Effect of Yb³⁺ concentration on the spectroscopic properties of Er³⁺/Yb³⁺ co-doped SiO₂-TiO₂ nanofiber

Er3+ has been gaining much interest due to the multiple emissions in both infrared and visible regions. Based on the previous study, SiO2-TiO2 have been proven to be an excellent host for Er3+. However, Er3+ exhibits a low absorption cross-section when doped into the silica-based host. Therefore, Yb3+ has been introduced into the matrix and acts as a sensitiser to increase the luminescence intensity. Er3+/Yb3+ co-doped 75SiO(2)-25TiO(2) nanofiber with different Er3+/Yb3+ ratios were fabricated via the sol-gel electrospinning method. The FESEM result shows the diameter of the nanofibers in the range of 62 to 515 nm. The absence of any peak within the 3000-4000 cm(-1) range in the FTIR spectra indicates the complete removal of the OH group. The XRD results imply that all samples were amorphous. The PL spectra showed strong green emission peaks, which were ascribed to H-2(11/2) -> I-4(15/2) as well as red emission peaks attributed to F-4(9/2) -> I-4(15/2) Er3+ transitions. The PL intensity was varied according to the Yb3+ concentration. The addition of Yb3+ was proven to aid the increment of PL intensity. Nevertheless, the PL intensity reduced when too high of Yb3+ concentration was used due to the concentration quenching effect.