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Start date: 2019 × Subject: acidity ×

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    The acidity of atmospheric particles and clouds
    (Katlenburg-Lindau : EGU, 2020) Pye, Havala O.T.; Nenes, Athanasios; Alexander, Becky; Ault, Andrew P.; Barth, Mary C.; Clegg, Simon L.; Collett Jr, Jeffrey L.; Fahey, Kathleen M.; Hennigan, Christopher J.; Herrmann, Hartmut; Kanakidou, Maria; Kelly, James T.; Ku, I-Ting; McNeill, V. Faye; Riemer, Nicole; Schaefer, Thomas; Shi, Guoliang; Tilgner, Andreas; Walker, John T.; Wang, Tao; Weber, Rodney; Xing, Jia; Zaveri, Rahul A.; Zuend, Andreas
    Acidity, defined as pH, is a central component of aqueous chemistry. In the atmosphere, the acidity of condensed phases (aerosol particles, cloud water, and fog droplets) governs the phase partitioning of semivolatile gases such as HNO3, NH3, HCl, and organic acids and bases as well as chemical reaction rates. It has implications for the atmospheric lifetime of pollutants, deposition, and human health. Despite its fundamental role in atmospheric processes, only recently has this field seen a growth in the number of studies on particle acidity. Even with this growth, many fine-particle pH estimates must be based on thermodynamic model calculations since no operational techniques exist for direct measurements. Current information indicates acidic fine particles are ubiquitous, but observationally constrained pH estimates are limited in spatial and temporal coverage. Clouds and fogs are also generally acidic, but to a lesser degree than particles, and have a range of pH that is quite sensitive to anthropogenic emissions of sulfur and nitrogen oxides, as well as ambient ammonia. Historical measurements indicate that cloud and fog droplet pH has changed in recent decades in response to controls on anthropogenic emissions, while the limited trend data for aerosol particles indicate acidity may be relatively constant due to the semivolatile nature of the key acids and bases and buffering in particles. This paper reviews and synthesizes the current state of knowledge on the acidity of atmospheric condensed phases, specifically particles and cloud droplets. It includes recommendations for estimating acidity and pH, standard nomenclature, a synthesis of current pH estimates based on observations, and new model calculations on the local and global scale. © 2020 Author(s).
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    Graphene oxide functional nanohybrids with magnetic nanoparticles for improved vectorization of doxorubicin to neuroblastoma cells
    (Basel : MDPI AG, 2019) Lerra, L.; Farfalla, A.; Sanz, B.; Cirillo, G.; Vittorio, O.; Voli, F.; Grand, M.L.; Curcio, M.; Nicoletta, F.P.; Dubrovska, A.; Hampel, S.; Iemma, F.; Goya, G.F.
    With the aim to obtain a site-specific doxorubicin (DOX) delivery in neuroblastoma SH-SY5Y cells, we designed an hybrid nanocarrier combining graphene oxide (GO) and magnetic iron oxide nanoparticles (MNPs), acting as core elements, and a curcumin–human serum albumin conjugate as functional coating. The nanohybrid, synthesized by redox reaction between the MNPs@GO system and albumin bioconjugate, consisted of MNPs@GO nanosheets homogeneously coated by the bioconjugate as verified by SEM investigations. Drug release experiments showed a pH-responsive behavior with higher release amounts in acidic (45% at pH 5.0) vs. neutral (28% at pH 7.4) environments. Cell internalization studies proved the presence of nanohybrid inside SH-SY5Y cytoplasm. The improved efficacy obtained in viability assays is given by the synergy of functional coating and MNPs constituting the nanohybrids: while curcumin moieties were able to keep low DOX cytotoxicity levels (at concentrations of 0.44–0.88 µM), the presence of MNPs allowed remote actuation on the nanohybrid by a magnetic field, increasing the dose delivered at the target site.