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Radio-frequency capacitance spectroscopy of metallic nanoparticles.

ABSTRACT: Recent years have seen great progress in our understanding of the electronic properties of nanomaterials in which at least one dimension measures less than 100?nm. However, contacting true nanometer scale materials such as individual molecules or nanoparticles remains a challenge as even state-of-the-art nanofabrication techniques such as electron-beam lithography have a resolution of a few nm at best. Here we present a fabrication and measurement technique that allows high sensitivity and high bandwidth readout of discrete quantum states of metallic nanoparticles which does not require nm resolution or precision. This is achieved by coupling the nanoparticles to resonant electrical circuits and measurement of the phase of a reflected radio-frequency signal. This requires only a single tunnel contact to the nanoparticles thus simplifying device fabrication and improving yield and reliability. The technique is demonstrated by measurements on 2.7?nm thiol coated gold nanoparticles which are shown to be in excellent quantitative agreement with theory.

SUBMITTER: Frake JC

PROVIDER: S-EPMC4650672 | biostudies-literature | 2015

REPOSITORIES: biostudies-literature

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Radio-frequency capacitance spectroscopy of metallic nanoparticles.

Frake James C JC Kano Shinya S Ciccarelli Chiara C Griffiths Jonathan J Sakamoto Masanori M Teranishi Toshiharu T Majima Yutaka Y Smith Charles G CG Buitelaar Mark R MR

Scientific reports 20150604

Recent years have seen great progress in our understanding of the electronic properties of nanomaterials in which at least one dimension measures less than 100 nm. However, contacting true nanometer scale materials such as individual molecules or nanoparticles remains a challenge as even state-of-the-art nanofabrication techniques such as electron-beam lithography have a resolution of a few nm at best. Here we present a fabrication and measurement technique that allows high sensitivity and high ...[more]

PMID: 26042729

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Project description:ObjectiveCardiovascular interventional devices typically have long metallic braids or backbones to aid in steerability and pushability. However, electromagnetic coupling of metallic-based cardiovascular interventional devices with the radiofrequency (RF) fields present during Magnetic Resonance Imaging (MRI) can make a device unsafe for use in an MRI scanner. We aimed to develop MRI conditional actively-tracked cardiovascular interventional devices by sufficiently attenuating induced currents on the metallic braid/tube and internal-cabling using miniaturized resonant floating RF traps (MBaluns).MethodMBaluns were designed for placement at multiple locations along a conducting cardiovascular device to prevent the establishment of standing waves and to dissipate RF-induced energy. The MBaluns were constructed with loosely-wound solenoids to be sensitive to transverse magnetic fields created by both surface currents on the device's metallic backbone and common-mode currents on internal cables. Electromagnetic simulations were used to optimize MBalun parameters. Following optimization, two different MBalun designs were applied to MR-actively-tracked metallic guidewires and metallic-braided electrophysiology ablation catheters. Control-devices were constructed without MBaluns. MBalun performance was validated using network-analyzer quantification of current attenuation, electromagnetic Specific-Absorption-Rate (SAR) analysis, thermal tests during high SAR pulse sequences, and MRI-guided cardiovascular navigation in swine.ResultsElectromagnetic SAR simulations resulted in ≈20 dB attenuation at the tip of the wire using six successive MBaluns. Network-analyzer tests confirmed ∼17 dB/MBalun surface-current attenuation. Thermal tests indicated temperature decreases of 5.9 °C in the MBalun-equipped guidewire tip. Both devices allowed rapid vascular navigation resulting from good torquability and MR-Tracking visibility.ConclusionMBaluns increased device diameter by 20%, relative to conventional devices, providing a spatially-efficient means to prevent heating during MRI.SignificanceMBaluns allow use of long metallic components, which improves mechanical performance in active MR-guided interventional devices.

Dataset Information

Radio-frequency capacitance spectroscopy of metallic nanoparticles.

Publications

Radio-frequency capacitance spectroscopy of metallic nanoparticles.

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