Figure 4.

Variations in the emission intensity ratios (I520/I585) of the co-doped silica particles. Recoded at the start pH (pH = 4) and end pH (pH = 8) of different cycles. The excitation wavelength was at 450 nm.

Xu et al. Nanoscale Research Letters 2011 6:561   doi:10.1186/1556-276X-6-561
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