Lanthanide-based luminescent hybrid materials.

Uniform, spherical-shaped TiO2:Eu nanoparticles with different doping concentrations have been synthesized through controlled hydrolysis of titanium tetrabutoxide under appropriate pH and temperature in the presence of EuCl3·6H2O. Through air annealing at 500°C for 2 h, the amorphous, as-grown nanoparticles could be converted to a pure anatase phase. The morphology, structural, and optical properties of the annealed nanostructures were studied using X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy [EDS], and UV-Visible diffuse reflectance spectroscopy techniques. Optoelectronic behaviors of the nanostructures were studied using micro-Raman and photoluminescence [PL] spectroscopies at room temperature. EDS results confirmed a systematic increase of Eu content in the as-prepared samples with the increase of nominal europium content in the reaction solution. With the increasing dopant concentration, crystallinity and crystallite size of the titania particles decreased gradually. Incorporation of europium in the titania particles induced a structural deformation and a blueshift of their absorption edge. While the room-temperature PL emission of the as-grown samples is dominated by the 5D0 - 7Fj transition of Eu+3 ions, the emission intensity reduced drastically after thermal annealing due to outwards segregation of dopant ions.

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Effects of crystallization and dopant concentration on the emission behavior of TiO2:Eu nanophosphors

Sasidharan Swarnalatha Lucky,†,§ Khee Chee Soo,‡ and Yong Zhang*,†,§,∥ †NUS Graduate School for Integrative Sciences & Engineering (NGS), National University of Singapore, Singapore, Singapore 117456 ‡Division of Medical Sciences, National Cancer Centre Singapore, Singapore, Singapore 169610 Department of Biomedical Engineering, Faculty of Engineering, National University of Singapore, Singapore, Singapore 117576 College of Chemistry and Life Sciences, Zhejiang Normal University, Zhejiang, P. R. China 321004

Nanoparticles in photodynamic therapy.

Yuming Yang,†,§ Qiang Zhao,‡,§ Wei Feng,† and Fuyou Li*,† †Department of Chemistry and State Key Laboratory of Molecular Engineering of Polymers and Institutes of Biomedical Sciences, Fudan University, Shanghai 200433, P. R. China ‡Key Laboratory for Organic Electronics and Information Displays (KLOEID) and Institute of Advanced Materials (IAM), Nanjing University of Posts and Telecommunications, Nanjing 210046, P. R. China.

Luminescent chemodosimeters for bioimaging.

Applications in Theranostics Guanying Chen,*,†,‡ Hailong Qiu,†,‡ Paras N. Prasad,*,‡,§ and Xiaoyuan Chen* †School of Chemical Engineering and Technology, Harbin Institute of Technology, Harbin, Heilongjiang 150001, China ‡Department of Chemistry and the Institute for Lasers, Photonics, and Biophotonics, University at Buffalo, State University of New York, Buffalo, New York 14260, United States Department of Chemistry, Korea University, Seoul 136-701, Korea Laboratory of Molecular Imaging and Nanomedicine, National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bethesda, Maryland 20892-2281, United States

Upconversion Nanoparticles: Design, Nanochemistry, and Applications in Theranostics

The energy levels and local structures of Eu 3+ incorporated in the lattice and surface sites of ZnO nanocrystals were investigated based on the high-resolution fluorescence spectra at 10 K. Radiative emissions from 5 D1 were first observed for Eu 3+ at the lattice site of ZnO. It is shown that the site symmetry of Eu 3+ at the lattice site descends from C3V to Cs or C1, whereas Eu 3+ ions at the surface occupy more disordered sites of the lowest symmetry C1. The luminescence decay of 5 D0 at the lattice site, showing a rise time and longer lifetime, behaves distinctly from that of the surface sites. Because of a small filling factor (52%) of nanoparticles, the 5 D0 lifetime of Eu 3+ is significantly affected by the surrounding medium, which can be well interpreted with the virtual-cavity model. The Judd-Ofelt intensity parameters of Eu 3+ in ZnO nanocrystals were determined, with ?2,4,6 values of (9.59, 8.11, <0.25) and (21.51, 2.30, <0.25) in units of 10 -20 cm 2 for Eu 3+ at the surface and lattice sites, respectively. A defect-mediated energy transfer from the ZnO band gap to Eu 3+ was observed. The growth mechanism for the incorporation of Eu 3+ into the ZnO lattice was also revealed.

Optical Spectroscopy of Eu 3+ Doped ZnO Nanocrystals

Tailoring the Broadband Emission in All-Inorganic Lead-Free 0D In-Based Halides through Sb3+ Doping

Phosphor materials have been rapidly developed in the past decades. Developing phosphors with desired properties including strong luminescence intensity and long lifetime has attracted widespread attention. Herein, we show that hetero-valence ion doping can serve as a potent strategy to manipulate luminescence in persistent phosphors by controlling disorder in the host lattice. Specifically, spinel phosphor Zn(Ga1− x Zn x )(Ga1− x Ge x )O4:Cr is developed by doping ZnGa2O4:Cr with tetravalent Ge4+. Compared to the original ZnGa2O4:Cr, the doped Zn(Ga1− x Zn x )(Ga1− x Ge x )O4:Cr possesses significantly enhanced persistent luminescence intensity and prolonged decay time. Rietveld refinements show that Ge4+ enters into octahedral sites to substitute Ga3+, which leads to the co-substitution of Ga3+ by Zn2+ for charge compensation. The hetero-valence substitution of Ga3+ by Ge4+ and Zn2+ enriches the charged defects in Zn(Ga1− x Zn x )(Ga1− x Ge x )O4:Cr, making it possible to trap large amounts of charge carriers within the defects during excitation. Electron paramagnetic resonance measurement further confirms that the amount of Cr3+ neighboring charged defects increases with Ge4+ doping. Thus charge carriers released from defects can readily combine with the neighboring Cr3+ to produce bright persistent luminescence after excitation ceases. The hetero-valence ion doping strategy can further be employed to develop many other phosphors and contributes to lighting, photocatalysis and bioimaging.

Controlling disorder in host lattice by hetero-valence ion doping to manipulate luminescence in spinel solid solution phosphors

Optical thermal sensing holds great promise for disease theranostics. However, traditional ratiometric thermometry methods, in which intensity ratio of two nonoverlapping emissions is defined as the thermosensitive parameter, may have a limited accuracy in temperature read-out due to the deleterious interference from wavelength- and temperature-dependent photon attenuation in tissue. To overcome this limitation, a dual-excitation decoding strategy based on NIR hybrid nanocomposites comprising self-assembled quantum dots (QDs) and Nd3+ doped fluoride nanocrystals (NCs) is proposed for thermal sensing. Upon excitation at 808 nm, the intensity ratio of two emissions at identical wavelength (1057 nm) from QDs and NCs, respectively, is defined as the thermometric parameter R. By employing another 830 nm laser beam following the same optical path as 808 nm laser to exclusively excite QDs, the two overlapping emissions can be easily decoded. The acquired R proves to be inert to the detection depth in tissue, with a minimized temperature reading error of ≈2.3 °C at 35 °C (at a depth of ≈1.1 mm), while the traditional thermometry mode based on the nonoverlapping 1025 and 863 nm emissions may exhibit a large error of ≈43.0 °C. The insights provided by this work pave the way toward high-accuracy deep-tissue biosensing.

https://onlinelibrary.wiley.com/doi/pdf/10.1002/advs.202001589

A Dual-Excitation Decoding Strategy Based on NIR Hybrid Nanocomposites for High-Accuracy Thermal Sensing.

Currently, lanthanide (Ln3+)-doped near-infrared (NIR)-emitting double perovskites (DPs) suffer from low photoluminescence quantum yield (PLQY). Herein, we develop a new class of NIR-emitting DPs based on Ln3+-doped Cs2(Na/Ag)BiCl6. Benefiting from the Na+-induced breakdown of local site symmetry in the Cs2AgBiCl6 DPs, effective NIR emissions of Ln3+ are realized through Bi3+ sensitization. Specifically, 7.3-fold and 362.9-fold enhanced NIR emissions of Yb3+ and Er3+ are achieved in Cs2Ag0.2Na0.8BiCl6 DPs relative to those in Na-free Cs2AgBiCl6 counterparts, respectively. The optimal absolute NIR PLQYs for Yb3+ and Er3+ in Cs2Ag0.2Na0.8BiCl6 DPs are determined to be 19.0% and 4.3%, respectively. Raman spectroscopy and first-principles density functional theory calculations verify the sublattice distortion in Cs2(Na/Ag)BiCl6 DPs via Na+ doping. These findings provide fundamental insights into the design of efficient NIR-emitting Ln3+-doped DPs for versatile optoelectronic applications.

Xueyuan Chen

Papers

Optical Spectroscopy of Eu 3+ Doped ZnO Nanocrystals

Tailoring the Broadband Emission in All-Inorganic Lead-Free 0D In-Based Halides through Sb3+ Doping

Controlling disorder in host lattice by hetero-valence ion doping to manipulate luminescence in spinel solid solution phosphors

A Dual-Excitation Decoding Strategy Based on NIR Hybrid Nanocomposites for High-Accuracy Thermal Sensing.

Boosting Near-Infrared Luminescence of Lanthanide in Cs2AgBiCl6 Double Perovskites via Breakdown of the Local Site Symmetry.