scholarly journals A Cavity-Enhanced UV Absorption Instrument for High Precision, Fast Time Response Ozone Measurements

2020 ◽  
Author(s):  
Reem A. Hannun ◽  
Andrew K. Swanson ◽  
Steven A. Bailey ◽  
Thomas F. Hanisco ◽  
T. Paul Bui ◽  
...  
Keyword(s):  
Marine Boundary Layer ◽  
Optical Cavity ◽  
Deposition Velocity ◽  
Flux Measurement ◽  
High Sensitivity ◽  
Field Measurements ◽  
Uv Absorption ◽  
Fast Time ◽  
Optical Cell ◽  
Research Aircraft

Abstract. The NASA Rapid Ozone Experiment (ROZE) is a broadband cavity-enhanced UV absorption instrument for the detection of in situ ozone (O3). ROZE uses an incoherent LED light source coupled to a high-finesse optical cavity to achieve an effective pathlength of ~ 104 m. Due to its high-sensitivity and small optical cell volume, ROZE demonstrates a 1σ precision of 80 pptv (0.1 s) and 31 pptv (1 s), as well as a 1/e response time of 50 ms. ROZE can be operated in a range of field environments, including low- and high-altitude research aircraft, and is particularly suited to O3 vertical flux measurements using the eddy covariance technique. ROZE was successfully integrated aboard the NASA DC-8 aircraft during July–September 2019 and validated against a well-established chemiluminescence measurement of O3. A flight within the marine boundary layer also demonstrated flux measurement capabilities, and we observed a mean O3 deposition velocity of 0.029 ± 0.005 cm s–1 to the ocean surface. The performance characteristics detailed below make ROZE a robust, versatile instrument for field measurements of O3.

scholarly journals A cavity-enhanced ultraviolet absorption instrument for high-precision, fast-time-response ozone measurements

2020 ◽  
Vol 13 (12) ◽  
pp. 6877-6887
Author(s):  
Reem A. Hannun ◽  
Andrew K. Swanson ◽  
Steven A. Bailey ◽  
Thomas F. Hanisco ◽  
T. Paul Bui ◽  
...  
Keyword(s):  
Marine Boundary Layer ◽  
Light Emitting Diode ◽  
Optical Cavity ◽  
Deposition Velocity ◽  
Flux Measurement ◽  
Ultraviolet Absorption ◽  
Time Response ◽  
Integration Time ◽  
Fast Time ◽  
Optical Cell

Abstract. The NASA Rapid Ozone Experiment (ROZE) is a broadband cavity-enhanced UV (ultraviolet) absorption instrument for the detection of in situ ozone (O3). ROZE uses an incoherent LED (light-emitting diode) light source coupled to a high-finesse optical cavity to achieve an effective pathlength of ∼ 104 m. Due to its high sensitivity and small optical cell volume, ROZE demonstrates a 1σ precision of 80 pptv (parts per trillion by volume) in 0.1 s and 31 pptv in a 1 s integration time, as well as an e-fold time response of 50 ms. ROZE can be operated in a range of field environments, including low- and high-altitude research aircraft, and is particularly suited to O3 vertical-flux measurements using the eddy covariance technique. ROZE was successfully integrated aboard the NASA DC-8 aircraft during July–September 2019 and validated against a well-established chemiluminescence measurement of O3. A flight within the marine boundary layer also demonstrated flux measurement capabilities, and we observed a mean O3 deposition velocity of 0.029 ± 0.005 cm s−1 to the ocean surface. The performance characteristics detailed below make ROZE a robust, versatile instrument for field measurements of O3.

scholarly journals A novel instrument for measurements of BrO with LED based Cavity-Enhanced Differential Optical Absorption Spectoscopy

2013 ◽  
Vol 6 (4) ◽  
pp. 6047-6096
Author(s):  
D. J. Hoch ◽  
J. Buxmann ◽  
H. Sihler ◽  
D. Pöhler ◽  
C. Zetzsch ◽  
...  
Keyword(s):  
Optical Absorption ◽  
Marine Boundary Layer ◽  
Detection Limits ◽  
High Sensitivity ◽  
Field Measurements ◽  
Reaction Chamber ◽  
Optical Absorption Spectroscopy ◽  
Integration Time ◽  
Polar Regions ◽  
Chamber Studies

Abstract. The chemistry of the troposphere and specifically the global tropospheric ozone budget is affected by reactive halogen species like Bromine monoxide (BrO) or Chlorine monoxide (ClO). Especially BrO plays an important role in the processes of ozone destruction, disturbance of NOx and HOx chemistry, oxidation of DMS, and the deposition of elementary mercury. In the troposphere BrO has been detected in polar regions, at salt lakes, in volcanic plumes, and in the marine boundary layer. For a better understanding of these processes field measurements as well as reaction-chamber studies are performed. In both cases instruments with high spatial resolution and high sensitivity are necessary. A Cavity Enhanced Differential Optical Absorption Spectroscopy (CE-DOAS) instrument with an open path measurement cell was designed and applied. For the first time, a CE-DOAS instrument is presented using an UV-LED in the 325–365 nm wavelength range. In laboratory studies, BrO as well as HONO, HCHO, O3, and O4, could be reliable determined at detection limits of 20 ppt for BrO, 9.1 ppb for HCHO, 970 ppt for HONO, and 91 ppb for O3, for five minutes integration time, respectively. The best detection limits were achieved for BrO (11 ppt), HCHO (5.1 ppb), HONO (490 ppt), and O3 (59 ppb) for integration times of 81 min or less. Comparison with established White-System DOAS and O3 monitor demonstrate the reliability of the instrument.

scholarly journals Undersizing of aged African biomass burning aerosol by an ultra-high-sensitivity aerosol spectrometer

2021 ◽  
Vol 14 (11) ◽  
pp. 7381-7404
Author(s):  
Steven G. Howell ◽  
Steffen Freitag ◽  
Amie Dobracki ◽  
Nikolai Smirnow ◽  
Arthur J. Sedlacek III
Keyword(s):  
Black Carbon ◽  
Biomass Burning ◽  
Marine Boundary Layer ◽  
Particle Diameter ◽  
High Sensitivity ◽  
Mie Scattering ◽  
Infrared Light ◽  
Brown Carbon ◽  
Research Aircraft ◽  
Particle Sizer

Abstract. The ultra-high-sensitivity aerosol spectrometer (UHSAS) differs from most other optical particle spectrometers by using a high-power infrared (IR) laser to detect small particles and reduce the sizing ambiguity due to the non-monotonicity of scattering with particle size. During the NASA ORACLES project (ObseRvations of Aerosols above CLouds and their intEractionS) over the southeast Atlantic Ocean, the UHSAS clearly undersized particles in the biomass burning plume extending from southern Africa. Since the horizontal and vertical extent of the plume was vast, the NASA P-3B research aircraft often flew through a fairly uniform biomass burning plume for periods exceeding 30 min, sufficient time to explore the details of the UHSAS response by selecting single particle sizes with a differential mobility analyzer (DMA) and passing them to the UHSAS. This was essentially an in-flight calibration of the UHSAS using the particles of interest. Two modes of responses appeared. Most particles were undersized by moderate amounts, ranging from not at all for 70 nm aerosols to 15 % for 280 nm particles. Mie scattering calculations show that composition-dependent refractive index of the particles cannot explain the pattern. Heating of brown carbon or tarballs in the beam causing evaporation and shrinking of the particles is the most plausible explanation, though mis-sizing due to non-sphericity cannot be ruled out. A small fraction (10 %–30 %) of the particles were undersized by 25 % to 35 %. Those were apparently the particles containing refractory black carbon. Laboratory calibrations confirm that black carbon is drastically undersized by the UHSAS, because particles heat to their vaporization point and shrink. A simple empirical correction equation was implemented that dramatically improves agreement with DMA distributions between 100 and 500 nm. It raised the median particle diameter by 18 nm, from 163 to 181 nm, during the August 2017 deployment and by smaller amounts during deployments with less intense pollution. Calculated scattering from UHSAS size distributions increased by about 130 %, dramatically improving agreement with scattering measured by nephelometers. The correction is only valid in polluted instances; clean marine boundary layer and free troposphere aerosols behaved more like the calibration spheres. We were unable to directly test the correction between 500 and 1000 nm, though aerodynamic particle sizer (APS) data appear to show that the correction is poor at the largest diameters, which is no surprise as the composition of those particles is likely to be quite different than that of the accumulation mode. This adds to the evidence that UHSAS data must be treated cautiously whenever the aerosol may absorb infrared light. Similar corrections may be required whenever brown carbon aerosol is present.

scholarly journals Undersizing of Aged African Biomass Burning Aerosol by an Ultra High Sensitivity Aerosol Spectrometer

2020 ◽  
Author(s):  
Steven G. Howell ◽  
Steffen Freitag ◽  
Amie Dobracki ◽  
Nikolai Smirnow ◽  
Arthur J. Sedlacek III
Keyword(s):  
Black Carbon ◽  
Biomass Burning ◽  
Marine Boundary Layer ◽  
Particle Diameter ◽  
High Sensitivity ◽  
Mie Scattering ◽  
Infrared Light ◽  
Ir Absorption ◽  
Brown Carbon ◽  
Research Aircraft

Abstract. The Ultra-High Sensitivity Aerosol Spectrometer (UHSAS) differs from most other optical particle spectrometers by using a high-power infrared (IR) laser to detect small particles and reduce the sizing ambiguity due to the non-monotonicity of scattering with particle size. During the NASA ORACLES project (ObseRvations of Aerosols above CLouds and their intEractionS) over the southeast Atlantic Ocean, the UHSAS clearly undersized particles in the biomass burning plume extending from Southern Africa. Since the horizontal and vertical extent of the plume was vast, the NASA P-3B research aircraft often flew through a fairly uniform biomass burning plume for periods exceeding 30 minutes, sufficient time to explore the details of the UHSAS response by selecting single particle sizes with a Differential Mobility Analyzer (DMA) and passing them to the UHSAS. This was essentially an in-flight calibration of the UHSAS using the particles of interest. Two modes of responses appeared. Most particles were undersized by moderate amounts, ranging from not at all for 70 nm aerosols to 15 % for 280 nm particles. Mie scattering calculations show that composition-dependent refractive index of the particles is unlikely to explain the pattern. Heating of brown carbon or tarballs in the beam causing evaporation and shrinking of the particles is the most plausible explanation, though that requires greater IR absorption than is usually attributed to brown carbon. 10–30 % of the particles were undersized by 25 to 35 %. Those were apparently the particles containing refractory black carbon. Laboratory calibrations confirm that black carbon is drastically undersized by the UHSAS, though the mechanism is not entirely clear. A simple empirical correction equation was implemented that dramatically improves agreement with DMA distributions between 100 and 500 nm. It raised median particle diameter 18 nm, from 163 to 181 nm during the August 2017 deployment and by smaller amounts during deployments with less intense pollution. Calculated scattering from UHSAS size distributions increased by about 130 %, dramatically improving agreement with scattering measured by nephelometers. The correction is only valid in polluted instances; clean marine boundary layer and free troposphere aerosols behaved more like the calibration spheres. We were unable to directly test the correction between 500 and 1000 nm, though APS data appear to show that the correction is poor at the largest diameters, which is no surprise as the composition of those particles is likely to be quite different than that of the accumulation mode. This adds to the evidence that UHSAS data must be treated cautiously whenever the aerosol may absorb infrared light. Similar corrections may be required whenever brown carbon aerosol is present.

scholarly journals Differentiating and quantifying exosome secretion from a single cell using quasi-bound states in the continuum

Nanophotonics ◽  
2020 ◽  
Vol 9 (5) ◽  
pp. 1081-1086 ◽  
Author(s):  
Abdoulaye Ndao ◽  
Liyi Hsu ◽  
Wei Cai ◽  
Jeongho Ha ◽  
Junhee Park ◽  
...  
Keyword(s):  
Single Cell ◽  
Optical Sensors ◽  
Figure Of Merit ◽  
Bound States ◽  
Single Cell Analysis ◽  
Optical Cavity ◽  
High Sensitivity ◽  
Cell Secretion ◽  
The Continuum ◽  
Refractive Index Detection

AbstractOne of the key challenges in biology is to understand how individual cells process information and respond to perturbations. However, most of the existing single-cell analysis methods can only provide a glimpse of cell properties at specific time points and are unable to provide cell secretion and protein analysis at single-cell resolution. To address the limits of existing methods and to accelerate discoveries from single-cell studies, we propose and experimentally demonstrate a new sensor based on bound states in the continuum to quantify exosome secretion from a single cell. Our optical sensors demonstrate high-sensitivity refractive index detection. Because of the strong overlap between the medium supporting the mode and the analytes, such an optical cavity has a figure of merit of 677 and sensitivity of 440 nm/RIU. Such results facilitate technological progress for highly conducive optical sensors for different biomedical applications.

Determination of Sulfonylurea Herbicides in Grains by Capillary Electrophoresis

1995 ◽  
Vol 78 (4) ◽  
pp. 1091-1096 ◽  
Author(s):  
Alexander J Krynitsky ◽  
Douglas M Swtneford
Keyword(s):  
Capillary Electrophoresis ◽  
Lower Limit ◽  
Limit Of Detection ◽  
Solid Phase ◽  
Residue Analysis ◽  
High Sensitivity ◽  
Sulfonylurea Herbicides ◽  
Optical Cell ◽  
Liquid Chromatographic ◽  
Tribenuron Methyl

Abstract A capillary electrophoresis (CE) method was developed to separate and determine residues of 5 sulfonylurea herbicides in grains (wheat, barley, and corn). This work demonstrated the practicality of using CE for residue analysis of sulfonylureas. The method yielded good recoveries and adequate sensitivities at tolerance levels (0.05–0.1 ppm). The compounds investigated were metsulfuron methyl (Ally), thifensulfuron methyl (Harmony), chlorsulfuron (Glean), rimsulfuron (DPX-E9636), and tribenuron methyl (Express). Acetonitrile extracts of grain samples were partitioned with hexane and then cleaned up with cation exchange solid-phase extraction cartridges. Quantitation was performed by micellar electrokinetic capillary chromatography using a high-sensitivity optical cell. Average recoveries at the 0.05 ppm level ranged from 72.9 to 118.5%. The lower limit of detection was approximately 0.02 ppm, except for rimsulfuron and tribenuron methyl, for which the lower limit of detection was 0.035 ppm. The method was less complicated and showed better sensitivity than current single-analyte liquid chromatographic enforcement methods.

scholarly journals Design and simulation of bio fluidic sensor based on photonic crystal

2014 ◽  
Vol 3 (2) ◽  
pp. 106
Author(s):  
Rajini Gaddam Kesava Reddy ◽  
Sharmila Ashok kumar ◽  
Sankardoss Varadhan
Keyword(s):  
Photonic Crystals ◽  
Photonic Band Gap ◽  
Optical Cavity ◽  
Fdtd Method ◽  
High Sensitivity ◽  
Three Dimensions ◽  
Fluidic Channel ◽  
Optical Cavities ◽  
Fluid Sensor ◽  
On Chip

Photonic crystals are materials patterned with a periodicity in dielectric constant in one, two and three dimensions and associated with Bragg scattering which can create range of forbidden frequencies called Photonic Band Gap (PBG). By optimizing various parameters and creating defects, we will review the design and characterization of waveguides, optical cavities and multi-fluidic channel devices. We have used such waveguides and laser nanocavities as Biosensor, in which field intensity is strongly dependent on the type of biofliud and its refractive index. This design and simulation technique leads to development of a nanophotonic sensor for detection of biofluids. In this paper, we have simulated sensing of biofliud in various photonic defect structures with the help of a numerical algorithm called Finite Difference Time Domain (FDTD) method. The simulation result shows the high sensitivity for the change in the bio-molecular structure. For developing the complete sensor system, we have to use the MEMS technologies to integrate on-chip fluidic transport components with sensing systems. The resulting biofluidic system will have the capability to continuously monitor the concentration of a large number of relevant biological molecules continuously from ambulatory patients. Keywords: FDTD, Photonic Crystals, Bio fluid Sensor, Optical Cavity.

scholarly journals Metallic Nanoparticle-Based Optical Cell Chip for Nondestructive Monitoring of Intra/Extracellular Signals

Pharmaceutics ◽  
2020 ◽  
Vol 12 (1) ◽  
pp. 50
Author(s):  
Sang-Nam Lee ◽  
Jin-Ha Choi ◽  
Hyeon-Yeol Cho ◽  
Jeong-Woo Choi
Keyword(s):  
Metallic Nanoparticles ◽  
High Sensitivity ◽  
Surface Enhanced Raman Spectroscopy ◽  
Localized Surface Plasmon ◽  
Nondestructive Monitoring ◽  
Metallic Nanoparticle ◽  
Optical Cell ◽  
Cell Chip ◽  
The Status ◽  
Sensitivity And Selectivity

The biosensing platform is noteworthy for high sensitivity and precise detection of target analytes, which are related to the status of cells or specific diseases. The modification of the transducers with metallic nanoparticles (MNPs) has attracted attention owing to excellent features such as improved sensitivity and selectivity. Moreover, the incorporation of MNPs into biosensing systems may increase the speed and the capability of the biosensors. In this review, we introduce the current progress of the developed cell-based biosensors, cell chip, based on the unique physiochemical features of MNPs. Mainly, we focus on optical intra/extracellular biosensing methods, including fluorescence, localized surface plasmon resonance (LSPR), and surface-enhanced Raman spectroscopy (SERS) based on the coupling of MNPs. We believe that the topics discussed here are useful and able to provide a guideline in the development of new MNP-based cell chip platforms for pharmaceutical applications such as drug screening and toxicological tests in the near future.

scholarly journals Characterization of the South Atlantic marine boundary layer aerosol using an aerodyne aerosol mass spectrometer

2008 ◽  
Vol 8 (16) ◽  
pp. 4711-4728 ◽  
Author(s):  
S. R. Zorn ◽  
F. Drewnick ◽  
M. Schott ◽  
T. Hoffmann ◽  
S. Borrmann
Keyword(s):  
Boundary Layer ◽  
Sulfuric Acid ◽  
High Resolution ◽  
Marine Boundary Layer ◽  
Methanesulfonic Acid ◽  
Field Measurements ◽  
Size Distributions ◽  
Air Masses ◽  
Unit Mass Resolution ◽  
Mass Concentrations

Abstract. Measurements of the submicron fraction of the atmospheric aerosol in the marine boundary layer were performed from January to March 2007 (Southern Hemisphere summer) onboard the French research vessel Marion Dufresne in the Southern Atlantic and Indian Ocean (20° S–60° S, 70° W–60° E). We used an Aerodyne High-Resolution-Time-of-Flight AMS to characterize the chemical composition and to measure species-resolved size distributions of non-refractory aerosol components in the submicron range. Within the "standard" AMS compounds (ammonium, chloride, nitrate, sulfate, organics) "sulfate" is the dominant species in the marine boundary layer with concentrations ranging between 50 ng m−3 and 3 μg m−3. Furthermore, what is seen as "sulfate" by the AMS is likely comprised mostly of sulfuric acid. Another sulfur containing species that is produced in marine environments is methanesulfonic acid (MSA). There have been previously measurements of MSA using an Aerodyne AMS. However, due to the use of an instrument equipped with a quadrupole detector with unit mass resolution it was not possible to physically separate MSA from other contributions to the same m/z. In order to identify MSA within the HR-ToF-AMS raw data and to extract mass concentrations for MSA from the field measurements the standard high-resolution MSA fragmentation patterns for the measurement conditions during the ship campaign (e.g. vaporizer temperature) needed to be determined. To identify characteristic air masses and their source regions backwards trajectories were used and averaged concentrations for AMS standard compounds were calculated for each air mass type. Sulfate mass size distributions were measured for these periods showing a distinct difference between oceanic air masses and those from African outflow. While the peak in the mass distribution was roughly at 250 nm (vacuum aerodynamic diameter) in marine air masses, it was shifted to 470 nm in African outflow air. Correlations between the mass concentrations of sulfate, organics and MSA show a narrow correlation for MSA with sulfate/sulfuric acid coming from the ocean, but not with continental sulfate.

scholarly journals Airborne formaldehyde measurements using PTR-MS: calibration, humidity dependence, inter-comparison and initial results

2011 ◽  
Vol 4 (4) ◽  
pp. 4631-4665 ◽  
Author(s):  
C. Warneke ◽  
P. Veres ◽  
J. S. Holloway ◽  
J. Stutz ◽  
C. Tsai ◽  
...  
Keyword(s):  
Los Angeles ◽  
Marine Boundary Layer ◽  
Operating Mode ◽  
Proton Transfer Reaction ◽  
Acquisition Time ◽  
Fast Time ◽  
Photochemical Degradation ◽  
Free Troposphere ◽  
Airborne Measurements ◽  
Humidity Dependence

Abstract. We present quantitative, fast time response measurements of formaldehyde (HCHO) onboard an aircraft using a Proton-Transfer-Reaction Mass-Spectrometry (PTR-MS) instrument. The HCHO measurement by PTR-MS is strongly humidity dependent and therefore airborne measurements are difficult and have not been reported. The PTR-MS instrument was run in the normal operating mode, where about 15 volatile organic compounds (VOCs) are measured together with HCHO onboard the NOAA WP-3 aircraft during the CalNex 2010 campaign in California. We compare the humidity dependence determined in the laboratory with in-flight calibrations of HCHO and calculate the HCHO mixing ratio during all flights using the results from both. The detection limit for HCHO was between 100 pptv in the dry free troposphere and 300 pptv in the humid marine boundary layer for a one second acquisition time every 17 s. The PTR-MS measurements are compared with HCHO measurements using a DOAS instrument and a Hantzsch monitor at a ground site in Pasadena. The PTR-MS agreed with both instruments within the stated uncertainties. We also compare HCHO enhancement ratios in the Los Angeles basin and in the free troposphere with literature values and find good agreement. The usefulness of the PTR-MS HCHO measurements in atmospheric observations is demonstrated by following an isolated anthropogenic plume. The photochemical production of HCHO can be observed simultaneously with production of acetaldehyde and the photochemical degradation of aromatic compounds using the PTR-MS.

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