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Counterfeit products are a problem known across many industries. Chemical products such as pharmaceuticals belong to the most targeted markets, with harmful consequences for consumer health and safety. However, many of the currently used anticounterfeit measures are associated with the packaging, with the readout method and level of security varying between different solutions. Identifiers that can be directly and safely mixed into the product to securely authenticate a batch would be desirable. For this purpose, we propose the use of chemical unclonable functions based on pools of short random DNA oligos, which allow the integration of a cryptographic authentication system into chemical products. We demonstrate and characterize a simplified workflow for readout, showing that results are robust and clearly differentiate between the correct tag and a counterfeit. As a proof of concept, we demonstrate the labeling of an acetaminophen formulation with a chemical unclonable function. The acetaminophen was successfully authenticated from a subsample of the product at a DNA admixing concentration of below 50 ng/g. Stability tests revealed that the readout is stable at room temperature for several years, exceeding the shelf life of most drug products. Our work thus shows that chemical unclonable functions are a valid alternative to state-of-the-art anticounterfeit methods, enabling a secure authentication scheme that is physically linked to the product and safe for consumption. The method is widely applicable beyond pharmaceuticals, allowing for more secure product tracing across industries.

The COVID-19 pandemic simultaneously disrupted supply chains and generated an urgent demand in medical infrastructure. Among personal protective equipment and ventilators, there was also an urgent demand for chemical oxygen. As devices to purify oxygen could not be manufactured and shipped rapidly enough, a simple and accessible oxygen concentrator based on pressure swing adsorption was developed at ETH Zurich in spring 2020. Instead of building devices locally and shipping them, it was decided to educate others in need of oxygen. The implementation encompassed education on process chemistry, material choice, and assembly and optimization of the concentrator and was realized using synchronous teaching tools, such as video call, and asynchronous ones, such as a website and video streaming. The project gained traction and interaction with engineering teams from universities and non-Governmental Organizations (Red Cross and the UN Development Program) in developing countries and emerging market economies, including Ecuador, Mexico, Somalia, and Peru. At the end of the project, the teams were surveyed regarding their experience in the educative knowledge transfer. It was reported that the learning experience prepared these groups well to build the device and to teach others as well. Major challenges were accessing some parts of the device and optimizing its performance. While synchronous communication is expected to be a very effective teaching method, the survey results showed that explanations via a website and video streaming have contributed the most to the implementation of the oxygen concentrator and thereby provide autonomous and sustainable education tools.

A core–shell strategy was developed to protect synthetic DNA in organosilica particles encompassing dithiol linkages allowing for a DNA loading of 1.1 wt %. DNA stability tests involving bleach as an oxidant showed that following the procedure DNA was sandwiched between core particles of ca. 450 nm size and a protective outer layer, separating the DNA from the environment. Rapid aging tests at 60 °C and 50% relative humidity revealed that the DNA protected within this material was significantly more stable than nonprotected DNA, with an expected ambient temperature half-life of over 60 years. Still, and due to the presence of the dithiol linkages in the backbone of the organosilica material, the particles degraded in the presence of reducing agents (TCEP and glutathione) and disintegrated within several days in a simulated compost environment, which was employed to test the biodegradability of the material. This is in contrast to DNA encapsulated following state of the art procedures in pure SiO2particles, which do not biodegrade in the investigated timeframes and conditions. The results show that synthetic DNA protected within dithiol comprising organosilica particles presents a strategy to store digital data at a high storage capacity for long time frames in a fully biodegradable format.

The need for tools that facilitate rapid detection and continuous monitoring of SARS-CoV-2 variants of concern (VOCs) is greater than ever, as these variants are more transmissible and therefore increase the pressure of COVID-19 on healthcare systems. To address this demand, we aimed at developing and evaluating a robust and fast diagnostic approach for the identification of SARS-CoV-2 VOC-associated spike gene mutations. Our diagnostic assays detect the E484K and N501Y single-nucleotide polymorphisms (SNPs) as well as a spike gene deletion (HV69/70) and can be run on standard laboratory equipment or on the portable rapid diagnostic technology platform peakPCR. The assays achieved excellent diagnostic performance when tested with RNA extracted from culture-derived SARS-CoV-2 VOC lineages and clinical samples collected in Equatorial Guinea, Central-West Africa. Simplicity of usage and the relatively low cost are advantages that make our approach well suitable for decentralized and rapid testing, especially in resource-limited settings.

Environmental tracers are chemical species that move with a fluid and allow us to understand its origin and material transport properties. DNA-based materials have been proposed and used for tracing due to their potential for multitracing with high specificity and sensitivity. For large-scale applications of this new material it is of interest to understand its impact on the environment. We therefore assessed the ecotoxicity of sub-micron silica particles with and without encapsulated DNA in the context of surface and underground tracing of natural waterflows using standard ecotoxicity assays according to ISO standards. Acute toxicity tests were performed with Daphnia magna(48 h), showing no effect on mobility at tracer concentrations below 300 ppm. Chronic ecotoxicological potential was tested with Raphidocelis subcapitata(green algae) (72 h) and Ceriodaphniaspecies (7 d) with no effect observed at realistic exposure scenario concentrations for both silica particles with and without encapsulated DNA. These results suggest that large-scale environmental tracing with DNA-tagged silica particles in the given exposure scenarios has a low impact on aquatic species with low trophic levels such as select algae and planktonic crustaceans.

A one-step photolithographic approach to patterning gold- and copper-coated surfaces is presented. The metal is selectively etched by the light-triggered local release of cyanide from a potassium ferrocyanide solution. The site-specific dissolution of gold by cyanide is extremely fast and essentially irreversible. An arbitrarily configurable light pattern can be produced with a commercial Digital Light Processing (DLP) projector directly pointed at the surface of the submerged sample. This procedure requires only minimal pre- and postprocessing operations and nontoxic chemicals. As an example of application, the rapid fabrication of a small two-zone differential heater is presented.

Because of its longevity and enormous information density, DNA is considered a promising data storage medium. In this work, we provide instructions for archiving digital information in the form of DNA and for subsequently retrieving it from the DNA. In principle, information can be represented in DNA by simply mapping the digital information to DNA and synthesizing it. However, imperfections in synthesis, sequencing, storage and handling of the DNA induce errors within the molecules, making error-free information storage challenging. The procedure discussed here enables error-free storage by protecting the information using error-correcting codes. Specifically, in this protocol, we provide the technical details and precise instructions for translating digital information to DNA sequences, physically handling the biomolecules, storing them and subsequently re-obtaining the information by sequencing the DNA. Along with the protocol, we provide computer code that automatically encodes digital information to DNA sequences and decodes the information back from DNA to a digital file. The required software is provided on a Github repository. The protocol relies on commercial DNA synthesis and DNA sequencing via Illumina dye sequencing, and requires 1–2 h of preparation time, 1/2 d for sequencing preparation and 2–4 h for data analysis. This protocol focuses on storage scales of ~100 kB to 15 MB, offering an ideal starting point for small experiments. It can be augmented to enable higher data volumes and random access to the data and also allows for future sequencing and synthesis technologies, by changing the parameters of the encoder/decoder to account for the corresponding error rates.

This review summarizes the development of whole-cell biosensors with a special focus on device development and cell immobilization. Integration of biosensor functions in a device will pave the way for field applications in remote areas and resource-limited settings. Firstly, an introduction to the field of whole-cell biosensors is provided, followed by examples of genetic engineering of cells in order to fulfill sensor functions. A framework of requirements to enable future field applications of biosensors is elaborated. A special focus is on different cell immobilization techniques ranging from polymers, to microfluidic devices, immobilization on paper and combinations of these methods. Looking at globally successfully implemented point of care devices such as a home pregnancy test or a blood glucose meter, we conclude the review with thoughts on long-term stability, portability, ease of use and user safety design guidelines for whole-cell biosensor devices.

We report improvements on the heat transfer and on the control strategy of a thermal cycler implemented on a novel device for performing a fast polymerase chain reaction (PCR). The reduction of the thermal mass of the sample holder and the direct contact with the sample allow for a significant reduction of the transition times, while the hybrid feedforward/feedback controller can rely on inexpensive components (actuators, sensors, processor) and still achieve minimal over/undershooting and good temperature stability. The design of the device has been improved by performing transient heat conduction analysis on the highly heat-conductive sample holder and on the solid metal body of the device which rapidly dissipates the excess heat produced during the thermal cycling. In the current setup, the sample holder hosts nine 1 μL samples covered with mineral oil, which can be simultaneously read in real time by the detection module designed in-house and installed on the device. An increase in speed of the PCR amplification was achieved with a reduction of the transition time of 63.8% when compared against a commercial real-time PCR machine. Our work shows that a complete, stand-alone, and ready-to-use quantitative PCR instrument can be fabricated from inexpensive and easily available components and it can achieve fast thermal cycling thanks to a hybrid control strategy.

A simple synthesis of fluorescent carbon quantum dots from lemon juice is described to introduce advanced high-school students and undergraduate college students to nanoparticle synthesis and quantum dots. The synthesis is based on the carbonization of lemon juice using only a hot plate stirrer. Column chromatography is used to separate different carbon quantum dots according to their size. This laboratory experiment can be carried out within a 2 h laboratory course and introduces the students to (1) nanotechnology and nanoparticle synthesis, using safe and commonly available chemicals. Furthermore, (2) the concept of fluorescence can be visualized in an intriguing manner using a pocket UV lamp. (3) This experiment serves as an introduction into size-exclusion chromatography. (4) An insight into possible sensing applications is given by the specific fluorescence quenching with an iron(III) solution. The experiment has been tested with 80 students in 4 Swiss high schools, and the knowledge of the students was tested before and after the experiment with a questionnaire. The performance increased by 0.42 ± 0.39 on a grading scale of 1 to 6. The calculated average effect size was 0.76, which is in the range of a medium- to large-effect size, indicating a favorable effect of the experiment on the nanoparticle knowledge of the students.

This study presents the first field validation of using DNA-labeled silica nanoparticles as tracers to image subsurface reservoirs by travel time based tomography. During a field campaign in Switzerland, we performed short-pulse tracer tests under a forced hydraulic head gradient to conduct a multisource–multireceiver tracer test and tomographic inversion, determining the two-dimensional hydraulic conductivity field between two vertical wells. Together with three traditional solute dye tracers, we injected spherical silica nanotracers, encoded with synthetic DNA molecules, which are protected by a silica layer against damage due to chemicals, microorganisms, and enzymes. Temporal moment analyses of the recorded tracer concentration breakthrough curves (BTCs) indicate higher mass recovery, less mean residence time, and smaller dispersion of the DNA-labeled nanotracers, compared to solute dye tracers. Importantly, travel time based tomography, using nanotracer BTCs, yields a satisfactory hydraulic conductivity tomogram, validated by the dye tracer results and previous field investigations. These advantages of DNA-labeled nanotracers, in comparison to traditional solute dye tracers, make them well-suited for tomographic reservoir characterizations in fields such as hydrogeology, petroleum engineering, and geothermal energy, particularly with respect to resolving preferential flow paths or the heterogeneity of contact surfaces or by enabling source zone characterizations of dense nonaqueous phase liquids.

Environmental tracing is a direct way to characterize aquifers, evaluate the solute transfer parameter in underground reservoirs, and track contamination. By performing multitracer tests, and translating the tracer breakthrough times into tomographic maps, key parameters such as a reservoir’s effective porosity and permeability field may be obtained. DNA, with its modular design, allows the generation of a virtually unlimited number of distinguishable tracers. To overcome the insufficient DNA stability due to microbial activity, heat, and chemical stress, we present a method to encapsulated DNA into silica with control over the particle size. The reliability of DNA quantification is improved by the sample preservation with NaN3and particle redispersion strategies. In both sand column and unconsolidated aquifer experiments, DNA-based particle tracers exhibited slightly earlier and sharper breakthrough than the traditional solute tracer uranine. The reason behind this observation is the size exclusion effect, whereby larger tracer particles are excluded from small pores, and are therefore transported with higher average velocity, which is pore size-dependent. Identical surface properties, and thus flow behavior, makes the new material an attractive tracer to characterize sandy groundwater reservoirs or to track multiple sources of contaminants with high spatial resolution.

A novel solvent-evaporation-based process that exploits template-particle stabilized bicontinuous emulsions for the formation of previously unreached membrane morphologies is reported in this article. Porous membranes have a wide range of applications spanning from water filtration, pharmaceutical purification, and battery separators to scaffolds for tissue engineering. Different situations require different membrane morphologies including various pore sizes and pore gradients. However, most of the previously reported membrane preparation procedures are restricted to specific morphologies and morphology alterations require an extensive optimization process. The tertiary system presented in this article, which consists of a poly(ether sulfone)/dimethylacetamide (PES/DMAc) solution, glycerol, and ZnO-nanoparticles, allows simple and exact tuning of pore diameters ranging from sub-20 nm, up to 100 nm. At the same time, the pore size gradient is controlled from 0 up to 840%/μm yielding extreme asymmetry. In addition to structural analysis, water flux rates of over 5600 L m–2h–1are measured for membranes retaining 45 nm silica beads.

A method to encapsulate DNA in heat-resistant and inert magnetic particles was developed. An inexpensive synthesis technique based on co-precipitation was utilized to produce Fe2O3nanoparticles, which were further functionalized with ammonium groups. DNA was adsorbed on this magnetic support, and the DNA/magnet nanocluster was surface coated with a dense silica layer by sol–gel chemistry. The materials were further surface modified with hexyltrimethoxysilane to achieve particle dispersibility in hydrophobic liquids. The hydrodynamic particle sizes were evaluated by analytical disc centrifugation, and the magnetic properties were investigated by vibrating sample magnetometry. The obtained nanoengineered encapsulates showed good dispersion abilities in various nonaqueous fluids and did not affect the optical properties of the hydrophobic dispersant when present at concentrations lower than 103μg/L. Upon magnetic separation and particle dissolution, the DNA could be recovered unharmed and was analyzed by quantitative real-time PCR and Sanger sequencing. DNA encapsulated within the magnetic particles was stable for 2 years in decalin at room temperature, and the stability was further tested at elevated temperatures. The new magnetic DNA/silica encapsulates were utilized to developed a low-cost platform for the tracing/tagging of oils and oil-derived products, requiring 1 μg/L = 1 ppb levels of the taggant and allowing quantification of taggant concentration on a logarithmic scale. The procedure was tested for the barcoding of a fuel (gasoline), a cosmetic oil (bergamot oil), and a food grade oil (extra virgin olive oil), being able to verify the authenticity of the products.

This work describes a magnetic separation‐based approach using polymyxin B‐functionalized metal alloy nanomagnets for the rapid elimination of endotoxins from human blood in vitro and functional assays to evaluate the biological relevance of the blood purification process. Playing a central role in gram‐negative sepsis, bacteria‐derived endotoxins are attractive therapeutic targets. However, both direct endotoxin detection in and removal from protein‐rich fluids remains challenging. We present the synthesis and functionalization of ultra‐magnetic cobalt/iron alloy nanoparticles and a magnetic separation‐based approach using polymyxin B‐functionalized nanomagnets to remove endotoxin from human blood in vitro. Conventional chromogenic Limulus Amebocyte Lysate assays confirm decreased endotoxin activity in purified compared to untreated samples. Functional assays assessing key steps in host defense against bacteria show an attenuated inflammatory mediator expression from human primary endothelial cells in response to purified blood samples compared to untreated blood and less chemotactic activity. Exposing Escherichia coli‐positive blood samples to polymyxin B‐functionalized nanomagnets even impairs the ability of gram‐negative bacteria to form colony forming units, thus making magnetic separation based blood purification a promising new approach for future sepsis treatment. Playing a central role in the development of gram‐negative sepsis, endotoxins are attractive therapeutic targets. However, their direct removal from protein‐rich fluids remains challenging. This article presents a magnetic separation‐based approach using polymyxin B‐functionalized metal nanomagnets to eliminate endotoxin from human blood in vitro. Functional assays show an attenuated inflammatory response from human endothelial cells and less chemotactic activity in purified samples.

The demand for low cost solar energy technology calls for manufacturing processes using economic liquid- or gas-phase synthesis of the corresponding materials. In this regard, manufacturing of quantum dot-sensitized solar cells is particularly complicated through multiple-step preparations. Material pairs such as TiO2–PbS heterojunctions have shown high absorption of visible light and good electron transfer properties. However, traditional solution processing requires extensive surface functionalization or the use of surfactants to obtain well-defined films. Such surfactants, unfortunately, often lower electron hopping/tunneling in the system (surfactants are usually insulators) and therefore have to be removed or exchanged before completing device fabrication. Similarly, the so far presented processes to deposit PbS directly on TiO2are very time consuming. In this paper, we present a single-step, large-scale, operable process to synthesize PbS–TiO2heterojunction particles by aerosol synthesis using reducing flame spray pyrolysis. Nanopowders with different lead sulfide to titanium dioxide ratios were produced and characterized. Thermodynamic equilibrium calculations of the gaseous environment during the combustion process show that the process is robust with regard to usual process changes or fluctuations. We further showed how this approach allowed us to vary the structure and size of the PbS–TiO2heterojunction particles, as long as an excess of sulfur species (S/Pb = 2.5) was applied during processing.

A simple structuring method for graphitic structures based on the catalytic properties of cerium oxide nanoparticles under oxidizing conditions is presented. Highly oriented pyrolytic graphite chips were impregnated with well-dispersed ceria nanoparticles and then treated at elevated temperatures for several hours. Oxidation activities on the particle surface appeared as crystallographically independent traces that were formed on the graphite and provide a simple method to manufacture nanogrooves at large scale. By altering treatment durations and temperatures, the optimal conditions and activity parameters of the particles were determined. A systematic AFM evaluation allowed formulating of a mechanism of the etching process. The findings provide a simple procedure for the patterning of graphitic structures, formation of nanogrooves and thereby a basic tool for material science with respect to the manufacturing of atmospheric nanofilters and ion-selective membranes.

AbstractA palladium bis-N-heterocyclic carbene complex was immobilized on polystyrene modified, magnetic carbon coated iron nanoparticles and evaluated in Suzuki-Miyaura cross-coupling reactions under conventional and microwave heating. Under the latter conditions, both aryl bromides and aryl chlorides could be employed as substrates at low loading of catalyst (0.2 mol%), which could be readily recovered by an external magnet and reused in at least four cycles. As a possible deactivation pathway of the catalyst, the formation of palladium nanoparticles in the course of the reaction that became encapsulated in the polystyrene matrix of the support is suggested.

The electrical properties of transparent, conductive layers prepared from nanoparticle dispersions of doped oxides are highly sensitive to impurities. Production of cost-effective thin conducting films for consumer electronics often employs wet processing such as spin and/or dip coating of surfactant-stabilized nanoparticle dispersions. This inherently results in entrainment of organic and inorganic impurities into the conducting layer leading to largely varying electrical conductivity. Therefore, this study provides a systematic investigation on the effect of insulating surfactants, small organic molecules and silica in terms of pressure dependent electrical resistivity as a result of different core/shell structures (layer thickness). Application of high temperature flame synthesis gives access to antimony-doped tin oxide (ATO) nanoparticles with high purity. This well-defined starting material was then subjected to representative film preparation processes using organic additives. In addition ATO nanoparticles were prepared with a homogeneous inorganic silica layer (silica layer thickness from 0.7 to 2 nm). Testing both organic and inorganic shell materials for the electronic transport through the nanoparticle composite allowed a systematic study on the influence of surface adsorbates (e.g., organic, insulating materials on the conducting nanoparticle’s surface) in comparison to well-known insulators such as silica. Insulating impurities or shells revealed a dominant influence of a tunneling effect on the overall layer resistance. Mechanical relaxation phenomena were found for 2 nm insulating shells for both large polymer surfactants and (inorganic) SiO2shells.

A novel organic/inorganic hybrid material comprising carbon‐coated cobalt nanoparticles and a poly(benzylchloride)styrene shell is the first magnetic support that complies with important requirements for immobilized reagents and scavengers, that is, stability under harsh conditions (e.g., acids), sufficient loading (up to 2 mmol g−1), and satisfying magnetization. The durability of the scaffold was demonstrated by immobilization of a trialkylsilane reagent, which served as a “magnetic” protecting group for a number of primary and secondary alcohols. Importantly, the scaffold could be efficiently separated, recycled, and reused after alcohol cleavage (HF⋅pyridine) via regeneration of the silyl chloride moiety with BCl3.

Das Verhalten von Nanopartikeln in biologischen Systemen dient als Grundlage zur Erforschung neuer medizinischer Behandlungsmethoden und ermöglicht die Entwicklung “sicherer” Nanotechnologie. Dieser Aufsatz diskutiert Moleküle und kleinste Partikel im Kontakt mit einzelnen Zellen oder ganzen Organismen mit Fokus auf anorganischen Materialien. Dabei treffen wir auf unerwartete, nicht‐klassische Verhaltensweisen solcher Partikel: veränderte Verteilungsmuster, chemisch aktive Grenzflächen und Festkörper mit dynamischem Verhalten. Die extern gesteuerte Platzierung von Medikamenten mithilfe von funktionalisierten Nanomagneten bringt Aspekte der Mechanik in die Arzneimittelforschung ein. In weiteren Abschnitten wird auf Persistenz und Bioakkumulation von Nanopartikeln mit Hinblick auf Langzeiteffekte eingegangen.

Understanding the behavior of nanoparticles in biological systems opens up new directions for medical treatments and is essential for the development of safe nanotechnology. This Review discusses molecules and nanoparticles when in contact with cells or whole organisms, with a focus on inorganic materials. The interaction of particles with biology unravels a series of new mechanisms not found for molecules: altered biodistribution, chemically reactive interfaces, and the combination of solid‐state properties and mobility. Externally guided movement of medicaments by using functional nanomagnets brings mechanics into drug design. In subsequent sections, the role of inertness and bioaccumulation is discussed in regard to the long‐term safety of nanoparticles.

Flame spray pyrolysis (FSP) was utilized to fabricate palladium in silica nanocomposites (core−shell structure) in a single step. The nanometer scale transformation of these materials to Pd dispersed on an amorphous silica matrix (oxide-supported noble metal) at elevated temperatures (500−900 °C) was investigated using transmission electron microscopy and CO chemisorption. A spatially resolved (1-D) population balance model was utilized to describe the transformation by diffusion and aggregation processes. The model describes the influence of temperature, matrix viscosity, particle sizes, and concentrations and enables a prediction of the morphology (core−shell vs supported) of metal/silica nanocomposites processed at elevated temperatures. The data are discussed in terms of aerosol formation mechanisms (consecutive vs simultaneous coagulation) and compared to literature data on the high-temperature formation of nanocomposites. To illustrate the validity of the physical model and mechanisms, a network modifier (CaO) was added to the glassy matrix of the composite (Pd/CaO/SiO2), decreasing the matrix viscosity and resulting in the predicted morphology.

A novel hybrid material is reported as support for a recyclable palladium catalyst via surface immobilization of a ligand onto Co‐based magnetic nanoparticles (NPs). A standard “click” reaction is utilized to covalently attach a norbornene tag (Nb‐tag) to the surface of the carbon coated cobalt NPs. The hybrid magnetic nanoparticles are produced by initiating polymerization of a mixture containing both Nb‐tagged ligand (Nb‐tagged PPh3) and Nb‐tagged carbon coated cobalt NPs. In turn, the norbornene units are suitably functionalized to serve as ligands for metal catalysts. A composite material is thus obtained which furnishes a loading that is one order of magnitude higher than the value obtained previously for the synthesis of functionalized Co/C‐nanopowders. This allows for its application as a hybrid support with high local catalyst concentrations, as demonstrated for the immobilization of a highly active and recyclable palladium complex for Suzuki‐Miyaura cross‐coupling reactions. Due to the explicit magnetic moment of the cobalt‐NPs, the overall magnetization of this organic/inorganic framework is significantly higher than of polymer coated iron oxide nanoparticles with comparable metal content, hence, its rapid separation from the reaction mixture and recycling via an external magnetic field is not hampered by the functionalized polymer shell.

Nanoparticles can serve as semi‐heterogeneous supports since they readily disperse in common solvents and combine high surface area with excellent accessibility. Reversible agglomeration through solvent changes and magnetic separation provide technically attractive alternatives to classical catalyst filtration. This account places emphasis on recent developments in this emerging area.

This work investigated the effect of adding nanoparticulate (29 nm) bioactive glass particles on the bioactivity, degradation and in vitrocytocompatibility of poly(3-hydroxybutyrate) (P(3HB)) composites/nano-sized bioactive glass (n-BG). Two different concentrations (10 and 20 wt ) of nanoscale bioactive glass particles of 45S5 Bioglass composition were used to prepare composite films. Several techniques (Raman spectroscopy, scanning electron microscopy, atomic force microscopy, energy dispersive X-ray) were used to monitor their surface and bioreactivity over a 45-day period of immersion in simulated body fluid (SBF). All results suggested the P(3HB)/n-BG composites to be highly bioactive, confirmed by the formation of hydroxyapatite on material surfaces upon immersion in SBF. The weight loss and water uptake were found to increase on increasing bioactive glass content. Cytocompatibility study (cell proliferation, cell attachment, alkaline phosphatase activity and osteocalcin production) using human MG-63 osteoblast-like cells in osteogenic and non-osteogenic medium showed that the composite substrates are suitable for cell attachment, proliferation and differentiation.

Durch nichtkovalente Anbindungdes gezeigten Pd‐Carben‐Komplexes an Graphen‐überzogene Cobaltnanopartikel wurde ein rezyklierbares System erhalten. Die Immobilisierung mithilfe von Pyren (siehe Schema, blaue Fläche) ist bei erhöhten Temperaturen reversibel, was den Einsatz als Homogenkatalysator ermöglicht. Mit diesem hochaktiven Katalysator wurden 16 iterative Hydroxycarbonylierungen von Arylhalogeniden durchgeführt.

Beyond the age of silicon: A combination of radical chemistry under standard conditions and clean‐room lithography can alter the electronic structure of graphene layers permanently through covalent chemical functionalization. The potential change follows the Hammett correlation. This simple method is a promising approach for graphene‐based electronics.

Nach der Ära des Siliciums:Die Verbindung zwischen Radikalchemie unter Standardbedingungen und Reinraumlithographie kann die elektronische Struktur von Graphenlagen durch kovalente chemische Funktionalisierung permanent verändern. Die Potentialveränderung folgt der Hammett‐Beziehung. Diese einfache Methode ist ein vielversprechender Ansatz für die graphenbasierte Elektronik.

X-ray amorphous tricalcium-phosphate nanoparticles (ATCP) produced by flame spray synthesis were heat-treated at temperatures between 500 and 1000 °C and analyzed in situ by X-ray powder diffraction. The main phase occurring after crystallisation at 525 °C was α-TCP, minor phases were identified as β-TCP and hydroxyapatite. More elevated temperatures induced crystallite growth and the transformation of α-TCP into β-TCP. Above 900 °C no α-TCP was traceable anymore. α’-TCP was not observed in the experiment. This study shows that nanoparticulate α-TCP can be obtained by thermal treatment of an amorphous TCP nanoparticle in a temperature range where sintering effects such as particle growth and densification are moderate or nearly negligible.

TEMPO was grafted on graphene‐coated nanobeads with a magnetic cobalt core by using a general applicable “click”‐chemistry protocol. The new heterogeneous CoNP–TEMPO emerged as a highly active catalyst for the chemoselective oxidation of primary and secondary alcohols using bleach as terminal oxidant. The outstanding stability of the C/Co nanoparticles enables the nanopowder to tolerate several TEMPO‐mediated iterative oxidation reactions without any significant loss in catalyst activity. Furthermore, the excellent magnetic properties enable the rapid separation and quantitative recycling of CoNP–TEMPO out of the reaction mixture by simple magnetic decantation. The recovered nanoparticles can be subsequently reused without any further purification.

The effect of composition on the reactivity of a calcium phosphate cement (CPC) made of tricalcium phosphate (TCP) – water mixtures was investigated by isothermal calorimetry at 37ºC. The parameters of interest were the mean particle size of the powder, the use of small amounts of nanosized hydroxyapatite powder, and the phosphate concentration and the pH of the aqueous solution. The results could be well explained by theoretical considerations. The main parameter controlling CPC reactivity was TCP particle size.

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Abstract: Metallic bismuth nanoparticles of over 98% purity were prepared by a modified flame spray synthesis method in an inert atmosphere by oxygen-deficient combustion of a bismuth-carboxylate based precursor. The samples were characterized by X-ray diffraction, thermal analysis and scanning electron microscopy confirming the formation of pure, crystalline metallic bismuth nanoparticles. Compression of the as-prepared powder resulted in highly dense, nanocrystalline pills with strong electrical conductivity and bright metallic gloss.

The production of oxide nanoparticles by selected wet-chemistry or dry processes is compared in terms of energy requirements. Clear differences arise for production using electricity-intensive plasma processes, organic- or chloride-derived flame synthesis and liquid based precipitation processes. In spite of short process chains and elegant reactor design, many dry methods inherently require vastly bigger energy consumption than the multi-step wet processes. Product composition strongly influences the selection of the preferred method of manufacturing in terms of energy requirement: Metal oxide nanoparticles of light elements with high valency, e.g. titania demand high volumes of organic precursors and traditional processes excel in terms of efficiency. Products with heavier elements, more complex composition and preferably lower valency such as doped ceria, zirconia, and most mixed oxide ceramics may be readily manufactured by recently developed dry processes.The production of oxide nanoparticles by selected wet-chemistry or dry processes is compared in terms of energy requirements. Clear differences arise for production using electricity-intensive plasma processes, organic- or chloride-derived flame synthesis and liquid based precipitation processes. In spite of short process chains and elegant reactor design, many dry methods inherently require vastly bigger energy consumption than the multi-step wet processes. Product composition strongly influences the selection of the preferred method of manufacturing in terms of energy requirement: Metal oxide nanoparticles of light elements with high valency, e.g. titania demand high volumes of organic precursors and traditional processes excel in terms of efficiency. Products with heavier elements, more complex composition and preferably lower valency such as doped ceria, zirconia, and most mixed oxide ceramics may be readily manufactured by recently developed dry processes.

Air stable cobalt nanoparticles have been prepared continuously at a production rate of 30 g h−1by a modified flame synthesis method under highly reducing conditions. Nanoparticles of 20–60 nm in diameter consisted of metallic face-centered-cubic cobalt. The metal particles were protected against oxidation by a surface layer of less than 1 nm of cobalt oxide. The material was highly magnetic exhibiting a high saturation magnetisation (>124 emu g−1) together with a low (<100 Oe) coercivity. Experiments under varying fuel to oxygen ratio were combined with thermodynamic calculations to illustrate the necessity for highly reducing conditions and enhanced gas mixing to enable the formation of metallic cobalt nanoparticles in flames.

Silica- and alumina-doped nanocrystalline ceria/zirconia (Ce0.5Zr0.5O2) were prepared in one step by flame-spray pyrolysis. Structural and textural properties were characterized using high-resolution electron microscopy, nitrogen adsorption and X-ray diffraction. Oxygen exchange capacity was studied by pulse thermal analysis using H2 as reducing agent. Adding silica (up to 20 wt%) or alumina (up to 16 wt%) altered the particle morphology from polyhedral to spherical particles. In doped ceria/zirconia, the oxygen exchange capacity (OEC) was affected by the silica content but very little by the alumina content. The highest OEC (450 mmol O2 kg−1) was measured for ceria/zirconia doped with 3 wt% silica, whereas for flame-made ceria/zirconia (360 mmol O2 kg−1) and corresponding precipitated silica- or alumina-doped materials the OEC was considerably lower. For high dopant contents (20 wt% silica) an amorphous layer was formed on top of a crystalline core. This layer acted as a diffusion barrier, so that the OEC dropped to about 76 mmol O2 kg−1.

The influence of trace amounts of transition metals (Cr, Mn, Fe, Co) on the structural and catalytic properties of silica and 1 wt% titania–silica nanoparticles prepared by flame synthesis has been investigated. The transition metal concentration was varied from 40 to about 2000 ppm by admixing the corresponding transition metal precursor to the silica and titania–silica precursor mixtures. These components were fed into a methane–oxygen diffusion flame, affording a single-step flame synthesis of the mixed oxide materials. The specific surface areas of all the powders thus prepared ranged from 60 to 240 m2 g−1, with oxygen flow being the most influential parameter. Diffuse reflectance UV-VIS and FT-IR spectroscopy showed that the Ti sites in the doped nanoparticles were unaffected by chromium, manganese, and cobalt, while iron led to the formation of a dual site with considerable acidity. Epoxidation of 2-cyclohexenol by tert-butylhydroperoxide (TBHP) was used to probe the effect of the transition metal dopants on the activity and selectivity of the titania–silica. A significant loss in selectivity to the epoxide was observed for all doped mixed oxides. The chromium-doped material was highly active, favoring radical processes. Even at a doping level of 40 ppm, considerable amounts of ketone by-products were formed. Manganese doping led to slow decomposition of the TBHP, but had no significant influence on the alkene conversion at Mn contents of up to 2000 ppm. Incorporation of iron afforded Lewis acid sites, leading to dehydration activity, as demonstrated by the occurence of water abstraction from the reactant. Cobalt-doped titania–silica showed only a weak tendency toward radical reactions, and no reactions due to Lewis acid sites were observed. Among the metal dopants, only chromium underwent significant leaching under reaction conditions.

Major advances in understanding aerosol formation and growth allow now production of nanoparticles with closely controlled characteristics so that some of the early promises of nanotechnology are materialized. The production of flame‐made titania particles coated in‐situ with vanadia was brought from a microreactor (4 g/h) to a pilot‐scale reactor (up to 200 g/h). Corresponding mixtures of titanium‐ and vanadium‐alkoxides were evaporated into a nitrogen or hydrogen stream and fed into a turbulent hydrogen/air or hydrogen/oxygen flame using a commercial burner. By controlling gas flow rates, burner configuration and type of oxidant, particles with a wide range of characteristics were made. Rutile rich (>85 wt%) to pure anatase (>99.5 wt%) powders were made by exchanging air with oxygen. Vanadia/titania catalysts were made with up to 10 wt% V2O5and were compared to powders made in the flame microreactor. A representative flame‐made DeNOx catalyst exhibited twice as much activity as a conventionally prepared reference catalyst for the removal of NO from a model exhaust gas by selective catalytic reduction with ammonia.

The structures of TiO₂–SiO₂ based aerogels and flame made particles, used as epoxidation catalysts, are compared by X-ray absorption near edge structure (XANES) spectroscopy and in situ XANES during dehydration of the calcined catalyst samples. The results are interpreted in terms of the titanium species present in the catalyst and the catalytic performance in the test reaction, the epoxidation of 2-cyclohexene-1-ol by tert-butylhydroperoxide (THBP) at 90 °C. XANES shows that tetrahedral titanium sites are the favoured sites at low TiO₂ concentrations (1–3.2 wt.% in this study). The catalytic performance (turnover frequency, selectivity) of such aerogels or flame made materials with low TiO₂ content is much better than that of corresponding samples with high TiO₂ content. In aerogels, regardless of the TiO₂ content, the amount of titanium with tetrahedral coordination increases significantly after dehydration at elevated temperature. In contrast, the pre-edge height and its position in the XANES spectra of the flame made catalyst samples is comparable, even without dehydration, to that of TS-1, which contains titanium in tetrahedral coordination. Thus the extent of tetrahedral Ti is intrinsically high in flame made catalysts and increases only slightly during the drying process. This behaviour can be attributed to the hydrophobic character of the flame made materials and ameliorates the catalytic performance, i.e. the selectivity.

Flame aerosol technology has been used to prepare titania/silica mixed oxide nanoparticles. A stream of argon containing evaporated hexamethyldisiloxane and titanium-tetraisopropoxide was brought into a methane–oxygen diffusion flame. Upon condensation, nanoparticles of titania/silica with high titania dispersion were formed. The powders were characterized using transmission electron microscopy, nitrogen adsorption, pore size analysis, laser-assisted ion-coupled plasma mass spectroscopy, UV–VIS spectroscopy, and diffuse reflectance IR spectroscopy. The powders consisted of agglomerates of primary particles from 10 to 20 nm in diameter at high oxygen-to-methane ratios in the flame. The morphology changed to larger, spherical particles when low oxygen-to-methane ratios were used. The catalytic materials were tested for the epoxidation of 2-cyclohexenol by tert.-butylhydroperoxide at 90°C. The activity and selectivity were investigated as a function of flame parameters used for catalyst preparation. The flame made catalysts showed better selectivity for the epoxidation than corresponding aerogels, but at lower activity. Epoxidation selectivity referred to TBHP reached 93%, whereas olefin selectivity was 83% at 80% conversion. The best catalytic performance was obtained with nanoparticles containing 1 to 3.2 wt% titania. The rate and selectivity achieved with the flame made catalysts were independent of the oxygen-to-methane ratio in the flame at high oxygen flow rate, whereas at low oxygen flow rate the activity and selectivity decreased considerably.

Flame aerosol synthesis has been used to prepare vanadia–titania nanoparticles with high activity for the selective catalytic reduction of NO by NH3. The mixed oxides were prepared from vanadium and titanium alkoxides which were evaporated into an argon stream and burned in a methane oxygen diffusion flame. Silica-containing samples were produced in a similar way by mixing hexamethyldisiloxane vapor into the precursor stream. Different flame structures were investigated for the effect of temperature and residence time on particle morphology, vanadia surface species, and overall catalytic activity. By changing the oxygen flow rate into the flame, particles with specific surface areas between 23 and 120 m2/g could be produced. High-resolution transmission electron microscopy (HRTEM) revealed that nanoparticles were spherical with diameters of 10 to 50 nm. X-ray photoelectron spectroscopy analysis indicated that vanadia was dispersed on the surface of the titania spheres. No indication for the presence of crystalline V2O5could be found by X-ray diffraction or HRTEM. Catalysts with a vanadia surface loading of 10 μmol/m2showed high activity with less than 1% N2O formation up to 350°C. Catalytic activity strongly depended on the vanadia loading; an increase from 2.5 to 7 μmol/m2resulted in a 30 times higher activity per vanadium. Addition of silica lowered the overall activity but did not change the activation energy. Raman spectroscopy indicated the presence of vanadate clusters. Temperature-programmed reduction corroborated that no significant amount of vanadia entered the titania lattice to form an interstitial solution. The selective catalytic reduction activity of as-prepared vanadia–titania is comparable to the best catalysts obtained by wet chemical methods.

The preparation of amorphous nanopowders by flame synthesis opens access to common soda-lime, metal-doped glasses or bioglasses in the range of 20–80 nm and offers an alternative to conventional wet-phase preparation, solid state reactions or melting.

Calcium carbonate nanoparticles of 20–50 nm size were obtained from a flame spray process where combustion of specific calcium-containing precursors results in amorphous or crystalline calcium carbonate particles depending on the spray flow conditions.

Non-oxidic salts such as NaCl, CaF2, SrF2and BaF2were synthesised using a flame spray method; optional doping of such fluorides with rare earth elements suggests possible applications in optics.

Spraying cerium and zirconium precursors dissolved in carboxylic acids into a methane–oxygen flame resulted in well-structured nanocrystals of ceria–zirconia mixed oxides with high temperature stability and surface area.

Magnetic separation‐based blood purification enables rapid and selective removal of endotoxin and bacteria from human whole blood. Functional assays assessing key steps in host defense against bacteria show an attenuated inflammatory response in purified samples and less chemotactic activity. Beatrice Beck‐Schimmer and co‐workers introduce on page 829this promising new approach for future sepsis treatment.

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Review: [96 refs.]