Electrolyte gate dependent high-frequency measurement of graphene field-effect transistor for sensing applications

We performed radiofrequency (RF) reflectometry measurements at 2.4 GHz on electrolyte-gated graphene field-effect transistors (GFETs) utilizing a tunable stub-matching circuit for impedance matching. We demonstrate that the gate voltage dependent RF resistivity of graphene can be deduced even in the presence of the electrolyte which is in direct contact with the graphene layer. The RF resistivity is found to be consistent with its DC counterpart in the full gate voltage range. Furthermore, in order to access the potential of high-frequency sensing for applications, we demonstrate time-dependent gating in solution with nanosecond time resolution.Comment: 14 pages, 4 figure

Intelligent Approach of Event Detection with Efficient Energy Consumption in Wireless Sensor Networks

In the context of environmental protection against fire, this work presents a hybrid system of decision making and early warning applied in wireless sensor networks. This system, also, integrates an efficient data routing technique, based on the clustering of the near-event nodes, ensuring judicious network energy consumption. Data fusion technique, based on sensors data aggregated by the Cluster Head node (CH) within a defined analysis area, is processed by K-medoids, the latter will mainly contribute to increase the system's performances by decreasing the intra-cluster noise parameter () conducting to improve the probability of detection. This step, therefore, will distinguish and merge only the correct and useful samples. On the basis of the fused data, the estimated alert by K-Nearest Neighbours (KNN) can be directly triggered based on a minimum number of sensor nodes detecting fire; this will affect in advantage on the rapidity of detection, which leads to limit the spread of fire quickly. The alert is transmitted from the CH node to the base station via an intermediate node (IN) elected intelligently outside the cluster. This proposed approach proves, through its simulation results, a remarkable improvement of system performances in terms of information reliability, rapidity of detection and alert, avoiding false and redundant information, and also it improves extending the network lifetime

Unravelling the conductance path through single-porphyrin junctions

Porphyrin derivatives are key components in natural machinery enabling us to store sunlight as chemical energy. In spite of their prominent role in cascades separating electrical charges and their potential as sensitizers in molecular devices, reports concerning their electronic transport characteristics are inconsistent. Here we report a systematic investigation of electronic transport paths through single porphyrin junctions. The transport through seven structurally related porphyrin derivatives was repeatedly measured in an automatized mechanically controlled break-junction set-up and the recorded data were analyzed by an unsupervised clustering algorithm. The correlation between the appearances of similar clusters in particular sub-sets of the porphyrins with a common structural motif allowed us to assign the corresponding current path. The small series of model porphyrins allowed us to identify and distinguish three different electronic paths covering more than four orders of magnitude in conductance

Doctor YouTube’s Opinion on Seasonal Influenza: A Critical Appraisal of the Information Available to Patients

Background: Seasonal influenza is a respiratory illness caused by the influenza virus. During the 2017–2018 flu season, the Centers for Disease Control and Prevention noted approximately 959,000 hospitalizations and 79,400 deaths from influenza. We sought to evaluate the educational quality of informational videos pertaining to seasonal influenza on the popular social media forum, YouTube. Methods: Using the keywords “seasonal influenza,” all videos from 28 January to 5 February 2017 were included and analyzed for characteristics, source, and content. The source was further classified as healthcare provider, alternative-medicine provider, the patient and/or their parents, company, media, or professional society. Videos about other categories of influenza (e.g. swine or Spanish) or in foreign languages were excluded. A total of 10 blinded reviewers scored each video independently. Results: Overall, 300 videos were analyzed, with a median of 341.50 views, 1.00 likes, 0 dislikes, and 0 comments. Based on the average scores of videos by source, there was statistically significant difference in the average score among videos by video source (p \u3c 0.01). Healthcare provider videos had the highest mean scores whereas alternative medicine provider videos had the lowest. Conclusions: Although the aforementioned video sources scored higher than others, these videos did not fulfill our criteria as far as educating patients thoroughly. Our data also suggest alternative medicine and patient source videos were misleading for patients. Clinical implications: Although videos by healthcare providers were a better source of information, videos on seasonal influenza were shown to be poor sources of valid healthcare information. This study reiterates the need for higher-quality educational videos on seasonal influenza by the medical community

Robust graphene-based molecular devices

One of the main challenges to upscale the fabrication of molecular devices is to achieve a mechanically stable device with reproducible and controllable electronic features that operates at room temperature1,2. This is crucial because structural and electronic fluctuations can lead to significant changes in the transport characteristics at the electrode-molecule interface3,4. In this study, we report on the realization of a mechanically and electronically robust graphene-based molecular junction. Robustness was achieved by separating the requirements for mechanical and electronic stability at the molecular level. Mechanical stability was obtained by anchoring molecules directly to the substrate, rather than to graphene electrodes, using a silanization reaction. Electronic stability was achieved by adjusting the π-π orbitals overlap of the conjugated head groups between neighbouring molecules. The molecular devices exhibited stable current-voltage (I-V) characteristics up to bias voltages of 2.0 V with reproducible transport features in the temperature range from 20 to 300 K

Understanding resonant charge transport through weakly coupled single-molecule junctions

Off-resonant charge transport through molecular junctions has been extensively studied since the advent of single-molecule electronics and it is now well understood within the framework of the non-interacting Landauer approach. Conversely, gaining a qualitative and quantitative understanding of the resonant transport regime has proven more elusive. Here, we study resonant charge transport through graphene-based zinc-porphyrin junctions. We experimentally demonstrate an inadequacy of the non-interacting Landauer theory as well as the conventional single-mode Franck-Condon model. Instead, we model the overall charge transport as a sequence of non-adiabatic electron transfers, the rates of which depend on both outer and inner-sphere vibrational interactions. We show that the transport properties of our molecular junctions are determined by a combination of electron-electron and electron-vibrational coupling, and are sensitive to the interactions with the wider local environment. Furthermore, we assess the importance of nuclear tunnelling and examine the suitability of semi-classical Marcus theory as a description of charge transport in molecular devices.Comment: version accepted in Nature Communications; SI available at https://researchportal.hw.ac.uk/en/publications/understanding-resonant-charge-transport-through-weakly-coupled-s

Understanding resonant charge transport through weakly coupled single-molecule junctions

Off-resonant charge transport through molecular junctions has been extensively studied since the advent of single-molecule electronics and it is now well understood within the framework of the non-interacting Landauer approach. Conversely, gaining a qualitative and quantitative understanding of the resonant transport regime has proven more elusive. Here, we study resonant charge transport through graphene-based zinc-porphyrin junctions. We experimentally demonstrate an inadequacy of the non-interacting Landauer theory as well as the conventional single-mode Franck-Condon model. Instead, we model the overall charge transport as a sequence of non-adiabatic electron transfers, the rates of which depend on both outer and inner-sphere vibrational interactions. We show that the transport properties of our molecular junctions are determined by a combination of electron-electron and electron-vibrational coupling, and are sensitive to the interactions with the wider local environment. Furthermore, we assess the importance of nuclear tunnelling and examine the suitability of semi-classical Marcus theory as a description of charge transport in molecular devices.Comment: version accepted in Nature Communications; SI available at https://researchportal.hw.ac.uk/en/publications/understanding-resonant-charge-transport-through-weakly-coupled-s