The bipolar diffusion charging of nanoparticles

A review and development of approaches for non-spherical particles

Ranganathan Gopalakrishnan, Peter H. McMurry, Christopher J. Hogan

Research output: Contribution to journalReview article

21 Citations (Scopus)

Abstract

Theoretical and experimental analyses of the steady state, bipolar diffusion charge distribution on nanoparticles are reviewed. This charge distribution plays a critical role in electrical mobility measurements of nanoparticle size distribution functions, where it is approximated via empirical regression equations. While the regression approach has been broadly successful, there remain several unresolved issues related to charge distribution calculations. Specifically, research to date has not revealed a method to reliably calculate nanoparticle-ion collision rates in the presence of strong attractive potentials, charge distribution predictions do not routinely consider the mass and (electrical) mobility distributions of the charging ions, and calculation approaches applicable to both spherical and nonspherical particles have not been compared to experimental data. In light of these issues, we examine the steady-state bipolar charge distribution on gold nanospheres and gold nanorods via tandem differential mobility analysis (TDMA). We compare measurements to regression equations as well as to Brownian Dynamics (BD) simulations, which take ion mobility and mass distributions as inputs. These distributions were measured using a DMA coupled to a mass spectrometer. Both regression equations and BD simulations are found to agree reasonably well with measurements in air, and we find that particle mobility diameter has a much greater influence on charging than particle morphology. Results support the use of BD calculations to predict bipolar charge distributions when ion properties are known. Nevertheless, our work supports continued use of regression equations when such information is not available.

Original languageEnglish (US)
Pages (from-to)1181-1194
Number of pages14
JournalAerosol Science and Technology
Volume49
Issue number12
DOIs
StatePublished - Dec 2 2015

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Charge distribution
Nanoparticles
Ions
Gold
ion
Nanospheres
Computer simulation
Mass spectrometers
Dynamic mechanical analysis
gold
Nanorods
Distribution functions
distribution
particle
nanoparticle
simulation
spectrometer
Air
collision
air

Cite this

The bipolar diffusion charging of nanoparticles : A review and development of approaches for non-spherical particles. / Gopalakrishnan, Ranganathan; McMurry, Peter H.; Hogan, Christopher J.

In: Aerosol Science and Technology, Vol. 49, No. 12, 02.12.2015, p. 1181-1194.

Research output: Contribution to journalReview article

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