CONTENTS 1. Introduction and Overview of the Field 4260 2. Experimental Methods 4262 2.1. Chambers for Cloud and Aerosol Studies 4262 2.1.1. Cloud Chamber Studies 4262 2.1.2. Aqueous Aerosol Chamber Studies 4263 2.2. Analytical Techniques 4263 2.2.1. Transfer-MS and ESI-MS 4263 2.2.2. High-Resolution Mass Spectrometry (HRMS) 4263 2.2.3. Other MS-Based Studies 4264 2.2.4. NMR 4264 2.2.5. Droplet Evaporation Techniques 4264 2.2.6. Kinetics 4265 3. A Comparison of Aqueous Aerosol, Fog, and Cloud Chemistry 4266 3.1. Overview of Conditions 4266 3.1.1. Occurrence of the Tropospheric Aqueous Phase: RH, ALW, and Clouds on a Global Scale 4266 3.2. Aqueous-Phase Transfer 4267 3.3. pH Effects 4268 3.3.1. Acid−Base Equilibria of Acids and Diacids 4268 3.3.2. Dehydration Reactions of Reaction Intermediates: Alkyl Radical Reformation 4268 3.3.3. Organic Accretion Reactions 4269 3.4. Ionic Strength Effects and Treatment of Nonideal Solutions 4269 3.4.1. Radical Reactions 4269 3.4.2. Nonradical Reactions 4270 3.4.3. Salting-in and Salting-out 4270 3.4.4. Treatment of Nonideality in ALW Chemistry 4270 4. Photochemistry 4271 4.1. Inorganic Bulk Photolysis and Radical Sources 4.1.1. Hydrogen Peroxide Photolysis 4.1.2. Nitrite Photolysis 4.1.3. Photolysis of Chlorine-Containing Species 4.1.4. Peroxomonosulfate Photolysis 4.1.

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Organosulfates (OSs), also referred to as organic sulfate esters, are well-known and ubiquitous constituents of atmospheric aerosol particles. Commonly, they are assumed to form upon mixing of air masses of biogenic and anthropogenic origin, that is, through multiphase reactions between organic compounds and acidic sulfate particles. However, in contrast to this simplified picture, recent studies suggest that OSs may also originate from purely anthropogenic precursors or even directly from biomass and fossil fuel burning. Moreover, besides classical OS formation pathways, several alternative routes have been discovered, suggesting that OS formation possibly occurs through a wider variety of formation mechanisms in the atmosphere than initially expected. During the past decade, OSs have reached a constantly growing attention within the atmospheric science community with evermore studies reporting on large numbers of OS species in ambient aerosol. Nonetheless, estimates on OS concentrations and implications on atmospheric physicochemical processes are still connected to large uncertainties, calling for combined field, laboratory, and modeling studies. In this Critical Review, we summarize the current state of knowledge in atmospheric OS research, discuss unresolved questions, and outline future research needs, also in view of reductions of anthropogenic sulfur dioxide (SO 2 ) emissions. Particularly, we focus on (1) field measurements of OSs and measurement techniques, (2) formation pathways of OSs and their atmospheric relevance, (3) transformation, reactivity, and fate of OSs in atmospheric particles, and (4) modeling efforts of OS formation and their global abundance.

The incorporation of colloidal quantum dots (QDs) into ionic crystals of various salts (NaCl, KCl, KBr, etc.) is demonstrated. The resulting mixed crystals of various shapes and beautiful colors preserve the strong luminescence of the incorporated QDs. Moreover, the ionic salts appear to be very tight matrices, ensuring the protection of the QDs from the environment and as a result providing them with extraordinary high photo-and chemical stability. A prototype of a white light-emitting diode (WLED) with a color conversion layer consisting of this kind of mixed crystals is demonstrated. These materials may also find applications in nonlinear optics and as luminescence standards.

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Methoxyphenols, which are emitted through biomass burning, are an important species in atmospheric chemistry. In the present study, temperature-dependent aqueous-phase OH radical reactions of six methoxyphenols and two related phenols have been investigated through laser flash photolysis and the density functional theory. The rate constants obtained were in a range of (1.1−1.9) × 10 10 L molWe derived the parameters of these reactions from the obtained T-dependent rate constants and found a mean Arrhenius activation energy of 16.9 kJ mol −1 . The diffusion rate constants were calculated for each case and compared to the measured ones. Generally, the rate constants are found to be close to fully diffusion-controlled (k diff = (1.4−1.5) × 10 10 L mol −1 s −1 for all reactions). A structure−function relationship was established through the measurement result, which could be used for predicting unknown rate constants of other phenolic compounds. All of these findings are expected to enhance the predictive capabilities of models, such as the chemical aqueous-phase radical mechanism.

The dihydroxycarbonyls 3,4-dihydroxy-2-butanone (DHBO) and 2,3-dihydroxy-2-methylpropanal (DHMP) formed from isoprene oxidation products in the atmospheric gas phase under low-NO conditions can be expected to form aqSOA in the tropospheric aqueous phase because of their solubility. In the present study, DHBO and DHMP were investigated concerning their radical-driven aqueous-phase oxidation reaction kinetics. For DHBO and DHMP the following rate constants at 298 K are reported: k(OH + DHBO) = (1.0 ± 0.1) × 10 L mol s, k(NO + DHBO) = (2.6 ± 1.6) × 10 L mol s, k(SO+ DHBO) = (2.3 ± 0.2) × 10 L mol s, k(OH + DHMP) = (1.2 ± 0.1) × 10 L mol s, k (NO + DHMP) = (7.9 ± 0.7) × 10 L mol s, k(SO + DHMP) = (3.3 ± 0.2) × 10 L mol s, together with their respective temperature dependences. The product studies of both DHBO and DHMP revealed hydroxydicarbonyls, short chain carbonyls, and carboxylic acids, such as hydroxyacetone, methylglyoxal, and lactic and pyruvic acid as oxidation products with single yields up to 25%. The achieved carbon balance was 75% for DHBO and 67% for DHMP. An aqueous-phase oxidation scheme for both DHBO and DHMP was developed on the basis of the experimental findings to show their potential to contribute to the aqSOA formation. It can be expected that the main contribution to aqSOA occurs via acid formation while other short-chain oxidation products are expected to back-partition into the gas phase to undergo further oxidation there.

Surface workfunction changes upon C60 adsorption onto different metal single crystals are investigated by Kelvin probe force microscopy (KPFM). Literature values for similar metal/organic systems, showing a broad variation for both the measured metal workfunction and workfunction change, are compared to the acquired KPFM values. Good agreement is found between nanoscopic KPFM results and macroscopic photoelectron spectroscopy or Kelvin probe literature data. The model of a linear dependence between the metal substrate workfunction and the C60-induced workfunction change is confirmed. Former numerical simulations predicted a lateral quantitative KPFM resolution in the range of 10 nm, in this work results are published that show the achievement of this resolution with Cr coated, sharp tips. Furthermore, numerical simulations are presented that show the possibility of molecular contrast for KPFM.