We use a charge reduction electrospray (ESI) source and subsequent ion mobility analysis with a differential mobility analyzer (DMA, with detection via both a Faraday cage electrometer and a condensation particle counter) to infer the densities of single and multiprotein ions of cytochrome C, lysozyme, myoglobin, ovalbumin, and bovine serum albumin produced from non-denaturing (20 mM aqueous ammonium acetate) and denaturing (1 : 49.5 : 49.5, formic acid : methanol : water) ESI. Charge reduction is achieved through use of a Po-210 radioactive source, which generates roughly equal concentrations of positive and negative ions. Ions produced by the source collide with and reduce the charge on ESI generated drops, preventing Coulombic fissions, and unlike typical protein ESI, leading to gas-phase protein ions with +1 to +3 excess charges. Therefore, charge reduction serves to effectively mitigate any role that Coulombic stretching may play on the structure of the gas phase ions. Density inference is made via determination of the mobility diameter, and correspondingly the spherical equivalent protein volume. Through this approach it is found that for both non-denaturing and denaturing ESI-generated ions, gas-phase protein ions are relatively compact, with average densities of 0.97 g cm(-3) and 0.86 g cm(-3), respectively. Ions from non-denaturing ESI are found to be slightly more compact than predicted from the protein crystal structures, suggesting that low charge state protein ions in the gas phase are slightly denser than their solution conformations. While a slight difference is detected between the ions produced with non-denaturing and denaturing ESI, the denatured ions are found to be much more dense than those examined previously by drift tube mobility analysis, in which charge reduction was not employed. This indicates that Coulombic stretching is typically what leads to non-compact ions in the gas-phase, and suggests that for gas phase measurements to be correlated to biomolecular structures in solution, low charge state ions should be analyzed. Further, to determine if different solution conditions give rise to ions of different structure, ions of similar charge state should be compared. Non-denatured protein ion densities are found to be in excellent agreement with non-denatured protein ion densities inferred from prior DMA and drift tube measurements made without charge reduction (all ions with densities in the 0.85-1.10 g cm(-3) range), showing that these ions are not strongly influenced by Coulombic stretching nor by analysis method.

SUMMARY The splitting of water in the presence of ordinary and nano TiO2 was carried out using hydrocarbon as a dual agent and solar energy as a light source for these experiments. The hydrogen gas evolved was tested and measured using downward displacement of water. The observed results show that more hydrogen was evolved when nano TiO2 was used as catalyst due to the larger surface area of the nano material. The splitting of sea water yields more hydrogen compared with ordinary water due to the presence of electron donating sodium ions in water. The added hydrocarbon plays a dual role as electron donor and as a trapping agent, which enhances the production of hydrogen to a greater extent compared with the regular donors such as olefin. Copyright © 2013 John Wiley & Sons, Ltd.

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In diffusion charging theory, it is assumed that each ion-particle collision leads to the transfer of charge from ion to particle, and that charge transfer will not occur upon collision between a vapor molecule and a charged particle. However, in chemical ionization, charge transfer can occur in two directions-from charge-donating ion to vapor molecule and back from charged vapor molecule to the original charge-donating species. Both aerosol diffusion charging and chemical ionization are collision-based charge transfer processes, and for particles only slightly larger than vapor molecules (aerosol clusters), the line between diffusion charging and chemical ionization becomes blurred. We examined the charge transfer from aerosol clusters (positively charged amino acid clusters) in the ∼1.0 nm size range to neutral vapor molecules (trimethylamine) at atmospheric pressure by using a combined experimental and theoretical approach. It was found that for singly charged amino acid cluster ions composed of 1, 2, and 3 amino acid molecules, the rate of charge transfer to trimethylamine vapor molecules was clearly observable, particularly for clusters composed of 1 and 2 molecules. The charge transfer rate for singly charged clusters with 4 or more amino acid molecules was consistently close to 0, indicating that the rate of charge transfer from clusters to vapor molecules is size dependent. The charge transfer rates also varied with cluster's chemical composition. Overall, this study demonstrates that small aerosol clusters (∼0.5 nm) can lose charge through collisions with vapor molecules, which is typically not considered in diffusion charging theories.

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