Bottom-up-synthesized graphene nanoribbons (GNRs) with excellent electronic properties are promising materials for energy storage systems. Herein, we report bottom-up-synthesized GNR films employed as electrode materials for micro-supercapacitors (MSCs). The micro-device delivers an excellent volumetric capacitance and an ultra-high power density. The electrochemical performance of MSCs could be correlated with the charge carrier mobility within the differently employed GNRs, as determined by pump–probe terahertz spectroscopy studies.

The vast potential of organic materials for electronic, optoelectronic and spintronic devices entails substantial interest in the fabrication of π-conjugated systems with tailored functionality directly at insulating interfaces. On-surface fabrication of such materials on nonmetal surfaces remains to be demonstrated with high yield and selectivity. Here we present the synthesis of polyaromatic chains on metallic substrates, insulating layers, and in the solid state. Scanning probe microscopy shows the formation of azaullazine repeating units on Au(111), Ag(111), and h-BN/Cu(111), stemming from intermolecular homo-coupling via cycloaddition reactions of CN-substituted polycyclic aromatic azomethine ylide (PAMY) intermediates followed by subsequent dehydrogenation. Matrix-assisted laser desorption/ ionization (MALDI) mass spectrometry demonstrates that the reaction also takes place in the solid state in the absence of any catalyst. Such intermolecular cycloaddition reactions are promising methods for direct synthesis of regioregular polyaromatic polymers on arbitrary insulating surfaces.

Graphene nanoribbons (GNRs) have demonstrated great potential for nanoscale devices owing to their excellent electrical properties. However, the application of the GNRs in large-scale devices still remains elusive mainly due to the absence of facile, nonhazardous, and nondestructive transfer methods. Here, we develop a simple acid (HF)-free transfer method for fabricating field-effect transistors (FETs) with a monolayer composed of a random network of GNRs. A polymer layer that is typically used as mechanical support for transferring GNR films is utilized as the gate dielectric. The resultant GNR-FETs exhibit excellent FET characteristics with a large on/off switching current ratio of >10 4 . The transfer process enables the demonstration of the first GNRbased nonvolatile memory. The process offers a simple route for GNRs to be utilized in various optoelectronic devices.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

What is the most significant result of this study?Through a chemical-vapor-deposition growth of high-quality graphene films directly on fused silica substrates, we eliminated a need of a sacrificial metal catalyst and achieved transfer-free integration into efficient micro-supercapacitors. How would you describe to the layperson the most significant result of this study?Graphene is a rising star material for energy-storage devices, especially for supercapacitors due to its excellent electronic properties. However, it is still challenging to achieve very good electronic properties through more scalable and economical producing methods. So far, the most promising approach for large-scale production of high-quality graphene relies on chemical vapor deposition (CVD). The CVD method involves decomposition of carbon-containing molecules like methane and acetylene at high temperatures of > 1000°C and allows for growth of graphene layer on metal surfaces, typically copper foils. However, integration of thus-grown graphene films into energy-storage devices require multiple film transfer processes, removing the metal catalyst. To this end, we have developed a metal-catalyst-free method for producing high-quality graphene films directly on insulating substrates by choosing a proper molecular precursor in the CVD growth. We have achieved transfer-free, direct integration of thus-grown gra-phene films into micro-supercapacitors and demonstrated high-volumetric capacitance. What was the inspiration for this cover design?We were inspired by the urgent desire of roll-to-roll production of graphene films through our metal-free chemical vapour deposition method, allowing for highly simplified and efficient integration into energy-storage devices. Who contributed to the idea behind the cover?Invited for this month's cover picture is the group of Prof. Dr. Klaus Müllen. The cover picture shows the direct metal-free chemical vapor deposition of graphene films on insulating substrates and their integration into high-volumetric capacitive micro-supercapacitors. Read the full text of the Article at