Refine
Year of publication
Document Type
Is part of the Bibliography
- yes (139) (remove)
Keywords
- calcium phosphate (9)
- Ionic liquids (7)
- ionic liquids (7)
- biomineralization (5)
- ionic liquid (5)
- poly(lactic acid) (5)
- 3D printing (4)
- activated carbon (4)
- brushite (4)
- dye removal (4)
- electrochemistry (4)
- hydroxyapatite (4)
- ionic conductivity (4)
- methyl orange (4)
- methylene blue (4)
- silver nanoparticles (4)
- water treatment (4)
- biomaterials (3)
- cellulose (3)
- erosion (3)
- ionogels (3)
- nanocomposite (3)
- nanoparticles (3)
- oxidative stress (3)
- roughness (3)
- sodium hydroxide etching (3)
- surface modification (3)
- water (3)
- wettability (3)
- 11-mercaptoundecanoic acid (2)
- 3-mercaptopropionic acid (2)
- 4-nitrophenol (2)
- Adsorbent (2)
- AgI (2)
- Alkylpyridinium salts (2)
- Arabica coffee (2)
- Bombyx mori silk (2)
- Calcium phosphate (2)
- Carica papaya seeds (2)
- Catalysis (2)
- Cd-free (2)
- Complex (2)
- E. coli (2)
- EDTA (2)
- Electrospinning (2)
- Gas (2)
- Hybrid materials (2)
- InP (2)
- InPZnS (2)
- Ionic Liquid Precursor (2)
- Ionogels (2)
- Kaolinite (2)
- Kinetics (2)
- LC-MS/MS (2)
- Laser-SNMS (2)
- Mineralization (2)
- NTA (2)
- Nanostructures (2)
- PLA (2)
- Phase transitions (2)
- QDs (2)
- Salts (2)
- Solvents (2)
- Structure elucidation (2)
- Thermochromism (2)
- ToF-SIMS (2)
- Water treatment (2)
- X-ray diffraction (2)
- aqueous dispersion (2)
- biomaterial (2)
- biomimetic mineralization (2)
- bound phenolic compounds (2)
- cadmium-free (2)
- calcination (2)
- calcium carbonate (2)
- calcium phosphate hybrid material (2)
- carbon dots (2)
- chitosan (2)
- clay (2)
- coffee by-products (2)
- coffee processing (2)
- cryogel (2)
- dip-coating (2)
- dye adsorption (2)
- dye mixture (2)
- gelatin (2)
- gold (2)
- hybrid materials (2)
- hybrid nanomaterials (2)
- hydrogel (2)
- hydroyxapatite (2)
- imidazolium (2)
- ionic liquid crystals (2)
- ionic liquid precursors (2)
- ionogel (2)
- ligand exchange (2)
- luminescence (2)
- mechanical properties (2)
- mechanical strength (2)
- mercaptocarboxylic acids (2)
- micro/mesoporous (2)
- microstructure (2)
- multishell (2)
- organic compounds adsorption (2)
- organic–inorganic hybrid (2)
- parchment (2)
- peptide biomarkers (2)
- phase separation (2)
- phase transfer (2)
- photocatalytic water splitting (2)
- polyamine (2)
- polyammonium salt (2)
- polycarboxylate (2)
- polyzwitterion (2)
- precipitation (2)
- protein carbonyls (2)
- protein modification (2)
- quantum dots (2)
- spent coffee (2)
- spent coffee grounds (2)
- surface chemistry (2)
- thermal properties (2)
- titania (2)
- valorization (2)
- water remediation (2)
- 3D (1)
- Ag/peptide@SiO(2) nanostructures (1)
- Amphiphilic polymers (1)
- Bacteria (1)
- Bio-inspired mineralization (1)
- Bioinspired (1)
- Biomimetics (1)
- Breakthrough time (1)
- Cation exchange Capacity (1)
- Cellulose (1)
- Clay-polymer nanocomposite - CPN (1)
- Click chemistry (1)
- Composite adsorbents (1)
- Composites (1)
- CuO (1)
- Defects (1)
- Desorption (1)
- Desorption kinetics (1)
- Dictyostelium discoideum (1)
- Energy (1)
- Fiber (1)
- Filtration (1)
- Gold nanoparticles (1)
- Grotthuss mechanism (1)
- Health (1)
- Heterogeneous catalysis (1)
- Hybrid clay (1)
- Hybrid material (1)
- Hydrogels (1)
- Hydrogen Production (1)
- Ionic Liquid (1)
- Ionic liquid (1)
- Ionogel (1)
- Iron (1)
- LED (1)
- Langmuir monolayers (1)
- Magnetic properties (1)
- Mesoporous materials (1)
- Microorganism (1)
- Micropollutants (1)
- N-acetyl cysteine (1)
- N-butylpyridinium bromide (1)
- Nanotechnology (1)
- Nanotoxicity (1)
- Nuclear magnetic resonance spectroscopy (1)
- Nucleophilic addition (1)
- Peptide coating (1)
- Phosphate recovery (1)
- Poly(ionic liquid) (1)
- Polyethylene imine (1)
- Polymers (1)
- Polymers on surfaces (1)
- Precipitation (1)
- Raman spectroscopy (1)
- Regeneration (1)
- SN(A)15 (1)
- Scattering (1)
- Sensors (1)
- Silver nanoparticles (1)
- Solid polymer electrolyte (1)
- Surface chemistry (1)
- Sustainable (1)
- TOF-SIMS (1)
- Triiodide "network" (1)
- Water (1)
- X-ray scattering (1)
- acidic ionic liquids (1)
- air-water-interface (1)
- aqueous-solution (1)
- bandgap (1)
- biocompatibility (1)
- block-copolymers (1)
- bone mimic (1)
- calcium (1)
- carbohydrates (1)
- carbonated apatite (1)
- catalysis (1)
- cation miscibility (1)
- cells (1)
- cesium cation (1)
- chiral nanoparticles (1)
- clusters (1)
- colloidal chemistry (1)
- colloidal quantum dots (1)
- confocal Raman microscopy (1)
- copper(II) halide salts (1)
- core-shell structures (1)
- cyano anchor group (1)
- dielectric polarisation (1)
- dielectric spectroscopy (1)
- disinfection (1)
- elastin-like recombinamers (1)
- electrolytes (1)
- electron-spin resonance (1)
- emulsion polymerization (1)
- energy materials (1)
- environmental remediation (1)
- extraction (1)
- ferroelectric thin films (1)
- food contact material (1)
- gas sensing (1)
- high pressure (1)
- hydrogen (1)
- imaging (1)
- incomplete surface passivation (1)
- indium (1)
- ion transport (1)
- life sciences (1)
- lipidomics (1)
- liquid crystal (1)
- liquid-crystal precursors (1)
- liquids (1)
- magnetic-properties (1)
- mesogen mesophases (1)
- mesoporous materials (1)
- metal (1)
- metal-containing ionic (1)
- metal-containing ionic liquids; (1)
- mineralization (1)
- mineralization beneath (1)
- molecular-structure (1)
- morphology (1)
- multidrug-resistant Escherichia coli (1)
- nano clay (1)
- nanocomposite material (1)
- nanofillers (1)
- nanomedicine (1)
- nanosilver (1)
- nanostructures (1)
- neurons (1)
- nucleation (1)
- organosilica (1)
- orthophosphates (1)
- paramagnetic-resonance (1)
- peptide-templated materials (1)
- perovskite solar cells (1)
- phagocytosis (1)
- phase transitions (1)
- phosphide (1)
- photocatalysts (1)
- photochemistry (1)
- poly(ethylene glycol) (1)
- polybutadiene (1)
- polycationic monolayer (1)
- polyelectrolytes (1)
- polymer (1)
- polymer brushes (1)
- polymer coating (1)
- polymer fillers (1)
- polymer films (1)
- polymer modification (1)
- pore templating (1)
- printing (1)
- proton conductivity (1)
- proton hopping (1)
- pyroelectricity (1)
- reactive oxygen species (1)
- ring-opening polymerization (1)
- rubidium cation (1)
- self-assembly (1)
- smart materials (1)
- sol-gel processes (1)
- solar (1)
- spin coating (1)
- square planar (1)
- sulfides (1)
- system (1)
- temperature phase (1)
- tetrabutylammonium hydroxide (1)
- tetrachlorocuprate(II) salts (1)
- tetrahalido metallates (1)
- tetrahalidometallates (1)
- thermomorphism (1)
- thiol passivation (1)
- three-dimensional depth profiling (1)
Self-assembly phenomena in block copolymer systems are attracting considerable interest from the scientific community and industry alike. Particularly interesting is the behavior of amphiphilic copolymers, which can self-organize into nanoscale-sized objects such as micelles, vesicles, or tubes in solution, and which form well-defined assemblies at interfaces such as air-liquid, air-solid, or liquid-solid. Depending on the polymer chemistry and architecture, various types of organization at interfaces can be expected, and further exploited for applications in nanotechnology, electronics, and biomedical sciences.
In this article, we discuss the formation and characterization of Langmuir monolayers from various amphiphilic block copolymers, including chargeable and thus pH-responsivematerials. Solid-supported polymer films are reviewed in the context of alteration of surface properties by ultrathin polymer layers and the possibilities for application in tissue engineering, sensors and biomaterials. Finally, we focus on how organic and polymer monolayers influence the growth of inorganic materials. This is a truly biomimetic approach since Nature uses soft interfaces to control the nucleation, growth, and morphology of biominerals such as calcium phosphate, calcium carbonate, and silica.
Covalently crosslinked PEI hydrogels are efficient templates for calcium phosphate mineralization in SBF. In contrast to the PEI hydrogels, non-crosslinked PEI does not lead to calcium phosphate nucleation and growth in SBF. The precipitate is a mixture of brushite and hydroxyapatite. The PEI/calcium phosphate composite material exhibits a sponge like morphology and a chemical composition that is interesting for implants. Cytotoxicity tests using Dictyostelium discoideum amoebae show that both the non-mineralized and mineralized hydrogels have a very low cytotoxicity. This suggests that next generation PEI hydrogels, where also the degradation products are non-toxic, could be interesting for biomedical applications.
Hydrogels with a hierarchical structure were prepared from a new highly water-soluble crosslinker N,N,N',N'-tetramethyl-N,N'-bis(2-ethylmethacrylate)-propyl-1,3-diammonium dibromide and from the sulfobetaine monomer 2-(N-3-sulfopropyl-N,N-dimethyl ammonium)ethyl methacrylate. The free radical polymerization of the two compounds is rapid and yields near-transparent hydrogels with sizes up to 5 cm in diameter. Rheology shows a clear correlation between the monomer-to-crosslinker ratio and the storage and loss moduli of the hydrogels. Cryo-scanning electron microscopy, low-field nuclear magnetic resonance (NMR) spectroscopy, and small-angle X-ray scattering show that the gels have a hierarchical structure with features spanning the nanometer to the sub-millimeter scale. The NMR study is challenged by the marked inhomogeneity of the gels and the complex chemical structure of the sulfobetaine monomer. NMR spectroscopy shows how these complications can be addressed via a novel fitting approach that considers the mobility gradient along the side chain of methacrylate-based monomers.
New cryogels for selective dye removal from aqueous solution were prepared by free radical polymerization from the highly water-soluble crosslinker N,N,N’,N’-tetramethyl-N,N’-bis(2-ethylmethacrylate)-propyl-1,3-diammonium dibromide and the sulfobetaine monomer 2-(N-3-sulfopropyl-N,N-dimethyl ammonium)ethyl methacrylate. The resulting white and opaque cryogels have micrometer sized pores with a smaller substructure. They adsorb methyl orange (MO) but not methylene blue (MB) from aqueous solution. Mixtures of MO and MB can be separated through selective adsorption of the MO to the cryogels while the MB remains in solution. The resulting cryogels are thus candidates for the removal of hazardous organic substances, as exemplified by MO and MB, from water. Clearly, it is possible that the cryogels are also potentially interesting for removal of other compounds such as pharmaceuticals or pesticides, but this must be investigated further.
New cryogels for selective dye removal from aqueous solution were prepared by free radical polymerization from the highly water-soluble crosslinker N,N,N’,N’-tetramethyl-N,N’-bis(2-ethylmethacrylate)-propyl-1,3-diammonium dibromide and the sulfobetaine monomer 2-(N-3-sulfopropyl-N,N-dimethyl ammonium)ethyl methacrylate. The resulting white and opaque cryogels have micrometer sized pores with a smaller substructure. They adsorb methyl orange (MO) but not methylene blue (MB) from aqueous solution. Mixtures of MO and MB can be separated through selective adsorption of the MO to the cryogels while the MB remains in solution. The resulting cryogels are thus candidates for the removal of hazardous organic substances, as exemplified by MO and MB, from water. Clearly, it is possible that the cryogels are also potentially interesting for removal of other compounds such as pharmaceuticals or pesticides, but this must be investigated further.
By using synchrotron X-ray powder diffraction, the temperature dependent phase diagram of the hybrid perovskite tri-halide compounds, methyl ammonium lead iodide (MAPbI3, MA+ = CH3NH3+) and methyl ammonium lead bromide (MAPbBr3), as well as of their solid solutions, has been established. The existence of a large miscibility gap between 0.29 ≤ x ≤ 0.92 (±0.02) for the MAPb(I1−xBrx)3 solid solution has been proven. A systematic study of the lattice parameters for the solid solution series at room temperature revealed distinct deviations from Vegard's law. Furthermore, temperature dependent measurements showed that a strong temperature dependency of lattice parameters from the composition is present for iodine rich compositions. In contrast, the bromine rich compositions show an unusually low dependency of the phase transition temperature from the degree of substitution.
Organic or inorganic (A) metal (M) halide (X) perovskites (AMX(3)) are semiconductor materials setting the basis for the development of highly efficient, low-cost and multijunction solar energy conversion devices. The best efficiencies nowadays are obtained with mixed compositions containing methylammonium, formamidinium, Cs and Rb as well as iodine, bromine and chlorine as anions. The understanding of fundamental properties such as crystal structure and its effect on the band gap, as well as their phase stability is essential. In this systematic study X-ray diffraction and photoluminescense spectroscopy were applied to evaluate structural and optoelectronic properties of hybrid perovskites with mixed compositions.
Silver nanoparticles (SNPs) are among the most commercialized nanoparticles because of their antibacterial effects. Besides being employed, e. g. as a coatingmaterial for sterile surfaces in household articles and appliances, the particles are also used in a broad range of medical applications. Their antibacterial properties make SNPs especially useful for wound disinfection or as a coating material for prostheses and surgical instruments. Because of their optical characteristics, the particles are of increasing interest in biodetection as well. Despite the widespread use of SNPs, there is little knowledge of their toxicity. Time-of-flight secondary ion mass spectrometry (ToF-SIMS) and laser post-ionization secondary neutral mass spectrometry (Laser-SNMS) were used to investigate the effects of SNPs on human macrophages derived from THP-1 cells in vitro. For this purpose, macrophages were exposed to SNPs. The SNP concentration ranges were chosen with regard to functional impairments of the macrophages. To optimize the analysis of the macrophages, a special silicon wafer sandwich preparation technique was employed; ToF-SIMS was employed to characterize fragments originating from macrophage cell membranes. With the use of this optimized sample preparation method, the SNP-exposed macrophages were analyzed with ToF-SIMS and with Laser-SNMS. With Laser-SNMS, the three-dimensional distribution of SNPs in cells could be readily detected with very high efficiency, sensitivity, and submicron lateral resolution. We found an accumulation of SNPs directly beneath the cell membrane in a nanoparticular state as well as agglomerations of SNPs inside the cells.
Calcium phosphate nanofibers with a diameter of only a few nanometers and a cotton-ball-like aggregate morphology have been reported several times in the literature. Although fiber formation seems reproducible in a variety of conditions, the crystal structure and chemical composition of the fibers have been elusive. Using scanning transmission electron microscopy, low dose electron (nano)diffraction, energy-dispersive X-ray spectroscopy, and energy- filtered transmission electron microscopy, we have assigned crystal structures and chemical compositions to the fibers. Moreover, we demonstrate that the mineralization process yields true polymer/calcium phosphate hybrid materials where the block copolymer template is closely associated with the calcium phosphate.
The lack of anionic carboxylate ligands on the surface of InP/ZnSe/ZnS quantum dots (QDs), where zinc carboxylate ligands can be converted to carboxylic acid or carboxylate ligands via proton transfer by 1-octanethiol, is demonstrated. The as-synthesized QDs initially have an under-coordinated vacancy surface, which is passivated by solvent ligands such as ethanol and acetone. Upon exposure of 1-octanethiol to the QD surface, 1-octanethiol effectively induces the surface binding of anionic carboxylate ligands (derived from zinc carboxylate ligands) by proton transfer, which consequently exchanges ethanol and acetone ligands that bind on the incomplete QD surface. These systematic chemical analyses, such as thermogravimetric analysis-mass spectrometry and proton nuclear magnetic resonance spectroscopy, directly show the interplay of surface ligands, and it associates with QD light-emitting diodes (QD-LEDs). It is believed that this better understanding can lead to industrially feasible QD-LEDs.
SpiderMAEn
(2019)
A growing energy demand requires new and preferably renewable energy sources. The infinite availability of solar radiation makes its conversion into storable and transportable energy forms attractive for research as well as for the industry. One promising example of a transportable fuel is hydrogen (H-2), making research into eco-friendly hydrogen production meaningful. Here, a hybrid system was developed using newly designed recombinant spider silk protein variants as a template for mineralization with inorganic titanium dioxide and gold. These bioinspired organic/inorganic hybrid materials allow for hydrogen production upon light irradiation. To begin with, recombinant spider silk proteins bearing titanium dioxide and gold-binding moieties were created and processed into structured films. These films were modified with gold and titanium dioxide in order to produce a photocatalyst. Subsequent testing revealed hydrogen production as a result of light-induced hydrolysis of water. Therefore, the novel setup presented here provides access to a new principle of generating advanced hybrid materials for sustainable hydrogen production and depicts a promising platform for further studies on photocatalytic production of hydrogen, the most promising future fuel.
The phase behavior of an amphiphilic block copolymer based on a poly(aspartic acid) hydrophilic block and a poly(n-butyl acrylate) hydrophobic block was investigated at the air–water and air–buffer interface. The polymer forms stable monomolecular films on both subphases. At low pH, the isotherms exhibit a plateau. Compression–expansion experiments and infrared reflection absorption spectroscopy suggest that the plateau is likely due to the formation of polymer bi- or multilayers. At high pH the films remain intact upon compression and no multilayer formation is observed. Furthermore, the mineralization of calcium phosphate beneath the monolayer was studied at different pH. The pH of the subphase and thus the polymer charge strongly affects the phase behavior of the film and the mineral formation. After 4 h of mineralization at low pH, atomic force microscopy shows smooth mineral films with a low roughness. With increasing pH the mineral films become inhomogeneous and the roughness increases. Transmission electron microscopy confirms this: at low pH a few small but uniform particles form whereas particles grown at higher pH are larger and highly agglomerated. Energy-dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy confirm the formation of calcium phosphate. The levels of mineralization are higher in samples grown at high pH.
Fully renewable pyridinium ionic liquids were synthesised via the hydrothermal decarboxylation of pyridinium zwitterions derived from furfural and amino acids in flow. The functionality of the resulting ionic liquid (IL) can be tuned by choice of different amino acids as well as different natural carboxylic acids as the counterions. A representative member of this new class of ionic liquids was successfully used for the synthesis of ionogels and as a solvent for the Heck coupling.
Mesoporous silica monoliths were prepared by the sol - gel technique and. lled with 1-ethyl-3-methyl imidazolium [Emim]-X (X = dicyanamide [N(CN)(2)], ethyl sulfate [EtSO4], thiocyanate [SCN], and triflate [TfO]) ionic liquids (ILs) using a methanol-IL exchange technique. The structure and behavior of the ILs inside the silica monoliths were studied using X-ray scattering, nitrogen sorption, IR spectroscopy, solid-state NMR, and thermal analysis. DSC finds shifts in both the glass transition temperature and melting points (where applicable) of the ILs. Glass transition and melting occur well below room temperature. There is thus no conflict with the NMR and IR data, which show that the ILs are as mobile at room temperature as the bulk (not confined) ILs. The very narrow line widths of the NMR spectra suggest that the ILs in our materials have the highest mobility reported for confined ILs so far. As a result, our data suggest that it is possible to generate IL/silica hybrid materials (ionogels) with bulk-like properties of the IL. This could be interesting for applications in, e.g., the solar cell or membrane fields.
Silica is an important mineral in biology and technology, and many protocols have been developed for the synthesis of complex silica architectures. The current report shows that silsesquioxane nanoparticles carrying polymer arms on their surface are efficient templates for the fabrication of silica particles with a star- or raspberry-like morphology. The shape of the resulting particles depends on the chemistry of the polymer arms. With poly(N,N- dimethylaminoethyl methacrylate) (PDMAEMA) arms, spherical particles with a less electron dense core form. With poly {[2- (methacryloyloxy)ethyl] trimethylammonium iodide} (PMETAI), star- or raspberry-like particles form. Electron microscopy, electron tomography, and small-angle X-ray scattering show that the resulting silica particles have a complex structure, where a silsequioxane nanoparticle carrying the polymer arms is in the center. Next is a region that is polymer-rich. The outermost region of the particle is a silica layer, where the outer parts of the polymer arms are embedded. Time- resolved zeta-potential and pH measurements, dynamic light scattering, and electron microscopy reveal that silica formation proceeds differently if PDMAEMA is exchanged for PMETAI.
Simple tripeptides are scaffolds for the synthesis and further assembly of peptide/silver nanoparticle composites. Herein, we further explore peptide-con trolled silver nanoparticle assembly processes. Silver nanoparticles with a pH-responsive peptide coating have been synthesized by using a one-step precipitation/coating route. The nature of the peptide/silver interaction and the effect of the peptide oil the formation of the silver particles have been studied via UV/Vis, X-ray photoelectron, and surface-enhanced Raman spectroscopies as well as through electron microscopy, small angle X-ray scattering and powder Xray diffraction with Rietveld refinement. The particles reversibly form aggregates of different sizes in aqueous solution. The state of aggregation call be controlled by the solution pH value. At low pH values, individual particles are present. At neutral pH values, small clusters form and at high pH values, large precipitates are observed.
Amphiphilic alkyl-poly(ethyleneimine)s (alkyl-PEI) with different degrees of polymerization have been produced by alkaline hydrolysis of alkyl-poly(2-methyl-2-oxazoline). Potentiometric titration of the alkyl-PEI shows the influence of the alkyl chain and the degree of polymerization on the titration curves and hence on the polymer conformation. Karl Fischer titration has been used to determine the water content in the polymers. Subsequent X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and differential scanning calorimetry (DSC) measurements prove the existence of different hydration states of the PEI even under dry storage conditions. Upon cooling from hot aqueous Solutions, hydrogels form. The gelation concentration decreases with increasing degree of polymerization of the PEI segment. Scanning electron microscopy (SEM and cryo-SEM) of the hydrogels reveal an alkyl-PEI fibrous network composed of fan-like units. DSC shows that the percentages of bound and free water in the hydrogels depend on the concentration of polar amino groups.
The report shows that simple LbL deposition of positively charged chitosan and negatively charged heparin can be used to efficiently modify the native surface of both NiTi and Ti without any previous treatments. Moreover, mineralization of the polymer multilayers with calcium phosphate leads to surfaces with low contact angles around 70 and 20 degrees for NiTi and Ti, respectively. This suggests that a polymer multilayer/calcium phosphate hybrid coating could be useful for making NiTi or Ti implants that are at the same time antibacterial (via the chitosan), suppress blood clot formation (via the heparin), and favor fast endothelialization (via the improved surface hydrophilicity compared to the respective neat material).
Klassischerweise haben Salze, beispielsweise Kochsalz, Schmelzpunkte von einigen hundert Grad Celsius und mehr. Ionische Flüssigkeiten sind dagegen Salze, deren Schmelzpunkt zum Teil weit unter der Raumtemperatur liegt. Sie sind daher bei Raumtemperatur flüssig. Obwohl ionische Flüssigkeiten seit 1914 bekannt sind, hatten sie bis vor 15 Jahren keinerlei Bedeutung. Heute jedoch werden ionische Flüssigkeiten aufgrund ihrer vorteilhaften Eigenschaften, wie hohe Leitfähigkeit oder hohe Temperaturstabilität, unter anderem zur Papierverarbeitung oder in flexiblen Solarzellen eingesetzt. Die Antrittsvorlesung wird sich insbesondere mit der Herstellung anorganischer Partikel befassen und zeigen, wie ionische Flüssigkeiten zur Herstellung neuer Materialien für verschiedene Anwendungen genutzt werden können.
The polymer-controlled and bioinspired precipitation of inorganic minerals from aqueous solution at near-ambient or physiological conditions avoiding high temperatures or organic solvents is a key research area in materials science. Polymer-controlled mineralization has been studied as a model for biomineralization and for the synthesis of (bioinspired and biocompatible) hybrid materials for a virtually unlimited number of applications. Calcium phosphate mineralization is of particular interest for bone and dental repair. Numerous studies have therefore addressed the mineralization of calcium phosphate using a wide variety of low- and high-molecular-weight additives. In spite of the growing interest and increasing number of experimental and theoretical data, the mechanisms of polymer-controlled calcium phosphate mineralization are not entirely clear to date, although the field has made significant progress in the last years. A set of elegant experiments and calculations has shed light on some details of mineral formation, but it is currently not possible to preprogram a mineralization reaction to yield a desired product for a specific application. The current article therefore summarizes and discusses the influence of (macro)molecular entities such as polymers, peptides, proteins and gels on biomimetic calcium phosphate mineralization from aqueous solution. It focuses on strategies to tune the kinetics, morphologies, final dimensions and crystal phases of calcium phosphate, as well as on mechanistic considerations.
Calcium phosphate mineralization from aqueous solution in the presence of organic growth modifiers has been intensely studied in the recent past. This is mostly due to potential applications of the resulting composites in the biomaterials field. Polymers in particular are efficient growth modifiers. As a result, there has been a large amount of work on polymeric growth modifiers. Interestingly, however, relatively little work has been done on polycationic additives. The current paper shows that poly(ethylene oxide)b-poly(L-lysine) block copolymers lead to an interesting morphology of calcium phosphate precipitated at room temperature and subjected to a mild heat treatment at 85 degrees C. Electron microscopy, synchrotron X-ray diffraction, and porosity analysis show that a (somewhat) porous material with channel-like features forms. Closer inspection using transmission electron microscopy shows that the channels are probably not real channels. Much rather the morphology is the result of the aggregation of ca. 100-nm-sized rodlike primary particles, which changes upon drying to exhibit the observed channel-like features. Comparison experiments conducted in the absence of polymer and with poly(ethylene oxide)-b-poly(L-glutamate) show that these features only form in the presence of the polycationic poly(L-lysine) block, suggesting a distinct interaction of the polycation with either the crystal or the phosphate ions prior to mineralization.
Ionogel fiber mats were made by electrospinning poly(methylmethacrylate) (PMMA) and the ionic liquid (IL) bis(1-butyl-3-methyl-imidazolium) tetrachloridocupraten, [Bmim](2)[CuCl4], from acetone. The morphology of the electrospun ionogels strongly depends on the spinning parameters. Dense and uniform fiber mats were only obtained at concentrations of 60 to 70 g of polymer and IL mass combined. Lower concentrations led to a low number of poorly defined fibers. High voltages of 20 to 25 kV led to well-defined and uniform fibers; voltages between 15 and 20 kV again led to less uniform and less dense fibers. At 10 kV and lower, no spinning could be induced. Finally, PMMA fibers electrospun without IL show a less well-defined morphology combining fibers and oblong droplets indicating that the IL has a beneficial effect on the electrospinning process. The resulting materials are prototypes for new functional materials, for example in sterile filtration.
We report on attempts towards the synthesis of titanium nanoparticles using a wet chemical approach in imidazolium-based ionic liquids (ILs) under reducing conditions. Transmission electron microscopy finds nanoparticles in all cases. UV/Vis spectroscopy confirms the nanoparticulate nature of the precipitate, as in all cases an absorption band between ca. 280 and 300 nm is visible. IR spectroscopy shows that even after extensive washing and drying, some IL remains adsorbed on the nanoparticles. Raman spectroscopy suggests the formation of anatase nanoparticles, but X-ray diffraction reveals that, possibly, amorphous titania forms or that the nanoparticles are so small that a clear structure assignment is not possible. The report thus shows that (possibly amorphous) titanium oxides even form under reducing conditions and that the chemical synthesis of titanium nanoparticles in ILs remains elusive.
In the body, nanoparticles can be systemically distributed and then may affect secondary target organs, such as the central nervous system (CNS). Putative adverse effects on the CNS are rarely investigated to date. Here, we used a mixed primary cell model consisting mainly of neurons and astrocytes and a minor proportion of oligodendrocytes to analyze the effects of well-characterized 20 and 40 nm silver nanoparticles (SNP). Similar gold nanoparticles served as control and proved inert for all endpoints tested. SNP induced a strong size-dependent cytotoxicity. Additionally, in the low concentration range (up to 10 mu g/ml of SNP), the further differentiated cultures were more sensitive to SNP treatment. For detailed studies, we used low/medium dose concentrations (up to 20 mu g/ml) and found strong oxidative stress responses. Reactive oxygen species (ROS) were detected along with the formation of protein carbonyls and the induction of heme oxygenase-1. We observed an acute calcium response, which clearly preceded oxidative stress responses. ROS formation was reduced by antioxidants, whereas the calcium response could not be alleviated by antioxidants. Finally, we looked into the responses of neurons and astrocytes separately. Astrocytes were much more vulnerable to SNP treatment compared with neurons. Consistently, SNP were mainly taken up by astrocytes and not by neurons. Immunofluorescence studies of mixed cell cultures indicated stronger effects on astrocyte morphology. Altogether, we can demonstrate strong effects of SNP associated with calcium dysregulation and ROS formation in primary neural cells, which were detectable already at moderate dosages.
Silver nanoparticles (SNPs) are among the most commercialized nanoparticles worldwide. Often SNP are used because of their antibacterial properties. Besides that they possess unique optic and catalytic features, making them highly interesting for the creation of novel and advanced functional materials. Despite its widespread use only little data exist in terms of possible adverse effects of SNP on human health. Conventional synthesis routes usually yield products of varying quality and property. It thus may become puzzling to compare biological data from different studies due to the great variety in sizes, coatings or shapes of the particles applied. Here, we applied a novel synthesis approach to obtain SNP of well-defined colloidal and structural properties. Being stabilized by a covalently linked small peptide, these particles are nicely homogenous, with narrow size distribution, and form monodisperse suspensions in aqueous solutions. We applied these peptide-coated SNP in two different sizes of 20 or 40 nm (Ag20Pep and Ag40Pep) and analyzed responses of THP-1-derived human macrophages while being exposed against these particles. Gold nanoparticles of similar size and coating (Au20Pep) were used for comparison. The cytotoxicity of particles was assessed by WST-1 and LDH assays, and the uptake into the cells was confirmed via transmission electron microscopy. In summary, our data demonstrate that this novel type of SNP is well suited to serve as model system for nanoparticles to be tested in toxicological studies in vitro.
Silver nanoparticles (SNP) are among the most commercialized nanoparticles. Here, we show that peptide-coated SNP cause functional impairment of human macrophages. A dose-dependent inhibition of phagocytosis is observed after nanoparticle treatment, and pretreatment of cells with N-acetyl cysteine (NAC) can counteract the phagocytosis disturbances caused by SNP.
Using the surface-sensitive mode of time-of-flight secondary ion mass spectrometry, in combination with multivariate statistical methods, we studied the composition of cell membranes in human macrophages upon exposure to SNP with and without NAC preconditioning. This method revealed characteristic changes in the lipid pattern of the cellular membrane outer leaflet in those cells challenged by SNP. Statistical analyses resulted in 19 characteristic ions, which can be used to distinguish between NAC pretreated and untreated macrophages. The present study discusses the assignments of surface cell membrane phospholipids for the identified ions and the resulting changes in the phospholipid pattern of treated cells. We conclude that the adverse effects in human macrophages caused by SNP can be partially reversed through NAC administration. Some alterations, however, remained.
The self-assembly of double-hydrophilic poly(ethylene oxide)-poly(2-methyl-2-oxazoline) diblock copolymers in water has been studied. Isothermal titration calorimetry, small-angle X-ray scattering, and analytical ultracentrifugation suggest that only single polymer chains are present in solution. In contrast, light scattering and transmission electron microscopy detect aggregates with radii of ca. 100 nm. Pulsed field gradient NMR spectroscopy confirms the presence of aggregates, although only 2% of the polymer chains undergo aggregation. Water uptake experiments indicate differences in the hydrophilicity of the two blocks, which is believed to be the origin of the unexpected aggregation behavior (in accordance with an earlier study by Ke et al. [Macromolecules 2009, 42, 5339-5344]). The data therefore suggest that even in double-hydrophilic block copolymers, differences in hydrophilicity are sufficient to drive polymer aggregation, a phenomenon that has largely been overlooked or ignored so far.
Magnetic ionogels (MagIGs) were prepared from organosilane-coated iron oxide nanoparticles, N-isopropylacrylamide, and the ionic liquid trihexyl(tetradecyl)phosphonium dicyanamide. The ionogels prepared with the silane-modified nanoparticles are more homogeneous than ionogels prepared with unmodified magnetite particles. The silane-modified particles are immobilized in the ionogel and are resistant tonanoparticle leaching. The modified particles also render the ionogels mechanically more stable than the ionogels synthesized with unmodified nanoparticles. The ionogels respond to external permanent magnets and are therefore prototypes of a new soft magnetic actuator.
Calcium phosphate nanofibers with a diameter of only a few nanometers and a cotton-ball-like aggregate morphology have been reported several times in the literature. Although fiber formation seems reproducible in a variety of conditions, the crystal structure and chemical composition of the fibers have been elusive. Using scanning transmission electron microscopy, low dose electron (nano) diffraction, energy-dispersive X-ray spectroscopy, and energy-filtered transmission electron microscopy, we have assigned crystal structures and chemical compositions to the fibers. Moreover, we demonstrate that the mineralization process yields true polymer/calcium phosphate hybrid materials where the block copolymer template is closely associated with the calcium phosphate.
Transparent, ion-conducting, luminescent, and flexible ionogels based on the room temperature ionic liquid (IL) 1-butyl-3-methylimidazolium bis(trifluoromethane sulfonyl) imide [Bmim][N(Tf)(2)], a PtEu2 chromophore, and poly(methylmethacrylate) (PMMA) have been prepared. The thermal stability of the PMMA significantly increases with IL incorporation. In particular, the onset weight loss observed at ca. 229 degrees C for pure PMMA increases to 305 degrees C with IL addition. The ionogel has a high ionic conductivity of 10(-3) S cm(-1) at 373 K and exhibits a strong emission in the red with a long average luminescence decay time of tau = 890 mu s. The resulting material is a new type of soft hybrid material featuring useful thermal, optical, and ion transport properties.
New hybrid materials have been prepared by grafting synthetic peptides in the interlayer spacing of Cu(II) and Co(II) layered simple hydroxides (LSHs). The interlayer spacing of the hybrids depends on the peptide chain length; the dependence is specific for the copper and cobalt-based hybrids. This suggests a metal-or LSH-specific interaction of the peptides with the respective inorganic layers. When tyrosine is present in the peptide, its fluorescence is quenched after grafting the peptide to the LSH. Studies of the luminescence vs. pH indicate deprotonation of the tyrosine moieties to tyrosinate at high pH, accompanied by the onset of luminescence. The luminescence increases with increasing OH- concentration, suggesting an application of the hybrids as chemical sensors. Moreover, the peptides influence the magnetic properties of the hybrids. The copper-based hybrids behave antiferromagnetically and the cobalt-based hybrids are ferrimagnets.
A number of ionogels - silica-ionic liquid (IL) hybrid materials - were synthesized and studied for their ionic conductivity. The materials are based on a sulfonated IL, 1-methyl-3-(3-sulfopropyl-)-imidazolium p-toluenesulfonate, [PmimSO(3)H][PTS], which contains a sulfonic acid/sulfonate group both in the IL anion and in the side chain of the IL cation. By way of the sulfonate-sulfonic acid proton transfer, the IL imparts the ionogel with a high ionic conductivity of ca. 10(-2) S cm(-1) in the as-synthesized state at 120 degrees C and 10(-3) S cm(-1) in the dry state at 120 degrees C. The ionogels are stable up to ca. 150 degrees C in dynamic thermogravimetric analysis. This suggests that these materials, which are relatively cheap and easily fabricated, could find application in fuel cells in intermediate temperature ranges where many other membrane materials are not suitable.
Carbon-based ionogels tuning the properties of the ionic liquid via carbon-ionic liquid interaction
(2012)
The behavior of two ionic liquids (ILs), 1-ethyl-3-methylimidazolium dicyanamide [Emim][DCA] and 1-ethyl-3-methylimidazolium triflate [Emim][TfO], in (meso) porous carbonaceous hosts was investigated. Prior to IL incorporation into the host, the carbon matrix was thermally annealed between 180 and 900 degrees C to control carbon condensation and surface chemistry. The resulting materials have an increasing "graphitic'' carbon character with increasing treatment temperature, reflected in a modified behavior of the ILs when impregnated into the carbon host. The two ILs show significant changes in the thermal behavior as measured from differential scanning calorimetry; these changes can be assigned to anion-pi interaction between the IL anions and the pore wall surfaces of these flexible carbonaceous support materials.
Mesoporous, highly structured silicon carbide (beta-SiC) was synthesised from renewable plant materials (two Equisetaceae species) in a one-step carbothermal process at remarkably low temperatures down to 1200 degrees C. The SiC precursor is a silicon-carbon mixture with finely dispersed carbon prepared by pyrolysis of the organic plant matrix. Yields are 3 to 100% (omega(Si/Si) related to the silicon deposited in the plant material), depending on reaction temperature and time. IR spectroscopy, X-ray diffraction, and nitrogen sorption prove the formation of high-purity beta-SiC with minor inorganic impurities after purification and a high specific surface area of up to 660 m(2) g(-1). Scanning electron microscopy shows that the plant morphology is maintained in the final SiC. Sedimentation analysis finds a mean particle size (diameters d(50)) of 20 mu m.
Commercially available 1,2-PB was transformed into a well-defined reactive intermediate by quantitative bromination. The brominated polymer was used as a polyfunctional macroinitiator for the cationic ring-opening polymerization of 2-ethyl-2-oxazoline to yield a water-soluble brush polymer. Nucleophilic substitution of bromide by 1-methyl imidazole resulted in the formation of polyelectrolyte copolymers consisting of mixed units of imidazolium, bromo, and double bond. These copolymers, which were soluble in water without forming aggregates, were used as stabilizers in the heterophase polymerization of styrene and were also studied for their ionic conducting properties.
Silver nanoparticles (SNP) are the subject of worldwide commercialization because of their antimicrobial effects. Yet only little data on their mode of action exist. Further, only few techniques allow for visualization and quantification of unlabeled nanoparticles inside cells. To study SNP of different sizes and coatings within human macrophages, we introduce a novel laser postionization secondary neutral mass spectrometry (Laser-SNMS) approach and prove this method superior to the widely applied confocal Raman and transmission electron microscopy. With time-of-flight secondary ion mass spectrometry (TOF-SIMS) we further demonstrate characteristic fingerprints in the lipid pattern of the cellular membrane indicative of oxidative stress and membrane fluidity changes. Increases of protein carbonyl and heme oxygenase-1 levels in treated cells confirm the presence of oxidative stress biochemically. Intriguingly, affected phagocytosis reveals as highly sensitive end point of SNP-mediated adversity In macrophages. The cellular responses monitored are. hierarchically linked, but follow individual kinetics and are partially reversible.
Biomimetic hybrid materials based on a polymeric and an inorganic component such as calcium phosphate are potentially useful for bone repair. The current study reports on a new approach toward biomimetic hybrid materials using a set of recombinamers (recombinant protein materials obtained from a synthetic gene) as crystallization additive for calcium phosphate. The recombinamers contain elements from elastin, an elastic structural protein, and statherin, a salivary protein. Via genetic engineering, the basic elastin sequence was modified with the SN(A)15 domain of statherin, whose interaction with calcium phosphate is well-established. These new materials retain the biocompatibility, "smart" nature, and desired mechanical behavior of the elastin-like recombinamer (ELR) family. Mineralization in simulated body fluid (SBF) in the presence of these recombinamers reveals surprising differences. Two of the polymers inhibit calcium phosphate deposition (although they contain the statherin segment). In contrast, the third polymer, which has a triblock structure, efficiently controls the calcium phosphate formation, yielding spherical hydroxyapatite (HAP) nanoparticles with diameters from 1 to 3 nm after 1 week in SBF at 37 degrees C. However, at lower temperatures, no precipitation is observed with any of the polymers. The data thus suggest that the molecular design of ELRs containing statherin segments and the selection of an appropriate polymer structure are key parameters to obtain functional materials for the development of intelligent systems for hard tissue engineering and subsequent in vivo applications.
Tetrahalidocuprates(II) show a high degree of structural flexibility. We present the results of crystallographic and electron paramagnetic resonance (EPR) spectroscopic analyses of four new tetrabromidocuprate(II) compounds and compare the results with previously reported data. The cations in the new compounds are the sterically demanding benzyltriphenylphosphonium, methyltriphenylphosphonium, tetraphenylphosphonium, and hexadecyltrimethylammonium ions; they were used to achieve a reasonable separation of the paramagnetic Cu(II) ions for EPR spectroscopy. X-Ray crystallography shows that in all four complexes the [CuBr4](2-) units have a distorted tetrahedral coordination geometry which is in agreement with DFT calculations. The EPR hyperfine structure was not resolved. This is due to the exchange broadening resulting from still incomplete separation of the paramagnetic Cu(II) centres. Nevertheless, the principal values of the electron Zeemann tensor (g(parallel to) and g(perpendicular to)) of the complexes could be determined. A correlation of structural (X-ray) parameters with the spin density at the copper centres (DFT) is well reflected in the EPR spectra of the bromidocuprates. This enables the correlation of X-ray and EPR parameters to predict the structure of tetrabromidocuprates in physical states other than the crystalline state. As a result, we provide a method to structurally characterize [CuBr4](2-) in, for example, ionic liquids or in solution, which has important implications for e.g. catalysis or materials science.
Silica and silver nanoparticles are relevant materials for new applications in optics, medicine, and analytical chemistry. We have previously reported the synthesis of pH responsive, peptide-templated, chiral silver nanoparticles. The current report shows that peptide-stabilized nanoparticles can easily be coated with a silica shell by exploiting the ability of the peptide coating to hydrolyze silica precursors such as TEOS or TMOS. The resulting silica layer protects the nanoparticles from chemical etching, allows their inclusion in other materials, and renders them biocompatible. Using electron and atomic force microscopy, we show that the silica shell thickness and the particle aggregation can be controlled simply by the reaction time. Small-angle X ray scattering confirms the Ag/peptide@silica core-shell structure. UV-vis and circular dichroism spectroscopy prove the conservation of the silver nanoparticle chirality upon silicification. Biological tests show that the biocompatibility in simple bacterial systems is significantly improved once a silica layer is deposited on the silver particles.
The iron-containing ionic liquids 1-butyl-3-methylimidazolium tetrachloroferrate(III) [C(4)mim][FeCl4] and 1-dodecyl-3-methylimidazolium tetrachloroferrate(III) [C(12)mim][FeCl4] exhibit a thermally induced demixing with water (thermomorphism). The phase separation temperature varies with IL weight fraction in water and can be tuned between 100 degrees C and room temperature. The reversible lower critical solution temperature (LCST) is only observed at IL weight fractions below ca. 35% in water. UV/Vis, IR, and Raman spectroscopy along with elemental analysis prove that the yellow-brown liquid phase recovered after phase separation is the starting IL [C(4)mim][FeCl4] and [C(12)mim][FeCl4], respectively. Photometry and ICP-OES show that about 40% of iron remains in the water phase upon phase separation. Although the process is thus not very efficient at the moment, the current approach is the first example of an LCST behavior of a metal-containing IL and therefore, although still inefficient, a prototype for catalyst removal or metal extraction.
The synthesis of Co-NPs and Mn-NPs by microwave-induced decomposition of the metal carbonyls Co-2(CO)(8) and Mn-2(CO)(10), respectively, yields smaller and better separated particles in the functionalized IL 1-methyl-3-(3-carboxyethyl)-imidazolium tetrafluoroborate [EmimCO(2)H][BF4] (1.6 +/- 0.3 nm and 4.3 +/- 1.0 nm, respectively) than in the non-functionalized IL 1-n-butyl-3-methylimidazolium tetrafluoroborate [Bmim][BF4]. The particles are stable in the absence of capping ligands (surfactants) for more than six months although some variation in particle size could be observed by TEM.
Biomimetic synthesis of chiral erbium-doped silver/peptide/silica core-shell nanoparticles (ESPN)
(2011)
Peptide-modified silver nanoparticles have been coated with an erbium-doped silica layer using a method inspired by silica biomineralization. Electron microscopy and small-angle X-ray scattering confirm the presence of an Ag/peptide core and silica shell. The erbium is present as small Er(2)O(3) particles in and on the silica shell. Raman, IR, UV-Vis, and circular dichroism spectroscopies show that the peptide is still present after shell formation and the nanoparticles conserve a chiral plasmon resonance. Magnetic measurements find a paramagnetic behavior. In vitro tests using a macrophage cell line model show that the resulting multicomponent nanoparticles have a low toxicity for macrophages, even on partial dissolution of the silica shell.
We report on the ionothermal synthesis of porous carbon materials from a variety of carbohydrate precursors (i.e. D-glucose, D-fructose, D-xylose, and starch) using 1-butyl-3-methylimidazolium tetrachloroferrate(III), [Bmim][FeCl(4)] as a reusable solvent and catalyst. The carbon materials derived from these different carbohydrates are similar in terms of particle size and chemical composition, possessing relatively high surface areas from 44 to 155 m(2) g(-1) after ionothermal processing, which can be significantly increased to > 350 m(2) g(-1) by further thermal treatment (e. g. post-carbonization at 750 degrees C). CO(2) and N(2) sorption analysis, combined with Hg intrusion porosimetry, reveals a promising hierarchical pore structuring to these carbon materials. The ionic liquid [Bmim][FeCl(4)] has a triple role: it acts as both a soft template to generate the characterized pore structuring, solvent and as a catalyst resulting in enhanced ionothermal carbon yields. Importantly from a process point of view, the ionic liquid can be successfully recovered and reused. The current work shows that ionothermal synthesis has the potential to be an effective, low cost, and green reusable synthetic route towards sustainable porous carbon materials.
The large-scale green synthesis of graphene-type two-dimensional materials is still challenging. Herein, we describe the ionothermal synthesis of carbon-based composites from fructose in the iron-containing ionic liquid 1-butyl-3-methylimidazolium tetrachloridoferrate(III), [Bmim][FeCl4] serving as solvent, catalyst, and template for product formation. The resulting composites consist of oligo-layer graphite nanoflakes and iron carbide particles. The mesoporosity, strong magnetic moment, and high specific surface area of the composites make them attractive for water purification with facile magnetic separation. Moreover, Fe3Cfree graphite can be obtained via acid etching, providing access to fairly large amounts of graphite material. The current approach is versatile and scalable, and thus opens the door to ionothermal synthesis towards the larger-scale synthesis of materials that are, although not made via a sustainable process, useful for water treatment such as the removal of organic molecules.
Transparent, ion-conducting, and flexible ionogels based on the room temperature ionic liquid (IL) 1-butyl-3-methylimidazolium bis(trifluoromethane sulfonyl) imide [Bmim][N(Tf)(2)], the dye-IL (DIL) 1-butyl-3-methylimidazolium methyl orange [Bmim][MO], and poly(methylmethacrylate) (PMMA) are prepared. Upon IL incorporation the thermal stability of the PMMA matrix significantly increases from 220 to 280 degrees C. The ionogels have a relatively high ionic conductivity of 10(-4) S cm(-1) at 373 K. Most importantly, the ionogels exhibit a strong and reversible color change when exposed to aqueous or organic solutions containing protons or hydroxide ions. The resulting material is thus a prototype of soft multifunctional matter featuring ionic conductivity, easy processability, response to changes in the environment, and a strong readout signal, the color change, that could be used in optical data storage or environmental sensing.
Ionic liquid Crystals constitute highly versatile materials that have drawn much interest these past few years in the fields of academic research and industrial development. In this respect, the present article is intended as an update of K. Binnemans review published in 2005, but focusing exclusively on the imidazolium cation - the most widely studied. Herein, imidazolium-containing thermotropic liquid crystalline materials will be sorted by molecular structure (mono-, bis-, poly-imidazolium compounds, with symmetrical and non-symmetrical structures) and discussed. Their physico-chemical properties will be exposed in order to adduce the relevancy and potential of the imidazolium platform in various fields of research.
The formation of CuCl nanoplatelets from the ionic liquid precursor (ILP) butylpyridinium tetrachlorocuprate [C4Py](2)[CuCl4] using ascorbic acid as a reducing agent was investigated. In particular, electron paramagnetic resonance (EPR) spectroscopy was used to evaluate the interaction between ascorbic acid and the Cu(II) ion before reduction to Cu(I). EPR spectroscopy suggests that the [CuCl4](2-) ion in the neat IL is a distorted tetrahedron, consistent with DFT calculations. Addition of ascorbic acid leads to the removal of one chloride from the [CuCl4](2-) anion, as shown by DFT and the loss of symmetry by EPR. DFT furthermore suggests that the most stable adduct is formed when only one hydroxyl group of the ascorbic acid coordinates to the Cu(II) ion.