A scalable and solvent‐free chemical process to obtain highly functionalized and dispersible multi‐walled carbon nanotubes is reported. Highly functionalized multi‐walled carbon nanotubes have been prepared using in situ generated aryl diazonium salts in the presence of ammonium persulfate and 2,2′‐azoisobutyronitrile by solvent‐free techniques. In the Raman spectra of the resulting materials, characteristic peaks, the D‐ and G‐bands, are shifted by about 10 cm−1 to lower frequencies. At the same time, the relative intensity ratios between the D‐ and G‐bands increase in comparison to that in the spectrum of the purified product. Fourier‐transform infrared spectroscopy reveals the presence of the functional groups on the surface. Transmission electron microscopy images directly confirm the significant build‐up of sidewall organic moieties on the treated materials. The weight loss of various functional moieties determined by thermogravimetry–differential scanning calorimetry analysis is about 18–33%. The dispersibility of the functionalized materials in solvents, such as chloroform, tetrahydrofuran, and water, is obviously improved.magnified image
Graphene oxide quantum dots (GOQDs) attract great attention for their unique properties and promising application potential. The difficulty in the formation of a confined structure, and the numerous and diverse oxygen-containing functional groups results in a low emission yield to GOQDs. Here, GOQDs with a size of about 5 nm, exfoliated from carbon fibers by microwave irradiation, are detected and analyzed. The exfoliated GOQDs are deeply oxidized and induce large numbers of epoxy groups and ether bonds, but only a small amount of carbonyl groups and hydroxyl groups. The subdomains of sp clusters, involving epoxy groups and ether bonds, are responsible for the two strong photoluminescence emissions of GOQDs under different excitation wavelengths. Moreover, GOQDs tend to self-assemble at the edges of their planes to form self-assembly films (SAFs) with the evaporation of water. SAFs can further assemble into different 3D patterns with unique microstructures such as sponge bulk, sponge ball, microsheet, sisal, and schistose coral, which are what applications such as supercapacitors, cells, catalysts, and electrochemical sensors need. This method for preparation of GOQDs is easy, quick, and environmentally friendly, and this work may open up new research interests about GOQDs.
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