Morphology-Controlled Synthesis and Metalation of Porphyrin Nanoparticles with Enhanced Photocatalytic Performance.

The design and engineering of the size, shape, and chemistry of photoactive building blocks enables the fabrication of functional nanoparticles for applications in light harvesting, photocatalytic synthesis, water splitting, phototherapy, and photodegradation. Here, we report the synthesis of such nanoparticles through a surfactant-assisted interfacial self-assembly process using optically active porphyrin as a functional building block. The self-assembly process relies on specific interactions such as π-π stacking and metalation (metal atoms and ligand coordination) between individual porphyrin building blocks.

Formation mechanism and optimization of highly luminescent N-doped graphene quantum dots.

Photoluminescent graphene quantum dots (GQDs) have received enormous attention because of their unique chemical, electronic and optical properties. Here a series of GQDs were synthesized under hydrothermal processes in order to investigate the formation process and optical properties of N-doped GQDs. Citric acid (CA) was used as a carbon precursor and self-assembled into sheet structure in a basic condition and formed N-free GQD graphite framework through intermolecular dehydrolysis reaction.

Porous one-dimensional nanostructures through confined cooperative self-assembly.

We report a simple confined self-assembly process to synthesize nanoporous one-dimensional photoactive nanostructures. Through surfactant-assisted cooperative interactions (e.g.

Templated photocatalytic synthesis of well-defined platinum hollow nanostructures with enhanced catalytic performance for methanol oxidation.

Hollow metallic nanostructures exhibit important applications in catalysis, sensing, and phototherapy due to their increased surface areas, reduced densities, and unique optical and electronic features. Here we report a facile photocatalytic process to synthesize and tune hollow platinum (Pt) nanostructures. Through hierarchically structured templates, well-defined hollow Pt nanostructures are achieved.

Nanostructured gold architectures formed through high pressure-driven sintering of spherical nanoparticle arrays.

We have demonstrated pressure-directed assembly for preparation of a new class of chemically and mechanically stable gold nanostructures through high pressure-driven sintering of nanoparticle assemblies at room temperature. We show that under a hydrostatic pressure field, the unit cell dimension of a 3D ordered nanoparticle array can be reversibly manipulated allowing fine-tuning of the interparticle separation distance. In addition, 3D nanostructured gold architecture can be formed through high pressure-induced nanoparticle sintering.

Monodisperse porous nanodiscs with fluorescent and crystalline wall structure.

We report a facile solution process to synthesize monodisperse porous nanodiscs through confined molecular self-assembly of surfactants and ZnTPyP. The nanodiscs exhibit trimodal pores with fluorescent and crystalline wall structures, and are potentially important for sorption and separation, sensors, catalytic materials, electrode materials, etc.

Energetics and structural consequences of axial ligand coordination in nonplanar nickel porphyrins.

The effects of ruffling on the axial ligation properties of a series of nickel(II) tetra(alkyl)porphyrins have been investigated with UV-visible absorption spectroscopy, resonance Raman spectroscopy, X-ray crystallography, classical molecular mechanics calculations, and normal-coordinate structural decomposition analysis. For the modestly nonplanar porphyrins, porphyrin ruffling is found to cause a decrease in binding affinity for pyrrolidine and piperidine, mainly caused by a decrease in the binding constant for addition of the first axial ligand; ligand binding is completely inhibited for the more nonplanar porphyrins. The lowered affinity, resulting from the large energies required to expand the core and flatten the porphyrin to accommodate the large high-spin nickel(II) ion, has implications for nickel porphyrin-based molecular devices and the function of heme proteins and methyl-coenzyme M reductase.

Unusual aryl-porphyrin rotational barriers in peripherally crowded porphyrins.

Previous studies of 5,10,15,20-tetraarylporphyrins have shown that the barrier for meso aryl-porphyrin rotation (DeltaG++(ROT)) varies as a function of the core substituent M and is lower for a small metal (M = Ni) compared to a large metal (M = Zn) and for a dication (M = 4H(2+)) versus a free base porphyrin (M = 2H). This has been attributed to changes in the nonplanar distortion of the porphyrin ring and the deformability of the macrocycle caused by the core substituent. In the present work, X-ray crystallography, molecular mechanics (MM) calculations, and variable temperature (VT) (1)H NMR spectroscopy are used to examine the relationship between the aryl-porphyrin rotational barrier and the core substituent M in some novel 2,3,5,7,8,10,12,13,15,17,18,20-dodecaarylporphyrins (DArPs), and specifically in some 5,10,15,20-tetraaryl-2,3,7,8,12,13,17,18-octaphenylporphyrins (TArOPPs), where steric crowding of the peripheral groups always results in a very nonplanar macrocycle.

Origin of the red shifts in the optical absorption bands of nonplanar tetraalkylporphyrins.

The view that the large red shifts seen in the UV-visible absorption bands of peripherally crowded nonplanar porphyrins are the result of nonplanar deformations of the macrocycle has recently been challenged by the suggestion that the red shifts arise from substituent-induced changes in the macrocycle bond lengths and bond angles, termed in-plane nuclear reorganization (IPNR). We have analyzed the contributions to the UV-visible band shifts in a series of nickel or zinc meso-tetraalkylporphyrins to establish the origins of the red shifts in these ruffled porphyrins. Structures were obtained using a molecular mechanics force field optimized for porphyrins, and the nonplanar deformations were quantified by using normal-coordinate structural decomposition (NSD).