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Nanoparticle Assemblies (nanoparticle + assembly)

Distribution by Scientific Domains

Polymers and Materials Science	71%
Chemistry	21%

Selected Abstracts

Multifunctional Magnetoplasmonic Nanoparticle Assemblies for Cancer Therapy and Diagnostics (Theranostics),

MACROMOLECULAR RAPID COMMUNICATIONS, Issue 2 2010
Wei Chen
Abstract In this work, we describe the preparation and biomedical functionalities of complex nanoparticle assemblies with magnetoplasmonic properties suitable for simultaneous cancer therapy and diagnostics (theranostics). Most commonly magnetoplasmonic nanostructures are made by careful adaptation of metal reduction protocols which is both tedious and restrictive. Here we apply the strategy of nanoscale assemblies to prepare such systems from individual building blocks. The prepared superstructures are based on magnetic Fe3O4 nanoparticles encapsulated in silica shell representing the magnetic module. The cores are surrounded in a corona-like fashion by gold nanoparticles representing the plasmonic module. As additional functionality they were also coated by poly(ethyleneglycol) chains as a cloaking agent to extend the blood circulation time. The preparation is exceptionally simple and allows one to vary the contribution of each function. Both modules can carry drugs and, in this study, they were loaded with the potential anticancer drug curcumin. A comprehensive set of microscopy, spectroscopy and biochemical methods were applied to characterize both imaging and therapeutic function of the nanoparticle assemblies against leukemia HL-60 cells. High contrast magnetic resonance images and high apoptosis rates demonstrate the success of assembly approach for the preparation of magnetoplasmonic nanoparticles. This technology allows one to easily "dial in" the functionalities in the clinical setting for personalized theranostic regiments. [source]

Molecular Structure,Function Relations of the Optical Properties and Dimensions of Gold Nanoparticle Assemblies,

ANGEWANDTE CHEMIE, Issue 7 2010
Revital Kaminker
Geometrische Vorgaben: Die Form einer Reihe von molekularen Vernetzern, die eine bis vier Pyridyleinheiten tragen, bestimmt die optischen Eigenschaften von Aggregaten aus Goldnanopartikeln (AuNPs; siehe Bild). Wie eine TEM-Analyse belegt, übertragen sich die unterschiedlichen Molekülstrukturen bei der Aggregation der AuNPs auf die Submikrometerebene. [source]

Nanoimprinted Polyethyleneimine: A Multimodal Template for Nanoparticle Assembly and Immobilization

ADVANCED FUNCTIONAL MATERIALS, Issue 18 2009
Chandramouleeswaran Subramani
Abstract Polyethyleneimine (PEI) is used as a scaffold for integrated top-down/bottom-up fabrication. In this synergistic strategy, patterned PEI surfaces are created using thermal nanoimprint lithography (NIL) using a sacrificial polystyrene (PS) overlayer. These imprinted surfaces act as versatile templates for assembling nanoparticles and dyes, with the amine groups of the PEI enabling electrostatic assembly, carbodiimide coupling, and dithiocarbamate attachment to the nanoimprinted features. The efficient assembly of particles and dyes is confirmed through fluorescence and atomic force microscopy. In these studies the PS overlayer serves two roles. First, the PS layer protects the PEI surface during the plasma-etch removal of the residual layer of the NIL process. Second, the PS overlayer serves as a mask, enabling sequential functionalization of the sides and the tops of the PEI features. [source]

Materials Fabricated by Micro- and Nanoparticle Assembly , The Challenging Path from Science to Engineering

ADVANCED MATERIALS, Issue 19 2009
Orlin D. Velev
Abstract We classify the strategies for colloidal assembly and review the diverse potential applications of micro- and nanoparticle structures in materials and device prototypes. The useful properties of the particle assemblies, such as high surface-to-volume ratio, periodicity at mesoscale, large packing density, and long-range ordering, can be harnessed in optical, electronic, and biosensing devices. We discuss the present and future trends in the colloidal- assembly field, focusing on the challenges of developing fabrication procedures that are rapid and efficiently controlled. We speculate on how the issues of scalability, control, and precision could be addressed, and how the functionality of the assemblies can be increased to better match the needs of technology. [source]

Forces between Surfactant-Coated ZnS Nanoparticles in Dodecane: Effect of Water,

ADVANCED FUNCTIONAL MATERIALS, Issue 16 2006
Alig, R. Godfrey
Abstract The forces between mica surfaces confining solutions of spherical and rod-shaped ZnS nanoparticles (diameter ca. 5,nm) coated with hexadecylamine or octadecylamine surfactant in dodecane have been measured in the absence and after the introduction of trace amounts of water. Initially, or at very low water content, the water molecules cause the nanoparticles to aggregate and adsorb on the hydrophilic mica surfaces, resulting in a long-range exponentially decaying repulsive force between the surfaces. After longer times (>,20,h), water bridges nucleate and grow between the nanoparticles and mica surfaces, and attractive capillary forces then cause a long-range attraction and a strong (short-range) adhesion. It is found, as has previously been observed in nonaqueous bulk colloidal systems, that even trace amounts of water have a profound effect on the interactions and structure of nanoparticle assemblies in thin films, which in turn affect their physical properties. These effects should be considered in the design of thin-film processing methodologies. [source]

Photoluminescence Quenching Control in Quantum Dot,Carbon Nanotube Composite Colloids Using a Silica-Shell Spacer,

ADVANCED MATERIALS, Issue 4 2006
M. Grzelczak
One-dimensional nanocomposite colloids are prepared by means of electrostatic self-assembly of CdTe nanocrystals on both carbon nanotubes (CNTs) and silica-coated CNTs (see Figure). The dense coverage of these linear nanoparticle assemblies minimizes the spacing between the nanocrystals, thereby facilitating efficient electronic and energy transfer along the nanotubes. [source]

Laser-induced atomic assembling of periodic layered nanostructures of silver nanoparticles in fluoro-polymer film matrix

LASER PHYSICS LETTERS, Issue 5 2010
V.N. Bagratashvili
Abstract Fluorinated acrylic polymer (FAP) films have been impregnated with silver precursor (Ag(hfac)COD) by supercritical fluid technique and next irradiated with laser (, = 532 nm). Laser-chemically reduced Ag atoms have been assembled into massifs of Ag nanoparticles (3,8 nm) in FAP/Ag(hfac)COD films matrix in the form of periodic layered nanostructures (horizontal to film surface) with unexpectedly short period (90,180 nm). The wavelet analysis of TEM images reveals the existence of even shorter-period structures in such films. Photolysis with non-coherent light or pyrolysis of FAP/Ag(hfac)COD film results in formation of Ag nanoparticles massifs but free of any periodic nanoparticle assemblies. Our interpretation of the observed effect of laser formation of short-period nano-sized Ag nanoparticle assemblies is based on self-enhanced interference process in the course of modification of optical properties of film. (© 2010 by Astro Ltd., Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA) [source]

Multifunctional Magnetoplasmonic Nanoparticle Assemblies for Cancer Therapy and Diagnostics (Theranostics),

Photoluminescence effects on gold nano- particles modified by short single stranded DNA molecules

MATERIALWISSENSCHAFT UND WERKSTOFFTECHNIK, Issue 4 2009
O. Kysil
Gold-Nanopartikel; Einzelstrang DNA; sichtbare Photolumineszenz; Photosensor Abstract The concept for a function of gold nanoparticle photosensor based on gold nanoparticle optical properties, depending on the size and architecture of their self , assemblies, is revised from the studies of modified by short ssDNA (5.4 nm length) selected gold nanoparticle (8.6 nm diameter) assembling in biosuspensions. Biosensing effect, collective photoluminescence in visible range of different size 2D, 3D assemblies from these nanoparticles, is revealed due to their controlled assembling in biosuspesions, dependent on ssDNA conformation, that changes gold core capping and therefore a force of interparticle interaction. Nanophotosensor is characterized by intensive photoluminescence maxima in two regions of visible range for tested biosuspensions due to detected difference in the self - assemblies' architecture of gold nanoparticles with different gold core capping by the ssDNA molecules. The emission maxima are 4.2x103 pps and 4.1x104 pps in (525,780) nm and (780,920) nm regions mainly for 2D assemblies as nanowires and 3D assemblies as circle holms, correspondently, in DNA buffer suspensions with different biomolecules. The results are explained addressing photoluminescence of gold nanoparticle assemblies to system of discrete electron states in valence and conductivity bands for gold nanoparticle model. Photolumineszenz-Effekt auf Gold Nanopartikel vermittelt durch kurze Einzelstrang DNA Moleküle Das Konzept für die Funktion der Goldpartikel Nanophotosensoren basiert auf den optischen Eigenschaften der Gold Nanopartikel abhängig von der Größe und Architektur ihrer ,Self-Assemblies", und wird auf Basis von Studien von kurzen ssDNA (5.4 nm Länge) mit ausgewählten sich in Biosuspensionen versammelnden Gold Nanopartikeln (8.6 nm Durchmesser) revidiert. Der Biosensoreffekt, sichtbar durch die gesammelte Photolumineszenz im sichtbaren Spektrum von verschieden großen 2D und 3D-Aggregaten von diesen Nanopartikeln, wird wegen ihrer kontrollierten Ansammlung in Biosuspensionen, welche in Abhängigkeit zu den kurzen ssDNA Konformation, dem Ändern der monomolekularen Bedeckungsschicht des Goldkerns und somit durch eine Kraft der Teilchen-Wechselwirkung offenbart. Der Nanophotosensor ist durch zwei intensive Photolumineszenz-Maxima im Bereich des sichtbaren Spektrums für derart geprüfte Biosuspensionen wegen des meßbaren Unterschieds in der Selbstanordnung von Gold Nanopartikeln mit dem verschiedenen Goldkernbedeckungen durch die ssDNA Stränge charakterisiert: Emissionsmaxima liegen bei 4.2x103 pps und 4.1x104 pps in den Wellenlängenbereichen von (525,780) nm und (780,920) nm, jeweils hauptsächlich für 2D-Aggregate als Nanodrähte und 3D-Aggregate in kreisförmiger Anordnung in DNA-Puffersuspendierungen mit verschiedenen Biomolekülen. Die Ergebnisse werden Mithilfe der Adressierung der Photolumineszenz von Gold Nanopartikel-Aggregaten zu System von getrennten Elektronzuständen in Valenz und Leitungsbändern entsprechend den Gold Nanopartikel-Modellen erklärt. [source]

Electrically Conductive Thin Films Prepared from Layer-by-Layer Assembly of Graphite Platelets

ADVANCED FUNCTIONAL MATERIALS, Issue 7 2009
Mubarak Alazemi
Abstract Layer-by-layer (LBL) assembly of carbon nanoparticles for low electrical contact resistance thin film applications is demonstrated. The nanoparticles consist of irregularly shaped graphite platelets, with acrylamide/,, -methacryl-oxyethyl-trimethyl-ammonium copolymer as the cationic binder. Nanoparticle zeta (,,) potential and thereby electrostatic interactions are varied by altering the pH of graphite suspension as well as that of the binder suspension. Film thickness as a function of zeta potential, immersion time, and the number of layers deposited is obtained using Monte Carlo simulation of the energy dispersive spectroscopy measurements. Multilayer film surface morphology is visualized via field-emission scanning electron microscopy and atomic-force microscopy. Thin film electrical properties are characterized using electrical contact resistance measurements. Graphite nanoparticles are found to self-assemble onto gold substrates through two distinct yet overlapping mechanisms. The first mechanism is characterized by logarithmic carbon uptake with respect to the number of deposition cycles and slow clustering of nanoparticles on the gold surface. The second mechanism results from more rapid LBL nanoparticle assembly and is characterized by linear weight uptake with respect to the number of deposition cycles and a constant bilayer thickness of 15 to 21,nm. Thin-film electrical contact resistance is found to be proportional to the thickness after equilibration of the bilayer structure. Measured values range from 1.6,m,,cm,2 at 173,nm to 3.5,m,,cm,2 at 276,nm. Coating volume resistivity is reduced when electrostatic interactions are enhanced during LBL assembly. [source]

Enzyme-Responsive Nanoparticle Systems,

ADVANCED MATERIALS, Issue 22 2008
James E. Ghadiali
Abstract Inorganic nanoparticles and their accompanying diverse physical properties are now virtually in routine use as imaging tools in cell-biology. In addition to serving as excellent contrast agents, their size- and environment-dependent optical and magnetic properties can be harnessed to create enzyme biosensor devices of extremely high sensitivity, whilst circumventing the numerous technical limitations associated with traditional enzyme assays. In this Research News article we discuss recent advances in field of enzyme-responsive nanoparticle systems, where the activity of an enzyme elicits a specific response in the nanoparticle assembly to produce a signal relating to enzyme activity, focusing on three important systems: DNA-structured nanoparticles, protein kinases and proteases. [source]

Controlled Assembly of Au, Ag, and Pt Nanoparticles with Chitosan

CHEMISTRY - A EUROPEAN JOURNAL, Issue 24 2009
Min Hong
Abstract Working on the chain gang: A simple method for the controlled assembly of metal nanoparticles (Au, Ag, and Pt) into 1D chains (see figure) has been developed based on the electrostatic interaction of negatively charged carboxylic groups on the citrate ions surrounding the NPs and the positively charged chitosan polymer. A simple method for the controlled assembly of metal nanoparticles into one-dimensional chains has been developed. The chain-formation process could be accounted for by the electrostatic interaction of the negatively charged carboxylic groups on the citrate ions surrounding metal nanoparticles and the positively charged chitosan polymer. Three representative types of nanoparticles comprising Au, Ag, and Pt, respectively, have been used to illustrate the generic applicability of the proposed methodology. Facile control of the chain length of the nanoparticle assembly could be achieved by adjusting the concentrations of negatively or positively charged species. We anticipate the ready adaptability of the methodology to nanoparticles of more complex compositions. [source]

A Sensitive Fluorescence Anisotropy Method for Point Mutation Detection by Using Core,Shell Fluorescent Nanoparticles and High-Fidelity DNA Ligase

CHEMISTRY - A EUROPEAN JOURNAL, Issue 27 2007
Ting Deng Dr.
Abstract The present study reports a proof-of-principle for a sensitive genotyping assay approach that can detect single nucleotide polymorphisms (SNPs) based on fluorescence anisotropy measurements through a core,shell fluorescent nanoparticles assembly and ligase reaction. By incorporating the core,shell fluorescent nanoparticles into fluorescence anisotropy measurements, this assay provided a convenient and sensitive detection assay that enabled straightforward single-base discrimination without the need of complicated operational steps. The assay was implemented via two steps: first, the hybridization reaction that allowed two nanoparticle-tagged probes to hybridize with the target DNA strand and the ligase reaction that generated the ligation between perfectly matched probes while no ligation occurred between mismatched ones were implemented synchronously in the same solution. Then, a thermal treatment at a relatively high temperature discriminated the ligation of probes. When the reaction mixture was heated to denature the duplex formed, the fluorescence anisotropy value of the perfect-match solution does not revert to the initial value, while that of the mismatch again comes back as the assembled fluorescent nanoparticles dispart. The present approach has been demonstrated with the discrimination of a single base mutation in codon 12 of a K-ras oncogene that is of significant value for colorectal cancers diagnosis, and the wild type and mutant type were successfully scored. Due to its ease of operation and high sensitivity, it was expected that the proposed detection approach might hold great promise in practical clinical diagnosis. [source]