Abstract
We are presenting new fluorescent nanoparticles (NPs) made from silica or polystyrene. Such NPs are potentially useful for purposes of cellular imaging and sensing. The NPs were surface-modified with amino groups, and longwave absorbing and emitting dyes were then conjugated, via their reactive chloro atoms, to the NPs. The reactions proceed at temperatures of around 65 degrees C and in predominantly aqueous solution, and are accompanied by a color change from typically green to blue. By analogy to other labels giving this effect, we refer to such dyes as chameleon labels. All NPs were characterized in terms of size, by absorption and emission spectroscopy, thermogravimetry and zeta potentials. The chameleon effect also was used to detect the presence of minute quantities of amino groups on the surface of NPs, both by absorptiometry and, with particular sensitivity, by fluorescence.