Real-space mapping of tailored sheet and edge plasmons in graphene nanoresonators

Plasmons in graphene nanoresonators have many potential applications in photonics and optoelectronics, including room-temperature infrared and terahertz photodetectors, sensors, reflect arrays or modulators1, 2, 3, 4, 5, 6, 7. The development of efficient devices will critically depend on precise knowledge and control of the plasmonic modes. Here, we use near-field microscopy8, 9, 10, 11 between λ0 = 10–12 μm to excite and image plasmons in tailored disk and rectangular graphene nanoresonators, and observe a rich variety of coexisting Fabry–Perot modes. Disentangling them by a theoretical analysis allows the identification of sheet and edge plasmons, the latter exhibiting mode volumes as small as 10−8λ03. By measuring the dispersion of the edge plasmons we corroborate their superior confinement compared with sheet plasmons, which among others could be applied for efficient 1D coupling of quantum emitters12. Our understanding of graphene plasmon images is a key to unprecedented in-depth analysis and verification of plasmonic functionalities in future flatland technologies.Peer ReviewedPostprint (author's final draft

Hypophosphatasia

Hypophosphatasia is a rare inherited disorder characterized by defective bone and teeth mineralization, and deficiency of serum and bone alkaline phosphatase activity. The prevalence of severe forms of the disease has been estimated at 1/100 000

Mass spectrometry of carbohydrate-protein interactions on a glycan array conjugated to CVD graphene surfaces

Mass spectrometry (MS) is a valuable tool for functional genomic, proteomic, and glycomic studies. In particular, the combination of MS with microarrays is a powerful technique for analyzing the activity of carbohydrate processing enzymes and for the identification of carbohydrate-binding proteins (lectins) in complex matrices. On the other hand, graphene exhibits high desorption/ionization efficiency, good conductivity and optical transparency, specifications of a high-performance component for matrix-assisted laser desorption/ionization (MALDI) platforms. Besides, the chemical functionalization of graphene increases the adsorption capability of functional biomolecules (e.g. receptors), resulting in very stable interfaces. Taking advantage of the properties of graphene, we developed several modified chemical vapor deposited graphene (CVDG)-based glycan arrays on different substrates including ITO and bare glass, as a potential sensing platform for carbohydrate-lectin interactions, which are involved in a plethora of biological processes. The glycan arrays were fully characterized by MALDI-MS analysis and, in some cases, optical microscopy

Investigation of CVD graphene topography and surface electrical properties

Combining scanning probe microscopy techniques to characterise samples of graphene, a self-supporting single atomic layer hexagonal lattice of carbon atoms, provides far more information than a single technique can. Here we focus on graphene grown by chemical vapour deposition (CVD), grown by passing carbon containing gas over heated copper, which catalyses single atomic layer growth of graphene on its surface. To be useful for applications the graphene must be transferred onto other substrates. Following transfer it is important to characterise the CVD graphene. We combine atomic force microscopy (AFM) and scanning Kelvin probe microscopy (SKPM) to reveal several properties of the transferred film. AFM alone provides topographic information, showing ‘wrinkles’ where the transfer provided incomplete substrate attachment. Combined with SKPM which measures the surface potential (SP), indicating regions with different graphene layer numbers, local defects and impurities can also be observed in the SP scan. Finally, Raman spectroscopy can confirm the structural properties of the graphene films, such as the number of layers and level of disorder, by observing the peaks present. We report example data on a number of CVD samples from different sources

Facebook affordances and citizen engagement during elections: European political parties and their benefit from online strategies?

This paper examines how Facebook is used by political parties during elections to extend or accelerate their reach within the electorate and how successful these efforts are. Specifically, we compare the content and style of parties’ Facebook posts during the 2014 European parliament elections, and how this affects followers’ responses in terms of liking, sharing and commenting on the posts. Our findings reveal while that the timing and visual content of posts are important in increasing voters’ attention, interactivity matters most. Responsive party posts on Facebooks are significantly more likely to be shared, liked, and commented on by users. Given that follower reactions, particularly sharing, helps to increase the visibility of party communication through indirect or two-step flow communication (online and offline), these findings are important in advancing our understanding of how and why social media campaigns are able to influence voters and thus affect election outcomes. For parties themselves the results provide some useful insights into what makes for an ‘effective’ Facebook campaign in terms of how they can accelerate the reach of their communication

Ultrasensitive detection of SARS-CoV-2 spike protein by graphene field-effect transistors

COVID-19, caused by the severe acute respiratory syndrome-coronavirus 2 (SARS-CoV-2), originated a global health crisis, causing over 2 million casualties and altering human daily life all over the world. This pandemic emergency revealed the limitations of current diagnostic tests, highlighting the urgency to develop faster, more precise and sensitive sensors. Graphene field effect transistors (GFET) are analytical platforms that enclose all these requirements. However, the design of a sensitive and robust GFET is not a straightforward objective. In this work, we report a GFET array biosensor for the detection of SARS-CoV-2 spike protein using the human membrane protein involved in the virus internalisation: angiotensin-converting enzyme 2 (ACE2). By finely controlling the graphene functionalisation, by tuning the Debye length, and by deeply characterising the ACE2-spike protein interactions, we have been able to detect the target protein with an extremely low limit of detection (2.94 aM). This work set the basis for a new class of analytical platforms, based on human membrane proteins, with the potential to detect a broad variety of pathogens, even before their isolation, being a powerful tool in the fight against future pandemics