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The positron emission particle tracking (PEPT) technique has been widely used in science and engineering to obtain detailed information on particulate motion in granular materials and flow fields in multiphase systems. The technique involves tracking a single radioactively labelled particle by detecting the pairs of back-to-back 511keV γ-rays arising from annihilation of emitted positrons. It is thus crucially dependent on the availability of suitably labelled tracer particles. With the present equipment, the optimum activity for a PEPT tracer is between 300 and 1000μCi. The positron emitting radionuclide most often used is ¹⁸F in the form of fluoride ions. However, most materials have a very poor capacity to take up fluoride naturally. This paper presents a surface modification technique which was developed to improve the adsorption of ¹⁸F on solids and therefore extending the application of PEPT. For example, 200μm …