Molecular detection based on conductance quantization of nanowires

Abstract

We have studied molecular adsorption onto stable metallic nanowires fabricated with an electrochemical method. Upon the adsorption, the quantized conductance decreases, typically, to a fractional value, which may be attributed to the scattering of the conduction electrons by the adsorbates. The further conductance change occurs when the nanowire is exposed to another molecule that has stronger adsorption strength. Because the quantized conductance is determined by a few atoms at the narrowest portion of each nanowire, adsorption of a molecule onto the portion is enough to change the conductance, which may be used for chemical sensors.

Nanogap Electrodes

“…The feedback signal, taking an electroplating method as an example, is frequently the current flowing through the gap electrodes, which is monitored during the deposition process. [35,[59][60][61][62][63][64][65][66] When the electrodes are very close but not yet touching, the monitor current is extremely sensitive to electrode distance, so it is easy to control the separation on an atomic scale by stopping the electrodeposition process at predefined conductance values. Unlike a current-feedback mode that uses both facing electrodes as a working electrode (WE), Tian et al [58] invented a method for the controllable electrochemical fabrication of electrodes with a nanometer/angstrom-sized gap using the potential distribution in the electric double layer as feedback, wherein two facing electrodes served as the working electrode and reference electrode (RE), respectively.…”

Mechanisms of molecular electronic rectification through electronic levels with strong vibrational coupling

“…II. Other cases for facile asymmetric current/bias voltage relations and electron flow along molecular wires, could include: ͑a͒ self-assembled condensed porphyrin complexes; 62,63 ͑b͒ condensed aromatic ring systems, 9,64 and multiply functionalized thiolates; 20 ͑c͒ carbon nanotube systems; 8,65,66 ͑d͒ supramolecular ladders and other arrays of large transition metal complexes; 67,68 ͑e͒ single molecules in metallic nanogaps; 69,70 ͑f͒ differential resistance patterns in adsorbed heteropolytungstate complexes; 71 ͑g͒ molecular photodiodes; 13,14,72 and ͑h͒ perhaps axial conduction along doublestranded oligonucleotides. 73 We conclude by addressing briefly recent data for current rectification in monolayers of hexadecyl-quinolinium tricyanodimethanide, 11,12,30 the following features of which are important in relation to the formalism and computations above:…”

Unexpected Magnetic Properties of Gas-Stabilized Platinum Nanostructures in the Tunneling Regime

“…In fact, fractional conduction peaks have been found in Pt and Au wires contaminated by molecules. 7,8 Shot noise measurements in pure Pt atomic chains have given evidence for a non-magnetic ground state, but this discrepancy with the theory could be due to spin polarized electrons that do not contribute to the transport. 9 Molecular structures can show large magnetoresistance (MR) and quantum interference, [10][11][12] and a positive MR has been observed at low temperatures in Pd atomic structures.…”