Artificial atom solids based on metal nanocrystals: Formation and electrical properties

Metal nanocrystals can behave as “artificial atoms” due to their diameter-dependent single electron charging energy. Organically passivated nanocrystals with narrow size distributions can self-assemble into ordered arrays, offering the possibility of artificial atom solids with unique collective electronic properties, derived from both the size-dependent electronic properties of the individual nanocrystal cores and the inter-nanocrystal electronic coupling mechanisms. We review our recent progress on probing the electronic properties of artificial atom solids via variable temperature charge transport measurements on laterally contacted arrays of metal nanocrystals, together with development of combined synthesis and processing routes to manipulate these properties.     

Reductive desorption of thiolate from monolayer protected gold clusters

The "electrochemical potential window" of monolayer-protected gold cluster (MPC) nanoelectrodes is probed where the electrified liquid-liquid interface is used as the detector. The first observation of the reductive desorption of thiolate at negative MPC core charge is reported.     

STANDARDIZATION OF CATCH-PER-UNIT-EFFORT FOR SHORT-TERM TRENDS IN CATCHABILITY

Examination of daily catch–per–unit–effort (CPUE) information on Pacific halibut revealed sharp declines that could not be explained by natural and fishing mortality. Catchability may have decreased during a fishing period because of local depletions of fish, changes in fish behavior, and other causes. Mathematical models of CPUE with a short–term catchability function of time or effort were based on a generalization of the DeLury method. A method of standardization was developed to account for the length of a fishing period and to correct for catchability. The effort model was best for Pacific halibut data and the application showed that standardization of CPUE is necessary to have a valid index of abundance when short–term changes in catchability occur.     

Synthesis and characterization of α,ω-bis(4-hydroxybutyl) polydimethylsiloxanes

α,ω-Bis(4-hydroxybutyl) polydimethylsiloxane (molecular weight 1500 to 4500) can be pre-pared with well-controlled molecular weight through the reaction of 1,3-bis(4-hydroxybu-tyl)tetramethyl disiloxane and dimethoxydimethyl silane or diethoxydimethyl silane in the presence of a stoichiometric amount of water and hydrochloric acid. The molecular weight of these hydroxybutyl-terminated polysiloxanes can be determined fairly consistently by a titration method. These polysiloxanes are stable toward cyclization. © 1995 John Wiley & Sons, Inc.     

Structure-function studies on a synthetic guanosine receptor that simultaneously binds Watson-Crick and Hoogsteen sites

[structure: see text] A series of receptors (11-16) designed to simultaneously bind the Watson-Crick and Hoogsteen sites of guanosine were synthesized, and their binding of guanosine tri-O-pentanoate (32) was probed via 1H NMR complexation studies in 5% DMSO-d6-chloroform-d. The guanosine receptors were synthesized with aminonaphthalene or aminoquinoline auxiliary groups tethered to N-4 of cytosine via a methylene or carbonyl group. A structure-function relationship was established allowing energetic contributions made by components of nucleoside analogues to be probed and more general design rules formulated that may guide the development of more efficacious DNA bases.     

Ultradoping Boron on Si(100) via Solvothermal Chemistry**

Ultradoping introduces unprecedented dopant levels into Si, which transforms its electronic behavior and enables its use as a next-generation electronic material. Commercialization of ultradoping is currently limited by gas-phase ultra-high vacuum requirements. Solvothermal chemistry is amenable to scale-up. However, an integral part of ultradoping is a direct chemical bond between dopants and Si, and solvothermal dopant-Si surface reactions are not well-developed. This work provides the first quantified demonstration of achieving ultradoping concentrations of boron (∼1e14 cm²) by using a solvothermal process. Surface characterizations indicate the catalyst cross-reacted, which led to multiple surface products and caused ambiguity in experimental confirmation of direct surface attachment. Density functional theory computations elucidate that the reaction results in direct B−Si surface bonds. This proof-of-principle work lays groundwork for emerging solvothermal ultradoping processes.