Dye-sensitized solar cells (DSSCs) have attracted extensive interest in past decade as a promising candidate for the future generation of cost-effective photovoltaic solar cells. [1][2][3][4][5] Since the first demonstration of 10.4% photoconversion efficiency on TiO 2 -based DSSC, [6] intensive work in DSSC research has been devoted to the synthetic chemistry and structural and photovoltaic characterization of mesoporous nanocrystalline TiO 2 materials. [7][8][9] In contrast, other metal oxide semiconductors, such as tin and zinc oxides, have received less attention, though they have required band-gap widths and photoelectrochemical properties as TiO 2 . In fact, SnO 2 has at least two advantageous features compared to TiO 2 for DSSC applications: its higher electron mobility ($100-200 cm 2 V À1 S À1[10]) than TiO 2 ($0.1-1.0 cm 2 V À1 S À1[11]), suggesting a faster diffusion transport of photoinduced electrons in SnO 2 than in TiO 2 ; and its larger band gap (3.6 eV) than anatase TiO 2 (3.2 eV), which would create fewer oxidative holes in the valence band, so as to facilitate the long-term stability of DSSCs. However, SnO 2 -based DSSCs were developed with less success, and the conversion efficiencies of SnO 2 photoelectrodes reported so far are much less than those of TiO 2 . [12,13]

Biosilica with a highly complex and intricate structure can be formed by a diatom under physiological conditions in the presence of silaffins. Herein, the biosilicification process in vivo is mimicked. A natural cationic polypeptide, protamine, was for the first time utilized in vitro to inspire and template silica formation at ambient temperature and neutral pH conditions. The silica-precipitating and templating effect of protamine was first tentatively elucidated. Then, this biomimetic silicification process was performed on the outer surface of liquid-core alginate (Alg) capsules in which β-glucuronidase (GUS) was preencapsulated. An alginate/protamine/silica (APSi) hybrid capsule with a distinct liquid core-solid shell structure was thus fabricated. The rigid, mesoporous silica shell dramatically inhibited the swelling of the capsule and effectively enhanced the mass transfer of substrates and products. Meanwhile, the biocompatible polysaccharide liquid core created a benign microenvironment and well preserved the three-dimensional structure of GUS. The stability of encapsulated GUS was significantly enhanced after silicification, and no loss in activity was found after 10 reaction cycles. Moreover, the relative activity of GUS encapsulated in APSi capsules reached 125%, not only exceeding that encapsulated in Alg capsules but also being higher than that of the free enzyme.

The structure of iron pentacarbonyl, Fe(CO)5, solvated in various solvents has been investigated by FTIR measurements and density functional theory (DFT) calculations. The primary focus rested on the solvation properties of iron pentacarbonyl in aromatic solvents ranging from benzene to increasingly fluorinated derivatives. While, in the gas phase, most iron pentacarbonyl molecules have D 3 h symmetry, about 60−90% of them have C 2 v or C 4 v symmetry in aromatic solvents at room temperature. The C 4 v structure exists in the gas phase as a transition state during a Berry pseudorotation. In solution, this transition state is stabilized by interaction with a solvent molecule located trans to the apical ligand of Fe(CO)5(∼C 4 v ), forming a weakly interacting solute−solvent complex. Benzene, for instance, does not coordinate to the iron with its π-system but with one of its aryl hydrogens. The equilibrium populations of conformers with various symmetries were investigated through (i) calculations of the Gibbs free energy for D 3 h , C 2 v , and C 4 v conformers of Fe(CO)5 after DFT structure refinement of the Fe(CO)5−solvent complex, (ii) experimental FTIR data in combination with theoretical IR absorption intensity values from our DFT calculations, and (iii) entirely experimental temperature-dependent FTIR data. The configuration population measurements relied on an absorption band around 2113 cm-1, which was assigned to a CO-stretching vibration of C 2 v and C 4 v symmetry. While this stretching mode is exclusively Raman active in D 3 h symmetry, it becomes increasingly IR active as the symmetry of Fe(CO)5 is broken by solvation. The absorption band is about a factor 800 weaker than the ones around 2000 cm-1, which are usually considered in IR spectroscopy of CO vibrations. We demonstrate that, despite its small intensity, this mode carries quantitative spectroscopic information about the conformer distribution.

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