A computational study of a single molecule chemical sensor
File(s)
Author(s)
Li, Mengxuan
Type
Thesis
Abstract
An electronic nose is a portable device capable of detecting gases and recognizing odors. One of the problems limiting its widespread application is the insufficient selectivity of the device. In this study we propose a new type of electronic nose which can potentially be small, fast and cheap compared with traditional gas analysis tools like IR and Raman spectroscopies.
This device is composed of a molecular junction exhibiting a sharp Negative Differential Resistance (NDR) current peak which could potentially enhance the selectivity, thereby functioning as a molecular sensor for molecule recognition. Using DFT-NEGF simulations, we investigate the relationship between molecule-molecule coupling, molecule-electrode coupling, and the corresponding NDR peak shape. Based on this analysis, we put forward three design rules to control the sensitivity of a sensor and determine that one mechanism for NDR is when a localized molecular orbital involved in resonant tunneling enters and leaves the bias window.
After the inelastic interaction of electrons with phonons is included in the calculations, we modified the structure of the molecular junction so that the electrons are forced to travel through the odorant. With this modification, we successfully detected various molecules using the molecular sensor based on Inelastic Electron Tunneling Spectroscopy (IETS).
Our findings provide valuable insights that could aid in the development of single-molecule sensors for molecule recognition and also contribute to the understanding of inelastic tunneling behaviour of electrons.
This device is composed of a molecular junction exhibiting a sharp Negative Differential Resistance (NDR) current peak which could potentially enhance the selectivity, thereby functioning as a molecular sensor for molecule recognition. Using DFT-NEGF simulations, we investigate the relationship between molecule-molecule coupling, molecule-electrode coupling, and the corresponding NDR peak shape. Based on this analysis, we put forward three design rules to control the sensitivity of a sensor and determine that one mechanism for NDR is when a localized molecular orbital involved in resonant tunneling enters and leaves the bias window.
After the inelastic interaction of electrons with phonons is included in the calculations, we modified the structure of the molecular junction so that the electrons are forced to travel through the odorant. With this modification, we successfully detected various molecules using the molecular sensor based on Inelastic Electron Tunneling Spectroscopy (IETS).
Our findings provide valuable insights that could aid in the development of single-molecule sensors for molecule recognition and also contribute to the understanding of inelastic tunneling behaviour of electrons.
Version
Open Access
Date Issued
2024-08-13
Date Awarded
01/03/2025
Advisor
Cucinotta, Clotilde
Horsfield, Andrew
Publisher Department
Department of Materials
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)