Shuttle-like supramolecular nanostructures formed by self-assembly of a porphyrin via an oil/water system

Assembly of Copper Phthalocyanine on TiO2 Nanorod Arrays as Co-catalyst for Enhanced Photoelectrochemical Water Splitting

A photoelectrochemical device was achieved by interfacial self-assembly of macrocyclic π-conjugated copper phthalocyanine (CuPc) on surface of TiO2 nanorod arrays (NRs). The photocurrent density of the elegant TiO2@CuPc NRs photoanode reaches 2.40 mA/cm2 at 1.23 V vs. RHE under the illumination of 100 mW/cm2 from AM 1.5G sun simulator, which is 2.4 times higher than that of the pure TiO2. At the same time, the photoelectrochemical device constructed through this strategy has good stability and the photocurrent density remain almost no decline after 8 h of continuous operation. The Mott-Schottky and LSV curves demonstrate that CuPc act as a co-catalyst for water oxidation and a possible mechanism is proposed for water oxidation based on careful analysis of the detailed results. The holes from VB of TiO2 photogenerated by electrons exciting are consumed by a process in which Cu2+ is oxidized to Cu3+ and Cu4+, and then oxidize water to produce oxygen. CuPc species is considered to be a fast redox mediator to reduce the activation energy of water oxidation in and effectively promote charge separation.

Temperature-induced reversible self-assembly of diphenylalanine peptide and the structural transition from organogel to crystalline nanowires

Controlling the self-assembly of diphenylalanine peptide (FF) into various nanoarchitectures has received great amounts of attention in recent years. Here, we report the temperature-induced reversible self-assembly of diphenylalanine peptide to microtubes, nanowires, or organogel in different solvents. We also find that the organogel in isopropanol transforms into crystalline flakes or nanowires when the temperature increases. The reversible self-assembly in polar solvents may be mainly controlled by electronic and aromatic interactions between the FF molecules themselves, which is associated with the dissociation equilibrium and significantly influenced by temperature. We found that the organogel in the isopropanol solvent made a unique transition to crystalline structures, a process that is driven by temperature and may be kinetically controlled. During the heating-cooling process, FF preferentially self-assembles to metastable nanofibers and organogel. They further transform to thermodynamically stable crystal structures via molecular rearrangement after introducing an external energy, such as the increasing temperature used in this study. The strategy demonstrated in this study provides an efficient way to controllably fabricate smart, temperature-responsive peptide nanomaterials and enriches the understanding of the growth mechanism of diphenylalanine peptide nanostructures.

Porphyrin assemblies via a surfactant-assisted method: from nanospheres to nanofibers with tunable length

In this paper, we report that a porphyrin, zinc 5,10,15,20-tetra(4-pyridyl)-21H,23H-porphine (ZnTPyP), could be organized to form one-dimensional (1D) nanofibers via a surfactant-assisted self-assembly (SAS) method. We disclose that when a chloroform solution of ZnTPyP is dropwise added into an aqueous solution of cetyltrimethylammonium bromide (CTAB), spherical nanostructures are formed at the initial stage. The nanospheres are naturally transformed into 1D nanostructures simply by aging under ambient conditions. Interestingly, by adjusting the volume of the employed ZnTPyP chloroform solution, the length of thus-produced 1D nanoarchitectures could be efficiently controlled. It is disclosed that longer nanofibers could be manufactured when a small volume of chloroform solution of ZnTPyP is involved, while shorter 1D nanospecies could be produced when a large volume of chloroform solution of ZnTPyP is employed. The 1D nanostructures are characterized by UV-visible spectra, scanning electron microscopy, low-resolution transmission electron microscopy, high-resolution transmission electron microscopy, and fast Fourier transformation. A solubility experiment has been carried out to disclose the dispersibility of our ZnTPyP in plain water and in CTAB aqueous solution. On the basis of the experimental facts, an explanation is proposed for these interesting new findings. The investigation provides new opportunities for the controllable assembly of porphyrin-based 1D nanomaterials with tunable length, and it sheds new scientific insights on the molecular assembly process occurring in the SAS system, wherein an oil/water system is used as the assembly medium.

Synthesis of size-controlled monodisperse Pd nanoparticles via a non-aqueous seed-mediated growth

We demonstrated that stepwise seed-mediated growth could be extended in non-aqueous solution (solvothermal synthesis) and improved as an effective method for controlling the uniform size of palladium nanoparticles (Pd NPs) in a wide range. The monodisperse Pd NPs with the size of about 5 nm were synthesized by simply reducing Pd(acac)2 with formaldehyde in different organic amine solvents. By an improved stepwise seed-mediated synthesis, the size of the monodisperse Pd NPs can be precisely controlled from approximately 5 to 10 nm. The as-prepared Pd NPs could self assemble to well-shaped superlattice crystal without size selection process.

Ag/AgBr/graphene oxide nanocomposite synthesized via oil/water and water/oil microemulsions: a comparison of sunlight energized plasmonic photocatalytic activity

In this article, we report that Ag/AgBr nanostructures and the corresponding graphene oxide (GO) hybridized nanocomposite, Ag/AgBr/GO, could be facilely synthesized by means of a surfactant-assisted assembly protocol, where an oil/water microemulsion is used as the synthesis medium. We show that thus-produced nanomaterials could be used as highly efficient and stable plasmonic photocatalysts for the photodegradation of methyl orange (MO) pollutant under sunlight irradiation. Compared with the bare Ag/AgBr nanospecies, Ag/AgBr/GO displays distinctly enhanced photocatalytic activity. More importantly, the as-prepared nanostructures exhibit higher photocatalytic activity than that of the corresponding Ag/AgBr-based nanomaterials synthesized viaa water/oil microemulsion and than that of the corresponding Ag/AgCl-based nanospecies synthesized by an oil/water microemulsion. An explanation has been proposed for these interesting findings. Our results suggest that thus-manufactured Ag/AgBr/GO plasmonic photocatalysts are promising alternatives to the traditional UV light or visible-light driven photocatalysts.