Mobility enhancement of CVD graphene by spatially correlated charges

The manuscript presents a strategy for enhancing the carrier mobility of single layer CVD graphene (CVD SLG) based on spatially correlated charges. Our Monte Carlo simulations, numerical modeling and the experimental results confirm that spatial correlation between defects with opposite charges can provide a means to control independently the carrier concentration and mobility of planar field effect transistors in which graphene is decorated with a layer of colloidal quantum dots (QDs). We show that the spatial correlation between electrically charged scattering centres close to the graphene/SiO2 interface and the localised charges in a QD layer can smooth out the electrostatic potential landscape, thus reducing scattering and enhancing the carrier mobility. The QD capping molecules influence the distribution and correlation of electrical charges in the vicinity of SLG and provide a means of tuning the carrier concentration and increasing the carrier mobility in graphene. These results represent a significant conceptual advance and provide a novel strategy for control of the electronic properties of 2D materials that could accelerate their utilization in optoelectronic devices

DDAB-assisted synthesis of iodine-rich CsPbI3 perovskite nanocrystals with improved stability in multiple environments

© 2020 The Royal Society of Chemistry. All-inorganic cesium lead halide perovskite (CsPbX3, X = Cl, Br, I) nanocrystals (NCs) have attracted considerable attention due to their tunable optical properties and high optical quantum yield. However, their stability in various environments, such as different solvents, high temperature and UV light, remains to be addressed to enable their exploitation in devices. Here, we report on the synthesis of all inorganic CsPbI3 perovskite nanocrystals capped with didodecyldimethylammonium bromide (DDAB). Monodispersed DDAB-capped CsPbI3 NCs have enhanced stability with respect to their morphological and optical properties compared to conventional oleic acid (OA)/oleylamine (OLA) capped nanocrystals. The DDAB-CsPbI3 NCs retain an optical quantum yield >80% for at least 60 days. The enhanced stability is explained by the binding of branched DDAB ligands to the NC surface, leading to the formation of a halogen-rich surface, as confirmed by X-ray photoelectron spectroscopy, with an iodine to lead atomic ratio of I : Pb = 4 : 1. These perovskites were used in light-emitting diodes (LEDs) and have a maximum external quantum efficiency (EQE) of 1.25% and a luminance of 468 cd m-2, and demonstrated improved operational performance. The enhanced stability of DDAB-CsPbI3 in the environments relevant for device processing and operation is relevant for their exploitation in optoelectronics

Cr2O3 nanoparticles boosting Cr–N–C for highly efficient electrocatalysis in acidic oxygen reduction reaction

Transition metal–nitrogen–carbon (M–N–C) catalysts have attracted significant attention for catalyzing oxygen reduction reactions (ORR). In this study, a porous Cr O @Cr–N–C catalyst with a small amount of Cr O nanoparticles loaded on the surface of Cr–N –C nanomaterials was prepared using synergistic heat treatment (SHT) method with zeolite imidazole frameworks (ZIFs) as precursors. TEM and spherical aberration-corrected TEM results demonstrated the presence of hollow morphologies, Cr O nanoparticles and atomic-level Cr distribution in Cr O @Cr–N–C. XPS, XRD and XAFS analysis indicated the coexistence of Cr O nanoparticles and Cr–N sites which were believed to act as active centers for ORR. In 0.1 M HClO , this material showed outstanding ORR catalytic activity with a half-wave potential of 0.78 V that was 40 mV higher than the traditional heat treatment derived Cr–N–C. It also revealed relatively low Tafel slope of 52.2 mV dec ; 4-electron pathway; remarkable stability and long-term durability. The improved ORR performance is mainly attributed to the synergy between Cr–N active center and Cr O nanoparticle. The SHT strategy reported here provides a new route to prepare highly efficient non-precious metal M−N–C catalysts with greater ORR activity and stability in acidic environments

Realization of Universal Quantum Gates with Spin-Qudits in Colloidal Quantum Dots

Hyperfine interactions in a single Mn-ion confined in a quantum dot (QD) are exploited to create a qudit, that is, a multilevel quantum-bit system, with well-defined, addressable, and robust set of spin states for the realization of universal quantum gates. An arbitrary superposition of states between selected hyperfine energy level pairs is generated and probed by using electron double resonance detected nuclear magnetic resonance (EDNMR). This enables the observation of Rabi oscillations and the experimental realization of NOT and √ SWAP universal quantum gates that are robust against decoherence. Our protocol for cyclical preparation, manipulation, and read-out of logic gates offers opportunities for the integration of qudits in scalable quantum circuit architectures beyond solid state electron spin qubits

Enhanced electrocatalytic oxygen reduction reaction for Fe-N4-C by the incorporation of Co nanoparticles

Oxygen reduction reaction (ORR) catalytic activity can be improved by means of enhancing the synergy between transition metals. In this work, a novel porous Fe-N4-C nanostructure containing uniformly dispersed Co nanoparticles (CoNPs) is prepared by an assisted thermal loading method. The as-prepared Co@Fe-N-C catalyst shows enhanced ORR activity with a half-wave potential (E1/2) of 0.92 V vs. RHE, which is much higher than those of the direct pyrolysis CoNP-free sample Fe-N-C (E1/2 = 0.85 V) and Pt/C (E1/2 = 0.90 V) in alkaline media. It exhibits remarkable stability with only a 10 mV decrease in E1/2 after 10 000 cycles and an outstanding long-term durability with 85% current remaining after 60 000 s. In acidic media, this catalyst exhibits catalytic activity with an E1/2 of 0.79 V, comparable to Pt/C (E1/2 = 0.82 V). X-ray absorption fine spectroscopy analysis revealed the presence of active centres of Fe-N4. Density functional theory calculations confirmed the strong synergy between CoNPs and Fe-N4 sites, providing a lower overpotential and beneficial electronic structure and a local coordination environment for the ORR. The incorporation of CoNPs on the surface of Fe-N4-C nanomaterials plays a key role in enhancing the ORR catalytic activity and stability, providing a new route to prepare efficient Pt-free ORR catalysts

New treatments in renal cancer: The AhR ligands

Kidney cancer rapidly acquires resistance to antiangiogenic agents, such as sunitinib, developing an aggressive migratory phenotype (facilitated by c-Metsignal transduction). The Aryl hydrocarbon receptor (AhR) has recently been postulated as a molecular target for cancer treatment. Currently, there are two antitumor agent AhR ligands, with activity against renal cancer, that have been tested clinically: aminoflavone (AFP 464, NSC710464) and the benzothiazole (5F 203) prodrug Phortress. Our studies investigated the action of AFP 464, the aminoflavone pro-drug currently used in clinical trials, and 5F 203 on renal cancer cells, specifically examining their effects on cell cycle progression, apoptosis and cell migration. Both compounds caused cell cycle arrest and apoptosis but only 5F 203 potently inhibited the migration of TK-10, Caki-1 and SN12C cells as well as the migration signal transduction cascade, involving c-Met signaling, in TK-10 cells. Current investigations are focused on the development of nano-delivery vehicles, apoferritin-encapsulated benzothiazoles 5F 203 and GW610, for the treatment of renal cancer. These compounds have shown improved antitumor effects against TK-10 cells in vitro at lower concentrations compared with a naked agent.Fil: Itkin, Boris. Gobierno de la Ciudad de Buenos Aires. Hospital General de Agudos "Juan A. Fernández"; ArgentinaFil: Breen, Alastair. University of Nottingham; Estados UnidosFil: Turyanska, Lyudmila. University of Nottingham; Estados UnidosFil: Sandes, Eduardo Omar. Universidad de Buenos Aires. Facultad de Medicina. Instituto de Oncología "Ángel H. Roffo"; ArgentinaFil: Bradshaw, Tracey D.. University of Nottingham; Estados UnidosFil: Loaiza Perez, Andrea Irene. Universidad de Buenos Aires. Facultad de Medicina. Instituto de Oncología "Ángel H. Roffo"; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay; Argentin

Synergistic heat treatment derived hollow-mesoporous-microporous Fe–N–C-SHT electrocatalyst for oxygen reduction reaction

© 2020 Exploring an economical and efficient oxygen reduction reaction (ORR) is an essential but challenging field of study. Metal–organic frameworks (MOFs) have emerged as promising candidates for the preparation of porous catalysts. Here we propose a synergistic heat treatment (SHT) method to synthesize Fe–N–C-SHT catalyst with hierarchical porous hollow structures via a simple carbonization method by the synergistic heating of ZIF-8-Fe (ZIF-8 doped with Fe) and ZIF-67 in a tube furnace. Fe–N–C-SHT catalyst displays efficient ORR activity (half-wave potential (Ehalf) = 0.88 V versus reversible hydrogen electrode (RHE) with a loading of 0.204 mgFe-N-C-SHTcm−2), which is superior to that of Fe–N–C synthesized using individual heat treatment (IHT) (Ehalf = 0.84 V) and Pt/C catalyst (Ehalf = 0.86 V). We achieve enhanced catalytic properties, enhanced methanol tolerance, and long-term durability of the Fe–N–C-SHT catalyst in alkaline electrolyte. The improved ORR activity is attributed to the synergistic effect of Fe doping and optimized SHT methodology, which led to the formation of a highly porous catalyst with numerous active sites. The developed SHT method presents a novel route to fabricate Fe–N–C catalysts with hollow-mesoporous-microporous structures and high performance in ORR

Defect-assisted high photoconductive UV-VIS gain in perovskite-decorated graphene transistors

Recent progress in the synthesis of high stability inorganic perovskite nanocrystals (NCs) has led to their increasing use in broadband photodetectors. These NCs are of particular interest for the UV range as they have the potential to extend the wavelength range of photodetectors based on traditional materials. Here we demonstrate a defect-assisted high photoconductive gain in graphene transistors decorated with all-inorganic caesium lead halide perovskite NCs. The photoconductive gain in the UV-VIS wavelength range arises from the charge transfer between the NCs and graphene and enables observation of high photoconductive gain of 106 A/W. This is accompanied by a giant hysteresis of the graphene resistance that is strongly dependent on electrostatic gating and temperature. Our data are well described by a phenomenological macroscopic model of the charge transfer from bound states in the NCs into the graphene layer, providing a useful tool for the design of high-photoresponsivity perovskite/graphene transistors