Control of pore size and pore uniformity in films based on self‐assembling block copolymers

Blends of self‐assembling polystyrene‐block‐poly(4‐vinyl pyridine) (PS‐b‐P4VP) diblock‐copolymers and poly(4‐vinyl pyridine) (P4VP) homopolymers were used to fabricate isoporous and nanoporous films. Block copolymers (BCP) self‐assembled into a structure where the minority component forms very uniform cylinders, while homopolymers, resided in the core of the cylinders. Selective removal of the homopolymers by ethanol immersion led to the formation of well‐ordered pores. In films without added homopolymer, just immersion in ethanol and subsequent swelling of the P4VP blocks was found to be sufficient to create pores. Pore sizes were tuned between 10 and 50 nm by simply varying the homopolymer content and the molecular weight of the block‐copolymer. Uniformity was lost when the average pore size exceeded 30 nm because of macrophase separation. However, preparation of films from low M_W diblock copolymers showed that it is possible to have excellent pore size control and a high porosity, while retaining a low pore size distribution. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014 , 52, 1568–1579     

Adsorption Equilibrium of Alkanes on a High Surface Area Activated Carbon Prepared from Brazilian Coconut Shells

Adsorption equilibria of methane, ethane, and n-butane on a high surface area activated carbon prepared from Brazilian coconut shells is examined in this study. The material shows high capacities for the alkanes tested. A group-contribution theory is used to predict adsorption isotherms for all three components with very good accuracy employing one set of model parameters. The theory is also used to observe trends in isosteric heat of adsorption as a function of loading at various temperatures.     

Raman Spectroscopic Investigations of the Effects of Ag+ and Ce3 + Doping on the Densification of Nanoporous Silica Xerogels

Doped and undoped 50 Å porous silica xerogels were heat-treated at various annealing temperatures ranging from 800°C to 1150°C. The heating was performed in air for 1 hour at each temperature. Raman spectroscopy was used to follow the structural changes occurring at various stages of the gel-to-glass transformation, as well as to investigate the effects of metal ions on the densification of these nanoporous silica xerogels. Raman data and density measurements showed that while densification is completely achieved at 1050°C for undoped xerogels, it occurs at 950°C for Ag⁺-doped samples. On the other hand, Ce^{3 +} doping was found to slow down the densification process, with complete densification occurring at 1100°C.     

TiO_2/CdS/Ru(bpy)_2(NCS)_2作为太阳电池光阳极的探讨

将 Cd S纳米粒子复合在 Ti O2 纳米多孔膜上 ,用染料 Ru( bpy) 2 ( NCS) 2 对此复合半导体纳米膜电极进行敏化 ,测量了不同 Cd S复合量的 ITO/Ti O2 /Cd S/Ru( bpy) 2 ( NCS) 2 光阳极组成光电池的能量转换效率 .实验证明 ,ITO/Ti O2 /Cd S/Ru( bpy) 2 ( NCS) 2 作为太阳电池光阳极的能量转换效率与 Ti O2 /Cd S复合半导体中 Cd S的含量有关 .当 Cd S复合时间为 5 min的电池的短路电流为 5 .2 3A/m2 ,开路电压为 0 .71 6 V,能量转换效率为 0 .77% .     

The Core-Shell Approach to Formation of Ordered Nanoporous Silicas by MPEG-b-PLA Block Copolymers

Selected MPEG-b-PLA block copolymer templates have been synthesized by ring-opening polymerization, with systematic variation of the chain lengths of the hydrophilic and hydrophobic blocks. The size and shape of the micelles that spontaneously form in solution are controlled by the characteristics of the block copolymer template. Tunable pore sizes ranging from 2 to 8 nm were achieved in the templated synthesis of ordered nanoporous silica by increasing the hydrophobic chain lengths. The highest surface area observed by BET analysis was 660 m²/g. The formation mechanism of these nanoporous structures, obtained by controlling the micelle size, has been confirmed using both liquid and solid state ¹³C and ²⁹Si NMR techniques. This work verifies the formation mechanism of nanoporous structures in which the pore size and wall thickness are closely dependent on the size of the hydrophobic cores and hydrophilic shells of the block copolymer templates.     

汞溴红敏化TiO2纳米多孔膜电极的光电化学性质研究

用汞溴红(Mercurochrome)作敏化剂敏化TiO2纳米多孔膜电极,UV-Vis,光电流作用谱和SPS谱表明,该敏化剂能有效地敏化TiO2电极,并且染料聚集体能扩大染料的敏化区间,增加了太阳光的利用效率,对电极施加不同的偏压,测试电极产生的瞬态光电流,研究了偏压对光生电荷转移及复合速率的影响,从不同方向照射电极,对阳极光电流影响显著,结合电化学、光电化学原理对这些现象进行了讨论.     

纳米多孔金催化有机反应研究进展

综述了金纳米多孔材料在催化CO和醇的氧化反应、含不饱和键化合物(炔烃、亚胺和α,β-不饱和醛)的加氢还原反应、炔基芳香醛与炔烃的成环反应、氧化脱氢偶联构筑新C—C键反应和C—X(X=B,Si)键形成反应中的应用研究结果.     

Highly efficient protection of alcohols as trityl ethers under solvent-free conditions,and recovery catalyzed by reusable nanoporous MCM-41-SO3H

An efficient method was developed for the protection of alcohols as trityl ethers using triphenylmethanol in the presence of nanoporous MCM-41-SO₃H as a heterogeneous catalyst under solvent-free ball-milling at room temperature. Low catalyst loading, high efficiency, reusability are among the advantages of this new solvent-free and environmentally friendly method. The deprotection of the produced trityl ethers was also efficiently achieved using the same catalyst in wet acetonitrile.