Dibenzo[hi,st]ovalene (DBOV)—a quasi-zero-dimensional “nanographene”—displays strong, narrow, and well-defined optical-absorption transitions at room temperature. On placing a DBOV-doped polymer film into an optical microcavity, we demonstrate strong coupling of the 0 → 0′ electronic transition to a confined cavity mode, with a coupling energy of 126 meV. Photoluminescence measurements indicate that the polariton population is distributed at energies approximately coincident with the emission of the DBOV, indicating a polariton population via an optical pumping mechanism.Keywords: Microcavity; nanographene; polaritons; strong coupling;

Edge functionalization of bottom-up synthesized graphene nanoribbons (GNRs) with anthraquinone and naphthalene/perylene monoimide units has been achieved through a Suzuki coupling of polyphenylene precursors bearing bromo groups, prior to the intramolecular oxidative cyclo-dehydrogenation. High efficiency of the substitution has been validated by MALDI-TOF MS analysis of the functionalized precursors and FT-IR, Raman, and XPS analyses of the resulting GNRs. Moreover, AFM measurements demonstrated the modulation of the self-assembling behavior of the edge-functionalized GNRs, revealing that GNR-PMI formed an intriguing rectangular network. This result suggests the possibility of programming the supramolecular architecture of GNRs by tuning the functional units.

Recent advances in bottom-up synthesis of atomically defined graphene nanoribbons (GNRs) with various microstructures and properties have demonstrated their promise in electronic and optoelectronic devices. Here we synthesized N = 9 armchair graphene nanoribbons (9-AGNRs) with a low optical band gap of ∼1.0 eV and extended absorption into the infrared range by an efficient chemical vapor deposition process. Time-resolved terahertz spectroscopy was employed to characterize the photoconductivity in 9-AGNRs and revealed their high intrinsic charge-carrier mobility of approximately 350 cm2·V–1·s–1.

Bottom-up synthesis of low-bandgap graphene nanoribbons with various widths is of great importance for their applications in electronic and optoelectronic devices. Here we demonstrate a synthesis of N = 5 armchair graphene nanoribbons (5-AGNRs) and their lateral fusion into wider AGNRs, by a chemical vapor deposition method. The efficient formation of 10- and 15-AGNRs is revealed by a combination of different spectroscopic methods, including Raman and UV–vis-near-infrared spectroscopy as well as by scanning tunneling microscopy. The degree of fusion and thus the optical and electronic properties of the resulting GNRs can be controlled by the annealing temperature, providing GNR films with optical absorptions up to ∼2250 nm.

We report on the surface-assisted synthesis and spectroscopic characterization of the hitherto longest periacene analogue with oxygen–boron–oxygen (OBO) segments along the zigzag edges, that is, a heteroatom-doped perihexacene 1. Surface-catalyzed cyclodehydrogenation successfully transformed the double helicene precursor 2, i.e., 12a,26a-dibora-12,13,26,27-tetraoxa-benzo[1,2,3-hi:4,5,6-h′i′]dihexacene, into the planar perihexacene analogue 1, which was visualized by scanning tunneling microscopy and noncontact atomic force microscopy. X-ray photoelectron spectroscopy, Raman spectroscopy, together with theoretical modeling, on both precursor 2 and product 1, provided further insights into the cyclodehydrogenation process. Moreover, the nonplanar precursor 2 underwent a conformational change upon adsorption on surfaces, and one-dimensional self-assembled superstructures were observed for both 2 and 1 due to the presence of OBO units along the zigzag edges.

AbstractA large number of graphene molecules, or large polycyclic aromatic hydrocarbons (PAHs), have been synthesized and display various optoelectronic properties. Nevertheless, their potential for application in photonics has remained largely unexplored. Herein, we describe the synthesis of a highly luminescent and stable graphene molecule, namely a substituted dibenzo[hi,st]ovalene (DBO 1), with zigzag edges and elucidate its promising optical-gain properties by means of ultrafast transient absorption spectroscopy. Upon incorporation of DBO into an inert polystyrene matrix, amplified stimulated emission can be observed with a relatively low power threshold (ca. 60 μJ cm−2), thus highlighting its high potential for lasing applications.

AbstractA large number of graphene molecules, or large polycyclic aromatic hydrocarbons (PAHs), have been synthesized and display various optoelectronic properties. Nevertheless, their potential for application in photonics has remained largely unexplored. Herein, we describe the synthesis of a highly luminescent and stable graphene molecule, namely a substituted dibenzo[hi,st]ovalene (DBO 1), with zigzag edges and elucidate its promising optical-gain properties by means of ultrafast transient absorption spectroscopy. Upon incorporation of DBO into an inert polystyrene matrix, amplified stimulated emission can be observed with a relatively low power threshold (ca. 60 μJ cm−2), thus highlighting its high potential for lasing applications.

The synthesis of 11a,25a-dibora-11,12,25,26-tetraoxatetranaphtho[1,2-a:2′,1′-f:1″,2″-j:2‴,1‴-o]perylene, a double [7]heterohelicene containing OBO units, has been achieved via tandem demethylation-borylation, representing the highest double helicene reported thus far with all six-membered rings. Single-crystal X-ray analysis clearly demonstrated a significantly twisted structure with the terminal aromatic rings overlapping at both ends, giving the first example of a double helicene with intramolecular π-layers. Such structural features resulted in a high theoretical isomerization barrier of 45.1 kcal/mol, which is the highest value for all the double helicenes ever reported, rendering the achieved molecule with high chiral stability. The (P,P)- and (M,M)-isomers were separated by chiral HPLC and the chiroptical properties were investigated, revealing opposite circular dichroism responses.