Particles in solution can be driven to translocate through nanopores/nanopipettes by a pressure difference and/or the application of a potential difference between internal and external electrodes. A translocating particle results in a resistive pulse (drop in the current between the two electrodes). For a conical geometry the resistive pulse is asymmetric, direction-dependent and gives information on many physical parameters of the particle; such as, the size, charge, deformability and shape of individual particles.
In the White group we have developed an understanding of the dynamics of particles travelling through pores, the forces involved, and the various ionic contributions to the shape of the resistive pulse. This understanding has enabled us to develop a multipass resistive pulse method, where we switch the pressure/voltage to repeatedly pass individual nanoparticles back and forth through the orifice of a conical nanopore/nanopipette. This leads to a precisely determined mean blocking current equating to sub-nanometer size resolution. We are currently exploring controlled delivery of single particles & molecules to electrochemical interfaces.
In addition, our group has developed a combined experimental/theoretical approach to investigate the dynamic physical and chemical interactions of individual suspended metal nanoparticles as they undergo electrochemical reactions at a microelectrode. To date, we have reported on the influence of Brownian motion on the electrochemical dissolution of single Ag nanoparticles as they collide with a polarized microelectrode. We explain the multimodal current vs. time responses by the Ag nanoparticle undergoing a series of discrete partial oxidation events as its random walk encounters the electrode surface.
Electrochemical Synthesis of Individual Core@Shell and Hollow Ag/Ag2S Nanoparticles
D. A. Robinson, H. S. White
Nano Lett. 2019. 19, 8, 5612-5619
Single Ag Nanoparticle Collisions within a Dual-Electrode Micro-Gap Cell
K. McKelvey, D. A. Robinson, N. J. Vitti, M. A. Edwards, H. S. White
Faraday Discuss., 2018, 210, 189-200
Effects of Instrumental Filters on Electrochemical Measurement of Single‐Nanoparticle
Donald Robinson, Martin A. Edwards, Hang Ren, and Henry S. White
ChemElectroChem, 2018, 5 (20), 3059-3067
Collision and Oxidation of Silver Nanoparticles on a Gold Nanoband Electrode
F. Zhang, M. Edwards, R. Hao, H. S. White, B. Zhang
J. Phys. Chem. C, 2017, 121 (42), pp 23564–23573
Three-Dimensional Super-resolution Imaging of Single Nanoparticles Delivered by Pipettes
Y. Yu, V. Sundaresan, S. Bandyopadhyay, Y. Zhang, M. A. Edwards, K. McKelvey, H. S. White, K. A. Willets.
ACS Nano, 2017, 11 (10), pp 10529–10538
S. M Oja, D. A. Robinson, N. J. Vitti, M. A. Edwards, Y. Liu, H. S. White, and B.
J. Am. Chem. Soc., 2017, 139 (2), 708–718.
Resistive Pulse Delivery of Single Nanoparticles to Electrochemical Interfaces
K. McKelvey, M. A. Edwards, and H. S. White
J. Phys. Chem. Lett., 2016, 7, 3920–3924.
Resistive-Pulse Analysis of Nanoparticles
L. Luo, S. R. German, W. Lan, D. A. Holden, T. L. Mega, and H. S. White
Ann. Rev. of Anal. Chem. , 2014, 7, 513-535.
A high-speed multipass coulter counter with ultra-high resolution
M. A. Edwards, S. R. German, J. E. Dick, A. J. Bard, and H. S. White
ACS Nano, 2015, 9 (12), 12274–12282.
Sizing Individual Au Nanoparticles in Solution with Sub-Nanometer Resolution
S. R. German, T. S. Hurd, H. S. White, and T. L. Mega
ACS Nano, 2015, 9(7), 7186-7194.
Effect of Surface Charge on the Resistive Pulse Waveshape during Particle Translocation
through Glass Nanopores
W. Lan, C. Kubeil, J. Xiong, A. Bund, and H. S. White
J. Phys. Chem. C. , 2014, 118(5), 2726-2734.
Controlling Nanoparticle Dynamics in Conical Nanopores
S. R. German, L. Luo, H. S. White, and T. L. Mega
J. Phys. Chem C, 2013, 117(1), 703-711.