اشترك بالحزمة الذهبية واحصل على وصول غير محدود شمرا أكاديميا
تسجيل مستخدم جديدElectrolytically Generated Nanobubbles on HOPG Surfaces
225
0
0.0
(
0
)
اسأل ChatGPT حول البحث
ﻻ يوجد ملخص باللغة العربية
Electrolysis of water is employed to produce surface nanobubbles on highly orientated pyrolytic graphite (HOPG) surfaces. Hydrogen (oxygen) nanobubbles are formed when the HOPG surface acts as negative (positive) electrode. Coverage and volume of the nanobubbles enhance with increasing voltage. The yield of hydrogen nanobubbles is much larger than the yield of oxygen nanobubbles. The growth of the individual nanobubbles during the electrolysis process is recorded in time with the help of AFM measurements and correlated with the total current. Both the size of the individual nanobubbles and the total current saturate after typical 1 minute; then the nanobubbles are in a dynamic equilibrium, meaning that they do not further grow, in spite of ongoing gas production and nonzero current. The surface area of nanobubbles shows a good correlation with the nanobubble volume growth rate, suggesting that either the electrolytic gas emerges directly at the nanobubbles surface, or it emerges at the electrodes surface and then diffuses through the nanobubbles surface. Moreover, the experiments reveal that the time constants of the current and the aspect ratio of nanobubbles are the same under all conditions. Replacement of pure water by water containing a small amount of sodium chloride (0.01 M) allows for larger currents, but qualitatively gives the same results.
قيم البحث
اقرأ أيضاً
Confined glasses and their anomalous interfacial rheology raise important questions in fundamental research and numerous practical applications. In this Letter, we study the influence of interfacial air nanobubbles on the free surface of ultrathin hi
gh-molecular-weight glassy polystyrene films immersed in water, in ambient conditions. In particular, we reveal the counterintuitive fact that a soft nanobubble is able to deform the surface of a rigid glass, forming a nanocrater with a depth that increases with time. By combining in-situ atomic-force-microscopy measurements and a modified lubrication model for the liquid-like layer at the free surface of the glass, we demonstrate that the capillary pressure in the nanobubble together with the liquid-like layer at the free surface of the glass determine the spatiotemporal growth of the nanocraters. Finally, from the excellent agreement between the experimental profiles and the numerical solutions of the governing glassy thin-film equation, we are able to precisely extract the surface mobility of the glass. In addition to revealing and quantifying how surface nanobubbles deform immersed glasses, until the latter eventually dewet from their substrates, our work provides a novel, precise, and simple measurement of the surface nanorheology of glasses.
A pi-conjugated {C}3h-oligomer involving three dithienylethylene branches bridged at the meta positions of a central benzenic core has been synthesized and deposited either on the Si(100) surface or on the HOPG surface. On the silicon surface, scanni
ng tunneling microscopy allows the observation of isolated molecules. Conversely, by substituting the thiophene rings of the oligomers with alkyl chains, a spontaneous ordered film is observed on the HOPG surface. As the interaction of the oligomers is different with both surfaces, the utility of the Si(100) surface to characterize individual oligomers prior to their use into a 2D layer is discussed.
The surface structure of Few-Layer Graphene (FLG) epitaxially grown on the C-face of SiC has been investigated by TM-AFM in ambient air and upon interaction with diluted aqueous solutions of bio-organic molecules (dimethyl sulfoxide, DMSO, and L-Meth
ionine). On pristine FLG we observe nicely ordered, three-fold oriented rippled domains, with a 4.7+/-0.2 nm periodicity (small periodicity, SP) and a peak-to-valley distance in the range 0.1-0.2 nm. Upon mild interaction of the FLG surface with the molecular solution, the ripple periodicity relaxes to 6.2+/-0.2 nm (large periodicity, LP), while the peak-to-valley height increases to 0.2-0.3 nm. When additional energy is transferred to the system through sonication in solution, graphene planes are peeled off from FLG, as shown by quantitative analysis of XPS and Raman spectroscopy data which indicate a neat reduction of thickness. Upon sonication rippled domains are no longer observed. Regarding HOPG, we could not observe ripples on cleaved samples in ambient air, while LP ripples develop upon interaction with the molecular solutions. Recent literature on similar systems is not univocal regarding the interpretation of rippling. The complex of our comparative observations on FLG and HOPG can be hardly rationalized solely on the base of surface assembly of molecules, either organic molecules coming from the solution or adventitious species. We propose to consider the ripples as the manifestation of the free-energy minimization of quasi-2D layers, eventually affected by factors such as the interplane stacking, the interaction with molecules and/or with the AFM tip.
Recent studies have highlighted the sensitivity of active matter to boundaries and their geometries. Here we develop a general theory for the dynamics and statistics of active particles on curved surfaces and illustrate it on two examples. We first s
how that active particles moving on a surface with no ability to probe its curvature only exhibit steady-state inhomogeneities in the presence of orientational order. We then consider a strongly confined 3D ideal active gas and compute its steady-state density distribution in a box of arbitrary convex shape.
We investigate the transition between the Cassie-Baxter and Wenzel states of a slowly evaporating, micron-scale drop on a superhydrophobic surface. In two dimensions analytical results show that there are two collapse mechanisms. For long posts the d
rop collapses when it is able to overcome the free energy barrier presented by the hydrophobic posts. For short posts, as the drop loses volume, its curvature increases allowing it to touch the surface below the posts. We emphasise the importance of the contact line retreating across the surface as the drop becomes smaller: this often preempts the collapse. In a quasi-three dimensional simulation we find similar behaviour, with the additional feature that the drop can de-pin from all but the peripheral posts, so that its base resembles an inverted bowl.
سجل دخول لتتمكن من نشر تعليقات
التعليقات
جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
