Langmuir最新文献

Charge transfer due to a water–air contact line moving over a fluoropolymer hydrophobic surface is investigated for an aqueous solution containing surface-active molecules. It is found that anionic (SDS) and neutral (Triton X-100) surfactants exhibit a two-stage charge transfer reduction with concentration. At low concentrations, a layer of surfactant molecules accumulates near the hydrophobic surface and partially quenches the charge transfer. Surprisingly, after this first stage, the charge transfer remains nearly constant or weakly increasing, while the concentration of surfactants increases several orders of magnitude. Eventually, for large enough concentrations, the charge transfer continues to decrease, eventually resulting in almost zero charge transfer before reaching the critical micelle concentration. For the cationic surfactant (CTAB), the behavior is entirely different and a single quenching mechanism can explain the observed reduction in charge transfer due to positively charged surface-active molecules forming a layer that electrostatically screens the water-induced negative charge residing on the hydrophobic interface. A similar behavior is observed for poly(vinyl alcohol), which is attributed to its known and strong interaction with the hydrophobic surface used in this study.

Reflection interference contrast microscopy (RICM, also known as interference reflection microscopy) and related techniques have become of wide interest to the biophysical, soft matter, and biochemistry communities owing to their exquisite sensitivity for characterizing thin films or individual nanoscopic objects adsorbed onto surfaces, or for monitoring cell–substrate interactions. Over the recent years, striking progress has been made to improve the sensitivity and the quantitative analysis of RICM. Its use in more complex environments, with spurious reflections stemming from a variety of structures in the sample, remains however challenging. In this paper, we demonstrate two optical sectioning methods that effectively reduce such background and can be readily implemented in a conventional RICM setup: line confocal detection and structured illumination microscopy. We characterize experimentally the benefits to image quality and demonstrate the use of the methods for quantitative imaging of complex biological and biomimetic samples: cellular membranes, thin organic films, biofunctional surfaces. We then discuss the benefits of each method and provide guidelines to arbitrate between sectioning and signal-to-noise ratio. Finally, we provide a detailed description of our experimental setup and a home-written image acquisition and processing software that should allow the interested reader to duplicate such a setup on a home-built or commercial microscope.

A straightforward, single-stage hydrothermal approach was utilized to synthesize a unique CuO@rGO-MoS₂ nanocomposite, featuring a nest-mimicking architecture. It has highly efficient heterogeneous catalyzed property that can catalyze and activate the peroxymonosulfate (PMS) by means of radical (•OH, SO₄^•–, and O₂^•–) and nonradical (¹O₂) pathways to generate ROS for the rapid degradation of the organic dye rhodamine B (Rh.B). Graphene oxide, which has high specific surface, serves as an excellent carrier which achieves a homogeneous dispersion of the main catalyst component and gives a series of oxygen-containing functional groups that become active centers for nonradical route activation. Through experimental and DFT calculation, it was revealed that MoS₂ as a cocatalyst accelerated the redox cycle of the Cu active center during the activation of PMS via catalysis, further enhancing the catalytic activity of the nanocomposites. And thus the CuO@rGO-MoS₂/PMS system with bird’s-nest like structure achieves rapid degradation of Rh.B in a short period, and the decomposition efficiency of Rh.B reaches 99% within 30 min duration of the reaction. Besides, this system exhibits excellent resistance to environmental interference, demonstrating commendable degradation efficiency across broad pH spectrum (pH 5–11) and high levels of common interfering ions (Cl^–, NO₃^–, SO₄^2–, etc.). To conclude, this study tried to propose and validate a catalyst design idea based on catalytic activation of peroxymonosulfate by selecting appropriate main catalysts, cocatalysts, and catalyst carriers to achieve improved catalytic performance and stability of the catalysts, and the synthesized catalysts CuO@rGO-MoS₂ by this design strategy have shown good degradation performances in real wastewater.