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

Nonlinear multi-phonon (2-7) absorption in the Na+/Bi3+-alloyed Cs2AgInCl6 lead-free double perovskites with ∼100% photoluminescence quantum yield and superior stability is observed for the first time, which can be pumped by a femtosecond laser in a wide spectral range (800-2600 nm). First-principles calculations verify that the parity-forbidden transition from the valence band maximum and conduction band minimum (at the Γ point) is not broken by Na+/Bi3+ doping, and strong optical band-to-band absorption occurs at the L&X points. Time-resolved emission spectra evidence that single-photon and multi-photon pumping leads to the same self-trapped exciton transition and high-order nonlinear absorption will not induce a remarkable thermal effect. Finally, we demonstrate that the Cs2Na0.4Ag0.6In0.99Bi0.01Cl6 DP shows great potential for next-generation wavelength-selective and highly sensitive multiphoton imaging applications.

Seven-photon absorption from Na+/Bi3+-alloyed Cs2AgInCl6 perovskites.

The physical properties of the host materials with nanometer dimensions may differ markedly from those of their bulk counterparts due to the particle size-dependent influences such as structure disordering and surface defects. Understanding the spectroscopic properties of these materials is important for optimizing their emissive properties for technological applications. In lanthanide-doped nanoparticles, particle size may affect luminescence quantum efficiency, radiative lifetime, nonradiative relaxation, as well as excitation energy transfer processes. Many of these observed phenomena result from size-reduction-induced structure distortion and surface defects that affect the local environments surrounding the doped lanthanide ions. In this chapter, the recent progress in the size effect on the luminescence of lanthanide ions in NPs was briefly reviewed, which covers from the basic theoretical principles for size-dependent luminescence dynamics to electronic energy-level fitting.

Size Effect on the Luminescence of Lanthanide Ions in Nanoparticles

National Natural Science Foundation of China[20725310, 21021061, 21073145]; Key Scientific Project of Fujian Province of China[2009HZ0002-1]; National Basic Research Program of China[2007CB815303, 2011CBA00508]; China Postdoctoral Science Foundation[20080430786]

Low cytotoxicity porous Nd(2)(SiO(4))(3) nanoparticles with near infrared excitation and emission.

Lanthanide-doped luminescent inorganic nanoparticles (NPs) of various compositions, albeit most of their bulk counterparts have been well studied previously, have attracted reviving interest and come to the forefront in nanophotonics owing to their potential applications in diverse fields such as biodetection and bioimaging. These lanthanide-doped NPs show superior features including narrow emission bandwidths, long photoluminescence (PL) lifetime, low toxicity, and high resistance to photobleaching, making them highly suitable for use as alternatives to organic fluorescent dyes or quantum dots for various bioapplications such as early cancer theranostics. In this chapter, the most recent progress in the optical spectroscopy of lanthanide-doped NPs is discussed. Particularly, we would like to provide an in-depth overview of the optical properties for lanthanide-doped semiconductor and insulator NPs, with an emphasis on the host-sensitized long-lived downconversion luminescence of Ln3+ exemplified by Eu3+ and Tb3+ and the multicolor upconversion luminescence originating from Er3+, Tm3+, Ho3+, and Yb3+ ions co-doped NPs. Furthermore, the use of Ln3+ ions as a sensitive structural probe to analyze the local structure of dopants will also be highlighted in this chapter, which is crucial to optimizing their optical performance for further biological applications.

Optical Spectroscopy of Lanthanide-Doped Nanoparticles

ConspectusTremendous progress in nanomaterial and nanotechnology has been made in recent years, which greatly contributes to the development of inorganic nanoparticles (NPs) as luminescent probes in diverse biomedical applications. In particular, these luminescent nanoprobes are widely employed for sensitive assays of biomarkers like disease markers. Generally, the luminescent bioassay technologies mainly rely on conventional molecular probes such as lanthanide (Ln3+) chelates or organic dyes, which suffer from inferior photochemical stability, low photobleaching, potential long-term toxicity, or high background noise. In contrast, Ln3+-doped NPs possess distinct physicochemical properties including better photostability, lower toxicity, and superior optical properties like long photoluminescent (PL) lifetime, narrow emission band, and tunable spectral range from the ultraviolet to the second near-infrared (NIR-II), which make them extremely ideal as luminescent nanoprobes. As such, enormous research enthusiasm has been invested in this fascinating field of Ln3+-doped luminescent nanoprobes in recent years. Accordingly, background-free luminescent bioassays with high signal-to-noise have been achieved by employing Ln3+-doped NPs on the basis of their downshifting luminescence (DSL) with a long PL lifetime, NIR-II luminescence with long-wavelength emissions, or upconverting luminescence (UCL) upon NIR excitation. However, there are still key challenges for Ln3+-doped nanoprobes owing to their low brightness and quantum yield, which restrict their biomedical applications. During the past decade, we have explored efficient approaches for the synthesis and design of highly efficient Ln3+-doped nanoprobes toward ultrasensitive luminescent bioassay of disease markers.In this Account, we summarize our most recent endeavors toward the development of inorganic Ln3+-doped NPs as sensitive nanoprobes for luminescent bioassays. First, we overview the approaches of controlled synthesis and optical manipulation to obtain highly efficient Ln3+-doped NPs with desirable optical properties. Second, we survey the design of Ln3+-doped nanoprobes with outstanding water dispersibility and excellent biocompatibility through surface functional bioconjugation of NPs. By employing these nanoprobes, we propose and exemplify several background-free luminescent bioassay strategies in an effort to suppress the interference of background noise from scattered lights and autofluorescence from biological samples. Third, we highlight the ultrasensitive bioassay of disease markers such as the time-resolved luminescent bioassay, NIR-II luminescent bioassay, and UCL bioassay. Finally, the major challenges, promising emerging trends, and future perspectives on this attractive field are discussed. Through this Account, we aim to offer a series of effective approaches to luminescent bioassay with high sensitivity and excellent specificity based on Ln3+-doped nanoprobes, which may broaden the roadway for clinical bioassays and accelerate the exploration of novel nanoprobes in versatile biomedical applications. 

Xueyuan Chen

Papers

Seven-photon absorption from Na+/Bi3+-alloyed Cs2AgInCl6 perovskites.

Size Effect on the Luminescence of Lanthanide Ions in Nanoparticles

Low cytotoxicity porous Nd(2)(SiO(4))(3) nanoparticles with near infrared excitation and emission.

Optical Spectroscopy of Lanthanide-Doped Nanoparticles

Lanthanide-Doped Inorganic Nanoprobes for Luminescent Assays of Biomarkers