Impact of the terminal end-group on the electrical conductance in alkane linear chains.

This research presents comprehensive theoretical investigations of a series of alkane-based chains using four different terminal end groups including amine -NH2, thiomethyl -SMe, thiol -SH and direct carbon contact -C. It is widely known that the electrical conductance of single molecules can be tuned and boosted by chemically varying their terminal groups to metal electrodes. Here, we demonstrate how different terminal groups affect alkane molecules' electrical conductance. In general, alkane chain conductance decreases exponentially with length, regardless of the anchor group types. In these simulations the molecular length varies from 3 to 8 -CH2 units, with 4 different linker groups; these simulations suggest that the conductances follow the order G C > G SH > G SMe > G NH2 . The DFT prediction order of the 4 anchors is well supported by STM measurements. This work demonstrates an excellent correlation between our simulations and experimental measurements, namely: the percent difference ΔG, exponential decay slopes, A constants and ß factors at different molecular alkane chain lengths.

Optimised power harvesting by controlling the pressure applied to molecular junctions.

A major potential advantage of creating thermoelectric devices using self-assembled molecular layers is their mechanical flexibility. Previous reports have discussed the advantage of this flexibility from the perspective of facile skin attachment and the ability to avoid mechanical deformation. In this work, we demonstrate that the thermoelectric properties of such molecular devices can be controlled by taking advantage of their mechanical flexibility. The thermoelectric properties of self-assembled monolayers (SAMs) fabricated from thiol terminated molecules were measured with a modified AFM system, and the conformation of the SAMs was controlled by regulating the loading force between the organic thin film and the probe, which changes the tilt angle at the metal-molecule interface. We tracked the thermopower shift vs. the tilt angle of the SAM and showed that changes in both the electrical conductivity and Seebeck coefficient combine to optimize the power factor at a specific angle. This optimization of thermoelectric performance via applied pressure is confirmed through the use of theoretical calculations and is expected to be a general method for optimising the power factor of SAMs.

Correction: Molecular-scale thermoelectricity: as simple as 'ABC'.

[This corrects the article DOI: 10.1039/D0NA00772B.].

Molecular-scale thermoelectricity: as simple as 'ABC'.

If the Seebeck coefficient of single molecules or self-assembled monolayers (SAMs) could be predicted from measurements of their conductance-voltage (G-V) characteristics alone, then the experimentally more difficult task of creating a set-up to measure their thermoelectric properties could be avoided. This article highlights a novel strategy for predicting an upper bound to the Seebeck coefficient of single molecules or SAMs, from measurements of their G-V characteristics. The theory begins by making a fit to measured G-V curves using three fitting parameters, denoted a, b, c. This 'ABC' theory then predicts a maximum value for the magnitude of the corresponding Seebeck coefficient. This is a useful material parameter, because if the predicted upper bound is large, then the material would warrant further investigation using a full Seebeck-measurement setup. On the other hand, if the upper bound is small, then the material would not be promising and this much more technically demanding set of measurements would be avoided. Histograms of predicted Seebeck coefficients are compared with histograms of measured Seebeck coefficients for six different SAMs, formed from anthracene-based molecules with different anchor groups and are shown to be in excellent agreement.

A study on intrabody communication for personal healthcare monitoring system.

In this paper we propose the use of intrabody communication (IBC) for a personal health monitoring system employing inexpensive, lightweight, miniature sensor platforms. Body area networks (BANs) with physiological sensors could improve current healthcare services and at the same time significantly reduce costs to public health systems. We are primarily looking to reduce the transmission power consumption of the wireless communication links by using very low power IBC to connect the BAN sensors, a change that has also been shown to increase the durability of the sensors. There has been no specific study carried out to date on the optimal modulation scheme for such IBC. For this reason, we investigated the transmission characteristics of the human body as a conductor of signal up to 2.4 GHz by considering different transmitter power consumption and data transmission rates. We believe that an optimal modulation scheme for IBC would allow an increase of the data transmission bit rate in our personal health monitoring system model. Therefore, we evaluated the performance of two different modulation schemes, QPSK and BPSK. Our experiment is conducted with point-to-point communication between an electrocardiogram sensor located in the chest region and a central hub located on the left wrist.