Water-Dispersible and Biocompatible Iron Carbide Nanoparticles with High Specific Absorption Rate.

Magnetic nanoparticles are important tools for biomedicine, where they serve as versatile multifunctional instruments for a wide range of applications. Among these applications, magnetic hyperthermia is of special interest for the destruction of tumors and triggering of drug delivery. However, many applications of magnetic nanoparticles require high-quality magnetic nanoparticles displaying high specific absorption rates (SARs), which remains a challenge today. We report here the functionalization and stabilization in aqueous media of highly magnetic 15 nm iron carbide nanoparticles featuring excellent heating power through magnetic induction. The challenge of achieving water solubility and colloidal stability was addressed by designing and using specific dopamine-based ligands. The resulting nanoparticles were completely stable for several months in water, phosphate, phosphate-buffered saline, and serum-containing media. Iron carbide nanoparticles displayed high SARs in water and viscous media (water/glycerol mixtures), even after extended exposition to water and oxygen (SAR up to 1000 W·g-1 in water at 100 kHz, 47 mT). The cytotoxicity and cellular uptake of iron carbide nanoparticles could be easily tuned and were highly dependent on the chemical structure of the ligands used.

High-capacitance Ti3C2Tx MXene obtained by etching submicron Ti3AlC2 grains grown in molten salt.

Submicron Ti3AlC2 grains are grown in molten salt. Etching the grains gives rise to small-sized Ti3C2Tx MXene particulates with capacitance more than twice that of the large ones derived from conventional high-temperature synthesis. Detailed electrochemical, structural, and spectroscopic studies demonstrate that increased capacitance predominantly originates from a decrease in the lateral size of the small Ti3C2Tx MXene particulates.

Electrochemical nucleophilic synthesis of di-tert-butyl-(4-[18F]fluoro-1,2-phenylene)-dicarbonate.

An electrochemical method with the ability to conduct (18)F-fluorination of aromatic molecules through direct nucleophilic fluorination of cationic intermediates is presented in this paper. The reaction was performed on a remote-controlled automatic platform. Nucleophilic electrochemical fluorination of tert-butyloxycarbonyl (Boc) protected catechol, an intermediate model molecule for the positron emission tomography (PET) probe (3,4-dihydroxy-6-[(18)F]fluoro-L-phenylalanine), was performed. Fluorination was achieved under potentiostatic anodic oxidation in acetonitrile containing Et3N·3HF and other supporting electrolytes. Radiofluorination efficiency was influenced by a number of variables, including the concentration of the precursor, concentration of Et3N·3HF, type of supporting electrolyte, temperature and time, as well as applied potentials. Radio-fluorination efficiency of 10.4±0.6% (n=4) and specific activity of up to 43GBq/mmol was obtained after 1h electrolysis of 0.1M of 4-tert-butyl-diboc-catechol in the acetonitrile solution of Et3N·3HF (0.033M) and NBu4PF6 (0.05M). Density functional theory (DFT) was employed to explain the tert-butyl functional group facilitation of electrochemical oxidation and subsequent fluorination.

Integrating oxaliplatin with highly luminescent carbon dots: an unprecedented theranostic agent for personalized medicine.

A theranostic nanomedicine (CD-Oxa) is synthesized by means of the condensation reaction between the amino groups on the surface of fluorescent carbon dots (CDs) and the carboxyl group of the oxaliplatin derivative Oxa(IV)-COOH. CD-Oxa, which integrates the optical properties of CDs and the anticancer function of oxaliplatin, could be used for simultaneous drug delivery and fluorescent tracking.

Facile synthesis of highly efficient and recyclable magnetic solid acid from biomass waste.

In this work, sawdust, a biomass waste, is converted into a magnetic porous carbonaceous (MPC) solid acid catalyst by an integrated fast pyrolysis-sulfonation process. The resultant magnetic solid acid has a porous structure with high surface area of 296.4 m(2) g(-1), which can be attributed to the catalytic effect of Fe. The catalytic activity and recyclability of the solid acid catalyst are evaluated during three typical acid-catalyzed reactions: esterification, dehydration, and hydrolysis. The favorable catalytic performance in all three reactions is attributed to the acid's high strength with 2.57 mmol g(-1) of total acid sites. Moreover, the solid acid can be reused five times without a noticeable decrease in catalytic activity, indicating the stability of the porous carbon (PC)-sulfonic acid group structure. The findings in the present work offer effective alternatives for environmentally friendly utilization of abundant biomass waste.

Synthesis, characterization and adsorptive properties of carbon with iron nanoparticles and iron carbide for the removal of As(V) from water.

This manuscript presents the synthesis of carbon modified with iron nanoparticles (CFe) and iron carbide (CarFe) from the pyrolyzed crown leaves of pineapple (Ananas comosus) treated with iron salts. The materials that were obtained were used for the removal of As(V) from aqueous media. The carbonaceous materials were characterized by Scanning Electron Microscopy (SEM), Transmission electron microscopy (TEM), X-ray diffraction (XRD), X-Ray Photoelectron Spectroscopy (XPS) and Mossbauer Spectroscopy. The specific area (BET), number site density and point of zero charge (pH(pzc)) were also determined. The kinetic parameters were obtained by fitting the experimental data to the pseudo-first-order and pseudo-second-order models. Different isotherm models were applied to describe the As(V) adsorption behavior. The kinetics of As(V) sorption by CFe and CarFe was well defined for the pseudo-second-order model (R(2) = 0.9994 and 0.999, respectively). The maximum As(V) uptake was 1.8 mg g(-1) for CFe and 1.4 mg g(-1) for CarFe. The results obtained indicated that both materials are equally useful for As(V) sorption. The As(V) experimental isotherm data were described by the Freundlich model for CFe and CarFe.

Liquid phase esterification of acetic acid over WO3 promoted ß-SiC in a solvent free system.

A series of tungstate promoted ß-SiC catalysts was synthesized by a wetness impregnation method. The as synthesized catalysts were unambiguously characterized by XRD, Raman, FTIR, XPS, UV-Vis DRS, TEM, BET surface areas and FE-SEM, and simultaneously the total amount of the acidity of the catalysts was estimated by NH(3)-TPD. The catalytic activities of the synthesized materials were tested in the liquid phase esterification of acetic acid with n-butanol in a solvent free medium. The reaction parameters were optimized to a temperature of 120 °C, molar ratio of butanol and acetic acid of 1:2 and a reaction time of 6 h after performing a number of experiments. Under the optimum conditions, the catalytic esterification revealed a significant effect of 88% conversion with 100% selectivity to butyl acetate in 20 wt% WO(3)/ß-SiC. This is the first report on the effective utilization of ß-SiC as a catalyst support for liquid phase esterification of acetic acid.

Synthesis and characterization of SiC and SiC/Si3N4 composite nano powders from waste material.

In the present work, nano silicon carbide has been prepared by pyrolysis of rice-husk ashes as starting materials. Three rice-husk ash samples having different features were used. The first was coarse-grained rice husk ash (fired husk as is), the second was fine rice husk ash (hand-ground), while the third was ball milled one. Effect of ball milling of the starting ashes for 6h on the formation of nano SiC was investigated and compared with those prepared without milling. The particle sizes of the prepared SiC materials were affected by the milling process. The particle sizes of the obtained nano SiC from ball milled staring materials were smaller than those prepared without milling. The pyrolysis conditions, i.e. the temperature and atmosphere were optimized. The optimum firing temperature to obtain well crystalline nano SiC was 1550°C. The effect of pyrolysis atmosphere, i.e. argon, vacuum and nitrogen was also demonstrated. The pyrolysis in argon exhibited lower efficiency on the formation of SiC than vacuum; while the pyrolysis in nitrogen atmosphere led to formation of SiC/Si(3)N(4) nanocomposite.

Parallel microwave chemistry in silicon carbide microtiter platforms: a review.

In this review, applications of silicon carbide-based microtiter platforms designed for use in combination with dedicated multimode microwave reactors are described. These platforms are employed not only for the efficient parallel synthesis of compound libraries, but also in the context of high-throughput reaction screening/optimization and a number of other (bio)analytical and biomedical applications. Since the semiconducting plate material (silicon carbide) is strongly microwave absorbing and possesses high thermal conductivity, no temperature gradients across the microtiter plate exist. Therefore, many of the disadvantages experienced in attempting to perform microtiter plate chemistry under conventional microwave conditions can be eliminated. In general, the silicon carbide-based microtiter platforms allow sealed vessel processing (either directly in the well or in glass vials placed into the wells) of volumes ranging from 0.02-3.0 mL at a maximum temperature/pressure limit of 200°C/20 bar. Depending on the specific plate and rotor configuration, a maximum of 80-192 transformations can be carried out in parallel in a single microwave irradiation experiment under strict temperature control. A platform type utilizing HPLC/GC vials as reaction vessels allows analysis directly from the reaction vessel eliminating the need for a transfer step from the reaction to the analysis vial. The latter system is particularly useful for analytical applications as well as reaction optimization/screening.

SiC avalanche photodiode array with microlenses.

A simple technique to incorporate microlenes with small photodiode arrays is demonstrated and analyzed. Using this method, the fill factor was increased from 2.6% to 22.4% for a two by two array. Simulation results are also shown. The photocurrent with microlens was approximately 8.6 times larger than without the microlens, which is consistent with simulation results.

Synthesis of nanostructured silicon carbide spheres from mesoporous C-SiO2 nanocomposites.

Nanostructured porous silicon carbide hollow spheres have been synthesized by phase separation in mesoporous silica-carbon nanocomposites at high temperatures and subsequent carbothermal reduction and crystallization.

Indium-catalyzed C-S cross-coupling of aryl halides with thiols.

Indium-catalyzed C-S cross-coupling of aromatic and alkane thiols with aryl halides proceeds smoothly in the presence of In(OTf)(3) (10 mol %), TMEDA (20 mol %), and KOH as a base in DMSO at 135 degrees C. When this protocol was utilized, a variety of thiols could be cross-coupled with aryl halides to afford the corresponding aryl sulfides in good to excellent yields.

Heavy metal removal from aqueous solution using carbonaceous K2S-impregnated adsorbent.

A novel carbonaceous adsorbent for heavy metal removal was prepared from raw coal by one-step simple sulfur impregnation using K2S. Raw coal was mixed with K2S powder and then heated at 800 degrees C for 30 min in nitrogen to produce K2S char. The sulfur content and form in K2S char were determined, and the ability of K2S char to adsorb Zn2+, Cd2+ and Pb2+ was examined. The K2S impregnation was effective at impregnating sulfur into coal, especially in the form of elemental, thiophenic and sulfatic sulfur. The sulfur content of K2S char was higher than those of raw coal and pyrolysis char. The Zn2+ removal in 2.4 mmol/L of Zn2+ solution by K2S char was higher than raw coal with the removal rate of 100%. K2S char adsorbed Pb2+ and Cd2+ in 24 mmol/L of Pb2+ and Cd2+ solution with the removal rate of 97% and 35%, respectively. The elution extents of adsorbed Pb2+ and Cd2+ were zero in distilled water and 27% in 0.1 mol/L HCl solution. These results indicated that an effective adsorbent for heavy metal ions was prepared from coal using K2S sulfur impregnation, and that the adsorbed metals were strongly retained in K2S char.

Influence of Na2S on the degradation kinetics of CCl4 in the presence of very pure iron.

This paper presents the results of kinetic studies to investigate the effect of FeS film formation on the degradation rate of CCl(4) by 99.99% pure metallic iron. The film was formed by submersing metallic iron grains in an oxygen free HCO(3)(-)/CO(3)(2-) electrolyte solution. When the grains had reached a quasi steady-state value of the corrosion potential, Na(2)S((aq)) was injected. Upon injection, a microm thick poorly crystalline FeS film formed immediately on the iron surface. Over time, the iron became strongly corroded and both the FeS film and the metallic iron grains began to crack leading to exposure of bare metallic iron to the solution. The effect of the surface film on the degradation rate of CCl(4) was investigated following four periods of aging, 1, 10, 30, and 60 days. Relative to the controls, the 1-day sulfide-aged iron showed a substantial decrease in rate of degradation of CCl(4.) However, over time, the rate of degradation increased and surpassed the degradation rate obtained in the controls. It has been proposed that CCl(4) is reduced to HCCl(3) by metallic iron by electron transfer. The FeS film is substantially less conducting than the bulk iron metal or non-stoichiometric magnetite and from the results of this study, greatly decreases the rate of CCl(4) degradation relative to iron that has not been exposed to Na(2)S. However, continued aging of the FeS film results in breakdown and stress-induced cracking of the film, followed by dissolution and cracking of the iron itself. The cracking of the bulk iron is believed to be a consequence of hydrogen embrittlement, which is promoted by sulfide. The increase in CCl(4) degradation rate, as the FeS films age, suggests that the process of hydrogen cracking increases the surface area available for charge transfer.

Synthesis of silicon carbide nanotubes by chemical vapor deposition.

Silicon carbide nanotubes (SiCNTs) were directly synthesized by chemical vapor deposition (CVD) in the paper. Methyltrichlorosilane (MTS) was selected as the SiC gaseous source and, ferrocence and thiophene as the catalyst and the cocatalyst, respectively. The influences of reaction temperature, contents of catalyst and cocatalyst, and content of gaseous source on the morphologies of the products were investigated, respectively. The products were identified by high-resolution transmission electron microscopy (HRTEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), and energy-dispersive X-ray (EDX), respectively. The synthesis of SiCNTs by CVD suggested a condition-dependent process. Novel SiCNTs, with 20 approximately 80 nm in outer diameter and 15 approximately 35 nm in inner diameter, respectively, were observed. The wall structure similar to that of carbon nanotubes was not found for the SiCNTs.

Synthesis of aminooxy-functionalized lanthanide(III) chelates for carbonyl-group conjugation.

The syntheses of three new aminooxy-tethered lanthanide(III) chelates, compounds 1-3, incorporating DOTA (= 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid), DTPA (= diethylenetriaminepentaacetic acid), or a substituted terpyridine (2,2',2'',2'''-[2,2': 6',2''-terpyridine-6,6''-diylbis(methylenenitrilo)]tetraacetic acid), respectively, are described. Reagents 1-3 can be used for carbonyl 'labeling', as shown by the formation of the corresponding oxime-ether bioconjugates of naltrexone (16) and 2-deoxy-beta-D-glucose (17) (Scheme 4).

Synthesis and characterization of SiC materials with hierarchical porosity obtained by replication techniques.

Porous silicon carbide monoliths were obtained using the infiltration of preformed SiO(2) frameworks with appropriate carbon precursors such as mesophase pitch. The initial SiO(2) monoliths possessed a hierarchical pore system, composed of an interpenetrating bicontinuous macropore structure and 13 nm mesopores confined in the macropore walls. After carbonization, further heat treatment at ca. 1,400 degrees C resulted in the formation of a SiC-SiO(2) composite, which was converted into a porous SiC monolith by post-treatment with ammonium fluoride solution. The resulting porous SiC featured high crystallinity, high chemical purity and showed a surface area of 280 m(2) g(-1) and a pore volume of 0.8 ml g(-1).

A study of silicon carbide synthesis from waste serpentine.

There are 60000 tons of serpentine wastes produced in year 2004 in Taiwan. This is due to the well-developed joints in the serpentine ore body as well as the stringent requirements of the particle size and chemical composition of serpentine by iron making company. The waste also creates considerable environmental problems. The purpose of this study is reutilization of waste serpentine to produce a high value silica powder after acid leaching. These siliceous microstructure products obtained from serpentine would be responsible for high reactivity and characteristic molecular sieving effect. In this study, the amorphous silica powder was then synthesized to silicon carbide with the C/SiO(2) molar ratio of 3. The experiment results show that silicon carbide can be synthesized in 1550 degrees C. The formed silicon carbide was whisker beta type SiC which can be used as raw materials for industry.

Combustion synthesis as a novel method for production of 1-D SiC nanostructures.

1-D nanostructures of cubic phase silicon carbide (beta-SiC) were efficiently produced by combustion synthesis of mixtures containing Si-containing compounds and halocarbons in a calorimetric bomb. The influence of the operating parameters on 1-D SiC formation yield was studied. The heat release, the heating rate, and the chamber pressure increase were monitored during the process. The composition and structural features of the products were characterized by elemental analysis, X-ray diffraction, differential thermal analysis/ thermogravimetric technique, Raman spectroscopy, scanning and transmission electron microscopy, and energy-dispersive X-ray spectrometry. This self-induced growth process can produce SiC nanofibers and nanotubes ca. 20-100 nm in diameter with the aspect ratio higher than 1000. Bulk scale Raman studies showed the product to be comprised of mostly cubic polytype of SiC and that finite size effects are present. We believe that the nucleation mechanism involving radical gaseous species is responsible for 1-D nanostructures growth. The present study has enlarged the family of nanofibers and nanotubes available and offers a possible, new general route to 1-D crystalline materials.