Raman Spectroscopy of Tungsten Trioxide and COMSOL© Computer Simulation in Gas Sensor Technology

C. CraigMentor: Dr. P. MisraREU Team Members: R. Garcia-Sanchez, Dr. D. Casimir, S. BartleySummer 2015 REU ProgramHoward University Department of Physics and Astronomy

Outline• Motivation for research• Background:• What are semiconducting metal oxide gas sensors?• How are optical gas sensors used today?

• What is Raman Spectroscopy?• Research methodology and Results• Comsol© Simulation• Conclusions and Future Research

Why use spectroscopy in gas sensing?

• Semi-conducting metal oxide gas sensors are • Small • Portable• Cheap• But inefficient

• Optical gas sensors will • Improve time-efficiency• Improve precision of concentration detection

Semiconducting Metal-Oxide Gas Sensors [1]

• Composition:• Thin film layer of

semiconducting metal oxide• Substrate• Heating track

Carbon Dioxide Sensor http://www.futurlec.com/Gas_Sensors.shtml

Fine et al. 2010

Changes in Resistivity

• Semiconducting metal-oxide gas sensors use changes in resistivity to detect the presence of certain gases

http://www.ipm.fraunhofer.de/content/dam/ipm/en/PDFs/Product%20sheet/GP/ISS/semiconductor-gas-sensors.pdf

Optimal Operating Temperature

• Optimal gas detecting temperatures differ depending on the gas

• ZnO detects• Chlorobenzene at

~200°C• Ethanol at ~380°C

Optical Gas Sensors Used Today

Mars Land Rover http://news.rpi.edu/content/2013/09/26/nasa-mars-rover-curiosity-finds-water-first-sample-planet-surface

What is Raman Spectroscopy?• Study of the interactions of matter and light (visible and

invisible)• Raman Spectroscopy uses monochromatic light to identify

molecules based on light scattering from the vibration that occurs between bonded atoms in lattice structures.

Tungsten Trioxide Monoclinic Lattice Structure

• Atoms bond in a lattice structure to form solids.• Bonds vibrate at different frequencies.• Vibration-laser beam interaction creates spectral lines.

Bignozzi et al. 2012

Fingerprint of WO3• The major Raman peaks of Tungsten Trioxide are 808, 719,

and 274 cm-1.• These peaks result from the W-O stretching mode, the W-O

bending mode, and the W-O-W deformation mode, respectively, in the lattice structure.

https://www.mdsp.org/

Methodology• A DXR Smart Raman

spectrometer• 780 nm laser

• OmnicTM Specta Software• Ventacon H-4-200 Sealed

Hot Cell • Tungsten Trioxide Sample

Temperature Controlled Environmental Chamber

Objective Lens

Sample

Collection Lens Notch Filter

Imaging Spectrometer CCD

Detector

CW Laser (780 nm)

780 nm Narrowband

Mirror

P. Misra et al. 2015

www.ventacon.com/hotcell/hotcell2.htm

P. Misra et al. 2015

Results• The peaks exhibited a slight red-shift in

frequency as the temperature increased from 30 to 200°C.

P. Misra et al. 2015

Red-Shift in Frequencies

20 60100

140180

220269

270

271

272

273

274

275

276

f(x) = − 0.0172444444444445 x + 275.026888888889

f(x) = − 0.0178754785868941 x + 275.804865367694

274 Peak v. Temp

Peak 3 v. Temp upLinear (Peak 3 v. Temp up)Peak 3 v. Temp downLinear (Peak 3 v. Temp down)

20 60100

140180

220716

716.5

717

717.5

718

718.5

719

719.5

720

f(x) = − 0.0038444444444412 x + 718.566222222221

f(x) = − 0.00426088630812932 x + 719.270089542861

718 Peak v. Temp

Peak 2 v. Temp upLinear (Peak 2 v. Temp up)Peak 2 v. Temp downLinear (Peak 2 v. Temp down)

20 60100

140180

220805

805.5

806

806.5

807

807.5

808

808.5

809

f(x) = − 0.00381111111111346 x + 807.732222222222

f(x) = − 0.00598394795245358 x + 808.767380030199

808 Peak v. Temp

Peak 1 v. Temp up/F 1350Linear (Peak 1 v. Temp up/F 1350)Peak 1 v. Temp down/F 1500Linear (Peak 1 v. Temp down/F 1500)

Slopes:• 808 peak: -0.006, -0.038• 718 peak: -0.0043, -0.0038• 275 peak: -0.0179, -0.0172

Discussion of Results• The decrease in frequency • Thermal expansion• Phonon Interactions

• Temperature uncertainty at extremity of hot cell. • Use of Comsol© Simulation to resolve uncertainty.

Comsol© Simulation of Hot Cell• Build geometry• Apply materials and physics• Run simulations

Simulation Results

Multislice Electric Potential (V)Surface Temperature (K)

Isosurface Temperature (K)

Future Work and Goals• Tungsten Trioxide samples will be exposed to SO2 and NO gas

and the resulting Raman spectra will be taken.• These spectra will be compared to the WO3 spectra previously

gathered.• Relate intensity to concentration.

• Break into the gas sensor industry with optical sensors• Miniaturized• Fingerprint indicates the gas• Intensity of spectral lines indicates concentration

Acknowledgments

• NSF Funding• My mentor, Dr. P. Misra• My REU Team Members: R. Garcia, Dr. D. Casimir, S.

Bartley

Bibliography[1] http://www.ipm.fraunhofer.de/content/dam/ipm/en/PDFs/Product%20sheet/GP/ISS/semiconductor-gas-sensors.pdf

[2] Raul Garcia. Ph.D. Dissertation

[3] inphotonics.

Carbon Dioxide Sensor http://www.futurlec.com/Gas_Sensors.shtml

Bignozzi CA, Caramori S, Cristino V, Argazzi R, Meda L, Tacca A. 2013. Nanostructured photoelectrodes based on WO3: applications to photooxidation of aqueous electrolytes. Royal Society of Chemisty 42, 2228–2246.

Misra P, Casimir D, Garcia-Sanchez R, Balinga S. Raman spectroscopic characterization of carbon nanotubes & tungsten oxide of relevance to energy storage and gas sensing applications. Poster session presented at: Name of Convention. Number of conference; 2015 June 15; Lake Forest, CA.

Wang C, Yin L, Zhang L, Xiang D, Gao R. 15 March 2010. Metal oxide gas sensors: sensitivity and influencing factors. Sensors (10): 2088-2106.

Shimizu Y, Egashira M. 1999. Basic aspects and challenges of semiconductor gas sensors. MRS Bulletin. 18-24.

Xie S, Inglesia E, Bell AT. 2001. Effects of Temperature on the Raman Spectra and Dispersed Oxides. J. Phys. Chem B. 105(22): 5144-5152.

Liu X, Cheng S, Hong L, Hu S, Zhang D, Ning H. 2012. A survey on gas sensing technology. Sensors.

Fine GF, Cavanagh LM, Afonja A, Binions R. 2010. Metal Oxide Semi-Conductor Gas Sensors in Environmental Monitoring. Sensors (10): Basel, Switzerland, 5469–5502.

Lou, LF. 2003. Introductions to Phonons and Electrons. Singapore: World Scientific Publishing Company.

Author(s). Date. Title. Edition. Place of publication: publisher. Extent. Notes.

• Leboffe MJ, Pierce BE. 2010. Microbiology: laboratory theory and application. Englewood (CO): Morton Publishing Company.• (Leboffe and Pierce 2010)