Ya-Ping Sun

Bandgap‐Like Strong Fluorescence in Functionalized Carbon Nanoparticles

Semiconductor quantum dots (QDs), especially the highly fluorescent CdSe-based core-shell nanostructures, have generated much excitement for their variety of potential applications in optical bioimaging and beyond.[1,2] These QDs are widely considered as being more advantageous over conventional organic dyes as well as genetically engineered fluorescent proteins in terms of optical brightness and photostability.[1,3–5] However, a serious disadvantage with these popular QDs is their containing heavy metals such as cadmium, whose significant toxicity and environmental hazard are well-documented.[6–9] Alternative benign (nontoxic) QD-like fluorescent nanomaterials have therefore been pursued, including the recent finding of fluorescent carbon nanoparticles (dubbed “carbon dots”).[10,11]

Metallic single-walled carbon nanotubes for conductive nanocomposites.

This article reports an unambiguous demonstration that bulk-separated metallic single-walled carbon nanotubes offer superior performance (consistently and substantially better than the as-produced nanotube sample) in conductive composites with poly(3-hexylthiophene) and also in transparent conductive coatings based on PEDOT:PSS. The results serve as a validation on the widely held view that the carbon nanotubes are competitive in various technologies currently dominated by conductive inorganic materials (such as indium tin oxide).

Functionalized carbon nanotubes for polymeric nanocomposites

Functionalized carbon nanotubes are more favorable for the desired homogeneous dispersion of exfoliated nanotubes as nanoscale fillers in polymeric nanocomposites. However, the compatibility of the large amount of functional groups necessary for the nanotube functionalization with the polymeric matrices is critical to the properties and performance of the resulting nanocomposites. We have developed an approach of only using functional polymers that are structurally identical or maximally similar to the matrix polymers in the functionalization and solubilization of carbon nanotubes. Several representative examples are highlighted, and issues concerning the characterization and evaluation of the polymeric nanocomposites thus obtained are discussed.

Graphene Oxides Dispersing and Hosting Graphene Sheets for Unique Nanocomposite Materials

Graphene oxides (GOs), beyond their widely reported use as precursors for single-layer graphene sheets, are in fact excellent materials themselves (polymers in two-dimension, polyelectrolyte-like, aqueous solubility and biocompatibility, etc.). In this reported work we used aqueous GOs to effectively disperse few-layer graphene sheets (GNs) in suspension for facile wet-processing into nanocomposites of GNs embedded in GOs (as the polymeric matrix). The resulting lightweight and plastic-like nanocomposite materials remained mechanically flexible even at high loadings of GNs, and they were found to be highly efficient in thermal transport, with the experimentally determined thermal diffusivity competitive to those typically observed only in well-known thermally conductive metals such as aluminum and copper. As demonstrated, GOs apparently represent a unique class of two-dimensional polymeric materials for potentially all-carbon nanocomposites, among others, which may find technological applications independent of those widely proclaimed for graphene sheets.

Solubilization of boron nitride nanotubes

A successful attempt in the functionalization and solubilization of boron nitride nanotubes is reported, and a functionalization mechanism based on interactions of amino functional groups with nanotube surface borons is proposed.

Separated metallic and semiconducting single-walled carbon nanotubes: opportunities in transparent electrodes and beyond.

Ever since the discovery of single-walled carbon nanotubes (SWNTs), there have been many reports and predictions on their superior properties for use in a wide variety of potential applications. However, an SWNT is either metallic or semiconducting; these properties are distinctively different in electrical conductivity and many other aspects. The available bulk-production methods generally yield mixtures of metallic and semiconducting SWNTs, despite continuing efforts in metallicity-selective nanotube growth. Presented here are significant advances and major achievements in the development of postproduction separation methods, which are now capable of harvesting separated metallic and semiconducting SWNTs from different production sources with sufficiently high enrichment and quantities for satisfying at least the needs in research and technological explorations. Opportunities and some available examples for the use of metallic SWNTs in transparent electrodes and semiconducting SWNTs in various device nanotechnologies are highlighted and discussed.

Carbon nanoparticles as chromophores for photon harvesting and photoconversion.

Carbon nanomaterials have generated a tremendous amount of attention in the scientific community. While most of the research and development efforts have been on fullerenes, carbon nanotubes, and graphene sheets, carbon nanoparticles (which are often considered as impurities or unwanted complications in the other carbon nanomaterials) have recently emerged as a unique class of highly fluorescent nano-dots. However, little or no attention has been paid to potential uses of carbon nanoparticles as chromophores in photochemical reactions or for photon harvesting and photoconversion in general. In the study reported herein we demonstrate the chromophore-equivalent functions of aqueous-suspended small carbon nanoparticles in harvesting visible photons for the reductive coating of the nanoparticles with silver and gold and, as a result, the preparation of unique carbon-noble-metal core-shell nanostructures.