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Xin Hai, Zhiyong Guo, Xin Lin, Xuwei Chen, Jian-Hua Wang
A fluorescent probe TPA@GQDs is fabricated by the conjugation of terephthalic acid (TPA) on the surface of graphene quantum dots (GQDs). The TPA@GQDs probe not only owns favorable dispersibility, but also exhibits excellent fluorescence stability over wide pH range and high ionic strength, and favorable anti-photobleaching ability. The great fluorescence enhancement of TPA@GQDs induced by the reaction between TPA and hydroxyl radical makes the TPA@GQDs a powerful probe for the sensitive assay of hydroxyl radical, giving rise to a detection limit low down to 12 nmol L-1...
January 19, 2018: ACS Applied Materials & Interfaces
Jing Zeng, Ke-Qiu Chen
Although a lot of theoretical studies have designed perfect spin filters using inorganic/organic/organometallic materials, their fabrication methods are not experimentally feasible. This dilemma could be solved by a recent experiment, where porphyrins have been covalently coupled to graphene edges in a precise manner (Y. He et al., Nat. Chem., 2017, 9, 33-38). In particular, experimental results confirmed that the intrinsic features of porphyrins for metallation are preserved after dehydrogenative coupling to graphene edges, paving the way for realizing synthesizable spintronic devices...
January 19, 2018: Physical Chemistry Chemical Physics: PCCP
Fen Li, Jijun Zhao
One of the key issues in lithium sulfur batteries is the fast capacity fade induced by the lithium polysulfide (LiPS) migration. Hence, a series of three-dimensional (3D) porous SiC materials with active sp2 Si atoms have been designed for lithium polysulfide entrapping in Li-S batteries. The ZGM-SiC-1 and AGM-SiC-3 have been confirmed to be thermodynamically and dynamically stable from the formation energy and phonon dispersion spectrum, meanwhile showing good mechanical properties. The moderate band gaps suggest fast electron transport during the charge-discharge cycles of the Li-S batteries, especially in ZGM-SiC-1...
January 19, 2018: Physical Chemistry Chemical Physics: PCCP
Zhao Huang, Shuaifeng Li, Xin Liu, Degang Zhao, Lei Ye, Xuefeng Zhu, Jianfeng Zang
Optical interface states exhibit promising applications in nonlinear photonics, low-threshold lasing, and surface-wave assisted sensing. However, the further application of interface states in configurable optics is hindered by their limited tunability. Here, we demonstrate a new approach to generate dynamically tunable and angle-resolved interface states using graphene-embedded photonic crystal (GPC) heterostructure device. By combining the GPC structure design with in situ electric doping of graphene, a continuously tunable interface state can be obtained and its tuning range is as wide as the full bandgap...
January 19, 2018: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Xuewu Ou, Yanzi Yu, Ruizhe Wu, Abhishek Tyagi, Minghao Zhuang, Yao Ding, Irfan Haider Abidi, Heng-An Wu, Feng-Chao Wang, Zhengtang Luo
"Shuttle effect" of lithium polysulfides (LiPS) leads to poor performance and short cycle life of Li-S battery, thus limiting their practical application. We demonstrate here that after coating polypropylene (PP) separator with a continuous monolayer graphene, the "shuttle effect" can be significantly suppressed by limiting the passage of long chain LiPS. The graphene/PP separator can be further modified by sealing the big holes or pores on graphene with in situ polymerized nylon-66, via an interfacial polymerization reaction between diamine and adipoyl chloride supplied by the aqueous and oil phase, respectively from each side of the membrane...
January 19, 2018: ACS Applied Materials & Interfaces
Bin Wang, Jaegeon Ryu, Sungho Choi, Gyujin Song, Dongki Hong, Chihyun Hwang, Xiong Chen, Bo Wang, Wei Li, Hyun-Kon Song, Soojin Park, Rodney S Ruoff
We show that a high energy density can be achieved in a practical manner with freestanding electrodes without using conductive carbon, binders, and current collectors. We made and used a folded graphene composite electrode designed for a high areal capacity anode. The traditional thick graphene composite electrode, such as made by filtering graphene oxide to create a thin film and reducing it such as through chemical or thermal methods, has sluggish reaction kinetics. Instead, we have made and tested a thin composite film electrode that was folded several times using a water-assisted method; it provides a continuous electron transport path in the fold regions and introduces more channels between the folded layers, which significantly enhances the electron/ion transport kinetics...
January 19, 2018: ACS Nano
Gang Wang, Qinglei Guo, Da Chen, Zhiduo Liu, Xiaohu Zheng, Anli Xu, Siwei Yang, Guqiao Ding
Recently, the biomass "bottom-up" approach for the synthesis of graphene quantum dots have attracted broad interest because of the outstanding features, including low-cost, rapid and environmentally friendly nature. However, the low crystalline quality of products, substitutional doping with heteroatoms in lattice and ambiguous reaction mechanism strongly challenge the further development of this technique. Herein, we proposed a facile and effective strategy to prepare controllable sulfur (S) doping in graphene quantum dots, occurring in a lattice substitution manner, by hydrothermal treatment of durian with platinum catalyst...
January 19, 2018: ACS Applied Materials & Interfaces
Zahra Mofidi, Parviz Norouzi, Masumeh Sajadian, Mohammad Reza Ganjali
A novel, simple and inexpensive analytical technique based on flat sheet supported liquid membrane microextraction coupled with fast Fourier transform stripping cyclic voltammetry on a reduced graphene oxide carbon paste electrode was used for the extraction and online determination of diclofenac in whole blood. First, diclofenac was extracted from blood samples using a polytetrafluoroethylene membrane impregnated with 1-octanol and then into an acceptor solution, subsequently it was oxidized on a carbon paste electrode modified with reduced graphene oxide nano-sheets...
January 19, 2018: Journal of Separation Science
Saheed Bukola, Ying Liang, Carol Korzeniewski, Joel Harris, Stephen Creager
Ion current densities near 1 A cm-2 at modest bias voltages (< 200 mV) are reported for proton and deuteron transmission across single-layer graphene in polyelectrolyte-membrane (PEM)-style hydrogen pump cells. The graphene is sandwiched between two Nafion membranes and covers the entire area between two platinum-carbon electrodes, such that proton transfer is forced to occur through the graphene layer. Raman spectroscopy confirms that buried graphene layers are single-layer and relatively free of defects following the hot-press procedure used to make the sandwich structures...
January 19, 2018: Journal of the American Chemical Society
Jing Cao, Binghui Wu, Ruihao Chen, Youyunqi Wu, Yong Hui, Bing-Wei Mao, Nanfeng Zheng
The power conversion efficiency of perovskite solar cells (PSCs) has ascended from 3.8% to 22.1% in recent years. ZnO has been well-documented as an excellent electron-transport material. However, the poor chemical compatibility between ZnO and organo-metal halide perovskite makes it highly challenging to obtain highly efficient and stable PSCs using ZnO as the electron-transport layer. It is demonstrated in this work that the surface passivation of ZnO by a thin layer of MgO and protonated ethanolamine (EA) readily makes ZnO as a very promising electron-transporting material for creating hysteresis-free, efficient, and stable PSCs...
January 19, 2018: Advanced Materials
Montserrat Manadé, Francesc Viñes, Adrià Gil, Francesc Illas
The attachment of H2 to the full set of transition metal (TM) adatoms supported on graphene is studied by using density functional theory. Methodology validation calculations on the interactions of H2 with benzene and graphene show that any of the vdW corrections under study, the Grimme D2, D3, D3 with Becke-Jonson damping (D3BJ), and Tkatchenko-Scheffler methods, applied on the PBE functional, are similarly accurate in describing such subtle interactions, with an accuracy of almost 2 kJ mol-1 compared to experiments...
January 19, 2018: Physical Chemistry Chemical Physics: PCCP
D Meléndrez, T Jowitt, M Iliut, A F Verre, S Goodwin, A Vijayaraghavan
We report on the adsorption dynamics of phospholipid membranes on graphene-coated substrates using the quartz crystal microbalance with dissipation monitoring (QCM-D) technique. We compare the lipid vesicle interaction and membrane formation on gold and silicon dioxide QCM crystal surfaces with their graphene oxide (GO) and reduced (r)GO coated counterparts, and report on the different lipid structures obtained. We establish graphene derivative coatings as support surfaces with tuneable hydrophobicity for the formation of controllable lipid structures...
January 19, 2018: Nanoscale
Kehua Zhong, Yanmin Yang, Jian-Min Zhang, Guigui Xu, Zhigao Huang
We have investigated the effects of graphene intercalation on dielectric reliability of HfO2 for Ni/Gr/HfO2 interfaces, and the effects of graphene intercalation and interfacial atom vacancy on the effective work function (EWF) of Ni/Gr/HfO2 interfaces using first-principle calculation based on density functional theory. The calculated results indicate that graphene intercalation can improve dielectric reliability of HfO2 dielectric even for the interfaces having interfacial oxygen vacancy or a small amount carbon vacancy...
January 18, 2018: Scientific Reports
Sourav P Mukherjee, Olesja Bondarenko, Pekka Kohonen, Fernando T Andón, Táňa Brzicová, Isabel Gessner, Sanjay Mathur, Massimo Bottini, Paolo Calligari, Lorenzo Stella, Elena Kisin, Anna Shvedova, Reija Autio, Heli Salminen-Mankonen, Riitta Lahesmaa, Bengt Fadeel
Carbon-based nanomaterials including carbon nanotubes (CNTs) have been shown to trigger inflammation. However, how these materials are 'sensed' by immune cells is not known. Here we compared the effects of two carbon-based nanomaterials, single-walled CNTs (SWCNTs) and graphene oxide (GO), on primary human monocyte-derived macrophages. Genome-wide transcriptomics assessment was performed at sub-cytotoxic doses. Pathway analysis of the microarray data revealed pronounced effects on chemokine-encoding genes in macrophages exposed to SWCNTs, but not in response to GO, and these results were validated by multiplex array-based cytokine and chemokine profiling...
January 18, 2018: Scientific Reports
Kun-Yi Andrew Lin, Hongta Yang, Fu-Kong Hsu
  To investigate effects of modification of MOFs on removal of acid dyes via adsorption and photodegradation, zirconium-based MOF, UiO-66, and its derivatives were synthesized. UiO-66 derivatives were prepared by using amine (NH2)-containing ligand and incorporating carbon nanotubes (CNTs) and reduced graphene oxide (RGO). During the synthesis UiO-66-NH2, UiO-66-CNT and UiO-66-RGO, were obtained, respectively. While UiO-66-NH2 showed the enhanced adsorption capacity for acid dyes owing to the electrostatic attraction, CNTs were found to be the most effective addition to enhance the adsorption of acid dyes...
February 1, 2018: Water Environment Research: a Research Publication of the Water Environment Federation
M Ruiz-Garcia, L L Bonilla, A Prados
We analyze a one-dimensional spin-string model, in which string oscillators are linearly coupled to their two nearest neighbors and to Ising spins representing internal degrees of freedom. String-spin coupling induces a long-range ferromagnetic interaction among spins that competes with a spin-spin antiferromagnetic coupling. As a consequence, the complex phase diagram of the system exhibits different flat rippled and buckled states, with first or second order transition lines between states. This complexity translates to the two-dimensional version of the model, whose numerical solution has been recently used to explain qualitatively the rippled to buckled transition observed in scanning tunneling microscopy experiments with suspended graphene sheets...
December 2017: Physical Review. E
Rajratan Basu
A small quantity of monolayer graphene flakes is doped in a nematic liquid crystal (LC), and the effective polar anchoring strength coefficient between the LC and the alignment substrate is found to increase by an order of magnitude. The hexagonal pattern of graphene can interact with the LC's benzene rings via π-π electron stacking, enabling the LC to anchor to the graphene surface homogeneously (i.e., planar anchoring). When the LC cell is filled with the graphene-doped LC, some graphene flakes are preferentially attached to the alignment layer and modify the substrate's anchoring property...
July 2017: Physical Review. E
Rajratan Basu, Samuel A Shalov
In a conventional liquid crystal (LC) cell, polyimide layers are used to align the LC homogeneously in the cell, and transmissive indium tin oxide (ITO) electrodes are used to apply the electric field to reorient the LC along the field. It is experimentally presented here that monolayer graphene films on the two glass substrates can function concurrently as the LC aligning layers and the transparent electrodes to fabricate an LC cell, without using the conventional polyimide and ITO substrates. This replacement can effectively decrease the thickness of all the alignment layers and electrodes from about 100 nm to less than 1 nm...
July 2017: Physical Review. E
Emily R Russell, Rastko Sknepnek, Mark Bowick
Two-dimensional crystalline membranes have recently been realized experimentally in systems such as graphene and molybdenum disulfide, sparking a resurgence in interest in their statistical properties. Thermal fluctuations can significantly affect the effective mechanical properties of properly thermalized membranes, renormalizing both bending rigidity and elastic moduli so that in particular they become stiffer to bending than their bare bending rigidity would suggest. We use molecular dynamics simulations to examine how the mechanical behavior of thermalized two-dimensional clamped ribbons (cantilevers) depends on their precise topology and geometry...
July 2017: Physical Review. E
Masumeh Foroutan, Mehdi Darvishi, S Mahmood Fatemi
The positioning, adsorption, and movement of water on substrates is dependent upon the chemical nature and arrangement of the atoms of the surface. Therefore the behavior of water molecules on a substrate is a reflection of properties of the surface. Based on this premise, graphene and gold substrates were chosen to study this subject from a molecular perspective. In this work, the structural and dynamical behaviors of a water nanodroplet on Au (100) and the graphene interfaces have been studied by molecular dynamics simulation...
September 2017: Physical Review. E
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