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VLADIMIR M. MASALOV,ELENA A. KUDRENKO,NATALIA A. GRIGORYEVA,KSENIA V. EZDAKOVA,VLADIMIR V. RODDATIS,NADEZHDA S. SUKHININA,MIKHAIL V. AREFEV,ALEXANDER A. MISTONOV,SERGEI V. GRIGORIEV,GENNADI A. EMELCHE 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2013 NANO Vol.8 No.4
Ultramicrotomy was used to prepare a cross-section of shell-like amorphous SiO2 spherical particle synthesized by the multistage Stöber method which allowed performing first direct observations of the hierarchical structure of the SiO2 particle by transmission and scanning electron microscopy. The presence of primary, secondary and tertiary particles forming the inner structure of SiO2 spheres was established. The use of the small angle scattering of neutrons and synchrotron radiation techniques has enabled to define the size of the primary particles, the fractal parameters of their surface and the bulk density of the SiO2 spheres.
A new method has been proposed to realize the visual detection of Cr3+ using 4-nitrobenzenethiol (4-NBT) and 4-mercaptobenzoic acid (4-MBA) modified silver nanoparticles (AgNPs). The presence of Cr3+ induces the aggregation of AgNPs through cooperative metal–ligand interaction, resulting in a color change from bright yellow to purple. Consequently, Cr3+ could be monitored by colorimetric response of AgNPs by a UV-Vis spectrophotometer or even naked eyes. We firstly used ethylene diamine tetraacetic acid (EDTA) as a masking agent to selectively detect Cr3+, and other metal ions have little influence on the Cr3+–AgNPs system. The cofunctionalized AgNPs exhibited a highly sensitive detection limit of Cr3+, which is as low as 5 x 10-9 mol L-1, and the absorbance ratio (A600nm /A387nm) is linear with the concentration of Cr3+ ranging from 5 x 10-9 mol L-1 to 2 x 10-6 mol L-1 with a coefficient of 0.993. Particularly, the sensor has been further evaluated to monitor the concentration of Cr3+ in drinking water, the recovery was in good agreement with those obtained by ICP-MS, indicating that this proposed method is successfully applied in real samples.
The effect of ultraviolet, visible and near-infrared irradiation on the yield and morphology of single crystalline C60 fullerene nanowhiskers (FNWs) and nanotubes (FNTs) was investigated in an effort to produce large-scale quantities of FNWs and FNTs. These fullerene nanomaterials were synthesized by the liquid–liquid interfacial precipitation method using pyridine and isopropyl alcohol (IPA) as solvents. The C60–pyridine solution was illuminated using different wavelengths for 24 h at ambient pressure and temperature before addition of IPA. High yields (30–38 mg/L) were obtained upon irradiation using wavelengths in the ultraviolet region in accordance with the increased photoabsorption signal of solid C60 and C60 dissolved in pyridine acquired by a UV-VIS-NIR spectrophotometer. However, elevated yields (21–27 mg/L) were also obtained in the 600–800 nm regions, where C60 absorption is particularly weak. Such an enhanced yield of FNTs and FNWs is probably related to the reported rise in transient absorption of the triplet excited state of C60 in the 740 nm region formed by the decay of the photoexcited singlet C60 through intersystem crossing. The formation of photopolymerized fullerene nanofibers was also observed by Raman spectroscopy, it is attributed to ultraviolet and visible light irradiation. SEM and TEM observations suggest that preparation of FNWs and FNTs by irradiation using different wavelengths of light does not produce apparent morphological transformations on the surface of these fullerene materials.
Eco-friendly synthesis of metal nanoparticles has accrued utmost interest by researchers in the last decade for their distinct properties making them applicable in different fields of science and technology. With regard to its low cost, low environmental effect, zero contamination and higher reducing potential, their synthesis by green chemistry procedure is an emerging area in nanobiotechnology. Plant-based nanoparticles produced are more stable, with high rate of synthesis and are suitable for large scale biosynthesis as compared to the use of microorganisms which require stringent control on cell cultures. Plant-based nanoparticles have advantages over other methods due to presence of biomolecules acting both as capping and reducing agents by increasing the rate of reduction and stabilization of nanoparticles. Furthermore, secondary metabolites present in plants are used for reducing metal ions in single step reaction. In this review paper, we have cited 265 research articles and have outlined 106 plant extract assisted gold and silver nanoparticles. The present review highlights the achievements of metal nanoparticle synthesis, especially silver and gold nanoparticles from plant extracts, along with factors liable for the synthesis of metal nanoparticles. It also focuses on the dye degrading properties and various biological activities of metal nanoparticles, their antimicrobial mechanism of action and the physicochemical properties that influence the biological effects of metallic nanoparticles. Biological activities of metal nanoparticles were also described, including the effect of physicochemical properties of metal nanoparticles on biological activities.
A hierarchical mesoporous ZSM-5 catalyst with aggregated nanocrystals structure was one-pot hydrothermally synthesized by using urea as the additive. The crystalline phase, morphology and hierarchical architectures were characterized by the XRD, SEM, TEM and N2 adsorption/desorption analyses. The nano-aggregates showed MFI crystalline phase and were composed of connected nanoparticles. The samples had the high surface area and the pore volume from intercrystalline among the nanoparticles due to spontaneously stacking of nanocrystals. The pyridine-adsorbed FTIR and the catalytic performances in the alkylation of phenol and tert-butyl alcohol were applied to evaluate the accessibility of acid sites and the catalytic activities for the hierarchical mesoporous ZSM-5 samples. The samples possessed high accessibility of acid sites which resulted from their large amount of mesopores, and its catalytic activity was improved dramatically. The phenol conversion could reach up to 95.6%, and the corresponding selectivity of 4-TBP and 2,4-DTBP was 44% and 51.5%, respectively.
This paper introduces a new technique for analyzing the behavior of global interconnects in FPGAs, for nanoscale technologies. Using this new enhanced modeling method, new enhanced accurate expressions for calculating the propagation delay of global interconnects in nano-FPGAs have been derived. In order to verify the proposed model, we have performed the delay simulations in 45 nm, 65 nm, 90 nm, and 130 nm technology nodes, with our modeling method and the conventional Pi-model technique. Then, the results obtained from these two methods have been compared with HSPICE simulation results. The obtained results show a better match in the propagation delay computations for global interconnects between our proposed model and HSPICE simulations, with respect to the conventional techniques such as Pi-model. According to the obtained results, the difference between our model and HSPICE simulations in the mentioned technology nodes is (0.29–22.92)%, whereas this difference is (11.13–38.29)% for another model.
Sulfated TiO2 nanoparticles were successfully immobilized on zeolite through improving hydrolysis-deposition method. Microstructure, crystallization, surface state and surface area of composite catalysts were characterized by SEM, XRD, FTIR spectra, XPS and BET and the photocatalytic activity was evaluated by degradation of methyl orange under UV irradiation. We optimized these factors (SO4 -2) ions, calcination temperature and loading amount of sulfated TiO2) on photocatalytic activity and crystallization of composite photocatalysts. The results indicated that the SO4 -2 ) ions are successfully immobilized on the surface of TiO2, and sulfated TiO2/zeolite show the highest photocatalytic activity for methyl orange at the [SO4 -2]/[Ti4+] molar rate of 1:1, calcination temperature of 600 ℃ for 2 h, and sulfated TiO2 loading amount of 40%, respectively.
The yolk-shell Fe3O4-polyaniline for decoration of Pd-Ni nanoparticles (yolk-shell Fe3O4-PANI/ Pd-Ni) were synthesized and used as a new electrocatalyst for oxidation of formic acid. The yolkshell Fe3O4-PANI/Pd-Ni catalyst provided superior catalyst performance for formic acid oxidation in H2SO4 aqueous solution. These yolk-shell Fe3O4-PANI/Pd-Ni catalysts were found to be more resistant to deactivation in the oxidation of formic acid than yolk-shell Fe3O4-PANI/Pd and Pd/C and to consistently show better long-term performances. The enhanced catalytic performance may arise from the unique structure and surface properties of the yolk-shell Fe3O4- PANI and bi-functional effect, which process extraordinary promotional effect on Pd catalyst.
In this work, highly active graphitic carbon nitride composite photocatalysts with an isotype heterojunction semiconductor structure have been prepared through the molecular composite precursors consisting of urea and melamine. These photocatalysts were characterized by XRD, SEM, TEM, UV-Vis, BET and transient photocurrent responses. The photodegradation of dyes in aqueous solution under visible-light irradiation has been investigated over carbon nitride photocatalysts consisting of different urea/melamine mass ratios. Further studies by photocurrent indicate that the photosynergistic effect of isotype heterojunction can remarkably enhance the photoinduced interfacial charge transfer, thereby increasing the charge separation during the photocatalytic reaction.
"2,9,16,23-tetranitrophthalocyanine zinc (TNZnPc)/TiO2 organic–inorganic heterostructures were successfully fabricated by a simple combination method of electrospinning technique and solvothermal processing. These photocatalysts were characterized by X-ray diffraction, scanning electron microscope, transmission electron microscope, UV–Vis, energy dispersive X-ray and X-ray photoelectron spectroscopy. The photocatalytic studies revealed that the TNZnPc/TiO2 organic–inorganic heterostructures exhibited enhanced photocatalytic efficiency of photo-degradation of rhodamine B compared with pure TiO2 nanofibers under visible-light irradiation. Further studies indicate that the photosynergistic effect of organic–inorganic heterostructures can remarkably enhance the photoinduced interfacial charge transfer, thereby increasing the charge separation during the photocatalytic reaction."