page_title: Probe tip
section_title: Applications
hierarchical_section_title: Probe tip / Applications
caption_attribution_description: English: Water Single Atom
context_page_description: A probe tip in scanning microscopy is a very sharp object made from metal or other materials, like a sewing needle with a point at one end with nano or sub-nanometer order of dimension. It can interact with up to one molecule or atom of a given surface of a sample that can reveal authentic properties of the surface such as morphology, topography, mapping and electrical properties of a single atom or molecule on the surface of the sample.
  The proliferation of the thrust in probe-based tools began after the invention of the scanning tunneling microscope and atomic force microscopy by Gerd Binnig and Heinrich Rohrer at the IBM Zurich research laboratory in 1982. It opened a new era for probing the nanoscale world of individual atoms and molecules as well as studying surface science, due to their unprecedented capability of characterizing a wide range of unique properties such as mechanical, chemical, magnetic and optical functionalities of various samples at nanometer-scale resolution in a vacuum, ambient or fluid environment. The utilization of sharp probe tips enabled the researcher to see inside the microscopic world from within the macroscopic world.
context_section_description: Probes tips have a wide variety of applications in different fields of science and technology. One of the major areas where probe tips are used is for application in SPM i.e., STM and AFM. For example, carbon nanotube tips in conjunction with AFM provides an excellent tool for surface characterization in the nanometer realm. CNT tips are also used in tapping-mode Scanning Force Microscopy (SFM), which is a technique where a tip taps a surface by a cantilever driven near resonant frequency of the cantilever. The CNT probe tips fabricated using CVD technique can be used for imaging of biological macromolecules, semiconductor and chemical structure. For example, it is possible to obtain an intermittent AFM contact image of IgM macromolecules with excellent resolution using a single CNT tip. Individual CNT tips can be used for high resolution imaging of protein molecules.
  In another application, multiwall carbon nanotube (MWCNT) and single wall carbon nanotube (SWCNT) tips were used to image amyloid β (1-40) derived protofibrils and fibrils by tapping mode AFM. Functionalized probes can be used in Chemical Force Microscopy (CFM) to measure intermolecular forces and map chemical functionality. Functionalized SWCNT probes can be used for chemically sensitive imaging with high lateral resolution and to study binding energy in chemical and biological system. Probe tips that have been functionalized with either hydrophobic or hydrophilic molecules can be used to measure the adhesive interaction between hydrophobic-hydrophobic, hydrophobic-hydrophilic, and hydrophilic-hydrophilic molecules. From these adhesive interactions the friction image of patterned sample surface can be found. Probe tips used in force microscopy can provide imaging of structure and dynamics of adsorbate at the nanometer scale. Self-assembled functionalized organic thiols on the surface of Au coated Si₃N₄ probe tips have been used to study the interaction between molecular groups. Again, carbon nanotube probe tips in conjunction with AFM can be used for probing crevices that occur in microelectronic circuits with improved lateral resolution. Functionality modified probe tips has been to measure the binding force between single protein-ligand pairs. Probe tips have been used as a tapping mode technique to provide information about the elastic properties of materials. Probe tips are also used in the mass spectrometer. Enzymatically active probe tips have been used for the enzymatic degradation of analyte. They have also been used as devices to introduce samples into the mass spectrophotometer. For example, trypsin-activated gold (Au/trypsin) probe tips can be used for the peptide mapping of the hen egg lysozyme.
  Atomically sharp probe tips can be used for imaging a single atom in a molecule. An example of visualizing single atoms in water cluster can be seen in Fig. 10. By visualizing single atoms in molecules present on a surface, scientists can determine bond length, bond order and discrepancies, if any, in conjugation which was previously thought to be impossible in experimental work. Fig. 9 shows the experimentally determined bond order in a poly-aromatic compound which was thought to be very hard in the past.
caption: Fig. 10: (a) Schematic of STM/AFM measurement for pentagonal water chains on Cu(110) with a CO-terminal tip. Red, black, white and brown spheres show O, C, H and Cu atoms, respectively. (b) Side-view schematic of the water chain. Red (yellow) spheres represent O atoms of horizontal (vertical) H2O. (c) STM image of the water chains on Cu(110) with a CO-terminal tip (sample bias V=30 mV, tunneling current I=20 pA). The zigzag chains have terminals (red ellipses). (d,e) STM (V=30 mV, I=20 pA) and AFM (V=0 mV, oscillation amplitude A=2 Å) images, respectively, of a water chain including a kink and a terminal. An atomic structure of the chain is superposed in d. The tip height in e was set over the bare surface under the same conditions as in d. (f) Δf map of the pentagonal chain at a tip height Δz=−2 Å (A=1 Å). (g) Δf(Δz) curves recorded over the markers in f. (h) Force map of the chain at Δz=−1.95 Å after subtraction of the force for the bare surface FCu. (i) Force curves over the makers in f after subtraction of FCu(Δz). Scale bars, 50 Å (c); 10 Å (d,e); 3 Å (f,h).[104]
exif: {}