The use of silver nanoparticles (AgNPs) in antimicrobial applications, including a wide range of consumer goods and apparel, has attracted attention because of the unknown health and environmental risks associated with these emerging materials. Of particular concern is whether there are new risks that are a direct consequence of their nanoscale size. Identifying those risks associated with nanoscale structure has been difficult due to the fundamental challenge of detecting and monitoring nanoparticles in products or the environment. Here, we introduce a new strategy to directly monitor nanoparticles and their transformations under a variety of environmental conditions. These studies reveal unprecedented dynamic behavior of AgNPs on surfaces. Most notably, under ambient conditions at relative humidities greater than 50%, new silver nanoparticles form in the vicinity of the parent particles. This humidity-dependent formation of new particles was broadly observed for a variety of AgNPs and substrate surface coatings. We hypothesize that nanoparticle production occurs through a process involving three stages: (i) oxidation and dissolution of silver from the surface of the particle, (ii) diffusion of silver ion across the surface in an adsorbed water layer, and (iii) formation of new, smaller particles by chemical and/or photoreduction. Guided by these findings, we investigated non-nanoscale sources of silver such as wire, jewelry, and eating utensils that are placed in contact with surfaces and found that they also formed new nanoparticles. Copper objects display similar reactivity, suggesting that this phenomenon may be more general. These findings challenge conventional thinking about nanoparticle reactivity and imply that the production of new nanoparticles is an intrinsic property of the material that is not strongly size dependent. The discovery that AgNPs and CuNPs are generated spontaneously from manmade objects implies that humans have long been in direct contact with these nanomaterials and that macroscale objects represent a potential source of incidental nanoparticles in the environment.
Size-dependent properties of surface-confined inorganic nanostructures are of interest for applications ranging from sensing to catalysis and energy production. Ligand-stabilized nanoparticles are attractive precursors for producing such nanostructures because the stabilizing ligands may be used to direct assembly of thoroughly characterized nanoparticles on the surface. Upon assembly; however, the ligands block the active surface of the nanoparticle. Methods used to remove these ligands typically result in release of nanoparticles from the surface or cause undesired growth of the nanoparticle core. Here, we demonstrate that mild chemical oxidation (50 ppm of ozone in nitrogen) oxidizes the thiolate headgroups, lowering the ligand's affinity for the gold nanoparticle surface and permitting the removal of the ligands at room temperature by rinsing with water. XPS and TEM measurements, performed using a custom planar analysis platform that permits detailed imaging and chemical analysis, provide insight into the mechanism of ligand removal and show that the particles retain their core size and remain tethered on the surface core during treatment. By varying the ozone exposure time, it is possible to control the amount of ligand removed. Catalytic carbon monoxide oxidation was used as a functional assay to demonstrate ligand removal from the gold surface for nanoparticles assembled on a high surface area support (fumed silica).
We report viscosities of liquid hexadecane measured at temperatures between (323 and 673) K and at pressures up to 4.0 MPa. This study significantly extends the temperature range over which viscosity data for hexadecane are available. The experiments were carried out using a dual-capillary viscometer that measures the ratio of the viscosity at the temperature in question to that at a reference temperature, 298.15 K in this work, at which the viscosity is well known. Absolute viscosities were then obtained with an estimated expanded relative uncertainty of about 3 % at 95 % confidence. An empirical function was developed to correlate the viscosity ratio with the density ratio and this fitted the experimental data within about 1 %. The results were found to agree well with the existing literature data.
In spite of the many potential benefits and applications of nanoparticles, concerns have been raised regarding their production, use, and ultimate fate due to poor process yields and uncertain health and environmental impacts. Production of commercial nanoparticles is growing as they find increasing use in industrial and consumer products. Nickel nanoparticles (NiNPs) have shown promise as a single element braze material, but the energy and material efficiencies of NiNP production remain uncertain. In this study, life cycle assessment (LCA) is employed to compare three different NiNP synthesis methods in terms of environmental impact. The study reveals challenges in using LCA to assess nanomanufacturing processes. Sensitivity analysis is performed across several process parameters to demonstrate an approach for addressing data uncertainties. The relative performance of the NiNP synthesis processes are discussed, and potential environmental implications for other NiNP synthesis processes are introduced. Policy change may be necessary to provide adequate transparency in assessing nanotechnologies for engineering applications.
Advances in IC process technology have enabled the design of complex systems on a single chip. System-on-chip developers need to be able to mix and match pre-designed, best-in-class functional blocks from many providers if they are to meet design deadlines with limited design engineering resources. Consequently, there is a rising interest in the creation, distribution, and design application of reusable, interoperable blocks of intellectual property, referred to as "IP" or "virtual components." This panel will explore the opportunities and challenges for design innovation offered by a worldwide, open reuse mechanism for virtual components.The session will begin with an embedded tutorial case study on the VSIA (Virtual Socket Interface Alliance) approach to design reuse. Then IP providers and users will discuss the technical and business challenges in establishing a mechanism for reuse of virtual components. The panelists will also discuss the issues in integrating virtual components from multiple providers into system-onchip designs. Doug Fairbairn, Cadence Design Systems Larry Cooke, Toshiba America Electronic ComponentsThe VSI Alliance was formed to help drive a common vision for the use of complex cores in the electronics industry and break down the technical barriers to the mix and match of 1P in system-on-chip design, including new concepts such as "virtual components" and the "virtual socket interface." This tutorial will describe the background of the VSI Alliance, including the industry forces which brought it into existence. We will present the first results of the Alliance, including the VSI Architectural Document and Roadmap and how these can be applied to system-on-chip design. We will also provide a brief review and description of potential impact of the Alliance's work in progress in areas such as IP protection, mixed-signal design, manufacturing test, system-level design, implementationlverification, and on-chip bus standards. Steve Schulz, Texas InstrumentsAfter evaluation, virtual components will be designed into the system-chips of the future using new methodologies. This presentation will cover how virtual components are captured, starting from an English requirements definition through the conversion to netlists, including hardwarelsoftware, board, ASIC, and FPGA technologies. It will also describe how virtual components are captured when netlists are converted to real physical instantiations. There will be descriptions of the documentation, formats, and design interfaces required to facilitate "plug-and-play" productivity gains, as well as realistic views of required application support for various types of virtual components, Takahide Inoue, SonyProbably the most profitable and often-used virtual components in system houses are standard formats such as NTSC, Ethernet, and PCI bus. The emerging System-on-Chip (SoC) integration capabilities require system industries and semiconductor manufacturers to develop strong technical and business collaborations, since now more than ever, SoCs must be d...
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.