The self-assembly of monodisperse gold and silver colloid particles into monolayers on polymer-coated substrates yields macroscopic surfaces that are highly active for surface-enhanced Raman scattering (SERS). Particles are bound to the substrate through multiple bonds between the colloidal metal and functional groups on the polymer such as cyanide (CN), amine (NH(2)), and thiol (SH). Surface evolution, which can be followed in real time by ultraviolet-visible spectroscopy and SERS, can be controlled to yield high reproducibility on both the nanometer and the centimeter scales. On conducting substrates, colloid monolayers are electrochemically addressable and behave like a collection of closely spaced microelectrodes. These favorable properties and the ease of monolayer construction suggest a widespread use for metal colloid-based substrates.

This paper details the kinetic aspects of covalent self-assembly of colloidal Au particles from solution onto immobilized organosilane polymers. On glass substrates, surface formation can be monitored using UV−vis spectroscopy and field emission scanning electron microscopy (FE-SEM). Correlation of these data allows the effect of nanostructure on bulk optical properties to be evaluated. At short derivatization times, particle coverage is proportional to (time)1/2. The particle sticking probability p, defined as the ratio of bound particles to the number of particles reaching the surface in a given time period, can be determined from a knowledge of the particle radius, solution concentration, temperature, and solution viscosity; for surfaces derivatized with (3-mercaptopropyl)trimethoxysilane (MPTMS), p ≈ 1. At longer derivatization times, interparticle repulsions result in a “saturation” coverage at ≈30% of a close-packed monolayer. Two approaches for modulating the rate of surface formation are described:  electrochemical potential control on organosilane-modified SnO2 electrodes and charge screening by organic adsorbates. Self-assembly of colloidal Au particles onto functionalized substrate surfaces is a reproducible phenomenon, as evidenced by UV−vis and surface enhanced Raman scattering (SERS) measurements on identically prepared substrates.

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Crude oils, produced waters, and emulsions retrieved from the Kutei Basin of Indonesia have been examined by a variety of analytical techniques to understand soap-formation mechanisms and origins of reactants. Crude oils contain long-chain, n-alkanoic or slightly branched monocarboxylic acids, which primarily have a landplant origin. Although the crude oils may contain up >1000 ppmw of carboxylic acids, the total acid number (TAN) is anomalously low (∼0.5 mg KOH/g, on average). Traces of mononaphthenic, bicyclonaphthenic, alkyl benzoic, diprotic, and tetraprotic acids are detected in some Kutei Basin oils. The oils and acids therein are significantly different from oils that have a marine algal origin, which, in certain areas of the world, contain high TAN values and concentrations of naphthenic acids synthesized by microbial biodegradation. The naphthenic acids combine with calcium in produced waters to form calcium naphthenates. Produced waters are enriched in sodium bicarbonate (NaHCO 3 ), as a result of the decarboxylation of volatile fatty acids. When the pH of produced water exceeds a value of ∼6.2, NaHCO 3 reacts with the carboxylic acids in a saponificationlike reaction to form interfacial sodium carboxylate soap emulsions. These emulsions may be stabilized by formation flour (reservoir formation of fine particulates of rock, such as quartz sand, silts, and aluminum silicate clays (for example, allophanes)), scale/corrosion debris, and high-molecular-weight acids. The Kutei Basin soap emulsions are resolved by heating and treatment with relatively high dosages of acid demulsifiers.

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