Size-dependent modulation of fluorescence and light scattering: a new strategy for development of ratiometric sensing†
Simultaneous response of fluorescence and light scattering can be obtained by using nanomaterials with size- and shape-dependent physiochemical properties. On the basis of this principle, we report a new strategy to design ratiometric sensors by combining fluorescence and light scattering, two different and independent signals. To obtain fluorescence and scattering signals simultaneously under the same excitation, two signal collection strategies are proposed based on the principles of fluorescence, light scattering and diffraction. One is to collect normal (down-conversion) fluorescence and second-order scattering (SOS) signals, and the other is to record the fluorescence excited by the second-order diffraction light of excitation wavelength λ/2 (SODL-fluorescence) and first-order scattering (FOS) or frequency doubling scattering (FDS) signals. A proof of concept study has been performed by using a carbon dots (CDs) and cobalt oxyhydroxide (CoOOH) nanoflakes system for ascorbic acid (AA) sensing. Apart from construction of ratiometric sensors, the combined fluorescence and scattering can also act as a useful technique to monitor aggregation-induced fluorescence quenching or enhancement.