2I) and this phenomenon manifests that NPDM alone has no direct response to the anions. Therefore, F -anions binded to Al 3+ ions through decomplexating Al 3+ from the NPDM-Al 3+ whole. Thus, assisted by F -anions, the repeatability in case of Al 3+ ions could be achieved. Nevertheless, these negative changes could be countervailable when the Al 3+ concentration is in excess along with the corresponding fluorescence color variations under a UV-lamp ( Fig. ). All the experimental data demonstrated that NPDM is an recyclable "off-on-off" molecular tweezers for Al 3+ and F -.