Geometrical Characterization of Glass Nanopipettes with Sub-10 nm Pore Diameter by Transmission Electron Microscopy

Abstract

Glass nanopipettes are widely used for various applications in nanosciences. In most of the applications, it is important to characterize their geometrical parameters, such as the aperture size and the inner cone angle at the tip region. For nanopipettes with sub-10 nm aperture and thin wall thickness, transmission electron microscopy (TEM) must be most instrumental in their precise geometrical measurement. However, this measurement has remained a challenge because heat generated by electron beam irradiation would largely deform sub-10-nm nanopipettes. Here we provide methods for preparing TEM specimens that do not cause deformation of such tiny nanopipettes.

Electrostatic-Gated Kinetics of Rapid Ion Transfers at a Nano-liquid/Liquid Interface

“…As for nanopipettes, due to their small size, the effect of gravity is greatly reduced, making it difficult for water to come out of the tip. TEM results in Figure S2b show trace water remaining inside the nanopipettes even under vacuum conditions, 36 indicating the strong interactions between water and pipette walls. Thus, the pivot point of the interface is likely to be located at the inner pipette walls for nanopipettes, where the interface is a concave shape according to the θ value (Figure S6e).…”

“…Transmission Electron Microscopy Measurements. The nanopipette sample preparation for TEM measurements was performed according to procedures reported by Watanabe et al 36 The nanopipette tip was cut in the water droplet and moved to the proper position on the copper grid. A 1 wt % formvar solution (polyvinylformal dissolved in DCE) was used to fix the end of the pipette tip on the grid before imaging.…”

Recent Advances in the Glass Pipet: from Fundament to Applications

“…44,45 Shigyou and Sun et al optimized the pulling parameters to create sub-10 nm nanopipettes. 10,11 However, these methods could not provide sufficient control over nanopipette geometry. Atomic layer deposition (ALD) enabling to provide a precisely controllable thickness of deposited layers with a subnanometer resolution has been utilized for shrinking the solid state nanopore.…”

“…15 Moreover, a further optimization of TEM conditions realized the nondestructive characterization for a sub-10 nm nanopipette. 11 The earliest application of a pipet in physiology referred to the patch clumping technique to detect the membrane potential in the 1970s. Because of this important technique, it won the Nobel Prize for Physiology or Medicine in 1991.…”

“…Significantly, it enables tailoring the pore size from the microscale down to the nanoscale level. Especially, recent advances allow to a high degree control over the pore size and the achievement of a sub-10 nm nanopipette. , Simultaneously, the geometrical characterization of the nanopipette such as pore size and cone angle experiences from a rough estimation by scanning electron microscopy (SEM) , and electrical-resistance measurement to directly allow precise characterization by transmission electron microscopy (TEM) . Moreover, a further optimization of TEM conditions realized the nondestructive characterization for a sub-10 nm nanopipette …”