For a sufficiently large charge imbalance, the electric field generated by the nanoparticle will be able to engender anodic etching not only at the nanoparticle/Si interface but also deeper into the surrounding Si. Electropolishing will occur at the nanoparticle/Si interface where the potential is highest. Farther away from the metal/Si interface, the electric field is high enough to induce either valence 2 or valence 4 etching and the production of nanocrystalline porous Si. A porous layer

surrounding the metal/Si interface would allow for transport of the etchant solution to the interface, which will facilitate etching and the transport of both reactants to and products away from the reactive PSI-7977 molecular weight interface. The oxidant primarily injects holes at the top of the metal nanoparticle rather than at the metal/Si interface, as illustrated Sapanisertib purchase in Figure 3. Figure 3 The mechanism of metal-assisted etching. Charge accumulation on

the metal nanoparticle generates an electric field. Close to the particle, the effective applied see more voltage is sufficient to push etching into the electropolishing regime, facilitating the formation of an etch track approximately the size of the nanoparticle. Further way, the lower voltage corresponds to the porous silicon formation regime. Conclusions The band structure of the metal/Si interface does not facilitate the diffusion of charge away from a metal after an oxidant has injected a hole into the metal. Therefore, the Bumetanide holes injected into the metal are not directly available to induce etching in Si. It is proposed here that the catalytic injection of holes by an oxidant in solution to a metal (film or nanoparticle) in metal-assisted etching (MAE) leads to a steady state charge imbalance in the metal. This excess charge induces an electric field in the vicinity of the metal and biases the surrounding Si. Close to the metal, the potential is raised sufficiently to induce etching with electropolishing character. Further away from the metal, the potential is sufficient to induce etching that leads to the formation of porous

silicon by either a valence 2 or valence 4 process. The balance between valence 2 etching, valence 4 etching, and electropolishing varies depending on the chemical identity of the metal. Authors’ information KWK is a Professor of Chemistry as well as a Chartered Chemist (Royal Society of Chemistry) with a Ph.D. in Chemical Physics from Stanford University and a B.S. in Chemistry from the University of Pittsburgh. Acknowledgements Experiments concerning the stoichiometry of metal-assisted etching to be reported elsewhere were performed together with William B. Barclay, now at the University of Maine. Electron microscopy in support of these experiments was performed with Yu Sun and Mark Aindow at the University of Connecticut.

The as-synthesized CuGaS2 nanoplates adopt a unique crystal structure of wurtzite-zincblende polytypism. In the growth process of CuGaS2 nanoplates, copper sulfides firstly formed, and then the as-formed copper sulfides

were gradually phase-transformed to CGS nanoplates with proceeding of the reaction. The optical bandgap energy of the nanoplates is estimated to be approximately 2.24 eV. Our results will aid in the application of two-dimensional CuGaS2 nanoplates and the synthesis of other multicomponent sulfide nanomaterials. Acknowledgements FK866 price This work was supported by the National Natural Science Foundation of China (No. 91022033, No. 21171158), and National Basic Research Program of China (2010CB934700). Electronic supplementary material Additional file 1:

Three crystal structure models of CuGaS2 and an XRD pattern of an intermediate sample. Figure S1. Three crystal structure models of CuGaS2 (a) tetragonal chalcopyrite structure; (b) cation-disordered cubic zincblende modification, (c) cation-disordered hexagonal wurtzite phase. Figure S2. XRD pattern of a sample collected at 220°C for 0 min. In the present case, Cu2-xS (JCPDS 23–0959) seems to contribute to the experimental pattern. (DOC 872 KB) References 1. Zhong H, Bai Z, Zou B: Tuning the luminescence properties of colloidal I–III–VI semiconductor nanocrystals for optoelectronics and biotechnology applications. J Phys Chem Lett 2012, 3:3167–3175.CrossRef 2. Aldakov D, Lefrancois A, Reiss P: Ternary and quaternary metal chalcogenide nanocrystals: synthesis, properties and applications. J Mater Chem C 2013, JPH203 ic50 1:3756–3776.CrossRef 3. Panthani MG, Akhavan V, Goodfellow B, Schmidtke JP, Dunn L, MK5108 molecular weight Dodabalapur A, Barbara PF, Korgel BA: Synthesis of CuInS 2 , CuInSe 2 , and Cu(In x Ga 1- x )Se 2 (CIGS) nanocrystal “inks” for printable photovoltaics. J Am Chem Soc 2008, 130:16770–16777.CrossRef 4. Tsuji

I, Kato H, Kudo A: Photocatalytic hydrogen evolution on ZnS-CuInS 2 -AgInS 2 solid solution photocatalysts with wide visible light absorption bands. Chem Mater 2006, 18:1969–1975.CrossRef 5. Song WS, Yang H: Efficient 4��8C white-light-emitting diodes fabricated from highly fluorescent copper indium sulfide core/shell quantum dots. Chem Mater 2012, 24:1961–1967.CrossRef 6. Pons T, Pic E, Lequeux N, Cassette E, Bezdetnaya L, Guillemin F, Marchal F, Dubertret B: Cadmium-free CuInS 2 /ZnS quantum dots for sentinel lymph node imaging with reduced toxicity. ACS Nano 2010, 4:2531–2538.CrossRef 7. Xie RG, Rutherford M, Peng XG: Formation of high-quality I-III-VI semiconductor nanocrystals by tuning relative reactivity of cationic precursors. J Am Chem Soc 2009, 131:5691–5697.CrossRef 8. Pan DC, An LJ, Sun ZM, Hou W, Yang Y, Yang ZZ, Lu YF: Synthesis of Cu-In-S ternary nanocrystals with tunable structure and composition. J Am Chem Soc 2008, 130:5620–5621.CrossRef 9.

The data set was divided into four parts and examined to ensure a minimum representation of each gene region in each part of the tree to prevent skewing: 59–95 % for ITS, 91–98 % for LSU, 32–83 % SSU, and 29–54 % RPB2 except for the Hygrophorus-Chromosera group with 15 % rpb2. Specimens selleck chemicals examined and drawings All of the cited types, specimens sequenced, and the specimens illustrated by drawings were examined by DJ Lodge with the exceptions noted below. Aeruginospora singularis had a type study by E Horak (FH). Types and collections of Hygrophorus spp. s.s. were examined by E Larsson, except A Kovalenko examined those from Russia and DJ Lodge examined those from Belize, the

Dominican Republic and Japan. Types and collections sequenced in subf. Lichenomphalioideae were examined by R Lücking, SA Redhead and LL Norvell, except for Lichenomphalia hudsoniana and L. umbellifera which were collected and examined by J Geml, and Cantharellula umbonata and C. humicola which were examined by DE Desjardin and DJ Lodge. T Læssøe collected and examined Chromosera and Haasiella from Russia and Danish collections of Chrysomphalina and Pseudoomphalina. G Griffith examined collections from Wales. Collections at Kew were matched

to reference ITS sequences, and M Ainsworth (B Dentinger et al., unpublished) re-determined them with microscopy. D Boertmann examined some collections selleck chemicals llc from ABT-888 cell line Hungary, but they are not deposited in recognized fungaria. Drawings of hand cut sections were made by DJ Lodge with the aid of an Olympus microscope and drawing tube. Locations where collections that were sequenced are deposited are given in Online Resource 1. Collection numbers for drawings are given

in the figure captions; these collections are deposited at CFMR, except for Aeruginospora singularis (BO); Cantharellula umbonata and C. humicola (SFSU); Hygrocybe appalachianensis (DMWV); Humidicutis pura (K); Ampulloclitocybe Phospholipase D1 clavipes, Cuphophyllus acutoides var. pallidus, C. aff. pratensis, Gloioxanthomyces vitellinus, Humidicutis auratocephalus and Pseudoarmillariella ectypoides (TENN). Results and discussion Ecology The Hygrophoraceae is known to comprise genera with different nutritional strategies, including known biotrophic associations with ectomycorrhizal plants, algae, cyanobacteria and mosses (Lawrey et al. 2009; Seitzman et al. 2011; Tedersoo et al. 2010). The remaining genera in Hygrophoraceae were putatively regarded as saprotrophic, but recent data derived from stable isotope ratios are at variance with that assumption (Griffith et al. 2002; Griffith 2004; Seitzman et al. 2011). Knowledge about nutritional strategies is important for conservation of species of Hygrophoraceae, and many species are reported as threatened in Europe and Australia (Boertmann 2010; Gärdenfors 2010; Griffith 2004; Griffith et al. 2002, 2004; Kearney and Kearney 2000; Young 2005).

5 V, while for the point contacts in Figure 5c, the threshold voltage does not exceed 1 V. It is also noticed that there is a different response of the I-Vs in the two metal-dielectric-metal devices.

Figure 5 C -AFM measurements of a- TaN x . (a) Positive I-V curves (solid lines) of TaN x deposited on Au for four different points fitted by the space-charge-limited current (SCLC) model (dash lines). (b) Negative I-V curves (solid lines) of TaN x deposited on Au for the same points presented in (a) fitted by the SCLC Epigenetic Reader Domain inhibitor model (dash lines). (c) Positive I-V curves of TaN x deposited on Si for three different points. The conductive part of the I-Vs exhibits an OSI-027 cell line almost parabolic to almost ohmic behavior (d) Negative I-V curves of TaN x deposited on Si for the points presented

in (b). In all I-Vs, the leakage current is quite high, displaying also a very noisy profile. In general, the total current flowing through a semiconductor can be written as I tot = I b + I s, where I b is the current from the bulk part of the film and I s includes the electronic conduction through the surface states and through the space charge layer beneath the surface. Taking into account the amorphous nature of the semiconducting film, the main conduction mechanism from the bulk is expected to be the Poole-Frenkel effect [43]. Usually in amorphous materials, the predominant

conduction mechanism is the Poole-Frenkel effect, i.e., the thermal emission of electrons from charged vacancies, attributed to impurities and defects that are present in large numbers inside the bulk of the amorphous matrix [43, 44]. In the present samples, charged nitrogen Anlotinib vacancies act like Coulombic traps that promote the injection of electrons from the Au or Ag bottom electrode as the electric field increases during forward bias direction and from Pt/Ir tip during the reverse bias direction. For Poole-Frenkel emission, the current density is given by [45]: (1) where C and β are material dependent constants, E is the induced electric field, q is the electron charge, T is the temperature, k is the Boltzmann NADPH-cytochrome-c2 reductase constant, and φ is the ionization potential in V. The constant C is related to charge carrier mobility and trap’s density, while β is related to the dielectric constant ε 0 ε r via (2) Other possible charge carrier transport mechanisms from the bulk of the film could be thermionic emission of charge carriers across the metal-dielectric interface or field emission by electron tunneling from the metal or charge traps to the quasi-conduction band of the amorphous semiconductor [46]. These mechanisms have also exponential like I-V behavior.