Number Of Nanoparticle Layers Research Articles

Chemical and Physical Properties of Photonic Noble-Metal Nanomaterials.

Colloidal noble metal nanoparticles (NPs) are composed of metal cores and organic or inorganic ligand shells. These NPs support size- and shape-dependent plasmonic resonances. They can be assembled from dispersions into artificial metamolecules which have collective plasmonic resonances originating from coupled bright and dark optical electric and magnetic modes that form depending on the size and shape of the constituent NPs and their number, arrangement, and interparticle distance. NPs can also be assembled into extended 2D and 3D metamaterials that are glassy thin films or ordered thin films or crystals, also known as superlattices and supercrystals. The metamaterials have tunable optical properties that depend on the size, shape, and composition of the NPs, and on the number of NP layers and their interparticle distance. Interestingly, strong light-matter interactions in superlattices form plasmon polaritons. Tunable interparticle distances allow designer materials with dielectric functions tailorable from that characteristic of an insulator to that of a metal, and serve as strong optical absorbers or scatterers, respectively. In combination with lithography techniques, these extended assemblies can be patterned to create subwavelength NP superstructures and form large-area 2D and 3D metamaterials that manipulate the amplitude, phase, and polarization of transmitted or reflected light.

Ultrathin Porous Hydrocarbon Membranes Templated by Nanoparticle Assemblies.

Porous polymer membranes are widely desired as catalyst supports, sensors, and active layers for separation membranes. We demonstrate that electron beam irradiation of freely suspended gold or Fe3O4 nanoparticle (NP) monolayer sheets followed by wet chemical etching is a high-fidelity strategy to template two-dimensional (2D) porous cross-linked hydrocarbon membranes. This approach, which relies on secondary electrons generated by the NP cores, can further be used to transform three-dimensional (3D) terraced gold NP supercrystals into 3D porous hydrocarbon membranes. We utilize electron tomography to show how the number of NP layers (monolayer to pentalayer) controls attenuation and scattering of the primary e-beam, which in turn determines ligand cross-link density and 3D pore structure. Electron tomography also reveals that many nanopores are vertically continuous because of preferential sintering of NPs. This work demonstrates new routes for the construction of functional nanoporous media.

Flux-pinning properties of YBa2Cu3O7−x multilayered films with Y2O3 and ZnO nanoparticle inclusions

We investigated the flux-pinning properties of YBa2Cu3O7−x (YBCO) films in which Y2O3 and ZnO nanoparticles were uniformly embedded by using the pulsed laser deposition (PLD) technique. Y2O3 and ZnO nanoparticles with average sizes of 10–30 nm and with different densities by changing the number of nanoparticle layers were introduced in a YBCO matrix in the form of a multilayered structure. The total thickness of the YBCO superconducting layers was kept to be 250 nm. Dilute doping was found to be effective for both Y2O3 and ZnO nanoparticles. For Y2O3 doping, critical current density (Jc) enhancements over a wide range of fields were obtained in 1- and 5-layer doped samples, while weak Jc enhancements and a better field dependence of Jc were found in the YBCO film with 1 layer of ZnO. Based on an analysis of surface morphology, the transition temperature (Tc), and Jc, we discuss the difference between the two types of nanoparticles as flux-pinning centers.

Multi-Layer Pt Nanoparticle Embedded High Density Non-Volatile Memory Devices

This work presents high density non-volatile memory devices by embedding multi-layers of ∼1 nm Pt nanoparticles between Al2O3 tunneling, inter-particle, and blocking dielectric layers. Up to four layers of Pt nanoparticle embedded memory devices were fabricated using a unique Tilted Target sputter deposition method. A combination of angular deposition flux and self-limiting growth process resulted in the formation of nearly mono-dispersed metal nanoparticles at room temperature allowing the fabrication of multi-layer devices without the need for further annealing. Multi-layer Pt nanoparticle embedded memory devices showed an enhanced memory window dependent on the number of nanoparticle layers. The memory window of 14.68 V and an electron charge density of 2.6 × 1013 cm−2 were obtained at ±10 V sweeping gate voltage in quad-layer Pt nanoparticle embedded memory-a twofold increase when compared to the single-layer device. We also demonstrated that asymmetrical quad-layer Pt nanoparticle embedded memory reduced an initial charging and improved the charge retention property.

Layered Hydrogen‐Bonded Nucleotide‐Functionalized CdS Nanoparticles for Photoelectrochemical Applications

CdS nanoparticles (NPs) functionalized with nucleotides were used to assemble layered NP arrays stabilized by H bonds (see scheme). The association of various nucleotides between the NPs and electrode, with subsequent sequential nucleotide linkages, allows control of the number of layers. The nucleotide-crosslinked CdS NP assemblies reveal photoelectrochemical activities; the intensity of the photocurrent increases with number of NP layers.

Creation of Submicrometer Structures Using Polymeric Nanoparticle Layers and Photolithography

This letter describes a novel route for the facile construction of mechanically robust, submicron architectures. The method couples the layer-by-layer deposition of charged polymeric nanoparticles with photopatterning and thermal processing. The merits of the method are demonstrated by the fabrication and microscopic characterization of massively dense (∼650 000 wells/cm2), ultrasmall volume (3−15 fL) well arrays. The well depth is controlled by the number of nanoparticle layers, with well depths as low as ∼4 nm obtained. The lateral dimensions of the wells, which were several microns, are defined by the photomask. Thermal processing not only further enhances the structural stability of the array but also dramatically reduces the depth of the wells. Potential applications of this preparative strategy are briefly discussed.