Synthesis and luminescence mechanism of multicolor-emitting g-C3N4 nanopowders by low temperature thermal condensation of melamine.

Graphite like C3N4 (g-C3N4) was synthesized facilely via the low temperature thermal condensation of melamine between 300-650°C. The results showed that the products maintained as melamine when the temperature is below 300°C. With the increase of temperature, the products were transformed into carbon nitride and amorphous g-C3N4 successively. The morphology of products was changed from spherical nanoparticles of melamine into layer carbon nitride and g-C3N4 with the increase of temperature. The photoluminescence spectra showed that the carbon nitride products have continuous tunable photoluminescence properties in the visible region with increasing temperature. With the help of steady state, transient state time-resolved photoluminescence spectra and Raman microstructural characterization, a novel tunable photoluminescence mechanism was founded systematically, which is mainly related to the two dimensional π-conjugated polymeric network and the lone pair of the carbon nitride.

Controllable fabrication and broadband near-infrared luminescence of various Ni2+-activated ZnAl2O4 nanostructures by a single-nozzle electrospinning technique.

By finely tuning the electrospun parameters (feeding rate of solution, working voltage and distance, etc.) and concentration of inorganic salts, various ZnAl(2)O(4) nanostructures (nanoparticles, nanonecklaces, nanofibers, nanotubes and hollow micromelts) were controllably synthesized by a single-nozzle electrospinning technique. The formation mechanisms of different ZnAl(2)O(4) nanostructures, including 'oriented attachment' mechanism, 'gas-push' mechanism, etc., were proposed to elucidate the morphology of the nanostructures and microstructure evolvement process. The morphology and microstructure of calcined electrospun nanostructures were considered to be mainly dependent on two factors, i.e. concentration of inorganic salts and size of as-prepared electrospun nanofibers. Using Ni(2+) ions as activators, broadband near infrared (NIR) emission covering 1000-1400 nm peaking at about 1176 nm was detected in Ni(2+)-doped ZnAl(2)O(4) nanostructures. The broadband NIR emission at around 1.3 µm optical communication window with a long lifetime of ~640 µs makes Ni(2+)-doped ZnAl(2)O(4) nanostructures as a promising candidate for micro/nano-broadband optical amplifiers, fibers, etc.