Schematic of the procedure of the dual-wire technique for attaching a particle to the tip of an AFM cantilever. (a) One wire (a micropipette here) picks up a small drop of glue. (b) The glue is applied to the cantilever. (c) The other wire picks up a colloidal particle. (d) The particle is positioned on the glue spot on the cantilever. Copied with permission from Mak et al. (Ref. 13). Copyright 2006 American Institute of Physics.
SEM image of a titanium sphere attached to the end of a tipless rectangular AFM cantilever. Copied with permission from Mak et al. (Ref. 13). Copyright 2006 American Institute of Physics.
The setup and the procedure of the cantilever-moving technique. (a) The setup of the probe holder. The U-shaped clip holding an AFM probe is glued to a glass pipette that is inserted into the arm of a 3D manipulator. (b) The top (left) and the side (right) view of the clip holding the probe. (c) When monitored through an optical microscope, the probe is positioned close to the edge of a small puddle of glue, lowered to press slightly against the glass slide, and pushed into the glue so that only the tip touches the glue; the probe is then pulled out to drag off the excess glue along the glass slide. (d) The tip is positioned on the top of a sphere (a glass sphere here), lowered vertically to touch the sphere, and then lifted up. For a pyramid-shaped tip, ideally the sphere can be attached to the foreside of the tip, as illustrated in (a).
A borosilicate glass sphere (about in diameter) sintered to a tipless silicon cantilever at for . Image courtesy of Bonaccurso (Ref. 18).
Clusters of ceria nanoparticles (size of individual particles: ) have been attached to the tip of an AFM cantilever using the cantilever-moving technique. (a) Topography of the clusters obtained by scanning (reverse imaging) a grating with spikes sharper than the cluster, showing that the cluster is composed of multiple individual nanoparticles. Image size: . (b) The cross-sectional profile. Image courtesy of Sokolov (Ref. 20).
SEM pictures of Au nanoparticles attached to the tip of a silica SNOM tip with the “inverse self-assembly” technique. (a) Top view of an attached single Au particle (indicated by the arrow) of around in diameter. (b) Top view when multiple Au particles have been attached. Note that in the original paper the two images were mistakenly transposed. Copied with permission from Sqalli et al. (Ref. 22). Copyright 2006 American Institute of Physics.
(Color) The procedure of the wet surface-assembly technique. There are four steps for attaching a single nanoparticle. (A) The surface of the tip was made chemically passive by silanization with a monolayer of phenethyltrichlorosilane. (B) The passivation layer at the end of the tip was removed to expose a fresh native oxide surface by scanning the tip against a clean silica wafer surface. (C) The exposed surface reacts with 3– methacryloxypropyltrimethoxysilane (3-MPTS) silane to form a monolayer. (D) The tip is dipped into the Au nanoparticle suspension to allow a single nanoparticle to covalently bond to the tip. In the shortened procedure, as indicated by the dashed arrow, the phenethyltrichlorosilane (PETS) silanization step is omitted; however, multiple nanoparticles deposit on all sides instead of only at the end of the tip. Copied with permission from Vakarelski and Higashitani (Ref. 23). Copyright 2006 American Chemical Society.
Typical SEM images of a tip before and after the attachment of Au nanoparticles. (a) A fresh tip. (b) Multiple Au nanoparticles attach to the tip following the shortened procedure. (c) A single nanoparticle attaches to the end of the tip following the four step procedure. (d) A single nanoparticle might attach to the end of the tip following the shortened procedure. Copied with permission from Vakarelski and Higashitani (Ref. 23). Copyright 2006 American Chemical Society.
The water-flow suction technique. (a) A microtube is immersed in an aqueous suspension of nanoparticles. The water flow induced by either the capillary force or pumping drives the particles towards the microtube’s orifice. A particle larger than the orifice will be trapped at the orifice. (b) A series of pictures showing a particle moving towards the orifice. (c) SEM picture of the end of a microtube showing that the inner diameter of the orifice is about . (d) SEM picture of a microtube with an attached gold nanoparticle at the end. Copied with permission from Kawata et al. (Ref. 24). Copyright 2003 American Institute of Physics.
The in situ picking-up technique. (a) A confocal image of gold particles that are spin coated on a glass slide. The particle marked with the arrow will be targeted and approached with the tip under shear-force control. (b) SEM image of a single particle that is picked up and attached to the end of the tip. The tip is coated with a monolayer of polyethylenimine as adhesive. (c) The repeated confocal scan of the same area verifies that the particle has indeed been picked up and is missing from the glass slide. Copied with permission from Kalkbrenner et al. (Ref. 25). Copyright 2001 Blackwell Publishing.
Optical tweezers technique. (a) A microtubule (MT) is fixed on a gold substrate via covalently grafting with a self-assembled monolayer. The operation is carried out under an optical microscope. (b) The sequence of positioning (first frame) and attaching (second frame) of a fluorescent bead (indicated by the arrow) to the tip of a grafted MT. Frame 3 is the fluorescence image of the bead after changing the filter. Copied with permission from Pampaloni et al. (Ref. 27). Copyright 2006 National Academy of Sciences, U.S.A.
SEM picture of the tip of a nanopipette with a Ag nanoparticle deposited by the chemical reaction deposition technique. (Note that solutions come out from two orifices below the nanoparticle.) Copied with permission from Barsegova et al. (Ref. 29). Copyright 2002 American Institute of Physics.
Illustration of the photocatalytic deposition technique. A silicon nitride tip with an oxidized surface layer is irradiated by ultraviolet light to form metallic Au by reducing ions by the photocatalytic effect in the aqueous solution of tetrachloroauric acid . To limit the reaction to the apex of the tip, the tip is illuminated with the evanescent wave that is generated by the attenuated total reflection of a He-Cd laser beam at the prism/electrolyte interface. Copied with permission from Okamoto and Yamaguchi (Ref. 30). Copyright 2001 Blackwell Publishing.
SEM images of a tip before (a) and after (b) the deposition of a Au nanoparticle (indicated by the arrow) prepared by the photocatalytic deposition technique. Copied with permission from Okamoto and Yamaguchi (Ref. 30). Copyright 2001 Blackwell Publishing.
SEM image of a elliptical Au nanoparticle fabricated by the FEB induced deposition technique. Copied with permission from Sqalli et al. (Ref. 31). Copyright 2002 American Institute of Physics.
Comparison between techniques for attaching a single microparticle and nanoparticle to the tip of an AFM or SNOM probe.
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