Non-hydrothermal synthesis and optical limiting properties of one-dimensional Se/C, Te/C and Se–Te/C core–shell nanostructures

A single step, nontoxic, non-hydrothermal, low temperature and reproducible method for the preparation of carbon-coated selenium and tellurium nanowires (Se/C and Te/C, respectively), and selenium–telluride (Se–Te/C) nanorods, is presented. Sodium dodecyl sulfate is used as the surfactant, and glucose is employed as the reducing and carbonizing agent. Uncoated nanowires of trigonal Se and Te without the carbon shell are obtained as products, at lower glucose concentrations, whereas at higher glucose concentrations carbon-coated nanowires of trigonal Se and Te are formed. Structural, morphological and compositional properties of the prepared products are examined using X-ray diffraction, scanning electron microscopy, high resolution transmission electron microscopy, and energy dispersive X-ray spectroscopy, respectively. The formation of amorphous carbon shell and the model depicting the growth of core–shell nanowires and nanorods are discussed on the basis of the experimental results. Nonlinear optical transmission of the samples is studied at 532 nm using the open-aperture Z-scan technique employing 5 ns laser pulses. Results show that the samples are efficient optical limiters, and that a three-to-four-fold enhancement in the value of the effective two-photon absorption coefficient (β) can be achieved by coating the nanowires and nanorods with carbon.