No abstract

The inhibition of asphaltene precipitation from high-pressure, CO(2)-injected reservoir oils by ionic and nonionic amphiphiles, the ionic liquids based on p-alkylpyridinium ([C(n)()py](+)) and N-butylisoquinolinium ([C(4)iql](+)) cations, and the alkylbenzene-derived amphiphiles p-alkylphenol (C(n)()phol), p-alkylbenzenesulfonic acid (C(n)()bsa), and sodium p-alkylbenzenesulfonate (C(n)()bsNa) was investigated for the first time. The influences of the structures of these compounds and the effect of the combination of their cations and anions were studied. The results show that the inhibition abilities of the alkylbenzene-derived amphiphiles first increase when n = 2-8 and then remain almost constant when n >/=8 and that the effectiveness follows the order C(n)()phol < C(n)()bsa approximately C(n)()bsNa. The inverse trend is observed for the ionic liquids [C(n)()py][Cl]; that is, their inhibition abilities decrease as n increases from 4 to 8 to 12. [C(4)iql][Cl] is more effective than [C(4)py][Cl], but [C(n)()py][BF(4)] and [C(n)()py][PF(6)] have almost no effect on the stabilization of asphaltenes. It was found that the effectiveness of an alkylbenzene-derived amphiphile on the inhibition of asphaltene precipitation from reservoir oils relies on its ability to form a stable steric-stabilization layer around asphaltenes, which is controlled by the polarity of its headgroup and the length of its alkyl tail. The novel mechanism of inhibiting asphaltene precipitation using the ionic liquids [C(n)()py] ([Cl], [BF(4)], and [PF(6)]) and [C(4)iql][Cl] was proposed. The mechanism states that the ionic liquids can effectively prevent asphaltene precipitation from the reservoir oils by breaking the asphaltene associations, which are due to the local nonneutrality of the charge densities of the cation and the anion. The ionic liquids that are based on an anion with high charge density, in connection with cations with sufficiently low charge densities, can effectively inhibit asphaltene precipitation from the reservoir oils. This mechanism is also important for studying the thermodynamic properties and phase behavior of the ionic liquids.

A vast array of semiconductor applications relies on the ability to dope the materials by the controlled introduction of impurities in order to achieve desired charge carrier concentration and conduction type. In this way, various functional metal/semiconductor or semiconductor/semiconductor junctions can be constructed for device applications. Conjugated polymers are organic semiconductors that can be electrochemically doped to form a dynamic p-n junction. The electronic structure and even the existence of such a polymer p-n junction had been the subject of intense scrutiny and debate. In this work, the formation of the world's largest frozen polymer p-n junction and its light-emission are visualized. With a pair of micromanipulated probes, we mapped the potential distribution of the p-n junction under bias across the entire interelectrode gap of over 10 mm. Site-selective current-voltage measurements reveal that the polymer junction is a graded p-n junction, with a much more conductive p region than n region.

Enhanced high temperature thermoelectric properties of Bi-doped c -axis oriented Ca 3 Co 4 O 9 thin films by pulsed laser deposition

Ligand-free rutile and anatase TiO2nanocrystals were synthesizedviaa hydrolytic sol–gel method. The improved power conversion efficiency was achieved by using anatase TiO2nanocrystals as electron extraction layer in the organic solar cells.