Theoretical characterisation of highly efficient dye-sensitised solar cells

Molecular electronic structure calculations, employing density functional theory (DFT) and time-dependent density functional theory (TD-DFT) methodologies, have been carried out to improve the performance of the synthesised dye YD2-o-C8 which is characterised by 11.9%–12.7% efficiencies. We aimed to narrow the band gap of YD2-o-C8 to extend the light-harvesting region to near-infrared (NIR). This was done by incorporating Cd instead of Zn onto the porphyrin ring and elongating the length of π-conjugation by adding ethynylene link and anthracene unit, so that the performances of the suggested cells could be expected to exceed the 11.9%–12.7% efficiencies with TiO₂, ZnO₂, and WO₃ oxide electrodes. The effects of modifying the central metal and elongating the length of π-conjugation on cell performance are confirmed in terms of frontier molecular orbital (FMO) energy gaps, density of states (DOS), molecular electrostatic potentials (MEPs), non-linear optical (NLO) properties, ultraviolet–visible (UV–vis) electronic absorption, and ¹H nuclear magnetic resonance chemical shifts. Increasing the length of π-conjugation of the D–π–A dyes leads to increasing the DOS near Fermi levels, more active NLO performance, strong response to the external electric field, delocalisation of the negative charges near the anchoring groups, deep electron injection, suppressing macrocycle aggregation, active dye regeneration, and inhibited dye recombination. The calculated band gap/eV of the present DMP-Zn is correlated with the experimental (E_1/2(oxidation)–E_1/2(reduction)/V) potentials of the identical YD2-o-C8. A co-sensitiser is suggested for NIR sensitisation (550–950 nm) to increase the power-to-conversion efficiency beyond 14%.     

Heat transfer augmentation of a car radiator using nanofluids

The car radiator heat transfer enhancement by using TiO₂ and SiO₂ nanoparticles dispersed in water as a base fluid was studied experimentally. The test rig is setup as a car radiator with tubes and container. The range of Reynolds number and volume fraction are (250–1,750) and (1.0–2.5 %) respectively. Results showed that the heat transfer increases with increasing of nanofluid volume fraction. The experimental data is agreed with other investigator.     

Crystal-packing trends for a series of 6,9,12,15,18-pentaaryl-1-hydro[60]fullerenes

The relationship between the size of the substituents of aryl groups in a series of fifteen 6,9,12,15,18-pentaaryl-1-hydro[60]fullerenes and the solid-state structures and packing motifs of these compounds has been analyzed. Pentaarylfullerenes have a characteristic "badminton shuttlecock" shape that causes several derivatives to crystallize into columnar stacks. However, many pentaarylfullerenes form non-stacked structures with, for example, dimeric, layered, diamondoid, or feather-in-cavity relationships between molecules. Computational modeling gave a qualitative estimate of the best shape match between the ball and socket surfaces of each pentaarylfullerene. The best match was for pentaarylfullerenes with large, spherically shaped para-substituents on the aryl groups. The series of pentaarylfullerenes was characterized by single-crystal X-ray diffraction. A total of 34 crystal structures were obtained as various solvates and were categorized by their packing motifs.     

Low-cost low-threshold diode end-pumped Tm:YAG laser at 2.016?μm

We report a low-threshold continuous-wave Tm:YAG laser that can be excited near 785?nm with low-cost, single-mode AlGaAs laser diodes. Low-threshold operation was achieved using a tightly focused, astigmatically compensated x-cavity containing a 2-mm-thick Tm:YAG crystal with 5?% Tm³⁺ concentration. Two linearly polarized single-mode diodes operating at 785.8?nm were polarization coupled to end pump the resonator. With a 6?% output coupler, as high as 32?mW of output power could be obtained at 2016?nm with 184?mW of incident pump power. The output could be further tuned in the 1935?C2035?nm range. Slope efficiency measurements indicated that cross-relaxation was very effective at this doping level. With a 2?% output coupler, lasing could be obtained with as low as 32.3?mW of pump power. In the limit of vanishing output coupling, the incident threshold pump power could be reduced to as low as 25?mW. To our knowledge, this is among the lowest lasing thresholds reported to date for continuous-wave, room-temperature thulium lasers.     

Kinetic investigation of redox reaction between vitamin C and ferric chloride hexahydrate in acidic medium

The kinetics of the reaction between vitamin C (l-ascorbic acid) and ferric chloride hexahydrate was investigated in acidic medium at pH 3 spectrophotometrically. The order of the reaction was established by applying different methods, such as initial rate method, integration method and half-life method. The results obtained from each method were correlated with each other and consistency in all methods was observed. The order of the reaction with respect to each reactant was found first and the overall second order was recommended for the reaction.     

A Structural Study of Epoxidized Natural Rubber (ENR-50) and Its Cyclic Dithiocarbonate Derivative Using NMR Spectroscopy Techniques

A structural study of epoxidized natural rubber (ENR-50) and its cyclic dithiocarbonate derivative was carried out using NMR spectroscopy techniques. The overlapping ¹H-NMR signals of ENR-50 at δ 1.56, 1.68-1.70, 2.06, 2.15-2.17 ppm were successfully assigned. In this work, the ¹³C-NMR chemical shift assignments of ENR-50 were consistent to the previously reported work. A cyclic dithiocarbonate derivative of ENR-50 was synthesized from the reaction of purified ENR-50 with carbon disulfide (CS₂), in the presence of 4-dimethylaminopyridine (DMAP) as catalyst at reflux temperature. The cyclic dithiocarbonate formation involved the epoxide ring opening of the ENR-50. This was followed by insertion of the C-S moiety of CS₂ at the oxygen attached to the quaternary carbon and methine carbon of epoxidized isoprene unit, respectively. The bands due to the C=S and C-O were clearly observed in the FTIR spectrum while the ¹H-NMR spectrum of the derivative revealed the peak attributed to the methylene protons had split. The ¹³C-NMR spectrum of the derivative further indicates two new carbon peaks arising from the >C=S and quaternary carbon of cyclic dithiocarbonate. All other ¹H- and ¹³C-NMR chemical shifts of the derivative remain unchanged with respect to the ENR-50.     

Preparation and characterization of zinc oxide nanoflakes using anodization method and their photodegradation activity on methylene blue

In this work, we report the formation of leaf-like ZnO nanoflakes by anodization of zinc foil in a mixture of ammonium sulfate and sodium hydroxide electrolytes under various applied voltage and concentration of sodium hydroxide. The morphology and structure of ZnO nanoflakes were investigated by field emission scanning electron microscopy, energy-dispersive X-ray spectroscopy and X-ray diffraction analysis. In addition, the photocatalytic activity of the prepared nanoflakes zinc oxide was evaluated in the photodegradation of organic dye methylene blue (MB) solution under UV irradiation. It was found that zinc oxide prepared under high concentration of sodium hydroxide and high voltage showed better performance in the photodegradation of methylene blue.     

Synthesis of D-mannitol substituted ether-linked bis-1,2,3-triazoles as models of gemini surfactants

Readily available and low cost D-mannitol was converted into 1,2,5,6-di-O-isopropylidene-D-mannitol (1) in the presence of acetone and zinc chloride. Williamson etherfication of 1 with propargyl bromide afforded the bisalkyne 2 in a very good yield. 1,3-Dipolar cycloaddition of 2 with four different alkyl azides using click conditions gave four novel bistriazoles 3a-d. Removal of the acetal groups of 3a-d afforded the deprotected bistriazoles 4a-d in excellent yields. Products 3 and 4 represent models of gemini surfactants.     

An alkyl–palladium(II) complex with a bidentate phosphine ligand: [1,3‐bis(di­phenyl­phosphino)­propane‐P,P′]­dimethyl­palladium(II) toluene hemi­solvate

In the title compound, [Pd(CH₃)₂(C₂₇H₂₆P₂)]·0.5C₇H₈, the Pd atom is at the centre of an approximately square‐planar arrangement of two P atoms and two methyl groups. The P—Pd—P angle [93.19 (3)°] is significantly larger than that in the corresponding dichloride complex [Pd(dppp)Cl₂]. The toluene mol­ecule is disordered across an inversion centre.