Simple preparation of lotus-root shaped meso-/macroporous TiO2 and their DSSC performances.

In pursuit of superior TiO2 photoanode materials for dye-sensitized solar cells (DSSCs), we prepared lotus-root shaped meso-/macroporous TiO2. The lotus-root shaped meso-/macroporous TiO2 was easily prepared by using a cetyltrimethylammonium hydroxide (CTAOH) template in aqueous solution. The crystallization of the as-prepared amorphous lotus-root shaped TiO2 was performed at 700 °C in air. Crystalline anatase phase with a very small portion of rutile phase was generated after the heat treatment at 700 °C and the BET surface area of crystalline lotus-root shaped meso-/macroporous TiO2 material (LR-700) was 30.0 m(2) g(-1). The wall of LR-700 displayed well-developed mesoporosity with a pore dimension of 28.3 nm. Periodically arranged microscale one-dimensional (1D) macropores were also observed in the particles. The photon-to-current conversion efficiencies (η) of LR-700 photoanodes in Grätzel type DSSCs were examined. The conversion efficiency of DSSC prepared by mixing nanoparticulate Evonik P25 and LR-700 (ratio=85:150 by mass) was 28% greater compared to the reference electrode using P25. Incident photon-to-current efficiencies (IPCE) of the DSSCs were dramatically improved by employing the photoanodes composed of a mixture of P25 and LR-700 but impedance analysis indicated that P25/LR-700 mixed cells have resistances similar to the standard P25 reference cell. Thus, photovoltaic performances could be improved mainly due to the increases of dye uptake and external quantum efficiency by using a mixed photoanode composed of LR-700 and nanocrystalline P25 particles.

Hollow S-doped carbon spheres from spherical CT/PEDOT composite particles and their CO2 sorption properties.

Chemically functionalizable shape-controlled poly(3,4-ethylenedioxythiophene) (PEDOT)-derived conducting copolymers, C1(C4)-CT/PEDOT/PSS-20APS and C1(C4)-CT/PEDOT/PSS-10APS, were prepared through oxidative polymerization of 3,4-ethylenedioxythiophene (EDOT) and 3-thiophenecarboxylic acid (C1-CT) or 4-(3-thienyl)butyric acid (C4-CT) in the presence of acid-labile mesoporous ZnO/Zn(OH)2 hard template. The mesoporous ZnO/Zn(OH)2 hard template could be removed by mild acid etching. The morphology of these polymeric microparticles was dependent on the concentration of ammonium persulfate (APS, (NH4)2S2O8) catalyst and the type of CT monomers. Hollow capsular C1-CT/PEDOT/PSS-20APS copolymer spheres with a large surface opening were obtained when the amount of oxidizing agent APS was 20mmol under the same experimental conditions. Because C1(C4)-CT/PEDOT/PSS-xAPS copolymers contain S-rich moieties in the polymer backbone, they are suited for the preparation of S-doped carbonaceous materials. Therefore, we carbonized C1-CT/PEDOT/PSS-20APS at several different temperatures in a high-purity nitrogen atmosphere to easily prepare hollow S-doped carbon spheres (HSCSs). The level of S-dopants in carbon spheres was strongly dependent on the carbonization temperature. Lower carbonization temperature led to a higher content of S-dopants but lower BET surface area. These carbon spheres were further analyzed by TEM, SEM, PXRD, and XPS. Gas sorption analyses were also performed to study gas sorption with different amount of S-dopants.

Facile preparation of SERS-active nanostructured Au spheres by simple reduction of AuCl4- ions with EDOT.

Uniform submicron-scale Au spheres with an average dimension of 574 nm were facilely prepared from the redox reaction between HAuCl4 and 3,4-ethylenedioxythiophene (EDOT) in aqueous solution under ambient conditions. HAuCl4 precursor readily polymerized to poly(3,4-ethylenedioxythiophene) (PEDOT) and metallic Au spheres simultaneously formed within a short period of time. The Au spheres are consisted of two slightly different types of spherical particles based on their surface textures. Major raspberry-like Au spheres are formed through the assembly of very tiny Au nanoparticles, while minor rosette-like Au spheres are formed through the dense packing of Au nanoplates. Both Au spheres are pure metallic face-centered cubic Au based on X-ray photoelectron spectroscopy and powder X-ray diffraction. The resultant Au spheres are adequate for application to surface-enhanced Raman scattering (SERS) due to their rough surfaces and nanogaps on the surfaces. Both methylene blue and crystal violet molecules were detectable at concentrations as low as 10(-7) M.

Effect of nitrogen doping on the performance of dye-sensitized solar cells composed of mesoporous TiO2 photoelectrodes.

Nitrogen-doped mesoporous TiO2 (NMP TiO2) nanoparticles are synthesized using a soft triblock copolymer template by TiCl4 hydrolysis with ammonia water and applied to the photoelectrodes of dye-sensitized solar cells (DSSCs). The large surface area of a TiO2 mesoporous structure is favorable for dye uptake, and nitrogen doping of TiO2 is expected to increase the charge transport in the photoelectrode as well as the scattering of visible light. Structural characterizations for NMP TiO2 nanoparticles by XRD, XPS, BET, and BJH analyses revealed successful synthesis. However, the photovoltaic performances of the DSSCs prepared from NMP TiO2 were not improved, as had been expected: the photo-conversion efficiency (η) of DSSCs from undoped mesoporous TiO2 (MP TiO2) was 4.69%, an improvement over the 4.15% with the application of P25 TiO2, but the efficiency of DSSCs from NMP TiO2 decreased to 3.2-3.6%. The measured amounts of adsorbed dye showed that nitrogen doping did not significantly affect dye adsorption. Therefore, it can be concluded that nitrogen doping increases isotropic charge transport in a TiO2 nanoparticle to promote charge recombination into an electrolyte, despite its advantages. The full benefits of nitrogen doping may be obtained through measures such as the deposition of a thin barrier layer of oxide onto the TiO2 surface to prevent charge recombination during charge transport in the TiO2 network.

2-Thiopheneacetic acid directed synthesis of Au nanorosette as an SERS-active substrate.

Rosette-like nanoscale Au materials were simply prepared through one-pot reduction of the AuCl4⁻ precursor by 2-thiopheneacetic acid (2-TAA) without extra surface capping ligands at room temperature. 2-TAA underwent polymerization into polythiophene derivatives while the AuCl4⁻ precursor was simultaneously reduced into various Au nanostructures. In situ generated polythiophene derivatives played a significant role of surface passivation in guiding the shape of Au nanostructures. The morphology of Au nanostructures was strongly dependent on the molar ratio of 2-TAA to AuCl4⁻. At lower [2-TAA]/[AuCl4⁻] ratios, uniform rosette-like Au microparticles consisting of 30-nm-thick Au nanoplates were observed. The Au nanoplates had either triangular prismatic or hexagonal geometry with many defects. Uniform Au nanorosettes could be easily deposited on the Si substrate by drop-casting and were subsequently used as highly active SERS substrates for the detection of methylene blue and crystal violet by Raman spectroscopy. Upon increasing the ratio of [2-TAA]/[AuCl4⁻], Au nanoparticles or nanorods heavily surrounded with polythiophene polymers were obtained.

Controlled growth of narrowly dispersed nanosize hexagonal MOF rods from Mn(III)-porphyrin and In(NO3)3 and their application in olefin oxidation.

A new class of narrowly dispersed nanosize hexagonal MOF rods from Mn(III)-porphyrin and In(III) was obtained. The length of MOF rods was controlled by simple change of reaction times. Furthermore, the oxidation of styrene has been successfully demonstrated with Mn(III)-porphyrin MOF rods and their reusability has been also tested.

Facile preparation of SERS-active nanogap-rich Au nanoleaves.

To simply reduce HAuCl(4) using 2-thiophenemethanol in an aqueous solution at room temperature, a novel metallic Au nanostructure with a high SERS activity was obtained. Flat sheet-like Au nanoleaves possessing many nanogap hotspots bound with a large percentage of high-index facets were obtained.