Authors:L. Zane Miller, James J. Rutowski, Jonathan A. Binns, Guillermo Orts-Gil, D. Tyler McQuade, and Jeremy L. Steinbacher
We present a rapid approach for forming monodisperse silica microcapsules decorated with metal oxide nanoparticles; the silica–metal oxide composites have a hierarchical architecture and a range of compositions. The details of the method were defined using titania precursors. Silica capsules containing low concentrations of titania (<1 wt. %) were produced via an interfacial reaction using a simple mesofluidic T-junction droplet generator. Increasing the titania content of the capsules was achieved using two related, flow-based postsynthetic approaches. In the first approach, a precursor solution containing titanium alkoxides was flowed through a packed-bed of capsules. The second approach provided the highest concentration of titania (3.5 wt. %) and was achieved by evaporating titanium precursor solutions onto a capsule packed-bed using air flow to accelerate evaporation. Decorated capsules, regardless of the method, were annealed to improve the titania crystallinity and analyzed by optical microscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX), powder X-ray diffraction (PXRD), and Fourier transform infrared (FT-IR) spectroscopy. The photocatalytic properties were then compared to a commercial nanoparticulate titania, which the microcapsule-supported titania outperformed in terms of rate of degradation of an organic dye and recyclability. Finally, the generality of the flow-based surface decoration procedures was demonstrated by synthesizing several composite transition metal oxide–silica microparticle materials.
Authors:Tayyebeh Madrakian, Abbas Afkhami, and Mohammad Rahimi
Arsenazo III modified maghemite nanoparticles (A-MMNPs) was used for removing and preconcentration of U(VI) from aqueous samples.
The effects of contact time, amount of adsorbent, pH and competitive ions was investigated. The experimental results were
fitted to the Langmuir adsorption model in the studied concentration range of uranium (1.0 × 10−4–1.0 × 10−2 mol L−1). According to the results obtained by Langmuir equation, the maximum adsorption capacity for the adsorption of U(VI) on
A-MMNPs was 285 mg g−1 at pH 7. The adsorbed uranium on the A-MMNPs was then desorbed by 0.5 mol L−1 NaOH solution and determined spectrophotometrically. A preconcentration factor of 400 was achieved in this method. The calibration
graph was linear in the range 0.04–2.4 ng mL−1 (1.0 × 10−10–1.0 × 10−8 mol L−1) of U(VI) with a correlation coefficient of 0.997. The detection limit of the method for determination of U(VI) was 0.01 ng mL−1 and the relative standard deviation (R.S.D.) for the determination of 1.43 and 2.38 ng mL−1 of U(VI) was 3.62% and 1.17% (n = 5), respectively. The method was applied to the determination of U(VI) in water samples.
Authors:Mircea Stefanescu, Marcela Stoia, Costica Caizer, Thomas Dippong, and Paul Barvinschi
This paper presents a study for the preparation of CoxFe3−xO4 (x = 0.02, 0.2, 0.5, 0.8, 1.0, 1.1, 1.5) nanoparticles, starting from metal nitrates: Co(NO3)2·6H2O, Fe(NO3)3·9H2O and ethylene glycol (C2H6O2). By heating the solutions metal nitrates-ethylene glycol, the redox reaction took place between the anion NO3− and OH–(CH2)2–OH with formation of carboxylate anions. The resulted carboxylate anions reacted with Co(II) and Fe(III) cations to form
coordinative compounds which are precursors for cobalt ferrite. XRD and magnetic measurements have evidenced the formation
of cobalt ferrite for all studied molar ratios. The average diameter of the cobalt ferrite crystallites was estimated from
XRD data and showed values in the range 10–20 nm. The crystallites size depends on the annealing temperature. The magnetization
of the synthesized samples depends on the molar ratio Co/Fe and on the annealing temperature.
Authors:Mohamadreza Bakht, Mahdi Sadeghi, and Claudio Tenreiro
Application of nanoparticles in nuclear medicine has aimed to develop diagnosis and therapeutic techniques. Cerium oxide nanoparticles
(CNPs) are expected to be useful for protection of healthy tissue from radiation-induced harm and could serve therapeutic
function. Among a variety of cerium radioisotopes, 137mCe (T1/2 = 34.4 h, IT (99.22%), β+ (0.779%)) could be a novel candidate radionuclide in the field of diagnosis owing to its appropriate half-life, 99.91% natural
abundance of target and its intense gamma line at 254.29 keV. In this study, 137mCe excitation function via the natLa(p,3n) reaction was calculated by TALYS-1.2 and EMPIRE-3 codes. The excitation function calculations demonstrated that the
natLa(p,3n)137mCe reaction leads to the formation of the 136/138Ce isotopic contamination in the 22–35 MeV energy range. Interestingly, the isotopic impurities of 137mCe could serve radio protector function. Overall results indicate that the cyclotron produced 137mCeO2 nanoparticles by irradiation of a target encompassing lanthanum oxide nanoparticles could be a potent alternative for conventional
diagnostic radionuclides with simultaneous radioprotection capacity.
Authors:Julian Schülein, Ingo Minrath, Rainer Pommersheim, and Holger Löwe
To synthesize nickel(0) nanoparticles by wet chemical reduction using hydrazine with an average size distribution below 100 nm, two different reactor concepts were developed. With a cone channel nozzle, the reactant solutions were sprayed into a batch for further processing and reduction at elevated temperatures. Another concept uses a micro-coaxial injection mixer connected to a heated tube to establish a fully continuously operating reactor. To shorten the time for reduction of the nickel, salt temperatures up to 180 °C are applied. To avoid uncontrolled residence time, the whole system was pressurized up to 80 bar. Approximately 80 L reactant solution, i.e., 1 kg nickel(0) nanoparticles, could be processed within 30 h.
Authors:I. Blanco, L. Abate, F. A. Bottino, P. Bottino, and M. A. Chiacchio
In recent years, polymer–nanoparticle composite materials have attracted the interest of a number of researchers because of their synergistic and hybrid properties derived from several components [ 1 – 8
Authors:Roberto Ricciardi, Jurriaan Huskens, and Willem Verboom
Dendrimer-encapsulated Au/Ag alloy nanoparticles (Au/Ag DENs) were covalently attached to a monolayer-functionalized inner surface of glass microreactors. The influence of the bimetallic alloy structure and of the different metal ratios was investigated for the reduction of 4-nitrophenol using NaBH4. TheAu/Ag—dendrimer nanocomposite with a 1:1 Au/Ag metal ratio showed the highest activity as compared to othermetal ratios and to pure Ag and Au. The dendrimer template exerted a stabilizing effect for six consecutive days of use with almost no decrease in conversion. This strategy enables the screening and investigation of a variety of bimetallic nanocatalysts in continuous-flow microreactors.
Authors:Shi Xu, Sheng Li, Yun Wei, Li Zhang, and Fei Xu
follows: water-free FeCl 3 and TiO 2 nanoparticles prepared from the previous step, in equimolar ratio, were ground in an agate mortar until mixed fully. Then the thiophene monomer, in equimolar ratio, was added dropwise into the above mixture with
Authors:Zongxue Yu, Yuxi Sun, Wenxian Wei, Lude Lu, and Xin Wang
Orthorhombic structural perovskite NdCrO3 nanocrystals with size of 60 nm were prepared by microemulsion method, and characterized by XRD, TEM, HRTEM, SEM, EDS and
BET. The catalytic effect of the NdCrO3 for thermal decomposition of ammonium perchlorate (AP) was investigated by DSC and TG-MS. The results revealed that the NdCrO3 nanoparticles had effective catalysis on the thermal decomposition of AP. Adding 2% of NdCrO3 nanoparticles to AP decreased the temperature of thermal decomposition by 87° and increased the heat of decomposition from
590 to 1073 J g−1. Gaseous products of thermal decomposition of AP were NH3, H2O, O2, HCl, N2O, NO, NO2 and Cl2. The mechanism of catalytic action was based on the presence of superoxide ion O2− on the surface of NdCrO3, and the difference of thermal decomposition of AP with 2% of NdCrO3 and pure AP was mainly caused by the different extent of oxidation of ammonium.