TiO2 coated urchin-like SnO2 microspheres for efficient dye-sensitized solar cells

Urchin-like SnO2 microspheres have been grown for use as photoanodes in dye-sensitized solar cells （DSSCs）. We observed that a thin layer coating of TiO2 on urchin-like SnO2 microsphere photoanodes greatly enhanced dye loading capability and light scattering ability, and achieved comparable solar cell per- formance even at half the thickness of a typical nanocrystalline TiO2 photoanode. In addition, this photoanode only required attaching -55% of the amount of dye for efficient light harvesting compared to one based on nanocrystalline TiO2. Longer decay of transient photovoltage and higher charge recombination resistance evidenced from electrochemical impedance spectroscopy of the devices based on TiO2 coated urchin-like SnO2 revealed slower recombination rates of electrons as a result of the thin blocking layer of TiO2 coated on urchin- like SnO2. TiO2 coated urchin-like SnO2 showed the highest value （76.1 ms） of electron lifetime （＇r） compared to 2.4 ms for bare urchin-like SnO2 and 14.9 ms for nanocrystalline TiO2. TiO2 coated SnO2 showed greatly enhanced open circuit voltage （Voc）, short-circuit current density （Jsc） and fill factor （FF） leading to a four-fold increase in efficiency increase compared to bare SnO2. Although TiO2 coated urchin-like SnO2 showed slightly lower cell efficiency than nanocrystalline TiO2, it only used a half thickness of photoanode and saved -45% of the amount of dye for efficient light harvesting compared to normal nanocrystalline TiO2.     

Enhanced performance in dye-sensitized solar cells via carbon nanofibers-platinum composite counter electrodes

A composite counter electrode (CE) made of electrospun carbon nanofibers (ECNs) and platinum (Pt) nanoparticles has been demonstrated for the first time to improve the performance of dye-sensitized solar cells (DSCs). The new ECN-Pt composite CE exhibited a more efficient electro-catalytic performance with lower charge transfer resistance (R(ct)), larger surface area, and faster reaction rate than those of conventional Pt. It reduced the overall series resistance (R(se)), decreased dark saturation current density (J(0)) and increased shunt resistance (R(sh)) of the DSCs, thereby leading to a higher fill factor (FF) and larger open circuit voltage (V(oc)). The reduced electron transport resistance (R(s)) and faster charge transfer rate in the CE led to a smaller overall cell series resistance (R(se)) in the ECN-Pt composite based DSCs. The DSCs based on an ECN-Pt CE achieved a η of ～8%, which was improved over those of pure Pt or ECN based cells.     

Economic contribution of hunting expenditure to the southern United States of America

Millions of people in United States of America (U.S.) participate in hunting activities which benefit the U.S. economy and help promote conservation and environmental goals. The 2011 National Survey of Fishing, Hunting and Wildlife-Associated RecreationSurvey reported that 13.7 million people aged 16 and above participated in recreational hunting activities, spending $33.7 billion on trips and equipment. This paper reports quantified economic contributions of hunting and its sub-activity expenditure for the thirteen states in the U.S. South by calculating total gross output, employment, total income, personal income and value-added. Input–output models were developed for each State, to determine the direct, indirect, and induced impacts of expenditure derived from hunting. Comparison at broad activity (hunting) and sub-activity (type of game etc.) levels revealed that there were differences in the individual states’ economies, and that levels of expenditure affected the total economic contribution of hunting activities. Generally, states with larger economies benefited from greater multiplier effects while the total economic contribution, when expressed as a percentage of the economy, was greater for states with smaller economies.     

Chemical synthesis of anisotropic nanocrystalline Sb2Te3 and low thermal conductivity of the compacted dense bulk

We describe a one-step, one-pot non-aqueous route for the synthesis of Sb2Te3 nanocrystals with hexagonal shape and highly anisotropic nanostructures. The as-prepared nanostructures were characterized by XRD, TEM and HRTEM. The effect of the stabilizers on the nanocrystal morphology has been discussed in detail. We have studied the thermal conductivity of the compacted bulk from the Sb2Te3 nanostructures. The results indicated that a very low thermal conductivity of about 1 W/mK at 300 K, comparing to 4.7 W/mK of the polycrystalline bulk, was achieved. The results indicated that nanostructured Sb2Te3 is potentially a good candidate for engineered nanocomposites that can lead to high thermoelectric figure-of-merit.     

One dimensional nanostructure/nanoparticle composites as photoanodes for dye-sensitized solar cells

Dye-sensitized solar cells (DSCs) show potential as a low cost alternative to silicon solar cells. Power conversion efficiencies exceeding 12% have been achieved for DSCs. Typical DSCs are based on TiO(2) nanoparticle photoanodes, which have numerous grain boundaries, surface defects and trap states as electrons transport from one particle to the other. Such defects and trap states increase back charge transfer (charge recombination) from the photoanode to electrolyte. One dimensional (1D) nanostructures such as nanofibers, nanorods, nanowires, and nanotubes can offer direct and fast electron transport to the electron collecting electrode. However, these 1D nanostructures have a major disadvantage of having insufficient surface area and inefficient dye attachment. To solve this challenge, mixtures of TiO(2) nanoparticles and 1D nanostructures (e.g. nanofibers, nanorods, nanowires, and nanotubes) are used to take advantage of the large surface area of nanoparticles and efficient charge transport of 1D nanostructures. In this article, we review the recent developments in using mixtures of 1D nanostructures and nanoparticles as photoanodes for efficient DSCs. Various randomly oriented and vertically aligned 1D nanostructures and their composites with nanoparticles are discussed. Future increase of efficiency in DSCs using 1D nanostructure/nanoparticle composites will rely on the optimization of diameters of 1D nanostructures, control of ratios of 1D nanostructures and nanoparticles, increase of crystallinity, and reduction of surface defects on the 1D nanostructures. This work will provide guidance for designing and growing appropriate 1D nanostructures, and combining them with nanoparticles at an optimal ratio for efficient DSCs.     

Effects of Thermal Annealing on the Formation of Buried <Emphasis Type="Italic">β</Emphasis>-SiC by Ion Implantation

A systematic study of the formation of buried β-SiC structures by carbon ion implantation into Si followed by high-temperature thermal annealing has been carried out. A high fluence of carbon ions (8 × 10¹⁷ atoms/cm²) was implanted at 65 keV energy. Formation of the crystalline β-SiC phase was monitored by Fourier-transform infrared (FTIR) spectroscopy, x-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM) techniques. The implanted samples were annealed at 900°C and 1100°C to observe the effects of annealing temperature on the formation of crystalline β-SiC. Formation of crystalline β-SiC was clearly observed in the sample annealed at 1100°C in a flowing nitrogen environment for a period of 1 h. Graphitic carbon clusters were observed at the implanted carbon profile peak position by XPS depth profile measurements. Various structural defects such as grain boundaries were also visualized in the annealed sample by high-resolution TEM.     

Edge-Based Close-Range Digital Photogrammetry for Structural Deformation Measurement

This paper proposes a close-range digital photogrammetric system based on edge detection for structural deformation measurement. Different from traditional photogrammetric applications using discrete points, continuous edges in digital images are used here as the controlling feature in this new system. This makes it possible to acquire spatially intensive information. The system uses several digital images of the structure, taken from a number of different stations before and after the deformation is induced. Then, an image-matching algorithm based on the coplanarity condition developed here is applied to establish spatial relationships of the interested edges, identified by using a new high-precision method. These relationships are subsequently employed to acquire full-field deformation measurement of the structure. A series of experiments was conducted in the laboratory to investigate the capability of the new photogrammetric system. Results show that the system is highly accurate and suitable for structural deformation measurement. It offers noncontact, full-field, and spatially intensive measurement, in contrast with conventional contact and point-measurement.     

A nucleation mechanism leading to stacking of lamellar crystals in polymer thin films

Systematic studies based on well‐controllable model systems aim at understanding how crystallization from a melt or solution of randomly coiled polymers leads to the formation of mono‐lamellar crystals. However, besides mono‐lamellar crystals also various other morphologically simple but yet not well understood structures are found. In particular, stacks of correlated lamellar crystals have been observed since the early days of the study of polymer crystallization. Here, we demonstrate that a recently proposed mechanism of self‐induced nucleation within lamellar crystals provides a possibility to explain how in such stacks lamellar crystals can be correlated. Examining various polymer systems, we show that the probability for generating self‐induced nuclei depends on the morphology of an initiating dendritic basal lamellar crystal. In addition, we provide evidence that this self‐induced nucleation mechanism, together with a high rate of transport of molten polymer to the fold surface, may allow the formation of polymer crystals with similar size in all three dimensions, containing a large number of superposed correlated lamellae. © 2019 The Authors. Polymer International published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.