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Simultaneous enhancement of red upconversion luminescence and CT contrast of NaGdF <sub/>4</sub> :Yb,Er nanoparticles <i>via</i> Lu <sup>3+</sup> doping
摘要： To date, lanthanide-doped upconversion nanoparticles (UCNPs) have been widely reported as a promising CT contrast agent because they have high atomic numbers and big X-ray attenuation coefficient values. However, it is still a challenge to fabricate a simple multimodal imaging probe with improved image quality for early cancer diagnosis in clinical medicine. Herein, ultra-small, uniform and monodisperse β-NaGdF4:Yb,Er,X% Lu (X = 0, 1, 2.5, 4, 6, 7.5) UCNPs were prepared through a solvothermal method with high-level modulation of both the phase and morphology. Meanwhile, a remarkably enhanced red upconversion luminescence (UCL) in the β-NaGdF4:Yb,Er,X% Lu NPs was successfully realized via Lu3+ doping. It is found that as the content of Lu3+ increases from 0 to 7.5 mol%, the UCL intensity of the red emission first increases and then decreases, with the optimum doping content of Lu3+ ions of 2.5 mol%. The red UCL enhancement is ascribed to the change of the Yb–Er interionic distance controlling the Yb–Er energy transfer rate and the distortion of the local environment of Er3+ ions influencing the 4f–4f transition rates of Er3+ ions, which has been further confirmed by the experimental check of the crystallographic phase and by photoluminescence spectroscopy employing Eu3+ as the structural probe, respectively. More importantly, after being modified with the HS-PEG2000-NH2 ligand, the NH2-PEGylated-NaGdF4:Yb,Er,X% Lu NPs exhibited low cytotoxicity, high biocompatibility, and remarkably enhanced contrast performance in in vitro UCL and in vivo CT imaging. On the basis of our findings, the as-obtained functionalized UCNPs could be considered as a promising versatile dual-mode imaging probe for bioimaging, tumor diagnosis, and cancer therapy.
关键词： red luminescence enhancement,Lu3+ doping,upconversion nanoparticles,multimodal imaging,CT contrast
更新于2025-11-14 17:04:02
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Interaction of ZnO nanorods with plasmonic metal nanoparticles and semiconductor quantum dots
摘要： We model the enhancement of near band edge emission from ZnO nanorods using plasmonic metal nanoparticles and compare it with emission enhancement from ZnO with semiconducting quantum dots. Selected CdSe quantum dots with absorption energies close to those of Ag and Au nanoparticles are chosen to construct model systems with ZnO to comprehend the role of ZnO’s intrinsic defects and plasmonic excitation in realizing the spectrally selective luminescence enhancement. Excitation wavelength dependent photoluminescence spectra along with theoretical models quantifying the related transitions and plasmonic absorption reveal that a complex mechanism of charge transfer between the ZnO nanorods and metal nanoparticles or quantum dots is essential along with an optimal energy band alignment for realizing emission enhancement. The theoretical model presented also provides a direct method of quantifying the relative transition rate constants associated with various electronic transitions in ZnO and their change upon the incorporation of plasmonic nanoparticles. The results indicate that, while the presence of deep level defect states may facilitate the essential charge transfer process between ZnO and the plasmonic nanoparticles, their presence alone does not guarantee UV emission enhancement and strong plasmonic coupling between the two systems. The results offer clues to designing novel multicomponent systems with coupled plasmonic and charge transfer effects for applications in charge localization, energy harvesting, and luminescence enhancement, especially in electrically triggered nanophotonic applications.
关键词： ZnO nanorods,plasmonic metal nanoparticles,semiconductor quantum dots,luminescence enhancement,charge transfer
更新于2025-09-23 15:19:57
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Ionic Self-Assembled Luminescent Nanospheres from Cationic Polyelectrolyte and Eu-Containing Polyoxometalate
摘要： Using the ionic self-assembly (ISA) strategy to combine Eu-containing polyoxometalates (Eu-POMs) and organic molecules mainly through noncovalent electrostatic interactions can protect Eu-POMs from solvent quenching of luminescence and enhance their processability. For this reason, a cationic polyelectrolyte, branched polyethyleneimine (PEI), and a Eu-POM, Na9(EuW10O36)·32H2O (EuW10), were used here to construct luminescence-enhanced spherical aggregates with diameters ranging from 50 to 200 nm. At a fixed concentration of EuW10, the phase behavior and luminescence properties of the mixture could be modulated by the PEI concentration. Such ISA-induced aggregates could effectively shield water molecules and result in better photophysical properties. Compared to bare EuW10, the absolute quantum yield and lifetime of luminescence for aggregates increased 10 and 5 times, respectively. Meanwhile, the sensitivity of the EuW10 coordination structure to the environment made it possible for obtained aggregates being used to detect either copper cations or permanganate anions due to their strong specific quenching effects to luminescence. Such a new type of luminescent soft material not only provided a reference for exploring the luminescence enhancement mechanism of lanthanide through self-assembly in aqueous solution but also exhibited potential in detection by luminescence analysis.
关键词： polyoxometalates,permanganate detection,polyethyleneimine,ionic self-assembly,copper detection,luminescence enhancement,luminescent nanospheres
更新于2025-09-23 15:19:57
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Effects of Gd3+ codoping on the enhancement of the luminescent properties of a NaBi(MoO4)2:Eu3+ red-emitting phosphors
摘要： A series of NaBi(MoO4)2:Eu3+ and NaBi(MoO4)2:Eu3+, Gd3+ phosphors were prepared using a sol-combustion method. NaBi(MoO4)2:Eu3+ with a tetragonal scheelite structure was obtained by heat treatment at 600–800 °C. The effects of the synthetic temperature and Eu3+ concentration on the luminescent properties of the NaBi(MoO4)2:Eu3+ phosphors were investigated. Under blue excitation at 464 nm, the NaBi(MoO4)2:Eu3+ sample exhibited a strong red emission peak at 618 nm, which originated from the 5D0→7F2 transition of Eu3+. Furthermore, Gd3+ ions were codoped into NaBi(MoO4)2:Eu3+ to enhance the luminescent intensity of NaBi(MoO4)2:Eu3+, Gd3+ due to energy transfer between Gd3+ and Eu3+. The results indicated that the NaBi(MoO4)2:Eu3+, Gd3+ red phosphor could be applied to white light-emitting diodes to achieve excellent properties, such as a high color rendering index and low correlated color temperature.
关键词： NaBi(MoO4)2,Energy transfer,Luminescence enhancement,Codoping,Red phosphors
更新于2025-09-19 17:15:36
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Silver doping induced luminescence enhancement and red shift of gold nanoclusters with aggregation-induced emission
摘要： Deep understanding on the luminescence property of aggregation-induced emission (AIE) featured metal nanoclusters (NCs) is highly desired. This paper reports an systematic study on enhancing the luminescence of AIE-featured Au NCs, which is achieved by Ag doping to engineer the size/structure and aggregation states of the Au(I)-thiolate motifs in the NC shell. Moreover, by prolonging reaction time, the luminescence of the as-synthesized AuAg NCs could be further tailored from orange to red, which is also due to the variation of the Au(I)-thiolate motifs of NCs. This study can facilitate the better understanding of this AIE-featured luminescent probe and the design of other synthetic routes for this rising family of functional materials.
关键词： bimetallic,aggregation-induced emission,luminescence enhancement,nanoclusters,red shift
更新于2025-09-10 09:29:36
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Fluorescence Behavior of Bis(cyanostyryl)pyrrole Derivatives Depending on Substituent Position of Cyano Groups in Solution and in Solid State
摘要： We synthesized a novel fluorophores of distyrylpyrrole derivatives possessing cyano groups at different position on olefin. Their fluorescence properties in solution and solid state were investigated by photoluminescence quantum yield and lifetime measurement, which provided radiative decay constant (kf) and nonradiative decay constant (knr). The derivative with cyano groups at inner position of molecule, inner isomer, shows high fluorescence quantum yield (Φf = 0.43) in solution while another derivative with cyano group at outer position, outer isomer, hardly shows fluorescence (Φf < 0.01) due to the large nonradiative decay (knr > 10 ns?1). Upon formation of single crystal or nanoparticles, these difference were inverted; the quantum yield of outer and inner isomer was enhanced and diminished, respectively. We explained these differences between in solution and solid state by means of analysis of single X-ray structure and computation study.
关键词： solid emission,pyrrole derivatives,substituent effect,Solid-state luminescence enhancement
更新于2025-09-04 15:30:14