Treuel L.,Karlsruhe Institute of Technology |
Treuel L.,University of Duisburg - Essen |
Treuel L.,Fraunhofer Institute for Chemical Technology |
Brandholt S.,Karlsruhe Institute of Technology |
And 5 more authors.
ACS Nano | Year: 2014
Recent studies have firmly established that cellular uptake of nanoparticles is strongly affected by the presence and the physicochemical properties of a protein adsorption layer around these nanoparticles. Here, we have modified human serum albumin (HSA), a serum protein often used in model studies of protein adsorption onto nanoparticles, to alter its surface charge distribution and investigated the consequences for protein corona formation around small (radius ∼5 nm), dihydrolipoic acid-coated quantum dots (DHLA-QDs) by using fluorescence correlation spectroscopy. HSA modified by succinic anhydride (HSAsuc) to generate additional carboxyl groups on the protein surface showed a 3-fold decreased binding affinity toward the nanoparticles. A 1000-fold enhanced affinity was observed for HSA modified by ethylenediamine (HSAam) to increase the number of amino functions on the protein surface. Remarkably, HSAsuc formed a much thicker protein adsorption layer (8.1 nm) than native HSA (3.3 nm), indicating that it binds in a distinctly different orientation on the nanoparticle, whereas the HSAam corona (4.6 nm) is only slightly thicker. Notably, protein binding to DHLA-QDs was found to be entirely reversible, independent of the modification. We have also measured the extent and kinetics of internalization of these nanoparticles without and with adsorbed native and modified HSA by HeLa cells. Pronounced variations were observed, indicating that even small physicochemical changes of the protein corona may affect biological responses. © 2013 American Chemical Society.
News Article | December 1, 2016
The PCM cube maintains a temperature of 21 degrees Celsius until it is completley melted. Credit: Fraunhofer ICT When the summer sun burns in the sky, phase change materials (PCM) integrated in building envelopes absorb the heat – it remains cool inside. When it is getting colder outside, the materials give off heat. Several grams of these storage media can protect against overheating and undercooling for a long time. For the first time, researchers have combined insulating characteristics of foams with PCM thermal masses via established procedures of shaping processes. Due to this combination of materials the heat transfer through walls is reduced for hours. In the evening, it is nice and warm in the living room. However, when you enter the room in the morning it is chilly. It takes time until the heating gets started and the air in the room warms up again. Phase change materials – media made up of salts or organic compounds that store heat – can compensate for such temperature differences. Temperature peaks on hot summer days in indoor areas can also be mitigated. Researchers of the Fraunhofer Institute for Chemical Technology ICT in Pfinztal near Karlsruhe/Germany have combined the traditional advantages of a foamed insulation with the thermic regulating and storing characteristics of PCM within a single component. "The material is able to restore and give off huge amounts of heat within a short time intervall where it changes its temparature while tranforming to another aggregate condition. Via established procedures of shaping processes the PCM were integrated in foamed sheets for the first time. The next step will be to test the long-term resistance of these components," explains Sandra Pappert, a scientist at the ICT. Storage media are already available as microcapsules; they can be stirred into wall paint or plaster. What is special about the new technology: "Instead of a few micrograms, several grams of the phase change materials have been integrated. Therefore the thickness of the wall is not changing by increasing the thermal mass," says Pappert. The physical principle is known from lakes, which are covered by an ice layer on bitter cold days. Although the air is much colder, the water has a constant temperature of four degrees Celsius for the entire time until the last drop of water in the lake has frozen to ice. The freezing temperatures that the lake absorbs from the air do not cool the water down any further. Rather, they convert the water into ice. Phase change materials (technical term PCM) are able to absorb, restore and release huge amounts of heat in a small time intervall while changing their aggregate condition depending on their surrounding temperature. This works by storage media, such as salts or organic compounds, changing their aggregate states as soon as heat is added. If, for example, they change from the liquid to the solid state or vice versa, they absorb or release heat. Explore further: New study sheds light on cooling capacity of phase change materials
Nebhani L.,Karlsruhe Institute of Technology |
Schmiedl D.,Fraunhofer Institute for Chemical Technology |
Barner L.,Fraunhofer Institute for Chemical Technology |
Barner-Kowollik C.,Karlsruhe Institute of Technology
Advanced Functional Materials | Year: 2010
The surface modification of divinylbenzene (DVB)-based microspheres is performed via a combination of reversible addition fragmentation chain transfer (RAFT) polymerization and rapid hetero-Diels-Alder (HDA) chemistry with the aim of quantifying the grafting densities achieved using this "graftingto" method. Two variants of the RAFT-HDA concept are employed to achieve the functionalization of the microspheres. In the first approach, the microspheres are functionalized with a highly reactive diene, i.e., cyclopentadiene, and are subsequently reacted with polystyrene chains (number-averaged molecular weight, Mn = 4200g mol-1; polydispersity index, PDI = 1.12.) that carry a thiocarbonyl moiety functioning as a dienophile. The functionalization of the microspheres is achieved rapidly under ambient conditions, without the aid of an external catalyst. The surface grafting densities obtained are close to 1.2 × 1020 chains per gram of microspheres. In the second approach, the functionalization proceeds via the double bonds inherently available on the microspheres, which are reacted with poly(isobornyl acrylate) chains carrying a highly dienophilic thiocarbonyl functionality; two molecular weights (Mn = 6000 g mol-1, PDI = 1.25; Mn = 26 000 g mol-1, PDI = 1.26) are used. Due to the less reactive nature of the dienes in the second approach, functionalization is carried out at elevated temperatures (T= 60°C) yet in the absence of a catalyst In this case the surface grafting density is close to 7 chains nm-2 for Mn = 6000 g mol-1 and 4 chains nm-2 for M n = 26000 g mol-1, or 2.82 × 1019 and 1.38 × 1019chains g-1, respectively. The characterization of the microspheres at various functionalization stages is performed via elemental analysis for the quantification of the grafting densities and attenuated total reflectance (ATR) IR spectroscopy as well as confocal microscopy for the analysis of the surface chemistry. © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Zydziak N.,Karlsruhe Institute of Technology |
Zydziak N.,Fraunhofer Institute for Chemical Technology |
Yameen B.,Karlsruhe Institute of Technology |
Barner-Kowollik C.,Karlsruhe Institute of Technology
Polymer Chemistry | Year: 2013
To meet the ever growing demand for carbon nanomaterials with tailored properties, Diels-Alder reactions are emerging as an efficient alternative to other synthetic methods. From an application perspective, the development of convenient surface functionalization strategies for carbon nanostructures is of paramount importance. Pristine carbon nanostructures display a natural tendency to undergo Diels-Alder reactions with a range of functional dienes and dienophiles without the need of a catalyst. This has sparked significant scientific interest in exploiting the Diels-Alder reaction as a powerful strategy for their synthesis as well as for their subsequent surface functionalization. The present review highlights the remarkable role of Diels-Alder reactions for the synthesis of fullerenes, carbon nanotubes and graphene, and its promise as a facile carbon nanostructure functionalization strategy with small molecules and polymer chains. A critical overview of the recent developments evidencing the potential of Diels-Alder reactions as an efficient route to carbon based functional materials is presented. This journal is © 2013 The Royal Society of Chemistry.
Musyanovych A.,Fraunhofer Institute for Chemical Technology |
Musyanovych A.,Max Planck Institute for Polymer Research |
Landfester K.,Max Planck Institute for Polymer Research
Macromolecular Bioscience | Year: 2014
The design and development of multifunctional polymer capsules with controlled chemical composition and physical properties has been the focus of academic and industrial research in recent years. Especially in the biomedical field, the formulation of novel polymer-based encapsulation systems for the early-stage disease diagnostic and effective delivery of bioactive agents represent one of the most rapidly advancing areas of science. The stimuli-responsive release of cargo molecules from the carrier gains remarkable attention for in vitro and in vivo delivery of contrast agents, genes, and pharmaceutics. In this Review, the current status and the challenges of different polymer-based micro- and nanocapsule formulations are considered, emphasizing on their potential biological application as carriers for specific drug targeting and controlled release upon applying of external stimulus. A considerable research has been conducted in recent years on development of multifunctional polymer capsules with controlled chemical composition and physical properties. This Review discusses different types of bio-oriented polymer-based colloidal systems, emphasizing on formulation aspects, site-specific drug targeting, and controlled release of a "payload" upon applying of external stimulus. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Koch E.-C.,Information and Analysis Center |
Weiser V.,Fraunhofer Institute for Chemical Technology |
Roth E.,Fraunhofer Institute for Chemical Technology
Angewandte Chemie - International Edition | Year: 2012
Deceiving with TNT: Melt-cast pyrotechnic mixtures based on 2,4,6-trinitrotoluene (TNT)/KClO 4 (see picture for flame) spectrally matched infrared decoy flares and show superior performance and greatly reduced sensitivity in comparison to common pyrotechnic or double-base material currently in use for IR countermeasure flares. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Reza M.T.,Leibniz Institute for Agricultural Engineering |
Becker W.,Fraunhofer Institute for Chemical Technology |
Sachsenheimer K.,Fraunhofer Institute for Chemical Technology |
Mumme J.,Leibniz Institute for Agricultural Engineering
Bioresource Technology | Year: 2014
Near-infrared (NIR) spectroscopy was evaluated as a rapid method of predicting fiber components (hemicellulose, cellulose, lignin, and ash) and selective compounds of hydrochar and corresponding process liquor produced by hydrothermal carbonization (HTC) of maize silage. Several HTC reaction times and temperatures were applied and NIR spectra of both HTC solids and liquids were obtained and correlated with concentration determined from van-Soest fiber analysis, IC, and UHPLC. Partial least-squares regression was applied to calculate models for the prediction of selective substances. The model developed with the spectra had the best performance in 3-7 factors with a correlation coefficient, which varied between 0.9275-0.9880 and 0.9364-0.9957 for compounds in solid and liquid, respectively. Calculated root mean square errors of prediction (RMSEP) were 0.42-5.06. mg/kg. The preliminary results indicate that NIR, a widely applied technique, might be applied to determine chemical compounds in HTC solid and liquid. © 2014 Elsevier Ltd.
Konig A.,Fraunhofer Institute for Chemical Technology |
Kroke E.,TU Bergakademie Freiberg
Polymers for Advanced Technologies | Year: 2011
Flexible polyurethane foams are widely used in many industrial applications, such as upholstered furniture and mattresses, automotive applications, etc. The chemical nature of the polyurethane, the low density, the high air permeability, and the open cell structure cause this material to be highly flammable. In this study, the influencing variables on the burning behavior of flexible polyurethane foams are investigated. Additionally the synthesis, formulation, characterization, and testing of a new phosphorus flame retardant (FR) methyl-DOPO 9,10-dihydro-9-oxa-methylphosphaphenthrene-10-oxide in flexible polyurethane foam with low density is performed. The new FR shows an excellent flame retarding behavior by acting mainly in the gas phase. Here the vaporization of methyl-DOPO occurs in the same temperature region as the depolymerization of the urethane and the bisubstituted urea groups during pyrolysis of the foam. Furthermore TG-MS measurements revealed the release of high concentrations of low molecular weight species like HPO, CH3PO, or PO2 in the mentioned temperature region. These species are able to scavenge the H- and OH-radicals in the radical chain reactions of the flame leading to a significant increase of the CO/CO2 ratio during cone calorimeter experiments. © 2010 John Wiley & Sons, Ltd.
Konig A.,Fraunhofer Institute for Chemical Technology |
Kroke E.,TU Bergakademie Freiberg
Fire and Materials | Year: 2012
The chemical nature of flexible polyurethane (flex PU) foams, the low density, the high air permeability and the open cell structure cause this material to be highly flammable. The new phosphorus flame-retardant (FR) methyl-DOPO (9, 10-dihydro-9-oxa-methylphosphaphenanthrene-10-oxide) is known to show an excellent flame retarding behavior in flex PU foam by acting mainly in the gas phase. In this study, the FR working mechanism of methyl-DOPO and its ring-opened analogue MPPP (methylphenoxyphenyl-phosphinate) is investigated by TGA, TG-MS, FMVSS 302 and Cone Calorimeter measurements. Under TG-MS conditions comparable concentrations of low molecular weight species such as HPO, mathrmCH 3PO or PO 2 are released. These species are able to scavenge the H- and OH-radicals in the radical chain reactions of the flame leading to a significant increase in the CO/CO 2 ratio and the smoke density during cone calorimeter experiments. Finally, the flame retardancy of MPPP is determined to be less efficient in flex PU foam because of the higher vapor pressure compared with methyl-DOPO. Here, the vaporization of methyl-DOPO occurs in the same temperature region as the depolymerization of the urethane and the bisubstituted urea groups during pyrolysis of the foam leading to an optimal interaction. Copyright © 2010 John Wiley & Sons, Ltd.
Rehm T.H.,Fraunhofer Institute for Chemical Technology
Chemical Engineering and Technology | Year: 2016
The unique properties of fluorine resulting from its tremendously high electronegativity make it a key player in the quest of enabling new and advanced qualities for chemical compounds and materials. With the advent of fluorinating reagents, a great diversity of synthetic methodologies has been developed to incorporate fluorine or fluorine-containing groups into small molecules with high conversion and selectivity. Especially photochemically catalyzed fluorination reactions proved their potential for the synthesis of fluorine-containing fine chemicals due to their mild reaction conditions. This tutorial review gives an overview of recently published synthesis strategies that use (visible-) light-absorbing catalysts for the activation of fluorinating reagents. A special focus lies on the use of continuous-flow microreactors for photochemically catalyzed fluorination reactions due to the excellent utilization of this reactor equipment for photochemistry. Photochemically catalyzed fluorination reactions allow the mild and selective incorporation of fluorine and fluorine-containing groups into small molecules. In conjunction with continuous-flow microreactors this strategy is a powerful tool for enabling the facile and efficient synthesis of high-value chemical products for a broad field of applications. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.