No abstract

Indene-C70 derivatives were synthesized, including indene-C70 mono-adduct (IC70MA), indene-C70 bis-adduct (IC70BA) and indene-C70 tris-adduct (IC70TA). All as-prepared fullerene adducts are in fact a mixture of isomers. The IC70BA mixture was further separated by high-performance liquid chromatography (HPLC) and two different IC70BA isomers were obtained. With the addition of the increased number of indene, the lowest unoccupied molecular orbital (LUMO) energy level of the C70 derivatives is also increased. IC70BA and its isomers have a slight difference in LUMO energy level, but show great differences in the absorption spectra. Polymer solar cells (PSCs) devices were fabricated under the same conditions with P3HT as donor, IC70BA and its isomer as acceptor, to examine the influence of the regioisomers on photovoltaic performance. The two IC70BA isomers exhibited varying power conversion efficiency (PCE) values of 2.80 and 3.18%, respectively, suggesting the molecular structure of the fullerene derivatives have an effect on polymer solar cells properties.

The detailed flow characteristics in the boundary layer are critical for physical understanding of complex flow and aerodynamic performance optimization of aircraft. In this study, high sensitive micro-electro-mechanical system flexible hot-film sensor was developed for measurement of unsteady boundary layer flow. The effects of annealing temperature and time on the temperature coefficient of resistance (TCR) were studied, the highest TCR value of 5100 ppm °C−1 was obtained after 6 h of vacuum thermal annealing treatment at 400 °C. The flow transition and separation characteristics developed on two-dimensional NACA 0012 airfoil at various Reynolds numbers and angles of attack were investigated by using flexible hot-film sensors with validation by surface pressure distribution and aerodynamic force coefficient. The accurate locations of onset, 50% intermittent and end of transition were detected successfully. The behavior of spatial progression to the leading edge of transition point was found as the Reynolds number and angle of attack increases. The hot-film sensor measurements also demonstrated the static stall of the airfoil was caused by the leading edge separation bubble.

A flexible hot-film sensor array for wall shear stress, flow separation, and transition measurement has been fabricated and implemented in experiments. Parylene C waterproof layer is vapor phase deposited to encapsulate the sensor. Experimental studies of shear stress and flow transition on a flat plate have been undertaken in a water tunnel with the sensor array. Compared with the shear stress derived from velocity profile and empirical formulas, the measuring errors of the hot-film sensors are less than 5%. In addition, boundary layer transition of the flat plate has also been detected successfully. Ensemble-averaged mean, normalized root mean square, and power spectra of the sensor output voltage indicate that the Reynolds number when transition begins at where the sensor array located is 1.82 × 105, 50% intermittency transition is 2.52 × 105, and transition finishes is 3.96 × 105. These results have a good agreement with the transition Reynolds numbers, as measured by the Laser Doppler Velocimetry (LDV) system.

The electronic properties of four metallofullerenol samples (La@C82(OH)32, La@C82(OH)24, La@C82(OH)18, La@C82(OH)12) and La@C82 were investigated by synchrotron radiation photoelectron emission spectra (PES). A new emission peak with binding energy of 13.9 eV, which is attributed to La 5d orbitals coupling with nanocage orbitals, is observed in PES of La@C82 for the first time. This suggestion is also supported by previous DFT calculations. Furthermore, the new emission peak disappears when the surface of La@C82 is modified with specific numbers of OH groups, which means the electron orbital coupling between inner metallic atoms and outer nanocage in metallofullerene could be shielded by surface modifications on the outer nanocage.