Electrochemical Synthesis of Cu2O Concave Octahedrons with High-Index Facets and Enhanced Photoelectrochemical Activity.

High-index-faceted nano-/microcrystals exhibit enhanced catalytic activity and can thus serve as new-generation catalysts owing to their high density of low-coordinated atoms, leading to significantly enhanced catalytic activity. In this study, an effective electrochemical approach termed cyclic scanning electrodeposition (CSE) was developed to convert a thin Cu film into Cu2O concave octahedrons enclosed by 24 {344} high-index facets at room temperature with high yield and high throughput. The formation mechanism and the role of each ion in the electrolyte were systematically studied, which facilitated the design of a high-index-faceted metal/metal oxide through CSE. We also presented a general formula to identify the structure of an individual crystal enclosed by {khh} high-index facets based on the crystals oriented along three low-index zone axes and imaged by transmission electron microscopy. Experimental results demonstrated the Cu2O concave octahedrons to be highly efficient, cost-effective catalysts for photoelectrochemical hydrogen production. This new technology is a promising route for the synthesis of metal or metal oxide crystals with high activity and has a great potential for several advanced applications, such as clean energy conversion.

Electrochemical synthesis to convert a Ag film into Ag nanoflowers with high electrocatalytic activity.

The cyclic scanning electrodeposition method was proposed to convert a thin Ag film into nanocrystals (NCs) with various shapes including nanoflowers, nanorods, dendrites, decahedrons, and icosahedrons. The flower-like Ag NCs exhibit a remarkably enhanced catalytic activity for electro-oxidation of glucose.

The study of electrical conductivity and diffusion behavior of water-based and ferro/ferricyanide-electrolyte-based alumina nanofluids.

Nanofluids are liquids containing suspensions of solid nanoparticles and have attracted considerable attention because they undergo substantial mass transfer and have many potential applications in energy technologies. Most studies on nanofluids have used low-ionic-strength solutions, such as water and ethanol. However, very few studies have used high-ionic-strength solutions because the aggregation and sedimentation of nanoparticles cause a stability problem. In this study, a stable water-based alumina nanofluid was prepared using stirred bead milling and exhibits a high electrical conductivity of 2420 µS/cm at 23 °C and excellent stability after five severe freezing-melting cycles. We then developed a process for mixing the water-based nanofluid with a high-ionic-strength potassium ferro/ferricyanide electrolyte and sodium dodecyl sulfate by using stirred bead milling and ultrasonication, thus forming a stable electrolyte-based nanofluid. According to the rotating disk electrode study, the electrolyte-based alumina nanofluid exhibits an unusual increase in the limiting current at high angular velocities, resulting from a combination of local percolation behavior and shear-induced diffusion. The electrolyte-based alumina nanofluid was demonstrated in a possible thermogalvanic application, since it is considered to be an alternative electrolyte for thermal energy harvesters because of the increased electrical conductivity and confined value of thermal conductivity.

Induction of Apoptosis in Endometrial Cancer (Ishikawa) Cells by Pogostemon cablin Aqueous Extract (PCAE).

Pogostemon cablin (PC) is a traditional herbal medicine used in the treatment of the common cold, nausea, diarrhea, and even for headaches and fever. However, the mechanisms underlying the anti-proliferative activity of PC in endometrial cancer (EC) cells have yet to be fully elucidated. This study investigated the anticancer effects of an aqueous extract of Pogostemon cablin (PCAE), specifically induced apoptosis in EC (Ishikawa) cells. Proliferation of EC cells following exposure to PCAE was assessed by an MTT assay. DNA content and the induction of cell cycle apoptosis were analyzed by flow cytometry (FACS Calibur). Protein caspase-3 and, -9 as well as AIF were investigated using Western blot. Our results demonstrate growth inhibition of Ishikawa cells by PCAE. Furthermore, caspase-3 activity caused PCAE-treated cell lines to accumulate in apoptosis. Gene expression profiling (GEP) results further suggest that, in addition to its known effects with regard to EC prevention, PCAE may also exert antitumor activity on established EC cells. Many previous studies have identified the chemo-preventive effects of natural plant materials and the potential role of these materials in chemotherapy. This current study used human EC Ishikawa cells to investigate the anti-tumor effects of PCAE in EC cells. Our results demonstrate that PCAE inhibits the growth of cancer cells and induces apoptosis, which suggests the potential applicability of PCAE as an antitumor agent.

A significant improvement in the electrocatalytic stability of N-doped graphene nanosheets used as a counter electrode for [Co(bpy)3](3+/2+) based porphyrin-sensitized solar cells.

A significant improvement in efficiency is achieved for porphyrin (YD2-o-C8) based dye-sensitized solar cells, coupled with [Co(bpy)3](3+/2+) mediator electrolyte. However, the poison of the counter electrode (CE) by the [Co(bpy)3](3+/2+) mediator remains a significant barrier to producing a reliable high-performance device. In this paper, nitrogen-doped graphene nanosheets (NG) are produced using a low-cost solution-based process and are used as the CE for [Co(bpy)3](3+/2+) based porphyrin-sensitized solar cells. These produce significantly better electrocatalytic activity than the commonly used Pt CE. The superior performance is a result of the increased number of catalytic sites and the wettable surface that is caused by the substitution of pyridinic and pyrrolic N into the carbon-conjugated lattice. To the authors' best knowledge, the significantly improved cycling stability (>1000 times) of NG CE for [Co(bpy)3](3+/2+) redox complexes is demonstrated for the first time.

A short-range ordered-disordered transition of a NiOOH/Ni(OH)2 pair induces switchable wettability.

By virtue of its amorphous structure with a short-range order feature, the inorganic nanoporous nickel oxyhydroxide (NiOOH) can reversibly and rapidly switch wettability by alternate treatments of environmental chamber (superhydrophobic) and UV/ozone (superhydrophilic). The switchable mechanism of the NiOOH/Ni(OH)2 pair arising from its exceptional intrinsic short-range order-disorder transition together with chemical composition change is highlighted for the first time, which significantly differs from the current stimuli-responsive materials. This distinct multifunctional thin film not only possesses reversible wettability but also is optically patternable/repairable and electrically conductive, which could be applicable in the manufacturing of various micro- and nanostructures. We demonstrate this potential in the rewritable two-dimensional (2D) microfluidic channels and wetting-contrast enhanced selective electroplating.

High electrocatalytic and wettable nitrogen-doped microwave-exfoliated graphene nanosheets as counter electrode for dye-sensitized solar cells.

In this paper, high electrocatalytic and wettable nitrogen-doped microwave-exfoliated graphene (N-MEG) nanosheets are used as Pt-free counter electrode (CE) for dye-sensitized solar cells (DSSCs). A low cost solution-based process is developed by using cyanamide (NH2 CN) at room temperature and normal pressure. The pyrrolic and pyridinic N atoms are doped into the carbon conjugated lattice to enhance electrocatalytic activity. N-MEG film having N-doping active sites and large porosity provides a wettable surface to facilitate electrolyte diffusion so that improves fill factor. Moreover, the control of the air exposure time after completing N-MEG film is found to be crucial to obtain a reliable N-MEG CE. A high DSSC efficiency up to 7.18% can be achieved based on N-MEG CE, which is nearly comparable to conventional Pt CE.

Highly conductive and low cost Ni-PET flexible substrate for efficient dye-sensitized solar cells.

The highly conductive and flexible nickel-polyethylene terephthalate (Ni-PET) substrate was prepared by a facile way including electrodeposition and hot-press transferring. The effectiveness was demonstrated in the counter electrode of dye-sensitized solar cells (DSSCs). The Ni film electrodeposition mechanism, microstructure, and DSSC performance for the Ni-PET flexible substrate were investigated. The uniform and continuous Ni film was first fabricated by electroplating metallic Ni on fluorine-doped tin oxide (FTO) and then intactly transferred onto PET via hot-pressing using Surlyn as the joint adhesive. The obtained flexible Ni-PET substrate shows low sheet resistance of 0.18Ω/□ and good chemical stability for the I(-)/I(3-) electrolyte. A high light-to-electric energy conversion efficiency of 7.89% was demonstrated in DSSCs system based on this flexible electrode substrate due to its high conductivity, which presents an improvement of 10.4% as compared with the general ITO-PEN flexible substrate. This method paves a facile and cost-effective way to manufacture various metals on a plastic nonconducive substrate beneficial for the devices toward flexible and rollable.

Functions of self-assembled ultrafine TiO2 nanocrystals for high efficient dye-sensitized solar cells.

In this paper, we demonstrate a simple approach of self-assembled process to form a very smooth and compacted TiO2 underlayer film from ultrafine titanium oxide (TiO2) nanocrystals with dimension of 4 nm for improving the electrical properties and device performances of dye-sensitized solar cells (DSSCs). Because the TiO2 film self-assembles by simply casting the TiO2 on fluorine-doped tin oxide (FTO) substrate, it can save a lot of materials in the process. As compared with control DSSC without the self-assembled TiO2 (SA-TiO2) layer, short-circuit current density (Jsc) improves from 14.9 mA/cm(2) for control DSSC to 17.3 mA/cm(2) for masked DSSC with the SA-TiO2 layer. With the very smooth SA-TiO2 layer, the power conversion efficiency is enhanced from 8.22% (control) to 9.35% for the DSSCs with mask and from 9.79% (control) to 11.87% for the DSSCs without mask. To explain the improvement, we have studied the optical properties, morphology, and workfunction of the SA-TiO2 layer on FTO substrate as well as the impedance spectrum of DSSCs. Importantly, we find that the SA-TiO2 layers have better morphology, uniformity, and contact with FTO electrode, increased workfunction and optical transmission, as well as reduced charge recombination at the contact of FTO substrate contributing to the improved device performances. Consequently, our results show that the simple self-assembly of TiO2 ultrafine nanocrystals forms a very good electron extraction layer with both improved optical and electrical properties for enhancing performances of DSSCs.

Direct electroplated metallization on indium tin oxide plastic substrate.

Looking foward to the future where the device becomes flexible and rollable, indium tin oxide (ITO) fabricated on the plastic substrate becomes indispensable. Metallization on the ITO plastic substrate is an essential and required process. Electroplating is a cost-effective and high-throughput metallization process; however, the poor surface coverage and interfacial adhesion between electroplated metal and ITO plastic substrate limits its applications. This paper develops a new method to directly electroplate metals having strong adhesion and uniform deposition on an ITO plastic substrate by using a combination of 3-mercaptopropyl-trimethoxysilane (MPS) self-assembled monolayers (SAMs) and a sweeping potential technique. An impedance capacitive analysis supports the proposed bridging link model for MPS SAMs at the interface between the ITO and the electrolyte.

Reliable contact fabrication on nanostructured Bi2Te3-based thermoelectric materials.

A cost-effective and reliable Ni-Au contact on nanostructured Bi2Te3-based alloys for a solar thermoelectric generator (STEG) is reported. The use of MPS SAMs creates a strong covalent binding and more nucleation sites with even distribution for electroplating contact electrodes on nanostructured thermoelectric materials. A reliable high-performance flat-panel STEG can be obtained by using this new method.