Highly efficient NIR to NIR upconversion of ZnMoO₄:Tm³⁺,Yb³⁺ phosphors and their application in biological imaging of deep tumors

Abstract

In vivo imaging of deep tumor in nude-mice was successfully demonstrated using highly efficient ZnMoO4:Tm3+,Yb3+,K+ nano-phosphors and an 810 nm NIR laser.

Super Broadband-Sensitive Upconversion in Tm and Ni Codoped Perovskites

“…These Ni 2+ absorption bands are partially overlapped with the Tm 3+ absorption peaks making the absorption peaks more intense and broad in the Tm and Ni codoped samples and thus cover a broader solar radiation ranging from 900 to 2000 nm. The energy level diagram consisting of Tm 3+ and Ni 2+ band positions in the CaTi 0.9 O 3 host calculated from the absorption spectra and possible energy transfer pathways is presented in Figure 1( [11,14]. Very similar UC emissions were also observed for the Tm and Ni codoped sample while excited at 960, 1300, and 1400 nm (only 960 nm excited UC emission spectrum is shown here, and very similar spectra were observed for all the excitation wavelengths mentioned above) that corresponded to the Ni absorption only (see Figure 1(a)) because no Tm 3+ absorption bands were located between 850-1100 nm and 1300-1500 nm ranges.…”

“…Considering the short circuit current density of~30 mA/cm 2 and conversion efficiency of~29% for a present single-junction GaAs solar cell, an improvement in conversion efficiency of~13% (absolute) is possible [27]. Further, the NIR emission at 800 nm perfectly matches the transparency window 7 International Journal of Photoenergy (650-1450 nm) of animal tissues, making the upconverter as a potential candidate for biological imaging besides energy conversion and storage [11]. However, at present, the absorptivity of the developed material is weak, and it should be addressed to utilize super broadband solar radiations efficiently.…”

“…Thus, the newly designed Tm 3+ -and Ni 2+ -based upconverters can be used to enhance the efficiency of GaAs, Cu 2 ZnSnS 4 , a-Si, and some special dye-sensitized solar cells that have absorption edges extended to 800 nm and longer. Besides, such NIR-to-NIR upconverters have potential applications in biomedical imaging and therapies of tumors owing to their biocompatibility, and minimal heating effects as compared to the traditional imaging techniques [11].…”

Controllable Synthesis of Upconversion Nanophosphors toward Scale‐Up Productions

“…Even though the relationship between optical performance and morphology of UCNPs have had been well understood, [ 23–26 ] relevant developments on commercializing such nanomaterials are hampered due to scaling‐up production process, where bottlenecks normally exist in the reproducibility, repeatability as well as the yield from these methods. By recapping these reported synthesis methods, for example, thermal decomposition, [ 35–40 ] co‐precipitation, [ 60–66 ] hydrothermal, [ 73–78 ] and ion exchange, [ 98–101 ] a common characteristics is discovered that these processes require large amounts of solvents, which easily lead to nonuniform precursor concentrations and temperature distributions. This characteristic represents an essential challenge in managing thermodynamic equilibrium for a smooth and uniform synthesis in lab, [ 27,28 ] and the scale‐up process where the breaking of local thermodynamic equilibrium is likely to occur to yield the uncontrollable changes on the phases and other features for the particle, especially the luminescent performance.…”

CaTiO3:Er3+,Ni2+broadband‐sensitive upconverter: An effective way to harvest unused NIR solar irradiation for crystalline silicon solar cells

“…Photon upconversion (UC) involves the absorption of two or more photons of low energies with subsequent emission of a single higher energy photon. Rare‐earth‐doped UC materials with strong luminescence in the NIR to the visible region have been extensively investigated in recent years due to their several potential applications in solar cells , novel display technologies , inks for secure printing , optical communication and amplifier , high density optical storage , infrared detection and sensors , and many more. From the various applications mentioned above, efficiency improvement of solar cells is one of the hot topics at present to exceed the limiting conversion efficiency of a single‐junction solar cell, namely, the Shockley–Quisser (S–Q) limit .…”