Tetracyanoplatinate Scanning Probe Microscope Tips
Tags: MI# 326
My idea is for a new type of scanning probe microscope (SPM) which could be used for 'picking up' molecules by expressing patterns of electrical charge on its tip that were complementary to the patterns of charge on the surfaces of molecules. The probe tips would be made from tetracyanoplatinate (TCP) salt crystals. These crystals consist of straight adjacent stacks of TCP units, each of which is a platinum atom surrounded at the corners of a square by four carbons each triple bonded to a nitrogen, together with positive metal ions. TCP salt crystals are anisotropic and patterns of electrical charge set at one end would be expressed identically at the other. Here is a suggested set of instructions on how to fabricate and wire a TCP probe microscope:
1. Place a thin metallic lid on a TCP group/positive ion aqueous solution.
2. Apply a positive electrode to a point on the lid with the negative electrode immersed in the solution thus causing a roughly shaped TCP needle to grow under that point.
3. Carefully photoetch a small patch of the lid to expose some of the TCP stacks.
4. Using a scanning tunneling microscope (STM) apply pulsed charges to individual TCP stacks at the (inverted) base of the needle until the growing end of the needle was in contact with the negative electrode.
5. Carefully break off the negative electrode and drain the solution. If the electrode was (atomically!) flat and the break was clean this would leave a flat TCP probe tip of the correct dimensions.
6. Invert the TCP probe and immerse the base in a solution of conductive polymers in a container the base of which has incorporated within it a microchip with several of its circuits terminating on the surface exposed to the solution.
7. Using an STM apply a charge to the end of a TCP stack and simultaneously oppositely charge one circuit terminal so that a single polymer molecule formed a bridge between the two. Repeat this action until all of the desired stacks had been connected to circuits.
8. Add calcium carbonate to the solution and by cooling or the addition of a catalyst proceed with calcification until the polymer wires had been completely embedded.
For greater detail please refer to the attached file.
Mark Hanlon
| Attachment | Size |
|---|---|
| A Path to Molecular Control.doc | 41 KB |
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Can I safely assume that this process requires both vaccumm and otherwise very invasive sample pre-treatments for readability: that there need be deposition coating, etc., and not just the tip preparation standing alone to make observations. Would the process be inherently ultimately fatal/destructive to organisms under observation? Can this possibly be used and or adapted to non-lethal observations of cells in vivo? I am interested in clinical pharmaceutical trial applications.
I have a few questions of a general nature. . .
Has your posted material been peer reviewed? If not yet, do you intend to do so and where?
More substantively: do you believe that the proposed probe termini are readable by currently available or adaptable technologies? What are this application's unique practical benfits over existing nano-observation protocols?
Hello KoKoKCB,
At the moment the proposal has not been peer reviewed. Traditionally peer review has applied to accounts of experiments that have been carried out. Since this is not the case a peer review would conclude that the proposal should be carried out or that there is something fundamentally wrong with the underlying theory. I do not think that the latter applies because, as set out in the attached file, any attempt to think systematically about how to work with individual molecules would result in something equivalent to the TCP probe. Having said this, I did not come up with the idea by 'deriving' it.
I have been working on the idea on and off since 2001 and the essay here is the final version. I posted the idea on this website after submitting it to the organizers of a conference to be held in Canada in June, so I will see if they want to go ahead with it.
I know for a fact that the probe termini are readable with scanning tunnelling microscopes (STMs) because I once did a web search and found an STM image of the end of a TCP crystal. It looked exactly as would be expected; highly conductive, regularly spaced patches surrounded by unconductive areas. The image was from the Sandia National Laboratory but may now be offline.
This application's main practical benefit would be that there are no other ways (yet) of picking up molecules. As yet only atoms or simple molecules have been 'picked up' and moved around with probe microscopes. The TCP probe is a beginning, and it would be relatively simple to develop.
Hope this helps!
Did you go to that conference, and if so, how did you make out? It seems like a great idea you have. . .
I didn't go to that conference but I was at Bristol University last Thursday (20/9/07) for an open day at the Physics Department. The subject was optical tweezers which has no obvious connection with probe microscopy but I had a chat with Mervyn Miles about the TCPM idea. His department is I think the most important SPM research centre in the UK. He was familiar with various conductive polymers so we talked about how the wiring process described above could be successfully carried out. He said that the first steps would be to repeat the experiment done by Tao and He in Arizona and then to wire up one TCP stack. I got the impression that this would be a natural continuation of work they have been doing before now so hopefully they will have a prototype within a few years. I will of course be monitoring progress!