Development of Multi-Parameter Measurement Apparatus for Up-Conversion Phosphor Particles

Up-conversion phosphor (UCP) particles have been used as optical biomarkers in a variety of assay formats. UCP particle properties such as concentration and luminescence are critical for these applications. A multi-parameter measurement apparatus (MPMA) has been designed and constructed to quantify UCP-particle concentration through the scattered light (S), and luminescence properties through fluorescence light (F), respectively. Linearity of S and F can be improved by introducing the transmitted light T over a wide range of concentrations. 38 suspensions at 0.001-2.0 mg/mL have been used to assess the utility of this apparatus for the accumulation of UCP information. The MPMA achieved a detection limit of 0.001 mg/mL and a dynamic range that reached 1.4 mg/mL according to S/T and 2.0 mg/mL according to F/T. The coefficient of variation for ten consecutive tests of the same sample is less than 14% while the measurement error for UCP particle concentration is below 18%. This lower limit of detection, repeatability and accuracy indicate that it is a valuable apparatus for monitoring and controlling the performances of UCP particles during UCP synthesizing as well as surface modification and activation processes.