Steps or Terraces Dynamics of Aromatic Hydrocarbons Adsorbed at Vicinal Metal Surfaces
Camarillo Cisneros, J., Liu, W., Tkatchenko, A.Physical Review Letters, 115 , (2015), DOI: 10.1103/PhysRevLett.115.086101, F. I. 7.512
The study of how molecules adsorb, diffuse, interact, and desorb from imperfect surfaces is essential for a complete understanding of elementary surface processes under relevant pressure and temperature conditions. Here we use first-principles calculations to study the adsorption of benzene and naphthalene on a vicinal Cu(443) surface with the aim to gain insight into the behavior of aromatic hydrocarbons on realistic surfaces at a finite temperature. Upon strong adsorption at step edges at a low temperature, the molecules then migrate from the step to the (111) terraces, where they can freely diffuse parallel to the step edge. This migration happens at temperatures well below the onset of desorption, suggesting a more complex dynamical picture than previously proposed from temperature-programed desorption studies. The increase of the adsorption strength observed in experiments for Cu(443) when compared to Cu(111) is explained by a stronger long-range van der Waals attraction between the hydrocarbons and the step edges of the Cu(443) surface. Our calculations highlight the need for time-resolved experimental studies to fully understand the dynamics of molecular layers on surfaces.
Solution synthesized p -type copper gallium oxide nanoplates as hole transport layer for organic photovoltaic devices
Wang, J., Ibarra, V., Barrera, D., Xu, L., Lee, Y.J., Hsu, J.W.P.Journal of Physical Chemistry Letters, 6 , (2015), 1071-1075, F. I. 7.458
p-Type metal-oxide hole transport layer (HTL) suppresses recombination at the anode and hence improves the organic photovoltaic (OPV) device performance. While NiOx has been shown to exhibit good HTL performance, very thin films (<10 nm) are needed due to its poor conductivity and high absorption. To overcome these limitations, we utilize CuGaO2, a p-type transparent conducting oxide, as HTL for OPV devices. Pure delafossite phase CuGaO2 nanoplates are synthesized via microwave-assisted hydrothermal reaction in a significantly shorter reaction time compared to via conventional heating. A thick CuGaO2 HTL (∼280 nm) in poly(3-hexylthiophene):[6,6]-phenyl-C61-butyric acid methyl ester (P3HT:PCBM) devices achieves 3.2% power conversion efficiency, on par with devices made with standard HTL materials. Such a thick CuGaO2 HTL is more compatible with large-area and high-volume printing process.
Benzodifuran and benzodithiophene donor-acceptor polymers for bulk heterojunction solar cells
Huang, P., Du, J, Gunathilake, S.S, Rainbolt, E.A, Murphy, J.W, Black, K.T, Barrera, D, Hsu, J.W.P, Gnade, B.E, Stefan, M.C, Biewer, M.C.Journal of Materials Chemistry A, 3 , (2015), 6980-6989, F. I. 7.443
Four new donor-acceptor copolymers were synthesized by using benzo[1,2-b:4,5-b′]dithiophene and benzo[1,2-b:4,5-b′]difuran as donors and thieno[3,4-b]thiophene was used as the acceptor building block. A systematic study was performed to determine the influence of the combinations of different heteroatoms in the donor-acceptor copolymer. In bulk heterojunction solar cells, the polymer with all furan building blocks in the electron donating units, poly[(4,8-bis(5-dodecyl-2-furanyl)benzo[1,2-b:4,5-b′]difuran-2-yl)-alt-(2-ethyl-1-(3-fluorothieno[3,4-b]thiophen-2-yl)-1-hexanone)] (P4) (Mn = 66.7 kDa), achieved the highest power conversion efficiency of 5.23%.
Copper-palladium core-shell as an anode in a multi-fuel membraneless nanofluidic fuel cell: Toward a new era of small energy conversion devices
Maya Cornejo, J., Ortiz Ortega, E., Álvarez Contreras, L., Arjona, N., Guerra Balcázar, M., Ledesma García, J., Arriaga, L.G.Chemical Communications, 51 , (2015), 2536-2539, F. I. 6.834
A membraneless nanofluidic fuel cell with flow-through electrodes that works with several fuels (individually or mixed): methanol, ethanol, glycerol and ethylene-glycol in alkaline media is presented. For this application, an efficient Cu@Pd electrocatalyst was synthesized and tested, resulting outstanding performance until now reported, opening the possibility of power nano-devices for multi-uses purposes, regardless of fuel re-charge employed.
Toward a unified description of luminescence-local structure correlation in Ln doped CeO2 nanoparticles: Roles of Ln ionic radius, Ln concentration, and oxygen vacancies
Avram, D., Sánchez Domínguez, M., Cojocaru, B., Florea, M., Parvulescu, V., Tiseanu, C.Journal of Physical Chemistry C, 119 , (2015), 16303-16313, F. I. 4.772
We propose a physical model for luminescence properties of trivalent lanthanide (Ln) doped into CeO2 by use of low temperature, site selective, time-gated luminescence spectroscopy seconded by X-ray diffraction, Raman, and Fourier transform infrared spectroscopy and transmission electron microscopy. The main findings can be summarized as follows: (i) Ln situated to both the left and right sides to Gd in the Ln series exhibit a two-center distribution. Both Ln centers substitute for the tetravalent Ce fluorite sites being differentiated by the local symmetry: cubic, as a result of zero vacancy in the nearest-neighbor oxygen shell (cubic Ln center), and low symmetry, likely due to one vacancy in the nearest-neighbor oxygen shell (Ln-defect associate center). (ii) A first example of Dy emission in an inversion (cubic) symmetry, characterized by relatively strong lines at 679 and 764 nm, is reported. This result is expected to challenge the way this lanthanide is currently used as a luminescence probe. (iii) The relative contribution of the Ln centers to the overall emission depends on the Ln ionic radius: Sm exists predominantly as a cubic center, while Er is found mostly as a vacancy associate. (iv) Er, La codoped CeO2 can be used as an effective model system to separate the effects of Ln concentration and subsequently induced oxygen vacancies on the efficiency of CeO2 sensitization of Ln emission. (v) Zr co-doping of CeO2 obstructs the formation of Ln-defect associates. The implications of our findings for the interpretation of data already present in the literature are also discussed.