Formation Of Nanoparticle Arrays Research Articles

Surface-Enhanced Raman Spectroscopy (SERS) of Neonicotinoid Insecticide Thiacloprid Assisted by Silver and Gold Nanostructures.

This study expresses our results on surface-enhanced Raman spectroscopy (SERS) analyses of neonicotinoid insecticide thiacloprid, i.e., Calypso 480 SC, in quantities much smaller than usually applied in the agricultural medicine. Advanced Ag and Au nanostructures created by the thermal deposition technique on Al2O3 ceramic were applied as active substrates for SERS analyses. The minimum concentration of thiacloprid detected was 380 µM and the enhancement factor was estimated to be about 3 × 103. The intensity of the SERS peaks increased by an order of magnitude after pulsed laser annealing of the films and formation of nanoparticle arrays and the enhancement factor reached ≈104, respectively. The proposed study has direct bearing on the environment and human health by detection of small amounts or residue of harmful pollutants using a relatively cheap and easy method to produce active SERS substrates.

AFM induced self-assembling and self-healing mechanism of silicon oxide nanoparticle linear array domains templated on Moiré superlattice patterns on HOPG

Silicon oxide nanocluster suspensions were drop-cast on highly oriented pyrolytic graphite (HOPG) and investigated using ultra-high vacuum non-contact atomic force microscopy (AFM). The assembly of silicon oxide nanoparticle arrays was observed during consecutive scanning of the surface using AFM. The patterns and alignments of the nanoparticle arrays were consistent with templating on a Moiré pattern in the top layers of the HOPG substrate. By halting and restarting the scanning process it was shown that the formation of nanoparticle arrays was driven by the AFM scan itself. Vacancy defects identified within the nanoparticle arrays were found to fill over time with nanoparticles; it was demonstrated that diffusion was preferred along the symmetry lines. This ‘self-healing’ mechanism was also shown to be driven by the AFM scanning. The recovery of defects within the arrays, and other observations of array dynamics, implied that the nanoparticle arrays had liquid-like qualities.

Evaporating metal nanocrystal arrays

Anodic aluminum oxide (AAO) substrates with a self-ordered triangular array of nanopores provide the means to fabricate multiple forms of nano materials, such as nanowires and nanoparticles. This study focuses on nanostructures that emerge in thin films of metals thermally evaporated onto the surface of AAO. Previous work showed that films of different evaporated metals assume dramatically different structures, e.g. an ordered triangular array of nearly monodisperse nanoparticles forms for lead (Pb) while a polycrystalline nanohoneycomb structure forms for silver (Ag). Here, we present investigations of the effects of substrate temperature and deposition angle that reveal the processes controlling the nano particle array formation. Our findings indicate that arrays form provided the grain nucleation density exceeds the pore density and the atomic mobility is high enough to promote grain coalescence. They introduce a method for producing films with anisotropic grain array structure. The results provide insight into the influence of substrate nano-morphology on thin film growth energetics and kinetics that can be harnessed for creating films with other novel nano-structures.

Silver Nanoparticle Arrays Prepared by In Situ Automatic Reduction of Silver Ions in Mussel‐Inspired Block Copolymer Films

Block copolymer phase separation has been employed to form templates for the fabrication of nanoscale patterns of metals due to their characteristic size scales that range from several nanometers to tens of nanometers. In the present work, poly(vinyl catechol‐block‐styrene) PVCa‐b‐PSt synthesized with various compositions forms unique microphase‐separated structures. Silver nanoparticles are spontaneously formed inside of the PVCa phases due to the reductive properties of the catechol moieties. The alignment and formation of silver nanoparticle arrays is successfully achieved without the need for high‐temperature thermal treatment or chemical reduction processes. The present system can be applied to the formation of nanoparticle arrays with a wide variety of metals by control of their arrangement. image

Synthesis of an embedded metal nanoparticle planar assembly by low-energy ion irradiation of a thin discontinuous metal film sandwiched in silica

Synthesis of a planar assembly of metal nanoparticles embedded in silica by low-energy ion irradiation is presented here. Argon ions of 350 keV were used to irradiate SiO2/Au/SiO2 and SiO2/Ag/SiO2 tri-layered films, with oxide thicknesses of 40 nm and metal layer thickness of 2 nm, to synthesize well isolated nanoparticles without the need of annealing. The nanoparticles have an average diameter of about 6 nm as revealed by transmission electron microscopy. Simulations by three-dimensional kinetic lattice Monte Carlo were performed to understand the ion-induced nanoparticle array formation from the initially percolated as-deposited metal layer embedded in the silica matrix.

Reorganization Induced by Silver Salt Reduction Inside a Mesostructured Block Copolymer Silica Film

Block copolymer self-assembly can be used to get a noble metallic nanoparticle array. The silver nanoparticle array formation inside a mesostructured silica film with the triblock copolymer (PEO)106(PPO)70(PEO)106 (F127) has been studied using Grazing Incidence Small-Angle X-ray Scattering (GISAXS), TEM, and X-ray diffraction analyses. Mesostructure organization essentially occurs during the sodium borohydride reduction process used to form silver nanoparticles. The well-known orthorhombic order, Fmmm space group, appears with (020)orthorhombic plan parallel to the substrate. Such reorganization is explained by the silver ion diffusion occurring along preferential directions toward the film surface. These metallic nanostructures could be potentially used in surface-enhanced Raman scattering, catalysis, or optical devices.

Biological Crystallization of Self-Aligned Iron Oxide Nanoparticles

Crystal growth and magnetic behavior of iron oxide nanoparticles assembled with biomolecules have been investigated. The nanoparticles assembled with trypsin molecules exhibit superparamagnetism at room temperature with blocking temperature (approximately 80 K) significantly lower than those without trypsin (approximately 140 K). This is attributed to reduced magnetostatic couplings between particles due to increased distance between particles separated by trypsin molecules. Moreover, the synthesized nanoparticle-biomolecule assemblies consist of a unique one-dimensional self-assembled arrays of nanoparticles found by structural analysis using transmission electron microscopy. The moiré fringes observed from the particle arrays indicate that the particles are aligned with slight misorientation of their crystallographic axes. Such an unusual formation of nanoparticle arrays may be relevant to specific ligand sites in trypsin molecules and the magnetostatic interparticle couplings.

Microtubule Templated Synthesis of Inorganic Nanomaterials

AbstractProtein microtubules (MTs) have been used as templates for the biomimetic synthesis of metal oxide, metal sulfide, and metallic nanomaterials. These materials were coated onto MTs via three distinct synthetic pathways: metal ion hydrolysis which yielded iron oxide or zinc oxide-coated microtubules, metal ion/sulfide co-precipitation which yielded zinc sulfide coated MTs, and metal ion reduction which yielded gold-coated MTs. The growth process of metal oxide coating involves heterogeneous nucleation on the MT surface and produces even, microcrystalline films. Metal sulfide and metal coating initially involves the formation of nanoparticle arrays that decorate the MT surface and can eventually lead to either semi- or fully continuous coatings.

Overview of Nanoparticle Array Formation by Wet Coating

We give a concise overview of nanoparticle array formation by wet coating techniques including patterned assembly, surface modification of nanoparticles, rheology, assembling dynamics, and function of nanoparticle arrays. For the rapid fabrication of large-area and/or patterned nanoparticle arrays, wet coating techniques, such as spin, dip, spray, gravure, slot, roll, and ink-jet coating, are promising ways for practical use in combination with an evaporation-driven self-assembly technique. We have also referred to the concept of array formation via surface modification.

Formation of Nanoparticle Arrays at the Interlayer of Aqueous Phosphate Bilayers

Abstract Nanoparticle arrays were obtained by simply mixing anionic bilayer membranes and cationic, quaternary ammonium-stabilized gold nanoparticles under ultrasonication. The particles were immobilized densely into the hydrophilic interlayers of the dispersed lamellar structures and formed quasi one-dimensional structure.

Interplay between Hole Instability and Nanoparticle Array Formation in Ultrathin Liquid Films

When dilute solutions of nearly monodisperse (3−5-nm diameter) passivated metal nanoparticles are evaporated on a solid substrate (a transmission electron microscopy grid), the resulting submonolayer structures are annular ringlike arrays. We describe here a theoretical mechanism whereby the growth of holesdry areas of the solid surface which is otherwise wet by solventis conjectured to be responsible for the formation of these novel close-packed two-dimensional (2D) arrays. Each annular ring is argued to arise from the pinning of the rim of an opening hole by a sufficient number of particles. Hole nucleation in this ultrathin-film system can occur due to two independent driving forces: evaporation (volatile hole nucleation) and disjoining pressure (nonvolatile hole nucleation). The cases are first presented separately, in an appropriate analytical theory, and are subsequently treated jointly in the context of a simulation. We investigate in particular the effect of competing time scales (for hole nuclea...