Retained Carrier-Mobility and Enhanced Plasmonic-Photovoltaics of Graphene via ring-centered η⁶ Functionalization and Nanointerfacing

Abstract

Binding graphene with auxiliary nanoparticles for plasmonics, photovoltaics, and/or optoelectronics, while retaining the trigonal-planar bonding of sp hybridized carbons to maintain its carrier-mobility, has remained a challenge. The conventional nanoparticle-incorporation route for graphene is to create nucleation/attachment sites via "carbon-centered" covalent functionalization, which changes the local hybridization of carbon atoms from trigonal-planar sp to tetrahedral sp. This disrupts the lattice planarity of graphene, thus dramatically deteriorating its mobility and innate superior properties. Here, we show large-area, vapor-phase, "ring-centered" hexahapto (η) functionalization of graphene to create nucleation-sites for silver nanoparticles (AgNPs) without disrupting its sp character. This is achieved by the grafting of chromium tricarbonyl [Cr(CO)] with all six carbon atoms (sigma-bonding) in the benzenoid ring on graphene to form an (η-graphene)Cr(CO) complex. This nondestructive functionalization preserves the lattice continuum with a retention in charge carrier mobility (9% increase at 10 K); with AgNPs attached on graphene/n-Si solar cells, we report an ∼11-fold plasmonic-enhancement in the power conversion efficiency (1.24%).

Gateless and reversible Carrier density tunability in epitaxial graphene devices functionalized with chromium tricarbonyl

“…Though the observed components of the functionalization process are expected and reported in the literature, their relative intensities were much higher compared to adjacent atoms like carbon. [32][33][34]36,[38][39] This observation is explained and resolved in the Supplementary Data.…”

“…The concept of functionalizing EG with Cr(CO) 3 was motivated, in part, by pursuits to alter the electronic structure of graphene without drastically modifying the in-plane transport properties, and to date, several groups use different forms of graphene to study the mechanisms behind hexahapto functionalization. [32][33][34][35][36][37] Covalent functionalization by this method does not fully passivate the EG surface, but greatly reduces the level of electron doping in EG devices and helps to limit the long-term drift in carrier density levels. For our method, which follows closely that of Ref.…”

“…The furnace temperature was then raised to 130 °C, using the optimized conditions set forth by Ref. 36. The Cr(CO) 6 sublimates and reacts with the surface of EG, resulting in the ring-centered Cr(CO) 3 functionalization.…”

Investigating photoresponsivity of graphene-silver hybrid nanomaterials in the ultraviolet

“…Various schemes to enhance the interaction of light with graphene [2][3][4][5][6] have been implemented, of which integration with plasmonic nanoparticles is particularly attractive. [7][8][9][10] The subwavelength localization and enhancement of the electric field around the nanoparticles can lead to a higher responsivity at the plasmon resonance. They also offer tunability in terms of spectral response, e.g., by changing the shape, size, and material, or polarizationresponse, e.g., by changing the aspect ratio.…”

An Interpretable Classification Framework for Information Extraction from Online Healthcare Forums

“…A more sophisticated classification framework is needed for processing unstructured data in OHFs, in order to extract useful patterns (e.g., terms, text sequences) for accurate categorization. Second, when categorizing post sentences into different classes, it is difficult to make the tradeoff between classification accuracy and interpretability [4, 5]. In health-related tasks, besides desirable classification performance, human-understandable explanations for classification results are also crucial, because patients or doctors will not take the risk to trust the predictions they do not understand.…”