表面活性剂对纳米氧化锌粒径和形貌的影响研究

以尿素和硝酸锌为原料,采用均匀沉淀法制备纳米氧化锌(ZnO),加入不同的表面活性剂以及同种表面活性剂不同剂量对纳米ZnO的粒径和形貌有不同的影响.实验结果表明:在液相法制备纳米ZnO时,复合型表面活性剂以及阴离子型表面活性剂的分散性能优于非离子表面活性剂.添加浓度为3.2×10-3 mol/L的表面活性剂十二烷基苯磺酸钠时,沉淀物的分散活性好,能够较好的控制ZnO的粒度;油酸钠和聚乙二醇1000复合型表面活性剂浓度分别为1.0×10-4 mol/L和1.6×10-3 mol/L时,分散效果最好,能制得粒径为10～50 nm的纳米ZnO.     

Electrochemiluminescent metallopolymer-nanoparticle composites: nanoparticle size effects

Metallopolymer-gold nanocomposites have been synthesized in which the metal complex-Au nanoparticle (NP) mole ratio is systematically varied by mixing solutions of 4-(dimethylamino) pyridine protected gold nanoparticles and a [Ru(bpy)(2)PVP(10)](2+) metallopolymer; bpy is 2,2'-bipyridyl and PVP is poly-(4-vinylpyridine). The impact of changing the gold nanoparticle diameter ranging from 4.0 ± 0.5 to 12.5 ± 1 nm has been investigated. The photo induced emission of the metallopolymer undergoes static quenching by the metal nanoparticles irrespective of their size. When the volume ratio of Au NP-Ru is 1, the quenching efficiency increases from 38% to 93% on going from 4.0 ± 0.5 to 12.5 ± 1 nm diameter nanoparticles while the radius of the quenching sphere remains unaffected at 75 ± 5 ?. The conductivity of thin films is initially unaffected by nanoparticle incorporation until a percolation threshold is reached at a mole ratio of 4.95 × 10(-2) after which the conductivity increases before reaching a maximum. For thin films of the nanocomposites on electrodes, the electrochemiluminescence intensity of the nanocomposite initially increases as nanoparticles are added before decreasing for the highest loadings. The electrochemiluminescence intensity increases with increasing nanoparticle diameter. The electrochemiluminescence (ECL) emission intensity of the nanocomposite formed using 12.5 nm particles at mole ratios between 5 × 10(-3) and 10 × 10(-3) is approximately 7-fold higher than that found for the parent metallopolymer. The application of these materials for low cost ECL-based point of care devices is discussed.     

Effect of nanoparticle size on the onset temperature of surface melting

In this letter the onset temperature of surface premelting, T_sm, is determined in terms of the mean-field approximation. There are established relationships, describing the dependence of T_sm on a characteristic size of nanoparticles. It is shown that if a radius of a particle, r, exceeds 10 nm approximately, this dependence is weak. On the contrary, it is strong if the radius of a particle is less than 5 nm. The transition of surface layers into the quasi-liquid and pseudo-crystalline states is under consideration, too. A comparison of the proposed model with available experimental data and with molecular dynamics simulations is carried out.     

Metal oxide nanoparticle mediated enhanced Raman scattering and its use in direct monitoring of interfacial chemical reactions

Metal oxide nanoparticles (MONPs) have widespread usage across many disciplines, but monitoring molecular processes at their surfaces in situ has not been possible. Here we demonstrate that MONPs give highly enhanced (×10(4)) Raman scattering signals from molecules at the interface permitting direct monitoring of their reactions, when placed on top of flat metallic surfaces. Experiments with different metal oxide materials and molecules indicate that the enhancement is generic and operates at the single nanoparticle level. Simulations confirm that the amplification is principally electromagnetic and is a result of optical modulation of the underlying plasmonic metallic surface by MONPs, which act as scattering antennae and couple light into the confined region sandwiched by the underlying surface. Because of additional functionalities of metal oxides as magnetic, photoelectrochemical and catalytic materials, enhanced Raman scattering mediated by MONPs opens up significant opportunities in fundamental science, allowing direct tracking and understanding of application-specific transformations at such interfaces. We show a first example by monitoring the MONP-assisted photocatalytic decomposition reaction of an organic dye by individual nanoparticles.     

One step production of magnetic nanoparticle films by laser pyrolysis inside a chemical vapour deposition reactor

Deposition of nanoparticulated films onto glass has been achieved by using an unprecedented combination of laser pyrolysis and chemical vapour deposition (CVD) on a single step process. Characterisation of the films reveals that the coated glasses obtained by this technique have similar characteristics to the ones previously fabricated using a two step pyrolysis plus CVD process. Under the laser action, maghemite or hematite nanoparticulated coatings are obtained by varying the processing conditions. We envisage the incorporation of this one step process for industrial production, where the nanoparticulated film would be deposited as the glass moves along the production line.     

表面效应对动态光散射纳米粒径测量的影响

为探究表面效应对动态光散射法测量纳米粒度的影响,设计一种宽度可调的样品池,采用基于高速线阵CCD的动态光散射测量系统,对不同粒径的标准SiO_2颗粒进行测量。结果表明:样品池宽度小于1.3 mm时,粒径测量值随通道宽度减小线性增大,宽度为0.6 mm时,粒径测量值与自由空间中的测量值差距超过5%;样品池宽度较小时,颗粒布朗运动受到明显影响,动态光散射仪中使用微量样品池时,应根据样品池宽度对测量结果进行修正。     

Influence of radiation on the limits of heterogeneous combustion of a particle in two parallel reactions on its surface

The influence of radiation on critical parameters of heterogeneous ignition and extinction of a carbon particle in air is analyzed with allowance for two heterogeneous reactions.Notation Q _chem surface power of heat release through chemical reactions, W/m² - Q _h overall density of heat flux by molecular convectionQ _m.c. and radiationQ _i, W/m² - d particle diameter, m - t time, sec - T ₁,T ₂,T ₂,T _w particle gas, and reaction chamber wall temperature respectively, K - ₁, ₂ particle and gas density, kg/m³ - c ₁,c ₂ specific heat of particle and gas, J/(kg·K) - n _ox relative mass concentration of oxidant in the gaseous medium - q _i thermal effect of the first (i=1, C+O₂=CO₂) and the second (i=2, 2C+O₂=2CO) chemical reactions, J/kg - _i stoichiometric coefficient - E activation energy, J/mole - k _0i preexponential factor, m/sec - R universal gas constant, J/(mole·K) - Nu Nusselt number - ₂ thermal conductivity coefficient of gas, W/(m·K) - D ₂ diffusion coefficient of gas, m²/sec - ₂₀, ₂₀,D ₀ density, thermal conductivity, and diffusion coefficients of gas atT ₀ - emissivity coefficient - Stefan-Boltzmann constant, W/(m²·K⁴) - , heat- and mass-transfer coefficients, W/(m²·K), m/sec. Indexes: 1, particle - 2 gas - ign ignition - ext extinction - w wall - st steady - cr critical - in initial - c combustion - m maximum - lim limiting I. I. Mechnikov Odessa State University. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 68, No. 3, pp. 466–473, 1995.     

Measurement of urine crystallites and its influencing factors by nanoparticle size analyzer

The difference of urine crystallites under 1000 nm in 10 patients with urolithiasis and 10 healthy subjects with no history of urolithiasis was comparatively studied with the nanoparticle size analyzer. By comparing the differences of intensity-autocorrelation curve, polydispersity index (PDI), Zeta potential, and relative error of average diameter of the two kinds of urine crystallites, it was concluded that the urine crystallites of healthy subjects were more stable than those of patients. The urine crystallites of healthy subjects had a narrower size distribution from 100 nm to 350 nm and a better dispersion (PDI < 0.3). However, the urine crystallites of patients with urolithiasis had a wider distribution from dozens of nanometers to 1000 nm and a worse dispersion (PDI > 0.5). The best processing method for urine crystallites detection was found: after antisepticising and protein-coagulating with formaldehyde, the urine was diluted with distilled water of the same volume, then filtrated through a micropore film of 3 microm, and the filtrate was centrifugalized at 4000 rpm for 15 minutes. This method can remove the cell fragments and macromolecular substances in the urine without affecting the detection of the urine crystallites under 1000 nm. The results were consistent with those obtained by transmission electron microscope (TEM).     

Label-free biosensing by surface plasmon resonance of nanoparticles on glass: optimization of nanoparticle size

The unique optical properties of noble metal nanoparticles have been used to design a label-free biosensor in a chip format. In this paper, we demonstrate that the size of gold nanoparticles significantly affects the sensitivity of the biosensor. Gold nanoparticles with diameters in the range of 12-48 nm were synthesized in solution and sensor chips were fabricated by chemisorption of these nanoparticles on amine-functionalized glass. Sensors fabricated from 39-nm-diameter gold nanoparticles exhibited maximum sensitivity to the change of the bulk refractive index and the largest "analytical volume", defined as the region around the nanoparticle within which a change in refractive index causes a change in the optical properties of the immobilized nanoparticles. The detection limit for streptavidin-biotin binding of a sensor fabricated from 39-nm-diameter nanoparticles was 20-fold better than a previously reported sensor fabricated from 13-nm-diameter gold nanoparticles. We also discuss several other factors that could improve the performance of the next generation of these immobilized metal nanoparticle sensors.     

Influence of Cu nanoparticle size on the photo-electrochemical response from Cu-multiwall carbon nanotube composites

We show that Cu metal nanoparticle-multiwall carbon nanotube (MWCNT) assemblies can act as a new hybrid photoactive layer in photo-electrochemical devices. The carbon nanotube (CNT) composites were formed by a controlled thermal deposition of copper which produced crystalline metal nanoparticles localized on the carbon tube outer walls. The photoresponse evaluated in terms of IPCE (incident photon-to-charge carrier generation efficiency) varied for different sized-Cu-MWCNT samples across all the visible and near ultraviolet photon energy range with respect to the response of bare MWCNTs. In the case of 0.2 nm Cu nominal thickness, the IPCE increased, reaching 15%, a value 2.5 times higher than that measured for bare MWCNTs. As the Cu nominal coverage thickened, the IPCE started to decrease and become totally ineffective after 1 nm deposited Cu. The IPCE increase found was interpreted as being the result of a remarkable charge transfer between the Cu metal nanoparticles and the CNTs due to the formation of a strong ionic bond at their interface. The results obtained prove that the metal nanoparticle-CNT composites have optical, electrical and structural properties that can be applied in a variety of nanoscale architectures for novel photo-electrochemical devices.     

Size and surface effects on the MRI relaxivity of manganese ferrite nanoparticle contrast agents

Superparamagnetic MnFe2O4 nanocrystals of different sizes were synthesized in high-boiling ether solvent and transferred into water using three different approaches. First, we applied a ligand exchange in order to form a water soluble polymer shell. Second, the particles were embedded into an amphiphilic polymer shell. Third, the nanoparticles were embedded into large micelles formed by lipids. Although all approaches lead to effective negative contrast enhancement, we observed significant differences concerning the magnitude of this effect. The transverse relaxivity, in particular r2*, is greatly higher for the micellar system compared to the polymer-coated particles using same-sized nanoparticles. We also observed an increase in transverse relaxivities with increasing particle size for the polymer-coated nanocrystals. The results are qualitatively compared with theoretical models describing the dependence of relaxivity on the size of magnetic spheres.     

Influence of a new chemical crosslink system on the morphology and crystallite size of nylon-12

Special polyamide chains of desirable structure were polymerized such that they already contained reactive sites at the chain ends. The degree of crosslinking is determined by the chain structure and the amount of a specific epoxide silane, which causes crosslinking by formation of condensed silicon centres. The influence of the chain structure and the amount of epoxide silane on the morphology and the crystallite size were investigated by transmission electron microscopy using electron spectroscopic imaging and differential scanning calorimetry. A three-component structure was observed, consisting of crystalline and amorphous regions with a transition region between them. The lamellar thickness of the crystallites (5–7 nm) was independent of the chain structure and of the amount of epoxide silane, i.e. independent of the degree of crosslinking. Conversely, the lamellar length of the crystallites was dependent on the chain structure. For the material containing linear chains it was usually greater than 100 nm; for the material containing highly branched chains it varied from about 100 nm down to a block-like structure. The width of the transition region, in which the chains are under stress, was about 2 nm. The condensed silicon centres (crosslink points) were randomly distributed with respect to the resolution of the transmission electron microscope. RuO₄ is a good staining agent for nylon-12.     

Utilizing the thermodynamic nanoparticle size effects for low temperature Pb-free solder

Development of a Pb-free Sn nanosolder paste with an initial melting temperature near or below the melting temperature of eutectic Sn-Pb solder (183 °C) has been investigated using the size-dependent melting behavior of small particles. Three to five nanometer Sn nanoparticles were fabricated by sonochemical reduction and observed to melt at temperatures near or below 183 °C. Prototype nanosolder pastes were produced by combining the nanoparticles with flux and were characterized by differential scanning calorimetry (DSC) in terms of their melting, solidification, coalescence, and metal particle loading properties. The results indicate that, although target melting temperatures were achieved, nanoparticle coalescence was limited by low volume loading of the metal, due in part to the capping layer (an organic layer adsorbed on the metal surface during chemical synthesis).     

Influence of size effects on the nucleation processes in a condensed phase

Some problems related to the influence of size effects on the nucleation processes in nanoparticles have been investigated theoretically.     

Influence of nanoparticle size to the electrical properties of naphthalenediimide on single-walled carbon nanotube wiring

Nanoparticles of N,N'-bis(n-alkyl)tetracarbonatenaphthalenediimide (NDI) were adsorbed on single-walled carbon nanotube (SWNT) wires dispersed on a SiO(2) substrate. The electrical properties were measured along the long axis of the SWNTs, and in all cases through the nanoparticles showed rectification in semiconducting I-V curve. The plateau width of the I-V curve through the NDI nanoparticles on metallic SWNTs decreased as the particle size increased, while the rectification ratio increased. The conduction mechanism was changed from tunneling conduction to Schottky-like conduction and their boundary is at about 3 nm diameter.     

Influence of size effects on gas absorption by nanoparticles

The influence of size effects on gas absorption by small aerosol particles is studied theoretically. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 81, No. 5, pp. 944–947, September–October, 2008.     

Direct observation of chemical reactions on single gold nanocrystals using surface plasmon spectroscopy

Heterogeneous catalysts have been pivotal to the development of the modern chemical industry and are essential for catalysing many industrial reactions. However, reaction rates are different for every individual catalyst particle and depend upon each particle's morphology and size, crystal structure and composition. Measuring the rates of reaction on single nanocrystals will enable the role of catalyst structure to be quantified. Here, using surface plasmon spectroscopy, we have directly observed the kinetics of atomic deposition onto a single gold nanocrystal and also monitored electron injection and extraction during a redox reaction involving the oxidation of ascorbic acid on a gold nanocrystal surface. These results constitute the first direct measurement of the rates of redox catalysis on single nanocrystals.     

Reaction inside a viral protein nanocage: Mineralization on a nanoparticle seed after encapsulation via self-assembly

Protein nanocages are ideal templates for the bio-inspired fabrication of nanomaterials due to several advantageous properties.During the mineralization of nanoparticles (NPs) inside protein nanocages,most studies have employed a common strategy:seed formation inside protein nanocages followed by seeded NP growth.However,the seed formation step is restricted to gentle reaction conditions to avoid damage to the protein nanocages,which may greatly limit the spectrum of seed materials used for NP growth.We put forward a simple route to circumvent such a limitation:encapsulation of a preformed NP as the seed via self-assembly,followed by the growth of an outer metal layer.Using such a method,we succeeded in mineralizing size-tunable Au NPs and Au@Ag core-shell NPs (＜10 nm in diameter) with narrow size distributions inside the virus-based NPs of simian virus 40.The present route enables the utilization of NPs synthesized under any conditions as the starting seeds for nanomaterial growth inside protein nanocages.Therefore,it potentially leads to novel bioinorganic chimeric nanomaterials with tailorable components and structures.     

Influence of size effects on the critical diameter and growth of nanoparticles

The effect exerted by the dependence between the condensation and surface-tension coefficients and the size of an aerosol nanoparticle on its growth and critical diameter is investigated theoretically. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 79, No. 2, pp. 14–18, March–April, 2006.     

Effect of particle size on iron nanoparticle oxidation state

Selecting catalyst particles is a very important part of carbon nanotube growth, although the properties of these nanoscale particles are unclear. In this article iron nanoparticles are analyzed through the use of atomic force microscopy and x-ray photoelectron spectroscopy in order to understand how the size affects the chemical composition of nanoparticles and thus their physical structure. Initially, atomic force microscopy was used to confirm the presence of iron particles, and to determine the average size of the particles. Next an analytical model was developed to estimate particle size as a function of deposition time using inputs from atomic force microscopy measurement. X-ray photoelectron spectroscopy analysis was then performed with a focus on the spectra relating to the 2p Fe electrons to study the chemical state of the particles as a function of time. It was shown that as the size of nanoparticles decreased, the oxidation state of the particles changed due to a high proportion of atoms on the surface.