Search query: densely packed arrays of metallic nanoparticles

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abstract: For the application of single walled carbon nanotubes (SWNTs) in nanoelectronic devices, techniques to obtain horizontally aligned semiconducting SWNTs (s SWNTs) with higher densities are still in their infancy. We reported herein a rational approach for the preferential growth of densely packed and well aligned s SWNTs arrays using oxygen deficient TiO2 nanoparticles as catalysts. Using this approach, a suitable concentration of oxygen vacancies in TiO2 nanoparticles could form by optimizing the flow rate of hydrogen and carbon sources during the process of SWNT growth, and then horizontally aligned SWNTs with the density of 10 tubes/mm and the s SWNT percentage above 95% were successfully obtained on ST cut quartz substrates. Theoretical calculations indicated that TiO2 nanoparticles with a certain concentration of oxygen vacancies have a lower formation energy between s SWNT than metallic SWNT (m SWNT) thus realizing the preferential growth of s SWNT arrays. Furthermore, this method can also be extended to other semiconductor oxide nanoparticles (i.e. ZnO, ZrO2 and Cr2O3) for the selective growth of s SWNTs, showing clear potential to the future applications in nanoelectronics.
author_names: Lixing Kang

Yue-hui Hu

Lili Liu

Juanxia Wu

Shucheng Zhang

Qiuchen Zhao

Feng Ding

Qingwen Li

Jin Zhang
title: Growth of close packed semiconducting single walled carbon nanotube arrays using oxygen deficient TiO2 nanoparticles as catalysts.
venue: Nano letters
year: 2015

abstract: This chapter is an overview of size and concentration effects on electrodynamic coupling in two dimensional densely packed arrays of metallic nanospheres in the frequency range of the surface plasmon resonance (SPR) Our theoretical analysis is based on the statistical theory of multiple scattering of waves. We show that concentration effects, such as the enhanced long wavelength transmission of light and the strong resonance quenching of transmission, are effectively interpreted in terms of constructive and destructive interference of waves incident on and scattered by a monolayer of closely packed submicrometer plasmonic particles. The concentration SPR red shift observed in the case of dipole metal nanoparticles is highly sensitive to the matrix refractive index and results from lateral near field couplings. We also demonstrate phenomena caused by a strong plasmonic photonic confinement in multilayered metal dielectric nanostructures consisting of densely packed monolayers. For example, we show that employing the size and/or concentration gradient of dipole metallic nanoparticles in a quarter wavelength multilayered system allows one to achieve an almost total absorbance.
author_names: A N Ponyavina

S M Kachan
title: Plasmonic spectroscopy of 2D densely packed and layered metallic nanostructures
year: 2011

abstract: A self assembly template with a photoreduction agent embedded along mesostructured silicate surfactant channels is prepared at the air water interface. The unique template allows uniform and continuous uptake of metallic precursors into the silicate surfactant channels from the solution subphase. Upon UV irradiation, the metallic precursors result in near monodisperse nanoparticles homogeneously arrayed in the mesostructured polyoxometalated silicate surfactant (PSS) channels until saturation. With three dimensionally densely packed Au NPs of ca. 1.7 nm in the PSS template, hence a very high number density of surface enhanced Raman scattering (SERS) hot spots and large absorptive volume, we show that impressive SERS can be measured with 4 nitrothiophenol adsorbed to Au NPs@PSS.
author_names: Shan-Chi Kuo

Jin-Jia Tasi

Junshou Li

Zheng-Hui Hou

Cheng-Han Li

U-Ser Jeng

Ying Huang Lai
title: Enhancement of surface enhanced Raman scattering activity of Au nanoparticles through the mesostructured metallic nanoparticle arrays
year: 2014

abstract: A novel one trough synthesis via an air water interface is demonstrated to provide hexagonally packed arrays of densely spaced metallic nanoparticles (NPs) In the synthesis, a mesostructured polyoxometalate (POM) silicatropic template (PSS) is first self assembled at the air water interface; upon UV irradiation, anion exchange cycles enable the free floating PSS film to continuously uptake gold precursors from the solution subphase for diffusion controlled and POM site directed photoreduction inside the silica channels. NPs 2 nm can hence be homogeneously formed inside the silica surfactant channels until saturation. As revealed via X ray diffraction, small angle X ray scattering (SAXS) grazing incidence SAXS, and transmission electron microscopy, the Au NPs directed by the PSS template are arrayed into a 2D hexagonal lattice with inter channel spacing of 3.2 nm and a mean along channel NP spacing of 2.8 nm. This corresponds to an ultra high number density (1019 NPs cm 3) of narrowly spaced Au NPs in the Au NP@PSS composite, leading to 3D densely deployed hot spots along and across the mesostructured POM silica channels for surface enhanced Raman scattering (SERS) Consequently, the Au NP@PSS composite exhibits prominent SERS with 4 mercaptobenzoic acid (4 MBA) adsorbed onto Au NPs. The best 4 MBA detection limit is 5 nm, with corresponding SERS enhancement factors above 108.
author_names: Ying Huang Lai

Shiaw-Woei Chen

Michitoshi Hayashi

Ying Jen Shiu

Chiao-Cheng Huang

Wei-Tsung Chuang

Chun-Jen Su

Hu-Cin Jeng

Jhe-Wei Chang

Yao-Chang Lee

An Chung Su

Chung-Yuan Mou

U-Ser Jeng
title: Mesostructured Arrays of Nanometer spaced Gold Nanoparticles for Ultrahigh Number Density of SERS Hot Spots
year: 2014

abstract: The design of achromatic optical components requires materials with high transparency and low dispersion. We show that although metals are highly opaque, densely packed arrays of metallic nanoparticles can be more transparent to infrared radiation than dielectrics such as germanium, even when the arrays are over 75% metal by volume. Such arrays form effective dielectrics that are virtually dispersion free over ultra broadband ranges of wavelengths from microns up to millimeters or more. Furthermore, the local refractive indices may be tuned by altering the size, shape, and spacing of the nanoparticles, allowing the design of gradient index lenses that guide and focus light on the microscale. The electric field is also strongly concentrated in the gaps between the metallic nanoparticles, and the simultaneous focusing and squeezing of the electric field produces strong 'doubly enhanced' hotspots which could boost measurements made using infrared spectroscopy and other non linear processes over a broad range of frequencies.Designing effective dielectrics in a broad range of the spectrum is of huge interest. Here, the authors demonstrate how transparent effective dielectrics can be constructed from dense arrays of metallic nanoparticles and can result in being more transparent than real dielectrics renowned for their transparency.
author_names: Samuel Palmer

Xiaofei Xiao

Nicolas Pazos-Perez

Luca Guerrini

Miguel A Correa-Duarte

Stefan A Maier

Richard V Craster

Ramon A Alvarez-Puebla

Vincenzo Giannini
title: Extraordinarily transparent compact metallic metamaterials
venue: Nature Communications
year: 2019

abstract: We performed synthesis and investigated the self assembly properties of gold nanoparticles (NPs) with covalently attached bolaamphiphilic ligands (B AuNPs) The judiciously designed coating rendered the NPs amphiphilic and induced their self assembly. The B AuNPs formed ordered two dimensional structures over large areas upon simple drop casting. The films exhibited an uncommon and applicable topography, consisting of densely packed rings of inner diameter of around 30 nm, with the B AuNPs at the rim and an empty interior. We introduced and proved experimentally an explanation of how the structures were formed. The model involved elements of geometric packing and ligand reorganization. Upon contact with the hydrophilic surface, ligands rearranged at the surface of the metallic cores of the B AuNPs so that the bolaamphiphilic moieties (constituting ca. 50% of the coating) were in proximity to the surface, while the hexanethiol moieties moved away from it. The described mechanism is of general relevance for.
author_names: Jan Paczesny

Michal M Wojcik

Krzysztof Sozanski

Kostyantyn Nikiforov

Carsten Tschierske

Annemarie Lehmann

Ewa Gorecka

Jozef Mieczkowski

Robert Holyst
title: Self Assembly of Gold Nanoparticles into 2D Arrays Induced by Bolaamphiphilic Ligands
year: 2013

abstract: We use evaporation within a microfluidic device to extract the solvent of a (possibly very dilute) dispersion of nanoparticles and concentrate the dispersion until a solid made of densely packed nanoparticles grows and totally invades the microfluidic geometry. The growth process can be rationalized as an interplay between evaporation induced flow and kinetic and thermodynamic coefficients which are system dependent; this yields limitations to the growth process illustrated here on two main cases: evaporation and transport limited growth. Importantly, we also quantify how colloidal stability may hinder the growth and show that care must be taken as to the composition of the initial dispersion, especially regarding traces of ionic species that can destabilize the suspension upon concentration. We define a stability chart, which, when fulfilled, permits us to grow and shape up solids, including superlattices and extended and thick arrays of nanoparticles made of unary and binary dispersions, composites, and heterojunctions between distinct types of nanoparticles. In all cases, the geometry of the final solid is imparted by that of the microfluidic device.
author_names: Julie Angly

Antonio Iazzolino

Jean-Baptiste Salmon

Jacques Leng

Sivasankaran Prathap Chandran

Virginie Ponsinet

Anthony Desert

Aurelie Le Beulze

Stephane Mornet

Mona Treguer-Delapierre

Miguel A Correa-Duarte
title: Microfluidic induced growth and shape up of three dimensional extended arrays of densely packed nanoparticles.
venue: ACS nano
year: 2013

abstract: Controlling the selectivity in electrochemical CO2 reduction is an unsolved challenge. While tin (Sn) has emerged as a promising non precious catalyst for CO2 electroreduction, most Sn based catalysts produce formate as the major product, which is less desirable than CO in terms of separation and further use. Tin monoxide (SnO) nanoparticles supported on carbon black were synthesized and assembled and their application in CO2 reduction was studied. Remarkably high selectivity and partial current densities for CO formation were obtained using these SnO nanoparticles compared to other Sn catalysts. The high activity is attributed to the ultra small size of the nanoparticles (2.6 nm) while the high selectivity is attributed to a local pH effect arising from the dense packing of nanoparticles in the conductive carbon black matrix.
author_names: J J Gu

Florent Heroguel

Jeremy S Luterbacher

Xile Hu
title: Densely Packed, Ultra Small SnO Nanoparticles for Enhanced Activity and Selectivity in Electrochemical CO2 Reduction.
venue: Angewandte Chemie
year: 2018

abstract: We report detailed characterization of surface plasmon polariton guiding along 1 1.5 and 2 mm wide channels in high density ~75 mm 2) random arrays of gold 70 nm high and 50 nm wide nanoparticles fabricated on a 70 nm thin gold film supported by a 170 mm thick silica substrate. The mode propagation losses, effective index dispersion, and scattering parameters are characterized using leakage radiation microscopy, in direct and Fourier planes, in the wavelength range of 740 840 nm. It is found that the mode supported by 2 mm wide channels propagates over 10 mm in straight waveguides, with the corresponding S bends and Y splitters functioning reasonably well. The results show that the SPP waves can efficiently be guided by narrow scattering free channels cut through randomly corrugated surface regions. The potential of this waveguiding mechanism is yet to be fully explored by tuning the scattering mean free path and localization length via the density and size of random nanoparticles. Nevertheless, the results obtained are encouraging and promising diverse applications of these waveguide components in plasmonic circuitry.
author_names: Eduardo Pisano

Victor Coello

Cesar E Garcia-Ortiz

Yiting Chen

Jonas Beermann

Sergey I Bozhevolnyi
title: Plasmonic channel waveguides in random arrays of metallic nanoparticles.
venue: Optics express
year: 2016

abstract: Two dimensional arrays of nanoparticles (NPs) have widespread applications in optical coatings, plasmonic sensors, and nanocomposites. Current bottom up approaches that use homogeneous NP templates, such as silane self assembled monolayers or homopolymers, are typically plagued by NP aggregation, whereas patterned block copolymer (BCP) films require specific compositions for specific NP distributions. Here, we show, using polystyrene b poly(4 vinylpyridine) (PS b P4VP) and gold NPs (AuNPs) of various sizes, that a nanothin PS b P4VP brushlike coating (comprised of a P4VP wetting layer and a PS overlayer) which is adsorbed onto flat substrates during their immersion in very dilute PS b P4VP tetrahydrofuran solutions, provides an excellent template for obtaining dense and well dispersed AuNPs with little aggregation. These non close packed arrays have similar characteristics regardless of immersion time in solution (about 10 120 s studied) solution concentration below a critical value (0.1 and 0.05 mg/mL studied) and AuNP diameter (10 90 nm studied) Very dilute BCP solutions are necessary to avoid deposition, during substrate withdrawal, of additional material onto the adsorbed BCP layer, which typically leads to patterned surfaces. The PS brush coverage depends on immersion time (adsorption kinetics) but full coverage does not inhibit AuNP adsorption, which is attributed to PS molecular rearrangement during exposure to the aqueous AuNP colloidal solution. The simplicity, versatility and robustness of the method will enable applications in materials science requiring dense, unaggregated NP arrays.
author_names: Hu Zhu

Jean-Francois Masson

C Geraldine Bazuin
title: Monolayer Arrays of Nanoparticles on Block Copolymer Brush Films.
venue: Langmuir the ACS journal of surfaces and colloids
year: 2019