Kyoto University · Engineering
Professor Takashi Ichii's research lab specializes in advanced atomic force microscopy (AFM) techniques, particularly frequency modulation AFM (FM-AFM) and Kelvin probe force microscopy (KFM), to investigate interfacial structures at the nanoscale. The lab focuses on probing complex liquid-solid and polymer-solid interfaces, including ionic liquids, water-in-salt electrolytes, self-assembled monolayers, and viscoelastic polymers like PDMS. By employing high-Q quartz tuning fork (qPlus) sensors, the lab achieves atomic-resolution imaging and quantitative nanomechanical and nanoelectrical characterization in challenging environments such as highly viscous or concentrated electrolytes. Their work provides fundamental insights into solvation structures, interfacial dynamics, and surface potential variations critical for energy storage and nanomaterials applications.
Figures are computed from collected data and may differ slightly.
Frequency modulation atomic force microscopy (FM-AFM) imaging in ionic liquids (ILs) were carried out. A quartz tuning fork sensor with a sharpened tungsten tip was used as a force sensor instead of a Si cantilever. Only the tip apex was immersed in ILs and the quality factor of the sensors was kept more than 100 in spite of the high viscosity of ILs. Atomic-resolution topographic imaging was successfully achieved in an IL as well as in an aqueous solution. In addition, frequency shift versus ti
Structural analysis of interfaces between ionic liquid (IL) and alkali-halide (100) surface was demonstrated by frequency modulation atomic force microscopy (FM-AFM). A quartz tuning fork sensor with a sharpened tungsten tip, the so-called qPlus sensor, was used as a force sensor. Atomic-resolution topographic imaging on a KCl(100) surface was successfully achieved in a viscous IL. The square lattice structure with a period of ∼0.4 nm was clearly imaged, which indicated that only K+ or Cl– ions
We investigated alkanethiol phase-separated self-assembled monolayers (PS-SAMs) using the Kelvin probe force microscope (KFM) combined with the non-contact atomic force microscope (NC-AFM). PS-SAMs were composed of two species of different chain-length alkanethiol. The surface potential (SP) measurements showed that the value of SP was linearly increased as a function of the chain length and that the gradient was about 9 mV per CH2 unit. In addition, we succeeded in obtaining nanometre-scale var
Frequency modulation atomic force microscopy (FM-AFM) imaging in ionic liquids (ILs) were carried out. A quartz tuning fork sensor with a sharpened tungsten tip was used as a force sensor instead of a Si cantilever. Only the tip apex was immersed in ILs and the quality factor of the sensors was kept more than 100 in spite of the high viscosity of ILs. Atomic-resolution topographic imaging was successfully achieved in an IL as well as in an aqueous solution. In addition, frequency shift versus ti
Abstract We investigated a polymeric liquid/solid interface by frequency modulation atomic force microscopy (FM-AFM) using a quartz tuning fork sensor, so-called qPlus sensor. We carried out topographic imaging on a muscovite mica surface in poly(dimethylsiloxane) (PDMS) which has 1000 times higher viscosity than that of water and the crystal structure of the mica surface was successfully imaged. Two-dimensional frequency shift mapping was also demonstrated at the interface and the layered struc
Abstract Water-in-salt electrolytes (WiSEs), which contain salt with extremely high concentration (>20 mol kg −1 ), are attracting much interest as new electrolytes for energy storage systems, especially for lithium-ion batteries (LIBs), because they are considered to be suitable for developing safer systems. Structural analysis on WiSE/solid interfaces would provide beneficial information for developing LIBs. Whereas the interfacial structures of diluted aqueous electrolytes (less than 1 mol
Abstract Simultaneous detection of vertical and lateral forces at the nanoscale by atomic force microscopy (AFM) yields important knowledge on nanotribology. Although silicon (Si) cantilevers are capable of detecting both the forces, it has not been achieved by quartz tuning fork sensors including qPlus sensors. In this study, we found that the tip apex of the qPlus sensor with a long tip oscillates vertically at the lowest resonance frequency (ƒ 1 ) and laterally at the second lowest resonance
Abstract Molecular-resolution imaging on an alkanethiol self-assembled monolayer (SAM) in an ionic liquid (IL) was demonstrated using frequency modulation atomic force microscopy (FM-AFM). A quartz tuning fork sensor with a sharpened tungsten tip, the so-called qPlus sensor, was used as a force sensor. Etch pits, which are a typical structure of alkanethiol SAMs, individual alkanethiol molecules, and single molecular defects were clearly imaged; that is, true molecular-resolution imaging was suc
Lead phthalocyanine molecules on MoS2(0001) substrates were imaged using an ultrahigh-vacuum AFM apparatus equipped with an optical beam deflection (OBD) sensor. The second flexural mode was employed to utilize its high effective spring constant in order to reduce the oscillation amplitude to 0.5 nm without oscillation instability. Submolecular-resolution images were obtained when a shorter cantilever, which had a very high resonance frequency and a low noise equivalent deflection in the OBD sen
The detection of vertical and lateral forces at the nanoscale by atomic force microscopy (AFM) reveals various mechanical properties on surfaces. The qPlus sensor is a widely used force sensor, which is built from a quartz tuning fork (QTF) and a sharpened metal probe, capable of high-resolution imaging in viscous liquids such as lubricant oils. Although a simultaneous detection technique of vertical and lateral forces by using a qPlus sensor is required in the field of nanotribology, it has sti
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