Mechanism of Cd(II) and Cu(II) Adsorption onto Few-Layered Magnetic Graphene Oxide as an Efficient Adsorbent.

Heavy metal contamination caused by industrial discharge is a challenging environmental issue. Herein, an efficient adsorbent based on few-layered magnetic graphene oxide (FLMGO) was fabricated, characterized, and utilized to remove aqueous Cd(II) and Cu(II). Results present that the two components graphene oxide (GO) and Fe3O4 of FLMGO promote mutually, enabling FLMGO to outperform either GO or Fe3O4. Specifically, FLMGO adsorbs Cd(II) and Cu(II) with adsorption quantities of 401.14 and 1114.22 mg·g-1 in 5 and 7 min, respectively. Moreover, FLMGO can be readily recovered via magnetic separation using a hand-held magnet. Adsorptions are spontaneous, endothermic, and entropy increasing, which are the best described by the Freundlich and pseudo-second-order model. The interaction mechanism is as follows: lone pair electrons in C=O- and C-O-related groups were coordinated toward Cd(II) and Cu(II) to induce chemical interaction. The high adsorption efficiency endows FLMGO with encouraging application potential in heavy metal remediation.

Synthesis of bifunctional fluorescent nanohybrids of carbon dots-copper nanoclusters via a facile method for Fe3+ and Tb3+ ratiometric detection.

In this work, a dual-emission ratiometric fluorescent probe of carbon dots-copper nanoclusters (CDs-Cu NCs) nanohybrids with bifunctional features was successfully assembled through mechanical mixing. The CDs were synthesized using ascorbic acid as a carbon source, and Cu NCs were prepared using d-penicillamine as the stabilizer and reducing agent. The as-prepared CDs-Cu NCs displayed two emission peaks (blue at 424 nm and red at 624 nm) when excited at 360 nm, and showed great stability. Interestingly, trace amount of Fe3+ could lead to the aggregation of Cu NCs, and induce a drastic static fluorescence quenching at 624 nm because of the electrostatic combination between them, while the fluorescence of the emission peak at 424 nm remained constant. Moreover, an attractive fluorescence enhancement phenomenon at 424 nm was observed when trace Tb3+ was added to the above system, which may due to the combination of fluorescence resonance energy transfer (FRET) and photo-induced electron transfer (PET) mechanisms. Thus, CDs-Cu NCs were applied for the ratiometric detection of Fe3+ and Tb3+ in aqueous solution, and the detection limit (3σ/slope) was 45 nM and 62 nM with the linear range from 0.01 to 40 µM and 0.1 to 50 µM, respectively. Furthermore, the developed sensor was successfully applied for the detection of Fe3+ and Tb3+ in real-water samples.

Synthesis of 1,3-dicarbonyl-functionalized reduced graphene oxide/MnO2 composites and their electrochemical properties as supercapacitors.

A novel 1,3-dicarbonyl-functionalized reduced graphene oxide (rDGO) was prepared by N-(4-aminophenyl)-3-oxobutanamide interacting with the epoxy and carboxyl groups of graphene oxide. The high-performance composite supercapacitor electrode material based on MnO2 nanoparticles deposited onto the rDGO sheet (DGM) was fabricated by a hydrothermal method. The morphology and microstructure of the composites were characterized by field-emission scanning electron microscopy, transmission electron microscopy, Raman microscopy and X-ray photoelectron spectroscopy. The obtained results indicated that MnO2 was successfully deposited on rDGO surfaces. The formed composite electrode materials exhibit excellent electrochemical properties. A specific capacitance of 267.4 F g-1 was obtained at a current density of 0.5 A g-1 in 1 mol L-1 H2SO4, while maintaining high cycling stability with 97.7% of its initial capacitance after 1000 cycles at a current density of 3 A g-1. These encouraging results are useful for potential energy storage device applications in high-performance supercapacitors.

High-Efficient Liquid Exfoliation of Boron Nitride Nanosheets Using Aqueous Solution of Alkanolamine.

As one of the simple and efficient routes to access two-dimensional materials, liquid exfoliation has received considerable interest in recent years. Here, we reported on high-efficient liquid exfoliation of hexagonal boron nitride nanosheets (BNNSs) using monoethanolamine (MEA) aqueous solution. The resulting BNNSs were evaluated in terms of the yield and structure characterizations. The results show that the MEA solution can exfoliate BNNSs more efficiently than the currently known solvents and a high yield up to 42% is obtained by ultrasonic exfoliation in MEA-30 wt% H2O solution. Finally, the BNNS-filled epoxy resin with enhanced performance was demonstrated.

High-efficient Synthesis of Graphene Oxide Based on Improved Hummers Method.

As an important precursor and derivate of graphene, graphene oxide (GO) has received wide attention in recent years. However, the synthesis of GO in an economical and efficient way remains a great challenge. Here we reported an improved NaNO3-free Hummers method by partly replacing KMnO4 with K2FeO4 and controlling the amount of concentrated sulfuric acid. As compared to the existing NaNO3-free Hummers methods, this improved routine greatly reduces the reactant consumption while keeps a high yield. The obtained GO was characterized by various techniques, and its derived graphene aerogel was demonstrated as high-performance supercapacitor electrodes. This improved synthesis shows good prospects for scalable production and applications of GO and its derivatives.