Assessment of functionalized iron oxide nanoparticles in vitro: Introduction to integrated nanoimpact index
Bayat, N. , Lopes, V.R., Sanchez Dominguez, M. , Lakshmanan, R., Rajarao, G.K., Cristobal, S.
Environmental Science: Nano, 2, (2015), 380-394, F. I. Not Available
Functionalization of super paramagnetic iron oxide NPs (SPIONs) with different coatings renders them with unique physicochemical properties that allow them to be used in a broad range of applications such as drug targeting and water purification. However, it is required to fill the gap between the promises of any new functionalized SPIONs and the effects of these coatings on the NPs safety. Nanotoxicology is offering diverse strategies to assess the effect of exposure to SPIONs in a case-by-case manner but an integrated nanoimpact scale has not been developed yet. We have implemented the classical integrated biological response (IBR) into an integrated nanoimpact index (INI) as an early warning scale of nano-impact based on a combination of toxicological end points such as cell proliferation, oxidative stress, apoptosis and genotoxicity. Here, the effect of SPIONs functionalized with tri-sodium citrate (TSC), polyethylenimine (PEI), aminopropyl-triethoxysilane (APTES) and Chitosan (chitosan) were assessed on human keratinocytes and endothelial cells. Our results show that endothelial cells were more sensitive to exposure than keratinocytes and the initial cell culture density modulated the toxicity. PEI-SPIONs had the strongest effects in both cell types while TSC-SPIONS were the most biocompatible. This study emphasizes not only the importance of surface coatings but also the cell type and the initial cell density on the selection of toxicity assays. The INI developed here could offer an initial rationale to choose either modifying SPIONs properties to reduce its nanoimpact or performing a complete risk assessment to define the risk boundaries.
Impurities and Electronic Property Variations of Natural MoS2 Crystal Surfaces
Addou, R, McDonnell, S. , Barrera, D., Guo, Z. , Azcatl, A., Wang, J., Zhu, H., Hinkle, C.L. , Quevedo Lopez, M., Alshareef, H.N., Colombo, L., Hsu, J.W.P., Wallace, R.M.
ACS Nano, 9, (2015), 9124-9133, F. I. 12.881
Room temperature X-ray photoelectron spectroscopy (XPS), inductively coupled plasma mass spectrometry (ICPMS), high resolution Rutherford backscattering spectrometry (HR-RBS), Kelvin probe method, and scanning tunneling microscopy (STM) are employed to study the properties of a freshly exfoliated surface of geological MoS2 crystals. Our findings reveal that the semiconductor 2H-MoS2 exhibits both n- and p-type behavior, and the work function as measured by the Kelvin probe is found to vary from 4.4 to 5.3 eV. The presence of impurities in parts-per-million (ppm) and a surface defect density of up to 8% of the total area could explain the variation of the Fermi level position. High resolution RBS data also show a large variation in the MoSx composition (1.8 < x < 2.05) at the surface. Thus, the variation in the conductivity, the work function, and stoichiometry across small areas of MoS2 will have to be controlled during crystal growth in order to provide high quality uniform materials for future device fabrication.
Steps or Terraces? Dynamics of Aromatic Hydrocarbons Adsorbed at Vicinal Metal Surfaces
Camarillo Cisneros, J., Liu, W., Tkatchenko, A.
Physical Review Letters, 115, (2015), 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.a, 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%.