Nanoscale Organization of GaSe Quantum Dots on a Gold Surface

Abstract

Precise spatial organization and electronic coupling between quantum dots are pivotal for many potential applications. Typical spherical quantum dots in assemblies are separated by organic ligands and hence weakly coupled. GaSe nanoparticles are disk-like particles that are four atoms thick with tunable lateral dimensions. Previous spectroscopic investigations indicate the formation of nanoscale aggregates in which the quantum dots are strongly coupled. In this report, we show that the anisotropic properties of these particles may be exploited to assemble surface-stabilized superstructures with well-defined distances between the quantum dots. By changing the ligands adsorbed on the nanoparticle edges, three distinct aggregate morphologies can be produced. The surface chemistry of GaSe orients the nanoparticles on a gold surface and induces stacking in the surface normal direction. The discrete heights of such stacked aggregates suggest that the layers are held together by van der Waals interactions with a regular spacing. Such structures, with their well-defined electronic coupling, have potential implications in fundamental studies of photoinduced charge transfer and transport, as well as device fabrications.

Linear and NLO spectroscopy of GaSe and InSe nanoparticles formed via laser ablation

“…Transitions from parabolic to ring-shaped valence band maximum in few-layer GaS, GaSe, and InSe was reported 19 . More results concerning the properties of GaSe nanoaggregates may be found [20][21][22][23][24][25][26][27][28][29][30] . 4 for GaSe) and possible controlling mechanism were discussed by the authors 31 .…”

Effect of the phosphorous-containing ligands on synthesis and properties of GaSe nanoparticles

“…Earlier investigations, conducted on GaSe syntheses [6][7][8] imply that above-mentioned particles were stabilised and capped either by distilled TOP/TOPO ligands (like II-VI core/shells), being weakly bonded; thus, not allowing prolonged storage of such particles or by strongly bonded intrinsic anhydride. The last one was formed by thermal treatment of technical TOP/TOPO mixtures.…”

“…Thus, numerous precipitation/redissolving cycles are impossible and even careful washing of the precipitate does not allow to get completely rid out of the ligating complexes. Since the spectroscopic properties of TOP/TOPO (i.e., TOPSe/TOPO)-capped GaSe particles were subject of many reports, we omit them and refer the reader to original works [6][7][8]. Figure 3 illustrates UV-Vis absorbance of OPA-capped particles.…”

“…Among the variety of semiconductor nanoparticles, layered III-VI compounds in low-dimensional forms have already reached the level of implementation in microelectronic devices due to their unique anisotropic properties [1,2]. Nevertheless, colloidal III-VI nanostructures investigations are far from the successful II-VI compounds and limited by several reports on the single-source metalorganic precursor [3,4], amine-capped particles syntheses from metal chloride [5] and growth by reaction of metalorganic precursor with trioctyphosphine (TOP) selenium in alkylphosphonic solvent [6][7][8]. The last method appeared to be strictly dependent on the TOP impurities and generally is irreproducible in pure TOP/TOPO solvents.…”

“…The last method appeared to be strictly dependent on the TOP impurities and generally is irreproducible in pure TOP/TOPO solvents. Octylphosphonic acid (OPA) was preliminary known as specie playing a key factor in GaSe nanoparticles syntheses and stability [8]. Nevertheless, neither OPA nor shorter chain phosphonic acids allow controlling syntheses, ligand stability and prolonged storage of GaSe nanoparticles.…”