Effect of pH conditions on the depolymerization of Wucaiwan coal by mixed acids/ultrasound method and the product structures and performance

Abstract The cleavage of the aliphatic chain or ether bond connecting the polycyclic aromatic hydrocarbons in coal can be achieved by not only hydrogenation reduction but also oxidative acid treatment. In this paper, coal samples from Wucaiwan in Xinjiang were pretreated with HNO3 followed by mixed acids/ultrasound treatment. The depolymerized coal samples obtained under different pH conditions were then separated by fractional washing. The structures and properties of the resulting coal samples were studied by elemental analysis, FT-IR, XRD, TG–DTA, TEM, UV–Vis, and PL. The results showed that when pH = 0.012, the obtained coal samples were fragments stripped off from the raw coal samples by ultrasound in strong acid conditions, aliphatic hydrocarbons linked with oxygen-containing groups such as nitro group, a small amount of small aromatic molecules and mineral salts; when pH = 1.99–4.09, the obtained coal samples were polycyclic aromatic hydrocarbons linked with oxygen-containing groups such as nitro group,possessing the annulus wall of multilayer graphene fragment structures built up by sp2 carbons, and they are typical fluorescent substances of carbon nanoparticle structure. The former has no solubility in organic solvents, while the latter can be well dissolved in polar solvents such as acetone. All the depolymerized coal samples obtained under different pH conditions exhibited good absorption and ability of fluorescence emission. Graphical Abstrac

Facile One-Step Sonochemical Synthesis and Photocatalytic Properties of Graphene/Ag3PO4 Quantum Dots Composites

Abstract In this study, a novel graphene/Ag3PO4 quantum dot (rGO/Ag3PO4 QD) composite was successfully synthesized via a facile one-step photo-ultrasonic-assisted reduction method for the first time. The composites were analyzed by various techniques. According to the obtained results, Ag3PO4 QDs with a size of 1–4 nm were uniformly dispersed on rGO nanosheets to form rGO/Ag3PO4 QD composites. The photocatalytic activity of rGO/Ag3PO4 QD composites was evaluated by the decomposition of methylene blue (MB). Meanwhile, effects of the surfactant dosage and the amount of rGO on the photocatalytic activity were also investigated. It was found that rGO/Ag3PO4 QDs (WrGO:Wcomposite = 2.3%) composite exhibited better photocatalytic activity and stability with degrading 97.5% of MB within 5 min. The improved photocatalytic activities and stabilities were majorly related to the synergistic effect between Ag3PO4 QDs and rGO with high specific surface area, which gave rise to efficient interfacial transfer of photogenerated electrons and holes on both materials. Moreover, possible formation and photocatalytic mechanisms of rGO/Ag3PO4 QDs were proposed. The obtained rGO/Ag3PO4 QDs photocatalysts would have great potentials in sewage treatment and water splitting

Additional file 1: of Facile One-Step Sonochemical Synthesis and Photocatalytic Properties of Graphene/Ag3PO4 Quantum Dots Composites

Figure S1. TEM images of rGO/Ag3PO4 QDs (stirring method). Figure S2. The plots of (ιhν)2 versus Eg of Ag3PO4 QDs, R-1.5, R-2, R-2.3, R-2.5, and R-3. Figure S3. (a) Photocatalyticdegradation of MB by R-2.3 prepared by different mass of surfactant and (b) apparent rate constants (k) of samples for photocatalytic degradation of MB. Figure S4. (a) Photocatalytic degradation of MB, MO, and RhB byR-2.3, (b) apparent rate constants (k) of sample for photocatalytic degradation of dyes. (ZIP 12230 kb

Flexible Graphene–Graphene Composites of Superior Thermal and Electrical Transport Properties

Graphene is known for high thermal and electrical conductivities. In the preparation of neat carbon materials based on graphene, a common approach has been the use of well-exfoliated graphene oxides (GOs) as the precursor, followed by conversion to reduced GOs (rGOs). However, rGOs are more suitable for the targeted high electrical conductivity achievable through percolation but considerably less effective in terms of efficient thermal transport dictated by phonon progression. In this work, neat carbon films were fabricated directly from few-layer graphene sheets, avoiding rGOs completely. These essentially graphene–graphene composites were of a metal-like appearance and mechanically flexible, exhibiting superior thermal and electrical transport properties. The observed thermal and electrical conductivities are higher than 220 W/m·K and 85000 S/m, respectively. Some issues in the further development of these mechanically flexible graphene–graphene nanocomposite materials are discussed and so are the associated opportunities