Efficiency enhancement of dye-sensitized solar cells by the addition of an oxidizing agent to the TiO(2) paste.

The addition of various amounts of a strong oxidizing agent (3,5-dinitrosalicyclic acid, DNSA) to TiO2 paste enhances the solar-to-electrical-energy conversion efficiency of the corresponding dye-sensitized solar cells (DSSCs). Maximum performance was obtained from a device that was fabricated by using a TiO2 paste with 2 wt % DNSA, which showed a short-circuit current density of 17.88 mA cm(-2) , an open-circuit voltage of 0.78 V, and an overall conversion efficiency of 9.62 %, which was an improvement in comparison to reference cells without DNSA. This improvement was rationalized in terms of the amount of residual carbon (formed due to the oxidation of binders) remaining on the TiO2 surface. Addition of a larger amount of oxidizing agent led to a smaller amount of residual carbon on the TiO2 surface. This smaller amount of residual carbon enhanced the adsorption of a larger number of dye molecules on the TiO2 surface. The addition of an oxidizing agent facilitated the removal of more residual organic species during the high-temperature calcination process while causing no change in the surface morphology and microstructure of the TiO2 film.

Prediction of rock salt structure of (InN)32 nanoparticles from first principles calculations.

From first principles calculations, we show that (InN)32 nanoparticles favor rock salt structure compared with wurtzite structure in bulk. A phase transition from wurtzite to rock salt structure is known to occur in bulk InN at 12.1 GPa and higher values of pressure for AlN and GaN. However, at the nanoscale we show that this structural transition takes place in (InN)32 without applying pressure. The charge asymmetry value "g" and cation/anion size ratio in InN describe very well this behavior. Similar studies on nanoparticles of AlN and GaN as well as a few other binary compounds such as MgS, AgI, ZnO, and CdSe, however, do not show such a transition. Our results suggest (InN)32 to be a unique candidate as further calculations on a few larger size (InN)n nanoparticles show that a filled cage (two shells) (InN)12@(InN)48 structure of (InN)60 has higher binding energy compared with a rock salt structure of (InN)64 leading to the conclusion that other 3D structures are likely to become favorable over rock salt structure for larger sizes.

Interactions between multiwall carbon nanotubes and poly(diallyl dimethylammonium) chloride: effect of the presence of a surfactant.

The interactions between multiwall carbon nanotubes (MWCNTs) and poly(diallyl dimethylammonium) chloride (PDDA) have been studied in the presence of different ionic and nonionic surfactants, such as sodium dodecyl sulfate (SDS), cetyltrimethylammonium bromide (CTAB), Tween 20, 40, 60, and 80, and Triton X-100. On the basis of scanning electron microscopy (SEM) results, the MWCNT/PDDA sample treated with Triton X-100 has been observed to show good dispersion of nanotubes. This is due to the π-π stacking between the benzene ring of Triton X-100 and the hexagonal carbon rings of nanotubes and better coating of PDDA on MWCNTs, as is confirmed by the Raman studies. Energy dispersive X-ray (EDX) spectroscopic data shows the presence of higher oxygen content in the MWCNTs/PDDA/Triton X-100 sample. The maximum upshift in the C1s peak position and down-shift in the N1s peak position for the MWCNTs/PDDA/Triton X-100 sample has been observed from X-ray photoelectron spectroscopy (XPS) results and is due to the intermolecular charge transfer from carbon in MWCNTs to nitrogen in PDDA. The presence and nature of a surfactant in the MWCNTs/PDDA system has been found to affect their interactions. The above results suggest that the MWCNTs/PDDA/Triton X-100 system is suitable as a metal-free electrocatalyst for the oxygen reduction reaction (ORR) in fuel cells.

Study of ion diffusional motion in ionic liquid-based polymer electrolytes by simultaneous solid state NMR and DTA.

Polymer electrolytes containing ionic liquid (IL), 2-methyl-1,3-dipropylimidazolium dihydrogenphosphate (MDPImH2PO4) have been studied by (1)H solid state NMR and differential thermal analysis (DTA) simultaneously by using a specially designed probe. To the best of our knowledge, this is the first report of its kind for IL based polymer electrolytes. The variation of NMR line width with temperature for the IL and polymer electrolytes shows line narrowing at the glass transition and melting temperature. The onset of long-range ion diffusional motion also takes place at these temperatures and is accompanied by a sudden increase in ionic conductivity value by 2-3 orders of magnitude. The presence of amorphous and crystalline phases in IL-based polymer electrolytes has been observed from X-ray diffraction (XRD) studies, and the amorphous phase is the high conducting phase in these polymer electrolytes. The IL-based polymer electrolytes have been observed to be thermally stable up to 200 °C. The results obtained from ion transport studies have also been supported by Fourier transform infrared (FTIR), XRD, and cyclic voltammetry (CV) studies.

Correlation between ion diffusional motion and ionic conductivity for different electrolytes based on ionic liquid.

Room temperature ionic liquid 2,3-dimethyl-1-hexylimidazolium bis(trifluoromethane sulfonyl)imide (DMHxImTFSI) has been synthesized and used in the preparation of polymer gel electrolytes containing polymethylmethacrylate and propylene carbonate (PC). The onset of ion diffusional motion has been studied by (1)H and (19)F NMR spectroscopy and the results obtained for ionic liquid, liquid electrolytes, and polymer gel electrolytes have been correlated with the ionic conductivity results for these electrolytes in the 100-400 K temperature range. The temperature at which (1)H and (19)F NMR lines show motional narrowing and hence ion diffusional motion starts has been found to be closely related to the temperature at which a large increase in ionic conductivity has been observed for these electrolytes. Polymer gel electrolytes have high ionic conductivity over a wide range of temperatures. Thermogravimetric analysis/differential scanning calorimetry studies show that the ionic liquid (DMHxImTFSI) used in the present study is thermally stable up to 400 degrees C, whereas the addition of PC lowers the thermal stability of polymer gel electrolytes containing the ionic liquid. Different electrolytes have been observed to show high ionic conductivity in different range of temperatures, which can be helpful in the design of polymer gel electrolytes for specific applications.

Polymer electrolytes based on room temperature ionic liquid: 2,3-dimethyl-1-octylimidazolium triflate.

Room temperature ionic liquid (DMOImTf) based upon 2,3-dimethyl-1-octylimidazolium cation and trifluoromethanesulfonate or triflate (CF(3)SO(3))(-) anion has been synthesized and shows conductivity of 5.68 mS/cm and viscosity of 26.4 cP at 25 degrees C. Ion conducting polymer electrolytes based on polymers (poly(ethylene oxide) (PEO) and polyvinylidenefluoride-co-hexafluoropropylene (PVdF-HFP)) and ionic liquid (DMOImTf) were prepared in film form by the casting technique. The conductivity of polymer electrolytes containing 0.5 M LiCF(3)SO(3) in PEO:DMOImTf taken in equal weight ratio increases with the addition of propylene carbonate (PC) while its mechanical stability improved by dispersing nanosize fumed silica. However, polymer electrolytes containing PVdF-HFP and ionic liquid show a high value of conductivity (10(-4)-10(-3) S/cm) alongwith better mechanical stability.

Deleterious influence of hypothyroidism on evolving myocardial infarction in conscious dogs.

To study the influence of hypometabolism on evolving myocardial infarction in a model with intact autoregulation, we investigated 53 awake dogs after coronary artery occlusion. Severe hypothyroidism was induced by the intravenous administration of 131I. Animals were instrumented to obtain hemodynamic measurements, and regional myocardial blood flow was measured with radioactive microspheres. Infarct size was determined by the creatine kinase depletion method, and dysrhythmia analysis was performed from 24-h Holter monitor tapes in animals matched for infarct size. The microarchitecture of hypothyroid myocardium was determined by the electron microscope. Before coronary occlusion, mean systemic pressure in hypothyroid dogs was reduced by 14% and cardiac output reduced by 32%, with no change in left ventricular end-diastolic pressure, first derivative of left ventricular pressure rise, (dP/dt), or heart rate. After coronary occlusion, there was deterioration in hemodynamic measurements in both groups, with lower absolute levels of mean systemic blood pressure and cardiac output obtained in hypothyroid dogs. Hypothyroidism was detrimental to evolving infarction with a 36% increase in infarct size present in hypothyroid dogs (30 +/- 2%) compared to euthyroid controls (22 +/- 3%), P less than 0.05. Dysrhythmias were more severe in hypothyroid dogs. There were no changes in the relationship between regional myocardial blood flow and the extent of infarction after coronary occlusion. Abnormalities in microarchitecture were present in hypothyroid dog myocardium. Severe hypometabolism in this model was associated with alterations in hemodynamics, more severe dysrhythmias and changes in microarchitecture. The combined effect of these alterations resulted in an overall detrimental influence of hypothyroidism on evolving myocardial necrosis in this model.

Electron microscopic studies of saprobic and parasitic forms of Coccidioides immitis.

During studies of both saprobic and parasitic cycles of Coccidioides immitis, we found that the hyphae contained septa with simple pores, Woronin bodies, pinocytotic vesicles and/or lomasomes. The alternating thallic arthroconidia were released by fracturing of the adjacent sterile cells. The endospores were formed by progressive cleavage of the spherules. The taxonomic classification of C. immitis still remains obscure.

Sense organs on the antennal flagellum of psocids (Insecta, Psocoptera).

The sense organs on the antennal flagella of five species of winged psocids belonging to two families of Psocoptera, Psocidae and Leptopsocidae, have been examined, All agree in possessing tactile hairs, thick-walled chemoreceptors and long, porous chemoreceptors. Thin-walled chemoreceptors were identified in all species except Metylophorous novaescotiae. Coeloconic chemoreceptors were present in all species except Echmepteryx hageni. Campaniform sense organs were found only in Metylophorus novaescotiae and Psocus leidyi.

The femoral chordotonal organs of a grasshopper, Orthoptera, Acrididae.

The fine structure of the prothoracic and mesothoracic femoral chordotonal organs of a grasshopper, Romalea microptera, is described. A single chordotonal organ may contain more than 300 sensory units. Each unit includes the cell bodies and dendrites of two neurons, together with sheath cells of several kinds. The cytoplasm of the sheath cells is packed with microtubules and filaments. These cells surround the cell bodies of the neurons and anchor them to the inner surface of the femoral wall. The dendrites from the two neurons are enclosed by a scolopale cell. At the distal end of this cell they traverse the extra-cellular space within the scolopale and their tips are fitted into cavities in the scolopale cap. The ciliary region of each dendrite is dilated for about one fourth of its total length. The cap is embedded in an elongate cap cell which is attached, in turn, to a ligament cell. The ligament cells are, themselves, attached to an apodeme that extends in from the tibia. When the tibia is flexed, the chordotonal organ is stretched and when it is extended, the organ is relaxed. It is postulated that the mass of the dilated region affects the character of the vibration that is induced when the dendrite is stretch or relaxed.