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Atmospheric organic aerosols play a major role in climate, demanding a better understanding of their formation mechanisms by contributing multiphase chemical reactions with the participation of water. The sunlight driven aqueous photochemistry of small 2-oxocarboxylic acids is a potential major source of organic aerosol, which prompted the investigations into the mechanisms of glyoxylic acid and pyruvic acid photochemistry reviewed here. While 2-oxocarboxylic acids can be contained or directly created in the particles, the majorities of these abundant and available molecules are in the gas phase and must first undergo the surface uptake process to react in, and on the surface, of aqueous particles. Thus, the work also reviews the acid-base reaction that occurs when gaseous pyruvic acid meets the interface of aqueous microdroplets, which is contrasted with the same process for acetic acid. This work classifies relevant information needed to understand the photochemistry of aqueous pyruvic acid and glyoxylic acid and motivates future studies based on reports that use novel strategies and methodologies to advance this field.

Cerium oxide (CeO2) nanoparticles were obtained by two-step synthetic process whose first step is heating process of ethylene glycol solution of Ce(NO3)3·6H2O with addition of 1 M NH3 aq. at 348 K for 24 h and a second step is dialysis process of the heated solution. These two-step processes enabled to obtain cerium oxide nanoparticles which were dispersed in H2O very stably and clear yellow sol was also obtained. Formation process of cerium oxide nanoparticles during the dialysis process in H2O was examined. For the dialysis process, inter-valence charge transfer (IVCT) absorption between Ce3+ and Ce4+ decreased. Furthermore, Raman spectrum of the CeO2 nanoparticles had the peak which corresponded to O22− ion, which was formed by reduction of O2. This result indicated that the dissolved O2 played important role of the oxidation of the Ce ions in cerium hydroxide (III) particles in the first step solution. The O22− ions which existed on the nanoparticle surface as peroxo group also contributed to the stable dispersion. Highlights: CeO2 sol was obtained by heating and dialysis of ethylene glycol solution of cerium nitrate hydrate (III). CeO2 nanoparticles were stably dispersed in H2O. Oxidation from Ce3+ to Ce4+ was occurred with dissolved O2 in H2O for dialysis process. Raman spectra indicated that of the obtained CeO2 nanoparticles contained oxygen vacancies. [ABSTRACT FROM AUTHOR]

• 3D Th ing -g-C 3 N 4 had extended π-conjugated system and accelerated electron transfer. • 3D Th ing -g-C 3 N 4 exhibited excellent cathodic ECL performance under lower potential. • The constructed ECL system used dissolved O 2 as the coreactant. • Multiple HCR based cascade amplification strategy was constructed to detecte miRNA. The low electrochemiluminescence (ECL) efficiency and poor ECL stability of graphitic carbon nitride (g-C 3 N 4) under high excitation potential due to obvious electrode passivation seriously restrict its further wider application. Here, construction of intramolecular donor–acceptor (D-A) structure had proposed to well resolve above problems, which had been rarely reported. As a research model, thiophene ring (electron donor, D) with strong electron donating property was doped into the heptazine (electron acceptor, A) of 3D g-C 3 N 4. An intramolecular D-A structure of 3D Th ing -g-C 3 N 4 was obtained, which had extended π-conjugated system and high-speed intramolecular electron transfer. As a result, 3D Th ing -g-C 3 N 4 with intramolecular D-A structure exhibiting excellent cathodic ECL performance with endogenous dissolved O 2 as coreactant under lower potential. Based on the above ECL system, an ultrasensitive biosensor was assembled for microRNA-221 detection with multiple HCR based cascade amplification strategy. The target-like DNA obtained through the initial HCR process induced by target could trigger multiple HCR processes again to realize the effective amplification of the target. The constructed biosensor had excellent detection performance for microRNA-221 and the detection limit was calculated as 5.25 aM. In conclusion, construction of intramolecular D-A structure was a novel and effective way to improve the ECL performance of g-C 3 N 4 , and the newly proposed multiple HCR based cascade amplification strategy paved provided new opportunities for the detection of cancer marker in early cancer diagnosis. [ABSTRACT FROM AUTHOR]

The sunlight photochemistry of the organic chromophore pyruvic acid (PA) in water generates ketyl and acetyl radicals that contribute to the production and processing of atmospheric aerosols. The photochemical mechanism is highly sensitive to dissolved oxygen content, [O2(aq)], among other environmental conditions. Thus, herein we investigate the photolysis (λ ≥ 305 nm) of 10–200 mM PA at pH 1.0 in water covering the relevant range 0 ≤ [O2(aq)] ≤ 1.3 mM. The rapid consumption of dissolved oxygen by the intermediate photolytic radicals is monitored in real time with a dissolved oxygen electrode. In addition, the rate of O2(aq) consumption is studied at air flow rates from 30.0 to 900.0 mL min−1. For the range of [PA]0 covered under air saturated conditions and 30 mL min−1 flow of air in this setup, the estimated half-lives of O2(aq) consumed by the photolytic radicals fall within the interval from 22 to 3 min. Therefore, the corresponding depths of penetration of O2(g) into water (x = 4.3 and 1.6 µm) are determined, suggesting that accumulation and small coarse mode aqueous particles should not be O2-depleted in the presence of sunlight photons impinging this kind of chromophore. These photochemical results are of major tropospheric relevance for understanding the formation and growth of secondary organic aerosol.

Purpose: It has been predicted that, during hyperoxia, excess O2 dissolved in arterial blood will significantly alter the blood's magnetic susceptibility. This would confound the interpretation of the hyperoxia-induced blood oxygenation level-dependent signal as arising solely from changes in deoxyhemoglobin. This study, therefore, aimed to determine how dissolved O2 affects the susceptibility of blood. Theory and Methods: We present a comprehensive model for the effect of dissolved O2 on the susceptibility of blood and compare it with another recently published model, referred to here as the ideal gas model (IGM). For validation, distilled water and samples of bovine plasma were oxygenated over a range of hyperoxic O2 concentrations and their susceptibilities were determined using multiecho gradient echo phase imaging. Results: In distilled water and plasma, the measured changes in susceptibility were very linear, with identical slopes of 0.062 ppb/mm Hg of O2. This change was dramatically less than previously predicted using the IGM and was close to that predicted by our model. The primary source of error in the IGM is the overestimation of the volume fraction occupied by dissolved O2. Conclusion: Under most physiological conditions, the susceptibility of dissolved O2 can be disregarded in MRI studies employing hyperoxia. [ABSTRACT FROM AUTHOR]

In this work, the electrochemiluminescence (ECL) phenomenon of three-dimensional graphitic carbon nitride (3D g-C 3 N 4) was reported. Firstly, the proposed 3D g-C 3 N 4 possessed 3D porous interconnected open-framework which enabled faster charge transport and efficient penetration of co-reactants due to "pore confinement effect". Then, we found that the dissolved O 2 could serve as an excellent co-reactant for cathodic ECL of 3D g-C 3 N 4. And the high specific surface area was beneficial to better adsorbing and gathering of dissolved O 2 and reactive oxygen species (ROSs), which made them full contact on the surface or inside of 3D g-C 3 N 4 , giving a more sufficient ECL reaction and higher ECL signal. Based on the proposed 3D g-C 3 N 4 -O 2 ECL system, a sensitive biosensor was constructed for microRNA-21 (miRNA-21) detection with assistance of 3D spherical tracks assisted 3D DNA walking machine, which exhibited superior performance for miRNA-21 with detection limit of 0.22 fM. The proposed 3D g-C 3 N 4 -O 2 ECL system with high ECL efficiency and the effective target conversion and amplification strategies were beneficial to construct ultra-sensitive ECL sensing platform, which would be better applied to clinical bioanalysis. [ABSTRACT FROM AUTHOR]

Highlights: [•] The efficiency of the methods increased in the following order: UV

Argyroneta aquatica is a unique air-breathing spider that lives virtually its entire life under freshwater. It creates a dome-shaped web between aquatic plants and fills the diving bell with air carried from the surface. The bell can take up dissolved O2 from the water, acting as a `physical gill'. By measuring bell volume and O2 partial pressure (PO2) with tiny O2-sensitive optodes, this study showed that the spiders produce physical gills capable of satisfying at least their resting requirements for O2 under the most extreme conditions of warm stagnant water. Larger spiders produced larger bells of higher O2 conductance (GO2). GO2 depended on surface area only; effective boundary layer thickness was constant. Bells, with and without spiders, were used as respirometers by measuring GO2 and the rate of change in PO2. Metabolic rates were also measured with flow-through respirometry. The water-air PO2 difference was generally less than 10 kPa, and spiders voluntarily tolerated low internal PO2 approximately 1-4kPa before renewal with air from the surface. The low PO2 in the bell enhanced N2 loss from the bell, but spiders could remain inside for more than a day without renewal. Spiders appeared to enlarge the bells in response to higher O2 demands and lower aquatic PO2. [ABSTRACT FROM AUTHOR]

Production of a novel bioflocculant by a fed-batch culture of Citrobacter sp. TKF04 was investigated using acetic acid as a sole carbon source. Synthesis of the bioflocculant was favored by dissolved O2 tension at 20% of air saturation and C/N ratio (mol acetic acid/mol ammonium) of 10:1 in the feed solution. Under optimal conditions, 4.6 g crude bioflocculant per liter broth was produced, whose flocculating activity was 22 300 units. This activity was 9 times higher than that of the control (only acetic acid was supplied). [ABSTRACT FROM AUTHOR]

Atmospheric organic aerosols play a major role in climate, demanding a better understanding of their formation mechanisms by contributing multiphase chemical reactions with the participation of water. The sunlight driven aqueous photochemistry of small 2-oxocarboxylic acids is a potential major source of organic aerosol, which prompted the investigations into the mechanisms of glyoxylic acid and pyruvic acid photochemistry reviewed here. While 2-oxocarboxylic acids can be contained or directly created in the particles, the majorities of these abundant and available molecules are in the gas phase and must first undergo the surface uptake process to react in, and on the surface, of aqueous particles. Thus, the work also reviews the acid-base reaction that occurs when gaseous pyruvic acid meets the interface of aqueous microdroplets, which is contrasted with the same process for acetic acid. This work classifies relevant information needed to understand the photochemistry of aqueous pyruvic acid and glyoxylic acid and motivates future studies based on reports that use novel strategies and methodologies to advance this field. [ABSTRACT FROM AUTHOR]

• A novel antifouling DNA sensor is proposed for BRCA1 ultrasensitive detection. • The needle-like Eu:Co 3 O 4 was in situ synthesized on conductive Ni foam as the basic photocathode. • CuS nanoparticles was grown on the surface of Eu:Co 3 O 4 /Ni foam through a SILAR to enhance the PEC response. • The antifouling interface was applied for DNA sequence fixing to improve the sensitivity of the sensor. • The sensor for BRCA1exhibits a low detection limit of 0.38 fM. In this work, the photosensitive needle-like Eu: Co 3 O 4 was synthesized on conductive nickel foam (Ni foam) in situ via hydrothermal and subsequent heat treatment, and as the basic material to construct an antifouling photoelectrochemical (PEC) DNA sensor for BRCA1 (breast cancer marker) detection. Ni foam has a great frame structure, which could well control the morphology and size of materials. Then CuS nanoparticles could easily grow on the surface of Eu: Co 3 O 4 /Ni foam through a sequential ionic layer adsorption reaction to further enhance the PEC response. For BRCA1 sensitivity analyzing, the excellent antifouling property was realized rely on the conjugation of amino-terminal poly(ethylene glycol) (PEG-NH 2). The developed PEC sensor displayed an outstanding stability and great sensitivity under the dissolved oxygen environment, and Ni foam PEC electrode provided potential application for other photosensitive materials-controlled preparation. [ABSTRACT FROM AUTHOR]

The sunlight photochemistry of the organic chromophore pyruvic acid (PA) in water generates ketyl and acetyl radicals that contribute to the production and processing of atmospheric aerosols. The photochemical mechanism is highly sensitive to dissolved oxygen content, [O2(aq)], among other environmental conditions. Thus, herein we investigate the photolysis (λ ≥ 305 nm) of 10–200 mM PA at pH 1.0 in water covering the relevant range 0 ≤ [O2(aq)] ≤ 1.3 mM. The rapid consumption of dissolved oxygen by the intermediate photolytic radicals is monitored in real time with a dissolved oxygen electrode. In addition, the rate of O2(aq) consumption is studied at air flow rates from 30.0 to 900.0 mL min−1. For the range of [PA]0 covered under air saturated conditions and 30 mL min−1 flow of air in this setup, the estimated half-lives of O2(aq) consumed by the photolytic radicals fall within the interval from 22 to 3 min. Therefore, the corresponding depths of penetration of O2(g) into water (x = 4.3 and 1.6 µm) are determined, suggesting that accumulation and small coarse mode aqueous particles should not be O2-depleted in the presence of sunlight photons impinging this kind of chromophore. These photochemical results are of major tropospheric relevance for understanding the formation and growth of secondary organic aerosol. [ABSTRACT FROM AUTHOR]