General and simple approach for visual detection of chromium (VI) ions using three-dimensional nanoscale structures

The design of optical chemical nanosensors were successfully developed for simple and high-speed detection of toxic Cr(VI) ions. The systematic design of the optical nanosensors was based on densely patterned a chromogenic receptor, namely, diphenylcarbazide (DPC), as a selective binding site onto three-dimensional (3D) nanoscale structures. The ability to precisely modify the nanoscale pore surfaces with DPC probe enables efficient sensing responses as a result of Cr(VI)-DPC binding events. In this approach, a dense dispersion of cationic surfactant such as DDAB enabled of the surface-enhanced polarity of the 3D carriers, which led to successful design of DPC-based nanosensors. In addition, the use of DDAB as modifier enhanced the accessibility and adsorptive characteristics of the DPC probe onto the 3D carriers with retaining the intrinsic mobility of the fabricated nanosensors. Such flexibility in the fabricated nanosensors led to high flux of the Cr(VI) ions to DPC probe without significant kinetic hindrance. The synthetic nanosensor can be used for an effective recognition of Cr(VI) ions to low level of concentrations in the range of 10^-10-10^-6 M (i.e. 0.07 ppb-200 ppb) with rapid response time (in the order of seconds). Moreover, these new classes of the design-made hybrid nanosensors exhibited long-term stability of signaling and recognition functionalities that in general provided extraordinary sensitivity, selectivity, reusability, and fast kinetic detection and quantification of various deleterious metal ions in our environment.