SERS Not To Be Taken for Granted in the Presence of Oxygen
ABSTRACT Oxidation of the Ag nanoparticle surface has a dramatic effect on the adsorption, orientation, and SERS detection limit of nitroaromatic molecules in aqueous solutions. Ultrasensitive SERS detection of p-nitrophenol can be achieved when oxidation of surface-immobilized Ag nanoparticles is inhibited by replacing the oxygen dissolved in water with argon gas. The presence of silver oxide at the nanoparticle surface hinders charge transfer between the aromatic ring and the underlying Ag metal surface and drastically decreases the overall detection sensitivity.
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ABSTRACT: The front transparent conductive oxide layer is a source of significant optical and electrical losses in silicon heterojunction solar cells because of the trade-off between free-carrier absorption and sheet resistance. We demonstrate that hydrogen-doped indium oxide (IO:H), which has an electron mobility of over 100 cm2/V s, reduces these losses compared to traditional, low-mobility transparent conductive oxides, but suffers from high contact resistance at the interface of the IO:H layer and the silver front electrode grid. This problem is avoided by inserting a thin indium tin oxide (ITO) layer at the IO:H/silver interface. Such IO:H/ITO bilayers have low contact resistance, sheet resistance, and free-carrier absorption, and outperform IO:H-only or ITO-only layers in solar cells. We report a certified efficiency of 22.1% for a 4-cm2 screen-printed silicon heterojunction solar cell employing an IO:H/ITO bilayer as the front transparent conductive oxide.Solar Energy Materials and Solar Cells 08/2013; 115:151–156. DOI:10.1016/j.solmat.2013.03.024 · 5.03 Impact Factor
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ABSTRACT: SEIRA, SERS, TPD and DFT were used to study 4-nitrophenol (4NP), 3-nitrophenol (3NP) and 2-nitrophenol (2NP) adsorption on nanoscale silver films/powder. SERS and DFT demonstrated that 4NP adsorbed as the 4-nitrophenolate ion. SEIRA results revealed that a 4NP multilayer condensed differently using deposition solvents with and without polar bonds. 3NP and 2NP adsorption were not altered by the polar properties of the solvent. The nanoscale properties of the silver films/powder were shown to impact how the polar properties of the deposition solvent altered nitrophenol adsorption. In the SEIRA spectra of 4NP and 3NP a C=O stretch was observed above 1700cm(-1) using a highly volatile n-pentane deposition solvent. No other solvent yielded such a peak for 4NP or 3NP adsorption including n-heptane. 2NP had a C=O stretch regardless of deposition solvent. A C=O stretch confirmed nitrophenol ionization in the monolayer and pointed toward the significance of resonance in NP adsorption. 2NP never formed a multilayer at high exposures as demonstrated using TPD and SEIRA. Results of this work will have environmental implications and will aid biochemical and industrial applications where phenolic compounds are employed.Journal of Colloid and Interface Science 10/2009; 342(2):311-9. DOI:10.1016/j.jcis.2009.10.053 · 3.55 Impact Factor