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Deposition of synchrotron‐radiation‐induced carbon contamination on beamline optics causes their performance to deteriorate, especially near the carbon K edge. The photon flux losses due to carbon contamination have spurred researchers to search for a suitable decontamination technique to restore the optical surface and retain its performance. Several in situ and ex situ refurbishing strategies for beamline optics are still under development to solve this serious issue. In this work, the carbon contamination is removed from a large (340 mm × 60 mm) Au‐coated toroidal mirror surface using a capacitively coupled low‐pressure RF plasma. Before and after RF plasma cleaning, the mirror was characterized by Raman spectroscopy, soft X‐ray reflectivity (SXR) and atomic force microscopy (AFM) techniques. The Raman spectra of the contaminated mirror clearly show the G (1575–1590 cm−1) and D (1362–1380 cm−1) bands of graphitic carbon. The SXR curve of the contaminated mirror shows a clear dip near the critical momentum transfer of carbon, indicating the presence of carbon contamination on the mirror surface. This dip disappears after removal of the contamination layer by RF plasma exposure. A decrease in the intensities of the CO bands is also observed by optical emission spectrometry during plasma exposure. The AFM and SXR results suggest that the root‐mean‐square (r.m.s.) roughness of the mirror surface does not increase after plasma exposure. [ABSTRACT FROM AUTHOR]

Abstract: The assembly of disk-shaped molecules on surfaces has drawn considerable attention because of their unique electronic and optical properties. We have studied the monolayer of the amphiphilic tricycloquinazoline (AmTCQ) based disk-shaped molecules at the air–water and air–solid interfaces. The AmTCQ molecules form a stable Langmuir monolayer at the air–water interface. The monolayer exhibits gas phase, low density liquid (L1) phase, and high density liquid (L12) phase. In L1 phase, the molecules prefer face-on conformation with their flexible side-chain being interdigitated with the neighboring molecules. Interestingly, the molecular conformations in L12 phase were found to be both the face-on and edge-on. The structure of the aggregates of the molecules on a surface can be influenced by the intermolecular and molecule–substrate interactions. The deficiency in π-electrons of the AmTCQ molecule may lead to a weak intermolecular interaction. The observation of both the conformations of the molecules in L12 phase can be attributed to the weak intermolecular interaction. [Copyright &y& Elsevier]

Abstract: Octadecanethiol (ODT) is known to form self-assembled monolayer on noble metal surfaces which has potential technological applications. Langmuir–Blodgett (LB) technique is another useful method of obtaining highly ordered assembly of molecules. It is of interest to find whether ODT molecules can also form a stable Langmuir monolayer which facilitates the preparation of LB films. In literature, it has been reported that ODT molecules form an unstable Langmuir monolayer. We have studied the stability of the monolayer of the ODT molecules at air–water interface using surface manometry and microscopy techniques. We find the monolayer to be stable on ultrapure water of resistivity greater than 18MΩcm. However, the behavior changes in the presence of even small amount of additives like NaOH or CdCl2 in the subphase. Our AFM studies on the LB films of ODT deposited from ion-free ultrapure water showed streak-like bilayer domains. The LB films of ODT deposited from CdCl2 containing aqueous subphase yield dendritic domains of the complexed unit grown over ODT monolayer. These nanostructures on surfaces may have potential applications in molecular electronics. [Copyright &y& Elsevier]

The Langmuir monolayer of cholesterol at the air-water interface exhibits a condensed phase in which the cholesterol molecules are aligned normal to the water surface. We have transferred the monolayer from water surface to different substrates by Langmuir-Blodgett (LB) technique and have studied their assembly by atomic force microscope (AFM). Our studies reveal that the aggregation of cholesterol molecules on hydrophobic surfaces leads to interesting structures. The cholesterol molecules assemble into a uniform film, elongated domains and uniformly distributed torus-shaped domains (doughnuts) for one, two and four cycles of deposition, respectively. Beyond four cycles, the molecules adsorb and desorb by an equal amount resulting in no further deposition. The formation of uniformly distributed doughnuts can be attributed to the hydrophobic interaction and reorganization of the molecules due to successive adsorption and desorption during deposition cycles. Our studies on hydrophilic surfaces show that cholesterol cannot form more than one layer of deposition. [ABSTRACT FROM AUTHOR]