Enhanced Photoresponse of High Crystalline Bi2Se3 Thin-Films Using Patterned Substrates.

High-quality Bi2Se3 thin films with topological insulating properties at room temperature have recently attracted much attention as one of the promising materials for realizing innovative electronic and optoelectronic devices. Here, we report the high crystallinity growth of Bi2Se3 thin films on a patterned sapphire substrate (PSS) by using a vapor-phase transport deposition with minimizing thermal dissociation of Se atoms vaporized in Bi2Se3 powder. This PSS not only reduces the large dislocation of heterogeneously grown Bi2Se3 on a sapphire substrate but also induces enhanced light absorption in the visible to near-infrared (IR) ranges compared to Bi2Se3 on planar sapphire substrates. Thus, the Bi2Se3 thin film laterally grown on the PSS reveals uniform surface properties and high crystallinity in the rhombohedral lattice phase with a full width at half maximum of 0.06° for the XRD (003) peak. Also, the photoresponse of the fabricated IR conversion device using Bi2Se3/PSS heterostructure exhibits excellent performance and high reliability with no degradation after continuous switching. As a result, the device constructed with the Bi2Se3/PSS exhibits one order of magnitude higher NIR induced-photocurrent and 1-2 orders of magnitude faster photo-switching than that with Bi2Se3/Al2O3. Such an enhancement in the device performance of Bi2Se3/PSS is confirmed by the increased absorption spectra in visible and NIR ranges and the improved light absorption distribution.

All-solution-processed flexible thin film piezoelectric nanogenerator.

An all-solution-processed flexible thin film piezoelectric nanogenerator is demonstrated using reactive zinc hydroxo-condensation and a screen-printing method. The highly elastic thin film allows the piezoelectric energy to be generated through the mechanical rolling and muscle stretching of the piezoelectric unit. This flexible all solution-processed nanogenerator is promising for use in future energy harvesters such as wearable human patches and mobile electronics.

Development of delivery methods for carbohydrate-based drugs: controlled release of biologically-active short chain fatty acid-hexosamine analogs.

Carbohydrates are attractive candidates for drug development because sugars are involved in many, if not most, complex human diseases including cancer, immune dysfunction, congenital disorders, and infectious diseases. Unfortunately, potential therapeutic benefits of sugar-based drugs are offset by poor pharmacologic properties that include rapid serum clearance, poor cellular uptake, and relatively high concentrations required for efficacy. To address these issues, pilot studies are reported here where 'Bu(4)ManNAc', a short chain fatty acid-monosaccharide hybrid molecule with anti-cancer activities, was encapsulated in polyethylene glycol-sebacic acid (PEG-SA) polymers. Sustained release of biologically active compound was achieved for over a week from drug-laden polymer formulated into microparticles thus offering a dramatic improvement over the twice daily administration currently used for in vivo studies. In a second strategy, a tributanoylated ManNAc analog (3,4,6-O-Bu(3)ManNAc) with anti-cancer activities was covalently linked to PEG-SA and formulated into nanoparticles suitable for drug delivery; once again release of biologically active compound was demonstrated.