Long-range ordered porous carbons produced from C60.

Carbon structures with covalent bonds connecting C60 molecules have been reported1-3, but their production methods typically result in very small amounts of sample, which restrict the detailed characterization and exploration necessary for potential applications. We report the gram-scale preparation of a new type of carbon, long-range ordered porous carbon (LOPC), from C60 powder catalysed by α-Li3N at ambient pressure. LOPC consists of connected broken C60 cages that maintain long-range periodicity, and has been characterized by X-ray diffraction, Raman spectroscopy, magic-angle spinning solid-state nuclear magnetic resonance spectroscopy, aberration-corrected transmission electron microscopy and neutron scattering. Numerical simulations based on a neural network show that LOPC is a metastable structure produced during the transformation from fullerene-type to graphene-type carbons. At a lower temperature, shorter annealing time or by using less α-Li3N, a well-known polymerized C60 crystal forms owing to the electron transfer from α-Li3N to C60. The carbon K-edge near-edge X-ray absorption fine structure shows a higher degree of delocalization of electrons in LOPC than in C60(s). The electrical conductivity is 1.17 × 10-2 S cm-1 at room temperature, and conduction at T < 30 K appears to result from a combination of metallic-like transport over short distances punctuated by carrier hopping. The preparation of LOPC enables the discovery of other crystalline carbons starting from C60(s).

Rapid Yet Efficient Reduction of Graphene Oxide Triggered by Semi-Molten Metals.

Reduced graphene oxide (rGO) has garnered extensive attention as electrodes, sensors, and membranes, necessitating the efficient reduction of graphene oxide (GO) for optimal performance. In this work, a swift reduction of GO that involves bringing GO foam in contact with semi-molten metals like tin (Sn) and lithium (Li) is presented. These findings reveal that the electrical resistance of GO foam is significantly diminished by its interaction with these metals, even in dry air. Taking inspiration from this technique, Sn foil is employed to encase the GO foam, followed by a calcination in 15 vol% H2 /Ar environment at 235 °C to fabricate the rGO, which demonstrates a remarkably lower electrical resistivity of 0.42 Ω cm when compared to the chemically reduced GO via hydrazine hydrate (650 Ω cm). The reduction mechanism entails the migration of Sn on GO and its subsequent reaction with oxygen functional groups. SnO/Sn(OH)2 formed from the reaction can be subsequently reversed through reduction by H2 to Sn. Utilizing this rGO as the host material for a sulfur cathode, a lithium-sulfur battery is constructed that displays a specific capacity of 1146 mAh g-1 and maintains a capacity retention of 68.4% after 300 cycles at a rate of 0.2 C.

Precisely Regulating Asymmetric Charge Distribution by Single-Atom Central Doped Ag-Based Series Clusters for Enhanced Photoreduction of CO2 to Alcohol Fuels.

High efficiently photocatalytic CO2 reduction (CO2RR) into liquid fuels in pure water system remains challenged. Iron polyphthalocyanine (FePPc) with strong light harvesting, unique Fe-N4 structure, abundant pores, and good stability could serve as a promising catalyst for CO2 photoreduction. To further improve the catalytic efficiency, herein, symmetry-breaking Fe sites are constructed by coupling with atomically precise M1Ag24 (M=Ag, Au, Pt) series clusters. Especially, the introduction of Pt1Ag24 causes the most asymmetric charge distribution of Fe in FePPc (followed by Au1Ag24 and Ag25), leading to the favorable CO2 adsorption and activation. In addition, Pt1Ag24-FePPc exhibits the most effective photogenerated carriers transfer and separation. As a result, Pt1Ag24-FePPc shows the methanol/ethanol yield of 48.55/32.97 µmol·gcat-1·h-1 in H2O-CO2 system under visible light irradiation, ~ 1.65/1.25-fold, 1.83/1.37-fold, and 3.6/1.61-fold higher than that of Au1Ag24-FePPc, Ag25-FePPc, and FePPc, respectively. This work provides a concept for precisely construction and regulation symmetry-breaking sites of cluster-based catalysts for effective CO2 conversion.

Erratum: Stronger Interlayer Interactions Contribute to Faster Hot Carrier Cooling of Bilayer Graphene under Pressure [Phys. Rev. Lett. 126, 027402 (2021)].

This corrects the article DOI: 10.1103/PhysRevLett.126.027402.

Phase-Changing in Graphite Assisted by Interface Charge Injection.

Among many phase-changing materials, graphite is probably the most studied and interesting: the rhombohedral (3R) and hexagonal (2H) phases exhibit dramatically different electronic properties. However, up to now the only way to promote 3R to 2H phase transition is through exposure to elevated temperatures (above 1000 °C); thus, it is not feasible for modern technology. In this work, we demonstrate that 3R to 2H phase transition can be promoted by changing the charged state of 3D graphite, which promotes the repulsion between the layers and significantly reduces the energy barrier between the 3R and 2H phases. In particular, we show that charge transfer from lithium nitride (α-Li3N) to graphite can lower the transition temperature down to 350 °C. The proposed interlayer slipping model potentially offers the control over topological states at the interfaces between different phases, making this system even more attractive for future electronic applications.

Stronger Interlayer Interactions Contribute to Faster Hot Carrier Cooling of Bilayer Graphene under Pressure.

We perform femtosecond pump-probe spectroscopy to in situ investigate the ultrafast photocarrier dynamics in bilayer graphene and observe an acceleration of energy relaxation under pressure. In combination with in situ Raman spectroscopy and ab initio molecular dynamics simulations, we reveal that interlayer shear and breathing modes have significant contributions to the faster hot-carrier relaxations by coupling with the in-plane vibration modes under pressure. Our work suggests that further understanding the effect of interlayer interaction on the behaviors of electrons and phonons would be critical to tailor the photocarrier dynamic properties of bilayer graphene.

Electrochemical Characterization of Single Layer Graphene/Electrolyte Interface: Effect of Solvent on the Interfacial Capacitance.

The development of the basic understanding of the charge storage mechanisms in electrodes for energy storage applications needs deep characterization of the electrode/electrolyte interface. In this work, we studied the charge of the double layer capacitance at single layer graphene (SLG) electrode used as a model material, in neat (EMIm-TFSI) and solvated (with acetonitrile) ionic liquid electrodes. The combination of electrochemical impedance spectroscopy and gravimetric electrochemical quartz crystal microbalance (EQCM) measurements evidence that the presence of solvent drastically increases the charge carrier density at the SLG/ionic liquid interface. The capacitance is thus governed not only by the electronic properties of the graphene, but also by the specific organization of the electrolyte side at the SLG surface originating from the strong interactions existing between the EMIm+ cations and SLG surface. EQCM measurements also show that the carbon structure, with the presence of sp2 carbons, affects the charge storage mechanism by favoring counter-ion adsorption on SLG electrode versus ion exchange mechanism in amorphous porous carbons.

Graphene foil as a current collector for NCM material-based cathodes.

When used as a current collector, aluminum foil (AF) is vulnerable to local anodic corrosion during the charge/discharge process, which can lead to the deterioration of lithium-ion batteries (LIBs). Herein, a graphene foil (GF) with high electrical conductivity (∼5800 S cm-1) and low mass density (1.80 g cm-3) was prepared by reduction of graphene oxide foil with ultra-high temperature (2800 °C) annealing, and it exhibited significantly anodic corrosion resistance when serving as a current collector. Moreover, a LiNi0.5Co0.2Mn0.3O2 (NCM523) cathode using GF as a current collector (NCM523/GF) demonstrated a gravimetric capacity of 137.3 mAh g-1 at 0.5 C based on the mass of the whole electrode consisting of the active material, carbon black, binder, and the current collector, which is 44.5% higher than that of the NCM523/AF electrode. Furthermore, the NCM523/GF electrode retains higher capacity at relatively faster rates, from 0.1 C to 5.0 C. Therefore, GF, a lightweight corrosion-resistant current collector, is expected to replace the current commercial metal current collectors in LIBs and to achieve high energy-density batteries.

Charge Storage Mechanisms of Single-Layer Graphene in Ionic Liquid.

Graphene-based carbon materials are promising candidates for electrical double-layer (EDL) capacitors, and there is considerable interest in understanding the structure and properties of the graphene/electrolyte interface. Here, electrochemical impedance spectroscopy (EIS) and electrochemical quartz crystal microbalance (EQCM) are used to characterize the ion fluxes and adsorption on single-layer graphene in neat ionic liquid (EMI-TFSI) electrolyte. It is found that a positively charged ion-species desorption and ion reorganization dominate the double-layer charging during positive and negative polarizations, respectively, leading to the increase in EDL capacitance with applied potential.

Diameter-Sensitive Breakdown of Single-Walled Carbon Nanotubes upon KOH Activation.

While potassium hydroxide (KOH) activation has been used to create pores in carbon nanotubes (CNTs) for improved energy-storage performance, the KOH activation mechanism of CNTs has been rarely investigated. In this work, the reaction between single-walled CNTs (SWCNTs) and KOH is studied in situ by thermogravimetric analysis coupled to infrared (IR) spectroscopy and gas chromatography/mass spectrometry (MS). The IR and MS results clearly demonstrate the sequential evolution of CO, hydrocarbons, CO2 , and H2 O in the activation process. By using the radial breathing mode of Raman spectroscopy, a diameter-sensitive selectivity is observed in the reaction between SWCNTs and KOH, leading to a preferential distribution of SWCNTs with diameters larger than 1 nm after activation at 900 °C and a preferential removal of SWCNTs with diameters below 1 nm upon activation.

Creating Pores on Graphene Platelets by Low-Temperature KOH Activation for Enhanced Electrochemical Performance.

KOH activation of microwave exfoliated graphite oxide (MEGO) is investigated in detail at temperatures of 450-550 °C. Out of the activation temperature range conventionally used for the preparation of activated carbons (>600 °C), the reaction between KOH and MEGO platelets at relatively low temperatures allows one to trace the structural transition from quasi-two-dimensional graphene platelets to three-dimensional porous carbon. In addition, it is found that nanometer-sized pores are created in the graphene platelets at the activation temperature of around 450 °C, leading to a carbon that maintains the platelet-like morphology, yet with a specific surface area much higher than MEGO (e.g., increased from 156 to 937 m(2) g(-1) ). Such a porous yet highly conducting carbon shows a largely enhanced electrochemical activity and thus improved electrochemical performance when being used as electrodes in supercapacitors. A specific capacitance of 265 F g(-1) (185 F cm(-3) ) is obtained at a current density of 1 A g(-1) in 6 m KOH electrolyte, which remains 223 F g(-1) (156 F cm(-3) ) at the current density of 10 A g(-1) .

Rupturing C60 Molecules into Graphene-Oxide-like Quantum Dots: Structure, Photoluminescence, and Catalytic Application.

The large-scale synthesis of graphene-oxide-like quantum dots (GOLQDs) is reported by oxidizing C(60) molecules using a modified Hummers method with a yield of ≈25 wt% readily achieved. The GOLQDs are highly soluble in water and in addition to hexagons have other carbon rings in the structure. They have an average height of ≈1.2 nm and a diameter distribution of 0.6-2.2 nm after drying on substrates. First-principle calculations indicate that a possible rupturing route may include the insertion of oxygen atoms to CC bonds in the C(60) molecule, followed by rupture of that CC bonds. The GOLQD suspension has a strong photoluminescence (PL) with peak position dependent on excitation wavelength. The PL is related to the size and emissive traps caused by oxygen-containing groups. The GOLQDs also catalyze the oxidation of benzyl alcohol with a high selectivity.

Ultrauniform Plating of Lithium on 10-nm-Scale Ordered Carbon Grids for Long Lifespan Lithium Metal Batteries.

Tailorable lithium (Li) nucleation and uniform early-stage plating is essential for long-lifespan Li metal batteries. Among factors influencing the early plating of Li anode, the substrate is critical, but a fine control of the substrate structure on a scale of ≈10 nm has been rarely achieved. Herein, a carbon consisting of ordered grids is prepared, as a model to investigate the effect of substrate structure on the Li nucleation. In contrast to the individual spherical Li nuclei formed on the flat graphene, an ultrauniform and nuclei-free Li plating is obtained on the ordered carbon with a grid size smaller than the thermodynamical critical radius of Li nucleation (≈26 nm). Simultaneously, an inorganic-rich solid-electrolyte-interphase is promoted by the cross-sectional carbon layers of such ordered grids which are exposed to the electrolyte. Consequently, the carbon grids with a grid size of ≈10 nm show a favorable cycling stability for more than 1100 cycles measured at 2 mA cm-2 in a half cell. With LiNi0.8Co0.1Mn0.1O2 as cathode, the assembled full cell with a cathode capacity of 3 mAh cm-2 and a negative/positive ratio of 1.67 demonstrates a stable cycling for over 130 cycles with a capacity retention of 88%.

Olanzapine for the prevention of postoperative nausea and vomiting after gynecologic laparoscopic surgery: a randomized controlled trial.

Purpose: This study was designed to investigate the prophylactic effect of oral olanzapine in postoperative nausea and vomiting after gynecologic laparoscopic surgery. Methods: ASA I-II, aged 18-75 years, planned to undergo gynecologic laparoscopic surgery with general anesthesia in adult female patients. Using the randomized numbers table, the patients were placed in two groups. Oral olanzapine 5 mg or placebo was given 1 h before anesthesia. All patients received standard antiemetic prophylaxis with dexamethasone and granisetron. The primary outcome was nausea and/or vomiting in the 24 h after the postoperative. Results: A total of 250 patients were randomized, and 241 were analyzed. The primary outcome occurred in 10 of 120 patients (8.3%) in the olanzapine group and 23 of 121 patients (19.2%) in the placebo group (p = 0.014). According to Kaplan-Meier analysis, the probabilities of nausea and/or vomiting in the 24 h after the postoperative in the olanzapine group were lower than in the placebo group (log-rank p = 0.014). In a multivariate Cox analysis, the variables of use of olanzapine [hazard ratio (HR): 0.35, 95% confidence interval (CI): 0.16-0.79; p = 0.012] and use of vasoactive drugs (HR: 2.48, 95% CI: 1.07-5.75; p = 0.034) were independently associated with nausea and/or vomiting in the 24 h after the postoperative. Conclusion: Our data suggest that olanzapine relative to placebo decreased the risk of nausea and/or vomiting in the 24 h after gynecologic laparoscopic surgery. Trial registration: The trial was registered prior to patient enrollment at The Chinese Clinical Trial Registry (https://www.chictr.org.cn/showproj.html?proj=166900, link to registry page, Principal investigator: Nanjin Chen, Date of registration: 25 April 2022).

Preventing nausea and vomiting after laparoscopic gynecological surgery: the benefits of using olanzapine Why was this study done? Despite the use of antiemetics, postoperative nausea and vomiting remain prevalent. Furthermore, patients who undergo gynecological laparoscopic surgery are at an increased risk. Therefore, this study investigated whether oral Olanzapine could reduce the incidence of nausea and vomiting after gynaecological Laparoscopy? What did the researchers do? The research team examined patients who underwent gynecological laparoscopic surgery under general anesthesia. They observed the occurrence of nausea and vomiting within 24 hours after surgery in patients who either received or did not receive Olanzapine treatment. The goal was to assess the effectiveness of Olanzapine in reducing postoperative nausea and vomiting. What did the researchers find? The addition of Olanzapine, when combined with granisetron and dexamethasone, resulted in a decreased risk of nausea and/or vomiting within the 24 hours following gynecologic laparoscopic surgery, as compared to the placebo. Administering oral Olanzapine at a dosage of 5 mg reduced the incidence of nausea and vomiting after gynecological laparoscopy from 19.2% to 8.3%. What do the findings mean? This study has identified a safe and effective medication for preventing postoperative nausea and vomiting. Implementing Olanzapine as a preventive measure can significantly reduce the incidence of nausea and vomiting following surgery, thereby enhancing the overall medical experience for patients.

Infrared biosensors based on graphene plasmonics: modeling.

We propose a biosensor by exploiting localized plasmons in graphene and biomolecule adsorption on it. Numerical simulations demonstrate that the sensitivity of such a device can achieve a high value of up to 1697 nm/RIU (refractive index unit) when the wavelength shift at the plasmon resonance is detected. The transparent substrate supporting graphene can be chosen potentially from a wide range of materials including insulators, semiconductors, polymers, and gels. The plasmon resonance wavelength can be tuned with electrostatic doping and/or structure modulation of graphene. Furthermore, the device works in a wide angle range of incident light since the transverse magnetic (TM) polarization is independent of incident angles.

Highly conductive and porous activated reduced graphene oxide films for high-power supercapacitors.

We present a novel method to prepare highly conductive, free-standing, and flexible porous carbon thin films by chemical activation of reduced graphene oxide paper. These flexible carbon thin films possess a very high specific surface area of 2400 m(2) g(-1) with a high in-plane electrical conductivity of 5880 S m(-1). This is the highest specific surface area for a free-standing carbon film reported to date. A two-electrode supercapacitor using these carbon films as electrodes demonstrated an excellent high-frequency response, an extremely low equivalent series resistance on the order of 0.1 ohm, and a high-power delivery of about 500 kW kg(-1). While higher frequency and power values for graphene materials have been reported, these are the highest values achieved while simultaneously maintaining excellent specific capacitances and energy densities of 120 F g(-1) and 26 W h kg(-1), respectively. In addition, these free-standing thin films provide a route to simplify the electrode-manufacturing process by eliminating conducting additives and binders. The synthetic process is also compatible with existing industrial level KOH activation processes and roll-to-roll thin-film fabrication technologies.

[Study of interaction of umbelliferone with three aromatic amino acids by fluorescence spectroscopy].

The interaction between umbelliferone (UMB) with tryptophan (Trp), tyrosine (Tyr) and phenylalanine (Phe) was studied by using fluorescence (FS) and ultraviolet (UV) spectroscopy. The results show that UMB can strongly quench the fluorescence of the three aromatic amino acids with the maximum quenching wavelengths at 347, 303 and 282 nm, respectively. Data analyses based on the Stern-Volmer curve and the UV spectroscopy show that static quenching occurred through the formation of the complexes of UMB with each aromatic amino acid in a molar ratio of 1 : 1. The binding constant K(c) of UMB with Trp, Tyr and Phe is 2.993 x 10(6), 7.858 x 10(4) and 1.186 x 10(3) L x mol(-1) (298.15 K) and 2.702 x 10(4), 1.063 x 10(5) and 8.352 x 10(3) L x mol(-1) (310.15 K), respectively. The thermodynamic parameters indicate that UMB has a strong interaction with the three aromatic amino acids. Hydrogen bond and Van der Waals force may play a major role in the reaction of UMB with Trp, whereas hydrophobic interaction should be responsible for the binding of UMB with Tyr and Phe. In addition, the dipole-dipole interaction may be another factor in the reactions between UMB and the three aromatic aminoacids.

Synthesis of α-Trifluoromethyl Alkynes through Fluoroalkynylation of gem-Difluoroalkenes.

A trifluoromethylalkynylation reaction of gem-difluoroalkenes with alkynyl sulfoxide by photoredox radical addition with good functional group tolerance in moderate to high yields, is developed for the synthesis of α-trifluoromethyl alkyne. This reaction features simple operation and inexpensive raw materials and provides an expeditious route to synthesize biologically relevant fluorine-containing alkynyl compounds with diverse structural skeletons.

Hierarchical palladium catalyst for highly active and stable water oxidation in acidic media.

Acidic water electrolysis is of great importance for boosting the development of renewable energy. However, it severely suffers from the trade-off between high activity and long lifespan for oxygen evolution catalysts on the anode side. This is because the sluggish kinetics of oxygen evolution reaction necessitates the application of a high overpotential to achieve considerable current, which inevitably drives the catalysts far away from their thermodynamic equilibrium states. Here we demonstrate a new oxygen evolution model catalyst-hierarchical palladium (Pd) whose performance even surpasses the benchmark Ir- and Ru-based materials. The Pd catalyst displays an ultralow overpotential (196 mV), excellent durability and mitigated degradation (66 µV h-1) at 10 mA cm-2 in 1 M HClO4. Tensile strain on Pd (111) facets weakens the binding of oxygen species on electrochemical etching-derived hierarchical Pd and thereby leads to two orders of magnitudes of enhancement of mass activity in comparison to the parent Pd bulk materials. Furthermore, the Pd catalyst displays the bifunctional catalytic properties for both oxygen and hydrogen evolutions and can deliver a current density of 2 A cm-2 at a low cell voltage of 1.771 V when fabricated into polymer electrolyte membrane electrolyser.

Activated graphene as a cathode material for Li-ion hybrid supercapacitors.

Chemically activated graphene ('activated microwave expanded graphite oxide', a-MEGO) was used as a cathode material for Li-ion hybrid supercapacitors. The performance of a-MEGO was first verified with Li-ion electrolyte in a symmetrical supercapacitor cell. Hybrid supercapacitors were then constructed with a-MEGO as the cathode and with either graphite or Li(4)Ti(5)O(12) (LTO) for the anode materials. The results show that the activated graphene material works well in a symmetrical cell with the Li-ion electrolyte with specific capacitances as high as 182 F g(-1). In a full a-MEGO/graphite hybrid cell, specific capacitances as high as 266 F g(-1) for the active materials at operating potentials of 4 V yielded gravimetric energy densities for a packaged cell of 53.2 W h kg(-1).