scholarly journals Nd3+-Doped TiO2 Nanoparticles as Nanothermometer: High Sensitivity in Temperature Evaluation inside Biological Windows

Sensors ◽  
2021 ◽  
Vol 21 (16) ◽  
pp. 5306
Author(s):  
Selene Acosta ◽  
Luis J. Borrero-González ◽  
Polona Umek ◽  
Luiz A. O. Nunes ◽  
Peter Guttmann ◽  
...  

TiO2 nanoparticles doped with different amounts of Nd3+ (0.5, 1, and 3 wt.%) were synthetized by the sol–gel method, and evaluated as potential temperature nanoprobes using the fluorescence intensity ratio between thermal-sensitive radiative transitions of the Nd3+. XRD characterization identified the anatase phase in all the doped samples. The morphology of the nanoparticles was observed with SEM, TEM and HRTEM microscopies. The relative amount of Nd3+ in TiO2 was obtained by EDXS, and the oxidation state of titanium and neodymium was investigated via XPS and NEXAFS, respectively. Nd3+ was present in all the samples, unlike titanium, where besides Ti4+, a significantly amount of Ti3+ was observed; the relative concentration of Ti3+ increased as the amount of Nd3+ in the TiO2 nanoparticles increased. The photoluminescence of the synthetized nanoparticles was investigated, with excitation wavelengths of 350, 514 and 600 nm. The emission intensity of the broad band that was associated with the presence of defects in the TiO2, increased when the concentration of Nd3+ was increased. Using 600 nm for excitation, the 4F7/2→4I9/2, 4F5/2→4I9/2 and 4F3/2→4I9/2 transitions of Nd3+ ions, centered at 760 nm, 821 nm, and 880 nm, respectively, were observed. Finally, the effect of temperature in the photoluminescence intensity of the synthetized nanoparticles was investigated, with an excitation wavelength of 600 nm. The spectra were collected in the 288–348 K range. For increasing temperatures, the emission intensity of the 4F7/2→4I9/2 and 4F5/2→4I9/2 transitions increased significantly, in contrast to the 4F3/2→4I9/2 transition, in which the intensity emission decreased. The fluorescence intensity ratio between the transitions I821I880=F5/24I49/2F43/2I49/2 and I760I880=F47/2I49/2F43/2I49/2 were used to calculate the relative sensitivity of the sensors. The relative sensitivity was near 3% K−1 for I760I880 and near 1% K−1 for I821I880.

Sensors ◽  
2019 ◽  
Vol 19 (10) ◽  
pp. 2400 ◽  
Author(s):  
Wanjun Sheng ◽  
Xiangfu Wang ◽  
Yong Tao ◽  
Xiaohong Yan

We report a new method for detecting variable resistance during short time intervals by using an optical method. A novel variable-resistance sensor composed of up-conversion nanoparticles (NaYF4:Yb3+,Er3+) and reduced graphene oxide (RGO) is designed based on characteristics of a negative temperature coefficient (NTC) resistive element. The fluorescence intensity ratio (FIR) technology based on green and red emissions is used to detect variable resistance. Combining the Boltzmann distributing law with Steinhart–Hart equation, the FIR and relative sensitivity SR as a function of resistance can be defined. The maximum value of SR is 1.039 × 10−3/Ω. This work reports a new method for measuring variable resistance based on the experimental data from fluorescence spectrum.


2021 ◽  
Author(s):  
Meiling Shi ◽  
Leqi Yao ◽  
shijie Yu ◽  
Yan Dong ◽  
Qiyue Shao

The fluorescence intensity ratio (FIR) technique is widely adopted in thermometric phosphor materials, but the improvement of relative sensitivity is normally limited by the fixed energy gap between two thermally-couped...


2018 ◽  
Vol 43 (2) ◽  
pp. 186 ◽  
Author(s):  
Leipeng Li ◽  
Yuan Zhou ◽  
Feng Qin ◽  
Yangdong Zheng ◽  
Hua Zhao ◽  
...  

2017 ◽  
Vol 42 (23) ◽  
pp. 4837 ◽  
Author(s):  
Leipeng Li ◽  
Yuan Zhou ◽  
Feng Qin ◽  
Yangdong Zheng ◽  
Hua Zhao ◽  
...  

2000 ◽  
Vol 39 (18) ◽  
pp. 3050 ◽  
Author(s):  
Scott A. Wade ◽  
Stephen F. Collins ◽  
Kenneth T. V. Grattan ◽  
Gregory W. Baxter

2014 ◽  
Vol 16 (41) ◽  
pp. 22665-22676 ◽  
Author(s):  
B. P. Singh ◽  
A. K. Parchur ◽  
R. S. Ningthoujam ◽  
P. V. Ramakrishna ◽  
S. Singh ◽  
...  

Graphical representation of Li+ co-doped Y2Ti2O7:Er3+/Yb3+ phosphor showing up-conversion of green and red bands and probing the fluorescence intensity ratio (FIR) for temperature sensing applications.


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