameter of about 1.8 nm) were prepared by alkaline hydrolysis of metal precursors in the presence of NaBH
4 and by colloidal stabilization with tripeptide glutathione. We obtained water-dispersed nanoparticles of Rh2 O3 , PdO, RuO2 , IrO2 , Os/OsO2 , and Pt/PtO. Their size was probed using high-resolution transmission electron microscopy, differential centrifugal sedimentation, small-angle X-ray scattering, and diffusion-ordered1 H NMR spectroscopy (1 H DOSY). Their oxidation state was clearly determined using X-ray photoelectron spectroscopy, X-ray powder diffraction, and electron diffraction. The chemical composition of the nanoparticles, that is, the ratio of the metal oxide core and glutathione capping agent, was quantitatively determined by a combination of these methods.- Published
- 2022
- Full Text
- View/download PDF
8. Metal-Ligand Interface and Internal Structure of Ultrasmall Silver Nanoparticles (2 nm).
- Author
-
Wetzel O, Hosseini S, Loza K, Heggen M, Prymak O, Bayer P, Beuck C, Schaller T, Niemeyer F, Weidenthaler C, and Epple M
- Subjects
- HeLa Cells, Humans, Ligands, Particle Size, Scattering, Small Angle, X-Ray Diffraction, Metal Nanoparticles toxicity, Silver
- Abstract
Ultrasmall silver nanoparticles were prepared by reduction with NaBH
4 and surface-terminated with glutathione (GSH). The particles had a solid core diameter of 2 nm as shown by transmission electron microscopy (TEM) and small-angle X-ray scattering (SAXS). NMR-DOSY gave a hydrodynamic diameter of 2 to 2.8 nm. X-ray photoelectron spectroscopy (XPS) showed that silver is bound to the thiol group of the central cysteine in glutathione under partial oxidation to silver(+I). In turn, the thiol group is deprotonated to thiolate. X-ray powder diffraction (XRD) together with Rietveld refinement confirmed a twinned (polycrystalline) fcc structure of ultrasmall silver nanoparticles with a lattice compression of about 0.9% compared to bulk silver metal. By NMR spectroscopy, the interaction between the glutathione ligand and the silver surface was analyzed, also with13 C-labeled glutathione. The adsorbed glutathione is fully intact and binds to the silver surface via cysteine. In situ1 H NMR spectroscopy up to 85 °C in dispersion showed that the glutathione ligand did not detach from the surface of the silver nanoparticle, i.e. the silver-sulfur bond is remarkably strong. The ultrasmall nanoparticles had a higher cytotoxicity than bigger particles in in vitro cell culture with HeLa cells with a cytotoxic concentration of about 1 μg mL-1 after 24 h incubation. The overall stoichiometry of the nanoparticles was about Ag∼250 GSH∼155 .- Published
- 2021
- Full Text
- View/download PDF
9. Factors Affecting the Nonsolvent-Induced Phase Separation of Cellulose from Ionic Liquid-Based Solutions.
- Author
-
Wittmar ASM, Koch D, Prymak O, and Ulbricht M
- Abstract
In the present work, we report for the first time an in-depth study of the factors influencing porous cellulose film structure formation during the nonsolvent-induced phase separation (NIPS) process from biopolymer solutions in ionic liquid-based solvents. The length of the alkyl chain of the ionic liquid's cation, the solvent/co-solvent ratio, and the type of the cellulose precursor used were found to have great influence both on cellulose solution formation and properties and to the NIPS process with water acting as nonsolvent. In the undiluted form, both studied ionic liquids proved to dissolve almost equally well the cellulose; however, due to differences in viscosities of the formed biopolymer solutions and due to differences in miscibility with water of the two ionic liquids, the used ionic liquid had a strong influence on the film's porous structure formation. The use of increasing amounts of an aprotic co-solvent, here dimethylsulfoxide, improved biopolymer solubilization and also led to the formation of a more pronounced macroporous structure during the NIPS process. The cellulose type also affected the porous structure generation during the NIPS process: with the increase of the molecular weight of the precursor, the viscosity of the formed biopolymer solution increased and the tendency to generate macroporous structures decreased., Competing Interests: The authors declare no competing financial interest., (© 2020 American Chemical Society.)
- Published
- 2020
- Full Text
- View/download PDF
10. Solution-based synthesis of GeTe octahedra at low temperature.
- Author
-
Schulz S, Heimann S, Kaiser K, Prymak O, Assenmacher W, Brüggemann JT, Mallick B, and Mudring AV
- Abstract
GeTe octahedra were prepared by reaction of equimolar amounts of GeCl2·dioxane and Te(SiEt3)2 in oleylamine, whereas a slight excess of the Te precursor yielded GeTe octahedra decorated with elemental Te nanowires, which can be removed by washing with TOP. The mechanism of the GeTe formation is strongly influenced by the solvent. The expected elimination of Et3SiCl (dehalosilylation) only occurred in aprotic solvents, whereas Te(SiEt3)2 was found to react with primary and secondary amines with formation of silylamines. Temperature-dependent studies on the reaction in oleylamine showed that crystalline GeTe particles are formed at temperatures higher than 140 °C. XRD, SAED, and HRTEM studies proved the formation of rhombohedral GeTe nanoparticles. These findings were confirmed by a single-crystal and powder X-ray analysis. The rhombohedral structure modification was found, and the structure was solved in the acentric space group R3m.
- Published
- 2013
- Full Text
- View/download PDF
Catalog
Discovery Service for Jio Institute Digital Library
For full access to our library's resources, please sign in.