Electrical and optical properties of porphyrin monomer and its J-aggregate

We have investigated the electrical and optical properties of a water-soluble porphyrin monomer and its J-aggregate both in solution and in the solid state. Specifically, we find that water enhances the electrical conductivity, of both the monomer and the J-aggregate. The luminescence quantum efficiency and spectrum are also affected quite dramatically by the presence of water. The J-aggregate also shows an electrochromic effect in the presence of moisture. We show that the electrochromic effect arises because the J-aggregate converts to the monomer

Surface functionalization of epitaxial graphene on SiC by ion irradiation for gas sensing application

In this work, surface functionalization of epitaxial graphene grown on silicon carbide was performed by ion irradiation to investigate their gas sensing capabilities. Swift heavy ion irradiation using 100 MeV silver ions at four varying fluences was implemented on epitaxial graphene to investigate morphological and structural changes and their effects on the gas sensing capabilities of graphene. Sensing devices are expected as one of the first electronic applications using graphene and most of them use functionalized surfaces to tailor a certain function. In our case, we have studied irradiation as a tool to achieve functionalization. Morphological and structural changes on epitaxial graphene layers were investigated by atomic force microscopy, Raman spectroscopy, Raman mapping and reflectance mapping. The surface morphology of irradiated graphene layers showed graphene folding, hillocks, and formation of wrinkles at highest fluence (2 x 10(13) ions/cm(2)). Raman spectra analysis shows that the graphene defect density is increased with increasing fluence, while Raman mapping and reflectance mapping show that there is also a reduction of monolayer graphene coverage. The samples were investigated for ammonia and nitrogen dioxide gas sensing applications. Sensors fabricated on pristine and irradiated samples showed highest gas sensing response at an optimal fluence. Our work provides new pathways for introducing defects in controlled manner in epitaxial graphene, which can be used not only for gas sensing application but also for other applications, such as electrochemical, biosensing, magnetosensing and spintronic applications. (C) 2017 Elsevier B.V. All rights reserved.Funding Agencies|Graphene Flagship [CNECT-ICT-604391]; Swedish Research Council [2015-05876]</p