contain dendritic structures with a fractal dimension consistent with a diffusionlimited aggregation process. [3,6] Although a variety of degradation prevention techniques have been reported such as encapsulation with hexagonal boron nitride [9] and polymers, [10] use of novel gate dielectrics, [11] and placement in an environment with a desiccant [3] or in a vacuum, [4] such techniques are not applicable for ambientair applications such as gas sensors. To our knowledge, the stability of bilayer (BL) and thicker-layer MoS 2 films in ambient air has not been extensively studied. It is important to understand the stability of such films for developing applications and having a better understanding of ML degradation. In this paper, we report on the structural stability of preheated and as-grown BL and thicker-layer MoS 2 films in ambient air. The films are grown using CVD on SiO 2 substrates and studied using atomic force microscopy (AFM), and Raman and PL spectroscopies.BL and thicker-layer MoS 2 and other TMD films, nanosheets, [12] and nanostructures, [13] although having indirect band gaps, have attracted considerable interest because of their useful properties. For example, BLs and thicker-layers have higher electrical conductivities than MLs due to their higher density of states and more effective screening of impurities in the substrate. [14] In addition, BL device yield is typically higher than ML device yield, due to the greater mechanical strength of BLs. [15,16] BL and thicker-layer TMD films offer layer control of properties such as spin-orbit coupling, [17] interlayer coupling, [18] and band gap. [19] Varying the twist angle between layers in BLs has been reported to result in twist-dependent valley and band alignment, [20] and Moiré pattern excitons. [21] The ambient-air degradation of CVD-grown ML MoS 2 and other ML TMD films was first reported by Gao et al. [3] They observed that ML MoS 2 and WS 2 grown on SiO 2 substrates developed extensive cracking, morphological changes, and quenching of PL after exposure to ambient air at room temperature (RT) for a period of about a year. The degradation was attributed to oxidation along grain boundaries and other defects. It was found that water vapor in the air was necessary for degradation to occur since films did not degrade in a dry box. In addition, Budania et al. [4] reported that mechanically exfoliated thin multilayer MoS 2 flakes on SiO 2 developed speckles in air at a high relative humidity (RH) of 60% over a period of about a year. Kotsakidis et al. [5] reported

Carbon nanotubes (CNTs) are known to be a suitable adsorbent of organic contaminants due to their large surface area and hollow structures; but at the nanoscale, CNTs have poor solubility and can be difficult to remove from solution. Studies have shown that the use of peptides can control the size, shape, and structure of materials during synthesis. In this research, magnetic CNTs were synthesized in a co‐precipitation reaction in the presence of the M6A−B1 peptide to correct these deficiencies in CNTs. Characterization of nanoparticles was facilitated by analytical methods including scanning electron microscopy, infrared spectroscopy, x‐ray diffraction, elemental analysis, and more. Water remediation studies were conducted to study the effect of dye, pH, and adsorbent on the removal of Toluidine Blue O from an aqueous solution. Pseudo‐second order kinetics were used in describing the rate of adsorption while a Langmuir isotherm model was used to study the interaction between the peptide‐functionalized material and the adsorbate. The separation factor, RL, calculated for the studied dye concentrations showed that adsorption with the peptide‐functionalized material was favorable.

Abstract Monolayer (ML) molybdenum disulfide (MoS₂) is a novel 2-dimensional (2D) semiconductor whose properties have many applications in devices. Despite its potential, ML MoS₂ is limited in its use due to its degradation under exposure to ambient air. Therefore, studies of possible degradation prevention methods are important. It is well established that air humidity plays a major role in the degradation. In this paper, we investigate the effects of substrate hydrophobicity on the degradation of chemical vapor deposition (CVD) grown ML MoS2. We use optical microscopy, atomic force microscopy (AFM), and Raman mapping to investigate the degradation of ML MoS2 grown on SiO2 and Si3N4 that are hydrophilic and hydrophobic substrates, respectively. Our results show that the degradation of ML MoS₂ on Si3N4 is significantly less than the degradation on SiO2. These results show that using hydrophobic substrates to grow 2D transition metal dichalcogenide ML materials may diminish ambient degradation and enable improved protocols for device manufacturing.

We report on the properties of defects in exfoliated graphene on SiO2 produced by electron irradiation at 25 keV and dosages from 4.96 × 1015 to 9.56 × 1017 electrons/cm2. With increasing dosage, graphene exhibits the two-stage amorphization trajectory reported for the Ar ion bombardment of graphene. Initially, the ratio of the D-peak height, ID, to the G peak height, IG, increases as new defects are formed. In the second stage, ID/ IG decreases as defects cover most of the sample. In the second stage, we find that the full width at half maximum of the Raman 2 D, D, and G peaks increases by 3, 3, and 6 cm−1, respectively. These values are less by factors of about 10, 5, and 10, respectively, than those reported for amorphous graphene produced by Ar ion bombardment. We find that ID/ IG monotonically decreases in the second stage as the annealing temperature increases from 80 to 220 °C. Assuming that ID/ IG is proportional to the defect density, we find an activation energy for defect healing, Ea = 0.48 eV, which is significantly less than Ea = 0.95 eV reported for vacancies and closer to Ea = 0.29 and 0.58 eV reported for hydrogen and hydroxyl group adsorbates, respectively. We propose that, in the second stage, graphene does not become amorphous, and the defects responsible for the D peak are adsorbates.