Ethanol-soluble amphiphilic TiO(2) nanoparticles (NPs) of average diameter ∼9 nm were synthesized, and an α-terpineol-based TiO(2) paste was readily prepared from them in comparatively few steps. When used for fabrication of photoelectrodes for dye-sensitized solar cells (DSSCs), the paste yielded highly transparent films and possessing greater-than-typical, thickness-normalized surface areas. These film properties enabled the corresponding DSSCs to produce high photocurrent densities (17.
View Article and Find Full Text PDFFour heterobimetallic U(vi)/M(ii) (M = Mn, Co, Cd) carboxyphosphonates have been synthesized. M(2)[(UO(2))(6)(PO(3)CH(2)CO(2))(3)O(3)(OH)(H(2)O)(2)]·16H(2)O (M = Mn(ii), Co(ii), and Cd(ii)) adopt cubic three-dimensional network structures with large cavities approximately 16 Å in diameter that are filled with co-crystallized water molecules. [Cd(3)(UO(2))(6)(PO(3)CH(2)CO(2))(6)(H(2)O)(13)]·6H(2)O forms a rhombohedral channel structure with hydrated Cd(ii) within the channels.
View Article and Find Full Text PDFMetal-organic frameworks--a class of porous hybrid materials built from metal ions and organic bridges--have recently shown great promise for a wide variety of applications. The large choice of building blocks means that the structures and pore characteristics of the metal-organic frameworks can be tuned relatively easily. However, despite much research, it remains challenging to prepare frameworks specifically tailored for particular applications.
View Article and Find Full Text PDFDespite its high refractive index sensitivity, localized surface plasmon resonance (LSPR) spectroscopy has been generally restricted to large biological analytes. Sensing of smaller molecules is a compelling target for this technique; in particular, LSPR spectroscopy could be utilized to detect hazardous or toxic gases and manage industrial processes involving gaseous chemicals. Here, we report sensing of pure gases over Ag nanoparticles using LSPR spectroscopy, where the detected changes in bulk refractive index are <5 × 10(-4) refractive index units (RIU).
View Article and Find Full Text PDFThe emergence of metal-organic frameworks (MOFs) as functional ultrahigh surface area materials is one of the most exciting recent developments in solid-state chemistry. Now constituting thousands of distinct examples, MOFs are an intriguing class of hybrid materials that exist as infinite crystalline lattices with inorganic vertices and molecular-scale organic connectors. Useful properties such as large internal surface areas, ultralow densities, and the availability of uniformly structured cavities and portals of molecular dimensions characterize functional MOFs.
View Article and Find Full Text PDFA ZIF-8 thin film-based Fabry-Pérot device has been fabricated as a selective sensor for chemical vapors and gases. The preparation of the ZIF-8 thin film and a series of ZIF-8 thin films of various thicknesses grown on silicon substrates are presented.
View Article and Find Full Text PDFSeparations of CO(2)/CH(4), CO(2)/N(2), and O(2)/N(2) mixtures were studied in three porous coordination polymers made of the same carborane ligand and Co(ii) nodes. High selectivities for CO(2) over CH(4) ( approximately 47) and CO(2) over N(2) ( approximately 95) were obtained, especially in the material with coordinated pyridine. Unusual selectivity for O(2) over N(2) (as high as 6.
View Article and Find Full Text PDFNickel bis(dicarbollide) is used as a fast, one-electron outer sphere redox couple in dye-sensitized solar cells. Device performances with this anionic shuttle are investigated with different electrolyte concentrations and additives, using only 0.030 M of the Ni(III) bis(dicarbollide) to efficiently regenerate the ruthenium dye.
View Article and Find Full Text PDFWe report direct measurements of the excess polarizability volumes of butadiyne-bridged zinc porphyrin dimers at singly beta-to-beta (1Zn) and doubly beta-to-beta (2Zn) positions using the transient dc photoconductivity (TDCP) technique. The excess polarizability volumes of the singlet exciton for 1Zn and 2Zn are 110 and 270 A(3), respectively, while those of the triplet exciton are approximately 100 A(3) for both dimers. Our measurements suggest that the singlet exciton is mainly localized on one porphyrin subunit for 1Zn, similar to the case for the porphyrin monomer.
View Article and Find Full Text PDFA series of cobalt-containing redox couples, based on [Co(1,10-phenanthroline)(3)](ClO(4))(2) and its derivatives, were prepared for use as regenerators/shuttles in dye-sensitized solar cells featuring modified TiO(2) photoelectrodes. Surface modification and trap-state passivation of the TiO(2) nanoparticle film electrodes were accomplished via atomic layer deposition of an ultrathin alumina coating. Electron lifetimes were then extracted from open-circuit voltage decay measurements.
View Article and Find Full Text PDFA diimide based porous organic polymer (POP) post-synthetically reduced with lithium metal demonstrates a drastic increase in selectivity for carbon dioxide over methane.
View Article and Find Full Text PDFPhotoinduced electron transfer in a self-assembled supramolecular ladder structure comprising oligomeric porphyrin rails and ligated dipyridyltetrazine rungs was characterized by transient absorption spectroscopy and transient direct current photoconductivity to be mainly from an oligomer (rail) to the center of a terminal tetrazine (rung), with the remaining hole being delocalized on the oligomer and subsequent charge recombination in 0.19 ns.
View Article and Find Full Text PDFMetal-organic frameworks (MOFs), a hybrid class of materials comprising inorganic nodes and organic struts, have potential application in many areas due to their high surface areas and uniform pores and channels. One of the key challenges to be overcome in MOF synthesis is the strong propensity for catenation (growth of multiple independent networks within a given crystal), as catenation reduces cavity sizes and diminishes porosity. Here we demonstrate that rational design of organic building blocks, which act as strut-impervious scaffolds, can be exploited to generate highly desired noncatenated materials in a controlled fashion.
View Article and Find Full Text PDFA new, twofold interpenetrated metal-organic framework (MOF) material has been synthesized that demonstrates dramatic steps in the adsorption and hysteresis in the desorption of CO(2). Measurement of the structure by powder X-ray diffraction (PXRD) and pair distribution function (PDF) analysis indicates that structural changes upon CO(2) sorption most likely involve the interpenetrated frameworks moving with respect to each other.
View Article and Find Full Text PDFTwo porphyrin-based dyes with carboxylic acid tethers of differing acidity in both protonated and deprotonated forms were examined on ZnO nanotube electrodes. All of the dyes have similar surface coverage, but only the more acidic dye in the acid form injects electrons well; this dye is the only one that corrodes the ZnO. In control experiments on TiO(2) nanoparticle electrodes, both dyes load and inject in protonated and deprotonated forms.
View Article and Find Full Text PDFA zinc porphyrin derivative (2) and zinc porphyrin-bodipy dyad (3) have been prepared and applied to dye-sensitized solar cells (DSSCs). On the basis of absorption and fluorescence excitation spectra, dyad 3 efficiently transfers energy from the bodipy to zinc porphyrin constituent. The 3-sensitized solar cell demonstrates higher solar spectral coverage, based on incident photon to current efficiency (IPCE) spectra, and an improved power conversion efficiency (eta = 1.
View Article and Find Full Text PDFA new strut containing an imidazolium tetracarboxylic acid core has been successfully incorporated into a microporous material using paddlewheel-coordinated copper(II) ions as nodes. Sorption studies conducted on this permanently microporous material imply that it can separate carbon dioxide from methane with high selectivity.
View Article and Find Full Text PDFSolvent-induced excited-state configuration mixing in a Pt(II) diimine chromophore with phenylene ethynylene containing acetylide ligands, [Pt((t)Bu2bpy)(PE3)2] (1), was characterized by nanosecond transient absorption spectroscopy and transient dc photoconductivity (TDCP). The mixing is a result of closely spaced triplet charge transfer (3CT) and intraligand-localized (3IL) triplet energy levels that are finely tuned with solvent polarity as ascertained by their parent model chromophores [Pt((t)Bu2bpy)(PE1)2] (2) and [Pt(P2)(PE3)2] (3), respectively. The absorption difference spectrum of the mixed triplet state is dramatically different from those of the 3CT and 3IL state model chromophores.
View Article and Find Full Text PDFA noncatenated, Zn-based metal-organic framework (MOF) material bearing silyl-protected acetylenes was constructed and postsynthetically modified using "click" chemistry. Using a solvent-based, selective deprotection strategy, two different organic azides were "clicked" onto the MOF crystals, resulting in a porous material whose internal and external surfaces are differently functionalized.
View Article and Find Full Text PDFSolution-phase transient dc photoconductivity (TDCP) measurements are used to address the question of exciton localization/delocalization in strongly coupled oligomeric porphyrins and in well-defined, higher-order assemblies of oligomers (ladder and prism assemblies). The approach used is determination of the excited-state excess polarizability volume, Delta alpha(V)--a quantity known to report on exciton delocalization. The measurements reveal for the oligomers that singlet excitons are substantially delocalized but that triplet excitons are much more localized.
View Article and Find Full Text PDFA Zn-based, mixed-ligand (pillared paddlewheel), metal-organic framework (MOF) has been covalently and quantitatively decorated with free carboxylic acids to demonstrate the utility of covalent post-synthesis modification in the construction of otherwise inaccessible carboxy-functionalized MOFs.
View Article and Find Full Text PDFWe have fabricated titanium dioxide based dye-sensitized solar cells that incorporate corrosion-protected silver nanoparticles as plasmonic optical elements of the photoelectrode. The thickness of the TiO(2) layer separating the dye from the nanoparticles has been systematically varied using atomic layer deposition. Over the range of TiO(2) coating thicknesses examined (2 to 8 nm) there is clear enhancement of the dye extinction when plasmonic particles are present, with the enhancement increasing as the TiO(2) thickness decreases.
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