Nanoparticle-Enhanced Plasma Discharge Using Nanosecond High-Voltage Pulses

Abstract

By discharging nanosecond high-voltage (5 kV) pulses across an insulating substrate containing Au, Pt, or Cu nanoparticles, a 3 order of magnitude (1000×) enhancement in the generation of plasma can be achieved through local field enhancement on the surface of the nanoparticles. The lowtemperature nature of this transient plasma is crucial to maintaining the structural integrity of these delicate nanoparticles. These nanoparticles provide up to a 1000-fold enhancement in the generation of the plasma, which is localized to the surface of the nanoparticles where it is potentially useful (e.g., for catalysis). We performed both time-domain and frequency-domain calculations of the electromagnetic response of the nanoparticles based on high-resolution transmission electron microscope (HRTEM) images, which show local field enhancement of the nanosecond high-voltage pulse on the order of 3×. Since the plasma initiation depends exponentially on the peak electric field strength, this 3-fold increase in the local electric field can result in a several orders of magnitude increases in the generation of plasma at a given applied external field strength. In order to rule out plasmon-resonance enhancement, which is often associated with small metal nanoparticles, we performed finite difference time domain (FDTD) simulations in the optical frequency domain, which show that the effect of plasmon resonance is negligible for Pt nanoparticles. We therefore attribute the nanoparticle-based enhancement to the generation of plasma (an electrostatic effect) rather than enhanced coupling of light from the near field to the far field via the plasmon resonance phenomenon (an optical effect).

Au Nanoparticle Enhancement of Plasma-Driven Methane Conversion into Higher Order Hydrocarbons via Hot Electrons

“…Below 9 kV, we only observe plasma emission with Au nanoparticles, indicating that enhancement factors much higher than this are created by the local field enhancement of the nanoparticles. In a previous study carried out in argon, enhancement factors of more than 1000-fold were observed with the presence of the nanoparticles . Above 9 kV, the plasma emission is larger for the electrodes without nanoparticles, where the applied field is strong enough to initiate a plasma from the bulk electrodes.…”

“…In a previous study carried out in argon, enhancement factors of more than 1000-fold were observed with the presence of the nanoparticles. 35 Above 9 kV, the plasma emission is larger for the electrodes without nanoparticles, where the applied field is strong enough to initiate a plasma from the bulk electrodes. Here, the Au nanoparticle film creates a shunt of the externally applied field applied between the copper electrodes.…”

“…The mechanism of electron emission from thin metal films was attributed to electric field emission at first . However, later works on these discontinuous ultrathin metal films revealed the importance of the contribution of long-lifetime hot electrons, which have a relatively high probability to reach the nanoparticle surfaces in this process. − In addition, nanoscale sharp features, such as carbon nanotubes and semiconductor nanowires, have been known for their capability to enhance local electrostatic fields and, hence, field-emission of electrons. − Our group reported enhanced plasma emission spectra in Ar on metal nanoparticles due to this local field enhancement, and we have ruled out the possibility that such an enhancement originates from plasmon-resonant (i.e., optical) effects …”

“…29−34 Our group reported enhanced plasma emission spectra in Ar on metal nanoparticles due to this local field enhancement, and we have ruled out the possibility that such an enhancement originates from plasmon-resonant (i.e., optical) effects. 35 In the work presented here, we explore the upconversion of methane to higher order hydrocarbons by discharging a nanosecond pulsed plasma across Au nanoparticles. This upconversion process is monitored using mass spectrometry and plasma emission spectroscopy.…”

Monitoring Reaction Intermediates in Plasma-Driven SO2, NO, and NO2 Remediation Chemistry Using In Situ SERS Spectroscopy

“…Here, we utilize a transient pulsed plasma discharge in a glass-slide plasma-based reactor, which consists of two parallel copper electrodes separated by an approximately 5 mm gap (see Figure ). − Further details are given in the Supporting Information.…”