Coherent control of single spins in silicon carbide at room temperature

Spins in solids are cornerstone elements of quantum spintronics1. Leading contenders such as defects in diamond2–5, or individual phosphorous dopants in silicon6 have shown spectacular progress but either miss established nanotechnology or an efficient spin-photon interface. Silicon carbide (SiC) combines the strength of both systems5: It has a large bandgap with deep defects7–9 and benefits from mature fabrication techniques10–12. Here we report the characterization of photoluminescence and optical spin polarization from single silicon vacancies in SiC, and demonstrate that single spins can be addressed at room temperature. We show coherent control of a single defect spin and find long spin coherence time under ambient conditions. Our study provides evidence that SiC is a promising system for atomic- scale spintronics and quantum technology

Structural Attributes and Photodynamics of Visible Spectrum Quantum Emitters in Hexagonal Boron Nitride

Newly discovered van der Waals materials like MoS2, WSe2, hexagonal boron nitride (h-BN), and recently C2N have sparked intensive research to unveil the quantum behavior associated with their 2D structure. Of great interest are 2D materials that host single quantum emitters. h-BN, with a band gap of 5.95 eV, has been shown to host single quantum emitters which are stable at room temperature in the UV and visible spectral range. In this paper we investigate correlations between h-BN structural features and emitter location from bulk down to the monolayer at room temperature. We demonstrate that chemical etching and ion irradiation can generate emitters in h-BN. We analyze the emitters' spectral features and show that they are dominated by the interaction of their electronic transition with a single Raman active mode of h-BN. Photodynamics analysis reveals diverse rates between the electronic states of the emitter. The emitters show excellent photo stability even under ambient conditions and in monolayers. Comparing the excitation polarization between different emitters unveils a connection between defect orientation and the h-BN hexagonal structure. The sharp spectral features, color diversity, room-temperature stability, long-lived metastable states, ease of fabrication, proximity of the emitters to the environment, outstanding chemical stability, and biocompatibility of h-BN provide a completely new class of systems that can be used for sensing and quantum photonics applications

Single-Shot Electron Imaging of Dopant-Induced Nanoplasmas

We present single-shot electron velocity-map images of nanoplasmas generated from doped helium nanodroplets and neon clusters by intense near-infrared and mid-infrared laser pulses. We report a large variety of signal types, most crucially depending on the cluster size. The common feature is a two-component distribution for each single-cluster event: a bright inner part with nearly circular shape corresponding to electron energies up to a few eV, surrounded by an extended background of more energetic electrons. The total counts and energy of the electrons in the inner part are strongly correlated and follow a simple power-law dependence. Deviations from the circular shape of the inner electrons observed for neon clusters and large helium nanodroplets indicate non-spherical shapes of the neutral clusters. The dependence of the measured electron energies on the extraction voltage of the spectrometer indicates that the evolution of the nanoplasma is significantly affected by the presence of an external electric field. This conjecture is confirmed by molecular dynamics simulations, which reproduce the salient features of the experimental electron spectra.The authors are grateful for financial support from the Deutsche Forschungsgemeinschaft (DFG) within the project MU 2347/12-1 and STI 125/22-2 in the frame of the Priority Programme 1840 ‘Quantum Dynamics in Tailored Intense Fields’, from the Carlsberg Foundation and the SPARC Programme, MHRD, India. The ELI-ALPS Project (GINOP-2.3.6-15-2015-00001) is supported by the European Union and co-financed by the European Regional Development Fund. AH is grateful for financial support from the Basque Government (Project Reference No. IT1254-19) and from the Spanish Ministerio de Economia y Competividad (Reference No. CTQ2015-67660-P). Computational and manpower support provided by IZO-SGI SG Iker of UPV/EHU and European funding (EDRF and ESF) is gratefully acknowledged

Coordinatively Saturated Tris(oxazolinyl)borato Zinc Hydride-Catalyzed Cross Dehydrocoupling of Silanes and Alcohols

The four-coordinate zinc compound ToMZnH (1, ToM = tris(4,4-dimethyl-2-oxazolinyl)phenylborate) catalyzes selective alcoholysis of substituted hydrosilanes. The catalytic reaction of PhMeSiH2 and aliphatic alcohols favors the monodehydrocoupled product PhMeHSi–OR. With the aryl alcohol 3,5-C6H3Me2OH, the selectivity for mono(aryloxy)hydrosilane PhMeHSiOC6H3Me2 and bis(aryloxy)silane PhMeSi(OC6H3Me2)2 is controlled by relative reagent concentrations. Reactions of secondary organosilanes and diols provide cyclic bis(oxo)silacycloalkanes in high yield. The empirical rate law for the ToMZnH-catalyzed reaction of 3,5-dimethylphenol and PhMeSiH2 is −d[PhMeSiH2]/dt = k′obs[ToMZnH]1[3,5-C6H3Me2OH]0[PhMeSiH2]1 (determined at 96 °C) which indicates that Si–O bond formation is turnover-limiting in the presence of excess phenol

High catalytic activity of oriented 2.0.0 copper(I) oxide grown on graphene film

[EN] Metal oxide nanoparticles supported on graphene exhibit high catalytic activity for oxidation, reduction and coupling reactions. Here we show that pyrolysis at 900 C under inert atmosphere of copper(II) nitrate embedded in chitosan films affords 1.1.1 facet-oriented copper nanoplatelets supported on few-layered graphene. Oriented (1.1.1) copper nanoplatelets on graphene undergo spontaneous oxidation to render oriented (2.0.0) copper(I) oxide nanoplatelets on few-layered graphene. These films containing oriented copper(I) oxide exhibit as catalyst turnover numbers that can be three orders of magnitude higher for the Ullmann-type coupling, dehydrogenative coupling of dimethylphenylsilane with n-butanol and C–N cross-coupling than those of analogous unoriented graphene-supported copper(I) oxide nanoplatelets.Financial support by the Spanish Ministry of Economy and Competitiveness (Severo Ochoa and CTQ2012-32315) and Generalitat Valenciana (Prometeo 2013-019) is gratefully acknowledged. Partial financial support from European Union (Being Energy project) is also acknowledged. J.F.B. and I. E.-A. thank the Technical University of Valencia and the Spanish Ministry of Science for PhD scholarships, respectively. The authors are grateful to Mrs. Amparo Forneli for her assistance in the sample preparation and to Dr. Agouram Said from SCSIE, University of Valencia for the sample preparation and HRTEM characterization of samples. AD thanks University Grants Commission, New Delhi, for the award of Assistant Professorship under its Faculty Recharge Programme. AD also thanks Department of Science and Technology, India, for the financial support through Fast Track project (SB/FT/CS-166/2013) and the Generalidad Valenciana for financial aid supporting his stay at Valencia through the Prometeo programme. VP thanks UEFISCDI for financial support through PN-II-ID-PCE-2011-3-0060 project (275/2011).Primo Arnau, AM.; Esteve Adell, I.; Blandez Barradas, JF.; Amarajothi, D.; Alvaro Rodríguez, MM.; Candu, N.; Coman, SM.... (2015). High catalytic activity of oriented 2.0.0 copper(I) oxide grown on graphene film. Nature Communications. 6. https://doi.org/10.1038/ncomms9561S85616Huang, J. et al. Nanocomposites of size-controlled gold nanoparticles and graphene oxide: formation and applications in SERS and catalysis. Nanoscale 2, 2733–2738 (2010).Li, X., Wang, X., Song, S., Liu, D. & Zhang, H. Selectively deposited noble metal nanoparticles on fe3o4/graphene composites: stable, recyclable, and magnetically separable catalysts. Chem. Eur. J. 18, 7601–7760 (2012).Liang, Y. et al. Covalent hybrid of spinel manganese-cobalt oxide and graphene as advanced oxygen reduction electrocatalysts. J. Am. Chem. Soc. 134, 3517–3523 (2012).Ghanbarlou, H., Rowshanzamir, S., Kazeminasab, B. & Parnian, M. J. Non-precious metal nanoparticles supported on nitrogen-doped graphene as a promising catalyst for oxygen reduction reaction: synthesis, characterization and electrocatalytic performance. J. Power Sources 273, 981–989 (2015).Chu, H. et al. Ionic-liquid-assisted preparation of carbon nanotube-supported uniform noble metal nanoparticles and their enhanced catalytic performance. Adv. Funct. Mater. 20, 3747–3752 (2010).Ramulifho, T., Ozoemena, K. I., Modibedi, R. M., Jafta, C. J. & Mathe, M. K. Fast microwave-assisted solvothermal synthesis of metal nanoparticles (Pd, Ni, Sn) supported on sulfonated MWCNTs: Pd-based bimetallic catalysts for ethanol oxidation in alkaline medium. Electrochim. Acta 59, 310–320 (2012).Wang, Y., Zhao, Y., He, W., Yin, J. & Su, Y. Palladium nanoparticles supported on reduced graphene oxide: facile synthesis and highly efficient electrocatalytic performance for methanol oxidation. Thin Solid Films 544, 88–92 (2013).He, Y. et al. Metal nanoparticles supported graphene oxide 3D porous monoliths and their excellent catalytic activity. Mater. Chem. Phys. 134, 585–589 (2012).Li, Z. et al. One-pot synthesis of pd nanoparticle catalysts supported on n-doped carbon and application in the domino carbonylation. ACS Catal. 3, 839–845 (2013).Xiang, G., He, J., Li, T., Zhuang, J. & Wang, X. Rapid preparation of noble metal nanocrystals via facile coreduction with graphene oxide and their enhanced catalytic properties. Nanoscale 3, 3737–3742 (2011).Li, Z. et al. Experimental and DFT studies of gold nanoparticles supported on MgO(111) nano-sheets and their catalytic activity. Phys. Chem. Chem. Phys. 13, 2582–2589 (2011).Ding, M., Tang, Y. & Star, A. Understanding interfaces in metal-graphitic hybrid nanostructures. J. Phys. Chem. Lett. 4, 147–160 (2013).Wildgoose, G. G., Banks, C. E. & Compton, R. G. Metal nanoparticles and related materials supported on carbon nanotubes: methods and applications. Small 2, 182–193 (2006).Blandez, J. F., Primo, A., Asiri, A. M., Álvaro, M. & García, H. Copper nanoparticles supported on doped graphenes as catalyst for the dehydrogenative coupling of silanes and alcohols. Angew. Chem. Int. Ed. 53, 12581–12586 (2014).Yang, M. Q., Zhang, N., Pagliaro, M. & Xu, Y. J. Artificial photosynthesis over graphene-semiconductor composites. Are we getting better? Chem. Soc. Rev. 43, 8240–8254 (2014).Zhang, N., Zhang, Y. & Xu, Y. J. Recent progress on graphene-based photocatalysts: current status and future perspectives. Nanoscale 4, 5792–5813 (2012).Parga, A. L. V. de., Ha nacido una estrella. El grafeno. An. Quím. 107, 213–220 (2011).Rao, C. N. R., Sood, A. K., Subrahmanyam, K. S. & Govindaraj, A. Graphene: the new two-dimensional nanomaterial. Angew. Chem. Int. Ed. 48, 7752–7777 (2009).Sun, T. et al. Facile and green synthesis of palladium nanoparticles-graphene-carbon nanotube material with high catalytic activity. Nature 3, 1–6 (2013).Yoo, E. et al. Enhanced electrocatalytic activity of Pt subnanoclusters on graphene nanosheet surface. Nano Lett. 9, 2255–2259 (2009).Jin, X. et al. Lattice-matched bimetallic CuPd-graphene nanocatalysts for facile conversion of biomass-derived polyols to chemicals. ACS Nano 7, 1309–1316 (2013).Hong, C. et al. Graphene oxide stabilized Cu2O for shape selective nanocatalysis. J. Mater. Chem. A 2, 7147–7151 (2014).Reina, A. et al. Large area, few-layer graphene films on arbitrary substrates by chemical vapor deposition. Nano Lett. 9, 30–35 (2008).Wei, D. et al. Synthesis of N-doped graphene by chemical vapor deposition and its electrical properties. Nano Lett. 9, 1752–1758 (2009).Kim, K. S. et al. Large-scale pattern growth of graphene films for stretchable transparent electrodes. Nature 457, 706–710 (2009).Li, X. et al. Large-area graphene single crystals grown by low-pressure chemical vapor deposition of methane on copper. J. Am. Chem. Soc. 133, 2816–2819 (2011).Mattevi, C., Kima, H. & Chhowalla, M. A review of chemical vapour deposition of graphene on copper. J. Mater. Chem. 21, 3324–3334 (2010).Liu, W., Li, H., Xu, C., Khatami, Y. & Banerjee, K. Synthesis of high-quality monolayer and bilayer graphene on copper using chemical vapor deposition. Carbon 49, 4122–4130 (2011).Losurdo, M., Giangregorio, M. M., Capezzuto, P. & Bruno, G. Graphene CVD growth on copper and nickel: role of hydrogen in kinetics and structure. Phys. Chem. Chem. Phys. 13, 20836–20843 (2011).Gao, L., Guest, J. R. & Guisinguer, N. P. Epitaxial graphene on Cu (111). Nano Lett. 10, 3512–3516 (2010).Zhao, L. et al. Influence of copper crystal surface on the growth of large area monolayer graphene. Solid State Commun. 151, 509–513 (2011).Wood, J. D., Schmucker, S. W., Lyons, A. S., Pop, E. & Lyding, J. W. Effects of polycrystalline Cu substrate on graphene growth by chemical vapor deposition. Nano Lett. 11, 4547–4554 (2011).Primo, A., Atienzar, P., Sanchez, E., Delgado, J. M. & Garcia, H. From biomass wastes to large-area, high-quality, N-doped graphene: catalyst-free carbonization of chitosan coatings on arbitrary substrates. Chem. Commun. 48, 9254–9256 (2012).Primo, A., Sánchez, E., Delgado, J. M. & García, H. High-yield production of N-doped graphitic platelets by aqueous exfoliation of pyrolyzed chitosan. Carbon 68, 777–783 (2014).Primo, A., Forneli, A., Corma, A. & García, H. From biomass wastes to highly efficient CO2 adsorbents: graphitisation of chitosan and alginate biopolymers. ChemSusChem. 5, 2207–2214 (2012).Ravi Kumar, M. N. V. A review of chitin and chitosan applications. React. Funct. Polym. 46, 1–27 (2000).Rinaudo, M. Chitin and chitosan: properties and applications. Prog. Polym. Sci. 31, 603–632 (2006).Rinaudo, M. Main properties and current applications of some polysaccharides as biomaterials. Polym. Int. 57, 397–430 (2008).Latorre-Sanchez, M. et al. The synthesis of a hybrid graphene-nickel/manganese mixed oxide and its performance in lithium-ion batteries. Carbon 50, 518–525 (2012).Park, B. K. et al. Synthesis and size control of monodisperse copper nanoparticles by polyol method. J. Colloid Interface Sci. 311, 417–424 (2007).Lavorato, C., Primo, A., Molinari, R. & Garcia, H. Natural alginate as a graphene precursor and template in the synthesis of nanoparticulate ceria/graphene water oxidation photocatalysts. ACS Catal. 4, 497–504 (2014).Wu, S. et al. Electrochemical deposition of Cl-doped n-type Cu2O on reduced graphene oxide electrodes. J. Mater. Chem. 21, 3467–3470 (2011).Jiang, L. et al. Surface-enhanced Raman scattering spectra of adsorbates on Cu2O nanospheres: charge-transfer and electromagnetic enhancement. Nanoscale 5, 2784–2789 (2013).Sridhara Rao, D. V., Muraleedharan, K. & Humphreys, C. J. Microscopy Science, Technology, Applications and Education Vol. 2, 1232–1244Formatex, Badajos (2011).Lewin, A. H. & Cohen, T. The mechanism of the Ullman reaction. Detection of an organocopper intermediate. Tetrahedron Lett. 6, 4531–4536 (1965).Hassan, J., Sévignon, M., Gozzi, C., Schulz, E. & Lemaire, M. Aryl-aryl bond formation one century after the discovery of the Ullmann reaction. Chem. Rev. 102, 1359–1469 (2002).Ma, D., Cai, Q. & Zhang, H. Mild method for Ullman coupling reaction of amines and aryl halides. Org. Lett. 5, 2453–2455 (2003).Li, Y., Gao, W., Ci, L., Wang, C. & Ajayan, P. M. Catalytic performance of Pt nanoparticles on reduced graphene oxide for methanol electro-oxidation. Carbon 48, 1124–1130 (2010).Ong, W.-J., Tan, L.-L., Chai, S.-P. & Yong, S.-T. Heterojunction engineering of graphitic carbon nitride (g-C3N4) via Pt loading with improved daylight-induced photocatalytic reduction of carbon dioxide to methane. Dalton Trans. 44, 1249–1257 (2015).Luo, C., Zhang, Y., Zeng, X., Zeng, Y. & Wang, Y. The role of poly(ethylene glycol) in the formation of silver nanoparticles. J. Colloid Interface Sci. 288, 444–448 (2005).Wu, S.-H. & Chen, D.-H. Synthesis and characterization of nickel nanoparticles by hydrazine reduction in ethylene glycol. J. Colloid Interface Sci. 259, 282–286 (2003).Hou, Z., Theyssen, N., Brinkmann, A. & Leitner, W. Biphasic aerobic oxidation of alcohols catalyzed by poly(ethylene glycol)-stabilized palladium nanoparticles in supercritical carbon dioxide. Angew. Chem. Int. Ed. 117, 1370–1373 (2005).Dhakshinamoorthy, A., Navalon, S., Sempere, D., Alvaro, M. & Garcia, H. Reduction of alkenes catalyzed by copper nanoparticles supported on diamond nanoparticles. Chem. Commun. 49, 2359–2361 (2013).Ito, H., Watanabe, A. & Sawamura, M. Versatile dehydrogenative alcohol silylation catalyzed by Cu (I)-phosphine complex. Org. Lett. 7, 1869–1871 (2005).Rendler, S. et al. Stereoselective alcohol silylation by dehydrogenative Si-O coupling: scope, limitations, and mechanism of the Cu-H-catalyzed non-enzimatic kinetic resolution with silicon-stereogenic silanes. Chem. Eur. J. 14, 11512–11528 (2008).Cristau, H. J., Cellier, P. P., Spindler, J. F. & Taillefer, M. Highly efficient and mild copper-catalyzed N- and C-arylations with aryl bromides and iodides. Chemistry 10, 5607–5622 (2004).Shafir, A. & Buchwald, S. L. Highly selective room-temperature copper-catalyzed C-N coupling reactions. J. Am. Chem. Soc. 128, 8742–8743 (2006)