Scalable production of water-dispersible reduced graphene oxide and its integration in a field effect transistor

Advances in functional guest materials for resistive gas sensors

Resistive gas sensors are considered promising candidates for gas detection, benefiting from their small size, ease of fabrication and operation convenience. The development history, performance index, device type and common host materials (metal oxide semiconductors, conductive polymers, carbon-based materials and transition metal dichalcogenides) of resistive gas sensors are firstly reviewed. This review systematically summarizes the functions, functional mechanisms, features and applications of seven kinds of guest materials (noble metals, metal heteroatoms, metal oxides, metal-organic frameworks, transition metal dichalcogenides, polymers, and multiple guest materials) used for the modification and optimization of the host materials. The introduction of guest materials enables synergistic effects and complementary advantages, introduces catalytic sites, constructs heterojunctions, promotes charge transfer, improves carrier transport, or introduces protective/sieving/enrichment layers, thereby effectively improving the sensitivity, selectivity and stability of the gas sensors. The perspectives and challenges regarding the host-guest hybrid materials-based gas sensors are also discussed.

Real-time monitored photocatalytic activity and electrochemical performance of an rGO/Pt nanocomposite synthesized via a green approach

Herein, we have reported the real-time photodegradation of methylene blue (MB), an organic pollutant, in the presence of sunlight at an ambient temperature using a platinum-decorated reduced graphene oxide (rGO/Pt) nanocomposite. The photocatalyst was prepared via a simple, one-pot and green approach with the simultaneous reduction of GO and Pt using aqueous honey as a reducing agent. Moreover, the honey not only simultaneously reduced Pt ions and GO but also played a key role in the growth and dispersion of Pt nanoparticles on the surface of rGO. Various rGO/Pt nanocomposites with different percentages of Pt nanoparticles loaded on rGO were obtained by tuning the concentration of the Pt source. The high percentage of Pt nanoparticles with an average size of 2.5 nm dispersed on rGO has shown excellent electrochemical performance. The photocatalytic activity of the rGO/Pt composite was enhanced by increasing the weight percent of the Pt particles on rGO, which led to the formation of a highly efficient photocatalyst. The optimized photocatalyst exhibited remarkable photocatalytic activity and degraded 98% MB in 180 minutes; thus, it can be used for industrial and environmental applications.

Absorption Behavior of Graphene Nanoplates toward Oils and Organic Solvents in Contaminated Water

In this work, graphene nanoplates (GNPs) were successfully prepared via direct chemical exfoliation from natural graphite. The properties of prepared GNPs were investigated using scanning electron microscopy and X-ray diffraction. The resultant GNPs had a low bulk density of 0.015 g mL−1, C content of 99.6%, a lateral diameter of 5–15 µm, and thickness of <15 nm, respectively. The absorption capacity of the GNPs for a range of oils and organic solvents including pump oil, polydimethylsiloxane oil (PDMS), dioctyl phthalates (DOP) oil, olive oil, bean oil, mazut oil, xylene, ethanol, and ethylene glycol (EG) was evaluated. The effects of the sorption conditions such as the absorption time (sorption kinetics), temperature, and aging manner (static, stirring, and ultrasonic) on the absorption capability of the GNPs were also investigated. It could be seen that the GNPs revealed extremely high absorption capacities for oil and organic solvents, reaching 21–42 times their own weight only after 2 min of absorption at room temperature, which were found to be much higher than those shown by various commercially available absorbents.

One-step reducing and dispersing graphene oxide via hydroxypropyl hydrazine and its applications in Cu2+ removal

Graphene is widely used in numerous scientific fields including physics, chemistry and materials science due to its exceptional electrical, thermal, optical and mechanical properties. However, the poor solubility/dispersibility strongly limits the practical applications of graphene. In this work, hydroxypropyl hydrazine (HPH) was synthesized to reduce graphene oxide (GO) under mild conditions. The as-produced graphene sheets with a 3D-porous structure show admirable dispersion stability in N,N-dimethylacetamide (DMAc) and the graphene sheets are more effective absorbents for Cu²⁺ removal than those reduced by hydrazine hydrate. A mechanism for removal of epoxides and carboxides from GO by HPH has been proposed. This one-step reducing and dispersing process of GO is more efficient, environmentally benign and safer for the bulk-scale production of 3D porous graphene.

Safety Assessment of Graphene-Based Materials: Focus on Human Health and the Environment

Graphene and its derivatives are heralded as "miracle" materials with manifold applications in different sectors of society from electronics to energy storage to medicine. The increasing exploitation of graphene-based materials (GBMs) necessitates a comprehensive evaluation of the potential impact of these materials on human health and the environment. Here, we discuss synthesis and characterization of GBMs as well as human and environmental hazard assessment of GBMs using in vitro and in vivo model systems with the aim to understand the properties that underlie the biological effects of these materials; not all GBMs are alike, and it is essential that we disentangle the structure-activity relationships for this class of materials.