Brilliant Nonlinear Optical Response of Ho³⁺ and Yb³⁺ Activated YVO₄ Nanophosphor and Its Conjugation with Fe₃O₄ for Smart Anticounterfeit and Hyperthermia Applications

Abstract

YVO4:Ho3+/Yb3+ nanophosphors prepared by an effective polyol-mediated route show dual-mode behavior in photoluminescence. Upon 980 nm excitation, the upconversion red emission spectrum exhibits a bright red peak at ∼650 nm, characteristic of the electronic transition of the Ho3+ ion via involvement of two-photon absorption, which has been confirmed by the power-dependent luminescence study. Moreover, at 300 nm excitation, downconversion emission peaks are observed at 550, 650, and ∼755 nm. The nonradiative resonant energy transfer occurs from the V–O charge transfer band to Ho3+ ions, resulting in an improved emission of Ho3+ ions. Moreover, polyethylene glycol-coated nanoparticles make it suitable for water dispersibility; and these particles are conjugated with Fe3O4 nanoparticles to form magnetic–luminescent hybrid nanoparticles. Highly water-dispersible magnetic–luminescent hybrid material attained the hyperthermia temperature (∼42 °C) under an applied AC magnetic field. The specific absorption rate value is found to be high (138 W/g), which is more than that of pure superparamagnetic Fe3O4 nanoparticles. At 300 nm excitation, the high quantum yield value of ∼27% is obtained from YVO4:Ho3+/Yb3+, which suggests that it is a good phosphor material. By employing the neutron activation analysis technique, it is shown that nanophosphor particles can absorb Au3+ up to the ppm level. Interestingly, such nanophosphor also shows the potentiality for anticounterfeiting applications.

Mesoporous NaGdF4/Ho–Yb@m-SiO2 Upconversion Nanophosphors as a Potent Theranostic Probe

“…The upconversion spectrum exhibits three strong emission peaks at ∼540, 645, and ∼750 nm, which are attributed to the electronic 4f−4f transitions 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 of Ho 3+ , respectively. 17,18 It is observed that the intensity of green band emission (545 nm) is brighter than that of red band emission (645 nm) at all laser input powers. It is found that the intensity increases with the increase of laser power.…”

“…There is a sharp peak at 463 nm, which corresponds to the absorption peak of Ho 3+ . 17,18 It is to be noted that the band gap of NaYF 4 or NaGdF 4 is about 10 eV (∼123 nm). 23 It means that host UCNPs will be transparent above 200 nm.…”

“…While DOX-loaded UCNPs would have potential applications in cancer therapy as a chemotherapeutic formulation, [ 177 Lu]­Lu–NaGdF 4 /Ho–Yb@m-SiO 2 would be useful in nuclear medicine as a theranostic probe because suitable decay properties of 177 Lu are useful in SPECT imaging as well as therapy. Lutetium-177 is one of the most important radioisotopes extensively used in nuclear medicine for the management of cancer treatment. − In addition, β – emission (497 keV) with a maximum penetration tissue range of ∼2.5 mm from 177 Lu is useful for imaging, and concomitant emission of gamma photons of suitable energies (113 and 208 keV) enables simultaneous molecular imaging through SPECT. Figure shows the schematic diagram demonstrating the potential material of NaGdF 4 /Ho–Yb@m-SiO 2 UCNPs for multifunctional theranostic applications.…”

Generation of Pure Green Up-Conversion Luminescence in Er3+ Doped and Yb3+-Er3+ Co-Doped YVO4 Nanomaterials under 785 and 975 nm Excitation

“…In the case of generation of the UC emission, the most frequently used dopant ions are the following systems: Yb 3+ -Er 3+ , Yb 3+ -Tm 3+ and Yb 3+ -Ho 3+ , [45][46][47][48]; however, triple or even four-fold doped systems are also known, such as Yb 3+ -Ho 3+ -Nd 3+ and Yb 3+ -Tm 3+ -Ho 3+ -Er 3+ [49,50]. One of the most commonly studied materials is YVO 4 doped with Yb 3+ -Er 3+ .…”

Altering of the Electric and Magnetic Dipole Transition Probability of Eu3+ in YPO4 Lattice by Codoping of K+ Ion: Potential Materials for Imaging and Heating

“…Rare-earth doped nanoparticles have been used in many applications including display, light emitting, sensor, and bioimaging, etc. − Particularly, rare-earth doped phosphates (REPO 4 ) have advantages over other available luminescent materials such as organic dyes and PbSe quantum dots in terms of photostability, biocompatibility, and easy surface functionalization. − Eu 3+ doped REPO 4 nanoparticles have been used extensively since the Eu 3+ ion has the 4f–4f transitions in absorption and emission spectra with characteristics of the electric dipole and magnetic dipole transitions. A maximum absorption peak at 395 nm ( 7 F 0 – 5 L 6 transition) and emission peaks at 580, 592, 615, 645, and 695 nm are observed. − In many cases, a transition due to 580 nm is not observed due to its forbidden nature ( 5 D 0 – 7 F 0 transition).…”