(Ce0.9Tb0.1)PO4 monospheres ((similar to)1.39 +/- 0.11 mu m) of negligible aggregation and high geometric uniformity were synthesized via microwave assisted homogeneous precipitation, whose luminescence responses toward MnO4- oxidant and vitamin C reductant were studied in detail. Through exciting Ce3+ with 275 nm UV light, strong and broad UV emission centered at (similar to)350 nm (FWHM (similar to)40 nm) and sharp green emission at (similar to)544 nm (FWHM (similar to)10 nm) were obtained, and efficient Ce3+ -> Tb3+ energy transfer, with an efficiency of (similar to)65%, was observed. Interacting the monospheres with MnO4- (0-50 mu M) effectively quenched the luminescence via Ce3+ oxidation, and treating the luminescence-quenched monospheres with VC (0-250 mu M) sufficiently recovered the luminescence via Ce4+ reduction. Numerical expressions were also established to correlate the emission intensity with VC and MnO4- concentrations. Besides, the colloidal monospheres exhibited the favorable response time of (similar to)18 and 50 s for 25 mu M of MnO4- and 150 mu M of VC, respectively.