surface reactivity
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2022 ◽  
Vol 13 (1) ◽  
Author(s):  
Hongxia Hao ◽  
Itai Leven ◽  
Teresa Head-Gordon

AbstractReaction rates of common organic reactions have been reported to increase by one to six orders of magnitude in aqueous microdroplets compared to bulk solution, but the reasons for the rate acceleration are poorly understood. Using a coarse-grained electron model that describes structural organization and electron densities for water droplets without the expense of ab initio methods, we investigate the electric field distributions at the air-water interface to understand the origin of surface reactivity. We find that electric field alignments along free O–H bonds at the surface are ~16 MV/cm larger on average than that found for O–H bonds in the interior of the water droplet. Furthermore, electric field distributions can be an order of magnitude larger than the average due to non-linear coupling of intramolecular solvent polarization with intermolecular solvent modes which may contribute to even greater surface reactivity for weakening or breaking chemical bonds at the droplet surface.


Author(s):  
Amymarie K. Bartholomew ◽  
Elena Meirzadeh ◽  
Ilana B. Stone ◽  
Christie S. Koay ◽  
Colin Nuckolls ◽  
...  

2022 ◽  
Vol 9 (1) ◽  
Author(s):  
Tej Poudel Chhetri ◽  
Lei Kerr ◽  
Nada Masmali ◽  
Herbert Jaeger ◽  
Khalid F. Eid

Nanostructured ZnO has been widely investigated as a gas sensing material. Antimony is an important dopant for ZnO that catalyses its surface reactivity and thus strengthens its gas sensing capability. However, there are not enough studies on the gas sensing of antimony-doped ZnO single wires. We fabricated and characterized ZnO/ZnO:Sb core–shell micro-wires and demonstrated that individual wires are sensitive to oxygen gas flow. Temperature and light illumination strongly affect the oxygen gas sensitivity and stability of these individual wires. It was found that these micro- and nano-wire oxygen sensors at 200°C give the highest response to oxygen, yet a vanishingly small effect of light and temperature variations. The underlying physics and the interplay between these effects are discussed in terms of surface-adsorbed oxygen, oxygen vacancies and hydrogen doping.


Geoderma ◽  
2022 ◽  
Vol 406 ◽  
pp. 115517
Author(s):  
Juan C. Mendez ◽  
Elise Van Eynde ◽  
Tjisse Hiemstra ◽  
Rob N.J. Comans

Sensors ◽  
2021 ◽  
Vol 21 (24) ◽  
pp. 8462
Author(s):  
Abdulaziz Alharbi ◽  
Benjamin Junker ◽  
Mohammad Alduraibi ◽  
Ahmad Algarni ◽  
Udo Weimar ◽  
...  

Beginning with LaFeO3, a prominent perovskite-structured material used in the field of gas sensing, various perovskite-structured materials were prepared using sol–gel technique. The composition was systematically modified by replacing La with Sm and Gd, or Fe with Cr, Mn, Co, and Ni. The materials synthesized are comparable in grain size and morphology. DC resistance measurements performed on gas sensors reveal Fe-based compounds solely demonstrated effective sensing performance of acetylene and ethylene. Operando diffuse reflectance infrared Fourier transform spectroscopy shows the sensing mechanism is dependent on semiconductor properties of such materials, and that surface reactivity plays a key role in the sensing response. The replacement of A-site with various lanthanoid elements conserves surface reactivity of AFeO3, while changes at the B-site of LaBO3 lead to alterations in sensor surface chemistry.


Polymers ◽  
2021 ◽  
Vol 13 (24) ◽  
pp. 4396
Author(s):  
Kateřina Polášková ◽  
Miloš Klíma ◽  
Zdeňka Jeníková ◽  
Lucie Blahová ◽  
Lenka Zajíčková

Polypropylene is a typical representative of synthetic polymers that, for many applications including adhesive joints, requires an increase in wettability and chemical surface reactivity. Plasma processing offers efficient methods for such surface modifications. A particular disadvantage of the plasma jets can be the small plasma area. Here, we present a cold atmospheric plasma radio-frequency slit jet developed with a width of 150 mm applied to polypropylene plasma treatment in Ar, Ar/O2 and Ar/N2 We identified two main parameters influencing the tensile strength of adhesive joints mediated by epoxy adhesive DP 190, nitrogen content, and the amount of low molecular weight oxidized materials (LMWOMs). Nitrogen functional groups promoted adhesion between epoxy adhesive DP 190 and the PP by taking part in the curing process. LMWOMs formed a weak boundary layer, inhibiting adhesion by inducing a cohesive failure of the joint. A trade off between these two parameters determined the optimized conditions at which the strength of the adhesive joint increased 4.5 times. Higher adhesion strength was previously observed when using a translational plasma gliding arc plasma jet with higher plasma gas temperatures, resulting in better cross linking of polymer chains caused by local PP melting.


Author(s):  
Keyvan Malaie ◽  
Zahra Heydari ◽  
Thierry Brousse

Abstract The extensive application of nickel foam (Ni foam) as current collector in supercapacitors has raised caveats on the contribution of the redox-active Ni foam to the measured capacities. However, due to the overlooked qualitative features (i.e., shapes) of the cyclic voltammograms (CVs), the redox reaction of the Ni foam oxide layer (NiFOL) has been frequently confused with the true electrochemical signature of the coated materials in alkaline solution. Herein, experimental CVs, scanning electron microscopy images, and estimations reveal that due to the high porosity of the Ni foam and its surface reactivity in alkaline solution (1-6 M KOH), the redox peak couple of the NiFOL can potentially be confused with or lead to misinterpretation of the true electrochemical features of the coatings. A classification of previous papers on a group of metal oxides investigated as battery-type or pseudocapacitive electrodes in the positive potential window is also presented to reveal the confusion between NiFOL and the coating when operated in alkaline solution.


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