103 research outputs found
Core–Shell Lanthanide Upconversion Nanophosphors as Four-Modal Probes for Tumor Angiogenesis Imaging
Multimodality imaging overcomes the shortage and incorporates the advantages of different imaging tools. Lanthanide-based nanoprobes are unique and have rich optical, magnetic, radioactive, and X-ray attenuation properties; however, simple doping of different lanthanide cations into one host can result in a material with multifunction but not the optimized properties. In this study, using NaLuF<sub>4</sub>:Yb,Tm as the core and 4 nm of <sup>153</sup>Sm<sup>3+</sup>-doped NaGdF<sub>4</sub> (half-life of <sup>153</sup>Sm = 46.3 h) as the shell, we developed a lanthanide-based core–shell nanocomposite as an optimized multimodal imaging probe with enhanced imaging ability. The lifetime of upconversion luminescence (UCL) at 800 nm and relaxation rate (1/<i>T</i><sub>1</sub>) were at 1044 μs and 18.15 s<sup>–1</sup>·mM<sup>–1</sup>, respectively; however, no significant decrease in the attenuation coefficient was observed, which preserved the excellent X-ray imaging ability. The nanomaterial NaLuF<sub>4</sub>:Yb,Tm@NaGdF<sub>4</sub>(<sup>153</sup>Sm) was confirmed to be effective and applicable for UCL imaging, X-ray computed tomography (CT), magnetic resonance imaging, and single-photon emission computed tomography (SPECT) <i>in vivo</i>. Furthermore, the NaLuF<sub>4</sub>:Yb,Tm@NaGdF<sub>4</sub>(<sup>153</sup>Sm) nanoparticles were applied in tumor angiogenesis analysis by combining multimodality imaging of CT, SPECT, and confocal UCL imaging, which shows its value of multifunctional nanoparticles NaLuF<sub>4</sub>:Yb,Tm@NaGdF<sub>4</sub>(<sup>153</sup>Sm) in tumor angiogenesis imaging
High-Efficiency Upconversion Luminescent Sensing and Bioimaging of Hg(II) by Chromophoric Ruthenium Complex-Assembled Nanophosphors
A chromophoric ruthenium complex-assembled nanophosphor (N719-UCNPs) was achieved as a highly selective water-soluble probe for upconversion luminescence sensing and bioimaging of intracellular mercury ions. The prepared nanophosphors were characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), energy-dispersive X-ray analysis (EDXA), Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). Further application of N719-UCNPs in sensing Hg2+ was confirmed by optical titration experiment and upconversion luminescence live cell imaging. Using the ratiometric upconversion luminescence as a detection signal, the detection limit of Hg2+ for this nanoprobe in water was down to 1.95 ppb, lower than the maximum level (2 ppb) of Hg2+ in drinking water set by the United States EPA. Importantly, the nanoprobe N719-UCNPs has been shown to be capable of monitoring changes in the distribution of Hg2+ in living cells by upconversion luminescence bioimaging
Red-Light-Controllable Liquid-Crystal Soft Actuators via Low-Power Excited Upconversion Based on Triplet–Triplet Annihilation
A red-light-controllable
soft actuator has been achieved, driven
by low-power excited triplet–triplet annihilation-based upconversion
luminescence (TTA-UCL). First, a red-to-blue TTA-based upconversion
system with a high absolute quantum yield of 9.3 ± 0.5% was prepared
by utilizing platinumÂ(II) tetraÂphenylÂtetraÂbenzoÂporphyrin
(PtTPBP) as the sensitizer and 9,10-bisÂ(diÂphenylÂphosphoryl)Âanthracene
(BDPPA) as the annihilator. In order to be employed as a highly effective
phototrigger of photodeformable cross-linked liquid-crystal polymers
(CLCPs), the PtTPBP&BDPPA system was incorporated into a rubbery
polyurethane film and then assembled with an azotolane-containing
CLCP film. The generating assembly film bent toward the light source
when irradiated with a 635 nm laser at low power density of 200 mW
cm<sup>–2</sup> because the TTA-UCL was effectively utilized
by the azotolane moieties in the CLCP film, inducing their <i>trans</i>–<i>cis</i> photoÂisomerization
and an alignment change of the mesogens via an emission–reabsorption
process. It is the first example of a soft actuator in which the TTA-UCL
is trapped and utilized to create photomechanical effect. Such advantages
of using this novel red-light-controllable soft actuator in potential
biological applications have also been demonstrated as negligible
thermal effect and its excellent penetration ability into tissues.
This work not only provides a novel photoÂmanipulated soft actuation
material system based on the TTA-UCL technology but also introduces
a new technological application of the TTA-based upconversion system
in photonic devices
Blue-Emissive Upconversion Nanoparticles for Low-Power-Excited Bioimaging in Vivo
Water-soluble upconversion luminescent (UCL) nanoparticles
based
on triplet–triplet annihilation (TTA) were successfully prepared
by coloading sensitizer (octaethylporphyrin Pd complex) and annihilator
(9,10-diphenylanthracene) into silica nanoparticles. The upconversion
luminescence quantum yield of the nanoparticles can be as high as
4.5% in aqueous solution. As determined by continuous kinetic scan,
the nanoparticles have excellent photostability. Such TTA-based upconversion
nanoparticles show low cytotoxicity and were successfully used to
label living cells with very high signal-to-noise ratio. UCL imaging
with the nanoparticles as probe is capable of completely eliminating
background fluorescence from either endogenous fluorophores of biological
sample or the colabeled fluorescent probe. In particular, such blue-emissive
upconversion nanoparticles were successfully applied in lymph node
imaging in vivo of living mouse with excellent signal-to-noise ratio
(>25), upon low-power density excitation of continuous-wave 532
laser
(8.5 mW cm–2). Such high-contrast and low-power
excited bioimaging in vivo with a blue-emissive upconversion nanoparticle
as probe may extend the arsenal of currently available luminescent
bioimaging in vitro and in vivo
High-Efficiency Upconversion Luminescent Sensing and Bioimaging of Hg(II) by Chromophoric Ruthenium Complex-Assembled Nanophosphors
A chromophoric ruthenium complex-assembled nanophosphor (N719-UCNPs) was achieved as a highly selective water-soluble probe for upconversion luminescence sensing and bioimaging of intracellular mercury ions. The prepared nanophosphors were characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), energy-dispersive X-ray analysis (EDXA), Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). Further application of N719-UCNPs in sensing Hg2+ was confirmed by optical titration experiment and upconversion luminescence live cell imaging. Using the ratiometric upconversion luminescence as a detection signal, the detection limit of Hg2+ for this nanoprobe in water was down to 1.95 ppb, lower than the maximum level (2 ppb) of Hg2+ in drinking water set by the United States EPA. Importantly, the nanoprobe N719-UCNPs has been shown to be capable of monitoring changes in the distribution of Hg2+ in living cells by upconversion luminescence bioimaging
Quantum Yield Measurements of Photochemical Reaction-Based Afterglow Luminescence Materials
Afterglow
materials have become one of the most promising luminescent
materials due to their long luminescence lifetime. Photoluminescence
quantum yield (PLQY), as one of the most fundamental and essential
parameters of luminescent materials, can directly evaluate the luminescence
properties of emissive compounds. Recently, a type of afterglow material
based on a photochemical reaction has been developed. However, there
is no suitable method to measure the PLQY of these afterglow materials
due to their special luminescence principle. Herein, we present a
method to measure the PLQY for these afterglow materials by collecting
the luminescent dynamic curves of emission and excitation light at
specific wavelength regions using a commercial spectrometer and an
integrating sphere. We found that the emitted photons of this kind
of afterglow material are in direct proportion to the excitation time,
which means the PLQY is irrelevant to the excitation time
3D Long-Range Triplet Migration in a Water-Stable Metal–Organic Framework for Upconversion-Based Ultralow-Power <i>in Vivo</i> Imaging
Triplet–triplet
annihilation upconversion (TTA-UC) has gained
increasing attention because it allows for harvesting of low-energy
photons in the solar spectrum with high efficiency in relevant applications
including solar cells and bioimaging. However, the utilization of
conventional TTA-UC systems for low-power bioapplications is significantly
hampered by their general incompatibility and low efficiency in aqueous
media. Herein we report a metal–organic framework (MOF) as
a biocompatible nanoplatform for TTA-UC to realize low-power <i>in vivo</i> imaging. Our MOF consists of a porphyrinic sensitizer
in an anthracene-based Zr-MOF as a TTA-UC platform. In particular,
closely aligned chromophores in the MOF facilitate a long-range 3D
triplet diffusion of 1.6 μm allowing efficient energy migration
in water. The tunable ratio between sensitizer and annihilator by
our synthetic method also allows an optimization of the system for
maximized TTA-UC efficiency in water at a very low excitation power
density. Consequently, the low-power imaging of lymph node in a live
mouse was successfully demonstrated with an excellent signal-to-noise
ratio (SNR > 30 at 5 mW cm<sup>–2</sup>)
Hemicyanine Dye as a Surfactant for the Synthesis of Bicontinuous Cubic Mesostructured Silica
In this paper, we developed a facile way to synthesize highly ordered optically active MCM-48 at room
temperature, by using mixtures of hemicyanine dye N-alkyl-2-[p-(N,N-diethylamino)-o-(alkyloxy)]pyridinium
bromide (denoted as o-CnPOCm, Scheme ) and cetyltrimethylammonium bromide (CTAB) as the structure-directing agents. The mesoporous materials were systematically characterized by powder X-ray diffraction,
transmission electron microscopy, nitrogen sorption, and thermogravimetry. The resultant MCM-48 exibits
unusually high thermal stability. For example, in the case of o-C2POC14, it can retain its cubic structure even
under calcinations at 900 °C for 5 h, although the pore size is shifted to the micropore region because of
shrinkage of the framework. The typical surface area and pore volume are 980 m2/g and 0.44 cm3/g, respectively,
for the powder calcined under such a high temperature. This is the first report of room-temperature synthesis
of MCM-48 with such good thermal stability using cationic−cationic mixed surfactant as the structure-directing
agent. The fluorescence lifetimes of the as-synthesized mesostructured MCM-48 were also measured, and
the result showed that the incorporated dye molecules have a 1 order of magnitude longer lifetime than that
of free species in solution, showing that the hemicyanine dye molecules are well dispersed within the CTAB
surfactant matrix. Furthermore, we compared eight other dye congeners (Scheme ) to fully investigate the
mesophase resulting from the dye−CTAB system. The results show that, upon addition of the dye surfactant
to the starting mixtures, the mesostructured silica undergoes an intrinsic phase-transition process; however,
specific dye geometry is required to obtain MCM-48 at room temperature. Those functionalities as well as
the designed synthesis of this novel mesostructured MCM-48 material promise a bright future in multifunctional
optical and electric nano- and microdevices (e.g., waveguides, laser, light-emitting diodes, etc.) and also shed
light on the self-assembly behavior in complex colloidal system
Afterglow/Fluorescence Dual-Emissive Ratiometric Oxygen Probe for Tumor Hypoxia Imaging
Hypoxia
is a common feature of many diseases such as
solid tumors.
The measurement and imaging of oxygen (O2) are extremely
important for disease diagnosis and therapy evaluation. In this work,
the afterglow/fluorescence dual-emissive ratiometric O2 probe based on a photochemical reaction-based afterglow system is
reported. The afterglow is highly sensitive to O2 because
the O2 content is directly related to the 1O2 yield and eventually affects the afterglow intensity. The
O2-insensitive fluorescence of an emitter can serve as
an internal reference. As the O2 concentration changes
from 0.08 to 18.5 mg L–1, the ratio value shows
a remarkable 53-fold increase. Compared with the intensity of a single
peak, the ratiometric signal can eliminate the interference of the
probe concentration to achieve higher accuracy. This afterglow/fluorescence
dual-emissive ratiometric O2 probe is successfully applied
to hypoxia imaging in tumor-bearing mice, which may further promote
the development of O2 sensing in the biomedical field
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