On total internal reflection investigation of nanoparticles by integrated micro-fluidic system

We report on a novel sensor for characterization of nanoparticles colloidal suspensions. We employ a diffraction grating under total internal reflection for investigation of nanodisperse fluids passing through an integrated microfluidic channel. Dispersions containing polymeric, metallic, and ferromagnetic nanoparticles are studied. Using this device, we can accurately determine in real-time the specific refractive index for the nanoparticle suspension and the nanoparticle concentration. The nanoparticle concentrations can be calculated with a resolution of 0.3-0.5 wt% for polymeric nanoparticles, 0.03-0.05 wt% for metallic nanoparticles, and 0.05-0.1 wt% for ferromagnetic nanoparticles. This translates to an effective refractive index that can be determined with an accuracy of 7 x 10(-4) for the polymeric and 2 x 10(-4) for the metallic and ferromagnetic dispersions.     

低折射率疏水SiO_2薄膜的制备和表征

为了制备低折射率疏水SiO_2薄膜,将正硅酸乙酯(TEOS)和二甲基二乙氧基硅烷(DDS)在碱性条件下共水解缩聚,再以六甲基二氮硅烷(HMDS)做进一步的改性,采用提拉浸渍工艺在玻璃基底上制备单层增透膜。通过对溶胶粘度随老化时间的变化规律及HMDS添加对薄膜接触角影响等的分析与研究,制备了接触角最大的低折射率薄膜;同时对薄膜的红外特性、透过率、折射率进行了表征。结果表明:TEOS和DDS共水解缩聚提高了膜层疏水性,经HMDS改性后,薄膜的接触角为149°,折射率为1.12。     

Combined electrochromic and plasmonic optical responses in conducting polymer/metal nanoparticle films

Poly(3,4-ethylenedioxithiophene)/poly(styrene sulphonate) (PEDOT/PSS) aqueous dispersions were mixed with aqueous gold nanoparticle and aqueous silver nanoparticle colloids. PEDOT/gold nanoparticles (Au NP) and PEDOT/silver nanoparticles (Ag NP) films were obtained by solvent casting the corresponding aqueous solutions. The nanocomposite films showed the optical characteristics associated with both the surface plasmon absorption resonance of the metal nanoparticles and the excitation of the bipolaron band of the conducting polymer. As an interesting application we demonstrate the use of metal nanoparticles to tune the color of PEDOT based electrochromic films from blue to violet in the case of Au NP or green in the case of Ag NP.     

Tailoring silver nanoparticle construction using dendrimer templated silica networks

We have examined the role of the internal environment of dendrimer templated silica networks in tailoring the construction of silver nanoparticle assemblies. Silica networks from which 3,5-dihydroxybenzyl alcohol based dendrimer templates have been completely removed, slowly wet with an aqueous solution of silver acetate. The latter then reacts with internal silica silanol groups, leading to chemisorption of silver ions, followed by the growth of silver oxide nanoparticles. Silica network constructed using generation 4 dendrimer contains residual dendrimer template, and mixes with aqueous silver acetate solution easily. Upon chemisorption, silver ions get photolytically reduced to silver metal under a stabilizing dendrimer environment, leading to the formation of silver metal nanoparticles.     

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.     

Effect of solvent refractive index on the surface plasmon resonance nanoparticle optical absorption

Optical properties of plasmon coupled silver and gold nanoparticles were studied as a function of the refractive index of the surrounding medium. Our studies confirmed that the effect of changes in the refractive index of the surrounding medium was more difficult to demonstrate from an experimental point of view, because of the very high susceptibility of nanoparticles to aggregate in aqueous and organic solvents. Whereas the position of the absorption bands of triiodide in these solvents shows a clear dependence on medium's refractive index, the surface plasmon band position of silver and gold nanoparticles do not exhibit the same dependence. This is attributed to a non-negligible interaction of these solvents with nanoparticle surfaces.     

水合氧化铁负载量对丙烯酸树脂基复合吸附剂的结构及除磷影响

为优化丙烯酸树脂基水合氧化铁(Hydrated ferric oxide,HFO)复合吸附剂的负载量,调节FeCl₃浓度制备出5种复合吸附剂(HFO负载量分别为5.3wt%、8.6wt%、12.1wt%、14.9wt%和18.5wt%,以Fe质量分数计),分析其结构性能,并考察D213-HFO复合吸附剂对磷的吸附等温线、吸附动力学、pH和共存离子影响及洗脱效果。结果表明,复合吸附剂负载HFO颗粒为纳米无定型HFO,在直径方向呈U型分布。此外,随HFO负载量增加,磷吸附容量先升高后下降,负载量为14.9wt%的复合吸附剂吸附容量最大(19.04 mg·g?1)。复合吸附剂吸附磷在240 min达到平衡,更符合准一级动力学模型(R2>0.99)。磷吸附最佳pH为6~8,当SO₄2?≥600 mg·L?1树脂对磷无吸附效果,而负载HFO吸附磷不受影响。在连续4个吸附-洗脱周期内,5wt%的NaOH和5wt%的NaCl溶液对磷的洗脱率均接近100%。实验表明,复合吸附剂的吸附容量随HFO负载量增加先升高后下降,而结构性能、吸附平衡时间、pH适应范围、共存离子影响及洗脱效果无显著差异。      

Preparation and properties of cross-linked zirconia nanoparticle films on polycarbonate

Highly-crystalline zirconia (ZrO₂) nanoparticle was functionalized with 3-(N-aminoethyl) aminopropyltrimethoxysilane (AAPTMS) and dispersed in water at primary particle size level under basic condition (pH 13-14). The aqueous ZrO₂ nanoparticle dispersion was cast on a polycarbonate substrate with 1,4-butanediol digylcidyl ether as a cross-linker. Nanoparticle films with as high as 81 wt.% of ZrO₂ were obtained through heating the cast dispersion at 120 °C, which are highly transparent. The refractive index ranges from 1.70 to 1.77 at wavelength of 632 nm with the decrease of the amount of AAPTMS attached to ZrO₂ nanoparticles. Nanoindentation tests show that the hardness of the film reaches 1.7 GPa. In addition, both punched tape abrasion and nanoscratch tests reveal that the films exhibit prominent scratch resistant performance.     

The systematic tunability of nanoparticle dimensions through the controlled loading of surface-deposited diblock copolymer micelles

The continuous tunability of iron oxide nanoparticle dimensions is demonstrated using the pH controlled loading of ferric nitrate from aqueous solution into polystyrene-block-polyacrylic acid reverse micelles deposited on a silicon substrate. Quasi-hexagonally ordered two-dimensional arrays of iron oxide nanoparticles with a systematic tunability of particle heights in the sub-10?nm regime and a constant periodicity are obtained and characterized with atomic force microscopy and x-ray photoelectron spectroscopy.     

减反射可见光与反射近红外线双功能镀膜玻璃

采用溶胶-凝胶工艺,用提拉法在光伏玻璃上制备了玻璃/TiO2-SiO2/SnO2∶F/SiO2减反射可见光与反射近红外双功能膜。用拟合方法研究了TiO2掺量对TiO2-SiO2膜层折射率的影响、以及溶胶中水含量对SiO2膜层折射率的影响;研究了快速热处理温度对SnO2∶F膜结构和方块电阻的影响,用紫外-可见光谱(UV-Vis)测试了膜层的透射率,用扫描电镜(SEM)观察了膜层的表面形貌。结果表明,TiO2掺量可以使TiO2-SiO2膜层的折射率在1.49~1.97之间变化,SiO2溶胶中的水含量能够在膜面上形成微孔,降低SiO2膜层的折射率。通过优化工艺,制备出了在可见光范围平均透过率约为96%、1120nm波长近红外起始反射的双功能复合膜。对得到的结果进行了讨论。     

Interferometric investigation and simulation of refractive index in glass matrixes containing nanoparticles of varying sizes

The relationship between refractive index and nanoparticle radii of cadmium selenide (CdSe) nanoparticles embedded within glass matrixes was investigated experimentally and by simulations. A homemade automated Michelson interferometer arrangement employing a rotating table and a He-Ne laser source at a wavelength of 632.8 nm determined the refractive index versus nanoparticle radii of embedded cadmium selenide (CdSe) nanoparticles. The refractive index was found to decrease linearly with nanoparticle radius increase. However, one sample showed a step increase in refractive index; on spectroscopic analysis, it was found that its resonant wavelength matched that of the He-Ne source wavelength. The simulations showed that two conditions caused the step increase in refractive index: low plasma frequency and matched sample and source resonances. This simple interferometer setup defines a new method of determining the radii of nanoparticles embedded in substrates and enables refractive index tailoring by modification of exact annealing conditions.     

Controlled Deposition of Silver Nanoparticles in Mesoporous Single‐ or Multilayer Thin Films: From Tuned Pore Filling to Selective Spatial Location of Nanometric Objects

Silver nanoparticle assemblies are embedded within mesoporous oxide thin films by an in situ mild reduction leading to nanoparticle–mesoporous oxide thin‐film composites (NP@MOTF). A quantitative method based on X‐ray reflectivity is developed and validated with energy dispersive spectroscopy in order to assess pore filling. The use of dilute formaldehyde solutions leads to control over the formation of silver nanoparticles within mesoporous titania films. Inclusion of silver nanoparticles in mesoporous silica requires more drastic conditions. This difference in reactivity can be exploited to selectively synthesize nanoparticles in a predetermined layer of a multilayered mesoporous stack leading to complex 1D‐ordered multilayers with precise spatial location of nanometric objects. The metal oxide nanocomposites synthesized have potential applications in catalysis, optical devices, surface‐enhanced Raman scattering, and metal enhancement fluorescence.     

Low refractive index silicon oxide coatings at room temperature using atmospheric-pressure very high-frequency plasma

Low refractive index silicon oxide films were deposited using atmospheric-pressure He/SiH₄/CO₂ plasma excited by a 150-MHz very high-frequency power. Significant increase in deposition rate at room temperature could prevent the formation of dense SiO₂ network, decreasing refractive index of the resulting film effectively. As a result, a silicon oxide film with the lowest refractive index, n = 1.24 at 632.8 nm, was obtained with a very high deposition rate of 235 nm/s. The reflectance and transmittance spectra showed that the low refractive index film functioned as a quarter-wave anti-reflection coating of a glass substrate.     

Cu纳米颗粒添加体的[BMIm]NTf_2离子液体法制备及其摩擦学性能

用离子液体法制备Cu纳米颗粒并将其用于摩擦学研究优于常用的方法,以往对此报道不多。通过微波辐射合成了1-丁基-3-甲基咪唑双三氟甲基磺酰亚胺{[BMIm]NTf2}离子液体,利用化学还原法分别在水溶液和[BMIm]NTf2中制备了Cu纳米颗粒,采用XRD,TEM,TG和DTA对其结构进行了表征;将2种纳米Cu颗粒溶于N68基础油中,采用四球摩擦磨损试验机对2种纳米Cu添加体的摩擦学性能进行了试验,并对磨痕表面进行了SEM分析。结果表明:[BMIm]NTf2离子液体中制备的Cu纳米颗粒为面心立方结构,粒径为3～25nm,能够显著改善N68基础油的抗磨减摩性能;与水溶液中制备的纳米Cu添加体相比,其摩擦系数下降了24.6%,钢球磨斑直径下降了18.8%,PB值提高了16.4%。     

Synthesis of silica-coated aqueous ferrofluids through ligand exchange with a new organosilica precursor

A new method for the production of aqueous dispersions of superparamagnetic iron oxide nanoparticles with applications in biomedicine is reported. The method is based on the use of a triethoxisilyl dodecanoic acid ligand that has been specially synthesized for this purpose. The nanoparticles were grown in organic medium using oleic acid as surfactant. Subsequently, oleic acid was exchanged for the alkoxysilane ligand, then hydrolysis was performed in a hydrocarbon solvent, and the nanoparticles were transferred into water. The organic and aqueous ferrofluids have been characterized and their magnetic properties have been determined. The resulting maghemite/silica nanoparticles were single core, and stable in aqueous suspension.     

Transmission of light through magnetic nanocavities

The transmission of light through a metallic film stack on a transparent substrate, perforated with a periodic array of cylindrical holes/nanocavities, is studied. The structure is fabricated by using self-assembled nanosphere lithography. Since one layer in the film stack is made of a ferromagnetic metal (iron), exposure of the structure to a solution containing iron oxide nanoparticles causes nanoparticle accumulation inside the nanocavities. This changes the dielectric constant inside the nanocavities and thus affects the light transmission. Simulations are in good agreement with experiment, and show large sensitivity of the response to the amount of iron oxide nanoparticles deposited. This could be used in various sensor applications.     

Transmission interference spectrometric determination of the thickness and refractive index of barrier films formed anodically on aluminum

Aluminum oxide films were formed anodically under carefully controlled conditions and prepared for transmission by dissolving part of the base metal in a solution containing iodine.A spectrophotometric technique to determine the refractive index of the anodic oxide is presented. This technique, based on the transmission interference spectra of two films with slightly different thicknesses, yielded precise results and enabled problems derived from the relatively low refractive index of alumina to be overcome. The film thickness was also calculated from the data, and the results indicated that the refractive index did not depend on the film thickness, at least for the range under study.The anodic alumina showed normal dispersion over the UV, visible and near- IR regions and its refractive index varied from 1.88 at 200 nm to 1.65 at 1300 nm.     

Green nanochemistry: metal oxide nanoparticles and porous thin films from bare metal powders

A universal, simple, robust, widely applicable and cost-effective aqueous process is described for a controlled oxidative dissolution process of micrometer-sized metal powders to form high-purity aqueous dispersions of colloidally stable 3-8 nm metal oxide nanoparticles. Their utilization for making single and multilayer optically transparent high-surface-area nanoporous films is demonstrated. This facile synthesis is anticipated to find numerous applications in materials science, engineering, and nanomedicine.     

Characterization of the biocompatible magnetic colloid on the basis of Fe3O4 nanoparticles coated with dextran, used as contrast agent in magnetic resonance imaging

The magnetic resonance imaging contrast agent, the so-called Endorem colloidal suspension on the basis of superparamagnetic iron oxide nanoparticles (mean diameter of 5.5 nm) coated with dextran, were characterized on the basis of several measurement techniques to determine the parameters of their most important physical and chemical properties. It is assumed that each nanoparticle is consisted of Fe3O4 monodomain and it was observed that its oxidation to gamma-Fe2O3 occurs at 253.1 degrees C. The M?ssbauer spectroscopy have shown a superparamagnetic behavior of the magnetic nanoparticles. The Magnetic Resonance results show an increase of the relaxation times T1, T2, and T2* with decreasing concentration of iron oxide nanoparticles. The relaxation effects of SPIONs contrast agents are influenced by their local concentration as well as the applied field strength and the environment in which these agents interact with surrounding protons. The proton relaxation rates presented a linear behavior with concentration. The measured values of thermo-optic coefficient dn/dT, thermal conductivity kappa, optical birefringence delta n0, nonlinear refractive index n2, nonlinear absorption beta' and third-order nonlinear susceptibility |chi(3)| are also reported.     

Electrospun polyvinylpyrrolidone fibers with high concentrations of ferromagnetic and superparamagnetic nanoparticles

Electrospun polymer fibers were prepared containing mixtures of different proportions of ferromagnetic and superparamagnetic nanoparticles. The magnetic properties of these fibers were then explored using a superconducting quantum interference device. Mixed superparamagnetic/ferromagnetic fibers were examined for mesoscale magnetic exchange coupling, which was not observed as theoretically predicted. This study includes some of the highest magnetic nanoparticle loadings (up to 50 wt%) and the highest magnetization values (≈ 25 emu/g) in an electrospun fiber to date and also demonstrates a novel mixed superparamagnetic/ferromagnetic system.