Preparation of anatase/rutile mixed-phase titania nanoparticles for dye-sensitized solar cells.

Acid-labile high surface mesoporous ZnO/Zn(OH)2 composite material is used as a novel hard template for the preparation of mesoporous amorphous TiO2. The template-free amorphous TiO2 material is then thermally crystallized at suitable temperature to control the relative ratio of anatase and rutile phases in a particle. Four different anatase/rutile (AR) mixed-phase TiO2 nanoparticles (AR-3, AR-15, AR-20, and AR-23 denoted for the samples of 3%, 15%, 20%, and 23% rutile phase, respectively) are prepared and characterized by powder X-ray diffraction (PXRD) and transmission electron microscopy (TEM). The coexistence of anatase and rutile phases in a TiO2 nanoparticle is visually confirmed by HRTEM analysis. These mixed-phase TiO2 nanoparticles are examined as candidates for photoelectrodes of dye-sensitized solar cells (DSSCs). The J-V curves and IPCE spectra for the DSSCs prepared from the mixed-phase TiO2 nanoparticles are obtained, and their photovoltaic properties are investigated. The photo-conversion efficiency (eta) indicates the highest value of 5.07% for AR-20. The synergistic effect of coexisting anatase and rutile phases with an optimal ratio in a TiO2 nanoparticle of AR-20 for an efficient interfacial transfer of photo-generated electrons is likely to lead to the highest efficiency among the AR-n samples.

Intracellular protein delivery by hollow mesoporous silica capsules with a large surface hole.

We prepared cell membrane-permeable hollow mesoporous silica capsules (HMSCs) by a simple new method. CTAB micellar assembly in cholesterol emulsion gave rise to a novel capsular morphology of the HMSC particles. The HMSCs consisted of mesostructured silica walls with a large surface hole (25-50 nm) and the average particle dimension was 100-300 nm. They exhibited high surface areas of up to 719.3 m(2) g(-1) and a mesoporous range of pores of 2.4-2.7 nm. The surface-functionalized HMSCs could also be prepared by a similar co-condensation method using tetraethoxysilane with various organoalkoxysilane precursors in the presence of cholesterol. These organically modified HMSCs could be further modified on demand. For example, a carboxy-functionalized HMSC could be surface-functionalized by a green fluorescent 5-aminofluorescein (AFL) through an amidation reaction to afford a fluorescent AFL-HMSC. The hollow capsular morphology of the HMSCs with a large surface hole enabled us to develop very efficient intracellular delivery systems for membrane-impermeable ions, molecules, and various functional proteins. Non-covalent sequestration and delivery of proteins as well as covalent linkage of fluorescent molecules on the silica surface are effective for this system. The highly negatively charged green fluorescent probe mag-fluo-4 could be intracellularly delivered into HeLa cells by HMSC without any difficulty. The HMSCs could also effectively transport large functional proteins such as antibodies into HeLa cells. The efficiency of protein delivery by HMSC seems to be 3-22-fold higher than that of mesoporous silica nanospheres (MSNs) based on confocal laser scanning microscopy (CLSM) analysis.

Gas sorption and supercapacitive properties of hierarchical porous graphitic carbons prepared from the hard-templating of mesoporous ZnO/Zn(OH)2 composite spheres.

Three-dimensional (3D) hierarchical porous carbon materials (PCMs) with graphitic carbon walls are facilely prepared through the hard-templating of acid-labile mesoporous ZnO/Zn(OH)2 spheres. Furfuryl alcohol or phloroglucinol is employed as a carbon precursor for two hierarchical porous carbon materials (PCM-F and PCM-P). The basic surfaces of ZnO/Zn(OH)2 are highly suited to the polymerization of the carbon precursors without extra catalysts. After carbonization followed by mild acid etching, hierarchical PCMs are obtained. These PCMs consist of interconnected turbostratic carbon wall structures. Gas sorption analysis indicates the surface areas of PCM-F and PCM-P are 1013 and 1075 m2 g-1, respectively. The corresponding pore volumes are very large, 3.39 and 3.01 cm3 g-1, respectively. The uptake abilities for carbon dioxide and hydrogen are investigated at 196 and 77 K, respectively. The PCM-P reveals higher uptake of H2 (1.19 wt%) and CO2 (282.0 cm3 g-1) than for PCM-F. In contrast, PCM-F shows a high gravimetric specific capacitance of 329.5 F g-1 based on galvanostatic charge/discharge curves at a current density of 0.1 A g-1. The PCM-F exhibits stable capacitance retention after 10,000 cycles at a current density of 5 A g-1.

Simple preparation of Pd-NP/polythiophene nanospheres for heterogeneous catalysis.

A very simple preparation was developed for catalytically active Pd-nanoparticles (Pd-NPs) decorating polythiophene conducting polymer nanospheres by the redox reaction between PdCl4(2-) ion and 2-thiophenemethanol (2-TPM) in an aqueous solution at room temperature. 2-TPM polymerized to form polythiophene nanospheres in the presence of PdCl4(2-) ions, reduced to Pd-NPs without the need for extra reducing agents or organic surface capping ligands for sub-20 nm Pd-NPs that uniformly cover polythiophene nanospheres whose dimensions range from 120 nm to 200 nm. The Pd-NP/polythiophene nanospheres were characterized by scanning transmission electron microscopy (STEM), transmission electron microscopy (TEM), and scanning electron microscopy (SEM), powder X-ray diffraction (PXRD), X-ray photoelectron spectroscopy (XPS), and inductively-coupled plasma atomic emission spectroscopy (ICP-AES). The Pd-NP/polythiophene nanospheres were found to be an excellent catalyst for Suzuki-Miyaura cross-coupling reaction for a wide range of substrates under mild aerobic reaction conditions.

Facile preparation of ultra-large pore mesoporous silica nanoparticles and their application to the encapsulation of large guest molecules.

Pore-enlarged mesoporous silica nanoparticles (MSNs) were prepared directly from as-prepared MSNs through a new, simple method using divalent Ca or Mg salts as both efficient silica etching reagents and as ion exchangers in methanolic solution under mild conditions. The resultant MSNs became almost template-free simultaneously during this etching process. The pore-enlarged MSNs, referred to as Ca-MSN or Mg-MSN, maintained their original hexagonal pore symmetry and particle sizes, but several ultra-large mesopores were generated inside and outside the MSNs together with regular mesopores having expanded pore dimension of around 4-5 nm. The average pore diameters for ultra-large pores were 47.5 nm for Ca-MSN and 52.4 nm for Mg-MSN. The generation of ultra-large pores can be regarded as the collapse of several mesopores into an ultra-large pore. Both Ca-MSN and Mg-MSN were good sorbents for positively charged porphyrin molecules. Additionally, these ultra-large pore MSNs exhibited better adsorption ability than calcined MSN for large proteins and antibodies, such as bovine serum albumin (BSA) and immunoglobulin G (IgG).

CO2 selective dynamic two-dimensional Zn(II) coordination polymer.

A CO2 selective dynamic two-dimensional (2D) MOF system, [Zn(glu)(µ-bpe)]·2H2O (·2H2O) (glu = glutarate, bpe = 1,2-bis(4-pyridyl)ethylene), is prepared. Based on variable temperature PXRD patterns, I·2H2O exhibits a structural transformation of the framework upon desolvation. Various gas sorption analyses at low temperatures reveal that solvent-free I selectively adsorbs CO2 over N2, H2, and CH4. Stepped CO2 isotherms for solvent-free I with a large hysteresis between adsorption and desorption branches at 196 K indicate that I is a dynamic framework. Moreover, I·2H2O shows efficient heterogeneous catalytic reactivity for transesterification of various esters. The catalyst can be recycled multiple times without losing its original activity.

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.