This is about one-fourth of the forest conversion emission factor in this AEZ.
Zheng et al. observed five-photon up-conversion emissions of Er3+ for optical temperature sensing which had highest sensitivity was 0.0052 K−1 [17].
The electrochemical impedance spectroscopy (EIS) was obtained with an electrochemical workstation (CHI660e, Shanghai CHI Co., Ltd .. Up-conversion emissions were measured with an excitation of a 980-nm laser.
The two green up-conversion emissions bands at about 529 and 542 nm correspond to the 2H11/2→4I15/2 and 4S3/2→4I15/2 transitions of Er3+, respectively.
Under 980 nm laser excitation, the green and red up-conversion emissions are observed at around 549 and 661 nm, which are attributed to the transitions of 4S3/2 → 4I15/2 and 4F9/2 → 4I15/2 of Er3+ ions, respectively.
When they compared spectra of Y2O3 Eu3+ with Yb3+, they noted that the up-conversion and down-conversion emissions lost intensity in the presence of Yb3+ and that was least apparent for the red 4F9/2 → 4I15/2 transition, even for a Yb3+/Er3+ ratio of 5 0.5.
Pumped by nanosecond laser at 800 nm, strong up-conversion emissions with the central wavelength at 507 nm (green) of 2,5-bis[4- 2-N,N-diphenylaminostyryl phenyl]-1,3,4-oxadiazole and 475 nm (blue) of 2,5-bis[4- 2-N,N-diphenylaminostyryl phenyl]-1,3,4-oxadiazoleole in the solution of CHCl3 have been observed.
Blue up-conversion emission occurs by its radiative de-excitations to the 4I15/2 level.
The UC-TiO2 presented an enhanced up-conversion emission compared with Er3+-Yb3+ co-doped TiO2.
The reduced state (Ce3+) associated to oxygen vacancies form defect states that are responsible for the down-conversion emission.
For measurements of up-conversion emission intensity dependence on excitation power, a continuous-wave laser is used (980-nm radiation).
