International Journal of Nanoscience

In this paper, a simple, low-cost and efficient method was adopted to fabricate large-area Si nanowire (SiNW) arrays by inserting the p-type (100) silicon wafer into aqueous HF + AgNO₃ solution for a certain time at room temperature. Surface of the silicon wafer with high aspect ratio SiNW shows the characteristics of low-reflection as low as 5% in the 450–800 nm wavelength range, especially less than 1% after etching for 60 min. The surface also exhibits super-hydrophobicity with water contact angle up to 150°. We investigated the relationship between the etching duration and aspect ratio of the SiNW systematically and demonstrated that the aspect ratio of the SiNW can be controlled. The antireflection surface shows a potential implication in increasing the conversation efficiency for solar cells, and the self-cleaning properties will further enhance the resistance to environment conditions for a long-life work.

The cuprous oxide nanoparticles were prepared with glucose as reducing agent by a wet-chemical method. The composition and structure of the catalysts were characterized with XRD and SEM analysis. The catalytic activity and stability of the catalyst for the H₂O₂ reduction were studied using the curves of cyclic voltammetry and chronoamperometry. The results showed that the crystal structure of the synthesized Cu₂O was the pure cubic phase and the crystallite size was about 19.5 nm. The Cu₂O powder was spherical and the average diameter of the spheres is about 1.0 μm. The Cu₂O nanoparticles were active for H₂O₂ electroreduction and the current density was about 30 mA cm^-2 at E = -0.4 V.

Phosphorus (P) is one of the main triggering nutrients responsible for eutrophication which troubles many waters in China. This study was to investigate the influencing factors of limestone (LS) adsorption and establish the parameter of constructed wetland (CW) using LS as the main substrate when treating effluent from a municipal wastewater treatment plant (MWTP) for P removal. First, a series of batch experiments were conducted to study the influencing factors of LS adsorption. Consequently, the P removal efficiency increased with the temperature and was high during the initial 3 h; the efficiency was over 75% even at initial P content 50 mg/L; under 2 mm small LS particle size enhanced the adsorption but the difference was not significant; the efficiency was over 90% when initial pH was below 6.37 and decreased sharply at pH above 8.15; sodium chloride as background electrolyte decreased the adsorption; organic acids including tartaric acid, oxalic acid and citric acid all suppressed the adsorption, and citric acid demonstrated the strongest effect. Then column experiment was conducted to evaluate the effect of the continuous vertical-flow LS bed treating effluent from a MWTP with varying hydraulic retention time (HRT). Over 80 days, the effluent pH was between 7 and 9, and effective running time increased with HRT during which the effluent total P content was below 0.5 mg/L. Short HRT such as 1 h or 1.5 h was recommended for dynamic LS adsorption. It showed that LS was suitable for the substrate in CW for P removal in wastewater advanced treatment.

As the inland waterway transportation developed rapidly in China, the frequency of hazardous chemical leakage accidents is increasing every year. Such pollution to inland river environment has become a world-wide issue. Montmorillonite (Mont) is typical 2:1 layer type silicate clay and due to their special structure, it has been used in organic pollution removal process. In order to improve their ability in pollution adsorption, the pillared Mont was made in this work. Since the common toxic structure in most chemical pollutants is the halogen atom-benzene ring part, we select a typical compound Monochlorobenzene (MCB) as the aim contaminant. In this research, the original Mont, Na–Mont, TiO₂ and TiO₂–Mont were prepared and used in MCB degradation experiment as catalysts. The influence of catalyst amount, promoter (H₂O₂) amount, MCB concentration and reaction time to MCB removal rate were studied, respectively in detail.

Surface-modified carbon nanotubes (CNTs) and nano-Ce–Zr mixed oxides (CZO) were prepared and employed initially as supports of H₃PW₁₂O₄₀ (HPW) for NO_x adsorption–decomposition. Both CNTs and nano-CZO are favorable supports for HPW. After loading with HPW, the NO_x adsorption efficiency increases, especially for HPW/CZO in which the highest adsorption efficiency can achieve 98% at the HPW loading of 70%, much higher than that of single HPW. NO_x adsorption efficiency can be influenced considerably by catalyst preparing conditions, in particularly, ethyl alcohol is superior to water as solvent for HPW loading onto CNTs; the –OH containing CNTs shows better promotion effect on the adsorption of NO_x than that containing –COOH when using absolute ethyl alcohol as solvent; mechanical grinding method is superior to incipient impregnation method in loading HPW onto the support of CZO. For both catalysts of HPW/CNTs and HPW/CZO, with the increase of HPW loading, the NO_x adsorption efficiency tends to reach a peak value before dropping down. Heated from 150°C to 450°C at a rate of 50°C/min, the adsorbed NO was found to decompose into N₂, O₂ and N₂O, and yields of N₂ being 21.8% and 27.3%, respectively for HPW/CNTs and HPW/CZO were obtained.

In this paper, magnetic mesoporous silica nanoparticles (Fe₃O₄–nSiO₂–mSiO₂) were synthesized using trimethylbenzene (TMB) as a swelling agent. These composite nanoparticles have a typical sandwich structure with a magnetic core, a nonporous silica middle layer and an ordered mesoporous silica outer shell. The experimental results indicate that the magnetic mesoporous silica nanoparticles have high specific surface area (510 m²/g), large pore size (3.8 nm) and pore volume (1.04 cm³/g). The thickness and pore structure of the out shell can also be easily tailored by adjusting the reaction conditions. The obtained nanomaterials were characterized by X-ray diffraction, transmission electron microscopy and nitrogen adsorption–desorption measurements.

Directed self-assembly of nano or microsized materials as building blocks is a very exciting research topic to construct large-scale but still uniform 2D or 3D architectures. Graphene shows great potential as an advanced building block for fabricating varied graphene-based functional films or architectures together with other metal, metal oxide and semiconductor nanomaterials. In our work, we demonstrated an approach to fabrication of flexible, transparent conductive thin films via layer-by-layer (LbL) assembly of oppositely charged reduced graphene oxides (RGOs). The graphene thin films showed remarkable optical–electronic properties. Inspired by this, we further fabricated transparent conductive hybrid thin film via LbL assembly of oppositely charged RGO nanosheets and Pt nanoparticles. The graphene–Pt hybrid thin film showed transient optical property as well as appropriate conductive and wetting properties. Moreover, we demonstrated graphene wrapped-MnO₂ (GW-MnO₂) nanocomposites by self-assembly of honeycomb MnO₂ nanospheres and graphene sheets via an electrostatic co-precipitation method. The hybrid materials had a good electrochemical performance.

To gain an insight into earthquake slip weakening due to thermal pressurization, microscopic molecular structures associated with water desorption are investigated for layered-hectorite nanoparticles by positronium (Ps) annihilation spectroscopy, thermogravimetry and differential thermal analysis (TG–DTA) and time-resolved length-change measurement with high resolution dilatometry. The large macroscopic length change of ~ 6% occurs simultaneously with the formation of open spaces with the size of ~ 7 Å when water molecules are desorbed from the interlayer spaces.

Adsorption behavior of cesium (Cs) into angstrom-scale open spaces for the saponite clay mineral is investigated by making use of positronium (Ps) annihilation spectroscopy together with thermogravimetry and differential thermal analysis (TG–DTA). Ps annihilation spectroscopy reveals two kinds of open spaces with their sizes of ~ 3 Å and ~ 10 Å, respectively, after baking at 423 K for 8 h under the vacuum condition at ~ 10^-5 Torr. The large open space is found to survive for the Cs-type saponite due to less hydration of the Cs cations even after the exposure to the air for 200 h. It is thus inferred that Cs is locally adsorbed in the angstrom-scale open spaces in the saponite clay minerals.

Nanocrystalline silicon embedded in silicon oxide (nc-Si/SiO₂) films have been in situ grown at a low substrate temperature of 300°C by reactive magnetron co-sputtering of Si and SiO₂ targets in a mixed Ar/H₂ discharge. The influences of H₂ flow rate (F_H) on the microstructural properties of the deposited nc-Si/SiO₂ films were investigated. The results of XRD and the deposition rate of nc-Si/SiO₂ films show that the introduction of H₂ contributes to the growth of nc-Si grains in silicon oxide matrix. With further increasing F_H, the average size of nc-Si grains increases and the deposition rate of nc-Si/SiO₂ films decreases gradually. Fourier transform infrared spectra analyses reveal that introduction of hydrogen contributes to the phase separation of nc-Si and SiO_x in the deposited films. Moreover, the Si–O_4-nSi_n(n = 0, 1) concentration of the deposited nc-Si/SiO₂ films reduces with the increase of F_H, while that of Si–O_4-nSi_n(n = 2, 3) concentration increases. These results can be explained by that active hydrogen atoms increase the probability of reducing oxygen from precursor in the plasma and prompting oxygen desorption from the growing surface. This low-temperature procedure for preparing nc-Si/SiO₂ films opens up the possibility of fabricating the silicon-based thin-film solar cells onto low-cost glass substrates using nc-Si/SiO₂ films.

Imidacloprid is a neonicotinoids insecticide, which is important for the cash crops such as tomato, rape and so on. The conventional formulation does not only increase the loss of pesticide but also leads to environmental pollution. Controlled-release formulations of pesticide are highly desirable not only for attaining the most effective utilization of the pesticide, but also for reducing environmental pollution. Pesticide imidacloprid was incorporated in poly (styrene–diacetone crylamide)-based formulation to obtain controlled release properties, and the imidacloprid nanocontrolled release formulation was characterized by infrared (IR) and field emission scanning electron microscope (FESEM). Factors related to loading efficiency, swelling and release behaviors of the formulation were investigated. It showed that the loading efficiency could reach about 40% (w/w). The values for the diffusion exponent "n" were in the range of 0.31–0.58, which indicated that the release of imidacloprid was diffusion-controlled. The time taken for 50% of the active ingredient to be released into water, T₅₀, was also calculated for the comparison of formulations in different conditions. The results showed that the formulation with higher temperature and more diacetone crylamide had lower value of T₅₀, which means a quicker release of the active ingredient. This study highlighted some pieces of evidence that improved pesticide incorporation and slower release were linked to potential interactions between the pesticide and the polymer.

The impact of the environmental factors on the emissions of particulate matter (PM) number, size distribution and mass size distribution from diesel passenger cars was evaluated. Particle measurements from five modern light-duty diesel vehicles (LDDV) were performed in June and November 2011. Commercial low sulfur diesel fuel (less than 50 ppm) was used during the testing of these vehicles which were not equipped with after-treatment devices. The dynamometer test was based on the Economic Commission of Europe (ECE) 15 cycles. The results indicate that PM_2.5 emissions from LDDV are significantly affected by ambient temperature and pressure. A comparison of the emissions concentration of PM_2.5 in these two different months showed that the number concentration in June was (3.8 ± 0.69) × 10⁷ cm^-3 and (2.5 ± 0.66) × 10⁷ cm^-3 in November. The PM concentration of about 30 nm diameter was 25 ± 6% of the total emissions in November while only 14 ± 3% of total emissions in June. In the 60 nm to 2.5 μm test range, November data shows less of a contribution for number than data from June testing. The concentration of mass emissions in June was (325 ± 44) mg/m³ and (92 ± 30) mg/m³ in November. The contribution of the number of PM particles in November testing is lower than testing in June by 34% and the mass concentration in November is 70% lower than that in June. With the decrease of ambient temperature and the increase of ambient pressure, both the oxygen concentration in cylinder and air–fuel ratio are increased, which caused lower particle number and mass emissions during November testing. The size distribution is also altered by these changes: the more efficient in-cylinder combustion resulted in a higher proportion of particles in the 30 nm and smaller range than for other particle sizes.

Fluorescent semiconductor nanocrystals have been widely used as fluorescent materials in chemical sensors, biotechnology, medical diagnostics, biological imaging and many other fields. Compared to the conventional organic fluorophores, the inorganic quantum dots (QDs) have many advantages, including broad absorption spectra, narrow emission spectra, good photostability and long fluorescent lifetime after excitation. Here, the high quality CdS QDs were synthesized directly from sulfur and CdO using the paraffin liquid as solvent and the oleic acid as the reacting media. The synthesized CdS QDs with a zinc blende (cubic) crystal structure were proved by X-ray diffraction. HRTEM observation revealed that the CdS QDs were uniform and the average grain size was about 4 nm. The optical properties of the CdS QDs were characterized by using photoluminescence (PL) spectrophotometer and Ultraviolet-visible (UV-Vis) absorption spectrophotometer. The formation mechanism of CdS QDs in the paraffin liquid and oleic acid system was proposed.

Nanosize barium sulfate (BaSO₄) particles prepared with dodecyl benzene sulfonic acid (DBSA) in ethanol–water reaction system are used to prepare BaSO₄/polypropylene (PP) nanocomposites by melt mixing method. It is then made into hybrid fibers by melt spinning and subsequent drawing with different ratios. The hybrid fibers are characterized by rheology, morphology, thermal stability and mechanical properties, respectively. The results indicate that the DBSA-modified BaSO₄ can improve the spinnability of BaSO₄/PP hybrid multifilament even at high BaSO₄ nanoparticles concentration. DBSA can be used as compatibilizer to enhance the interface interaction of BaSO₄/PP nanocomposites, because DBSA contains both hydrophobicity long alkyl chain and hydrophilic sulfonic group. Therefore, it can improve the performances of BaSO₄/PP hybrid multifilament.

Production of nanoparticles by precipitation is a relatively simple process but the control of product particle size distribution is difficult. In this paper, nanosize barium sulfate (BaSO₄) particles are prepared with dodecyl benzene sulfonic acid (DBSA) in ethanol–water reaction system at room temperature. The BaSO₄ nanoparticles are characterized by scanning electron microscopy (SEM), transmission electron microscope (TEM), powder X-ray diffraction (XRD), dynamic light scattering (DLS), Fourier transform infrared spectroscopy (FT-IR) and thermo gravimetric analysis (TGA), respectively. The results indicated that the average diameter of spherical BaSO₄ is about 46 nm modified with 5 wt.% DBSA, which have good dispersion in the presence of a certain concentration NH₃ ⋅ H₂O. It suggests that the high dispersion is attributed to presence of a thin layer of barium alkyl sulfate, which is formed and coated onto the surface of BaSO₄ particles during the reaction process. The thin films on the surface of the BaSO₄ effectively modified the surface and properties, which also control the particle size and morphology.

Lead sulfide (PbS) quantum dots (QDs) capped with oleic acid and oleic amine were synthesized by using safe and innocuous sulfur powder as S source instead of the bis (trimethylsilyl) sulfide ((TMS)₂S). QDs with size distribution from 20 nm to 3 nm were gained by controlling the experiment parameters such as heating temperature, capping agents and the growth time. The morphology and crystal structure of the as-prepared PbS QDs were characterized by (high-resolution) transmission electron microscopy (HR-TEM) images and powder X-ray diffraction (XRD). This method may offer a new route to synthesize PbS QDs for photovoltaic devices.

Biopolymer chitosan templated bimodal porous silica materials with uniform macroporosity and narrowed mesopore size distribution were synthesized via fast precipitation of chitosan–silica hybrid composites (Chi/SiO₂). Clear Chi/SiO₂ solutions containing the biopolymer chitosan and siloxane-based inorganic network were prepared by hydrolysis of sodium metasilicate in the presence of biopolymer chitosan. The relative amount of chitosan in as-made Chi/SiO₂ was analyzed by thermogravimetric analysis (TGA). Chi/SiO₂ was calcined at 600°C for 5 h in the presence air to remove chitosan, and characterized by scanning electron microscope (SEM), transmission electron microscope (TEM) and N₂ adsorption–desorption isotherms. These porous silica products had high specific surface area of 500–550 m²/g, narrow pore size distribution and also bicontinuous macropore structure.

Electro-hydraulic power impulse water jets can convert the shock wave generated in the liquid by discharging into mechanical energy, and it has been widely used in material forming, surface cleaning, pipeline dirt cleaning and ore breaking process. Compared with the traditional high pressure water jets, the energy utilization of electro-hydraulic power impulse water jets is up to 80% while the water consumption is reduced by 40–55%. This paper has taken electro-hydraulic power impulse water jets as the research object, employed obtaining the maximum pressure of compression impulse matrix surface as the research goal, studied in depth the equivalent discharge circuit, characteristic equation and the relationship between the electrical parameters of the electro-hydraulic power impulse discharge circuit and built the calculation method of the voltage, the inductance, the capacitance and the electrode spacing parameter of electro-hydraulic power impulse water jets discharge circuit. So, it will provide important theoretical basis for further studies of electro-hydraulic power impulse technology and the existing water jets device.

Thermodynamically stable molybdenum trioxide nanorods have been successfully synthesized by a simple hydrothermal process. The product exhibits high-quality, single-crystalline layered orthorhombic structure (α-MoO₃), and aspect ratio over 20 by characterizations of X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HR-TEM) and Fourier transform infrared (FT-IR). The growth mechanism of α-MoO₃ nanorods can be understood by electroneutral and dehydration reaction, which is highly dependent on solution acidity and hydrothermal temperature. The sensing tests show that the sensor based on MoO₃ nanorods exhibits high sensitivity to NO₂ and is not interferred by CO and CH₄, which makes this kind sensor a competitive candidate for NO₂ detection. The intrinsic sensing performance of MoO₃ maybe arise from its nonstoichiometry of MoO₃ owing to the presence of Mo⁵⁺ and oxygen vacancy in MoO₃ lattice, which has been confirmed by X-ray photoelectron spectroscopy (XPS) analysis. The sensing mechanism of MoO₃ for NO₂ is also discussed.