Atomic force microscopy (AFM) has been widely used for characterizing nanoscale material properties of inorganic materials across various industries while there is broad interest in expanding AFM measurement capabilities for nanobiotechnology applications. An area of high priority involves studying the interactions of virus particles and viral proteins with cell membrane receptors in order to develop new classes of antiviral drug candidates. Herein, we developed an AFM-based force spectroscopy approach to measure the binding interactions between an AH peptide corresponding to the N-terminal amphipathic helix of the hepatitis C virus (HCV) NS5A protein and its cellular receptor, phosphatidylinositol (4,5)-bisphosphate [PI(4,5)P2], which is a phosphoinositide and the binding interaction is necessary for HCV viral genome replication. Various measurement parameters and the peptide conjugation scheme were first optimized and it was identified that the AH peptide demonstrated high binding specificity for PI(4,5)P2 receptors compared to other phosphoinositide receptors. It was further determined that a therapeutic drug candidate could prevent the interaction between AH peptide and PI(4,5)P2 receptors and the results agreed with biochemical assay data. Collectively, these findings demonstrate how AFM-based measurement capabilities can be useful for nanobiotechnology applications related to pharmaceutical drug screening, especially in the field of antiviral drug discovery and development.
Over the past three decades, AFM (Atomic Force Microscopy) has evolved into an ideal methodology for non-destructive sample scan with longer tip life, higher accuracy, repeatability, and automation. AFM is improving steadily so that it can be widely adopted like other microscopes, such as optics and scanning electron microscopes (SEM). In addition to the recent advances in AFM technology, it further expands the AFM application area by combining with other metrological technologies such as white interferometer (WLI) and photo-induced force microscopy (PiFM). By utilizing the vibration-isolated platform and the low noise z scanner of AFM, the performance of WLI has been greatly improved achieving unprecedented high z resolution. Hybridization of WLI and AFM provides us new possibilities in semiconductor and other industrial applications. The Photo-induced Force Microscopy (PiFM) is also integrated into 300mm AFM stage. PiFM can obtain chemical-specific nano-scale images and IR spectra by illuminating IR beam on the sample point of interest. I will also introduce preliminary data of various optical hybrid results from the prototype research grade hybrid AFM system.
van der Waals (vdW) heterostructures comprising two-dimensional (2D) crystals offer promising prospects for realizing ultrathin electronic and photonic devices with novel functionalities. Development of efficient and reliable light sources based on excitonic electroluminescence in 2D semiconductors is of fundamental importance toward the practical implementation of photonic devices. In this talk, I will focus on our approaches to realizing electrical generation of excitonic emissions based on vdW heterostructures. An efficient carrier-to-exciton conversion and planar electroluminescence are demonstrated in a metal-insulator-semiconductor (MIS) heterostructure consisting of few-layer graphene, hBN and monolayer WS2. Due to the unipolar tunnelling mechanism, selectively charged exciton emissions in monolayer WSe2 are further generated in this MIS-type light emitting devices (LED). Furthermore, on-chip linearly polarized LEDs are demonstrated by harnessing the anisotropic excitons from 2D semiconductors with reduced in-plane symmetry. Finally, I will highlight how scanning probe microscope could be utilized to improve the performance of the 2D LED devices.
Since atomic force microscopy (AFM) has been developed, it becomes novel technique for surface investigation including topography and other material properties measurement. AFM shows high utilization in the research field due to complementary relationships with optical microscopy, electron microscopy and other measuring equipment.
Kelvin Probe Force Microscopy (KPFM) is one of the well-known AFM modes that enables the monitoring of both surface morphology and surface potential distribution properties on a nanometer scale. KPFM has been utilized extensively to investigate the localized charge distributions on a surface layer, local surface potential distributions variations of surface work functions and ferroelectric domains, in a variety of research fields. Since the development of KPFM, it has become one of the more useful AFM options utilized by surface/material science and a variety of semiconductor industries. It is a unique technique for surface potential or work function mapping with nano-scale and their optional modes such as AM, Sideband, and Heterodyne have great advantages to explore a variety of material characterization with superior spatial resolution/improved electrical sensitivity.
In this study, we review overall information on KPFM including principle, optional modes, parameters, and application. In particular, we present results obtained with AM-KPFM, Sideband KPFM, and Heterodyne KPFM on well-defined samples with extended areas of different surface potentials. From these results, we directly compare the spatial resolution and image quality of AM-KPFM, Sideband KPFM, and Heterodyne KPFM under identical conditions.
Atomic Force Microscopy or AFM is an important tool in realizing the visualization of Nanotechnology by providing not just micrographs but much more aspects than other types of advanced microscopy techniques. As the material engineering advances the composite materials are becoming increasingly complicated and often a product can be made of multiple combination of many materials. NR based materials are of no exception! Whilst the bulk properties of such composite materials are measured, the intrinsic properties of individual material and the interactions of such neighbouring materials are undoubtedly contributing to the bulk properties. This type of localized properties can only be accessed using certain microscopic tools and AFM is surely one of the most suitable tools. NR/Graphene nanocomposites have been reported with enhanced surface electrical conductivity and Electrical AFM mode was used to probe the establishment of conductive site on the composite surfaces. AFM can also be used to study the coverage efficiency of coating materials on NR films where the distribution of coated materials was mapped using PinPoint Nanomechanical mode.
Functional ferroelectric thin films have been investigated for their potential application in electronic and optoelectronic devices. For instance, the bulk photovoltaic effect based on ferroelectricity promises above band gap photovoltages for photovoltaics. Furthermore, conductive domain walls between ferroelectric domains could act as charge carrier pathways lowering recombination rates and, thus, increase the charge collection in electronic devices.1–3
To correlate ferroelectric effects in domains on electronic and optoelectronic properties in ferroelectric functional materials vertical and lateral domains should be visualized with a high spatial resolution. The local piezoelectric information becomes available via piezoresponse force microscopy (PFM). For thin films, the weak piezoresponse can be enhanced by driving the electrical excitation of PFM close to the vertical (deflection) or lateral (torsion) contact resonance. Since the contact resonance depends on a consistent tip-sample contact a high surface roughness often introduces topographic crosstalk.4 Dual frequency resonance tracking (DFRT) improves the stability of the resonance enhancement.5 Here, we demonstrate our capabilities to capture the out-of-plane and in-plane DFRT piezoresponse simultaneously, by driving the electrical excitation of the cantilever at the contact resonance of the vertical deflection, as well as the torsional resonance on a thin film of the ferroelectric bismuth ferrite. Furthermore, we present a DFRT measurement on the active material in perovskite solar cells: methylammonium lead iodide.
The Department of Science and Technology-Industrial Technology Development Institute-Materials Science Division (DOST-ITDI-MSD) spearheads Research and Development (R&D) programs on materials essential to the development of local industries, generates quality R&D while harnessing the use of locally available resources in developing various materials for industrial purposes; and provides world class S&T services in materials science and engineering. DOST-ITDI-MSD houses the Nanotechnology Laboratory which is equipped with characterization tools for Nanotechnology Synthesis and Characterizations allowing research and development on materials science and engineering especially in the areas of new/advanced materials, surface engineering, and special materials.
Two types of porphyrin-imide dyads bearing different central metals (zinc and rhodium) have been synthesized and connected to carboxylic acid groups of single-walled carbon nanotubes (SWNTs) by a condensation reaction. The presence of the molecule was confirmed by atomic force microscopy (AFM) and transmission electron microscopy (TEM) using gold nanoparticles (AuNPs) as the marker of the molecules. Studies of the electronic properties using conductive AFM showed high rectification behavior up to 23 of average rectifying characteristic for zinc porphyrin-imide dyad. Here, a new method suited for wiring single molecule diodes using carbon nanotube as electrodes was successfully used resulting stable structure and strong connection of single molecule junctions with highly rectifying behavior. This result opens a new way for multi electrodes connection to a single molecule.
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