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Amanda Luan, Ernesto Valdovinos, Joey WongMentor: Meysam R. BarmiAdvisor: Professor Carl D. MeinhartDepartment of Mechanical EngineeringUniversity of California, Santa Barbara

Applications of Stain Visualization• Detection of:o Explosiveso Pollutants in the airo Molecules in water• Biological and chemicalapplicationsportaec.net2

Purpose of Research• Characterize and testanalyte 4-ABT(4-aminobenzenethiol)stains• Determine bestcombination of variablesof nanoparticles formore accurate Ramanspectroscopy3

What is Raman Spectroscopy?• The investigation of Raman scattering to identifyparticles• Raman scattering uses a laser to shine monochromaticlight of a certain wavelength• Fast and accurate chemical detection1500Intensity100050000 200 400 600 800 1000 1200 1400 1600 1800 2000 2200Wave Number /cm -14

Creating Stains• 4-ABT exposureNanoparticle4-ABTDimerTrimerTetramer• Heat droplets whichcreates mixing due tothe Marangoni Effect• Mixing formsdimers, trimers,tetramers• Evaporation• Stain for analysis5

Lab Preparation• Wafer cleaning: acetone, isopropanol• Surface treatmentθθflouropolymer, teflonizationsilicon oxide6

Droplet Placement and Evaporation• Variables testedo Hydrophobic vs hydrophilic surfaceso 110 nm vs 20 nm nanoparticleso Volume of liquido Temperatureo Exposure time to 4-ABT7

Results: DetectionIntensity15001000500No 4-ABT molecules00 200 400 600 800 1000 1200 1400 1600 1800 2000 2200Wave Number /cm -1( )1/Wavelengthx 10 4 Wave number /cm -134-ABT molecules1588Intensity2100 200 400 600 800 1000 1200 1400 1600 1800 2000 2200( )1/Wavelength8

Stains on Silicon Surface20nm nanoparticles1:200 1:1001:50Concentrations9

Hydrophobic20nm nanoparticles.5 mm scaleHydrophilic20nm nanoparticles2 mm scale30-40°C30-40°C50-60°C50-60°C110nm nanoparticles.5 mm scale110nm nanoparticles2 mm scaleTypicalTypical10

Future Research• Continue to search for the optimal combination ofvariables for Raman spectroscopyo Different surfaces, temperatures, evaporations,sizes of nanoparticles• Later use other molecules other than 4-ABT11

Acknowledgements• Meysam R. Barmi• Professor Carl D. Meinhart• Summer Institute in Math and Science• California NanoSystems Institute12

Thank you for your attention13

Further Reading• “Free-surface microfluidic control of surface-enhancedRaman spectroscopy for the optimized detection ofairborne molecules“ by Piorek, Lee, Santiago,Moskovits, Banerjee, Meinharto 18898-18901, November 27, 2007, volume 104 no.4814

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