Nonlinear Optical Thermometry—A Novel Temperature Sensing Strategy via Second Harmonic Generation (SHG) and Upconversion Luminescence in BaTiO₃:Ho³⁺,Yb³⁺ Perovskite

Abstract

Nonlinear optical spectroscopy may be a powerful tool for sensing of various intrinsic properties of materials and different state functions of the system. This is due to the strong dependence of nonlinear phenomena on numerous physicochemical factors. The feasibility of simultaneously employing the second harmonic generation (SHG) and upconversion luminescence (UCL) processes in BaTiO3:Ho3+,Yb3+ for optical temperature sensing is demonstrated for the first time. Under 976 nm laser excitation, the evolution of the SHG and UCL band intensity ratio is correlated with temperature and calibrated within the temperature range of 25–305 °C. The band intensity ratio between SHG and UCL exhibits a sigmoidal dependence on temperature, and, hence, it can allow the detection of phase transitions from non‐centrosymmetric to centrosymmetric systems, and vice versa. Most importantly, from the perspective of optical temperature sensing, this work provides a novel and effective strategy for nonlinear optical thermometry, with high sensitivity of up to 2.78% °C–1.

Manipulating Upconversion Emission and Thermochromic Properties of Ho3+/Yb3+-Codoped Al2Mo3O12 Microparticles by Negative Lattice Expansion for Multimode Visual Optical Thermometry

“…As one of the rare-earth ions, Ho 3+ is considered an important upconverting activator, since it can emit strong green and red UC emissions. 32,33 Besides, to enhance the UC emission of Ho 3+ , Yb 3+ is needed to be codoped, since it is able to absorb near-infrared (i.e., NIR) efficiently and shift the captured energy to Ho 3+ . 34,35 Clearly, the influence of NTE on the UC emission and temperature In addition, based on the temperature-dependent color coordinates, we further investigated the thermometric behaviors of the resultant microparticles.…”

“…For the aim of shedding light on the luminescence behaviors of the studied samples, we recorded the UC emission spectra of Al 2 Mo 3 O 12 :Ho 3+ /2 x Yb 3+ microparticles, which are depicted in Figure a. Excited by NIR light (i.e., 980 nm), all of the compounds exhibit the UC emissions of Ho 3+ , with emission bands with central wavelengths of 545, 661, and 760 nm deriving from the 5 F 4 / 5 S 2 → 5 I 8 , 5 F 5 → 5 I 8 , and 5 F 4 / 5 S 2 → 5 I 7 transitions of Ho 3+ , , respectively. Moreover, it is evident that the intensities of the detected UC emissions are able to be modified by tuning the Yb 3+ content, reaching their maximum values when x = 0.09 (see Figure b).…”

“…Thus, the investigation on the synthesis and luminescence properties of rare-earth ion-doped Al 2 Mo 3 O 12 materials is very necessary. As one of the rare-earth ions, Ho 3+ is considered an important upconverting activator, since it can emit strong green and red UC emissions. , Besides, to enhance the UC emission of Ho 3+ , Yb 3+ is needed to be codoped, since it is able to absorb near-infrared (i.e., NIR) efficiently and shift the captured energy to Ho 3+ . , Clearly, the influence of NTE on the UC emission and temperature sensing characterization of Ho 3+ /Yb 3+ -codoped Al 2 Mo 3 O 12 compounds has never been investigated yet. For the sake of making up this shortage, we utilized the high-temperature solid-state reaction method to synthesize Ho 3+ /Yb 3+ -codoped Al 2 Mo 3 O 12 microparticles, in which their basic features including phase component, microstructure, surface behavior, light harvest capacity, UC emission properties, and thermal quenching performance have been investigated in detail.…”

Supersensitive Ratiometric Thermometry and Manometry Based on Dual‐Emitting Centers in Eu2+/Sm2+‐Doped Strontium Tetraborate Phosphors

“…Due to the absence of an appropriate physical model to conform the changes of LIR of the non-TCLs within the studied range of temperature, the empirical, i.e., exponential or polynomial functions are commonly employed. [14,15,[37][38][39] In the case of the compounds containing 1 and 3 mol% of Eu 2+ , the use of bi-exponential functions resulted in satisfactory fitting, however, in the case of the highly doped compound, with 9 mol% of Eu 2+ , the use of different 3rd-order polynomial function was necessary to obtain good fitting. This is probably due to the higher doping content, leading to various, temperature-dependent concentration quenching effects, compared to other samples.…”

Solution‐Based Synthesis Routes for the Preparation of Noncentrosymmetric 0‐D Oxide Nanocrystals with Perovskite and Nonperovskite Structures

“…The above kinetic aspects and growth mechanisms, when reported in the literature, are indicated in the next sections of this review only dedicated to 0-D dielectric nanomaterials and whose global outline is largely inspired from the excellent contributions of Charles et al [56] and Schnepp et al [57] Very notably, the overall complexity of NCO nanocrystals has recently been increased in terms of chemical compositions with the synthesis of three-and four-cation perovskites belonging to high-symmetry point groups, [8,58] in terms of new functional optical properties with the doping by fluorescent rare-earth ions, [59][60][61] in terms of crystalline structures with new hosts belonging to low-symmetry point groups [62,63] and finally, in terms of surface functionalization for bioimaging [64,65] and for the two-photon-triggered photorelease of caged compounds in advanced drug-delivery theranostic applications. [66,67] In parallel, the experimental techniques (TEM imaging, synchrotron radiations, pair distribution function analysis of the Bragg and diffuse scattering components, SAXS, real-time UV-Vis, FTIR, DLS, SHG, and AFM-based experiments, etc.)…”