Uniform graphene quantum dots patterned from self-assembled silica nanodots.

Graphene dots precisely controlled in size are interesting in nanoelectronics due to their quantum optical and electrical properties. However, most graphene quantum dot (GQD) research so far has been performed based on flake-type graphene reduced from graphene oxides. Consequently, it is extremely difficult to isolate the size effect of GQDs from the measured optical properties. Here, we report the size-controlled fabrication of uniform GQDs using self-assembled block copolymer (BCP) as an etch mask on graphene films grown by chemical vapor deposition (CVD). Electron microscope images show that as-prepared GQDs are composed of mono- or bilayer graphene with diameters of 10 and 20 nm, corresponding to the size of BCP nanospheres. In the measured photoluminescence (PL) spectra, the emission peak of the GQDs on the SiO(2) substrate is shown to be at ∼395 nm. The fabrication of GQDs was supported by the analysis of the Raman spectra and the observation of PL spectra after each fabrication step. Additionally, oxygen content in the GQDs is rationally controlled by additional air plasma treatment, which reveals the effect of oxygen content to the PL property.

Photoswitchable quantum dots by controlling the photoinduced electron transfers.

We report photoluminescence (PL) modulation of quantum dots (QDs) by photoinduced electron transfers from acridine-1,8-dione derivative surface ligands. Reversible PL switching upon many repeated cycles was demonstrated, as alternating on and off of the UV excitation for the surface ligand has successfully resulted in the QD PL modulation.

Nanotransfer printing with sub-10 nm resolution realized using directed self-assembly.

An extraordinarily facile sub-10 nm fabrication method using the synergic combination of nanotransfer printing and the directed self-assembly of block copolymers is introduced. The approach is realized by achieving the uniform self-assembly of polydimethylsiloxane (PDMS)-containing block copolymers on a PDMS mold through the stabilization of the block copolymer thin films. This simple printing method can be applied on oxides, metals, polymers, and non-planar substrates without pretreatments. The fabrication of well-aligned metallic and polymeric functional nanostructures and crossed wire structures is also presented.

Assembled monolayers of hydrophilic particles on water surfaces.

A facile and quick approach to prepare self-assembled monolayers of water-dispersible particles on the water surface is presented. Particle suspensions in alcohols were dropped on a water reservoir to form long-range ordered monolayers of various particles, including spherical solid particles, soft hydrogel particles, metal nanoparticles, quantum dots, nanowires, single-wall carbon nanotubes (SWCNTs), nanoplates, and nanosheets. A systematic study was conducted on the variables affecting the monolayer assembly: the solubility parameter of spreading solvents, particle concentration, zeta potential of the particles in the suspension, surface tension of the water phase, hardness of the particles, and addition of a salt in the suspension. This method requires no hydrophobic surface treatment of the particles, which is useful to exploit these monolayer films without changing the native properties of the particles. The study highlights a quick 2D colloidal assembly without cracks in the wafer scale as well as transparent conductive thin films made of SWCNTs and graphenes.