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Jiří Šperka, Marek Havlíček, Petr Klapetek

Characterization of Collected Aerosol CarbonaceousParticles using Atomic Force Microscopy

Atomic Force Microscopy (AFM) is common method for topographymeasurements of various samples including carbon containingnanomaterials or collected aerosol particles. Employment of AFMfor collected aerosol material is advantageous because of ambientmeasurement conditions, there are no problems with low pressure,sample charging or contamination that can occur during electronmicroscopy. However, for such measurements, good adhesion ofcollected aerosol particles to the substrate is crucial. Selectedsubstrate for collection of aerosol particles and other aspects ofcollecting proccess have impact on the final result. The aim of thiswork is to investigate possibilities of topography measurements ofindividual carbonaceous particles using AFM.

ACKNOWLEDGEMENTThe authors thank to Václav Hortvík for help with experiments. Work was supported by internal Czech MetrologyInstitute project n. 445190109.

Introduction & Motivation Results & Conclusions

AFM measurements were performed usingBruker Dimension Icon microscope. Firstsample (cigarette) was measured in tappingmode with RTESPA­150 AFM probe. Secondsample (lighter) was measured in two modes:(i) PeakForce tapping, (ii) Tapping mode,both with ScanAsyst­Air AFM probe. Samplefrom inverted generator was measured inPeakForce tapping mode with ScanAsyst­AirAFM probe. AFM data were evaluated inGwyddion (http://gwyddion.net/) ­ free AFMdata evaluation software.

Atomic force microscopy measurement was succcessful onsamples that were not fully covered with carbonaceous aerosolparticles. Comparison of AFM and electron microscopy images ofthird sample shows that AFM technique can be successfully usedfor high­quality topography measurements of carbonaceousparticles. Second sample was not suitable for AFMmeasurement, adhesion of particles to the sample was too low,electron microscopy is better technique for this type of samples.

23rd ETH­Conference on Combustion Generated Nanoparticles, June 17th ­ 20th, 2019, ETH Zurich, Switzerland

a) Cigarette b) Butane lighter c) Inverted generator

Particles Generation & Collection

Three different aerosol sources were used for particle generation:a) cigarette, b) common butane lighter and c) inverted sootgenerator from Argonaut Scientific that used a downward­flowingopen­tipped diffusion flame sustained by 70 sccm propane and 8SLM air flow. Particles were collected on glass substrates withoutany intended size pre­selection. For first two samples, the situationfor collecting of particles is on first two pictures below. First samplewas exposed for 4 minutes to cigarette smoke and second samplefor 15 seconds to the lighter. Collection of particles from invertedsoot generator proceeded inside generator exhaust tube indistance of 1.5 m from the generator, where the glass substratewas situated and exposed for 10 min to operating invertedgenerator.

AFM Measurement

Sample 1 ­ cigarette

Sample 2 ­ lighter

Sample 3 ­ inverted burner

Czech Metrology Institute, Brno, Czech RepublicDepartment of Primary Nanometrology and Technical Length

Contact: jsperka@cmi.cz, www.nanometrologie.cz

AFM images of first sample. Many small spherical particles with approximatediameter of 300 nm are visible on the left image. One large non­sphericalparticle on the right image.

Electron microscopy images of second sample. Glass substrate wasdensely covered with layer of soot. AFM image capture was not possibledue to attachment of sample material to the AFM tip.

AFM images and one electron microscopy (bottom right) image of thirdsample. Top left overview picture shows infrequent distribution of particleson glass substrate. Top right picture shows two connected particles. Bottompictures demonstare appearance of similar structures captured using AFMand electron microscopy.