Carbon is anything but a new material, yet ubiquitously applicable for many catalytic transformations in modern organic chemistry. It is highly versatile, as it occurs as modifications abundantly ...available as 1–3D carbonaceous materials due to technical progress. In addition, materials such as activated charcoal, ordered mesoporous carbon (OMC), graphite and graphene (oxide), carbon nanotubes (CNTs), nanospheres (nano-onions, fullerenes), and many others are no “innocent” supports, as demonstrated by many recent publications within the revitalized field of “carbocatalysis”. By nature, carbon scaffolds offer a perfect link between nanoscaled matter and organic molecules, which makes them an ideal cornerstone for molecular catalysts. Apart from this inherent chemical significance, the physical properties (e.g., different conductivity) are equally important for the performance of heterogeneous or immobilized homogeneous catalysts. Careful selection of the carbon scaffold enables control of reactivity by tuning the electronic interactions of active sites with the support or among each other. Moreover, separation and recycling of “heterogenized” catalysts can be further improved by rendering carbon “magnetic”, that is, by incorporation of magnetic particles or by coating metal nanomagnets with graphene-like shells. Altogether, tuning the properties of carbon supports might lead to catalysts tailored not only in matters of reactivity (electron shuttle), but also to down-to-earth problems such as purification (magnetic separation and recycling). This critical review will highlight how far such concepts have already been implemented in the design of “heterogenized” catalysts and is meant to widen the perspectives where certain concepts have yet to be realized.
Over the last decades, the use of magnetic nanoparticles in research and commercial applications has increased dramatically. However, direct detection of trace quantities remains a challenge in terms ...of equipment cost, operating conditions and data acquisition times, especially in flowing conditions within complex media. Here we present the in-line, non-destructive detection of magnetic nanoparticles using high performance atomic magnetometers at ambient conditions in flowing media. We achieve sub-picomolar sensitivities measuring ~30 nm ferromagnetic iron and cobalt nanoparticles that are suitable for biomedical and industrial applications, under flowing conditions in water and whole blood. Additionally, we demonstrate real-time surveillance of the magnetic separation of nanoparticles from water and whole blood. Overall our system has the merit of in-line direct measurement of trace quantities of ferromagnetic nanoparticles with so far unreached sensitivities and could be applied in the biomedical field (diagnostics and therapeutics) but also in the industrial sector.
Thin‐walled, hollow carbon nanospheres with a hydrophobic interior and good water dispersability can be synthesized in two steps: First, metal nanoparticles, coated with a few layers of graphene‐like ...carbon, are selectively modified on the outside with a covalently attached hydrophilic polymer. Second, the metal core is removed at elevated temperature treatment with acid, leaving a well‐defined carbon‐based hydrophobic cavity. Loading experiments with the dye rhodamine B and doxorubicin confirmed the filling and release of a cargo and adjustment of a dynamic equilibrium (cargo‐loaded versus release). Rhodamine B preferably accumulates in the interior of the bubbles. Filled nanobubbles allowed constant dye release into pure water. Studies of the concentration‐dependent loading and release show an unusual hysteresis.
Hollow carbon nanobubbles: Water‐dispersible, carbon‐based nanobubbles, synthesized by metal templating, spontaneously take up cargo by hydrophobic interactions. The slow release of the cargo follows an unexpected out‐of‐equilibrium (hysteretic) behavior.
Herein, we present a water dispersable, magnetic nanoparticle supported "click and release" system. The cleavable linker has been synthesized by using a strain-promoted copper-free "click" reagent to ...establish the specific link and a fluoride cleavable silane moiety for mild cleavage. Small organic molecules, azide-bearing dyes and functionalized enzymes have been bound to the magnetic particle and released in a bioorthogonal way.
The count of circulating tumor cells (CTCs) has been associated with a worse prognosis in different types of cancer. Perioperatively, CTCs detach due to mechanical forces. Diagnostic tools exist to ...detect and isolate CTCs, but no therapeutic technique is currently available to remove CTCs in vivo from unprocessed blood. The aim of this study was to design and test new magnetic nanoparticles to purify whole blood from CTCs. Novel magnetic carbon-coated cobalt (C/Co) nanoparticles conjugated with anti-epithelial cell adhesion molecule (EpCAM) antibodies were synthesized, and their antifouling and separation properties were determined. The newly developed C/Co nanoparticles showed excellent separation and antifouling properties. They efficiently removed tumor cells that were added to healthy subjects’ blood samples, through an anti-EpCAM antibody interaction. The nanoparticles did not interact with other blood components, such as lymphocytes or the coagulation system. In blood samples of carcinoma patients suffering from metastatic disease, on average, ≥68% of CTCs were removed. These nanoparticles could prompt the development of a blood purification technology, such as a dialysis-like device, to perioperatively remove CTCs from the blood of cancer patients in vivo and potentially improve their prognosis.
The combination of force and flexibility enables controlled and soft movements. In sharp contrast, presently used machines are solid and mostly based on stiff driveshafts or cog wheels. Magnetic ...elastomers are realized through dispersion of small particles in polymer matrices and have attracted significant interest as soft actuators for controlled movement or conveying and are particularly attractive candidates for magnetic pump applications. At present, low magnetic particle loading and thus limited actuator strength have restricted the application of such materials. Here, the direct incorporation of metal microparticles into a very soft and flexible silicone and its application as an ultra‐flexible, yet strong magnetic tube, is described. Because metals have a far higher saturation magnetization and higher density than oxides, the resulting increased force/volume ratio afforded significantly stronger magnetic actuators with high mechanical stability, flexibility, and shape memory. Elliptical inner diameter shape of the tubing allowed a very efficient contraction of the tube by applying an external magnetic field. The combination of magnetic silicone tubes and a magnetic field generating device results in a magnetic peristaltic pump.
Magnetic silicone tubes with 67 wt% magnetic particles and an inner diameter of elliptical shape allow very efficient contractions of the tube by applying an external magnetic field. The combination of magnetic silicone tubes and a magnetic field generating device results in a magnetic peristaltic pump.
In this study, we demonstrate a two-step process where activated carbon based air purifier systems can be regenerated in situ and eliminate volatile organic compounds (VOCs) from indoor air in an ...energy efficient way. A carbon based adsorber was combined in series with a CeO2/TiO2 oxidative catalyst for total oxidation of the previously adsorbed and periodically released volatile organic compounds during regeneration runs. We investigated the adsorption and desorption behavior of five different VOCs (diethyl ether, limonene, linalool, hexanoic acid, triethylamine and n-decane) with thermogravimetric measurements, mass spectrometry and elemental analysis. Cyclic loading and regeneration experiments were carried out with selected VOCs (limonene, linalool and n-decane) for testing regeneration at elevated temperature. We showed that in situ thermal regeneration and subsequent oxidation of released VOC is a sustainable and easy applicable technology for indoor air purification. This two-step approach allows energy saving as the VOCs are eliminated discontinuously (enriching VOCs; periodic catalytic combustion), and is of high environmental and economic interest, as much less maintenance services are required.
Tris(2‐carboxyethyl)phosphine (TCEP) is an often‐used reducing agent in biochemistry owing to its selectivity towards disulfide bonds. As TCEP causes undesired consecutive side reactions in various ...analytical methods (e.g., gel electrophoresis, protein labeling), it is usually removed by means of dialysis or gel filtration. Here, an alternative method of separation is presented, namely the immobilization of TCEP on magnetic nanoparticles. This magnetic reagent provides a simple and rapid approach to remove the reducing agent after successful reduction. A reduction capacity of 70 μmol per gram of particles was achieved by using surface‐initiated atom transfer polymerization.
Tris(2‐carboxyethyl)phosphine (TCEP) is an often‐used reducing agent in biochemistry owing to its selectivity towards disulfide bonds. Because TCEP causes undesired consecutive side reactions in various analytical methods (e.g., gel electrophoresis, protein labeling), it is usually removed by means of dialysis or gel filtration. Here, an alternative method of separation is presented, namely the immobilization of TCEP on magnetic nanoparticles.
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