Tryptophan-functionalized gold nanoclusters used as a fluorescence sensor for alizarin determination.

In terms of the superior performance of gold nanoclusters (Au NCs) and the ubiquitous tryptophan in higher plants, tryptophan stabilized gold nanoclusters (Try@Au NCs) were synthesized through chemical reduction method. The uniformly dispersed Au NCs emitted blue fluorescence at 448 nm when the excitation wavelength was located at 368 nm. On the basis of inner filter effect, Try@Au NCs was used as a turn-off fluorescence nanoprobe for simple and quick detection of alizarin. The water-soluble Try@Au NCs displayed excellent stability under various conditions which was beneficial for practical application. This as-prepared fluorescence nanosensor displayed noticeable sensitivity and selectivity toward alizarin measurement with a detection linear range of 0.5-100 μM and detection limit of 0.092 μM. The satisfactory results of recovery assay stated that this as-developed nanosensor was great promising for alizarin detection in real samples.