Investigation of Amperometric Sensing Mechanism in Gold–C₆₀–Gold Molecular Dot

Abstract

We investigate through simulations the gold-C 60 -gold molecular junction as a novel single-molecule amperometric gas sensor. We find it promising for NO and NO 2 detection in air and at room temperature, with current variations of the order of the microampere, and presenting the potential capability of achieving the single-molecule sensitivity along with selectivity in the presence of common atmospheric gases. Furthermore, and for the first time, we investigate the current modulation mechanism due to target-sensor intermolecular interactions, providing theoretical insights into the functioning and exclusive properties of this novel device. In particular, we show and motivate the peculiar voltage-dependent response of the sensor that we relate to the distinctive mechanism of transport modulation occurring in the presence of a specific target. Finally, we discuss sensing reliability in air and the effects of probable fabrication process variability on sensing performance. Our results motivate future works on molecular dot-based chemical sensors in terms of the sensor-target exclusive interactions and detection principles, oriented to device-level engineering to find optimal operating conditions. Index Terms-Amperometric detection, C 4 H 10 , C 60 , CH 4 , CO, CO 2 , dot, electronics, fullerene, gas, gold, junction, molecular, nanogap, NH 3 , nitric oxide (NO), NO 2 , quantum, sensor, single-molecule. I. INTRODUCTIONA IR pollution is gaining global attention as a cause of climate change and a risk to human health by provoking severe diseases [1], [2]. The current state-of-the-art gas measurement trend is toward nanostructured metal oxide (MOX) chemiresistive sensors, thanks to their high sensitivity, fast response/recovery time, high stability and crystallinity, direct electronic interface, and low fabrication cost [3], [4]. Among them, miniaturized sensors, like nanowires, are promising Manuscript

Effect of Adsorption Mechanism on Conduction in Single-Molecule Pyrrole-Based Sensor for AFB1

“…A current reduction of almost two orders of magnitude, from 0.462 µA to 6.56 nA, is present in the optimum sensing condition, corresponding to AC1 configuration at 0.6 V. Interestingly, the transport modulation seems independent on the nature of the AFB1-8PyDT chemical interaction, while we believe it is caused by an 8PyDT torsion, that breaks the 8PyDT conjugation and affects the molecular channel conformation and orbitals, with spatial TEs and TPs modulation. Despite the very different sensor structure, this is coherent with the results we obtained in a previous work [36]. Thanks to the effective I DS reduction of hundreds of nA in all the AC1, AC2, AC3, AC4 cases, the proposed SMS is promising for chemically robust, labelfree, pervasive detection of AFB1 concentration in food stocks and on field.…”

Design of Pyrrole-Based Gate-Controlled Molecular Junctions Optimized for Single-Molecule Aflatoxin B1 Detection

“…In a previous work [ 25 ], we have shown that chemical analytes can significantly modify the SMS transmission spectrum, , and thus the SMS current, , through a spatial modification of the region in which transmission occurs, i.e., by modifying the contributing to conduction. In [ 25 ], we related the modification to an electron wavefunction spatial displacement caused by the presence of the analyte.…”

“…In a previous work [ 25 ], we have shown that chemical analytes can significantly modify the SMS transmission spectrum, , and thus the SMS current, , through a spatial modification of the region in which transmission occurs, i.e., by modifying the contributing to conduction. In [ 25 ], we related the modification to an electron wavefunction spatial displacement caused by the presence of the analyte. In other words, the target analyte can significantly affect the electron wavefunction in the SMS by modifying the transmission properties , and , and therefore the current, , which can be evaluated through Equations ( 1 ) and ( 3 ).…”

“…Scanning Tunneling Break Junction (STM-BJ) techniques and Mechanical Break Junction (MBJ) platforms allow the experimental verification of single molecule devices such as switches, photoswitches, diodes, memristors and sensors [ 18 , 19 , 20 , 21 , 22 ]. Molecular electrical detection has been demonstrated in various applications experimentally and theoretically [ 22 , 23 , 24 , 25 , 26 ], and significantly novel properties have been highlighted by the use of molecules in the realization of sensors [ 25 ]. In addition, possible nanoscale phenomena with exclusive conductive properties, e.g., the quantum interference [ 27 , 28 , 29 ], and successful applications in high-sensitivity sensors make it very promising for the detection of small molecules.…”