Electronic Detection of Oxygen Adsorption and Size‐Specific Doping of Few‐Atom Gold Clusters on Graphene

Abstract

COMMUNICATION (1 of 8)properties in graphene, such as (tunable) bandgaps [12] or p-n junctions. [13] Metal atoms and nanoparticles are interesting candidates to tailor graphene. [14] The charge transfer between adparticles and graphene results in tunable (surface) electronic states, which can act as active sites for heterogeneous catalysis, [4,[15][16][17] or enhance the sensitivity and selectivity of graphene gas sensors (see ref.[18] and references therein). Furthermore, metal adparticles are prime candidates to induce a (tunable) spin-orbit coupling in graphene, enhancing for instance the spin Hall effect, [19] which further augments graphene's spintronic potential. [20] Due to the extreme sensitivity of graphene devices, one desires a high level of control in adsorbing metal adparticles. Such control is offered by state-of-the-art cluster fabrication and deposition techniques, which allows to select the size and composition of clusters with atomic resolution, and tune the deposition energy and adparticle density. [21] Using these techniques, ultrasmall few-atom clusters in gas-phase showcased a distinct atom-by-atom size-dependence in the electronic and structural properties, leading to different and unique physicochemical properties. [22] The size-dependent characteristics can be preserved in the interaction of a cluster with a support. For specific gold, cobalt and germanium clusters, dedicated atomic resolution surface probe studies, using scanning tunneling microscopy [23,24] and scanning transmission electron microscopy, [25][26][27][28] have, in combination with density functional theory (DFT) simulations, allowed for a detailed morphological characterization of clusters on supports. The overall properties of a cluster-support system retain a dependence on the exact cluster size. [15] As such, cluster-support systems, engineered with atomic precision, are, among others, of interest as catalysts [29][30][31][32] and lowreactive building blocks for nanosystems. [33] In the size-regime in between single atoms and larger nanometer-sized particles, clusters offer diverse possibilities in functionalizing graphene.To the best of our knowledge, there has been no realization yet of an electronic device, in which the rich size-dependence of few-atom metal clusters is transpired in the properties of the device, although this has been proposed in several computational studies for few-atom metal clusters on graphene. [34][35][36] To that avail, we combine in this work single layer graphene (G) with few-atom gold clusters. In particular, these clusters Graphene's sensitivity to adsorbed particles has attracted widespread attention because of its potential sensor applications. Size-selected few-atom clusters are promising candidates as adparticles to graphene. Due to their small size, physicochemical properties are dominated by quantum size effects. In particular, few-atom gold clusters demonstrate a significant catalytic activity in various oxidation reactions. In this joint experimental and computational work, size-...

Au3-Decorated graphene as a sensing platform for O2 adsorption and desorption kinetics

“…The experimental procedure of depositing few-atom clusters on graphene devices was introduced in previous publications. 26,27 In brief, the electronic measurements were done on a GFET, which consists of a graphene layer deposited on top of a 300 nm SiO 2 layer thermally grown on a heavily doped silicon substrate. When a back-gate voltage V g is applied to the silicon substrate, an electric field induces charge carriers in the graphene strip, changing its resistivity.…”

“…It has been demonstrated that every deposited Au 3 cluster induces ε e electrons (with ε e > 0, n-doping) and every Au 3 -O 2 complex ε h electrons (with ε h < 0, p-doping) in the graphene strip. 27 Consequently, ε tot the total number of induced electrons in the graphene strip, equals ε e N Au 3 + ε h N Au 3 O 2 , with N Au 3 the number of bare Au 3 clusters and N Au 3 O 2 the number of Au 3 -O 2 complexes. Upon adsorption of one O 2 molecule on a Au 3 cluster, ε tot changes by an amount ε h − ε e = ε O 2 .…”

“…This functionalizes the graphene strip as an oxygen detector, as was shown in a previous publication by some of the authors. 27 In the current article, we develop this idea further by controlled in situ measurements during the oxygen molecule adsorption and desorption processes that allow to quantify the adsorption barrier, the desorption energy as well as entropy changes during the desorption process, values that so far have been very challenging to obtain experimentally.…”

Engineering single-atom catalysts toward biomedical applications

“…Consequently, the few-atom clusters may show metal-coordination atom (N,O)-metal bonds without the direct metal-metal bond. [191][192][193] Notably, different aggregated atom numbers cause a large difference for the geometric and electronic structures, which could be exactly utilized to distinguish the few-atom clusters, nanoclusters and nanoparticles. For example, the few-atom clusters of Au n (2 r n r 7) are characterized by a planar geometric structure (Fig.…”

MoS2/Graphene Composites as Promising Materials for Energy Storage and Conversion Applications

“…[10,11] 2D materials and their most famous example graphene has attracted enormous worldwide attention and are regarded as a potential candidates for a wide range of applications, including supercapacitors, batteries, catalysis, sensors, wearable electronics, protective coatings, composites, etc. [12][13][14][15][16][17] Graphene, a 2D material in the form of atomically thin sheets composed of carbon atoms that are arranged in a hexagonal array, has many outstanding properties including high electrochemical properties, thermal & optical characteristics, eco-friendliness, high specific surface area, high capacitance, super elasticity and flexibility. [3,18,19] Therefore, graphene could be an ideal platform for energy applications, such as a conductive electrode, high capacity electrode or even as a hydrogen storage.…”