It is now recognized that nanoscale particulate matter(PM)represents a substantial health hazard for our society,including PM from restaurant smoke.In this study,we explored the use of a transient pulsed plasma in con...It is now recognized that nanoscale particulate matter(PM)represents a substantial health hazard for our society,including PM from restaurant smoke.In this study,we explored the use of a transient pulsed plasma in conjunction with an applied DC bias to treat oil aerosols that closely resemble restaurant(i.e.,charbroiler)smoke emissions.For polyaromatic olefin PAO-4 and soybean oil,we found that a three-order-of-magnitude reduction in particulates(i.e.,99.9%remediation)could be achieved with this system.Here,the plasma discharge was produced in a 4-in.-diameter cylindrical reactor with a 5-10 ns high voltage(30 kV)pulse generator together with applied DC bias voltages up to 10 kV.The distribution of nanoparticle sizes was measured using a scanning mobility particle sizer(SMPS)with diameter centered around 225 nm.Here,the main mechanism of remediation occurs in a two-step process in which the oil nanoparticles are first ionized by the free electrons and free radicals in the plasma and then the charged particles are swept out to the sidewalls of the reactor by the applied DC potential.We believe this general approach opens up new degrees of freedom in the design of electrostatic oil aerosol pollution control devices.展开更多
There are various mechanisms of light emission in carbon nanotubes (CNTs), which give rise to a wide range of spectral emission characteristics that provide important information regarding the underlying physical proc...There are various mechanisms of light emission in carbon nanotubes (CNTs), which give rise to a wide range of spectral emission characteristics that provide important information regarding the underlying physical processes that lead to photon emission. Here, we report spectra obtained from individual suspended CNT dual-gate field effect transistor (FET) devices under different gate and bias conditions. By applying opposite voltages to the gate electrodes (i.e., Vg1 = –Vg2), we are able to create a pn-junction within the suspended region of the CNT. Under forward bias conditions, the spectra exhibit a peak corresponding to E11 exciton emission via thermal (i.e., blackbody) emission occurring at electrical powers around 8 μW, which corresponds to a power density of approximately 0.5 MW/cm2. On the other hand, the spectra observed under reverse bias correspond to impact ionization and avalanche emission, which occurs at electrical powers of ~ 10 nW and exhibits a featureless flat spectrum extending from 1,600 nm to shorter wavelengths up to 600 nm. Here, the hot electrons generated by the high electric fields (~ 0.5 MV/cm) are able to produce high energy photons far above the E11 (ground state) energy. It is somewhat surprising that these devices do not exhibit light emission by the annihilation of electrons and holes under forward bias, as in a light emitting diode (LED). Possible reasons for this are discussed, including Auger recombination.展开更多
文摘It is now recognized that nanoscale particulate matter(PM)represents a substantial health hazard for our society,including PM from restaurant smoke.In this study,we explored the use of a transient pulsed plasma in conjunction with an applied DC bias to treat oil aerosols that closely resemble restaurant(i.e.,charbroiler)smoke emissions.For polyaromatic olefin PAO-4 and soybean oil,we found that a three-order-of-magnitude reduction in particulates(i.e.,99.9%remediation)could be achieved with this system.Here,the plasma discharge was produced in a 4-in.-diameter cylindrical reactor with a 5-10 ns high voltage(30 kV)pulse generator together with applied DC bias voltages up to 10 kV.The distribution of nanoparticle sizes was measured using a scanning mobility particle sizer(SMPS)with diameter centered around 225 nm.Here,the main mechanism of remediation occurs in a two-step process in which the oil nanoparticles are first ionized by the free electrons and free radicals in the plasma and then the charged particles are swept out to the sidewalls of the reactor by the applied DC potential.We believe this general approach opens up new degrees of freedom in the design of electrostatic oil aerosol pollution control devices.
基金The authors would like to acknowledge support from the Northrop Grumman-Institute of Optical Nanomaterials and Nanophotonics(NG-ION2)(B.W.).This research was supported by the NSF Award No.CBET-1905357(S.Y.)and Department of Energy DOE Award No.DE-FG02-07ER46376(Y.W.).R.K.acknowledges funding from AFOSR Grant No.FA9550-16-1-0306 and National Science Foundation Award No.1610604.R.A.acknowledges a USC Provost Graduate Fellowship.A portion of this work was carried out in the University of California Santa Barbara(UCSB)nanofabrication facility:This work was also carried out in part at the Center for Integrated Nanotechnologies,a U.S.Department of Energy,Office of Science user facility.Y.L.,S.K.D,and H.H.acknowledge partial support of the LANL LDRD program and Y.L.and H..H.acknowledge support from DOE BES FWP#LANLBES22.
文摘There are various mechanisms of light emission in carbon nanotubes (CNTs), which give rise to a wide range of spectral emission characteristics that provide important information regarding the underlying physical processes that lead to photon emission. Here, we report spectra obtained from individual suspended CNT dual-gate field effect transistor (FET) devices under different gate and bias conditions. By applying opposite voltages to the gate electrodes (i.e., Vg1 = –Vg2), we are able to create a pn-junction within the suspended region of the CNT. Under forward bias conditions, the spectra exhibit a peak corresponding to E11 exciton emission via thermal (i.e., blackbody) emission occurring at electrical powers around 8 μW, which corresponds to a power density of approximately 0.5 MW/cm2. On the other hand, the spectra observed under reverse bias correspond to impact ionization and avalanche emission, which occurs at electrical powers of ~ 10 nW and exhibits a featureless flat spectrum extending from 1,600 nm to shorter wavelengths up to 600 nm. Here, the hot electrons generated by the high electric fields (~ 0.5 MV/cm) are able to produce high energy photons far above the E11 (ground state) energy. It is somewhat surprising that these devices do not exhibit light emission by the annihilation of electrons and holes under forward bias, as in a light emitting diode (LED). Possible reasons for this are discussed, including Auger recombination.
