Nano

Water-soluble and stable dispersions of silver nanoparticles (Ag NPs) were obtained using a straightforward one-step synthesis method. Polyacrylamide (PAM), a kind of water-soluble polymer with polar amide group, is used as stabilizing agent to prevent the aggregation of Ag NPs in aqueous medium. The successful formation of PAM-stabilized Ag NPs was demonstrated by ultraviolet-visible spectroscopy (UV-Vis), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and Fourier-transform infrared spectroscopy (FTIR). In addition, the SERS-active substrate made of Ag NPs was fabricated to enhance the Raman signal of R6G and graphene. The significant SERS effective makes the as-synthesized substrate to be widely used in practical applications for routine SERS analysis and water environment biological monitoring.

Hierarchical Cu₂O nanostructures have been successfully fabricated on a large scale using copper acetate and glucose as starting reactants, CTAB as an additive via a microwave-assisted process. The influences of CTAB dosage and reaction time on the morphology of the products were investigated. The resulting Cu₂O nanostructures were characterized by means of X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM). FESEM images show that the Cu₂O nanostructures are microsphere, which are composed of nanoparticles. The concentration of CTAB plays a key role in the growth of Cu₂O nanostructures under experimental conditions. The possible formation mechanism of these hierarchical Cu₂O nanostructures has been proposed. Meanwhile, the catalytic performances of these Cu₂O microspheres for thermal decomposition of ammonium perchlorate (AP) were investigated using DSC. The results revealed that Cu₂O have a great influence on the thermal decomposition of AP. The additions of Cu₂O powders lower the high decomposition temperature of AP.

Effect of Al₂O₃ nanoparticles (80 nm) on the grain structure and phase formation in Ni-50Ti system during high-energy mechanical alloying (MA) was studied. While the formation of NiTi B2 phase occurs progressively during MA, it is shown that the hard inclusions cause abrupt phase formation at short milling times, particularly at higher nano-Al₂O₃ contents. High-resolution transmission electron microscopy showed significant grain refinement in the presence of alumina nanoparticles to sizes less than 10 nm, which precedes the formation of semicrystalline structure and reduces the diffusion length and thus accelerates the phase formation. The composite powder reached steady-state MA condition at shorter milling times with finer grain structure and higher hardness.

4-Mercaptovaleric acid (4MVA) and 3-mercaptovaleric acid (3MVA), two branched isomers of 5-mercaptovaleric acid (MVA), were designed and synthesized. They were used as capping agents in the aqueous synthesis of CdTe quantum dots (QDs) by a modified hydrothermal method with sodium tellurite as Te source. Compared with MVA-CdTe, either 4MVA-QDs or 3MVA-QDs exhibited higher fluorescent quantum yield (QY) and sharper absorption peak, which confirmed the superiority of using branched mercapto acids in the aqueous synthesis of QDs for improved optical properties. The fluorescence of QDs capped with 4MVA was higher than that of QDs capped with 4-mercaptobutyric acid (MBA) but lower than that of QDs capped with 3-mercaptobutyric acid (3MBA), which further confirmed the advantage of designing methyl side group rather than methylene group in the main chain for desired optical properties. However, the lower fluorescence, less sharp absorption peak and faster growth rate of 3MVA-QDs than that of 3MBA-QDs indicated adverse effect of side group on the aqueous synthesis of QDs if the size of side group is very bulky. Our results are helpful for selecting and designing appropriate capping agents for QDs with excellent properties.

Mesoporous silicas SBA-15 are modified with β-Cyclodextrins (β-CD) by simple grafting method. β-CD functionalized SBA-15 was characterized by Fourier transform infrared (FTIR) spectroscopy, transmission electron microscopy (TEM), scanning electron microscopy (SEM), powder X-ray diffraction (PXRD), nitrogen adsorption–desorption measurements, thermogravimetric analysis (TGA) and X-ray photoelectron spectroscopy (XPS). Furthermore, the applicability of it is investigated through studying the adsorption properties of clenbuterol. It showed better adsorption capacities of clenbuterol than pure SBA-15. β-CD functionalized SBA-15 material has the potential applications in the treatment of clenbuterol contamination in food and environment science.

The present work was addressed to study the visible light induced performance as photocatalysts of mesoporous N_yTi_1–xCe_xO_2–y structures obtained under microwave irradiation. The titanium dioxide (TiO₂) was doped with cerium and nitrogen in order to improve the quantum efficiency of the TiO₂ and to shift its adsorption spectra to the visible region. The prepared meso-powders were analyzed by means of X-ray diffraction (XRD), scanning Electron microscopy (SEM), infrared (IR) spectroscopy, transmission electronic microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The surface area was evaluated by means of the Brunauer-Emmett-Teller (BET) method and ultraviolet (UV)-visible diffuse reflectance measurements were performed in order to determine the band gap energy. In addition, the photocatalytic activity of the samples was evaluated by monitoring the photodegradation of methylene blue (MB) under UV and visible light energy irradiation. The results show that our methodology is an effective way for incorporating cerium and nitrogen into TiO₂ compound, which in turn, increases its photocatalytic activity. The diffuse reflectance analysis confirms that the absorption edge was shifted towards the visible region of the optical spectrum. The XRD diffraction patterns indicate homogeneous solid solutions in which prevails the anatase phase. It was observed a reduction in crystal size from 13.1 nm to 7.7 nm for N_yTi_0.98Ce_0.02O_2–y in comparison to TiO₂. The textural properties of the synthesized compounds were determined, by means of adsorption isotherms indicating the formation of mesoporous structures. IR spectra show characteristic vibration signals attributed to Ti–O–Ti bonds, as well as vibrations assigned to cerium and nitrogen bonds. The XPS analyses evidence the presence of Ce³⁺/Ce⁴⁺ redox couple and Ti–N bonds. The photocatalityc efficiency was evaluated in the degradation of MB monitoring the absorbance change at 664 nm. The degradation of this compound was 91.4% using N_yTi_0.98Ce_0.02O_2–y as photocatalyst under UV energy in 90 min. Also 38.7% of MB degradation was achieved in 150 min under visible light radiation.

Novel flower-like composite architecture was successfully synthesized by spray drying and post-calcinating method for the first time. Scanning electron microscopy and transmission electron microscopy observations confirmed that reduced graphene oxides/carbon nanotubes hybrid (rGO/CNTs) formed a flower-like micrometer structure and Cu₂O, CuO (Cu_xO, x = 1 or 2) nanoparticles were decorated inside them. The photocatalytic properties were further investigated by evaluating the photodegradation of a pollutant methyl orange (MO). The experimental results indicated that this novel architecture enhanced photocatalytic performance with 96.2% decomposition of MO after 25 min in the presence of H₂O₂ under visible light irradiation, which was much higher than that of Cu_xO powders (33.2%). This could be attributed to the more efficient adsorption of MO molecules on flower-like rGO/CNTs and provide a high concentration of MO near to the Cu_xO nanoparticles, thus promoting the photocatalytic degradation process.

In this paper, a new simple approach has been developed for the preparation of α-Fe₂O₃ microspheres by a facile hydrothermal method using PVP as a surfactant. Uniform α-Fe₂O₃ microspheres could be routinely synthesized through solvothermal approach by controlling the PVP/FeCl₃⋅6H₂O ratio. The as-obtained α-Fe₂O₃ microspheres exhibit high efficiency on the decolorization of RhB aqueous solution in the presence of H₂O₂ at room temperature.

Ultra-small and functional copper nanoclusters (Cu NCs) have been extensively used in consumer technologies due to their superior properties. A simple and green way to prepare stable, water-soluble and near-infrared (NIR) Cu NCs by using a reducing agent was reported in this work. Reduced glutathione (GSH) worked as an important scaffold to prevent NCs from aggregating. Since GSH has functional groups such as carboxyl and amino, it can also be used in reducing Cu²⁺ ions. The resulting GSH–Cu NCs with a particle size of 2.5 nm have good dispersibility in aqueous solution, and show NIR emission with a wavelength of 700 nm (quantum yield 0.6%). MC3T3-E1 cells are used as an example in the fluorescence imaging of GSH–Cu NCs. Several promising features including NIR fluorescence, good water-solubility and biocompatibility, bioactive surface and ultra-small size make the GSH–Cu NCs a good probe for cells.

The 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) nanoparticles were prepared by using semibatch reaction crystallization method, and the influencing factors in close relationship with the grain size and crystal morphology control, such as the concentration of reaction system and categories of surfactants, were studied in this paper. The synthesized nano-TATB particles had been characterized by SEM, XRD, thermo gravimetric/differential scanning calorimetric (TG/DSC) and N₂ physisorption. The grain size of TATB particles using nonionic surfactant as the additive ranged from 30 nm to 65 nm with a shape of spheres or ellipsoids. The broadening of the peaks and the weakening of the strength for nano-TATB were observed by XRD analysis. The corrected average particle size of nano-TATB was calculated using the Debye–Scherrer equation and the range was from 18 nm to 50 nm. TG and DSC curves revealed that thermal decomposition of nano-TATB occurred in the range of 361.5°C–385.0°C and its peak temperature was 373.7°C with a decrease of approximately 7°C compared with original TATB. Furthermore, the specific surface area (21.54 m²/g) of nano-TATB was calculated by BET method using N₂ physisorption (at 77°C).

The performance of a nanoscale sensor is not limited by the sensitivity of the sensor itself but rather by the diffusion time required for target molecules to reach to the extremely small sensor surface. In this work, we developed a carbon nanotube device that performed the dual functions of concentrating and detecting microorganisms in a sample solution. The sensor surface area was increased by fabricating a carbon nanotube network device using thermal chemical vapor deposition and standard microfabrication techniques. The target Escherichia coli (E. coli) cells were concentrated at the sensor surface via dielectrophoretic concentration by the carbon nanotube network channels. After 10 min of collection, the chip was washed with ample amounts of a clean buffer solution, and only the E. coli cells that were bound to the antibodies remained on the sensor surface. The binding of E. coli to the CNT network device decreased the conductance, presumably due to an increase in the scattering at the sensor surface. The detection limit and the time required for microorganism detection was greatly improved by combining dielectrophoresis with the carbon nanotube devices.

In this paper, the effect of environmental temperature on the radial breathing mode (RBM) frequency of single-walled carbon nanotubes (SWNTs) with arbitrary chirality is investigated. The analytical formulation is developed which can link the frequency to the geometrical parameters of the SWCNT and environmental temperature. Good agreement between the present results and existing experimental data is found. The results show that the predicted RBM frequencies of the SWCNTs decrease with increasing of temperature. The softening of the C–C force constants in the SWCNT is responsible for the temperature-induced downshift in the RBM frequencies.