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Abstract-A novel polarization reconfigurable planar lowprofile antenna is presented. The antenna consists of an electronically reconfigurable polarizer and a slot antenna. The polarizer is loaded by PIN diodes and by changing the states of the PIN diodes, the linearly polarized (LP) wave generated by the slot antenna can be converted to either right-hand circularly polarized (RHCP) or left-hand circularly polarized (LHCP) wave. The polarizer contains 16 unit cells, which are arranged as a 4×4 array. Each of the unit cells has two layers and is printed on two sides of the substrate. The presented antenna radiates RHCP waves when the PIN diodes of top side are ON while it radiates LHCP waves when the PIN diodes of bottom side are ON. An analysis of the antenna is provided by using equivalent circuits. To verify the design concept, one prototype at 2.5 GHz band is designed and fabricated. Good agreement between the measurement and simulation results is obtained. The measured results show that the antenna achieves a gain better than 8.5 dBic in both RHCP and LHCP with 70% aperture efficiency. It is also shown that the presented design can be easily extended to the design of large-scale arrays without increasing the complexity of the DC bias circuit. The advantages of the proposed design are simple planar structure, low profile, flexibility in designs, high isolation between DC bias circuit and RF signals, high power handling, high gain and low cost. The proposed design can also be applied to the design of antennas at other frequency bands.

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Although gold nanorods capped with hexadecyltrimethylammonium bromide (CTAB) have been prepared through the seed-mediated method for their use in diagnostics and therapeutics, the toxicity of AuNRs@CTAB limits their practical applications in the biomedical field. In this work, the synthesis and tuning of gold nanorods at very low concentrations of CTAB (as low as 0.008 M) was successfully achieved by using the seed-mediated method. Furthermore, we managed to optimize the growth conditions by changing the amount of seeds, AgNO 3 , and/or HCl. At low CTAB concentrations, gold nanorods with tunable size and aspect ratio, high monodispersity, and high purity were obtained and studied by UV–vis spectroscopy, transmission electron microscopy, and Mie–Gans theoretical calculations. This work revealed a method of nanoparticle growth that may be extended to synthesize other nanomaterials such as Ag, Cu, Pd, and Pt at such low CTAB concentrations.