Platinum clusters on vacancy-type defects of nanometer-sized graphene patches

GIGA: a versatile genetic algorithm for free and supported clusters and nanoparticles in the presence of ligands

We present a versatile parallelised genetic algorithm, which is able to perform global optimisation from first principles for pure and mixed free clusters in the gas phase, supported on surfaces or in the presence of one or several atomic or molecular species (ligands or adsorbates). The genetic algorithm is coupled to different quantum chemical software packages in order to permit a large variety of methods for the global optimisation. The genetic algorithm is also capable of optimising different electronic spin multiplicities explicitly, which allows global optimisation on several potential energy hypersurfaces in parallel. We employ the genetic algorithm to study ligand-passivated clusters [Cd3Se3(H2S)3]+ and to investigate adsorption of [Pt6(H2O)2]+ supported on graphene. The explicit consideration of the electronic spin multiplicity during global optimisation is investigated for nanoalloy clusters Pt4V2.

Interband transitions in closed-shell vacancy containing graphene quantum dots complexed with heavy metals

High-performance optical detection of toxic heavy metals by using graphene quantum dots (GQDs) requires a strong interaction between the metals and GQDs, which can be reached through artificial creation of vacancy-type defects in GQDs.

On the interaction of toxic Heavy Metals (Cd, Hg, Pb) with graphene quantum dots and infinite graphene

The promise of graphene and its derivatives as next generation sensors for real-time detection of toxic heavy metals (HM) requires a clear understanding of behavior of these metals on the graphene surface and response of the graphene to adsorption events. Our calculations herein were focused on the investigation of the interaction between three HMs, namely Cd, Hg and Pb, with graphene quantum dots (GQDs). We determine binding energies and heights of both neutral and charged HM ions on these GQDs. The results show that the adsorption energy of donor-like physisorbed neutral Pb atoms is larger than that of either Cd or Hg. In contrast to the donor-like behavior of elemental HMs, the chemisorbed charged HM species act as typical acceptors. The energy barriers to migration of the neutral adatoms on GQDs are also estimated. In addition, we show how the substitution of a carbon atom by a HM adatom changes the geometric structure of GQDs and hence their electronic and vibrational properties. UV-visible absorption spectra of HM-adsorbed GQDs vary with the size and shape of the GQD. Based on our results, we suggest a route towards the development of a graphene-based sensing platform for the optical detection of toxic HMs.

On the Catalytic Activity of Pt Supported by Graphyne in the Oxidation of Ethanol

The adsorption of Pt clusters on β- and γ-graphyne (β-GY, γ-GY), graphdiyne (GDY), and graphene (GP) was extensively investigated with density functional theory. Ethanol adsorption and its partial oxidation on the Pt supported by the GY and GP were then explored to address the influence of the supporting materials on the activity of Pt nanoclusters to ethanol oxidation. Among the examined adsorption sites such as the hollow, Csp-Csp, and Csp-Csp2 bonds, the hollow site consisting of multiple triple bonds is the most attractive one to adsorb Pt and Pt4 regardless of β-GY, γ-GY, and GDY. The binding of Pt4 to the GDY is slightly stronger than those of β-GY and γ-GY (binding energy: -3.64, -3.73, and -4.08eV). It is remarkable that the adsorption of Pt4 on GY is 2-3 times stronger than that on GP (-3.6-4.1 vs -1.3 eV), showing that the GY and GDY are better substracts than the GP for the stability of Pt clusters. Furthermore, the potential energy profiles for the oxidation of ethanol show that in spite of the higher energy barrier for the adsorbed ethanol on Pt4 supported by γ-GY than by GP (1.54 vs 1.19eV), the dehydrogenation product and of ethanol on Pt-graphyne is much stabler than that on Pt-graphene, suggesting that graphyne is thermodynamically more favorable than graphene as a subtract for the Pt catalyst.

Insights into the origin of the excited transitions in graphene quantum dots interacting with heavy metals in different media

Exploring graphene quantum dots (GQDs) is an attractive way to design novel optical and electrochemical sensors for fast and reliable detection of toxic heavy metals (HMs), such as Cd, Hg and Pb.