Surface coating of Al nanoparticles by using a wet ball milling method: A facile synthesis and characterization of colloidal stability

A facile surface coating of aluminum (Al) nanoparticles with various dispersants by using a wet ball milling method is reported. Various mixtures of Al nanoparticles (d = 30–130 nm) and dispersants in solvent were ball milled. The excellent surface coating was observed with coating thickness ranging from 10 to 13 nm. The resulting good colloidal stability confirmed by both visual inspection of colloidal precipitation and Turbiscan backscattering was attributed to a stable dispersant organic layer formed on Al nanoparticle surfaces after ball milling as observed in HRTEM images. This method can be extended to the synthesis of a variety of any other metallic nano-colloidal solutions.     

悬浮液进样端视电感耦合等离子体发射光谱法直接测定二氧化钛中铌

用聚丙烯酸胺(NH₄PAA)为分散剂制备二氧化钛悬浮液,并以悬浮液进样端视电感耦合等离子体发射光谱法直接测定了二氧化钛中痕量杂质铌。研究了分散剂及分散剂的量和pH对二氧化钛悬浮液稳定性的影响,通过优化条件制备得到稳定和均匀的悬浮液。研究了端视电感耦合等离子体发射光谱分析悬浮液进样的性能。本方法的检出限为3.0 μg·L-1, 相对标准偏差为3.1%(n=3, c=0.3 mg·L-1)。     

Characterization of luminescent chromophore obtained from silica spheres

Blue light emitting chromophores have been separated from silica spheres by soaking them into acetone for 120 days. The luminescent chromophores were not obtained from other solvents, including ether, methanol, ethanol, 2-propanol, chloroform and tetrahydrofuran. According to the Fourier transform infrared spectrum, the luminescent material is composed of C–OH, –CH₂, –CH₃, C=O, and Si–O–Si. UV–visible absorption peak of the chromophore is at 5.17 eV (240 nm). Field emission scanning electron microscope images show small cracks on the surface of aged spheres. The luminescence peak was at 2.81 eV (441 nm) for excitation energy between 3.88 and 3.35 eV and slightly shifted toward lower energy for excitation energy lower than 3.35 eV. The deconvoluted luminescent spectrum shows two emission bands at 3.08 and 2.74 eV, which are well-matched the oxygen deficient center model. Compared to the absorption peak (5.17 eV) and the emission peak (2.81 eV), large Stokes shift (2.36 eV) is observed.     

四（3,4-亚甲二氧基苯基）卟啉的合成及光谱分析

研究了以3,4-亚甲二氧基苯甲醛和吡咯为原料合成四（3,4-亚甲二氧基苯基）卟啉的方法,探索了溶剂、催化剂等反应条件对合成的影响。新化合物结构分别被UV-Vis,IR,1H NMR及元素分析所证实。利用紫外-可见分光光度法和荧光光谱法研究了四（3,4-亚甲二氧基苯基）卟啉在四氢呋喃（THF）、丙酮、氯仿、N,N-二甲基甲酰胺（DMF）4种溶剂中的光谱性质。     

Analysis of Anionic Polymer Dispersant Behavior in Dense Silicon Nitride and Carbide Suspensions Using an AFM

The paper focuses on the interaction mechanism caused by anionic polymer dispersants in dense silicon nitride and silicon carbide suspensions. An atomic force microscope (AFM) was used to determine the relationship between the macroscopic suspension viscosity and the microscopic structure adsorbing of a polymer dispersant at the solid/liquid interface. The surface interactions within the suspensions were analyzed under various dispersant pH values and additive conditions. The addition of an anionic polymer dispersant decreased the viscosity of silicon nitride and silicon carbide suspension and increased the electrosteric repulsive force on the non-oxide surface in solution at pH > 6, which was the isoelectric point of the materials. Based on the above results, we estimated the adsorption mechanism of anionic polymer dispersants on each solid surface in solution under relatively high pH conditions.     

Study on ultrasound-assisted liquid-phase exfoliation for preparing graphene-like molybdenum disulfide nanosheets

Nanomaterials with graphene-like structures have many excellent properties different from bulk materials and have become one of the most popular international frontiers in recent years. In this paper, graphene-like molybdenum disulfide materials are prepared by ultrasonic exfoliation method assisted with 1-Dodecanethiol. Double solvent ultrasonic exfoliation is realized by introducing chloroform. In addition, the optimal preparation conditions for the preparation of graphene-based molybdenum disulfide are investigated from the aspects of ultrasonic processing time and volume ratio of 1-Dodecanethiol and chloroform. Ultrasonic cleaning instrument is used in the experiment, it’s type is KQ3200E (40KHz, 150 W). Results show that the prepared graphene-like molybdenum disulfide has the highest concentration when the volume ratios of 1-Dodecanethiol and chloroform is 1:1 and ultrasonic processing time is 12 h. The dispersion of graphene-like molybdenum disulfide in low-boiling organic solvents, such as chloroform, tetrahydrofuran (THF), isopropanol (IPA), acetone, acetonitrile (CH₃CN) and ethanol, is realized by solvent exchange method. Characterized by transmission electron microscopy, a relatively thin sheet material is obtained. In addition, the latest methods for preparing graphene-like molybdenum disulfide nanosheet are discussed in view of micromechanical exfoliation, lithium ion intercalation, chemical vapor deposition and chemical synthesis, the advantages and limitations of various preparation methods are compared, the applications of graphene-like molybdenum disulfide nanosheets are also investigated.     

Electrospun cross linked rosin fibers

In this study, we describe the first reported preparation of rosin in fiber form through use of an electrospinning technique utilizing various solvent systems. The polymer concentration of the formed fiber was studied by using various solvents such as chloroform, ethanol, N-N dimethylformamide (DMF), tetrahydrofuran (THF), acetone, and methylene chloride (MC). An electrospray of the solution resulted in the beaded form of the rosin. By varying the polymer concentration with MC, we were then able to obtain uniform fibers. However, the fibers exhibited large diameter. We believe that it is possible to reduce the diameter of the rosin fibers through appropriate selection of electrospinning parameters. In addition, the morphological transitions from beads, to beaded fiber, to fiber were studied at different polymer concentrations. We propose a possible physical cross linking mechanism for the formation of rosin fibers during the electrospinning process. Our results demonstrate the feasibility of producing fiber nanostructures of rosin by using an electrospinning technique.     

An Electroacoustic Investigation of Concentrated Aqueous Suspensions of Calcium Pyrophosphate

The zeta potential of concentrated suspensions of calcium pyrophosphate were investigated using electroacoustics. The particles were negatively charged over the entire pH range studied. It proved impossible to reduce the pH of the suspension below 1.8, but the iso electric point could be estimated to occur at approximately pH 1. Two commercially available dispersants (one cationic and one anionic) were then added in small increments to the suspension in order to follow the change in zeta potential as the dispersants adsorbed onto the particles. From the shape of the curve it was possible to estimate the optimum adsorbed amount of dispersant required to fully coat the particles. The cationic dispersant adsorbed strongly and the optimum dosage was estimated at 2.5 ml of active polymer/kg of powder. Anionic dispersants are known to adsorb onto negatively charged ceramic oxide particles, but the anionic dispersant used in this study did not adsorb onto the negatively charged calcium pyrophosphate particles.     

Viscosity and dispersion state of magnetic suspensions

We investigate the viscosity behavior of a magnetic suspension in which magnetic particles are dispersed in a mixture of polyacrylic liquids. The size of magnetite particles is nearly 300 nm and the volume fraction of the magnetic particles is in the range of 0.003-0.03. The particle concentration dependence of the suspension viscosity yields the intrinsic viscosity [η], which varies from 25.6 at 5 s⁻¹ to 5.1 at 400 s⁻¹. The yield stress and the infinite shear viscosity of the suspension increase non-linearly as the particle concentration ? increases. We examine the effect of process conditions such as milling time and amount of dispersant on the viscosity behavior of the suspension. As milling time elapses, yield stress and low shear viscosity decrease and then reach constant values while the infinite shear viscosity remains constant. When oleic acid is added as a dispersant, the yield stress and low shear viscosity of the suspension show minimum values as the amount of oleic acid increases. These results agree with experimental results of sedimentation tests, which enable us to estimate the aggregate size of magnetic suspension. The yield stress and the low shear viscosity of the magnetic suspension are found to be useful in evaluating the dispersion state of the magnetic suspension.     

Characteristic of nanoparticles generated from different nano-powders by using different dispersion methods

A standard rotating drum with a modified sampling train (RD), a vortex shaker (VS), and a SSPD (small-scale powder disperser) were used to investigate the emission characteristics of nano-powders, including nano-titanium dioxide (nano-TiO₂, primary diameter: 21 nm), nano-zinc oxide (nano-ZnO, primary diameter: 30–50 nm), and nano-silicon dioxide (nano-SiO₂, primary diameter: 10–30 nm). A TSI SMPS (scanning mobility particle sizer), a TSI APS (aerodynamic particle sizer), and a MSP MOUDI (micro-orifice uniform deposit impactor) were used to measure the number and mass distributions of generated particles. Significant differences in specific number and mass concentration or distributions were found among different methods and nano-powders with the most specific number and mass concentration and the smallest particles being generated by the most energetic SSPD, followed by VS and RD. Near uni-modal number or mass distributions were observed for the SSPD while bi-modal number or mass distributions existed for nano-powders except nano-SiO₂ which also exhibited bimodal mass distributions. The 30-min average results showed that the mass median aerodynamic diameter (MMAD) and number median diameter (NMD) of the SSPD ranged 1.1–2.1 μm and 166–261 nm, respectively, for all three nano-powders, which were smaller than those of the VS (MMAD: 3.3–6.0 μm and NMD: 156–462 nm), and the RD (MMAD: 5.2–11.2 μm and NMD: 198–479 nm). For nano-particles (electric mobility diameter < 100 nm), specific mass concentrations were nearly negligible for all three nano-powders and test methods. Specific number concentrations of nano-particles were low for the RD tester but were elevated when more energetic VS and SSPD testers were used. The quantitative size and concentration data obtained in this study is useful to elucidate the field emission and personal exposure data in the future provided that particle loss in the generation system is carefully assessed.     

Characteristic stability of bare Au-water nanofluids fabricated by pulsed laser ablation in liquids

Gold nanoparticles (Au-NPs) suspended in water where the suspension is a kind of nanofluid, were produced by pulsed laser ablation in liquids. Under the laser irradiation conditions up to 18 h, the average size of the Au-NPs ranged from 7.1 to 12.1 nm while their size-distribution tended to become narrower with effects of laser-induced fragmentation. Interestingly, the nanofluid showed an outstanding colloidal stability even after 1 month although no dispersants were used. The characteristic stability of bare Au-NPs suspension in water was found to be due to a large negative zeta potential of Au-NPs in water. The thermal conductivity of the Au-NPs (0.018 vol%)/water suspension increased by 9.3±5.4% compared to that of pure water.     

Nano-porous indium oxide transistor sensor for the detection of ethanol vapours at room temperature

Porous indium oxide thin film prepared by the dip coating technique has been used in the construction of a field effect transistor. The coating solution was prepared from indium chloride precursor. The average particle size of the dip coated thin film was found to be 25 nm. Scanning electron microscopic images show the porous nature of the film, and the root mean square roughness of the film calculated using atomic force microscope was 24 nm. A transistor has been constructed by evaporating metal Aluminium as source and drain electrodes on the indium oxide active layer and employing the silicon substrate itself as a gate. The sensor response of the constructed transistor was tested with ethanol, ammonia and acetone vapours. The sensor showed good response to ethanol vapours even at 5-ppm level, and the time for response and recovery of the gas was nearly 1 min. Response to ammonia and acetone was comparatively poor. When the gate voltage was increased from 0 to 300 mV, a considerable increase in the source-drain current was observed. As the temperature of the sensing element increased, response to ethanol vapours also increased. There was nearly a linear variation in the transistor response for 100 ppm of ethanol vapours when the gate voltage was swept from 0 to 300 mV. The sensor response of the transistor increases with the gas concentration. The constructed transistor was found to be selectively sensitive to ethanol; therefore it can be implemented to work as a breath alcohol checker.     

Characterization of Nano-Structured Poly(D,L-lactic acid) Nonwoven Mats Obtained from Different Solutions by Electrospinning

Two different solvent mixtures, chloroform/dimethylformamide (DMF) and chloroform/ acetone, in 60/40 v/v concentrations, were used to electrospin poly(D,L-lactic acid) (PDLLA). The influence of solvent type, solution concentration, and processing conditions on the morphology and properties of the electrospun mats was studied. The nanofibers characterization was done by scanning electron microscopy (SEM), wide-angle X-ray diffraction (WAXD) and differential scanning calorimetry (DSC). The smallest nanofibers’ diameters from both mixtures were obtained from solutions with 5 wt%/v PDLLA concentration using a 1.0 kV/cm electrical field. In general the nanofibers from the chloroform/DMF mixture had smaller diameters than the nanofibers from the chloroform/acetone mixture. However, the latter ones were porous, while the nanofibers from the chloroform/DMF mixtures were not. All the PDLLA nanofibers, independent of solvent mixture, had a very low amount of crystallinity and were composed of very small and imperfect α and β crystals.     

MoS_2溶液的波长选择性光限幅效应研究

采用N,N-二甲基甲酰胺(DMF)和四氢呋喃(THF)为溶剂,用离散法制备二硫化钼(MoS2)悬浮溶液,并用开孔Z扫描方法研究其在可见和近红外区域的非线性光学特性.结果显示,在强激光照射下,MoS2(in THF)悬浮溶液在可见波段(530 nm)透过率增强为常光透过率的1.54倍,表现为饱和吸收;在近红外波段(790 nm)透过率减弱为常光透过率的0.6倍,表现为反饱和吸收,具有很好的波长选择性光限幅效应.而作为对比的MoS2(in DMF)悬浮溶液在全波段透过率降低,呈现反饱和吸收特性,波长选择性不明显.机理解释可能为饱和吸收和热效应导致的自衍射两种机制联合作用.     

Fabrication and characterization of GaP/polymer nanocomposites for advanced light emissive device structures

GaP nanoparticles have been prepared using white P and a mild aqueous synthesis at decreased temperature followed by ultrasonication and stored as the suspension in water–ethanol mixture. They were characterized by standard methods of X-ray diffraction, transmission electron microscopy, Raman light scattering, and photoluminescence. Properties of GaP nanoparticles were compared with industrial and specially grown perfect GaP single crystals. It was shown that the GaP nanoparticles in suspension are the most suitable for high quality GaP/polymers nanocomposites because only they are uniform with dimensions of about 10 nm which is optimal for appearance of the pronounced quantum confinement effect. Polyglycidyl methacrylate (PGMA), polyglycidyl methacrylate-co-polyoligoethyleneglycol methacrylate (PGMA-co-POEGMA), and biphenyl vinyl ether (BPVE) polymers were used to prepare GaP polymer nanocomposites. The thickness of the polymer nanocomposite film was about 250–300 nm defined from AFM scratch experiment. The resulting nanocomposites yielded a bright luminescence at room temperature in a broad band with the maximum ranging from 2.5 to 3.2 eV and showed pronounced quantum confinement effects and other interesting and important for application phenomena leading to dramatic 1 eV expansion of GaP luminescence to the UV spectral region.     

直接置换法制备包覆型纳米铜-银双金属粉末

 以AgNO₃为主盐，采用直接置换法初步制备了包覆型纳米铜-银双金属粉末，分析了工艺条件对包覆效果的影响，并用透射电子显微镜、X射线能量色散谱仪和X射线衍射仪进行了表征。实验结果表明：纳米铜-银双金属粉末为包覆型结构，平均粒径约70 nm，分散性较好，表面银的原子分数达到74.28%。在洗涤过程中加入一定量的保护剂，有效解决了纳米铜粉的氧化问题。     

Milling and dispersion of multi-walled carbon nanotubes in texanol

Rheological results were used to determine the optimum type of dispersant and its concentration for six commercial dispersants for the dispersion of multi-walled carbon nanotube (MWCNT) agglomerates in texanol. An unsaturated polycarboxylic acid copolymer (BYK P-104) exhibited the optimum performance with the lowest MWCNT slurry viscosity in texanol. The cutting and dispersion efficiencies of MWCNTs with 20 wt.% of BYK P-104 dispersant were compared using conventional ball milling and high energy milling, whereby the latter was found to be more effective. High energy milling for 2 h produced a large portion of MWCNT agglomerates smaller than 150 nm, showing a drastic increase in slurry viscosity due to the dispersion into individual CNTs. On the other hand, 120 h ball milling was required to achieve the agglomerate size of 300 nm with less viscosity increase upon milling. Decrease in the degree of MWCNT crystallinity was observed by both milling, even though 2 h high energy milling showed slightly less damage than 120 h ball milling based on XRD and Raman spectroscopy results.     

Nanosphere dispersion on a large glass substrate by low dose ion implantation for localized surface plasmon resonance

Dispersing nanospheres on a large glass substrate is the key to fabricate noble metal nanostructures for localized surface plasmon resonance through dispersed nanosphere lithography. This article reports that by modifying the glass surface with low dose ion implantation and successively dip coating the surface with poly(diallyldimethyl ammonium chloride) (PDDA), polystyrene or silica nanospheres can be dispersed on a large glass substrate. Investigation shows that several kinds of ions, such as silicon, boron, argon, and arsenic, can improve the nanosphere dispersion on glass, attributed to the ion bombardment-caused silicon increment. Ion implantation imposes no surface roughness or optical loss to the glass substrate, thus this method is suitable for localized surface plasmon resonance application. Experiments show silicon ion implantation can best disperse the nanospheres. For the gold nanostructures obtained by obliquely evaporating 30 nm of gold film onto the polystyrene nanospheres, which are dispersed on a silicon ion implanted glass substrate, a localized surface plasmon resonance sensitivity of 242 nm/RIU is achieved.     

Dispersion of multi-walled carbon nanotubes in biocompatible dispersants

Owing to their phenomenal electrical and mechanical properties, carbon nanotubes (CNT) have been an area of intense research since their discovery in 1991. Different applications for these nanoparticles have been proposed, among others, in electronics and optics but also in the medical field. In parallel, emerging studies have suggested potential toxic effects of CNT while others did not, generating some conflicting outcomes. These discrepancies could be, in part, due to different suspension approaches used and to the agglomeration state of CNT in solution. In this study, we described a standardized protocol to obtain stable CNT suspensions, using two biocompatible dispersants (Pluronic F108 and hydroxypropylcellulose) and to estimate the concentration of CNT in solution. CNT appear to be greatly individualized in these two dispersants with no detection of remaining bundles or agglomerates after sonication and centrifugation. Moreover, CNT remained perfectly dispersed when added to culture medium used for in vitro cell experiments. We also showed that Pluronic F108 is a better dispersant than hydroxypropylcellulose. In conclusion, we have developed a standardized protocol using biocompatible surfactants to obtain reproducible and stable multi-walled carbon nanotubes suspensions which can be used for in vitro or in vivo toxicological studies.