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Abstract: Here we provide evidence of two selective growth modes, namely the ‘surface adsorption (SA) mode’ and the ‘diffusion and precipitation (DP) mode’ for the synthesis of graphene on Cu foil by thermal chemical vapor deposition. Using acetylene feedstock, the number of graphene layers was controlled simply by adjusting the injection time, and the DP growth mode was clearly verified by the existence of a carbon-diffused Cu layer with expansion of the Cu lattice. With methane feedstock, either SA or DP growth modes could be selected for the growth of graphene at low or high partial pressure of carbon feedstocks, respectively. The critical pressure for switching the growth modes depends on reactivity of carbon feedstock to Cu substrate. [Copyright &y& Elsevier]

Abstract: An easy method for decorating multi-walled carbon nanotubes (MWCNTs) with metal nanoparticles (NPs) of a uniform size is reported. The NPs were obtained by energy-tunable MeV electron beam irradiation (MEBI) on NiCl2·6H2O-coated and PtCl2-coated MWCNTs at room temperature and ambient conditions. X-ray photoelectron spectroscopy clearly revealed that MEBI induced Cl desorption, leading to the formation of Ni (5.16±0.74nm) and Pt (1.63±0.15nm) NPs. Since this was achieved without destruction of MWCNTs, MEBI can be a universal method for obtaining any metal NP on CNTs if the metal forms a compound with Cl. [Copyright &y& Elsevier]

Graphene has shown many advantages over the metal oxide transparent materials that serve as conventional electrodes in solar cells because graphene is more transparent, has greater stability, and is more mechanically flexible. Flexibility and semi-transparency of the perovskite solar cells are challenged to integrate with the flexible electronic devices since the perovskite solar cells have discovered. Herein, we provide the first report of transfer-free, large-scale monolayer graphene employed as a transparent and flexible bottom electrode. High-quality graphene without transfer process was directly synthesized at 150 °C on a polymer substrate via plasma assisted thermal chemical vapor deposition (PATCVD). Additionally, a highly transparent AZO/Ag/AZO (AAA) multilayer was utilized as a top counter electrode to create semi-transparent perovskite solar cells with a remarkable degree of mechanical flexibility. The 300 nm-thick perovskite solar cells with PATCVD-Graphene revealed a high transmittance of ~26% at a wavelength of 700 nm. The highest level of power conversion efficiency (PCE) (~14.2%) was recorded by an illumination from the bottom graphene side. After 1000 bending cycles under a tensile strain of 1.5%, the graphene-based devices maintained a level of PCE that was more than 90% greater than the initial reading. This superior bending robustness highlights the potential for non-transfer, graphene-based, perovskite photovoltaic material to establish a tandem structure for a foldable solar cell. Image 1 • High-quality graphene without transfer process was directly synthesized at 150 °C on a polymer substrate as transparent electrode. • The smooth surface with grain size upon 700 nm of MAPbI 3 perovskite has been obtained by CVD process. • Solar-cell devices with PATCVD-graphene electrodes demonstrated a PCE of 14.2% with a transmittance ~26% at a wavelength of 700 nm. • PSC devices demonstrated a great flexibility, maintaining 90% of the original PCE value after 1000 bending cycles under a tensile strain of 1.5%. [ABSTRACT FROM AUTHOR]

Large-area graphene synthesized by a chemical vapor deposition (CVD) method is promising for a flexible, stretchable transparent electrode but suffers from structural defects such as grain boundaries, which causes to degrade its physical properties. Recently, preparation methods of large-scale growth templates for single-crystalline graphene (SCG) were reported, but the macroscopic properties of SCG have not been adequately examined yet. Here, an SCG-based flexible, stretchable graphene transparent electrode is successfully demonstrated, which shows superior optoelectrical, electromechanical, and barrier properties compared to polycrystalline graphene (PCG)-based transparent electrodes. The result exhibits the grain boundary effect of graphene on soft substrates on a macroscopic scale and a great promise toward realizing a tremendous performance improvement of graphene-based flexible transparent electrodes on a large scale. [Display omitted] • The macroscopic properties of SCG and PCG related to transparent electrode application are examined. • SCG and PCG were synthesized and confirmed with various methods both in microscopic and macroscopic scale. • According to the scaling law, graphene without GBs may not have advantages in its physical properties. • The graphene GBs highly affect electromechanical and barrier properties, as well as electrical conductivity. • Using SCG instead of PCG for flexible transparent electrodes is worth it for its improved long-term stability. [ABSTRACT FROM AUTHOR]

Thin film of Fe(TCNQ:tetracyanoquinodimethane) x ∼2 that exhibits both ferromagnetic and semiconducting behavior was developed by physical vapor deposition. The IR and photoemission spectra display clear evidences of coordination between metal and TCNQ based on charge transfer rather than physical mixture. The shifts of C and N 1s core-level spectra due to metal-TCNQ coordination reveal the local spin density of the TCNQ − anion, predicted by DFT calculation. The valence band spectra of the Fe(TCNQ) x ∼2 thin film also confirm the formation of a singly occupied molecular orbital (SOMO) in TCNQ - , which leads to long-range magnetic order as confirmed by a vibrating sample magnetometer. [ABSTRACT FROM AUTHOR]

• N and F doped GQDs were synthesized by two-step functionalization method. • N,F-GQDs exhibit enhanced electrocatalytic and electrochemical reaction activities. • N,F co-doped GQDs efficiently work on HER, OER, and supercapacitor. Development of efficient electrochemical catalysts is crucial for clean energy technologies such as water splitting, and batteries, etc. Despite large amounts of electrocatalyst research, it remains a challenge to eco-friendly non-metal catalyst showing high performance as much as novel metal. To achieve high performance as much as noble-metal, carbon nanomaterials (CNMs) have been attracted as a candidate to the widespread application using electrochemical reaction. Herein, we report nitrogen, and fluorine co-doped graphene quantum dot (N,F-GQDs) synthesized by two-step functionalizing method for highly efficient overall water splitting. N,F-GQDs demonstrate electrocatalytic effect toward HER, and OER, and is fabricated as two-electrode full-water splitting showing good stability at various potential points. Furthermore, due to fluorine treatment, prepared N,F-GQDs exhibits enhanced electrochemical reaction property, which can induce capacitance due to the large difference of electronegativity between fluorine and carbon. N,F-GQDs is applied for the anode of super capacitance in the three-electrode system and reveal specific capacitance of 270 F g−1 at 1 mV s−1 from CV curves, and GCD capacitance of 244 F g−1 at 3 mA cm−2. This work provides a new avenue for enhancing both activities of the electrocatalytic and electrochemical reaction. [ABSTRACT FROM AUTHOR]

A composite sorbent for the simultaneous removal of both Hg2+ and SeO 3 2− from aqueous media was produced from the solvothermal synthesis of a zirconium metal organic framework, UiO-66, in the presence of activated carbon. The composite sorbent has a large surface area of 1051 m2 g−1 with crystalized porous structures and has strong thermal stability up to 600 °C. The contaminant uptake of the sorbent follows a Langmuir adsorption isotherm with maximum sorption capacity of 205 mg g−1 and 168 mg g−1 for Hg2+ and SeO 3 2−, respectively. Scanning electron microscopy-energy dispersive spectroscopy results show that the Se regions overlap exclusively with Zr-rich regions suggesting that SeO 3 2− adsorption depends entirely on the exposed UiO-66 surface. In addition, X-ray photoelectron spectroscopy spectra of Se 3d and Hg 4f showed the association of SeO 3 2− and Hg2+ on the UiO-66 and carbon surfaces, respectively. The sorbent could facilitate the development of a single process for the simultaneous removal of cationic Hg and anionic Se as well as other similar ionic metals with opposite charges from aqueous media. Image 1 • A UiO-66 and activated carbon composite sorbent is synthesized and characterized. • Adsorption experiments indicates that the sorbent removes dissolved Hg2+ and SeO 3 2- effectively. • Langmuir isotherm best describes the adsorption of Hg2+ and SeO 3 2- to the composite sorbent. • The adsorption of SeO 3 2- is localized to UiO-66 while Hg2+ adsorption is not site specific. [ABSTRACT FROM AUTHOR]