Photodetecting Heterostructures from Graphene and Encapsulated Colloidal Quantum Dot Films.

Heterostructure devices consisting of graphene and colloidal quantum dots (QDs) have been remarkably successful as photodetectors and have opened the door to technological applications based on the combination of these low-dimensional materials. This work explores the photodetection properties of a heterostructure consisting of a graphene field effect transistor covered by a film of silica-encapsulated colloidal QDs. Defects at the surface of the silica shell trap optically excited charge carriers, which simultaneously enables photodetection via two mechanisms: photogating, resulting in a net p-doping of the device, and Coulombic scattering of charge carriers in the graphene, producing an overall decrease in the current magnitude.

Micron-Size Two-Dimensional Methylammonium Lead Halide Perovskites.

Hybrid lead halide perovskites with 2D stacking structures have recently emerged as promising materials for optoelectronic applications. We report a method for growing 2D nanosheets of hybrid lead halide perovskites (I, Br and Cl), with tunable lateral sizes ranging from 0.05 to 8 μm and a structure consisting of n stacked monolayers separated by long alkylamines, tunable from bulk down to n = 1.

Field Effect and Photoconduction in Au Nanoclusters Films.

Quantum-confined Au nanoclusters exhibit molecule-like properties, including atomic precision and discrete energy levels. The electrical conductivity of Au nanocluster films can vary by several orders of magnitude and is determined by the strength of the electronic coupling between the individual nanoclusters in the film. Similar to quantum-confined, semiconducting quantum dots, the electrical coupling in films is dependent on the size and structure of the Au core and the length and conjugation of the organic ligands surrounding it.

Preparation of high-yield and ultra-pure Au nanoclusters: towards their implementation in real-world applications.

Colloidal approaches allow for the synthesis of Au nanoclusters (NCs) with atomic precision and sizes ranging from a few to hundreds of atoms. In most of the cases, these processes involve a common strategy of thiol etching of initially polydisperse Au nanoparticles into atomically precise NCs, resulting in the release of Au-thiolate complexes as byproducts. To the best of our knowledge, neither the removal of these byproducts nor the mass spectra in the relevant mass region were shown in previous studies.

Large-Area Heterostructures from Graphene and Encapsulated Colloidal Quantum Dots via the Langmuir-Blodgett Method.

This work explores the assembly of large-area heterostructures comprised of a film of silica-encapsulated, semiconducting colloidal quantum dots, deposited via the Langmuir-Blodgett method, sandwiched between two graphene sheets. The luminescent, electrically insulating film served as a dielectric, with the top graphene sheet patterned into an electrode and successfully used as a top gate for an underlying graphene field-effect transistor. This heterostructure paves the way for developing novel hybrid optoelectronic devices through the integration of 2D and 0D materials.

Electronic Properties of Sulfur Covered Ru(0001) Surfaces.

The structural properties of sulfur superstructures adsorbed on Ru(0001) have been widely studied in the past. However, much less effort has been devoted to determine their electronic properties. To understand the connection between structural and electronic properties, we have carried out density functional theory periodic boundary calculations mimicking the four long-range ordered sulfur superstructures identified experimentally by means of scanning tunneling microscopy (STM) techniques.

Organic Covalent Patterning of Nanostructured Graphene with Selectivity at the Atomic Level.

Organic covalent functionalization of graphene with long-range periodicity is highly desirable-it is anticipated to provide control over its electronic, optical, or magnetic properties-and remarkably challenging. In this work we describe a method for the covalent modification of graphene with strict spatial periodicity at the nanometer scale. The periodic landscape is provided by a single monolayer of graphene grown on Ru(0001) that presents a moiré pattern due to the mismatch between the carbon and ruthenium hexagonal lattices.