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A single nanoparticle is one of the most sensitive electronic devices for sensing chemicals in a gas or liquid. The conductivity of a single Au nanoparticle is significantly modulated by the binding of a molecule that alters charge by just one electron. However, the single-electron sensitivity requires cryogenic temperatures and interconnection is not easy. A patterned two-dimensional network of one-dimensional nanoparticle necklaces made up of 10 nm Au particles are fabricated and shown to exhibit similar single-electron effect at room temperature. Furthermore, the long range conductivity of over 10’s of microns makes the structure easy to self-assemble onto conventional microelectronics circuitry. A device exhibiting single-electron effect is characterized by highly non-linear current-bias behavior where at bias, V > VT current rises rapidly and scales as (V/VT – 1)ζ, where ζ ≥ 1 is the critical exponent and VT is the threshold voltage. Below VT, current does not flow. Thus, VT is the switching voltage and larger ζ signifies sharper switching characteristics. While arrays of one and two dimension are well known to exhibit appreciable VT at cryogenic temperatures, at ambient temperatures the blockade effect vanishes. The unique architecture of the necklace network results in a weak dependence of VT on temperature which leads to room temperature single-electron effect. The high sensitivity of the nanoparticle necklace network array at room temperature allows coupled live cells to electronically switch, or gate, the device through cellular metabolic activity. Additionally, the critical exponent, ζ, which is a measure of how current will rise during switching, can be significantly enhanced by cementing the necklaces with the dielectric material CdS, thereby greatly increasing the switching gain and sensitivity of the device. Given robust room temperature single-electron switching, enhanced ζ values, cellular coupling capability, and natural integrability with microelectronics circuitry, nanoparticle necklace network arrays have the potential to be implemented in a wide range of applications, such as, chemical sensors, biofuel cells, biomedical devices, and data storage devices.
Adviser: Ravi F. Saraf