稀土掺杂复式钨酸盐纳米晶体的制备及发光性能

应用水热合成技术制备了稀土掺杂复式钨酸盐NaRe（WO4）2（Re=La,Y,Gd）纳米晶体,水热合成温度随Re^3＋种类的不同而呈现较大的差异.稀土离子在NaRe（WO4）2纳米晶体中处于非反演对称中心位置.在980nm红外光激发下,Yb^3＋和Er^3＋共掺的NaRe（WO4）2纳米晶体可产生明显的绿色上转换发光,发光机理为双光子过程.     

Enforcing Luminescence at Organic Nanointerfaces: Luminescence Spatial Confinement and Amplification in Molecular‐Based Core–Shell Nanoparticles

Fully organic core–shell nanoparticles that promote luminescence spatial confinement and enhancement at the core–shell nanointerface are designed and prepared. These molecular‐based bicomponent nanostructures give rise to very efficient directional excitation energy transfer from the shell to acceptor molecules in the core located at the core–shell nanointerface. A striking luminescence enhancement is observed with respect to the corresponding single‐component nanoparticles, which is ascribed to large local electric fields generated at the nanointerface between the polarizable molecular core and shell.     

Responsive Upconversion Nanoprobe for Background‐Free Hypochlorous Acid Detection and Bioimaging

Responsive nanoprobes play an important role in bioassay and bioimaging, early diagnosis of diseases and treatment monitoring. Herein, a upconversional nanoparticle (UCNP)‐based nanoprobe, Ru@UCNPs, for specific sensing and imaging of hypochlorous acid (HOCl) is reported. This Ru@UCNP nanoprobe consists of two functional components,, i.e., NaYF₄:Yb, Tm UCNPs that can convert near infrared light‐to‐visible light as the energy donor, and a HOCl‐responsive ruthenium(II) complex [Ru(bpy)₂(DNCH‐bpy)](PF₆)₂ (Ru‐DNPH) as the energy acceptor and also the upconversion luminescence (UCL) quencher. Within this luminescence resonance energy transfer nanoprobe system, the UCL OFF–ON emission is triggered specifically by HOCl. This triggering reaction enables the detection of HOCl in aqueous solution and biological systems. As an example of applications, the Ru@UCNPs nanoprobe is loaded onto test papers for semiquantitative HOCl detection without any interference from the background fluorescence. The application of Ru@UCNPs for background‐free detection and visualization of HOCl in cells and mice is successfully demonstrated. This research has thus shown that Ru@UCNPs is a selective HOCl‐responsive nanoprobe, providing a new way to detect HOCl and a new strategy to develop novel nanoprobes for in situ detection of various biomarkers in cells and early disgnosis of animal diseases.     

Rare‐Earth‐Element‐Ytterbium‐Substituted Lead‐Free Inorganic Perovskite Nanocrystals for Optoelectronic Applications

Lead‐(Pb‐) halide perovskite nanocrystals (NCs) are interesting nanomaterials due to their excellent optical properties, such as narrow‐band emission, high photoluminescence (PL) efficiency, and wide color gamut. However, these NCs have several critical problems, such as the high toxicity of Pb, its tendency to accumulate in the human body, and phase instability. Although Pb‐free metal (Bi, Sn, etc.) halide perovskite NCs have recently been reported as possible alternatives, they exhibit poor optical and electrical properties as well as abundant intrinsic defect sites. For the first time, the synthesis and optical characterization of cesium ytterbium triiodide (CsYbI₃) cubic perovskite NCs with highly uniform size distribution and high crystallinity using a simple hot‐injection method are reported. Strong excitation‐independent emission and high quantum yields for the prepared NCs are verified using photoluminescence measurements. Furthermore, these CsYbI₃ NCs exhibit potential for use in organic–inorganic hybrid photodetectors as a photoactive layer. The as‐prepared samples exhibit clear on–off switching behavior as well as high photoresponsivity (2.4 × 10³ A W^?1) and external quantum efficiency (EQE, 5.8 × 10⁵%) due to effective exciton dissociation and charge transport. These results suggest that CsYbI₃ NCs offer tremendous opportunities in electronic and optoelectronic applications, such as chemical sensors, light emitting diodes (LEDs), and energy conversion and storage devices.     

In Vivo Repeatedly Activated Persistent Luminescence Nanoparticles by Radiopharmaceuticals for Long‐Lasting Tumor Optical Imaging

Persistent luminescence nanoparticles (PLNPs) with rechargeable near‐infrared afterglow properties attract much attention for tumor diagnosis in living animals since they can avoid tissue autofluorescence and greatly improve the signal‐to‐background ratio. Using UV, visible light, or X‐ray as excitation sources to power up persistent luminescence (PL) faces the challenges such as limited tissue penetration, inefficient charging capability, or tissue damage caused by irradiation. Here, it is proved that radiopharmaceuticals can efficiently excite ZnGa₂O₄:Cr³⁺ nanoparticles (ZGCs) for both fluorescence and afterglow luminescence via Cerenkov resonance energy transfer as well as ionizing radiation. ¹⁸F‐FDG, a clinically approved tumor‐imaging radiopharmaceutical with a short decay half‐life around 110 min, is successfully used as the internal light source to in vivo excite intravenously injected ZGCs for tumor luminescence imaging over 3 h. The luminescence with similar decay time can be re‐obtained for multiple times upon injection of ¹⁸F‐FDG at any time needed with no health concern. It is believed this strategy can not only provide tumor luminescence imaging with high sensitivity, high contrast, and long decay time at desired time, but also guarantee the patients much less radiation exposure, greatly benefiting image‐guided surgery in the future.     

Water‐Dispersible,pH‐Stable and Highly‐Luminescent Organic Dye Nanoparticles with Amplified Emissions for In Vitro and In Vivo Bioimaging

A new strategy is presented for using doped small‐molecule organic nanoparticles (NPs) to achieve high‐performance fluorescent probes with strong brightness, large Stokes shifts and tunable emissions for in vitro and in vivo imaging. The host organic NPs are used not only as carriers to encapsulate different doped dyes, but also as fluorescence resonance energy transfer donors to couple with the doped dyes (as acceptors) to achieve multicolor luminescence with amplified emissions (AE). The resulting optimum green emitting NPs show high brightness with quantum yield (QY) of up to 45% and AE of 12 times; and the red emitting NPs show QY of 14% and AE of 10 times. These highly‐luminescent doped NPs can be further surface modified with poly(maleic anhydride‐alt‐1‐octadecene)‐polyethylene glycol (C18PMH‐PEG), endowing them with excellent water dispersibility and robust stability in various bio‐environments covering wide pH values from 2 to 10. In this study, cytotoxicity studies and folic acid targeted cellular imaging of these multicolor probes are carried out to demonstrate their potential for in vitro imaging. On this basis, applications of the NP probes in in vivo and ex vivo imaging are also investigated. Intense fluorescent signals of the doped NPs are distinctly, selectively and spatially resolved in tumor sites with high sensitivity, due to the preferential accumulation of the NPs in tumor sites through the passive enhanced permeability and retention effect. The results clearly indicate that these doped NPs are promising fluorescent probes for biomedical applications.     

Endowing Perovskite Nanocrystals with Circularly Polarized Luminescence

Perovskite nanocrystals are attracting great interest due to their excellent photonic properties. Here, through a supramolecular self‐assembly approach, the perovskite nanocrystals (NCs) with a novel circularly polarized luminescence (CPL) are successfully endowed. It is found that the achiral perovskite NCs can coassemble with chiral gelator in nonpolar solvents, in which the gelator molecules modify the surface of the perovskite NCs. Through such cogelation, the molecular chirality can transfer to the NCs resulting in CPL signals with a dissymmetric factor (g_lum) up to 10^?3. Furthermore, depending on the molecular chirality of the gelator, the CPL sense can be selected and the mirror‐imaged CPL is obtained. Such gels can be further embedded into the polymer film to facilitate flexible CPL devices. It is envisaged that this approach will afford a new insight into the designing of the functional chiroptical materials.     

Design,Properties, and In Vivo Behavior of Super­paramagnetic Persistent Luminescence Nanohybrids

With the fast development of noninvasive diagnosis, the design of multimodal imaging probes has become a promising challenge. If many monofunctional nanocarriers have already proven their efficiency, only few multifunctional nanoprobes have been able to combine the advantages of diverse imaging modalities. An innovative nanoprobe called mesoporous persistent luminescence magnetic nanohybrids (MPNHs) is described that shows both optical and magnetic resonance imaging (MRI) properties intended for in vivo multimodal imaging in small animals. MPNHs are based on the assembly of chromium‐doped zinc gallate oxide and ultrasmall superparamagnetic iron oxide nanoparticles embedded in a mesoporous silica shell. MPNHs combine the optical advantages of persistent luminescence, such as real time imaging with highly sensitive and photostable detection, and MRI negative contrast properties that ensure in vivo imaging with rather high spatial resolution. In addition to their imaging capabilities, these MPNHs can be motioned in vitro with a magnet, which opens multiple perspectives in magnetic vectorization and cell therapy research.     

UV–Vis–NIR Full‐Range Responsive Carbon Dots with Large Multiphoton Absorption Cross Sections and Deep‐Red Fluorescence at Nucleoli and In Vivo

Carbon dots (CDs), with excellent optical property and cytocompatibility, are an ideal class of nanomaterials applied in the field of biomedicine. However, the weak response of CDs in the near‐infrared (NIR) region impedes their practical applications. Here, UV–vis–NIR full‐range responsive fluorine and nitrogen doped CDs (N‐CDs‐F) are designed and synthesized that own a favorable donor‐π‐acceptor (D‐π‐A) configuration and exhibit excellent two‐photon (λ_ex = 1060 nm), three‐photon (λ_ex = 1600 nm), and four‐photon (λ_ex = 2000 nm) excitation upconversion fluorescence. D‐π‐A‐conjugated CDs prepared by solvothermal synthesis under the assistance of ammonia fluoride are reported and are endowed with larger multiphoton absorption (MPA) cross sections (3PA: 9.55 × 10^?80 cm⁶ s² photon^?2, 4PA: 6.32 × 10^?80 cm⁸ s³ photon^?3) than conventional organic compounds. Furthermore, the N‐CDs‐F show bright deep‐red to NIR fluorescence both in vitro and in vivo, and can even stain the nucleoli of tumor cells. A plausible mechanism is proposed on the basis of the strong inter‐dot and intra‐dot hydrogen bonds through N? H···F that can facilitate the expanding of conjugated sp² domains, and thus not only result in lower highest occupied molecular orbital‐lowest unoccupied molecular orbital energy level but also larger MPA cross sections than those of undoped CDs.     

Photon Upconverted Circularly Polarized Luminescence via Triplet–Triplet Annihilation

Circularly polarized luminescent materials are of increasing attention due to their potential applications in advanced optical technologies, such as chiroptical devices and optical sensing. Recently, in all reported circularly polarized luminescent materials, high‐energy excitation results in low‐energy or downconverted circularly polarized luminescence (CPL) emission. Although photon upconversion—i.e., the conversion of low‐energy light into higher‐energy emission, with a wide variety of applications—has been widely reported, the integration of photon upconversion and CPL in one chiral system to achieve higher‐energy CPL emission has never been reported. Herein, a brief review is provided of recent achievements in photon‐upconverted CPL via the triplet–triplet annihilation mechanism, focusing on the amplified dissymmetry factor g_lum through energy transfer process and dual upconverted and downconverted CPL emission through chirality and energy transfer process.     

Upconversion Luminescence Resonance Energy Transfer (LRET)‐Based Biosensor for Rapid and Ultrasensitive Detection of Avian Influenza Virus H7 Subtype

Avian influenza viruses (AIV) with good adaptation and various mutations have threatened both human and animals’ health. The H7 subtypes have the potential to cause pandemic threats to human health due to the highly pathogenic characteristics. Therefore, it is quite urgent to develop a novel biosensor for rapid and sensitive detection of H7 subtypes. In this work, a biosensor based on luminescence resonance energy transfer (LRET) from BaGdF₅:Yb/Er upconversion nanoparticles (UCNPs) to gold nanoparticles (AuNPs) has been developed for rapid and sensitive H7 subtypes detection. The amino modified capture oligonucleotide probes are covalently linked to poly(ethylenimine) (PEI) modified BaGdF₅:Yb/Er UCNPs. The thiol modified oligonucleotides with H7 hemagglutinin gene sequence are conjugated to surfaces of AuNPs. The hybridization process between complementary strands of H7 Hemagglutinin gene and its probe brings the energy donor and acceptor into close proximity, leading to the quenching of fluorescence of UCNPs. A linear response is obtained ranging from 10 pm to 10 nm and the limit of detection (LOD) is around 7 pm with detection time around 2 hours. This biosensor is expected to be a valuable diagnostic tool for rapid and sensitive detection of AIV.     

Chromophore‐Modified Highly Selective Ratiometric Upconversion Nanoprobes for Detection of ONOO−‐Related Hepatotoxicity In Vivo

Acute hepatitis is a major problem affecting public health and has attracted more and more attention. Generally, as the standard means, blood tests are taken for evaluating hepatitis. However, such tests fail to accurately reflect the level of hepatitis in vivo. Herein, two highly selective ratiometric fluorescent probes are designed to track peroxynitrite (ONOO^?) as the hepatitis indicator, and further evaluate acute liver injury in vivo through dye‐grafted upconversion nanoparticles (UCNPs). Specifically, upconversion luminescence of nanoprobes at 540 or 660 nm can be quenched by the designed and synthesized chromophore E‐CC or H‐CC, that can be destroyed by ONOO^? via energy transfer (ET) process, while the upconversion luminescence intensity at 810 nm remains the same. Thus, the developed nanoprobes can be used for ratiometric detection (I₅₄₀/I₆₆₀ or I₆₆₀/I₈₁₀) of ONOO^?. Moreover, the developed near infrared ratiometric nanoprobes can highly selectively detect ONOO^?, which can eliminate the interference of HOCl and SO₃^2?. Finally, it is demonstrated that this highly selective ratiometric nanosystem can achieve effective detection of ONOO^? in living cells and CCl₄‐induced acute liver injury models. It provides some reference value for clinical detection of hepatotoxicity.     

Instantaneous In Vivo Imaging of Acute Myocardial Infarct by NIR‐II Luminescent Nanodots

Fast and precise localization of ischemic tissues in the myocardium after an acute infarct is required by clinicians as the first step toward accurate and efficient treatment. Nowadays, diagnosis of a heart attack at early times is based on biochemical blood analysis (detection of cardiac enzymes) or by ultrasound‐assisted imaging. Alternative approaches are investigated to overcome the limitations of these classical techniques (time‐consuming procedures or low spatial resolution). As occurs in many other fields of biomedicine, cardiological preclinical imaging can also benefit from the fast development of nanotechnology. Indeed, bio‐functionalized near‐infrared‐emitting nanoparticles are herein used for in vivo imaging of the heart after an acute myocardial infarct. Taking advantage of the superior acquisition speed of near‐infrared fluorescence imaging, and of the efficient selective targeting of the near‐infrared‐emitting nanoparticles, in vivo images of the infarcted heart are obtained only a few minutes after the acute infarction event. This work opens an avenue toward cost‐effective, fast, and accurate in vivo imaging of the ischemic myocardium after an acute infarct.