System and method for single molecule detection

1. A single molecule sensing or detecting device comprising:

a first electrode; and

a second electrode separated from the first electrode by a gap, the first electrode and the second electrode having an opening formed therethrough;

wherein:

at least one of the first electrode and the second electrode is functionalized with at least one recognition molecule,

the recognition molecule having an effective length L1 and configured to selectively bind to a target molecule having an effective length L2,

the size of the gap is configured to be greater than L2, but less than or equal to the sum of L1 and L2, so that the gap is bridged by the target molecule bound by the at least one recognition molecule, thereby completing an electrical circuit.

2. The device of claim 1 , further comprising an insulating layer disposed in the gap, wherein a thickness of the insulating layer is less than or equal to the sum of L1 and L2.

3. The device of claim 1 , wherein the size of the gap is at least twice the effective length L1.

4. The device of claim 1 , wherein the size of the gap is equal to the sum of L1 and L2.

5. The device of claim 1 , wherein the size of the gap is between about 2 nm to about 15 nm.

6. The device of claim 1 , wherein the size of the gap is between about 2 nm to about 10 nm.

7. The device of claim 1 , wherein the size of the gap is between about 5 nm to about 15 nm.

8. The device of claim 1 , wherein the at least one recognition molecule comprises a peptide.

9. The device of claim 1 , wherein the at least one recognition molecule comprises a cyclic RGD peptide.

10. The device of claim 1 , where the size of the opening is between 0.1 nm and 100 microns in a linear dimension.

11. The device of claim 1 , wherein the first electrode and/or the second electrode are configured to generate a current upon binding of the target molecule, and wherein the current includes a fluctuating portion and/or a background portion.

12. The device of claim 1 , wherein the first electrode and the second electrode are collectively configured to generate a current upon binding of the target molecule, the current including a fluctuating portion and a background portion.

13. The device of claim 12 , wherein the background portion of the current is based on a number of non-target molecules adsorbed on the first electrode and/or on the second electrode.

14. The device of claim 12 , wherein:

the fluctuating portion is based on a concentration of the target molecule in a solution containing the target molecule,

the solution is in contact with the first electrode and the second electrode, and

the concentration of the target molecule in the solution is from about 10 fM to about 1 μM.

15. A method for sensing or detecting a target molecule, comprising:

applying a voltage bias across a first electrode and a second electrode of a molecular sensing or detecting device, the first electrode and second electrode collectively having an opening formed therethrough, wherein:

the second electrode separated from the first electrode by a gap,

at least one of the first electrode and the second electrode being functionalized with a recognition molecule,

the recognition molecule includes an effective length L1 and is configured to selectively bind to a target molecule having an effective length L2 so that the gap between the first electrode and second electrode is bridged when the target molecule binds to the recognition molecule, thereby completing an electrical circuit and generating a unique electrical recognition signal corresponding to the target molecule;

contacting the first electrode and the second electrode with a solution containing the target molecule in a concentration from about 10 fM to about 1 μM;

monitoring current generated between the first electrode and the second electrode over time; and

determining one or more of:

the presence of the target molecule; and

a number of non-target molecules adsorbed on the first electrode and/or on the second electrode.

16. The method of claim 15 , wherein determining the presence of the target molecule is based on a fluctuating portion of the current.

17. The method of claim 15 , wherein determining a number of non-target molecules adsorbed on the first electrode and/or on the second electrode is based on a background portion of the current.

18. The method of claim 15 , wherein:

the device further includes an insulating layer disposed in the gap, and

a thickness of the insulating layer is less than or equal to the sum of L1 and L2.

19. The method of claim 15 , wherein the gap is at least twice the effective length L1 in thickness.

20. The method of claim 15 , wherein the size of the gap is equal to the sum of L1 and L2.

21. The method of claim 15 , wherein the size of the gap is between about 2 nm to about 15 nm.

22. The method of claim 15 , wherein the size of the gap is between about 2 nm to about 10 nm.

23. The method of claim 15 , wherein the size of the gap is between about 5 nm to about 15 nm.

24. The method of claim 15 , wherein the recognition molecule comprises a cyclic RGD peptide.