20 research outputs found
Controlled Functionalization of Graphene Layers
No full textControlled functionalization of graphene layers is one of the most important research objectives in the material chemistry. A well established procedure is the oxidation with strong acids and oxidizing agents often in harsh and dangerous reaction conditions giving products of unknown precise structure. In this chapter, the controlled functionalization of graphene layers with a derivative of serinol is presented, avoiding toxic reagents and dangerous reaction conditions. The derivative is the bio‐based serinol pyrrole, obtained through the neat reaction of serinol with 2,5‐hexanedione; the graphitic substrate was high surface area graphite (HSAG) with high‐shape anisotropy. The functionalization reaction, characterized by a 85% atomic efficiency (water is the only by‐product), evolved with high yields leading to functionalized graphene layers through the controlled introduction of oxygen and nitrogen‐containing functional groups. Sustainable processes were adopted, such as ball milling and heating. The mechanism pathway, the characterization of HSAG and reaction products through a wide range of analytical methods, some successful applications of the adducts are discussed in this chapter. The functionalization left the bulk crystalline structure of the layers substantially unaltered. Stable dispersions in water and eco‐friendly solvents were prepared
Graphene Materials
No full textGraphene is, basically, a single atomic layer of graphite, an abundant mineral that is an allotrope of carbon that is made up of very tightly bonded carbon atoms organized into a hexagonal lattice. What makes graphene so special is its sp2 hybridization and very thin atomic thickness (of 0.345 Nm). These properties are what enable graphene to break so many records in terms of strength, electricity, and heat conduction (as well as many others). This book gathers valuable information about the surface chemistry of graphene, some of its properties (electrical, mechanical, etc.), and many of its modifications that can be taken into account
Effect of the adsorbed film on scanning the hysteresis loop of CH<sub>2</sub>Br<sub>2</sub>/Vycor adsorption isotherm according to theorem-6 of the domain theory.
No full textPoints Λ and Ξ are approached from different routes; ΑΛΞΟ is a primary descending curve originated from the ascending boundary p(x) and CΞDΛC is a loop originated from the descending boundary q(x), α and O are respectively the upper and lower closure points of the adsorption isotherm. The complexion diagrams for common points are shown too; hatched areas indicate the correction needed to be taken into account for the adsorbed film in order theorem-6 to be valid. Note that the thickness of the film increases with pressure.</p
Scanning of Adsorption Hysteresis In Situ with Small Angle X-Ray Scattering.
No full textEverett's theorem-6 of the domain theory was examined by conducting adsorption in situ with small angle x-ray scattering (SAXS) supplemented by the contrast matching technique. The study focuses on the spectrum differences of a point to which the system arrives from different scanning paths. It is noted that according to this theorem at a common point the system has similar macroscopic properties. Furthermore it was examined the memory string of the system. We concluded that opposite to theorem-6: a) at a common point the system can reach in a finite (not an infinite) number of ways, b) a correction for the thickness of the adsorbed film prior to capillary condensation is necessary, and c) the scattering curves although at high-Q values coincide, at low-Q values are different indicating different microscopic states. That is, at a common point the system holds different metastable states sustained by hysteresis effects. These metastable states are the ones which highlight the way of a system back to a return point memory (RPM). Entering the hysteresis loop from different RPMs different histories are implanted to the paths toward the common point. Although in general the memory points refer to relaxation phenomena, they also constitute a characteristic feature of capillary condensation. Analogies of the no-passing rule and the adiabaticity assumption in the frame of adsorption hysteresis are discussed
Complementary paths view in conjunction with Fig 3.
No full textUpper curve (red): Subtraction of the scattering curve at point P from the path ABPC at p/po = 0.571 from the scattering curve at point A at p/po = 0.468 of the same path. Lower curve (cyan): Subtraction of the scattering curve at point P from the loop DZFPGD at p/po = 0.571 from the scattering curve at point D at p/po = 0.665 of the same path. Note that the two curves are symmetrical except at low-Q values indicating that the paths AP and PD are complementary to each other.</p
Scattering curves at various relative pressures around the loop DZFPGD; for full inspection and corresponding letters, view this figure in conjunction with Fig 3.
No full textGreen: p/po = 0.665 point D; red: p/po = 0.571 point Z; pink: p/po = 0.519 point F; cyan: p/po = 0.571 point P; blue: p/po = 0.614 point G. Note that points Z and G although they correspond to almost equal amounts adsorbed their scattering curves red and blue, respectively, have different low-Q distributions indicating different metastabilities.</p
The Effect of Rotation on Gas Storage in Nanoporous Materials
No full textNanoporous materials offer a promising solution for gas storage applications in various scientific and engineering domains. However, several crucial challenges need to be addressed, including adsorptive capacity, rapid loading, and controlled gas delivery. A potential approach to tackle these issues is through rotation-based methods. In this study, we investigate the impact of rotation on CO2 adsorption using activated carbon, both at the early and late stages of the adsorption process. Towards this direction, three sets of experiments were conducted: (i) adsorption isotherm with rotation at each gas loading, (ii) adsorption kinetics with multiple rotations performed in sequence 15 min after CO2 introduction, and (iii) adsorption kinetics with a single rotation after 40 h of adsorption and repetition after another 20 h. For the first two cases, the comparison was performed by respective measurements without rotation, while for the last case, results were compared to a theoretical pseudo-first-order kinetic curve. Our findings demonstrate that rotation enhances the adsorptive capacity by an impressive 54%, accelerates kinetics by a factor of 3.25, and enables controllable gas delivery by adjusting the angular velocity. These results highlight rotation as a promising technique to optimize gas storage in nanoporous materials, facilitating advancements in numerous scientific and engineering applications
The Effect of Nanobubbles on Transdermal Applications
No full textIn the present work, a new method for dermal delivery using nanobubbles (NBs) is investigated. Oxygen NBs are generated in deionized water and used to produce cosmetic formulations with hyaluronic acid as an active ingredient. Nanobubbles result in the improvement of the effect and penetration of the active ingredient through Strat-M, a synthetic membrane that resembles human skin. Experiments conducted with the Franz Cell device confirm the greater penetration of the active ingredient into Strat-M due to NBs, compared to cosmetic formulations that do not contain NBs. The effect of NBs was further examined by measuring UV-Vis and FTIR spectra. A possible mechanism was outlined, too. It was also found that NBs do not change the pH or the FTIR spectrum of the cosmetic serum indicating non-toxicity
Mass fractals for the two different routes ABPC and DZFPGD of Fig 3.
No full textGreen: p/po = 0.665 point D; blue: p/po = 0.571 point Z; cyan: p/po = 0.571 point P from path corresponding to loop; red: p/po = 0.468 point A; and pink: p/po = 0.571 point P from path corresponding to ABPC route. Note that that the mass fractal models of route ABPC (red and pink lines) correspond to larger ξο than those of the loop (green, cyan and blue lines). The former route is originated from the desorption branch whereas the latter from the adsorption branch of the adsorption isotherm, hence the long-range correlations are more pronounced for the former than for the latter route.</p
Effect of air gap on gas permeance/selectivity performance of BTDA‐TDI/MDI copolyimide hollow fiber membranes
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