Showing papers by "Xueyuan Chen published in 2017"
TL;DR: This work demonstrates an effective strategy through Mn2+ substitution to fundamentally stabilize perovskite lattices of CsPbX3 QDs even at high temperatures up to 200 °C under ambient air conditions and derives significantly improved thermal stability and optical performance from the enhanced formation energy due to the successful doping of Mn2-doped QDs.
Abstract: All-inorganic cesium lead halide perovskite (CsPbX3, X = Cl, Br, and I) quantum dots (QDs), possessing high photoluminescence quantum yields and tunable color output, have recently been endowed great promise for high-performance solar cells and light-emitting diodes (LEDs). Although moisture stability has been greatly improved through separating QDs with a SiO2 shell, the practical applications of CsPbX3 QDs are severely restricted by their poor thermal stability, which is associated with the intrinsically low formation energies of perovskite lattices. In this regard, enhancing the formation energies of perovskite lattices of CsPbX3 QDs holds great promise in getting to the root of their poor thermal stability, which hitherto remains untouched. Herein, we demonstrate an effective strategy through Mn2+ substitution to fundamentally stabilize perovskite lattices of CsPbX3 QDs even at high temperatures up to 200 °C under ambient air conditions. We employ first-principle calculations to confirm that the signi...
631 citations
TL;DR: The hybrid plasmonic UC nanostructures with an optimal shell thickness exhibit an improved bioimaging performance compared with bare UCNCs, and a polarized nature of the light at both UC emission bands is observed, which stems from the relationship between the excitation polarization and GNR orientation.
Abstract: Lanthanide-doped upconversion nanocrystals (UCNCs) have recently become an attractive nonlinear fluorescence material for use in bioimaging because of their tunable spectral characteristics and exceptional photostability Plasmonic materials are often introduced into the vicinity of UCNCs to increase their emission intensity by means of enlarging the absorption cross-section and accelerating the radiative decay rate Moreover, plasmonic nanostructures (eg, gold nanorods, GNRs) can also influence the polarization state of the UC fluorescence-an effect that is of fundamental importance for fluorescence polarization-based imaging methods yet has not been discussed previously To study this effect, we synthesized GNR@SiO2@CaF2:Yb3+,Er3+ hybrid core-shell-satellite nanostructures with precise control over the thickness of the SiO2 shell We evaluated the shell thickness-dependent plasmonic enhancement of the emission intensity in ensemble and studied the plasmonic modulation of the emission polarization at the single-particle level The hybrid plasmonic UC nanostructures with an optimal shell thickness exhibit an improved bioimaging performance compared with bare UCNCs, and we observed a polarized nature of the light at both UC emission bands, which stems from the relationship between the excitation polarization and GNR orientation We used electrodynamic simulations combined with Forster resonance energy transfer theory to fully explain the observed effect Our results provide extensive insights into how the coherent interaction between the emission dipoles of UCNCs and the plasmonic dipoles of the GNR determines the emission polarization state in various situations and thus open the way to the accurate control of the UC emission anisotropy for a wide range of bioimaging and biosensing applications
148 citations
TL;DR: In vivoBioimaging tests demonstrate that ZGGO:Cr nanoparticles can efficiently eliminate tissue autofluorescence, and the nanoparticles also show good promise in long-term bioimaging as they can be easily reactivated in vivo.
Abstract: Optical bioimaging is an indispensable tool in modern biology and medicine, but the technique is susceptible to autofluorescence interference. Persistent nanophosphors provide an easy-to-perform and highly efficient means to eliminate tissue autofluorescence. However, direct synthesis of persistent nanophosphors with tunable properties to meet different bioimaging requirements remains largely unexplored. In this work, zinc gallogermanate (Zn1+xGa2–2xGexO4:Cr, 0 ≤ x ≤ 0.5, ZGGO:Cr) persistent luminescence nanoparticles with composition-dependent size and persistent luminescence are reported. The size of the ZGGO:Cr nanoparticles gradually increases with the increase of x in the chemical formula. Moreover, the intensity and decay time of persistent luminescence in ZGGO:Cr nanoparticles can also be fine-tuned by simply changing x in the formula. In vivo bioimaging tests demonstrate that ZGGO:Cr nanoparticles can efficiently eliminate tissue autofluorescence, and the nanoparticles also show good promise in lo...
130 citations
TL;DR: By utilizing the superior excitation-free persistent luminescence, this work demonstrated for the first time the application of biotinylated ZnGa2O4’s as background-free luminescent nano-bioprobes for sensitive and specific detection of avidin in a heterogeneous assay with a limit of detection down to ∼150 pM, thus revealing the great potential of these NIR PLNPs in ultrasensitive biodetection and bioimaging.
Abstract: Persistent luminescence nanoparticles (PLNPs) have shown great promise in the field of biomedicine, but are currently limited by the challenge in the synthesis of high-quality PLNPs with bright persistent luminescence and a long afterglow time. Herein, we report a facile strategy for the synthesis of monodisperse, rechargeable and LED-activated ZnGa2O4 : Cr3+ near-infrared (NIR) PLNPs based on a modified solvothermal liquid–solid-solution method. The as-synthesized PLNPs are not only flexible for bioconjugation, but could also circumvent the limitation of the weak persistent luminescence and short afterglow time that most PLNPs confronted owing to their rechargeable capability. It was unraveled that both thermal activation and quantum tunneling mechanisms contributed to the afterglow decay of the PLNPs, and the quantum tunneling was found to dictate the LED-activated afterglow intensity and lasting time. Furthermore, by utilizing the superior excitation-free persistent luminescence, we demonstrated for the first time the application of biotinylated ZnGa2O4 : Cr3+ PLNPs as background-free luminescent nano-bioprobes for sensitive and specific detection of avidin in a heterogeneous assay with a limit of detection down to ∼150 pM, thus revealing the great potential of these NIR PLNPs in ultrasensitive biodetection and bioimaging.
115 citations
TL;DR: The developed ZGO:Mn NRs possess tunable length and persistent luminescence, and they are ideal for eliminating autofluorescence interference in biosensing, making them valuable in research areas such as studying the functions of biomolecules and monitoring of molecular/cellular networks in their native contexts.
Abstract: Persistent luminescence nanoparticles (PLNPs), which can remain luminescent after cessation of excitation, have emerged as important materials in biomedicine due to their special ability to eliminate tissue autofluorescence. Even though significant advances have been made in bioimaging, studies on controlled synthesis of PLNPs with tunable properties are lacking. Until now, only a few studies have reported the synthesis of quasi-spherical ZnGa2O4:Cr PLNPs, and direct synthesis of PLNPs with other shapes and chemical compositions has not been reported. Herein, we report the direct synthesis of Zn2GeO4:Mn (ZGO:Mn) persistent luminescence nanorods (NRs). The length and persistent luminescence of ZGO:Mn NRs can be fine-tuned by simply changing the pH of the hydrothermal reaction system. Moreover, ZGO:Mn NRs exhibit rapid growth rate, and NRs with strong persistent luminescence can be obtained within 30 min of hydrothermal treatment. Aptamer-guided ZGO:Mn bioprobes were further constructed and applied to serum...
111 citations
TL;DR: NIR-triggered nanocomposites of 808 nm UCNP-PLL@CNs exhibit high capability for ROS production and efficient PDT in vitro and in vivo, and are verified by significant improvement in ROS generation.
Abstract: Photodynamic therapy (PDT) based on photosensitizers (PSs) constructed with nanomaterials has become popular in cancer treatment, especially oral carcinoma cell. This therapy is characterized by improved PS accumulation in tumor regions and generation of reactive oxygen species (ROS) for PDT under specific excitation. In the selection of near-infrared (NIR) window, 808 nm NIR light because it can avoid the absorption of water is particularly suitable for the application in PDT. Hence, multiband emissions under a single 808 nm near-infrared excitation of Nd3+ -sensitized upconversion nanoparticles (808 nm UCNPs) have been applied for the PDT effect. 808 nm UCNPs serve as light converter to emit UV light to excite inorganic PS, graphitic carbon nitride quantum dots (CNQDs), thereby generating ROS. In this study, a nanocomposite consisting UCNPs conjugated with poly-l-lysine (PLL) to improve binding with CNQDs is fabricated. According to the research results, NIR-triggered nanocomposites of 808 nm UCNP-PLL@CNs have been verified by significant improvement in ROS generation. Consequently, 808 nm UCNP-PLL@CNs exhibit high capability for ROS production and efficient PDT in vitro and in vivo. Moreover, the mechanism of PDT treatment by 808 nm UCNP-PLL@CNs is evaluated using the cell apoptosis pathway.
84 citations
TL;DR: In this article, the authors highlight the latest progress in the electronic structures, optical properties and emerging bio applications of Eu3+-activated nanoprobes, which covers from spectroscopic site symmetry, excited-state dynamics, downshifting/upconversion luminescence enhancement strategies, and luminescent biosensing, with an emphasis on their heterogeneous/homogeneous biodetection as well as in vitro and in vivo bioimaging.
60 citations
TL;DR: A unique strategy is reported for the synthesis of high-quality LiYbF4:Ln3+ core-only and core/shell UCNPs with tunable particle sizes and shell thicknesses and unraveled the dominant mechanisms of phonon-assisted cooperative energy transfer and sequential dimer ground- state absorption/excited-state absorption for the CSU process in LiYf4:Tb3+ UCNBP.
Abstract: Lanthanide (Ln3+)-doped upconversion nanoparticles (UCNPs) have attracted tremendous interest owing to their potential bioapplications. However, the intrinsic photophysics responsible for upconversion (UC) especially the cooperative sensitization UC (CSU) in colloidal Ln3+-doped UCNPs has remained untouched so far. Herein, we report a unique strategy for the synthesis of high-quality LiYbF4:Ln3+ core-only and core/shell UCNPs with tunable particle sizes and shell thicknesses. Energy transfer UC from Er3+, Ho3+ and Tm3+ and CSU from Tb3+ were comprehensively surveyed under 980 nm excitation. Through surface passivation, we achieved efficient non-cooperative sensitization UC with absolute UC quantum yields (QYs) of 3.36%, 0.69% and 0.81% for Er3+, Ho3+ and Tm3+, respectively. Particularly, we for the first time quantitatively determined the CSU efficiency for Tb3+ with an absolute QY of 0.0085% under excitation at a power density of 70 W cm-2. By means of temperature-dependent steady-state and transient UC spectroscopy, we unraveled the dominant mechanisms of phonon-assisted cooperative energy transfer (T > 100 K) and sequential dimer ground-state absorption/excited-state absorption (T < 100 K) for the CSU process in LiYbF4:Tb3+ UCNPs.
57 citations
TL;DR: A multilayer-structured design strategy to manipulate the deleterious CR-ETs in lanthanide-doped UCNPs for highly enhanced upconverting luminescence is demonstrated.
Abstract: Energy transfer (ET) is of fundamental importance in tuning the optical performance of lanthanide-doped upconversion nanoparticles (UCNPs). However, the fine control and manipulation of the ETs particularly for deleterious cross-relaxation type ETs (CR-ETs) in lanthanide-doped UCNPs remains a formidable challenge to date. Herein, we demonstrate a rational design strategy to manipulate the deleterious CR-ETs in lanthanide-doped UCNPs, by fine-tuning the distances at an extremely large length scale (>20 nm) among multiple lanthanide dopants that are simultaneously embedded into one single nanoparticle with specially designed multilayer nanostructures. The successful inhibition of the CR-ETs leads to a significantly enhanced upconversion luminescence signal with an intensity ∼70 times higher than that of co-doped conventional UCNPs. This finding paves a new way for the better control of the ETs in lanthanide-doped nanoparticles, and offers the possibility of constructing a series of promising single-nanocrystal-based anti-counterfeiting barcodes with well-identified UC emission color and lifetime outputs.
40 citations
TL;DR: In this article, a linearly polarized laser excited by light ranging from visible to near-infrared was obtained from a metal-organic framework (MOF) hybrid material ZJU-68⊃DMASM.
Abstract: Due to the periodically physical/chemical environment and high-efficient confinement effect of the metal-organic framework (MOF) only possessing 1D channels, the authors realize periodically and highly aligned dye molecule integration within the MOF hybrid material ZJU-68⊃DMASM. Such molecule integration can provide an opportunity to directly determine 4-[p-(dimethylamino)styryl]-1-methylpyridinium (DMASM) molecules in the MOF channels by electron density mapping using X-ray diffraction data. Furthermore, combining the anisotropic emission property of such molecule integration and the perfect crystal morphology of ZJU-68 serving as the natural resonant cavity, the authors obtain a single-mode linearly polarized laser excited by light ranging from visible to near-infrared.
26 citations
TL;DR: In this article, the epitaxial growth of an inert shell has been confirmed to greatly suppress the fast concentration quenching and significantly inhibit the integrity breakdown of the upconversion profile, achieving an improvement of upcon conversion quality.
Abstract: High emitter concentration in upconversion nanoparticles has rarely been studied, as it can not only decrease brightness, but can also change the emission color via altering the intensity ratio between different bands, imposing serious constraints on the content of lanthanide emitters to optimize upconversion. In this work, four sets of upconversion systems with the emitter concentration varying from 2 mol% to 20 mol% have been fabricated with ∼8 nm core and ∼10 nm core–shell nanoparticles. The epitaxial growth of an inert shell has been confirmed to greatly suppress the fast concentration quenching and significantly inhibit the integrity breakdown of the upconversion profile, achieving an improvement of upconversion quality. The mechanism of the inert shell to alleviate the concentration effect has further been proposed and the surface defects were proposed to greatly facilitate the occurrence of the concentration effect. The lifetimes of upconversion nanoparticles with different emitter concentrations have also been investigated for the core and core–shell nanoparticles. In addition, the relationship between the optical properties of nanoparticles and the thickness of the inert shell has further been unraveled.
TL;DR: The synthesis of monodisperse tetragonal-phase LaO Br:Ln3+ NCs via a modified thermal decomposition approach is reported, showing great potential of LaOBr:LN3+ nanoprobes in bioimaging.
Abstract: Lanthanide (Ln3+)-doped nanocrystals (NCs) have shown great promise in diverse bioapplications. Exploring new host materials to realize efficient downshifting (DS) and upconversion (UC) luminescence is a goal of general concern. Ln3+-doped oxybromides, which bring together the advantages of high chemical/thermal stability of oxides and low phonon energy of bromides, have been rarely reported so far. Herein, we report the synthesis of monodisperse tetragonal-phase LaOBr:Ln3+ NCs via a modified thermal decomposition approach. Ln3+ dopants in LaOBr NCs occupying surface and lattice sites were verified based on high-resolution photoluminescence spectra of Eu3+ at 10 K. Intense DS emissions were observed in Ce3+ and Ce3+/Tb3+ doped LaOBr NCs upon excitation at 353.0 nm, which is far from the deep-UV absorption band of proteins. Moreover, UC properties of LaOBr:Yb3+/Ho3+ and Yb3+/Er3+ NCs were comprehensively surveyed upon near-infrared excitation at 980 nm. Particularly, the red-to-green ratio can be markedly increased from 0.1 to ∼300 in LaOBr:Yb3+/Er3+ NCs, resulting in high-chromatic-purity single-band red UC emission. Furthermore, we have employed the LaOBr:Ln3+ NCs for cancer cell imaging by virtue of their superior optical properties, showing great potential of LaOBr:Ln3+ nanoprobes in bioimaging.