Visible radiation at resonant frequencies is transduced to thermal energy by surface plasmons on gold nanoparticles. Temperature in ≤10-microliter aqueous suspensions of 20-nanometer gold particles irradiated by a continuous wave Ar+ ion laser at 514 nm increased to a maximum equilibrium value. This value increased in proportion to incident laser power and in proportion to nanoparticle content at low concentration. Heat input to the system by nanoparticle transduction of resonant irradiation equaled heat flux outward by conduction and radiation at thermal equilibrium. The efficiency of transducing incident resonant light to heat by microvolume suspensions of gold nanoparticles was determined by applying an energy balance to obtain a microscale heat-transfer time constant from the transient temperature profile. Measured values of transduction efficiency were increased from 3.4% to 9.9% by modulating the incident continuous wave irradiation.
The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which causes the coronavirus disease (COVID-19), is shed in feces and the viral ribonucleic acid (RNA) is detectable in wastewater. A nine-week wastewater epidemiology study of ten wastewater facilities, serving 39% of the state of Utah or 1.26 M individuals was conducted in April and May of 2020. COVID-19 cases were tabulated from within each sewershed boundary. RNA from SARS-CoV-2 was detectable in 61% of 126 wastewater samples. Urban sewersheds serving >100,000 individuals and tourist communities had higher detection frequencies. An outbreak of COVID-19 across two communities positively correlated with an increase in wastewater SARS-CoV-2 RNA, while a decline in COVID-19 cases preceded a decline in RNA. SARS-CoV-2 RNA followed a first order decay rate in wastewater, while 90% of the RNA was present in the liquid phase of the influent. Infiltration and inflow, virus decay and sewershed characteristics should be considered during correlation analysis of SAR-CoV-2 with COVID-19 cases. These results provide evidence of the utility of wastewater epidemiology to assist in public health responses to COVID-19.
The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which causes the coronavirus disease (COVID-19), is shed in feces and the virus RNA is detectable in wastewater. A nine-week wastewater epidemiology study of ten wastewater facilities, serving 39% of the state of Utah or 1.26M individuals was conducted in April and May of 2020. COVID-19 cases were tabulated from within each sewershed boundary by public health partners. The virus was detectable in 61% of 126 unique wastewater samples. Urban sewersheds serving >100,000 individuals and tourist communities had higher detection frequencies of the virus RNA. An outbreak of COVID-19 across two communities correlated with an increase in SARS-CoV-2 RNA in wastewater, while a decline in COVID-19 case counts preceded a decline in SARS-CoV-2 RNA. These results demonstrate the utility of wastewater epidemiology to assist in public health responses to COVID-19.
Electroless gold island thin films are formed by galvanic replacement of silver reduced onto a tin-sensitized silica surface. A novel approach to create nanoparticle ensembles with tunable particle dimensions, densities, and distributions by thermal transformation of these electroless gold island thin films is presented. Deposition time is adjusted to produce monomodal ensembles of nanoparticles from 9.5 +/- 4.0 to 266 +/- 22 nm at densities from 2.6 x 1011 to 4.3 x 108 particles cm-2. Scanning electron microscopy and atomic force microscopy reveal electroless gold island film structures as well as nanoparticle dimensions, densities, and distributions obtained by watershed analysis. Transmission UV-vis spectroscopy reveals photoluminescent features that suggest ultrathin EL films may be smoother than sputtered Au films. X-ray diffraction shows Au films have predominantly (111) orientation.
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