From Nanographene and Graphene Nanoribbons to Graphene Sheets: Chemical Synthesis

Room-Temperature Near-Infrared Phosphorescence from C64 Nanographene Tetraimide by π-Stacking Complexation with Platinum Porphyrin

Near-Infrared (NIR) phosphorescence at room temperature is challenging to achieve for organic molecules due to negligible spin-orbit coupling and a low energy gap leading to fast non-radiative transitions. Here, we show a supramolecular host-guest strategy to harvest the energy from the low-lying triplet state of C64 nanographene tetraimide 1. 1H NMR and X-ray analysis confirmed the 1 : 2 stoichiometric binding of a Pt(II) porphyrin on the two π-surfaces of 1. While the free 1 does not show emission in the NIR, the host-guest complex solution shows NIR phosphorescence at 77 K. Further, between 860-1100 nm, room temperature NIR phosphorescence (λmax=900 nm, τavg=142 μs) was observed for a solid-state sample drop-casted from a preformed complex in solution. Theoretical calculations reveal a non-zero spin-orbit coupling between isoenergetic S1 and T3 of π-stacked [1 ⋅ Pt(II) porphyrin] complex. External heavy-atom-induced spin-orbit coupling along with rigidification and protection from oxygen in the solid-state promotes both the intersystem crossing from the first excited singlet state into the triplet manifold and the NIR phosphorescence from the lowest triplet state of 1.

A Geometrically Flexible Three-Dimensional Nanocarbon

The development of architecturally unique molecular nanocarbons by bottom-up organic synthesis is essential for accessing functional organic materials awaiting technological developments in fields such as energy, electronics, and biomedicine. Herein, we describe the design and synthesis of a triptycene-based three-dimensional (3D) nanocarbon, GFN-1, with geometrical flexibility on account of its three peripheral π-panels being capable of interconverting between two curved conformations. An effective through-space electronic communication among the three π-panels of GFN-1 has been observed in its monocationic radical form, which exhibits an extensively delocalized spin density over the entire 3D π-system as revealed by electron paramagnetic resonance and UV-vis-NIR spectroscopies. The flexible 3D molecular architecture of GFN-1, along with its densely packed superstructures in the presence of fullerenes, is revealed by microcrystal electron diffraction and single-crystal X-ray diffraction, which establish the coexistence of both propeller and tweezer conformations in the solid state. GFN-1 exhibits strong binding affinities for fullerenes, leading to host-guest complexes that display rapid photoinduced electron transfer within a picosecond. The outcomes of this research could pave the way for the utilization of shape and electronically complementary nanocarbons in the construction of functional coassemblies.

Visible light-induced chemoselective 1,2-diheteroarylation of alkenes

Visible-light photocatalysis has evolved as a powerful technique to enable controllable radical reactions. Exploring unique photocatalytic mode for obtaining new chemoselectivity and product diversity is of great significance. Herein, we present a photo-induced chemoselective 1,2-diheteroarylation of unactivated alkenes utilizing halopyridines and quinolines. The ring-fused azaarenes serve as not only substrate, but also potential precursors for halogen-atom abstraction for pyridyl radical generation in this photocatalysis. As a complement to metal catalysis, this photo-induced radical process with mild and redox neutral conditions assembles two different heteroaryl groups into alkenes regioselectively and contribute to broad substrates scope. The obtained products containing aza-arene units permit various further diversifications, demonstrating the synthetic utility of this protocol. We anticipate that this protocol will trigger the further advancement of photo-induced alkyl/aryl halides activation.

[4]Rhombene: Solution-Phase Synthesis and Application in Distributed Feedback Lasers With Emission Beyond 830 nm

Graphene-like molecules with multiple zigzag edges are emerging as promising gain materials for organic lasers. Their emission wavelengths can vary widely, ranging from visible to near-infrared (NIR), as the molecular size increases. Specifically, rhombus-shaped molecular graphenes with two pairs of parallel zigzag edges, known as [n]rhombenes, are excellent candidates for NIR lasers due to their small energy gaps. However, synthesizing large-size rhombenes with emission beyond 800 nm in solution remains a significant challenge. In this study, we present a straightforward synthesis of an aryl-substituted [4]rhombene derivative, [4]RB-Ar, using a method that combines intramolecular radical-radical coupling with Bi(OTf)3-mediated cyclization of vinyl ethers. The structure of [4]RB-Ar was confirmed through X-ray crystallographic analysis. Bond length analysis and theoretical calculations indicate that aromatic sextets are predominantly localized along the molecule's long axis. Significantly, [4]RB-Ar demonstrates narrow amplified spontaneous emission at around 834 nm when dispersed in polystyrene thin films. Moreover, solution-processed distributed feedback lasers employing [4]RB-Ar as the active gain material display tunable narrow emissions in the range of 830 to 844 nm.

Graphene-Based Photodynamic Therapy and Overcoming Cancer Resistance Mechanisms: A Comprehensive Review

Photodynamic therapy (PDT) is a non-invasive therapy that has made significant progress in treating different diseases, including cancer, by utilizing new nanotechnology products such as graphene and its derivatives. Graphene-based materials have large surface area and photothermal effects thereby making them suitable candidates for PDT or photo-active drug carriers. The remarkable photophysical properties of graphene derivates facilitate the efficient generation of reactive oxygen species (ROS) upon light irradiation, which destroys cancer cells. Surface functionalization of graphene and its materials can also enhance their biocompatibility and anticancer activity. The paper delves into the distinct roles played by graphene-based materials in PDT such as photosensitizers (PS) and drug carriers while at the same time considers how these materials could be used to circumvent cancer resistance. This will provide readers with an extensive discussion of various pathways contributing to PDT inefficiency. Consequently, this comprehensive review underscores the vital roles that graphene and its derivatives may play in emerging PDT strategies for cancer treatment and other medical purposes. With a better comprehension of the current state of research and the existing challenges, the integration of graphene-based materials in PDT holds great promise for developing targeted, effective, and personalized cancer treatments.

Helical Nanographenes Bearing Pentagon-Heptagon Pairs by Stepwise Dehydrocyclization

The incorporation of pentagon-heptagon pairs into helical nanographenes lacks a facile synthetic route, and the impact of these pairs on chiroptical properties remains unclear. In this study, a method for the stepwise construction of pentagon-heptagon pairs in helical nanographenes by the dehydrogenation of [6]helicene units was developed. Three helical nanographenes containing pentagon-heptagon pairs were synthesized and characterized using this approach. A wide variation in the molecular geometries and photophysical properties of these helical nanographenes was observed, with changes in the helical length of these structures and the introduction of the pentagon-heptagon pairs. The embedded pentagon-heptagon pairs reduced the oxidation potential of the synthesized helical nanographenes. The high isomerization energy barriers enabled the chiral resolution of the helicene enantiomers. Chiroptical investigations revealed remarkably enhanced circularly polarized luminescence and luminescence dissymmetry factors with an increasing number of the pentagon-heptagon pairs.

Solid Electrolyte Interphase Recombination on Graphene Nanoribbons for Lithium Anode

The practical application of lithium metal batteries is hindered by the lithium dendrite issue, which is seriously affected by the composition and structure of the solid electrolyte interphase (SEI). Modifying the SEI can regulate lithium dendrite formation and growth. Here, we experimentally realize a Li protective layer of LiTFSI-ether electrolyte induced a natural SEI grafted on graphene nanoribbons (SEI@GNRs) via their in situ reactions. The experimental results and theoretical calculations uncover that the 3D structure of SEI@GNRs can reduce the local current density and Li+ flux. The natural SEI in SEI@GNRs, especially the rich inorganic species of LiF, Li3N, and Li2S, decreases the Li+ nucleation overpotential, makes Li+ ion deposition and nucleation uniform, and isolates electron transport. Their synergetic effect suppresses Li dendrite formation and growth, increasing the electrochemical performance of lithium metal batteries. The design strategy is beneficial for the development of lithium metal batteries.

Porous Conductive Textiles for Wearable Electronics

Over the years, researchers have made significant strides in the development of novel flexible/stretchable and conductive materials, enabling the creation of cutting-edge electronic devices for wearable applications. Among these, porous conductive textiles (PCTs) have emerged as an ideal material platform for wearable electronics, owing to their light weight, flexibility, permeability, and wearing comfort. This Review aims to present a comprehensive overview of the progress and state of the art of utilizing PCTs for the design and fabrication of a wide variety of wearable electronic devices and their integrated wearable systems. To begin with, we elucidate how PCTs revolutionize the form factors of wearable electronics. We then discuss the preparation strategies of PCTs, in terms of the raw materials, fabrication processes, and key properties. Afterward, we provide detailed illustrations of how PCTs are used as basic building blocks to design and fabricate a wide variety of intrinsically flexible or stretchable devices, including sensors, actuators, therapeutic devices, energy-harvesting and storage devices, and displays. We further describe the techniques and strategies for wearable electronic systems either by hybridizing conventional off-the-shelf rigid electronic components with PCTs or by integrating multiple fibrous devices made of PCTs. Subsequently, we highlight some important wearable application scenarios in healthcare, sports and training, converging technologies, and professional specialists. At the end of the Review, we discuss the challenges and perspectives on future research directions and give overall conclusions. As the demand for more personalized and interconnected devices continues to grow, PCT-based wearables hold immense potential to redefine the landscape of wearable technology and reshape the way we live, work, and play.

Recent Advances in Mechanistic Understanding of Metal-Free Carbon Thermocatalysis and Electrocatalysis with Model Molecules

Metal-free carbon, as the most representative heterogeneous metal-free catalysts, have received considerable interests in electro- and thermo-catalytic reactions due to their impressive performance and sustainability. Over the past decade, well-designed carbon catalysts with tunable structures and heteroatom groups coupled with various characterization techniques have proposed numerous reaction mechanisms. However, active sites, key intermediate species, precise structure-activity relationships and dynamic evolution processes of carbon catalysts are still rife with controversies due to the monotony and limitation of used experimental methods. In this Review, we summarize the extensive efforts on model catalysts since the 2000s, particularly in the past decade, to overcome the influences of material and structure limitations in metal-free carbon catalysis. Using both nanomolecule model and bulk model, the real contribution of each alien species, defect and edge configuration to a series of fundamentally important reactions, such as thermocatalytic reactions, electrocatalytic reactions, were systematically studied. Combined with in situ techniques, isotope labeling and size control, the detailed reaction mechanisms, the precise 2D structure-activity relationships and the rate-determining steps were revealed at a molecular level. Furthermore, the outlook of model carbon catalysis has also been proposed in this work.

Molecular Graphene Nanoribbon Junctions

One of the challenges for the realization of molecular electronics is the design of nanoscale molecular wires displaying long-range charge transport. Graphene nanoribbons are an attractive platform for the development of molecular wires with long-range conductance owing to their unique electrical properties. Despite their potential, the charge transport properties of single nanoribbons remain underexplored. Herein, we report a synthetic approach to prepare N-doped pyrene-pyrazinoquinoxaline molecular graphene nanoribbons terminated with diamino anchoring groups at each end. These terminal groups allow for the formation of stable molecular graphene nanoribbon junctions between two metal electrodes that were investigated by scanning tunneling microscope-based break-junction measurements. The experimental and computational results provide evidence of long-range tunneling charge transport in these systems characterized by a shallow conductance length dependence and electron tunneling through >6 nm molecular backbone.

Spatially resolved fluoroalkylation and alkylation of graphene by direct laser writing

Two classes of photoactive compounds containing fluoroalkyl- and alkyl silver carboxylates were utilized for graphene laser writing, affording a set of patterned graphene architectures bearing various functionalities. The laser patterning of graphene is accomplished by using laser-triggered decomposition of silver carboxylates to generate radicals confined to the irradiated area for the selective binding of graphene.

Cove-Edged Chiral Graphene Nanoribbons with Chirality-Dependent Bandgap and Carrier Mobility

Graphene nanoribbons (GNRs) have garnered significant interest due to their highly customizable physicochemical properties and potential utility in nanoelectronics. Besides controlling widths and edge structures, the inclusion of chirality in GNRs brings another dimension for fine-tuning their optoelectronic properties, but related studies remain elusive owing to the absence of feasible synthetic strategies. Here, we demonstrate a novel class of cove-edged chiral GNRs (CcGNRs) with a tunable chiral vector (n,m). Notably, the bandgap and effective mass of (n,2)-CcGNR show a distinct positive correlation with the increasing value of n, as indicated by theory. Within this GNR family, two representative members, namely, (4,2)-CcGNR and (6,2)-CcGNR, are successfully synthesized. Both CcGNRs exhibit prominently curved geometries arising from the incorporated [4]helicene motifs along their peripheries, as also evidenced by the single-crystal structures of the two respective model compounds (1 and 2). The chemical identities and optoelectronic properties of (4,2)- and (6,2)-CcGNRs are comprehensively investigated via a combination of IR, Raman, solid-state NMR, UV-vis, and THz spectroscopies as well as theoretical calculations. In line with theoretical expectation, the obtained (6,2)-CcGNR possesses a low optical bandgap of 1.37 eV along with charge carrier mobility of ∼8 cm2 V-1 s-1, whereas (4,2)-CcGNR exhibits a narrower bandgap of 1.26 eV with increased mobility of ∼14 cm2 V-1 s-1. This work opens up a new avenue to precisely engineer the bandgap and carrier mobility of GNRs by manipulating their chiral vector.

Supramolecular Large Nanosheets Assembled at Air/Water Interfaces and in Solution from Amphiphilic Heptagon-Containing Nanographenes

We report the synthesis of a new set of amphiphilic saddle-shaped heptagon-containing polycyclic aromatic hydrocarbons (PAHs) functionalized with tetraethylene glycol chains and their self-assembly into large two-dimensional (2D) polymers. An in-depth analysis of the self-assembly mechanism at the air/water interface has been carried out, and the proposed arrangement models are in good agreement with the molecular dynamics simulations. Quite remarkably, the number and disposition of the tetraethylene glycol chains significantly influence the disposition of the PAHs at the interface and conditionate their packing under pressure. For the three compounds studied, we observed three different behaviors in which the aromatic core is parallel, perpendicular, and tilted with respect to the water surface. We also show that these curved PAHs are able to self-assemble in solution into remarkably large sheets of up to 150 μm2. These results show the relationship, within a family of curved nanographenes, between the monomer configuration and their self-assembly capacity in air/water interfaces and organic-water mixtures.

Energy Application of Graphene Based Membrane: Hydrogen Separation

Hydrogen gas (H2 ) is a viable energy carrier that has the potential to replace the traditional fossil fuels and contribute to achieving zero net emissions, making it an attractive option for a hydrogen-based society. However, current H2 purification technologies are often limited by high energy consumption, and as a result, there is a growing demand for alternative techniques that offer higher H2 purity and energy efficiency. Membrane separation has emerged as a promising approach for obtaining high-purity H2 gas with low energy consumption. Nevertheless, despite years of development, commercial polymeric membranes have limited performance, prompting researchers to explore alternative materials. In this context, carbon-based membranes, specifically graphene-based nanomaterials, have gained significant attention as potential membrane materials due to their unique properties. In this review, we provide a comprehensive overview of carbon-based membranes for H2 gas separation, fabrication of the membrane, and its characterization, including their advantages and limitations. We also explore the current technological challenges and suggest insights into future research directions, highlighting potential ways to improve graphene-based membranes performance for H2 separations.

On-Surface Synthesis of Multiple Cu Atom-Bridged Organometallic Oligomers

A metal-metal bond between coordination complexes has the nature of a covalent bond in hydrocarbons. While bimetallic and trimetallic compounds usually have three-dimensional structures in solution, the high directionality and robustness of the bond can be applied for on-surface syntheses. Here, we present a systematic formation of complex organometallic oligomers on Cu(111) through sequential ring opening of 11,11,12,12-tetraphenyl-1,4,5,8-tetraazaanthraquinodimethane and bonding of phenanthroline derivatives by multiple Cu atoms. A detailed characterization with a combination of scanning tunneling microscopy and density functional theory calculations revealed the role of the Cu adatoms in both enantiomers of the chiral oligomers. Furthermore, we found sufficient strength of the bonds against sliding friction by manipulating the oligomers up to a hexamer. This finding may help to increase the variety of organometallic nanostructures on surfaces.

Annulative π-Extension by Cp*Co(III)-Catalyzed Ketone-Directed peri-Annulation: An Approach to Access Fused Arenes

A masked-bay-region selective first-row transition-metal Cp*Co(III)-catalyzed annulative π-extension of arene-derived ketones is achieved to afford K-region-functionalized benzo[e]pyrenes, benzotetraphenes, and pyrenes. Comprehensive density functional theory studies buttress the mechanistic pathway comprising key steps like peri-C-H activation, alkyne 1,2-migratory insertion, and nucleophilic attack toward ketone, this attack being the rate-determining step. In addition, π-conjugated 1,1'-bipyrenes, potential photocatalyst pyrene-quinones, and putative n-type semiconductor cyano group-containing dibenzo[de,qr]tetracenes are also accessed.

Photoredox Annulation of Polycyclic Aromatic Hydrocarbons

The rise of interest in using polycyclic aromatic hydrocarbons (PAHs) and molecular graphenoids in optoelectronics has recently stimulated the growth of modern synthetic methodologies giving access to intramolecular aryl-aryl couplings. Here, we show that a radical-based annulation protocol allows expansion of the planarization approaches to prepare functionalized molecular graphenoids. The enabler of this reaction is peri-xanthenoxanthene, the photocatalyst which undergoes photoinduced single electron transfer with an ortho-oligoarylenyl precursor bearing electron-withdrawing and nucleofuge groups. Dissociative electron transfer enables the formation of persistent aryl radical intermediates, the latter undergoing intramolecular C-C bond formation, allowing the planarization reaction to occur. The reaction conditions are mild and compatible with various electron-withdrawing and -donating substituents on the aryl rings as well as heterocycles and PAHs. The method could be applied to induce double annulation reactions, allowing the synthesis of π-extended scaffolds with different edge peripheries.

Bis-peri-dinaphtho-rylenes: Facile Synthesis via Radical-Mediated Coupling Reactions and their Distinctive Electronic Structures

Polycyclic aromatic hydrocarbons (PAHs) with a one-dimensional (1D), ribbon-like structure have the potential to serve as both model compounds for corresponding graphene nanoribbons (GNRs) and as materials for optoelectronics applications. However, synthesizing molecules of this type with extended π-conjugation presents a significant challenge. In this study, we present a straightforward synthetic method for a series of bis-peri-dinaphtho-rylene molecules, wherein the peri-positions of perylene, quaterrylene, and hexarylene are fused with naphtho-units. These molecules were efficiently synthesized primarily through intramolecular or intermolecular radical coupling of in situ generated organic radical species. Their structures were confirmed using X-ray crystallographic analysis, which also revealed a slightly bent geometry due to the incorporation of a cyclopentadiene ring at the bay regions of the rylene backbones. Bond lengh analysis and theoretical calculations indicate that their electronic structures resemble pyrenacenes more than quinoidal rylenes. That is, the aromatic sextets are predominantly localized along the long axis of the skeletones. As the chain length increases, these molecules exhibit enhanced electronic absorption with a bathochromic shift, and multiple amphoteric redox waves. This study introduces a novel synthetic approach for generating 1D extended PAHs and GNRs, along with their structure-dependent electronic properties.

On-surface synthesis of nitrogen-doped nanographene with an [18]annulene pore on Ag(111)

On-surface synthesis is of importance to fabricate low dimensional carbon-based nanomaterials with atomic precision. Here, we synthesize nitrogen-doped nanographene with an [18]annulene pore and its dimer through sequential reactions of debromination, aryl-aryl coupling, cyclodehydrogenation and C-N coupling on Ag(111) from 3,12-dibromo-7,8-diaza[5]helicene. The inner structures of the products were characterized with scanning tunneling microscopy with a CO terminated tip at low temperature. Furthermore, the first four unoccupied electronic states of the nanographene were investigated with a combination of scanning tunneling spectroscopy and theoretical calculations. Except for the LUMO + 2 state observed at +1.3 V, the electronic states at 500 mV, 750 mV and 1.9 V were attributed to the superatom molecular orbitals at the [18]annulene pore, which were significantly shifted towards the Fermi level due to the hybridization with the confined surface state.

Two-Dimensional (2D) materials in the detection of SARS-CoV-2

The SARS-CoV-2 pandemic has resulted in a devastating effect on human health in the last three years. While tremendous effort has been devoted to the development of effective treatment and vaccines against SARS-CoV-2 and controlling the spread of it, collective health challenges have been encountered along with the concurrent serious economic impacts. Since the beginning of the pandemic, various detection methods like PCR-based methods, isothermal nucleic acid amplification-based (INAA) methods, serological methods or antibody tests, and evaluation of X-ray chest results have been exploited to diagnose SARS-CoV-2. PCR-based detection methods in these are considered gold standards in the current stage despite their drawbacks, including being high-cost and time-consuming procedures. Furthermore, the results obtained from the PCR tests are susceptible to sample collection methods and time. When the sample is not collected properly, obtaining a false result may be likely. The use of specialized lab equipment and the need for trained people for the experiments pose additional challenges in PCR-based testing methods. Also, similar problems are observed in other molecular and serological methods. Therefore, biosensor technologies are becoming advantageous with their quick response, high specificity and precision, and low-cost characteristics for SARS-CoV-2 detection. In this paper, we critically review the advances in the development of sensors for the detection of SARS-CoV-2 using two-dimensional (2D) materials. Since 2D materials including graphene and graphene-related materials, transition metal carbides, carbonitrides, and nitrides (MXenes), and transition metal dichalcogenides (TMDs) play key roles in the development of novel and high-performance electrochemical (bio)sensors, this review pushes the sensor technologies against SARS-CoV-2 detection forward and highlights the current trends. First, the basics of SARS-CoV-2 detection are described. Then the structure and the physicochemical properties of the 2D materials are explained, which is followed by the development of SARS-CoV-2 sensors by exploiting the exceptional properties of the 2D materials. This critical review covers most of the published papers in detail from the beginning of the outbreak.

Molecularly or atomically precise nanostructures for bio-applications: how far have we come?

A huge variety of nanostructures are promising for biomedical applications, but only a few have been practically applied. Among the various reasons, the limited structural preciseness is a critical one, as it increases the difficulty in product quality control, accurate dosing, and ensuring the repeatability of material performance. Constructing nanoparticles with molecule-like preciseness is becoming a new research field. In this review, we focus on the artificial nanomaterials that can currently be molecularly or atomically precise, including DNA nanostructures, some metallic nanoclusters, dendrimer nanoparticles and carbon nanostructures, describing their syntheses, bio-applications and limitations, in view of up-to-date studies. A perspective on their potential for clinical translation is also given. This review is expected to provide a particular rationale for the future design of nanomedicines.

Two-Step Synthesis of B2 N2 -Doped Polycyclic Aromatic Hydrocarbon Containing Pentagonal and Heptagonal Rings with Long-Lived Delayed Fluorescence

Pentagon-heptagon embedded polycyclic aromatic hydrocarbons (PAHs) have aroused increasing attention in recent years due to their unique physicochemical properties. Here, for the first time, this report demonstrates a facile method for the synthesis of a novel B2 N2 -doped PAH (BN-2) containing two pairs of pentagonal and heptagonal rings in only two steps. In the solid state of BN-2, two different conformations, including saddle-shaped and up-down geometries, are observed. Through a combined spectroscopic and calculation study, the excited-state dynamics of BN-2 is well-investigated in this current work. The resultant pentagon-heptagon embedded B2 N2 -doped BN-2 displays both prompt fluorescence and long-lived delayed fluorescence components at room temperature, with the triplet excited-state lifetime in the microsecond time region (τ = 19 µs). The triplet-triplet annihilation is assigned as the mechanism for the observed long-lived delayed fluorescence. Computational analyses attributed this observation to the small energy separation between the singlet and triplet excited states, facilitating the intersystem crossing (ISC) process which is further validated by the ultrafast spectroscopic measurements.

Nanographene-Based Heterojunctions for High-Performance Organic Phototransistor Memory Devices

Organic phototransistors can enable many important applications such as nonvolatile memory, artificial synapses, and photodetectors in next-generation optical communication and wearable electronics. However, it is still a challenge to achieve a big memory window (threshold voltage response ∆V_th ) for phototransistors. Here, a nanographene-based heterojunction phototransistor memory with large ∆V_th responses is reported. Exposure to low intensity light (25.7 µW cm^-2 ) for 1 s yields a memory window of 35 V, and the threshold voltage shift is found to be larger than 140 V under continuous light illumination. The device exhibits both good photosensitivity (3.6 × 10⁵ ) and memory properties including long retention time (>1.5 × 10⁵  s), large hysteresis (45.35 V), and high endurance for voltage-erasing and light-programming. These findings demonstrate the high application potential of nanographenes in the field of optoelectronics. In addition, the working principle of these hybrid nanographene-organic structured heterojunction phototransistor memory devices is described which provides new insight into the design of high-performance organic phototransistor devices.

Facile preparation of conductive carbon-based membranes on dielectric substrates

Graphene has attracted much research attention due to its outstanding chemical and physical properties, such as its excellent electronic conductivity, making it as a useful carbon material for a variety of application fields of photoelectric functional devices. Herein, a new method for synthesizing conductive carbon membranes on dielectric substrates via a low-temperature thermodynamic driven process is developed. Although the obtained films exhibit low crystallinity, their electrical, wetting, and optical properties are acceptable in practice, which opens up a new avenue for the growth of carbon membranes and may facilitate the applications of transparent electrodes as potential plasma-free surface-enhanced Raman scattering (SERS) substrates.

Recent advances in n-type and ambipolar organic semiconductors and their multi-functional applications

Organic semiconductors have received broad attention and research interest due to their unique integration of semiconducting properties with structural tunability, intrinsic flexibiltiy and low cost. In order to meet the requirements of organic electronic devices and their integrated circuits, p-type, n-type and ambipolar organic semiconductors are all necessary. However, due to the limitation in both material synthesis and device fabrication, the development of n-type and ambipolar materials is quite behind that of p-type materials. Recent development in synthetic methods of organic semiconductors greatly enriches the range of n-type and ambipolar materials. Moreover, the newly developed materials with multiple functions also put forward multi-functional device applications, including some emerging research areas. In this review, we give a timely summary on these impressive advances in n-type and ambipolar organic semiconductors with a special focus on their synthesis methods and advanced materials with enhanced properties of charge carrier mobility, integration of high mobility and strong emission and thermoelectric properties. Finally, multi-functional device applications are further demonstrated as an example of these developed n-type and ambipolar materials.

Synthesis and Interlayer Assembly of a Graphenic Bowl with Peripheral Selenium Annulation

Pentagonal cyclization at the bay positions of armchair-edged graphenic cores can build molecular bowls without the destruction of hexagonal lattices. However, this synthesis remains challenging due to unfavorable strain and the multiple reactions required. Here, we show that a new type of graphenic molecular bowl with a depth of 1.7 Å and a diameter of 1.2 nm is constructed by sextuple Se annulation at the bay positions of armchair-edged hexa-peri-hexabenzocoronene. This graphenic bowl is functionalized with phenylseleno groups that stack into a discrete bilayer dimer in solution. Such a dimer exhibits high stability and survives in the gas phase after laser ablation. Strikingly, the asymmetric one-dimensional supramolecular columns of graphenic bowl with coherent stacking configuration are observed in the solid state, which results in a strong second harmonic generation with prominent polarization dependence. Our findings present a concise synthesis of a giant molecular bowl with a graphenic core and demonstrate the unique supramolecular assembly of extended graphenic bowls.

Synthesis of precisely functionalizable curved nanographenes via graphitization-induced regioselective chlorination in a mechanochemical Scholl Reaction

While the synthesis of nanographenes has advanced greatly in the past few years, development of their atomically precise functionalization strategies remains rare. The ability to modify the carbon scaffold translates to controlling, adjusting, and adapting molecular properties. Towards this end, here, we show that mechanochemistry is capable of transforming graphitization precursors directly into chlorinated curved nanographenes through a Scholl reaction. The halogenation occurs in a regioselective, high-yielding, and general manner. Density Functional Theory (DFT) calculations suggest that graphitization activates specific edge-positions for chlorination. The chlorine atoms allow for precise chemical modification of the nanographenes through a Suzuki or a nucleophilic aromatic substitution reaction. The edge modification enables modulation of material properties. Among the molecules prepared, corannulene-coronene hybrids and laterally fully π-extended helicenes, heptabenzo[5]superhelicenes, are particularly noteworthy.

Electrochemically driven [4+2] benzannulation: synthesis of polycyclic (hetero)aromatic compounds

A green and economical electrochemical protocol has been developed to synthesize polycyclic (hetero)aromatic compounds by the [4+2] benzannulation of biaryldiazonium salts with alkynes. This protocol features a broad substrate scope. Instead of requiring diazonium reagents, these reactions can begin from anilines and can be carried out in one pot. Moreover, the readily accessible scale-up synthesis achieved by using an electrochemical flow cell demonstrates the synthetic potential of this protocol.

Atomically Precise Distorted Nanographenes: The Effect of Different Edge Functionalization on the Photophysical Properties down to the Femtosecond Scale

Nanographenes (NGs) have been attracting widespread interest since they combine peculiar properties of graphene with molecular features, such as bright visible photoluminescence. However, our understanding of the fundamental properties of NGs is still hampered by the high degree of heterogeneity usually characterizing most of these materials. In this context, NGs obtained by atomically precise synthesis routes represent optimal benchmarks to unambiguously relate their properties to well-defined structures. Here we investigate in deep detail the optical response of three curved hexa-peri-hexabenzocoronene (HBC) derivatives obtained by atomically precise synthesis routes. They are constituted by the same graphenic core, characterized by the presence of a heptagon ring determining a saddle distortion of their sp² network, and differ from each other for slightly different edge functionalization. The quite similar structure allows for performing a direct comparison of their spectroscopic features, from steady-state down to the femtosecond scale, and precisely disentangling the role played by the different edge chemistry.

Synthetic carbon nanomaterials for electrochemical energy conversion

Carbon nanomaterials have attracted widespread attention in electrochemical energy conversion due to their large surface area, excellent electrical/thermal conductivity and good chemical stability. However, the structure-activity relationship of carbon nanomaterials remains unclear. This review is thus on the synthesis methods of carbon nanomaterials including two-dimensional graphene, graphene nanoribbons, nanographene, heteroatom doped porous carbon and graphdiyne as electrocatalysts for the hydrogen evolution reaction, oxygen evolution reaction, and oxygen reduction reaction in fuel cells, electrolyzers and CO₂ reduction. The correlation between the electronic/chemical properties and electrochemical performance of synthetic carbon nanostructures will be profoundly discussed. Additionally, the emerging challenges and some perspectives on the development of synthetic carbon nanomaterials for electrochemical energy conversion are discussed.

Wetting Properties of Clathrate Hydrates in the Presence of Polycyclic Aromatic Compounds: Evidence of Ion-Specific Effects

Polycyclic aromatic hydrocarbons (PAHs) have attracted remarkable multidisciplinary attention due to their intriguing π-π stacking configurations, showing enormous opportunity for their use in a variety of advanced applications. To secure progress, detailed knowledge on PAHs' interfacial properties is required. Employing molecular dynamics, we probe the wetting properties of brine droplets (KCl, NaCl, and CaCl₂) on sII methane-ethane hydrate surfaces immersed in various oil solvents. Our simulations show synergistic effects due to the presence of PAHs compounded by ion-specific effects. Our analysis reveals phenomenological correlations between the wetting properties and a combination of the binding free-energy difference and entropy changes upon oil solvation for PAHs at oil/brine and oil/hydrate interfaces. The detailed thermodynamic analysis conducted upon the interactions between PAHs and various interfaces identifies molecular-level mechanisms responsible for wettability alterations, which could be applicable for advancing applications in optics, microfluidics, biotechnology, medicine, as well as hydrate management.

Characterization of encapsulated graphene layers using extreme ultraviolet coherence tomography

Many applications of two-dimensional materials such as graphene require the encapsulation in bulk material. While a variety of methods exist for the structural and functional characterization of uncovered 2D materials, there is a need for methods that image encapsulated 2D materials as well as the surrounding matter. In this work, we use extreme ultraviolet coherence tomography to image graphene flakes buried beneath 200 nm of silicon. We show that we can identify mono-, bi-, and trilayers of graphene and quantify the thickness of the silicon bulk on top by measuring the depth-resolved reflectivity. Furthermore, we estimate the quality of the graphene interface by incorporating a model that includes the interface roughness. These results are verified by atomic force microscopy and prove that extreme ultraviolet coherence tomography is a suitable tool for imaging 2D materials embedded in bulk materials.

Engineering of graphene quantum dots by varying the properties of graphene oxide for fluorescence detection of picric acid

The study examines the effect of different forms of graphene oxide (GO) on the synthesis of graphene quantum dots (GQD). GO synthesized at various temperatures i.e. 30, 50, 110 °C possessed different structural and functional properties and was used as a substrate for GQD preparation. Thorough characterization of the GQDs in terms of their structural, morphological, functional, and optical properties was performed. The GQDs exhibited variation in their size and fluorescence properties depending upon the type of GO used. Hydrothermal reduction of GO, prepared at an oxidation temperature of 50 °C (GO-50), minimized the particle size (3.6 nm) and maximized the photoluminescence (PL) intensity and quantum yield (64.8%) of the GQD (GQD-50). GQD-50 was found to detect picric acid (PA) in an aqueous solution via 'turn-off' fluorescence quenching, unlike the other GQDs where the initial precursor is synthesized at 30, 110 °C. Experimental studies summarize that interaction between the fluorophore-quencher resulted in static quenching. The limit of detection was estimated to be 1.2 μM with a detection range of 0-200 μM. The work concludes that optimization of the substrate i.e. GO can result in the development of a simple, non-toxic, cost-effective GQD based sensor for PA detection. The study eliminates the need for doping/functionalization of GQDs as reported previously, and hence finds a promising impact on the development of sensors.

Fundamental Properties of Transition-Metals-Adsorbed Germanene: A DFT Study

The transition metal (TM)-absorbed germanene systems enriched by strong chemical bonding are investigated using first-principles calculations. Dedicated calculations include the geometry, preferable adsorption sites, atom-dominated band structure, spin–density distributions, spatial charge distribution, and the projected density of states (DOS). The strong multi-orbital chemical bonds between TMs and Ge atoms can create seriously buckled structures and a non-uniform chemical environment, which are responsible for the unusual electronic properties. Of the three chosen systems, the Fe–Ge and Co–Ge ones possess magnetic properties, while the Ni–Ge system exhibits non-magnetic behavior. The orbital-hybridization-induced characteristics are revealed in van Hove singularities of the DOS.

Doubling the Length of the Longest Pyrene-Pyrazinoquinoxaline Molecular Nanoribbons

Molecular nanoribbons are a class of atomically-precise nanomaterials for a broad range of applications. An iterative approach that allows doubling the length of the longest pyrene-pyrazinoquinoxaline molecular nanoribbons is described. The largest nanoribbon obtained through this approach-with a 60 linearly-fused ring backbone (14.9 nm) and a 324-atoms core (C276 N48 )-shows an extremely high molar absorptivity (values up to 1 198 074 M-1  cm-1 ) that also endows it with a high molar fluorescence brightness (8700 M-1  cm-1 ).

Atomically Precise Water-Soluble Graphene Quantum Dot for Cancer Sonodynamic Therapy

Although water-soluble graphene quantum dots (GQDs) have shown various promising bio-applications due to their intriguing optical and chemical properties, the large heterogeneity in compositions, sizes, and shapes of these GQDs hampers the better understanding of their structure-properties correlation and further uses in terms of large-scale manufacturing practices and safety concerns. It is shown here that a water-soluble atomically-precise GQD (WAGQD-C96 ) is synthesized and exhibits a deep-red emission and excellent sonodynamic sensitization. By decorating sterically hindered water-soluble functional groups, WAGQD-C96 can be monodispersed in water without further aggregation. The deep-red emission of WAGQD-C96 facilitates the tracking of its bio-process, showing a good cell-uptake and long-time retention in tumor tissue. Compared to traditional molecular sonosensitizers, WAGQD-C96 generates superior reactive oxygen species and demonstrates excellent tumor inhibition potency as an anti-cancer sonosensitizer in in vivo studies. A good biosafety of WAGQD-C96 is validated in both in vitro and in vivo assays.

Solution Synthesis and Characterization of a Long and Curved Graphene Nanoribbon with Hybrid Cove-Armchair-Gulf Edge Structures

Curved graphene nanoribbons (GNRs) with hybrid edge structures have recently attracted increasing attention due to their unique band structures and electronic properties as a result of their nonplanar conformation. This work reports the solution synthesis of a long and curved multi-edged GNR (cMGNR) with unprecedented cove-armchair-gulf edge structures. The synthesis involves an efficient A₂ B₂ -type Diels-Alder polymerization between a diethynyl-substituted prefused bichrysene monomer (3b) and a dicyclopenta[e,l]pyrene-5,11-dione derivative (6) followed by FeCl₃ -mediated Scholl oxidative cyclodehydrogenation of the obtained polyarylenes (P1). Model compounds 1a and 1b are first synthesized to examine the suitability and efficiency of the corresponding polymers for the Scholl reaction. The successful formation of cMGNR from polymer P1 bearing prefused bichrysene units is confirmed by FTIR, Raman, and solid-state NMR analyses. The cove-edge structure of the cMGNR imparts the ribbon with a unique nonplanar conformation as revealed by density functional theory (DFT) simulation, which effectively enhances its dispersibility in solution. The cMGNR has a narrow optical bandgap of 1.61 eV, as estimated from the UV-vis absorption spectrum, which is among the family of low-bandgap solution-synthesized GNRs. Moreover, the cMGNR exhibits a carrier mobility of ≈2 cm² V^-1 s^-1 inferred from contact-free terahertz spectroscopy.

Controlled Growth and Self-Assembly of Multiscale Organic Semiconductor

Currently, organic semiconductors (OSs) are widely used as active components in practical devices related to energy storage and conversion, optoelectronics, catalysis, and biological sensors, etc. To satisfy the actual requirements of different types of devices, chemical structure design and self-assembly process control have been synergistically performed. The morphology and other basic properties of multiscale OS components are governed on a broad scale from nanometers to macroscopic micrometers. Herein, the up-to-date design strategies for fabricating multiscale OSs are comprehensively reviewed. Related representative works are introduced, applications in practical devices are discussed, and future research directions are presented. Design strategies combining the advances in organic synthetic chemistry and supramolecular assembly technology perform an integral role in the development of a new generation of multiscale OSs.

Effects of graphene oxide nanosheets in the polychaete Hediste diversicolor: Behavioural, physiological and biochemical responses

Numerous applications exist for graphene-based materials, such as graphene oxide (GO) nanosheets. Increased concentrations of GO nanosheets in the environment have the potential to have a large negative effect on the aquatic environment, with consequences for benthic organisms, such as polychaetes. The polychaete Hediste diversicolor mobilises the sediments, hence altering the availability of contaminants and the nutrients biogeochemical cycle. As such, this study proposes to assess the effects of different GO nanosheet concentrations on the behaviour, feeding activity, mucus production, regenerative capacity, antioxidant status, biochemical damage and metabolism of H. diversicolor. This study evidenced that H. diversicolor exposed to GO nanosheets had a significantly lower ability to regenerate their bodies, took longer to feed and burrow into the sediment and produced more mucus. Membrane oxidative damage (lipid peroxidation) increased in exposed specimens. The increased metabolic rate (ETS) evidenced a higher energy expenditure in exposed organisms (high use of ready energy sources - soluble sugars) to fight the toxicity induced by GO nanosheets, such as SOD activity. The increase in SOD activity was enough to reduce reactive oxygen species (ROS) induced by GO on cytosol at the lowest concentrations, avoiding the damage on proteins (lower PC levels), but not on membranes (LPO increase). This study revealed that the presence of GO nanosheets, even at the lower levels tested, impaired behavioural, physiological, and biochemical traits in polychaetes, suggesting that the increase of this engineered nanomaterial in the environment can disturb these benthic organisms, affecting the H. diversicolor population. Moreover, given the important role of this group of organisms in coastal and estuarine food webs, the biogeochemical cycle of nutrients, and sediment oxygenation, there is a real possibility for repercussions into the estuarine community.