Nanoparticles Of Different Materials Research Articles

Controlling cement hydration with nanoparticles

Nanoparticles have recently become a focus in the development of new accelerators for cement hydration. We have produced nanoparticles of different materials like Al2O3, C–S–H-phase, and quartz by different top-down and bottom-up production methods. The effect of these particles on the cement hydration was followed by heat flow calorimetry to evaluate their acceleration potential as a function of the particles material, particles size and their percentage in the cement paste. In this work we will demonstrate which particles have the best potential as accelerators for cement hydration and therefore are most suitable for further investigations. Interestingly, nanoparticles which have a retarding effect on cement hydration were also found.

Numerical study of nanoparticle sensors based on the detection of the two-photon-induced luminescence of gold nanorod antennas

We investigate numerically the modification of the nonlinear optical properties of a nanoantenna in the trapping of nanoparticles (NPs) by using both the discrete dipole approximation method and the finite-difference time-domain technique. The nanoantenna, which is formed by two gold nanorods (GNRs) aligned end to end and separated by a small gap, can emit strong two-photon-induced luminescence (TPL) under the excitation of a femtosecond laser light which is resonant with its longitudinal surface plasmon resonance. In addition, the excited antenna can stably trap small NPs which in turn induce modifications in the emitted TPL. These two features make it a promising candidate for building highly sensitive detectors for NPs of different materials and sizes. It is demonstrated that sensors built with antennas possess higher sensitivities than those built with single GNRs and nanorod-based antennas are more sensitive than nanoprism-based antennas. In addition, it is found that the trapping probability for a second NP is significantly reduced for the antenna with a trapped NP, implying that trapping of NPs may occur sequentially. A relationship between the TPL of the system (antenna + NP) and the optical potential energy of the NP is established, enabling the extraction of the information on the optical potential energy and optical force by recording the TPL of the system. It is shown that the sequential trapping and releasing of NPs flowing in a microfluid channel can be realized by designing two different antennas arranged closely.

Looking into the structure of Ge nano-crystals through combined Diffraction/XAFS

Nano-particles of different materials including II-VI (ZnS, ZnO, etc.), III-V (AlN, GaN, etc.) and IV (Si, Ge, etc.) have been applied widely because of their superb optical-electrical properties. More importantly, the size & structure-dependent character of their physical properties due to the quantum confinement effect attracted much research interest during the past decades [1]. Ge is characterized by relatively large Exciton Bohr Radius (≍24nm) [3], which potentially favors the quantum confinement effects for tuning the photoluminescence (PL) properties. Besides, the low toxicity of Ge suggests potential biological applications such as cell imaging and labeling [4]. For the structure characterization of our prepared Ge quantum dots (QDs), we used the in-house X-ray pair distribution function (PDF) machine (X-ray from Ag source with wavelength down to 0.056nm) and Diamond light source synchrotron radiation source (XAFS, XRD, PL, etc.) to characterize the atomic structure. Several other methods such as TEM and SAED were used to provide a comprehensive picture of QDs on nanoscale. The results showed that our as-prepared Ge QDs are amorphous with small size, and annealing process could attenuate the Ge-O bonding. In both aged as prepared and fresh annealed samples we observed a diffraction peak corresponding to d-spacing around 2.8Å, which can be associated with either ST12 or BC8 metastable phase of Ge. Moreover, samples showing extra diffraction peaks also shows different XANES features from that of diamond Ge. The fdmnes calculation and FitIt fitting was carried out to further look into structural information.

Growth Mechanism of Monodisperse Spherical Particles under Nanosecond Pulsed Laser Irradiation

It is well-known that the colloidal nanoparticles irradiated by laser can be reduced in size. Recently, we demonstrated that at particular experimental conditions, colloidal nanoparticles of different materials can grow under pulse laser irradiation, finally transforming to the near monodisperse submicron spheres. To date, the detailed mechanism of this process was not revealed. In this work, we explore the mechanism of particle growth by applying the particle heating-melting-evaporation model. Our investigations show that the process of particle growth can be divided into two stages. At the initial stage, particle agglomeration is the dominant factor for the fast particle growth. Then, the process continues as long as the particles can be melted. The final particle diameter is determined by the value of laser fluence, because the laser fluence determines the maximum diameter of the particle which can be melted. Good agreement between the experimental results and results of calculation was obtained.

Mechanisms of nanoparticle formation by ultra-short laser ablation of metals in liquid environment

Laser ablation in liquids is now commonly used to produce colloidal nanoparticles (NPs) that have found numerous applications in different areas. In experiments, NPs of different materials can be rather easily obtained by using laser systems with various pulse durations, shapes, wavelengths, and fluences. In this paper, we focus our attention on metal (gold) NPs produced by ultra-short laser pulses. To better understand the mechanisms of the NPs formation, we perform modeling of femtosecond laser interactions with a gold target in the presence of liquid (water). Simulation of the ablation process over several nanoseconds shows that most of the primary NPs originate from the ablated metastable liquid layer, whereas only a minority is formed by condensation inside the cavitation bubble. These particles will further grow/evaporate, and coagulate during a much longer collision stage in the liquid colloid.

Two-step synthesis method for regular arrays of nano-particles embedded in oxide layers

Abstract Governed by diffusion and reaction kinetics, regular nano-porous oxide layers with embedded metal oxide nano-particles are formed. To facilitate this process, metals are evaporated through ultra-thin alumina membranes (UTAMs) onto Si substrates, followed by a well-controlled oxidation process. The structural parameters of the oxide layers such as the layer thickness and the pore depth are tailorable. Furthermore the growth mechanism of the composite system is described by a theoretical model. This versatile synthesis method shows potential to become a general fabrication strategy to realize nano-porous surface structures with embedded nano-particles of different materials for various purposes from fundamental studies to technical applications.

Correlated Structure and Optical Property Studies of Plasmonic Nanoparticles

This article provides a review of our recent studies of single metal nanoparticles and single nanoparticle clusters aimed at correlating the structural and plasmonic properties of the same entity. The correlation between the structure and the optical properties arising from the localized surface plasmon resonance (LSPR) on single nanoparticles from various samples is described. Nanoparticles of different materials (Ag and Au) and shapes (spheres, cubes, triangles) are considered. Experiments were carried out using transmission electron microscopy (TEM), dark-field spectroscopy, and surface-enhanced Raman spectroscopy (SERS). Results of those measurements were compared with electrodynamics calculations to provide insight into the interpretation and physical meaning of the experimental results. We examine correlated studies of triangular nanoparticle arrays to highlight the significance of single entity measurements over ensemble-averaged measurements. Furthermore, we show how an examination of statistics on large data sets helps draw quantitative structure―LSPR relationships. We also show that implementing SERS in correlated measurements improves the understanding of factors important in determining SERS enhancements. Finally, we extend the scope of correlated measurements to the tracking and controlled manipulation of single nanoparticles, thus paving the way for in vivo diagnostics using nanomaterials.

Gold nanoparticles as advanced building blocks for nanoscale self-assembled systems

The goal of controlling materials on the nanoscale with the efficiency and elegancy of nature from a bottom up approach is a key ambition of nanoscience. Nanoparticles of different materials in a wide variety of shapes and sizes are a popular starting point due to their novel physical and chemical properties. If we had the ability to control precisely the surface properties of nanoparticles, we could direct their assembly into higher order structures to provide a route to new materials and devices, as well as synthetic analogues of biological macromolecular complexes. The scope of this review is to discuss and overview the current knowledge base and approaches that are used to control the surface properties of nanoparticles and to impart recognition functions to the nanoparticles that can drive self-assembly processes. The approaches discussed focus on the self-assembly and the self-organisation of ligands, in solution, on the surface of gold nanoparticles.

Water-Soluble Peptide-Coated Nanoparticles: Control of the Helix Structure and Enhanced Differential Binding to Immune Cells

The stabilizing action of C(α)-tetrasubstituted α-amino acids inserted into a sequence of short peptides allowed for the first time the preparation of water-soluble nanoparticles of different materials coated with a helix-structured undecapeptide. This peptide coating strongly favors nanoparticle uptake by human immune system cells.

Wavelength-Dependent Differential Interference Contrast Microscopy: Multiplexing Detection Using Nonfluorescent Nanoparticles

The wavelength dependence of plasmonic nanoparticles' contrasts in differential interference contrast (DIC) microscopy has been exploited previously for unambiguous identification and dynamic tracking of these nanoprobes in complex environments (Anal. Chem. 2009, 81, 9203-9208). In the present study, the suitability of multiplexing detection in DIC microscopy was investigated systematically with 19 kinds of nanoparticles of different materials and/or sizes. A unique DIC contrast spectrum was found for each kind of nanoparticle. Multiplexing detection was accomplished by measuring DIC contrasts at a minimum of two specific illumination wavelengths. The main advantages of DIC microscopy for multiplexing detection over other nonfluorescence techniques, such as dark field microscopy and surface-enhanced Raman scattering, were demonstrated by differentiating four kinds of nanoparticles on the cell membrane while providing high-contrast images of both the nanoprobes and cell features.

Influence of acceleration voltage on scanning electron microscopy of human blood platelets

Scanning electron microscopy (SEM) is used to view a variety of surface structures, molecules, or nanoparticles of different materials, ranging from metals, dental and medical instruments, and chemistry (e.g. polymer analysis) to biological material. Traditionally, the operating conditions of the SEM are very important in the material sciences, particularly the acceleration voltage. However, in biological sciences, it is not typically seen as an important parameter. Acceleration voltage allows electrons to penetrate the sample; thus, the higher the acceleration voltage the more penetration into the sample will occur. As a result, ultrastructural information from deeper layers will interfere with the actual surface morphology that is seen. Therefore, ultimately, if acceleration voltage is lower, a better quality of the surface molecules and structures will be produced. However, in biological sciences, this is an area that is not well-documented. Typically, acceleration voltages of between 5 and 20 kV are used. This manuscript investigates the influence of acceleration voltages ranging from 5 kV to as low as 300 V, by studying surface ultrastructure of a human platelet aggregate. It is concluded that, especially at higher magnifications, much more surface detail is visible in biological samples when using an acceleration voltage between 2 kV and 300 V.

Erratum: On-chip single nanoparticle detection and sizing by mode splitting in an ultrahigh-Q microresonator

The ability to detect and size individual nanoparticles with high resolution is crucial to understanding the behaviour of single particles and effectively using their strong size-dependent properties to develop innovative products. We report realtime, in situ detection and sizing of single nanoparticles, down to 30 nm in radius, using mode splitting in a monolithic ultrahigh-quality-factor (Q) whispering-gallery-mode microresonator. Particle binding splits a whispering-gallery mode into two spectrally shifted resonance modes, forming a self-referenced detection scheme. This technique provides superior noise suppression and enables the extraction of accurate particle size information with a single-shot measurement in a microscale device. Our method requires neither labelling of the particles nor a priori information on their presence in the medium, providing an effective platform to study nanoparticles at single-particle resolution. With the rapid progress in nanotechnology, nanoparticles of different materials and sizes have been synthesized and engineered as key components in various applications ranging from solar cell

Controlled growth of Co nanoparticle assembly on nanostructured template Al2O3∕NiAl(100)

Based on the systematic studies of the growth temperature, deposition rate, and annealing effects, the control of Co nanoparticle density, size, and alignment is demonstrated to be feasible on a nanostructured template Al2O3∕NiAl(100). At 140–170K, a slow deposition rate (0.027ML∕min) promises both the linear alignment and the high particle density. 1.5 ML Co nanoparticle assembly sustains the density of ∼260∕104nm2 even after 800–1090K annealing. This study also indicates the possibilities of the controlled growth for nanoparticles of different materials.

Characterization of metal-oxide nanosensors fabricated with focused ion beam (FIB)

A procedure to contact single metal-oxide nanowires and nanoparticles of different materials using a Dual Beam FIB has been developed. The quality of the electrical contacts has been evaluated and the possibility of extracting the electrical parameters of these nanowires and nanoparticles demonstrated. The response of some of them to different gases is presented, proving the feasibility of fabricating metal-oxide nanosensors.

Electrophoretic Separation of Nanoparticles with a Discrete Number of Functional Groups

AbstractA concept is describe that facilitates the modification of colloidal nanoparticles of different materials with an exactly known number of variable functional groups. In particular, a procedure for the surface functionalization of nanoparticles with a controlled number of mono‐ or bifunctional poly(ethylene glycol) (PEG) molecules of suitable chain length is reported. Conjugates of nanoparticles with one, two, and three PEG molecules per nanoparticle could be separated using gel electrophoresis. Molecules with additional functionalities could be conjugated to the free ends of the bifunctional PEG molecules. In this way the PEG molecules act as convenient spacers that allow for the sorting of nanoparticles with a discrete number of functional groups.

Production of nanoparticles of different materials by means of ultrashort laser pulses

Ultrashort pulsed laser ablation in vacuum of different targets was performed in order to investigate the possibility of producing nanoparticles with controlled size and shape. A systematic morphology characterization of deposited products was performed for nickel and silicon as a function of laser pulse intensity and wavelength, at a fixed pulse repetition rate. The nanoparticles were investigated by atomic force microscopy, and clear trends for their size and shape anisotropy were evidenced. The best conditions to obtain nanosized particles of oblate ellipsoidal shape, with the minor axis below 10 nm, were determined in the case of nickel targets. Our results show that ultrashort pulse laser deposition can be considered as an interesting technique for the tailoring of nanogranular films with the desired particles dimension and shape, according to the peculiar properties required in specific applications. Moreover, the preliminary features are very promising from the point of view of the production of magnetoresistive films with specific anisotropy.

Combined Optical Tweezers/Ion Beam Technique to Tune Colloidal Masks for Nanolithography

A method is presented to control the in-plane ordering, size, and interparticle distance of nanoparticles fabricated by evaporation through a mask of colloidal particles. The use of optical tweezers combined with critical point drying gives single-particle position control over the colloidal particles in the mask. This extends the geometry of the colloidal masks from (self-organized) hexagonal to any desired symmetry and spacing. Control over the mask's hole size is achieved by MeV ion irradiation, which causes the colloids to expand in the in-plane direction, thus shrinking the size of the holes. After modification of the mask, evaporation at different angles with respect to the mask gives additional control over structure and interparticle distance, allowing nanoparticles of different materials to be deposited next to each other. We demonstrate large arrays of metal nanoparticles with dimensions in the 15-30 nm range, with control over the interparticle distance and in-plane ordering.

Compaction of agglomerates of aerosol nanoparticles: A compilation of experimental data

The compacting behavior of agglomerated aerosol nanoparticles in the size range between 7 and 150 nm was investigated using available literature data. We observed a characteristic behavior, which can be described by three separate steps. When comparing the first step, the compaction from agglomerates into spherules, differences could be observed for nanoparticles of different materials. It is seen from the available data that smaller particles compact at lower temperatures. For most materials where data available (Ag, Au, Fe, W, PbS and SnO2), the compaction temperatures were found to lie in a temperature interval, between 1/3 and 1/2 of the bulk melting temperature. For the data available on TiO2, on the other hand, the compaction temperature corresponds to about 2/3 of the bulk melting temperature. Thus, a fundamental difference might exist in the sintering behavior of titania as compared with other materials. This difference may be attributed to a lower degree of cleanliness of the titania particles.

Near-infrared surface plasmon resonance sensing on a Si platform with nanoparticle-based signal enhancement

A Si-based surface plasmon resonance (SPR) system is examined in conditions of the nanoparticle-enhanced sensing. The system is equipped with near IR pumping light and a silicon coupling prism, used with SPR-supporting gold film in the Kretschmann– Raether geometry. Using Maxwell–Garnett (MG) effective medium theory, we modeled the SPR-related response of the system to the absorption of colloidal nanoparticles of different materials (Au, Cu, Pt, Ag, Al, Ti, Pd) on gold. We show that this response strongly depends on the nanoparticle fill factor, associated with a relative volume of nanoparticles in the absorbed layer. For low fill factors (fm � 0.1), corresponding to relatively low concentrations of small nanoparticles, the absorption of nanoparticles of different materials leads to almost identical angular shifts of the SPR dip, but to a quite different intensity damping at the dip point. In contrast, the increase of the fill factor results in quite different angular and intensity SPR characteristics for the materials used, with the most pronounced sensing responses for Pt, Pd and Ti. The proposed analysis enables to estimate the efficiency of nanoparticles of different materials as markers in nanoparticle-enhanced SPR sensing. 2004 Elsevier B.V. All rights reserved.