In this paper, new nitrogen doped carbon dots with a high quantum yield and novel optical properties were synthesized by a simple and fast one step microwave-assisted synthesis. Citric acid monohydrate was used as a carbon source and 2,2-dimethyl-1,3-propanediamine as nitrogen source. The prepared N-CDs were characterized by Fourier transform infrared, Raman, UV-visible and photoluminescence spectroscopies. Transmission electron microscope (TEM) images revealed that the N-CDs have distinctive flake-shape morphology. The N-CDs exhibit bright blue luminescence and quenching response towards Hg 2þ ions. The quenching sensitivity was investigated.The results indicate a limit of detection as low as 7.63 nM and a linear relationship over the range 0-4.2 μM. In addition, the prepared N-CDs were tested as sensor for pH in the range from 1 to 7.

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NiCoTi spinel ferrite, SrCoTi hexagonal ferrite and copper microparticles were coated with polypyrrole (PPY) using in situ chemical oxidative method. The resulted microwave absorbing material was introduced into polyurethane matrix. XRD patterns indicated the successful preparation of spinel and hexagonal ferrites. SEM micrographs showed the semi-spherical morphology of the prepared composite. The magnetic properties have been investigated using VSM. The microwave absorber with 20%w/w loading percentage exhibits the best microwave absorption performance (bandwidth under −10 dB of 3 GHz and reflection loss of −24 dB at the matching frequency 9.75 GHz and thickness of 1.8 mm). The measurements of permittivity and permeability reveal that the dielectric loss mechanism is the predominant in the current absorber. The measured reflection loss using free space method also indicates the superior performance of the sample with 20%w/w loading percentage.