Flame spray synthesis under a non-oxidizing atmosphere: Preparation of metallic bismuth nanoparticles and nanocrystalline bulk bismuth metal

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 glos

Particle Emission and Exposure during Nanoparticle Synthesis in Research Laboratories

Real-time size, mass and number particle concentrations, and emission rates in university laboratories producing nanoparticles by scalable flame spray pyrolysis are quantified. Measurements were conducted in four laboratories using various technological set-ups and during production of particles of a range of compositions with differing physical-chemical properties, from NaCl salt, BiPO4, CaSO4, Bi2O3, insoluble TiO2, SiO2, and WO3 to composites such as Cu/ZnO, Cu/SiO2, Cu/ZrO2, Ta2O5/SiO2, and Pt/Ba/Al2O3. Production time ranged from 0.25 to 400 min and yields from 0.33 to 183 g. Temporal and spatial analyses of the particle concentrations were performed indicating that elevated number concentrations in the workplace can occur. Airborne submicron number concentrations increased from background levels of 2100 up to 106 000 cm−3 during production, while the mass concentration ranged from a background of 0.009 to 0.463 mg m−3. Maximum particle number emission rates amounted to 1.17 × 1012 min−1. The size distributions displayed concentration peaks mainly between 110 and 180 nm. However, changes in the operating conditions and the production of certain nanoparticles resulted in concentration peaks in the nanoparticle size range <100 nm. The effectiveness and limitations of current technology in assessing researchers' exposure to nanoparticles during production are examined, and further measures for workers' protection are propose

Energy Consumption During Nanoparticle Production: How Economic is Dry Synthesis?

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 processe

Physico-Chemical Differences Between Particle- and Molecule-Derived Toxicity: Can We Make Inherently Safe Nanoparticles?

The rapidly growing applications of nanotechnology require a detailed understanding of benefits and risks, particularly in toxicology. The present study reviews the physical and chemical differences between particles and molecules when interacting with living organisms. In contrast to classical chemicals, the mobility of nanoparticles is governed by agglomeration, a clustering process that changes the characteristic size of the nanomaterials during exposure, toxicity tests or in the environment. The current status of nanotoxicology highlights non-classical toxic interactions through catalytic processes inside living cells and the enhanced heavy metal transport into the cytosol through the 'Trojan horse mechanism'. The safety of nanoparticles in consumer goods is proposed to be rendered inherently safer by substituting the currently used persistent oxides through biodegradable materials

Carbon coated magnetic nanoparticles as supports in microwave-assisted palladium catalyzed Suzuki-Miyaura couplings

A 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 suggeste

Compression coil provides increased lead control in extraction procedures

Aims We investigated a new lead extraction tool (Compression Coil; One-Tie, Cook Medical) in an experimental traction force study. Methods and results On 13 pacemaker leads (Setrox JS53, Biotronik) traction force testing was performed under different configurations. The leads were assigned to three groups: (i) traction force testing without central locking stylet support (n = 5), (ii) traction force testing with the use of a locking stylet (Liberator, Cook Medical) and a proximal ligation suture (n = 4), (iii) traction force testing with the use of a locking stylet and a compression coil (n = 4). The following parameters were obtained for all groups: stress-strain curves, maximal forces, elastic modulus, post-testing lead length and lead elongation. In Groups 2 and 3 retraction of the locking stylet within the lead was measured [lead tip-locking stylet distance (LTLSD)]. Maximal forces for the three groups were: (i) 28.3 ± 0.3 N; (ii) 30.6 ± 3.0 N; (iii) 31.6 ± 2.9 N (1 vs. 2, P = 0.13; 1 vs. 3, P = 0.04; 2 vs. 3, P = 0.65). Elastic modulus was (i) 22.8 ± 0.1 MPa; (ii) 2830.8 ± 351.1 MPa; (iii) 2447.0 ± 510.5 MPa (1 vs. 2, P < 0.01; 1 vs. 3, P < 0.01; 2 vs. 3, P = 0.26). Mean LTLSD in Group 2 was 19.8 ± 3.2 cm and was 13.8 ± 1.7 cm in Group 3 (P = 0.02). The ratio of LTLSD/post-testing lead length was 0.37 ± 0.03 for Group 2 and 0.24 ± 0.03 for Group 3 (P < 0.01). Conclusion The application of a compression coil leads to an increased lead control expressed by less retraction of the locking stylet within the lead. This enables improved central support of extraction sheaths in the case of challenging extraction procedure

Preparation of nano-gypsum from anhydrite nanoparticles: Strongly increased Vickers hardness and formation of calcium sulfate nano-needles

The preparation of calcium sulfate by flame synthesis resulted in the continuous production of anhydrite nanoparticles of 20-50nm size. After compaction and hardening by the addition of water, the anhydrite nanoparticles reacted to nano-gypsum which was confirmed by X-ray diffraction, diffuse reflectance IR spectroscopy and thermal analysis. Mechanical properties were investigated in terms of Vickers hardness and revealed an up to three times higher hardness of nano-gypsum if compared to conventional micron-sized construction material. The improved mechanical properties of nano-gypsum could in part be due to the presence of calcium sulfate nano-needles in the nano-gypsum as showed by electron microscop

Device for continuous extracorporeal blood purification using target-specific metal nanomagnets

Background. The present work illustrates how magnetic separation-based blood purification using ultra-strong iron nanomagnets can be implemented into an extracorporeal blood purification circuit. By this promising technique, today's blood purification may be extended to specifically filter high-molecular compounds without being limited by filter cut-offs or column surface saturation. Methods. Blood spiked with digoxin (small molecule drug) and interleukin-1β (inflammatory protein) was circulated ex vivo through a device composed of approved blood transfusion lines. Target-specific nanomagnets were continuously injected and subsequently recovered with the aid of a magnetic separator before recirculating the blood. Results. Magnetic blood purification was successfully carried out under flow conditions: already in single-pass experiments, removal efficiencies reached values of 75 and 40% for digoxin and interleukin-1β, respectively. Circulating 0.5 L of digoxin-intoxicated blood in a closed loop, digoxin concentration was decreased from initially toxic to therapeutic concentrations within 30 min and purification extents of 90% were achieved after 1.5 h. Conclusions. Magnetic separation can be successfully implemented into an extracorporeal blood purification device. Simultaneous and specific filtering of high-molecular compounds may offer promising new therapeutic tools for the future treatment of complex diseases, such as sepsis and autoimmune disorder

Immobilization on a Nanomagnetic Co/C Surface Using ROM Polymerization: Generation of a Hybrid Material as Support for a Recyclable Palladium Catalyst

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 PPh 3) 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

Suspension of Amorphous Calcium Phosphate Nanoparticles Impact Commitment of Human Adipose-Derived Stem Cells In Vitro

Amorphous calcium phosphate (aCaP) nanoparticles may trigger the osteogenic commitment of adipose-derived stem cells (ASCs) in vitro. The ASCs of three human donors are investigated using basal culture medium DMEM to either 5 or 50 µg/mL aCaP nanoparticles suspension (control: no nanoparticles). After 7 or 14 days, stem cell marker genes, as well as endothelial, osteogenic, chondrogenic, and adipogenic genes, are analyzed by qPCR. Free calcium and phosphate ion concentrations are assessed in the cell culture supernatant. After one week and 5 µg/mL aCaP, downregulation of osteogenic markers ALP and Runx2 is found, and averaged across the three donors. Our results show that after two weeks, ALP is further downregulated, but Runx2 is upregulated. Endothelial cell marker genes, such as CD31 and CD34, are upregulated with 50 µg/mL aCaP and a 2-week exposure. Inter-donor variability is high: Two out of three donors show a significant upregulation of ALP and Runx2 at day 14 with 50 µg/mL aCaP compared to 5 µg/mL aCaP. Notably, all changes in stem cell commitment are obtained in the absence of an osteogenic medium. While the chemical composition of the culture medium and the saturation status towards calcium phosphate phases remain approximately the same for all conditions, gene expression of ASCs changes considerably. Hence, aCaP nanoparticles show the potential to trigger osteogenic and endothelial commitment in ASCs