Tailoring magnetism in silicon-doped zigzag graphene edges

Recently, the edges of single-layer graphene have been experimentally doped with silicon atoms by means of scanning transmission electron microscopy. In this work, density functional theory is applied to model and characterize a wide range of experimentally inspired silicon doped zigzag-type graphene edges. The thermodynamic stability is assessed and the electronic and magnetic properties of the most relevant edge configurations are unveiled. Importantly, we show that silicon doping of graphene edges can induce a reversion of the spin orientation on the adjacent carbon atoms, leading to novel magnetic properties with possible applications in the field of spintronics.A.U. gratefully acknowledges Eusko Jaurlaritza for his predoctoral grant. We thank the Provincial Council of Gipuzkoa (RED Gipuzkoa Next 2021-CIEN-000070-01), the Basque Department of Education (IT1254-19, PIBA2020-1-0014), the Spanish Ministry of Science and Innovation (PID2019-107338RB-C66, PID2020-114754GA-I00) and the European Union (EU) through Horizon 2020 (FET-Open project SPRING Grant No. 863098) for financial support. The authors thankfully acknowledge the computer resources at MareNostrum and the technical support provided by Barcelona Supercomputing Center (QHS-2021-3-0004). We also thank DIPC and SGI-IZOSGIker (UPV/EHU) for the generous allocation of computational resources

Second-Row Transition-Metal Doping of (ZniSi), i = 12, 16 Nanoclusters: Structural and Magnetic Properties

TM@ZniSi nanoclusters have been characterized by means of the Density Functional Theory, in which Transition Metal (TM) stands from Y to Cd, and i = 12 and 16. These two nanoclusters have been chosen owing to their highly spheroidal shape which allow for favored endohedral structures as compared to other nanoclusters. Doping with TM is chosen due to their magnetic properties. In similar cluster-assembled materials, these magnetic properties are related to the Transition Metal-Transition Metal (TM-TM) distances. At this point, endohedral doping presents a clear advantage over substitutional or exohedral doping, since in the cluster-assembled materials, these TM would occupy the well-fixed center of the cluster, providing in this way a better TM-TM distance control to experimentalists. In addition to endohedral compounds, surface structures and the TS’s connecting both isomers have been characterized. In this way the kinetic and thermal stability of endohedral nanoclusters is predicted. We anticipate that silver and cadmium endohedrally doped nanoclusters have the longest life-times. This is due to the weak interaction of these metals with the cage, in contrast to the remaining cases where the TM covalently bond to a region of the cage. The open-shell electronic structure of Ag provides magnetic properties to Ag@ZniSi clusters. Therefore, we have further characterized (Ag@Zn12S12)2 and (Ag@Zn16S16)2 dimers both in the ferromagnetic and antiferromagnetic state, in order to calculate the corresponding magnetic exchange coupling constant, J.This research was funded by Eusko Jaurlaritza (the Basque Government), and the Spanish Office for Scientific Research. The SGI/IZO-SGIker UPV/EHU (supported by Fondo Social Europeo and MCyT) is gratefully acknowledged for generous allocation of computational resources. JMM would like to thank Spanish Ministry of Science and Innovation for funding through a Ramon y Cajal fellow position (RYC 2008-03216). We thanks Elixabete Rezabal for cheerful discussion

Unraveling the effects of Fe and Mn promoters on the tungstated zirconia catalyst: A DFT study

Periodic DFT calculations are performed to unravel the effect of the incorporation of Fe and Mn into the tung-stated zirconia catalyst, (WO3)x/ZrO2 (x = 1,3), in their electronic, geometric, and catalytic properties. Our results suggest that both Mn and Fe have a proclivity to occupy the same positions and thus both metals will compete for the same adsorption sites. The addition of Fe or Mn slightly destabilizes the WO3 monomer while stabilizes the (WO3)3 trimer. Hence, medium size clusters, which are the most catalytically active species, will be more sinter resistant in the presence of the promoters, leading to catalysts with longer lifetimes. The computed deprotonation energies evidence that the overall Bronstead acidity is increased upon the addition of the dopant atoms. It is proposed that the metals lead to a reduction of WZ and induce a local spin density imbalance.The function as redox initiators of these metals is confirmed.This work is supported by grant PID2020-114754GA-I00 funded by MCIN/ AEI/10.13039/501100011033 and funding provided by Gobierno Vasco-Eusko Jaurlaritza (IT1254-19). We also thank DIPC and SGI-IZO-SGIker (UPV/EHU) for the generous allocation of computa-tional resources. The authors thankfully acknowledge also the computer resources at MareNostrum and the technical support provided by Bar-celona Supercomputing Center (QHS-2021-3-0004). The authors acknowledge the Instituto Politecnico Nacional for the financial support received through project SIP-20221590. J.I.R. thanks SIP-IPN for financial support (projects SIP20210100 and SIP20221613). K.G.M.C. thanks CONACYT-Mexico for the doctorate fellowship (CVU: 745592)

Role of dispersion interactions in Endohedral TM@(ZnS)12 structures

Role of dispersion interactions in Endohedral TM@(ZnS)(12) structures[EN] II−VI semiconducting materials are gaining attention due to their optoelectronic properties. Moreover, the addition of transition metals, TMs, might give them magnetic properties. The location and distance of the TM are crucial in determining such magnetic properties. In this work, we focus on small hollow (ZnS)12 nanoclusters doped with TMs. Because (ZnS)12 is a cage-like spheroid, the cavity inside the structure allows for the design of endohedral compounds resembling those of C60. Previous studies theoretically predicted that the first-row TM(ZnS)12 endohedral compounds were thermodynamically unstable compared to the surface compounds, where the TM atom is located at the surface of the cluster. The transition states connecting both structure families were calculated, and the estimated lifetimes of these compounds were predicted to be markedly small. However, in such works dispersion effects were not taken into account. Here, in order to check for the influence of dispersion on the possible stabilization of the desired TM(ZnS)12 endohedrally doped clusters, several functionals are tested and compare to MP2. It is found that the dispersion effects play a very important role in determining the location of the metals, especially in those TMs with the 4s3d shell half-filled or completely filled. In addition, a complete family of TM doped (ZnS)12 nanoclusters is explored using ab initio molecular dynamics simulations and local minima optimizations that could guide the experimental synthesis of such compounds. From the magnetic point of view, the Cr(7S)@(ZnS)12 compound is the most interesting case, since the endohedral isomer is predicted to be the global minimum. Moreover, molecular dynamics simulations show that when the Cr atom is located at the surface of the cluster, it spontaneously migrates toward the center of the cavity at room temperature.Financial support comes from Eusko Jaurlaritza through project IT1254-19. The authors are thankful for technical and human support provided by SGIker (UPV/EHU, ERDF, EU). E.J.I. acknowledges the support of the Ikerbasque Fellowship. E.R.C. acknowledges funding from the Juan de la Cierva program IJCI-2017-34658

Metal–Polymer Heterojunction in Colloidal-Phase Plasmonic Catalysis

[EN] Plasmonic catalysis in the colloidal phase requires robust surface ligands that prevent particles from aggregation in adverse chemical environments and allow carrier flow from reagents to nanoparticles. This work describes the use of a water-soluble conjugated polymer comprising a thiophene moiety as a surface ligand for gold nanoparticles to create a hybrid system that, under the action of visible light, drives the conversion of the biorelevant NAD+ to its highly energetic reduced form NADH. A combination of advanced microscopy techniques and numerical simulations revealed that the robust metal-polymer heterojunction, rich in sulfonate functional groups, directs the interaction of electron-donor molecules with the plasmonic photocatalyst. The tight binding of polymer to the gold surface precludes the need for conventional transition-metal surface cocatalysts, which were previously shown to be essential for photocatalytic NAD+ reduction but are known to hinder the optical properties of plasmonic nanocrystals. Moreover, computational studies indicated that the coating polymer fosters a closer interaction between the sacrificial electron-donor triethanolamine and the nanoparticles, thus enhancing the reactivity.This work was supported by grant PID2019-111772RB-I00 funded by MCIN/AEI/10.13039/501100011033 and grant IT 1254-19 funded by Basque Government. The authors acknowl- edge the financial support of the European Commission (EUSMI, Grant 731019). S.B. is grateful to the European Research Council (ERC-CoG-2019 815128). The authors acknowledge the contributions by Dr. Adrian Pedrazo Tardajos related to sample support and electron microscopy experiments