A new strategy for determination of trace PO43− using CNDAu as resonance Rayleigh scattering and fluorescence dual-mode probe.

• Gold-doped carbon nitride dots were prepared by microwave procedure. • The fluorescence and RRS signals are linear to phosphate concentration. • The FL/RRS coupled dual-mode method was accurate and sensitive. The hydrophilic carbon nitride dots (CNDs) and gold-carbon nitride dots (CND Au) were prepared by microwave digestion instrument with citric acid, thiourea and chloroauric acid as precursors. The morphology and properties of the nanomaterial were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), resonance Rayleigh scattering (RRS), fluorescence (FL), Fourier transform infrared spectrometer (FTIR) and particle size analysis. The acidified ammonium molybdate and CNDs are combined to form complex by intermolecular forces, the system's fluorescence and RRS signals are decreased. After adding PO 4 3−, the ammonium molybdate and PO 4 3− form stable phosphomolybdate heteropoly acid (PMo) with hydrophobic properties, the PMo particles are separated from CNDs, and the released CNDs lead to the increase of FL signal. At the same time, PMo particles are simultaneously aggregate forming large particles, which are manifested by an increase in the RRS signal. We can establish a sensitive, rapid, selective method for the determination of trace PO 4 3− by combining RRS and FL signals. Within a certain range, the signals of the two methods show a linear relationship with the concentration of PO 4 3−. The linear range of dual-mode determination method is 1.4–21 nmol/L PO 4 3−, with a detection limit of 0.60 nmol/L. [ABSTRACT FROM AUTHOR]