Grafted 2D Assembly of Colloidal Metal Nanoparticles for Application as a Variable Capacitor

Abstract

2D assemblies of monodisperse metal particles with controlled size in the nanometer range show considerable advantages in various applications of nanophysics: surface-plasmon resonance, [1] magnetic properties for ultrahigh-density media storage, [2] transport properties, [3] and for electronic devices, such as new flash memories, [4] and chemical sensors. [5] For all these solid-state applications, chemical synthesis has proven to lead to a very good control of particle size and shape. Moreover, the chemical synthesis of nanoparticles has the advantages of simplicity and low cost with respect to physical approaches. Monodisperse metal particles with a mean size tailored in the nanometer range can be produced by several chemical reactions, such as the reduction of metal salts or the decomposition of organometallic precursors.[6] Furthermore, 3D and 2D superlattices were produced from a solution of coated metal particles with surfactants after evaporation of the solvent. [7] The organization of such particle arrays depends on several factors such as the length of the alkyl chain and the nature of the surface on which the particles are deposited. Long-range ordered 2D arrays of alkanethiolate-coated gold nanoparticles have been obtained on a silicon nitride membrane, however, an excess of thiol and a slow evaporation rate are needed. [8] Even without the excess of organic molecules that may be inappropriate for some applications, it generally remains difficult to obtain reproducible 2D dense arrays of nanoparticles without the local formation of 3D aggregates. An alternative way to get 2D arrays consists of grafting nanoparticles on chemically modified surfaces. The silanization of oxide surfaces with amino-or mercapto-silane is one of the most studied methods for this purpose.[9] The covalent immobilization of gold colloids onto self-assembled monolayers (SAMs) has also been proposed.[10] Metal nanoparticles/polyelectrolyte ultrathin films can be grown as well by layer-by-layer self-assembly methods through electrostatic interactions.[11]Several studies dealing with the electrochemical properties of coated metal nanoparticles in solution showed that monodispersed alkanethiolate-protected gold nanoparticles exhibited quantized charging characteristics.[12] Such molecular-like capacitor characteristics were observed for other metals provided very small particle mean size and very low standard deviation of the size distribution were obtained.[13] Conversely, only very few studies deal with the use of metal nanoparticles prepared by chemistry for the elaboration of solid-state devices. We report a new application of 2D assemblies of metal nanoparticles in the field of electronics. We describe the elaboration and the transport properties of junctions, the structure of which is given in Figure 1. It consists of a 2D assembly of conducting nanoparticles embedded in a thin insulating layer of a plane capacitor. The left dielectric barrier is thin enough to allow a tunnel current to pass through when the DC voltage is a...

Ionic Strength-Controlled Deposition of Charged Nanoparticles on a Solid Substrate

“…Two-dimensional structures consisting of metallic (Ag, Au) , or semiconductor (CdSe, CdS) , nanoparticles (NPs) have attracted considerable scientific attention because of their potential applications in various fields, such as solar cells, , sensing, light-emitting devices, , storage media, , photodetectors, semiconductor nanorod epitaxial growth, electrode modification, corrosion protection, antireflective films, nanosphere lithography, or heterogeneous catalysis . At present, such coatings can be prepared by several well-established methods, including the Langmuir–Blodgett technique, electrodeposition, spin-casting, drop-casting, dip-casting, grafting, contact printing, or the sol–gel technique . All these methods have some drawbacks, such as they require special equipment, they are confined to a limited set of surfaces, or they can be used on flat or small-sized areas.…”

FTIR and XPS Study of Pt Nanoparticle Functionalization and Interaction with Alumina

“…The transport properties of such capacitors rely on Coulomb blockade in the 2D nanoparticle assembly . The successful combination of physical and chemical means for the realization of variable capacitors has been shown recently . The first results were obtained with 3 nm ruthenium particles, but the next challenge is to lower the particle size to below 1.5 nm in order to increase the working temperature up to room temperature …”

“…22 The successful combination of physical and chemical means for the realization of variable capacitors has been shown recently. 23 The first results were obtained with 3 nm ruthenium particles, 23 but the next challenge is to lower the particle size to below 1.5 nm in order to increase the working temperature up to room temperature. 22 The integration of "chemical particles" in solid state devices for electronic applications requires not only control over their mean size and the precise study of their chemical environment as for heterogeneous catalysis but also control over their organization in 1D, 2D, or 3D arrays onto substrates.…”

Light-Controlled Swarming and Assembly of Colloidal Particles

“…For instance, Ag 3 PO 4 microparticle swarms exhibit expansion and contraction with the addition and removal of NH 3 , Pt–Au nanowire motor swarms exhibit overall migration under the control of ultrasounds, and the superparamagnetic particle swarms can perform rolling with the cooperative control of ultrasounds and magnetic fields [ 30 , 36 , 41 ]. Nowadays, the exotic swarming and assembly of CPs motivate intensive endeavors for their applications, such as variable capacitors [ 42 ], drug delivery [ 43 , 44 ], biological detection and repair [ 32 , 45 ], targeted diagnosis and therapy [ 46 ], magnetic resonance imaging [ 47 ], etc.…”