The Influence of Surface-Modification Technology on the Spectral Characteristics of Hydrophilic CdSe/ZnS Nanoparticles upon Interaction with Polyelectrolytes

The spectral and kinetic characteristics of CdSe/ZnS nanoparticles (NPs) surface-modified with cysteamine by two different methods are considered upon interaction with polyelectrolytes. With the use of steady-state and time-resolved fluorescence spectroscopies, it is shown that the fluorescence intensity and stability of NPs in the presence of polyelectrolytes depend on the surface-modification method. It is found that hydrophilic NPs obtained at the interface between two immiscible liquids (chloroform–water) are more resistant to aggregation.     

表面活性剂对气-液界面纳米颗粒吸附规律的影响

通过测定及分析纳米颗粒和表面活性剂-纳米颗粒复配体系在自由吸附过程与动态收缩过程中表面张力的变化,总结了纳米颗粒在气-液界面的吸附排布规律以及表面活性剂对其吸附规律的影响.实验结果表明,自由吸附过程中,随矿化度增加、阳离子活性剂浓度增加,平衡表面张力降低,这与颗粒吸附密度增加及颗粒润湿性改变有关.浓度低于临界胶束浓度(CMC)时,阳离子活性剂体系与混合体系的表面张力差异证明了阳离子活性剂可以通过静电作用吸附于纳米颗粒表面,进而部分溶解于水相;而阴离子活性剂与纳米颗粒相互作用力较弱,对表面张力影响较小.纳米颗粒体系在液滴收缩过程中,表面张力从自由吸附平衡态进一步降低大约9 m N/m,说明自由吸附过程中纳米颗粒不能达到紧密排布;同时表面张力呈现为缓慢降低、快速降低和达到平衡三部分,表面压缩模量可达70 m N/m,满足了液膜Gibbs稳定准则,这将有助于提高泡沫或者乳液稳定性.纳米颗粒-表面活性剂体系在液滴收缩过程中表面张力降低值随活性剂浓度增加而减小;表面压缩模量由高到低依次为:纳米颗粒>阳离子活性剂-纳米颗粒>阴离子-纳米颗粒>表面活性剂.     

One-step synthesis of dye-incorporated porous silica particles

Fluorescent nanoparticles have a variety of biomedical applications as diagnostics and traceable drug delivery agents. Highly fluorescent porous silica nanoparticles were synthesized in a water/oil phase by a microemulsion method. What is unique about the resulting porous silica nanoparticles is the combination of a single-step, efficient synthesis and the high stability of its fluorescence emission in the resulting materials. The key of the success of this approach is the choice of a lipid dye that functions as a surrogate surfactant in the preparation. The surfactant dye was incorporated at the interface of the inorganic silica matrix and organic environment (pore template), and thus insures the stability of the dye?Csilica hybrid structure. The resulting fluorescent silica materials have a number of properties that make them attractive for biomedical applications: the availability of various color of the resulting nanoparticle from among a broad spectrum of commercially dyes, the controllablity of pore size (diameters of ~5?nm) and particle size (diameters of ~40?nm) by adjusting template monomer concentration and the water/oil ratio, and the stability and durability of particle fluorescence because of the deep insertion of surfactant??s tail into the silica matrix.     

Physicochemical properties of nanoparticles affect translocation across pulmonary surfactant monolayer

Interaction between nanoparticles (NPs) and pulmonary surfactant monolayer is one of the most important parts in NP-based pulmonary drug delivery system, which can affect the result of the inhaled nano-drugs and their potential efficacy. Here, we show how surface charge of NPs affects translocation across pulmonary surfactant monolayer with coarse-grained molecular dynamics simulations. The results reveal that the surface charge position of NPs can determine the fate of the inhaled NPs about whether they can have the ability of translocation across the pulmonary surfactant monolayer, which is that NPs with face surface charge can penetrate the pulmonary surfactant monolayer and NPs with edge surface charge cannot. Besides, dynamic process, phase state and the potential of mean force profiles further confirm this result. Moreover, compared to anionic NPs, there is a greater chance for cationic NPs to be adsorbed on the surface of the pulmonary surfactant monolayer, which can further decrease the thickness of the pulmonary surfactant monolayer and reduce the distance between charged NPs and the pulmonary surfactant monolayer. Our researches provide a novel simulation model of NPs on translocation across pulmonary surfactant monolayer and the study of NP-based pulmonary drug delivery system should consider the surface charge of NPs.     

Effect of Shear Flow on Nanoparticles Migration near Liquid Interfaces

The effect of shear flow on spherical nanoparticles (NPs) migration near a liquid–liquid interface is studied by numerical simulation. We have implemented a compact model through which we use the diffuse interface method for modeling the two fluids and the molecular dynamics method for the simulation of the motion of NPs. Two different cases regarding the state of the two fluids when introducing the NPs are investigated. First, we introduce the NPs randomly into the medium of the two immiscible liquids that are already separated, and the interface is formed between them. For this case, it is shown that before applying any shear flow, 30% of NPs are driven to the interface under the effect of the drag force resulting from the composition gradient between the two fluids at the interface. However, this percentage is increased to reach 66% under the effect of shear defined by a Péclet number Pe = 0.316. In this study, different shear rates are investigated in addition to different shearing times, and we show that both factors have a crucial effect regarding the migration of the NPs toward the interfacial region. In particular, a small shear rate applied for a long time will have approximately the same effect as a greater shear rate applied for a shorter time. In the second studied case, we introduce the NPs into the mixture of two fluids that are already mixed and before phase separation so that the NPs are introduced into the homogenous medium of the two fluids. For this case, we show that in the absence of shear, almost all NPs migrate to the interface during phase separation, whereas shearing has a negative result, mainly because it affects the phase separation.     

Generation and characterization of NiO nanoparticles by continuous wave fiber laser ablation in liquid

Pulsed laser ablation in liquid (PLAL) has been widely applied for the generation of nanoparticles (NPs). We report on the generation of NiO NPs using a high-power, high-brightness continuous wave (CW) fiber laser source at a wavelength of 1,070 nm. Characterization of such NPs in terms of size distribution, shape, chemical composition, and phase structure was carried out by transmission electron microscopy (TEM), high-resolution TEM equipped with energy-dispersive X-ray (EDX), and X-ray diffraction (XRD). The results revealed the formation of NiO NPs in water with an average size of 12.6 nm. The addition of anionic surfactant sodium dodecyl sulfate (SDS) reduced the size of NiO NPs down to 10.4 nm. The shape of the NPs was also affected by the SDS, showing the change of shapes from spherical domination in water to tetragonal with increased SDS concentrations. Furthermore, the NiO NPs generated in water and SDS solutions were dual phase containing both cubic and rhombohedral structures. It was also found that the NiO NPs were single crystalline in nature irrespective of the size and shape.     

Surface triple points and multiple-layer transitions observed by tuning the surface field at smectic liquid-crystal-water interfaces

We present an ellipsometric study of the interface between a smectic liquid crystal and water in the presence of a nonionic surfactant. The surfactant concentration serves as a handle to tune the surface field. For sufficiently large surfactant concentrations, a smectic phase is present at the interface in the temperature range above the smectic-A-isotropic bulk transition; when the bulk transition is approached, the thickness of this surface phase grows via a series of layer-by-layer transitions at which single smectic layers are formed. At lower surfactant concentrations, transitions appear at which the thickness of the surface phase jumps by multiple smectic layers, thereby implying the existence of triple points at which surface phases with different smectic layer numbers coexist. This is the first experimental demonstration of such surface triple points which are predicted by theoretical models.     

Total Internal Reflection Fluorescence Spectroscopy for Investigating the Adsorption of a Porphyrin at the Glass/Water Interface in the Presence of a Cationic Surfactant Below the Critical Micelle Concentration

Total internal reflection fluorescence (TIRF) spectroscopy was used to investigate the adsorption behavior of meso-tetrakis(p-sulfonatophenyl)porphyrin (TPPS) at the glass/water interface in the presence of a cationic surfactant (cetyltrimethylammonium bromide, CTAB) far below the critical micelle concentration. The adsorption model of TPPS at the glass/water interface in the presence of low concentration of CTAB was proposed, which was different from the adsorption of TPPS in the presence of micelles of CTAB at the glass/water interface. TPPS and CTAB did not form stable complex at the interface in dilute system. The interfacial species of TPPS were analyzed by comparing the spectra of TPPS at the glass/water interface and in the aqueous phase. The influences of the TPPS concentration, the CTAB concentration, and the pH values on the interfacial fluorescence spectra and intensities were studied. It was demonstrated that electrostatic interaction and hydrophobicity performed an important role on the adsorption of TPPS in the presence of CTAB. The different effects of TPPS concentration on the adsorption behaviour of TPPS at different pH were observed for the first time. It was found that the adsorption isotherms of TPPS at glass/water interface could fit Freundlich equation at pH 7.1.     

Synthesis and Characterization of Oxazine-doped Silica Nanoparticles for Their Potential Use as Stable Fluorescent Reagents

The synthesis process to obtain silica nanoparticles (NPs) doped with two oxazine dyes, nile blue and cresyl violet, has been investigated using a modification of the reverse micelle microemulsion method and a procedure based on the Stöber method. A micellar medium provided by the non-ionic surfactant Triton X-100 in a hexanol:water mixture and an ethanol:water mixture, have been used to provide the synthesis medium in each case. Tetraethoxysilane has been used as the initiator of the polymerization and condensation reactions after its hydrolysis in basic medium using ammonium hydroxide. Dye-silane precursor NPs have been also synthesized in order to compare their potential advantages against the NPs obtained by the direct encapsulation of the oxazine dyes. Size distribution and fluorescence of the synthesized NPs, which were monitored using Transmision Electron Microscopy (TEM) and a microplate reader, respectively, depend on the molar ratio and total concentration of the reagents involved in the synthesis. NPs obtained using the developed synthesis procedures had sizes below 400 nm in most instances and the best luminescent properties were observed for NPs with sizes ranging from 100 to 300 nm. Lower sizes result in a decrease in the fluorescence intensities of these nanomaterials. Parameters related with the luminescence features of these NPs were calculated in order to compare the feasibility of both synthesis approaches. The repeatability of the reverse-micelle microemulsion procedure performed in different days gave a relative standard deviation of 10% for the fluorescence intensity values.     

Wettability alteration of sandstones by silica nanoparticle dispersions in light and heavy crude oil

Unlike conventional oil production methods, enhanced oil recovery (EOR) processes can recover most oil products from the reservoir. One method, known as wettability alteration, changes the hydrophilicity of the reservoir rock via decreased surface interactions with crude oils. The mitigation of these attractive forces enhances petroleum extraction and increases the accessibility of previously inaccessible rock deposits. In this work, silica nanoparticles (NPs) have been used to alter the wettability of two sandstone surfaces, Berea and Boise. Changes in wettability were assessed by measuring the contact angle and interfacial tension of different systems. The silica NPs were suspended in brine and a combined solution of brine and the Tween®20 nonionic surfactant at concentrations of 0, 0.001, and 0.01 wt% NP with both light and heavy crude oil. The stability of the different nanofluids was characterized by the size, zeta potential, and sedimentation of the particles in suspension. Unlike the NPs, the surfactant had a greater effect on the interfacial tension by influencing the liquid-liquid interactions. The introduction of the surfactant decreased the interfacial tension by 57 and 43% for light and heavy crude oil samples, respectively. Imaging and measurements of the contact angle were used to assess the surface-liquid interactions and to characterize the wettability of the different systems. The images reflect that the contact angle increased with the addition of NPs for both sandstone and oil types. The contact angle in the light crude oil sample was most affected by the addition of 0.001 wt% NP, which altered both sandstones’ wettability. Increases in contact angle approached 101.6% between 0 and 0.001 wt% NPs with light oil on the Berea sandstone. The contact angle however remained relatively unaffected by addition of higher NP concentrations, thus indicating that low NP concentrations can effectively be used for enhancing crude oil recovery. While the contact angle of the light crude oil plateaued, the heavy crude oil continued to increase with an increase in NP concentration; therefore indicating that a maximum contact angle in heavy crude oil was not yet achieved. The introduction of NPs in light and heavy crude oil samples altered both the Berea and Boise sandstone systems’ wettability, which in turn indicated the efficacy of the silica NPs and surfactants in generating a more water-wet reservoir. Consequently, silica NPs and surfactants are most promising for EOR across the range of oil types.     

表面活性剂含量对全息聚合物分散液晶光栅电光特性的影响

研究了含表面活性剂Actyflon-G04的全息聚合物分散液晶透射光栅的表面形貌和电光特性,通过理论分析得出驱动电压和膜的锚定能及表面自由能的关系.实验结果表明,在Actyflon-G04含量为4wt%-8wt%时光栅相分离程度高,相界面平滑,聚合物层的致密度增加.光栅的衍射效率达到96%,接近理想值.实现了在提高光栅衍射效率的同时降低驱动电压,使光栅的电光特性得到改善.     

Study on Synthesis of Silver Nanoparticles Using dsDNA as Template and Detection of GSH

In this work, silver nanoparticles are synthesized using a simple and sensitive method by using double-stranded DNA (dsDNA-Ag NPs) as a template. The prepared dsDNA-Ag NPs are characterized by fluorescence spectroscopy analysis, X-ray photoelectron spectroscopy analysis, and transmission electron microscopy analysis. The excitation wavelength of the prepared silver nanoparticles is 295 nm, the emission wavelength is 377 nm, the average particle size is 11.2 nm, and the dispersion is uniform with pleasurable stability. The nanomaterials are used as fluorescent probes to detect glutathione (GSH). After adding glutathione to the dsDNA-Ag NPs fluorescent probes, the fluorescence of dsDNA-Ag NPs is burst due to electron transfer and S Ag bond generation, and the linear range of detection concentration is 0–90 mm with a detection limit of 0.37 mm .     

两个非磁性颗粒在磁流体中的沉降现象研究

在磁场作用下,在磁流体里添加非磁性颗粒(non-magnetic particles,NPs),可以使得NPs形成不同的结构,操控NPs的运动从而影响磁流体的特性,这种应用逐渐受到了研究者的关注.为了更好地操控磁流体里NPs的运动,本文采用一种多物理模型研究在外加磁场作用下,磁流体中两个NPs沉降的运动过程.其中,用格子玻尔兹曼方法模拟磁流体的运动,外加磁场对磁流体的影响用一种自修正方法求解泊松方程,这个自修正方法可以使欧姆定律满足守恒定律.NPs之间的偶极干扰力采用偶极力模型,同时采用一种相对过渡平滑的共轭边界条件处理NPs与磁流体交界面的流固干扰以避免磁场密度过渡的突变.本文主要探究两个NPs在磁流体中的沉降,揭示磁场作用下NPs的相互干扰原理;同时,对控制NPs运动时的参数进行调节,得到NPs不同的运动轨迹,达到操控颗粒运动的目的.本研究可对NPs在磁流体中的应用提供定量的分析结果,对NPs在工业上的应用提供有力的理论支撑.     

Laser synthesis of aluminium nanoparticles in biocompatible polymer solutions

Pulsed laser ablation of Aluminium (Al) in pure water rapidly forms a thin alumina (Al₂O₃) layer which drastically modifies surface plasmon resonance (SPR) absorption characteristics in deep-UV region. Initially, pure aluminium nanoparticles (NPs) are generated in water without any stabilizers or surfactants at low laser fluence which gradually transform to stable Al-Al₂O₃ core-shell nanostructure with increasing either residency time or fluence. The role of laser wavelength and fluence on the SPR properties and oxidation characteristics of Al NPs has been investigated in detail. We also present a one-step in situ synthesis of oxide-free stable Al NPs in biocompatible polymer solutions using laser ablation in liquid method. We have used nonionic polymers (PVP, PVA and PEG) and anionic surfactant (SDS) stabilizer to suppress the Al₂O₃ formation and studied the effect of polymer functional group, polymeric chain length, polymer concentration and anionic surfactant on the incipient embryonic aluminium particles and their sizes. The different functional groups of polymers resulted in different oxidation states of Al. PVP and PVA polymers resulted in pure Al NPs; however, PEG and SDS resulted in alumina-modified Al NPs. The Al nanoparticles capped with PVP, PVA, and PEG show a good correlation between nanoparticle stability and monomeric length of the polymer chain.     

Optical Properties of Micro-patterned Silver Nanoparticle Substrates

In this paper, we describe a novel technique for depositing metal nanoparticles (NPs) on a planar substrate whereby the NPs are micro-patterned on the surface by a simple stamp-printing procedure. The method exploits the attractive force between negatively charged colloidal metal NPs and positively-charged polyelectrolyte layers which have been selectively deposited on the surface. Using this technique, large uniform areas of patterned metal NPs, with different plasmonic properties, were achieved by optimisation of the stamping process. We report the observation of unusual fluorescence emission from these structures. The emission was measured using epifluorescence microscopy. Fluorescence lifetime behaviour was also measured. Furthermore, the μ-patterned NPs exhibited blinking behaviour under 469 nm excitation and the fluorescence spectrum was multi-peaked. It has been established that the fluorescence is independent of the plasmon resonance properties of the NPs. As well as optimising the novel NP μ-patterning technique, this work discusses the origin and characteristics of the anomalous fluorescence behaviour in order to characterise and minimise this unwanted background contribution in the use of metal NPs for plasmonic enhancement of fluorescence for optical biochip applications.     

纳米氧化锌对细叶蜈蚣草(Egeria najas)光合作用的影响

采用细叶蜈蚣草(Egeria najas)作为受试植物,分别用不同浓度的ZnO NPs处理细叶蜈蚣草六天,通过OJIP荧光动力学曲线和脉冲瞬态荧光动力学曲线评估暴露在不同浓度的ZnO NPs悬浮液中的细叶蜈蚣草的光合性能。当细叶蜈蚣草暴露在ZnO NPs悬浮液中,光系统Ⅱ关闭的净速率（M_O）、J点的相对可变荧光强度（V_J）和单位反应中心用于热能耗散的能量（DI₀/RC）有明显的下降趋势（p<0.05）,最大光化学量子效率（Φ_P0）、捕获的激子中用来推动电子传递的效率（Ψ₀）、电子传递的量子产额（Φ_E0）、实际光化学量子效率（′_PSⅡ）有上升的趋势（p<0.05）。表明ZnO NPs增强了光系统Ⅱ反应中心之间的连通性、促进了光系统Ⅱ受体侧的电子传递和光能的利用,即ZnO NPs在某些方面促进了细叶蜈蚣草的光合作用。用相应浓度的Zn2+溶液来处理细叶蜈蚣草,当细叶蜈蚣草暴露在Zn2+溶液中,光系统Ⅱ关闭的净速率、J点的相对可变荧光强度和单位反应中心用于热能耗散的能量有明显的上升趋势（p<0.05）,最大光化学量子效率、捕获的激子中用来推动电子传递的效率、电子传递的量子产额、实际光化学量子效率有下降的趋势（p<0.05）,单位反应中心吸收的光能（ABS/RC）、捕获的光能（TR₀/RC）和非调节性能量耗散量子产量（′_NO）有明显的上升趋势（p<0.05）,即Zn2+降低了光系统Ⅱ反应中心之间的连通性、抑制了光系统Ⅱ受体侧的电子传递和光能的利用并使反应中心失活,即Zn2+抑制了细叶蜈蚣草的光合作用。在ZnO NPs处理细叶蜈蚣草的实验中并没有发现光合作用受抑制情况,表明ZnO NPs的促进作用强于其释放的游离Zn2+的抑制作用。     

掺杂香豆素6的杂化纳米颗粒的制备及荧光性能研究(英文)

采用一种再沉淀-封装法制备了掺杂香豆素6(C6)的杂化荧光纳米颗粒,并通过SEM和DLS对其进行了形貌和粒径大小表征。在450 nm光激发下,制备的C6掺杂纳米颗粒表现出绿色荧光。通过比较光致发光光谱随掺杂浓度的变化,得出C6掺杂纳米颗粒的浓度猝灭是因为分子间能量转移而非C6分子聚集所致。另外,由于所选聚合物基质材料PS和PMMA分子结构的区别,导致PS-基质和PMMA-基质的纳米颗粒的光谱形状不同。C 6分子在PS-基质的纳米颗粒中处于两种不同的微环境,所以发射峰较宽;PMMA是线性分子,PMMA-基质的纳米颗粒中只存在一种局域环境,所以发射峰较窄。高的掺杂浓度会超过纳米颗粒对C6分子的负载能力,从而导致C6分子在水溶液中聚集。     

Statistical characterization of an ensemble of functional neural networks

The Ginzburg-Landau free energy functional with two order parameters has been widely used to describe surfactant adsorption phenomena at the interface between two immiscible fluids such as oil and water. To model surfactant adsorption, additional surfactant related terms are added to the original free energy functional which models an immiscible binary mixture. In this paper, we present a detailed comparison of phase-field models for an immiscible binary mixture with surfactant. In particular, we investigate the effects of mathematical model parameters on equilibrium surfactant profile across the interface between the immiscible binary mixture. Most previous models have severe time-step constraints due to the nonlinear coupling of order parameters. To solve these stability problems, we propose a special case of these models which allows the use of a much larger time-step size. We also apply a type of unconditionally gradient stable scheme and a fast multigrid method to solve the proposed model efficiently and accurately.     

Spectroscopic studies on the interaction between ZnSe nanoparticles with bovine serum albumin

The interaction between ZnSe nanoparticles (NPs) and bovine serum albumin (BSA) was studied by UV–vis, fluorescence spectroscopic techniques. The results showed that the fluorescence of BSA was strongly quenched by ZnSe NPs and the quenching mechanism was discussed to be a static quenching procedure, which was proved by quenching constant (K_q). The recorded UV–vis data and the fluorescence data quenching by the ZnSe NPs showed that the interaction between them leads to the formation of ZnSe–BSA complex. Based on the synchronous fluorescence spectra, it was established that the conformational change of BSA was induced by the interaction of ZnSe with the tyrosine micro-region of the BSA molecules. Furthermore, the temperature effects on the structural and spectroscopic properties of individual ZnSe NPs and protein and their bioconjugates (ZnSe–BSA) were also researched. It was found that, compared to the monotonic decrease of the individual ZnSe NPs fluorescence intensity, the temperature dependence of the ZnSe–BSA emission had a much more complex behavior, which was highly sensitive to the conformational changes of the protein.     

Synthesis and characterization of superparamagnetic nanoparticles coated with fluorescent gold nanoclusters

Multifunctional nanoparticles (NPs) combining the superparamagnetism of Mn−Zn ferrite and the fluorescence property of gold nanoclusters (NCs) have been prepared by wet chemistry. Magnetic NPs synthesized by co-precipitation method were coated several times with oppositely charged polyelectrolytes (PEs) using the layer-by-layer technique. Common techniques (Fourier transform infrared spectroscopy, electron microscopy, zeta potential, etc.) indicated the monodispersity and the stability of the coated NPs providing a positive charged surface. Fluorescent gold NCs bound to a standard protein bovine serum albumin were adsorbed on the surface of the magnetic NPs. Structural investigations proved the presence of small gold clusters (~2 nm) in a shell surrounding the magnetic nanomaterial. The stable nanocomposite kept the original fluorescence property of the metal clusters with 211-fold increase of the red emission (λ = 690 nm) compared to the uncoated NPs. These NPs can be moved with a permanent magnet despite a 72-wt% increase of the non-magnetic fraction due to the PE coating and the protein adsorption.