Renfu Li

A Strategy to Achieve Efficient Dual‐Mode Luminescence of Eu3+ in Lanthanides Doped Multifunctional NaGdF4 Nanocrystals

Trivalent lanthanide (Ln 3 + ) ions doped luminescent nanocrystals (NCs) 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 distinct electrical, optical and magnetic properties as well as their potential applications in diverse fi elds such as LEDs, lasers, biological labeling and imaging. [ 1 ] Compared to conventional luminescent materials such as organic fl uorescent dyes and quantum dots (QDs), these Ln 3 + doped NCs show more superior features including narrow emission band widths ( < 10 nm), [ 2 ] long luminescence lifetime ( μ s–ms range) [ 2b,c ] and low long-term toxicity. [ 3 ] These features coupled with the higher resistance to photobleaching relative to that of organic fl uorescent dyes make them highly suitable for use as alternatives to organic fl uorescent dyes and QDs for various biological applications. In particular, inorganic fl uorides have the advantages of high chemical stability and intrinsic low phonon energies ( ∼ 350 cm − 1 ), and thereby are often employed as host materials for the doping of Ln 3 + to achieve the desirable downconversion (DC) or upconversion (UC) luminescence of Ln 3 + . [ 4 ] Because of well-established effi cient UC luminescence, considerable efforts have been devoted to the synthesis and multicolor tuning of Ln 3 + -doped NaYF 4 UC NCs, where Yb 3 + acting as the sensitizer with a large absorption cross-section at ∼ 980 nm is usually codoped along with the most common UC activator ions (Er 3 + , Tm 3 + and Ho 3 + ) to produce strong red, green, and violet UC emissions. [ 5 ]

Amine-Functionalized Lanthanide-Doped KGdF4 Nanocrystals as Potential Optical/Magnetic Multimodal Bioprobes

Amine-functionalized lanthanide-doped KGdF(4) nanocrystals, synthesized via a facile one-step solvothermal route by employing polyethylenimine as the surfactant and capping ligand, have been demonstrated to be sensitive time-resolved FRET bioprobes to detect a trace amount of biomolecules such as avidin at a concentration of 5.5 nM and to be potential T(1)-MRI contrast agents due to a large longitudinal relaxivity of Gd(3+) (5.86 S(-1)·mM(-1) per Gd ion and 3.99 × 10(5) S(-1)·mM(-1) per nanocrystal).

Lanthanide-doped LiLuF(4) upconversion nanoprobes for the detection of disease biomarkers.

Lanthanide-doped upconversion nanoparticles (UCNPs) have shown great promise in bioapplications. Exploring new host materials to realize efficient upconversion luminescence (UCL) output is a goal of general concern. Herein, we develop a unique strategy for the synthesis of novel LiLuF4 :Ln(3+) core/shell UCNPs with typically high absolute upconversion quantum yields of 5.0 % and 7.6 % for Er(3+) and Tm(3+) , respectively. Based on our customized UCL biodetection system, we demonstrate for the first time the application of LiLuF4 :Ln(3+) core/shell UCNPs as sensitive UCL bioprobes for the detection of an important disease marker β subunit of human chorionic gonadotropin (β-hCG) with a detection limit of 3.8 ng mL(-1) , which is comparable to the β-hCG level in the serum of normal humans. Furthermore, we use these UCNPs in proof-of-concept computed tomography imaging and UCL imaging of cancer cells, thus revealing the great potential of LiLuF4 :Ln(3+) UCNPs as efficient nano-bioprobes in disease diagnosis.

Sub-10 nm Lanthanide-Doped CaF2 Nanoprobes for Time-Resolved Luminescent Biodetection†

Lanthanide-doped luminescent nanoparticles (NPs) haveevoked considerable interest due to their superior features,such as sharp f–f emission peaks, a long photoluminescence(PL) lifetime, low toxicity, and high resistance to photo-bleaching, which make them extremely suitable for use asalternatives to organic fluorescent dyes or quantum dots forvarious bioapplications.

Full-colour fluorescent materials based on mixed-lanthanide(III) metal–organic complexes with high-efficiency white light emission

In this communication, we report a series of high-efficiency full-colour fluorescent materials based on isostructural mixed-lanthanide metal–organic complexes. By varying the stoichiometric ratio of the lanthanide ions, a fluent change of emission colours within the full-colour region was realized and strong white light-emission with a high quantum yield up to 62% was also achieved.

Er3+-Doped Anatase TiO2 Nanocrystals: Crystal-Field Levels, Excited-State Dynamics, Upconversion, and Defect Luminescence

A comprehensive survey of electronic structure and optical properties of rare-earth ions embedded in semiconductor nanocrystals (NCs) is of vital importance for their potential applications in areas as diverse as luminescent bioprobes, lighting, and displays. Er3+ -doped anatase TiO2 NCs, synthesized via a facile sol-gel solvothermal method, exhibit intense and well-resolved intra-4f emissions of Er3+ . Crystal-field (CF) spectra of Er3+ in TiO2 NCs are systematically studied by means of high-resolution emission and excitation spectra at 10-300 K. The CF analysis of Er3+ assuming a site symmetry of C(2v) yields a small root-mean-square deviation of 25.1 cm(-1) and reveals the relatively large CF strength (549 cm(-1) ) of Er3+, thus verifying the rationality of the C(2v) symmetry assignment of Er3+ in anatase TiO2 NCs. Based on a simplified thermalization model for the temperature-dependent photoluminescence (PL) dynamics from (4) S(3/2) , the intrinsic radiative luminescence lifetimes of (4) S(3/2) and (2) H(11/2) are experimentally determined to be 3.70 and 1.73 μs, respectively. Green and red upconversion (UC) luminescence of Er3+ can be achieved upon laser excitation at 974.5 nm. The UC intensity of Er3+ in Yb/Er-codoped NCs is found to be about five times higher than that of Er-singly-doped counterparts as a result of efficient Yb3+ sensitization and energy transfer upconversion (ETU) evidenced by its distinct UC luminescence dynamics. Furthermore, the origin of defect luminescence is revealed based on the temperature-dependent PL spectra upon excitation above the TiO2 bandgap at 325 nm.

Multifunctional Nano-Bioprobes Based on Rattle-Structured Upconverting Luminescent Nanoparticles†

Lanthanide-doped upconversion nanoparticles (UCNPs) have shown great promise in versatile bioapplications. For the first time, organosilica-shelled β-NaLuF4:Gd/Yb/Er nanoprobes with a rattle structure have been designed for dual-modal imaging and photodynamic therapy (PDT). Benefiting from the unique rattle structure and aromatic framework, these nanoprobes are endowed with a high loading capacity and the disaggregation effect of photosensitizers. After loading of β-carboxyphthalocyanine zinc or rose Bengal into the nanoprobes, we achieved higher energy transfer efficiency from UCNPs to photosensitizers as compared to those with conventional core-shell structure or with pure-silica shell, which facilitates a large production of singlet oxygen and thus an enhanced PDT efficacy. We demonstrated the use of these nanoprobes in proof-of-concept X-ray computed tomography (CT) and UC imaging, thus revealing the great potential of this multifunctional material as an excellent nanoplatform for cancer theranostics.

Spectroscopic evidence of the multiple-site structure of Eu 3+ ions incorporated in ZnO nanocrystals

Hexagonal Eu(3+):ZnO nanocrystals were synthesized by a modified solgel method. By means of the site-selective spectroscopy at 10 K, two kinds of luminescence sites of Eu(3+) are identified. One site exhibits a long lifetime of (5)D(0) and sharp emission and excitation peaks, which are ascribed to the inner lattice site with an ordered crystalline environment. The other site associated with the distorted lattice sites near the surface shows a relatively short lifetime of (5)D(0) and significantly broadened fluorescence lines. The energy transfer from the nanocrystal host to Eu(3+) confirms that Eu(3+) ions can, to some extent, be incorporated into the ZnO nanocrystal.

Effects of phonon confinement on the luminescence dynamics of Eu3+ in Gd2O3 nanotubes

The effects of phonon confinement on the excited state dynamics of Eu3+ in Gd2O3 nanotubes are investigated. Anomalous thermalization appears due to elimination of low-energy phonon modes in this highly efficient nanophosphor of many potential applications. It is observed that in the low-temperature excitation spectrum hot bands with fine structures originate from the lowest sublevel of 7F1 at 217?cm?1 above the ground state. The intensity of the hot bands hardly changes below 50?K, but it increases and exhibits normal Boltzmann thermalization above 50?K. The fluorescence lifetime of 5D0 (2.19?ms at 10?K) is found to be unusually longer than that of the bulk counterparts, indicating a small filling factor of 0.55 for the nanotubes. These luminescent properties are attributed to the morphology and to the lack of low-energy phonon modes in the nanotubes.

A highly luminescent chameleon: fine-tuned emission trajectory and controllable energy transfer

By varying the stoichiometric ratio of Eu3+, Tb3+ and Gd3+ ions in a lanthanide metal–organic framework, a mixed-Ln MOF, [Eu0.0040Tb0.0460Gd0.9500(BTB)(DMSO)2]·H2O, has been designed to display white-light emission. In addition, the switch between blue, white, and yellow for this material has been achieved by controlling the energy transfer process.