Effect of Pretreatment Conditions on the Precise Nanoporosity of Graphene Oxide

Nanoscale pores in graphene oxide (GO) control various important functions. The nanoporosity of GO is sensitive to low-temperature heating. Therefore, it is important to carefully process GO and GO-based materials to achieve superior functions. Optimum pretreatment conditions, such as the pre-evacuation temperature and time, are important during gas adsorption in GO to obtain accurate pore structure information. This study demonstrated that the pre-evacuation temperature and time for gas adsorption in GO must be approximately 333–353 K and 4 h, respectively, to avoid the irreversible alteration of nanoporosity. In situ temperature-dependent Fourier-transform infrared spectra and thermogravimetric analysis–mass spectrometry suggested significant structural changes in GO above the pre-evacuation temperature (353 K) through the desorption of “physically adsorbed water” and decomposition of unstable surface functional groups. The nanoporosity of GO significantly changed above the aforementioned pre-evacuation temperature and time. Thus, standard pretreatment is indispensable for understanding the intrinsic interface properties of GO

Sustainable and Versatile CuO/GNS Nanocatalyst for Highly Efficient Base Free Coupling Reactions

A CuO nanoparticles (CuO NPs)/graphene nanosheet (GNS) hybrid was prepared by a very simple method and employed as a nanocatalyst (CuO/GNS) for base free coupling reactions, namely, A³-coupling and <i>aza</i>-Michael reactions. TEM shows that CuO NPs of below ∼35 nm size are homogeneously dispersed on the GNS. Strong adhesion between CuO NPs and GNS was acknowledged by a high Raman <i>I</i>_D/<i>I</i>_G ratio and XPS result. The BET surface area of CuO/GNS was found to be 66.26 m² g^–1. The EDS and XPS investigations revealed that the weight percentage and chemical state of Cu in CuO/GNS were 4.46% and +2, respectively. Under mild reaction conditions, CuO/GNS exhibited an outstanding catalytic activity in terms of yield, turnover number (TON) and turnover frequency (TOF) toward A³-coupling reaction. A small amount of catalyst (10 mg, 0.7 mol % of Cu) is enough to carry out the reactions with a wide range of substrates. The CuO/GNS is stable, heterogeneous in nature and reusable for at least five times without any significant loses of yield. N-oxidation of tertiary amines was also carried out to explore further the activity of CuO/GNS, and the results are found to be excellent. Versatility of the CuO/GNS was realized from the superior catalytic activity of used CuO/GNS in <i>aza</i>-Michael reaction. Finally, GNS (∼95%) and CuO (as CuCl₂) were successfully recovered from the used CuO/GNS and confirmed by TEM, Raman, XPS, XRD and SEM-EDS analyses

Formation and Properties of Selenium Double-Helices inside Double-Wall Carbon Nanotubes: Experiment and Theory

We report the production of covalently bonded selenium double-helices within the narrow cavity inside double-wall carbon nanotubes. The double-helix structure, characterized by high-resolution transmission electron microscopy and X-ray diffraction, is completely different from the bulk atomic arrangement and may be considered a new structural phase of Se. Supporting <i>ab initio</i> calculations indicate that the observed encapsulated Se double-helices are radially compressed and have formed from free Se atoms or short chains contained inside carbon nanotubes. The calculated electronic structure of Se double-helices is very different from the bulk system, indicating the possibility to develop a new branch of Se chemistry

Essential Role of Viscosity of SWCNT Inks in Homogeneous Conducting Film Formation

Newly developed inorganic single-wall carbon nanotube (SWCNT) inks of the Zn/Al complex and colloidal silica give a quite homogeneous SWCNT film on the polyethylene terephthalate (PET) substrate by the bar-coating method, whereas the surfactant-based SWCNT inks of sodium dodecyl sulfonate (SDS) and sodium dodecyl benzene sulfonate (SDBS) cannot give a homogeneous film. The key properties of SWCNT inks were studied for the production of homogeneous SWCNT films. The contact angle and surface tension of the inorganic dispersant-based SWCNT inks were 70° and 72 mN m^–1, respectively, being close to those of water (71.5° and 71 mN m^–1). The viscosity was significantly higher than that of water (0.90 mPa·s), consequently, providing sufficient wettability, spreadability, and slow drying of the ink on the substrate, leading to homogeneous film formation. On the other hand, the surfactant dispersant-aided SWCNT inks have the contact angle and surface tension twice lower than the inorganic dispersant-based SWCNT inks, guaranteeing better wettability and spreadability than the inorganic dispersant-based inks. However, the small viscosity close to that of water induces a heterogeneous flow of SWCNT ink on rapid drying, leading to inhomogeneous film formation

Even- and odd-chain saturated fatty acids in serum phospholipids are differentially associated with adipokines

<div><p>Background</p><p>Saturated fatty acids are generally thought to have detrimental effects on health. However, a recent study showed that even- and odd-chain saturated fatty acids had opposite associations with type 2 diabetes. Limited studies of Western populations examined the associations of circulating saturated fatty acids with adipokines, an important role in glucose metabolism.</p><p>Objective</p><p>We examined the associations of saturated fatty acids in serum phospholipids with circulating levels of adipokines among a Japanese population.</p><p>Design</p><p>A cross-sectional study was conducted among 484 Japanese employees (284 men and 200 women) aged 20–65 years. The serum fatty acid composition in the phospholipid fraction was measured by gas-chromatography. Serum leptin, adiponectin, plasminogen activator inhibitor-1 (PAI-1), resistin, and visfatin were measured using a Luminex suspension bead-based multiplexed array. Multiple linear regression analysis was performed to assess the association between saturated fatty acids and adipokines, with adjustment for potential confounding variables.</p><p>Results</p><p>Even- and odd-chain saturated fatty acids were differentially associated with adipokines. Higher levels of even-chain saturated fatty acids (14:0 myristic, 16:0 palmitic, and 18:0 stearic acids) were associated with higher levels of resistin (P for trend = 0.048) and lower levels of adiponectin (P for trend = 0.003). By contrast, odd-chain saturated fatty acids (15:0 pentadecanoic and 17:0 heptadecanoic acids) showed inverse associations with leptin and PAI-1 (P for trend = 0.048 and 0.02, respectively). Visfatin was positively associated with both even- and odd-chain saturated fatty acids.</p><p>Conclusions</p><p>The results suggest that even- and odd-chain saturated fatty acids are differentially associated with adipokine profile.</p></div

Multivariate adjusted geometric means (and 95% confidence interval) for adipokines among phospholipids saturated fatty acids.

<p>Multivariate adjusted geometric means (and 95% confidence interval) for adipokines among phospholipids saturated fatty acids.</p

Characteristics of participants^a.

<p>Characteristics of participants<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0178192#t001fn001" target="_blank">^a</a>.</p

Molecular Dynamics Study of Carbon Nanotubes/Polyamide Reverse Osmosis Membranes: Polymerization, Structure, and Hydration

Carbon nanotubes/polyamide (PA) nanocomposite thin films have become very attractive as reverse osmosis (RO) membranes. In this work, we used molecular dynamics to simulate the influence of single walled carbon nanotubes (SWCNTs) in the polyamide molecular structure as a model case of a carbon nanotubes/polyamide nanocomposite RO membrane. It was found that the addition of SWCNTs decreases the pore size of the composite membrane and increases the Na and Cl ion rejection. Analysis of the radial distribution function of water confined in the pores of the membranes shows that SWCNT+PA nanocomposite membranes also exhibit smaller clusters of water molecules within the membrane, thus suggesting a dense membrane structure (SWCNT+PA composite membranes were 3.9% denser than bare PA). The results provide new insights into the fabrication of novel membranes reinforced with tubular structures for enhanced desalination performance

Enhanced CO₂ Adsorptivity of Partially Charged Single Walled Carbon Nanotubes by Methylene Blue Encapsulation

We prepared a partially charged single walled carbon nanotube (SWCNT) by charge transfer-mediated encapsulation of methylene blue (MB) molecules, which enhances the CO₂ adsorptivity. The liquid phase adsorption of MB molecules on SWCNT could give the MB-encapsulated SWCNT, which was evidenced by the remarkable depression of the X-ray diffraction intensity from the ordered bundle structure, the decrease of N₂ and H₂ adsorption in the internal tube spaces of SWCNT, and the high-resolution transmission electron microscopic observation. The molecular spectroscopic examination revealed the charge transfer interaction between the encapsulated MB molecules and SWCNT. The electrical conductivity increased by the encapsulation of MB suggested the electron transfer from SWCNT to MB molecules, giving rise to positively charged SWCNT. The enhancement of CO₂ adsorption by the MB-encapsulation coincided with the positively charged SWCNT

Aqueous Nanosilica Dispersants for Carbon Nanotube

Nanosilicas can disperse single-wall carbon nanotube (SWCNT) in aqueous solution efficiently; SWCNTs are stably dispersed in aqueous media for more than 6 months. The SWCNT dispersing solution with nanosilica can produce highly conductive transparent films which satisfy the requirements for application to touch panels. Even multiwall carbon nanotube can be dispersed easily in aqueous solution. The highly stable dispersion of SWCNTs in the presence of nanosilica is associated with charge transfer interaction which generates effective charges on the SWCNT particles, giving rise to electrostatic repulsion between the SWCNTs in the aqueous solution. Adhesion of charged nanosilicas on SWCNTs in the aqueous solution and a marked depression of the S₁₁ peak of optical absorption spectrum of the SWCNT with nanosilicas suggest charge transfer interaction of nanosilicas with SWCNT. Thus-formed isolated SWCNTs are fixed on the flexible three-dimensional silica jelly structure in the aqueous solution, leading to the uniform and stable dispersion of SWCNTs