Nanoparticle Self Research Articles

Nanoparticle Self Diffraction in the TEM: A proposal

Nanoparticle Self Diffraction in the TEM: A proposal

Anionic Hyperbranched Amphiphilic Polyelectrolytes as Nanocarriers for Antimicrobial Proteins and Peptides.

This manuscript presents the synthesis of hyperbranched amphiphilic poly (lauryl methacrylate-co-tert-butyl methacrylate-co-methacrylic acid), H-P(LMA-co-tBMA-co-MAA) copolymers via reversible addition fragmentation chain transfer (RAFT) copolymerization of tBMA and LMA, and their post-polymerization modification to anionic amphiphilic polyelectrolytes. The focus is on investigating whether the combination of the hydrophobic characters of LMA and tBMA segments, as well as the polyelectrolyte and hydrophilic properties of MAA segments, both distributed within a unique hyperbranched polymer chain topology, would result in intriguing, branched copolymers with the potential to be applied in nanomedicine. Therefore, we studied the self-assembly behavior of these copolymers in aqueous media, as well as their ability to form complexes with cationic proteins, namely lysozyme (LYZ) and polymyxin (PMX). Various physicochemical characterization techniques, including size exclusion chromatography (SEC) and proton nuclear magnetic resonance (1H-NMR), verified the molecular characteristics of these well-defined copolymers, whereas light scattering and fluorescence spectroscopy techniques revealed promising nanoparticle (NP) self- and co-assembly properties of the copolymers in aqueous media.

Ambient ammonia production via electrocatalytic nitrite reduction over MoO2 nanoparticles self-supported on molybdenum plate

Electrocatalytic reduction of nitrite (NO2–) is an environmentally friendly method for ambient ammonia (NH3) production, and the development of high–efficiency electrocatalysts is in urgent demand. Herein, we demonstrated that MoO2 nanoparticles self–supported on a molybdenum plate (MoO2/MP) could act as an excellent catalyst for the conversion of NO2– to NH3. The optimized catalyst can achieve an impressive NH3 yield of 8678.4 ± 187.4 μg h–1 cm–2 with high Faradaic efficiency of 94.5 ± 0.2 % at −0.8 V in the solution of 0.5 M Na2SO4 and 0.1 M NO2–, along with preferable durability. Additionally, density functional theory calculation reveals that the MoO2 (1¯11) surface has a high activity for NO2– reduction, with 0.38 eV as the potential determining step (*NO2 to NO2H), as well as severe suppress hydrogen evolution.

Surface, Interface, and Temperature Effects on the Phase Separation and Nanoparticle Self Assembly of Bi-Metallic Ni0.5Ag0.5: A Molecular Dynamics Study.

Classical molecular dynamics (MD) simulations were used to investigate how free surfaces, as well as supporting substrates, affect phase separation in a NiAg alloy. Bulk samples, droplets, and droplets deposited on a graphene substrate were investigated at temperatures that spanned regions of interest in the bulk NiAg phase diagram, i.e., miscible and immiscible liquid, liquid-crystal, and crystal-crystal regions. Using MD simulations to cool down a bulk sample from 3000 K to 800 K, it was found that phase separation below 2400 K takes place in agreement with the phase diagram. When free surface effects were introduced, phase separation was accompanied by a core-shell transformation: spherical droplets created from the bulk samples became core-shell nanoparticles with a shell made mostly of Ag atoms and a core made of Ni atoms. When such droplets were deposited on a graphene substrate, the phase separation was accompanied by Ni layering at the graphene interface and Ag at the vacuum interface. Thus, it should be possible to create NiAg core-shell and layer-like nanostructures by quenching liquid NiAg samples on tailored substrates. Furthermore, interesting bimetallic nanoparticle morphologies might be tuned via control of the surface and interface energies and chemical instabilities of the system.

Advanced visible-light photocatalytic property of biologically structured carbon/ceria hybrid multilayer membranes prepared by bamboo leaves

Biologically structured carbon/cerium dioxide materials are synthesized by biological templates. The microscopic morphology, structure and the effects of different oxidation temperatures on materials are characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) ultraviolet-visible light spectrum (UV–Vis) and X-ray Photoelectron Spectroscopy (XPS). Moreover, by splitting water under visible light irradiation, the hydrogen production is measured to test the photocatalytic property of these materials. The results show that materials made with bamboo biological templates which are immersed in 0.1molL−1 of cerium nitrate solution, then carbonizated in nitrogen (700°C) and oxidized in air (500–600°C), can obtain the biological structure of bamboo leaves. The product is in the composition of hybrid multilayer membrane, which one is carbon membrane form plant cell carbonation and another is ceria membrane by nanoparticle self assembly. The best oxidation temperature is 550°C and the band gap of carbon/cerium dioxide materials synthesized at this optimum oxidation temperature could be reduced to 2.75eV. After exposure to visible light for 6h, the optimal hydrogen production is about 302μmolg−1, which is much higher than that of pure CeO2.

Self-assembly behaviour of bismuth oxide nanoparticles assisted by oleylamine

Bi2O3 nanoparticles are prepared by using a facile solution-based thermal decomposition method assisted by oleylamine. These Bi2O3 nanoparticles self assemble into nanobelts. The reaction time and temperature affect self-assembly behaviour of the Bi2O3 nanoparticles. Increasing the reaction time or temperature results in the larger size of nanoparticles, which leads to failure of formation of nanobelts. It is illustrated that oleylamine and the size of nanoparticles play key roles in the self-assembly of nanoparticles. Based on the experimental results, a formation mechanism of the self-assembled nanobelts was proposed and this method may be extended to fabrication of other metal oxide nanobelts.

An EGFR targeting nanoparticle self assembled from a thermoresponsive polymer

AbstractBACKGROUNDDecorating nanoparticles with proteins, antibodies and antibody fragments allows highly specific targeting to selected cells for improved delivery of therapeutics and diagnostics. A range of particles have previously been trialled in drug delivery including liposomes, dendrimers, hydrogels and inorganic particles. Polymer nanoparticles can be rationally designed and self‐assembled with control over particle size, morphology, charge and shape, allowing for optimization of drug delivery. However, post‐functionalization of particles with antibodies or proteins can influence the self‐assembly process and creates challenges in maintaining bioactivity.RESULTSAn EGFR‐targeting scFv antibody fragment has been integrated as a hydrophilic moiety, and through self‐assembly driven by a thermoresponsive polymer, formed antibody‐targeted polymeric nanoparticles (immunoparticles) of approximately 320 nm in diameter. The binding of the scFv to native EGFR on MDA MB 468 cells and to recombinant EGFR was determined using flow cytometry and surface plasmon resonance respectively. Conjugation of the scFv to the thermoresponsive polymer did not compromise the binding to EGFR. Furthermore, cross‐linking the scFv with glutaraldehyde to stabilize the immunoparticle did not impact the binding of the particle to EGFR.CONCLUSIONThe temperature‐induced self‐assembly of immunoparticles from antibody‐conjugated polymers provides a novel method to prepare targeted nanoparticles. This methodology further provides a rapid and versatile way to build immunoparticles with multi‐targeting capability by combining different types of scFv‐PNIPAM conjugates targeting different receptors. © 2014 Society of Chemical Industry

A Novel Strategy for Synthesis of Gold Nanoparticle Self Assemblies

Gold nanoparticle self assemblies are one-dimensional structures of gold nanoparticles. Gold nanoparticle self assemblies exhibit unique physical properties and find applications in the development of biosensors. Methodologies currently available for lab-scale and commercial synthesis of gold nanoparticle self assemblies are complex. These methods are often multistep involving linker nanoparticle conjugation steps and external stimuli treatment steps. Here, we present a simple method for synthesis of gold nanoparticle self assemblies. The method involves surfactant-free synthesis of gold nanoparticles, washing of gold nanoparticles with distilled water and irradiation of gold nanoparticles with glow discharge plasma. Thus synthesized gold nanoparticle self assemblies were characterized using electron microscopy and ultraviolet and visible light spectroscopy. Results show that washing with distilled water and irradiation with glow discharge plasma induces assembling of gold nanoparticles into multimers, chain-like structures and networks. Our synthesis method is unique in that it provides full control on the extent of self assembly and at the same time is simple and economical. Our synthesis method facilitates lab-scale and commercial synthesis of gold nanoparticle self assemblies, which, in turn, will promote the application of self assembled gold nanoparticles in the development of novel biosensors, drug-delivery platforms, lab-on-a-chip platforms and a variety of other nano-scale medical devices. Keywords: Chain-like structure and nanoparticle network, gold, multimer, nanoparticle, self assembly.

Prussian Blue Nanoparticles Self Assembling on Electrochemically Reduced Graphene Oxide Modified GC Electrode for Sensitive Hydrogen Peroxide Detection

AbstractA facile, fast, and convenient route was suggested for the fabrication of Prussian blue nano particles (PBNPs) assembled on reduced graphene oxide (RGO) modified glassy carbon electrode (PBNPs|RGO|GCE). RGO was electrodeposited on the surface of GCE and the prepared RGO|GCE was immersed into a ferric‐hexacyanoferrate(III) solution and PBNPs were assembled on the RGO|GCE for a certain period of time. The PBNPs film thickness can be easily controlled by adjusting the assembling duration. The developed PBNPs|RGO|GCE was successfully used for determining hydrogen peroxide, with a linear response over the concentration range 0.5‐400 μM, a good accuracy and precision, detection limit 0.44 μM, and sensitivity 1168 mA M−1 cm−2.

Self-assembly of core–shell nanoparticles for self-healing materials

New core–shell nanoparticles were synthesized by grafting a poly(acrylate amide) shell onto a cross-linked polystyrene nanoparticle (NP) via atom transfer radical polymerization (ATRP). The core–shell NPs self assemble into self-healing materials in which the dynamic hydrogen-bonding shell confers self-healing properties while the hard cross-linked core provides stiffness.

Palladium Nanoparticles Formed on Titanium Silicate ETS-10

We report that surface templated and supported palladium nanoparticles self assemble on ETS-10 type molecular sieve surfaces by simple exchange and activation procedures in the absence of a reductant. This procedure is similar to the one previously reported for silver nanoparticle self assembly on ETS-10. We observed a bimodal distribution with particle sizes ranging from 2-5 and 15-30 nm. This simple, economical method generates high concentrations (approximately 12 wt% of total composite) of uniform, metallic palladium nanoparticles that are multiply twinned and thermally stable making them potentially unique for advanced catalytic and electronic applications.

Gold nanoparticle superlattices as functional solids for concomitant conductivity and SERS tuning

Mercaptosuccinic acid protected gold nanoparticles (Au@MSA) self assemble to form superlattice (SL) crystals at the air-water interface. These have been used for gas adsorption. The current-voltage (I-V) characteristics of the SL film with embedded SL crystals, obtained by four probe measurements, show Ohmic conduction. The conductance observed was proportional to the polarizability of the adsorbed gases. The current through the SL decreases on adsorption of the gas along with decrease in the SERS intensity of a probe molecule from the crystals. We rationalise our observation of the linear dependence of the conductance on the polarizability of the adsorbed gas using a simple model calculation. Variation of the conductance may be useful in designing electrical switches operating at the nanometre length scales.

Fast polymer semiconductor transistor by nano-particle self assembly

Polymer semiconductor based field effect transistors promise low cost electronics over rigid and flexible large area substrates using fabrication techniques such as ink-jet printing. However, the low mobility of carriers in these semiconductors does not permit high performance electronics. A primary means to achieve higher speed in spite of the low carrier mobility is to reduce feature size, particularly channel length, of the field effect transistors. In this paper, we use the controlled coffee stain effect in a silver nano-particle colloid along with ink-jet printing to develop a process which helps reduce field effect transistor channel length to about 1–10 μm and improve transistor speed.

Controlling the assembly of hydrophobized gold nanoparticles at the air–water interface by varying the interfacial tension

Controlled assembly is the key to harness the nanoscale properties of nanoparticles in most technological applications and it has been an important challenge as it leads to the manipulation of interparticle properties. The present work depicts the control of the assembly of nanoparticles in the monolayers by evaporation kinetics and particle interactions at the air–liquid interface. In the presence of attractive particle–particle and particle–monolayers interactions, nanoparticles self assemble into a superlattice structure upon drying from a colloidal suspension on to the preformed lipid monolayers. This self-assembly mechanism produces monolayers with long-range ordering. However, rapid dewetting and high rate of evaporation can significantly undermine the extent of ordering. Using gold nanoparticles as vehicles for experimentation and by changing the monolayers and solvent, we here demonstrate that the extent of ordering of nanoparticles can be controlled.

Self assembled nanoparticle aggregates from line focused femtosecond laser ablation

In this paper we present the use of a line focused femtosecond laser beam that is rastered across a 2024 T3 aluminum surface to produce nanoparticles that self assemble into 5-60 micron diameter domed and in some cases sphere-shaped aggregate structures. Each time the laser is rastered over initial aggregates their diameter increases as new layers of nanoparticles self assemble on the surface. The aggregates are thus composed of layers of particles forming discrete layered shells inside of them. When micron size aggregates are removed, using an ultrasonic bath, rings are revealed that have been permanently formed in the sample surface. These rings appear underneath, and extend beyond the physical boundary of the aggregates. The surface is blackened by the formation of these structures and exhibits high light absorption.

Silver nanoparticles self assembly as SERS substrates with near single molecule detection limit

Highly sensitive SERS substrates with a limit of detection in the zeptomole (for Nile blue A and oxazine 720) range were fabricated through a bottom-up strategy. Ag nanoparticles (Ag NPs) were self-assembled onto glass slides by using 3-mercaptopropyltrimethoxysilane (MPTMS) sol-gel as linker. The substrates were characterized by UV-Vis and AFM after each deposition of Ag NPs. It was found that the glass slide presented just a few Ag NPs aggregates scattered throughout the surface after just one deposition. The glass surface was gradually covered by a homogeneous distribution of Ag NPs aggregates as the deposition number increased. Surface-enhanced Raman scattering (SERS) of the substrates was examined at different numbers of Ag NPs deposition using nile blue A and oxazine 720 as probe molecules and two laser excitations (632.8 nm and 785 nm). Optimum SERS was observed after six depositions of Ag NPs. SERS mapping indicated that at lower deposition numbers (less than 3 Ag NPs depositions) the substrates presented a few SERS "hot-spots" randomly distributed at the surface. After 7 Ag NPs depositions, spatial distribution of the SERS signal followed a Gaussian statistics, with a percent relative standard deviation (RSD%) of approximately 19%. In addition, the sample-to-sample reproducibility of the SERS intensities under both laser excitations was lower than 20%. It was also found that these substrates can provide giant Raman signal enhancement. At optimum conditions and with a 632.8 nm laser, the signal from an estimated of only approximately 44 probe molecules (100x objective) can still be detected.

Graphite Nanoparticle Self Assembly on Gold

not Available.

Self-Assembly of Unusual Nanoparticle Crystals

Regular particles of any size, from atoms to colloids, can form crystals. Manipulation of their charges allows control of crystal structure and can be extended to nanoparticle self assembly.

Silver Nanoparticles Self Assembled on HOPG: Unusual Behavior as Probed by Scanning Tunneling Microscopy

The controlled construction of nanostructures on solid surfaces for technological applications depends primarily on a deep understanding of the physical chemistry of the interface. Several methods have been devised to grow metallic nanostructures on solid surfaces, notably physical vapor deposition and electrodeposition. The electrochemical method led to the creation of a very promising technology called Electrochemical Step Edge Decoration (ESED) by the Penner group in Irvine, Ca. In this method, metallic nano and mesowires are built through electrochemical deposition on the step edges of the basal plane of Highly Oriented Pyrolytic Graphite (HOPG) [1]. The proposed growth mechanism is based on the Terrace-Ledge-Kink (TLK) model [2], in which the foreign adatoms nucleate the electrochemically induced growth of nanoparticles in the lower plane of step edges. White and collaborators [3], while studying the stability of gold nanoparticles electrodeposited on HOPG, noticed the preferential nucleation on the upper plane of step edges in stark opposition to the TLK model. They proposed that this preferential deposition is associated with a slippage of the atomic layer near the edge. This proposition indicates that the surface in the upper plane near the edge will present a decrease in the atomic distance in the plane, disrupting the registry with the underlying plane. To further assess this proposition we have devised another experimental approach where, instead of electrodepositing foreign adatoms for nucleation and growth, we deposited fully formed silver nanoparticles on HOPG through a Self Assembly mechanism and studied its spatial distribution. Through this approach, we intend to study the surface mobility of nanoparticles, as opposed to atomic species as studied in electrochemical deposition.

Si Nanoparticle Synthesis and Self – Organization

ABSTRACTSi nanoparticle linear arrays have been produced by pulsed KrF laser irradiation in inert atmospheres. The Si nanoparticles have a Gaussian size distribution with a mean diameter of 2.9 nm and a FWHM of 2 nm. The self – organized lines are spaced at a distance approximately equal to the laser beam wavelength, λ. The evolution of this self – organization process and that of laser – induced periodic surface structures (LIPSS) are closely related. The nanoparticles scatter light that interferes with the incident light. Similar to LIPSS, the inhomogeneous deposition of laser light due to this interference pattern created at the surface drives the particle formation and clustering. A detailed study of the clustering formation as a function of the laser pulses is presented.