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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The transport of high intensity, high brightness beams without aberrations in low energy accelerators ͑50-100 keV͒ is the main objective of this work. An analytical approach is used for the design of a single gap accelerating column. The tracing of beam lines inside the accelerating gap shows a decrease of the beam radius with an increase of the accelerating voltage ratio up to the optimal value. Beyond this optimal value the beam line makes a crossover with the axis of the accelerating tube, which indicates the presence of beam aberration. Also the rate of beam emittance growth increases due to the presence of beam aberration. An estimation of the minimum value of the electric field required to contain the beam against space charge expansion is set forth for different gaseous ions.

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