Search

Abstract Multi-functionalized magnetic graphene was prepared by surface-initiated initiators for continuous activator regeneration atom transfer radical polymerization (ICAR ATRP) mediated by polydopamine chemistry. The obtained multi-functionalized magnetic graphene was used as an adsorbent for application in adsorption and speciation of arsenic. Adsorption kinetics and isotherms of arsenic were investigated by batch adsorption experiments. The adsorbent displayed simultaneous or selective removal ability for As(III) and As(V) within different pH ranges. The adsorption of both As(III) and As(V) agreed well with the Freundlich isotherm model, and they were effectively adsorbed through chelation and electrostatic interaction, respectively. Moreover, the functionalized magnetic graphene was examined as a column packing material for speciation analysis of arsenic using solid phase extraction technique. As(III) and As(V) could be effectively separated through a sequential elution strategy. An alkaline solution was firstly employed to selectively elute As(V), and then an acidic solution was utilized to elute As(III). The developed adsorbent in the present study was successfully applied to the determination of As(III) and As(V) in natural and environmental water samples with satisfactory results. Graphical abstract Unlabelled Image Highlights • Multi-functionalized magnetic graphene was prepared and used as an adsorbent. • As(III) and As(V) could be simultaneously or selectively removed by the adsorbent. • As(III) and As(V) could be separated through a sequential elution strategy. [ABSTRACT FROM AUTHOR]

Graphene aerogels have been extensively studied in water treatment and oil remediation. We report a mild and green method to prepare a 3D-columnar graphene aerogel. The aerogel was synthesized by using polyvinyl alcohol (PVA) and stearic acid (SA) as crosslinking agents to construct a framework of reduced graphene oxide (RGO). The interaction between PVA, SA, and stacked RGO sheets created a mechanically very robust aerogel. The aerogel possesses ultra-light performance with the destiny ranging from 4.9 to 10 mg cm −3 . The aerogel also demonstrated ultrafast oil absorption, good fire-resistance, and excellent mechanical properties. The adsorptive capacities are in the range of 105–250 times of its original weight for various organic liquids after the absorption. The aerogel also exhibited a strong durability and reusability, and after ten cycles of absorbing-squeezing, the adsorptive capacity is nearly unchanged, indicating potential application in practical oil remediation. [ABSTRACT FROM AUTHOR]

The NiCo 2 O 4 -anchored reduced graphene oxide (NiCo 2 O 4 @rGO) nanoplates have been synthesized by a facile self-assembly process. The morphology, crystalline structure and electrochemical performance of the materials have been investigated comprehensively. The results of SEM manifest that NiCo 2 O 4 particles have been densely anchored on the surface of rGO with a mesoporous structure, and the morphology is tunable via altering concentration of urea during the preparation process. Due to the high ratio of NiCo 2 O 4 in the composite and the plate structure, the electrochemical performance of as-prepared material has been greatly improved. When evaluated as anode materials in lithium ion batteries (LIBs), the as-prepared NiCo 2 O 4 @rGO nanocomposite delivers a reversible capacity of 994 mAh g −1 at a current density of 200 mA g −1 with outstanding rate capability, revealing that it could be a promising anode for LIBs. [ABSTRACT FROM AUTHOR]

Graphene directly grown on an 4H-SiC (0 0 0 1) substrate by chemical vapor deposition was studied: it was shown that Si evaporation process is not completely halted during graphene growth when T G  ≥ 1400 °C, the SiC substrate decomposes at the position of graphene coverage. AFM and Raman spectrum results reveal that carbon concentration significantly influences graphene growth rate and morphology/structure. It is found that the quality of graphene film depends on the growth temperature and the flow of carbon source. We develop a new gradient growth method to produce a feasible graphene material for electronic devices. Graphene grown by this method has a flat-morphology structure, low wrinkle density, high crystal quality, good uniformity, and outstanding electrical transport properties. Nitrogen doping has an n-type doping effect on graphene carrier concentration. The main component of nitrogen-bond type is the graphitic configuration. The graphene material with nitrogen doping reaches a record mobility of 9010 cm 2 /V·s by room temperature Hall effect measurement, indicating graphene grown by gradient method with suitable nitrogen doping could yield a high quality film comparable to that by traditional method. [ABSTRACT FROM AUTHOR]

[Display omitted] • A sandwich-like composite, S-V 2 O 5 /rGO core–shell structure, is synthesized. • The sandwich-like S-V 2 O 5 /rGO exhibits improved Zn2+ storage. • S-V 2 O 5 /rGO delivers a high capacity up to 610 mAh·g−1 at 0.1 A·g−1. The synthesis of V 2 O 5 with novel architectures for aqueous Zn-ion batteries (AZIBs) has been developed great advances but is still a huge challenge. Herein, a sandwich-like composite, sulfur-doped V 2 O 5 /reduced graphene oxide/sulfur-doped V 2 O 5 (denoted as S-V 2 O 5 /rGO) core–shell structure, is synthesized by the combination of hydrothermal and calcining processes, and this material exhibits improved electrochemical properties for Zn2+ storage. The rGO in the middle and S-dopant facilitate ion diffusion and electron transport and make the material easier for the electrolyte to enter, resulting in outstanding Zn2+ storage of S-V 2 O 5 /rGO. The Zn//S-V 2 O 5 /rGO battery delivers a high capacity up to 610 mAh·g−1 at 0.1 A·g−1 and stable cycle performance. The battery also delivers excellent rate stability with about 467, 458, 454, 447 and 442 mAh·g−1 at 0.4, 0.8, 1.0, 1.5 and 2.0 A·g−1. The energy densities are achieved as high as 333 Wh·kg−1 at 286 W·kg−1 and 306 Wh·kg−1 at 1392 W·kg−1 based on the mass of S-V 2 O 5 /rGO. The results prove that this sandwich-like structure combination with S-dopant can improve the electrical conductivity and facilitate the migration of Zn2+ and electrons, leading to fast redox reaction kinetics. These findings provide a novel strategy for designing novel V-based architectures for aqueous multivalent ions batteries. [ABSTRACT FROM AUTHOR]

Modulating the thickness of graphene, interlayer distance and external electric-field for graphene/Ga 2 O 3 are easy to eliminate the tunneling and Schottky barrier, and then to realize high performance β-Ga 2 O 3 optoelectronic. • A small n-type Schottky barrier height (SBH n) exists in the graphene/Ga 2 O 3 contact. • SBH n -to- SBH p transition can be realized by applying positive external E-field. • Three methods can realize the SBH n -to-Ohmic transition for graphene/Ga 2 O 3 interface. • The interfacial dipole and potential step are the main factors for the SBH. The ultra-wide-gap β-Ga 2 O 3 has been regarded as a promising material for next-generation power electronic and deep-ultraviolet (UV) photodetectors. Exploring a suitable electrode is vital for realizing high performance β-Ga 2 O 3 based nanodevices. Herein, the structural and contact properties of graphene/Ga 2 O 3 interfaces are tuned and investigated by using the first-principles calculations. Results show that the small n-type Schottky barrier of about 0.07 eV for the graphene/Ga 2 O 3 interface with weak interlayer interaction is irrespective of the interface stacking arrangement. Moreover, the intrinsic electronic property of Ga 2 O 3 is well preserved in the interface. More interestingly, the n-type Schottky barrier to Ohmic contact transition can be obtained by shorting the interlayer distance, or increasing the graphene layers or applying a negative external electric field for the interface. Moreover, applying a large positive external electric field can realize the p-type Schottky barrier to Ohmic contact transition for graphene/Ga 2 O 3 interface. These results are uncovered by analyzing the interfacial dipole and potential step of graphene/Ga 2 O 3 interface, and expected to enhance the application potential of graphene electrode in the β-Ga 2 O 3 based electronic and optoelectronic devices. [ABSTRACT FROM AUTHOR]

• Graphene quantum dots (GQDs) are used to modify the SnO 2 ETL in perovskite solar cells. • The GQDs increase the electronic coupling as well as energy levels matching between the perovskite and SnO 2 ETL. • The combination of SnO 2 :GQDs leads to a significant improvement of efficient charge carrier extraction and suppression of the charge recombination. • A high PCE of 21.1% is obtained, which is increased by 13.4% in comparison with the device based on the SnO 2 -only ETL (18.6%). In this work, Graphene quantum dots (GQDs) was decorated on the SnO 2 electron transport layers (ETLs) to boost the performance of perovskite solar cells (PSCs). The power conversion efficiency (PCE) of 21.1% was acquired with the combination of SnO 2 and GQDs. Compared with the SnO 2 -only ETL devices (18.6%), the PCE of SnO 2 /GQDs based devices is greatly enhanced in PCE by the value of 13.4% as well as in the stability. Investigation reveals that with the combination of SnO 2 and GQDs, the open circuit voltage (V OC) and the short circuit current density (J SC) could increase. Various advanced optical and electrical characterizations were carried out to explore the action mechanism of GQDs. The experimental results convinced that the introduction of GQDs leads to the better carrier transportation and extraction by increasing the electronic coupling and matching the energy levels between the perovskite and SnO 2 ETL. Also, the perovskite film quality deposited on the GQDs decorated SnO 2 ETL is better compared with the SnO 2 only. Furthermore, the device stability based on the GQDs modified SnO 2 is evidently improved contrast to the SnO 2 -only device. Its performance kept above 80% of initial value after 720 h storage. [ABSTRACT FROM AUTHOR]