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AuxAg1-x Nanocomposites with 40-Fold Emission Enhancement Formed by the Electrostatic Assembly of Gold Nanoclusters and Silver Nanoclusters for Bioimaging and Bioanalysis
摘要： Noble metal nanoclusters (NCs) have been widely used in bioimaging and bioanalysis due to their unique molecular-like structures and good biocompatibility. Bright nanomaterials with high quantum yields are in need for widespread applications. Unfortunately, the weak photoluminescence (PL) of metal NCs hampers their biomedical applications, and thus it is urgent to develop effective routes to enhance their brightness, especially in aqueous solutions. In this work, we reported a facile strategy to prepare highly luminescent AuxAg1-x nanocomposites (x: molar ratio of Au) by electrostatic-induced assembly of non-luminescent glutathione (GSH) stabilized silver NCs (GSH-Ag NCs) and weak orange-emitting GSH stabilized gold NCs (GSH-Au NCs) in aqueous solutions. Transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), fluorescence spectroscopy, inductively coupled plasma mass spectrometry (ICP-MS), UV-vis absorption spectroscopy and dynamic light scattering (DLS) shed light on the mechanism of PL enhancement. It was found that the positively charged gold nanoclusters and the negatively charged silver nanoclusters formed aggregates by electrostatic force, leading to a 40-fold fluorescence intensity enhancement compared with GSH-Au NCs. This was a novel method to strengthen the fluorescence of nanoclusters with such large enhancement in aqueous solutions. With the molar ratio of Au and Ag changing from 80:1 to 2:3, the emission maximum of the AuxAg1-x nanocomposites could be tuned from 590 to 548 nm. The electrostatic force of the Au0.50Ag0.50 nanocomposites enabled them to respond to pH. The Au0.50Ag0.50 nanocomposites were fluorescent turn-on and turn-off at pH 2.6 and pH 7.5, respectively. In this respect, they can be used as a fluorescent switch and be further used as a general recyclable pH probe in the range of 2.6-7.5. This work will inspire even better strategies to further improve the brightness of noble metal NCs.
关键词： nanocomposites,fluorescent switch,electrostatic force,silver nanoclusters,fluorescence enhancement,gold nanoclusters
更新于2025-11-14 15:23:50
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A Fluorescence Light-up Silver Nanocluster Beacon Modulated by Metal Ions and Its Application in Telomerase Activity Detection
摘要： DNA-templated silver nanoclusters (DNA-AgNCs) have been extensively studied in recent years. The enhancement of fluorescence emission from the DNA-AgNCs is still being explored. Herein, we report a new study on the fluorescence enhancement of DNA-AgNCs induced by metal ions. The enhancement is greatly dependent on the primary sequence and secondary structure of DNA strands. Thus, a label-free AgNCs-based molecular beacon (MB) is explored for the detection of telomerase activity. Nonfluorescent MB-AgNCs in phosphate buffer emit a dramatic red fluorescence when Mg2+ is introduced, whereas Mg2+ has a limited effect on the weak fluorescence of DNA-AgNCs when the hairpin structure of MB is opened. Telomerase primer (TP) can be elongated by telomerase, resulting in the unfolding of MB via strand displacement reaction. Based on the different brightnesses of AgNCs produced by the two DNA templates, telomerase activity is detected. MB-AgNCs sensing platform provides a simple and low-costing method to detect telomerase activity and shows a great potential in the construction of cost-effective probes for biomolecular detection.
关键词： telomerase detection,DNA,fluorescence enhancement,silver nanocluster,metal ions
更新于2025-09-23 15:23:52
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Strong Emission Enhancement in pH-Responsive 2:2 Cucurbit[8]uril Complexes
摘要： Organic fluorophores, particularly stimuli-responsive molecules, are very interesting for biological and material sciences applications, but limited by aggregation- and rotation-caused photoluminescence quenching. A series of easily accessible bipyridinium fluorophores is reported, whose emission is quenched by a twisted intramolecular charge transfer (TICT) mechanism. Encapsulation in a cucurbit[7]uril host yields a 1:1 complex exhibiting a moderate emission increase due to destabilization of the TICT state inside the apolar cucurbituril cavity. A much stronger fluorescence enhancement is observed in 2:2 complexes with the larger cucurbit[8]uril, which is caused by additional conformational restriction of rotations around the aryl-aryl bonds. As the cucurbituril complexes are pH switchable, this system represents an efficient supramolecular ON/OFF fluorescence switch.
关键词： restriction of intramolecular motion,luminescence,host-guest complex,fluorescence enhancement,Cucurbituril
更新于2025-09-23 15:23:52
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Hydrophilic, Red-Emitting, and Thermally Activated Delayed Fluorescence Emitter for Time-Resolved Luminescence Imaging by Mitochondrion-Induced Aggregation in Living Cells
摘要： Thermally activated delayed fluorescence (TADF) materials have provided new strategies for time-resolved luminescence imaging (TRLI); however, the development of hydrophilic TADF luminophores for specific imaging in cells remains a substantial challenge. In this study, a mitochondria-induced aggregation strategy for TRLI is proposed with the design and utilization of the hydrophilic TADF luminophore ((10-(1,3-dioxo-2-phenyl-2,3-dihydro-1H-benzo[de]isoquinolin-6-yl)-9,9-dimethyl-9,10-dihydroacridin-2-yl)methyl)triphenylphosphonium bromide (NID-TPP). Using a nonconjugated linker to introduce a triphenylphosphonium (TPP+) group into the 6-(9,9-dimethylacridin-10(9H)-yl)-2-phenyl-1H-benzo[de]isoquinoline-1,3(2H)-dione (NID) TADF luminophore preserves the TADF emission of NID-TPP. NID-TPP shows clear aggregation-induced delayed fluorescence enhancement behavior, which provides a practical strategy for long-lived delayed fluorescence emission in an oxygen-containing environment. Finally, the designed mitochondrion-targeting TPP+ group in NID-TPP induces the adequate accumulation of NID-TPP and results in the first reported TADF-based time-resolved luminescence imaging and two-photon imaging of mitochondria in living cells.
关键词： time-resolved luminescence imaging,aggregation-induced delayed fluorescence enhancement,thermally activated delayed fluorescence,mitochondria-specific imaging
更新于2025-09-23 15:22:29
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Enhanced Fluorescence Emission and Magnetic Alignment Control of Biphasic Functionalized Composite Janus Particles
摘要： Janus particles, particles that have two distinct aspects on their surface or interiors, have attracted much attention due to their potential for application. For the application of Janus particles to high-resolution displays, and as light sources for optical circuits and fluorescent probes, the Janus particles should be nanosize to ensure high-resolution display and analysis, responsive to external stimuli, and highly fluorescent. However, it is still a challenging issue to develop such highly fluorescent nanoscale Janus particles and control their alignment. Magnetoresponsive Janus particles, of which the orientation can be controlled by an external magnetic field, are prepared by the simple introduction of polymer-coated magnetic nanoparticles (NPs) into the hemispheres of Janus particles. If these magnetoresponsive Janus particles can be combined with a strong fluorescence system, then they could be ideal candidates as components of the previously mentioned applications. In the present study, Janus particles are prepared with a fluorescent dye and gold nanoparticles (Au NPs) on one side. The optical properties of the resulting particles are assessed and discussed. Furthermore, the response of composite Janus particles containing dyes, Au NPs, and iron oxide NPs to an external magnetic field is discussed.
关键词： fluorescence enhancement,LSPR,magnetic alignment,Janus particles
更新于2025-09-23 15:21:21
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Self-Assembly of Europium-Containing Polyoxometalates/Tetra- <i>n</i> -alkyl Ammonium with Enhanced Emission for Cu <sup>2+</sup> Detection
摘要： Lanthanide-containing polyoxometalates (POMs) can be used to detect various materials, but their luminescence in water has suffered enormous limitations due to the strong fluorescence quenching. Herein, to resolve this problem, three-dimensional nanoparticles built by mixed Weakley-type europium-containing POMs (Na9[EuW10O36]·32H2O, abbreviated to EuW10) and tetra-n-alkyl ammonium (TA) with enhanced fluorescent properties have been designed in aqueous solution using an ionic self-assembly (ISA) technique, which is mainly driven by the electrostatic interaction between EuW10 and TA. The morphology and fluorescent properties of the system as well as some influencing factors (alkyl chain length, amino group, and inorganic salt concentration) were systematically investigated. The results indicated that the fluorescent intensity of EuW10/tetramethylammonium bromide (TMAB) composite increased about 14 times, whereas the extent of increase of fluorescence for EuW10/tetraethylammonium bromide (TEAB) and EuW10/tetrabutylammonium bromide (TMAB) composites gradually decrease due to the bulkier steric hindrance of the longer alkyl chain. Besides, the luminescence of EuW10/TMAB nanoparticles is pH responsive, and the reversibility of their structures and luminescence can be realized upon the addition of NaOH/HCl. Moreover, the EuW10/TMAB system also shows great fluorescence-sensing behavior, which could detect Cu2+ with a detection limit of 0.15 μM. Our work provides a facile construction strategy for a functional fluorescent complex via POMs-based supramolecular self-assembly in aqueous solution, which will be further used in biomarkers and sensors.
关键词： Cu2+ detection,fluorescence enhancement,ionic self-assembly,lanthanide-containing polyoxometalates,pH-responsive
更新于2025-09-23 15:21:01
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Significant enhancement of light-harvesting efficiency through the formation of [2]pseudorotaxane with γ-cyclodextrin based on a bolaamphiphile of salicylaldehyde azine moiety
摘要： In this work, we have designed and synthesized a bolaamphiphile of salicylaldehyde azine (BSA), which can form [2]pseudorotaxane with γ-cyclodextrin (BSA@γ-CD) in aqueous solution and exhibit remarkable enhancement of the fluorescence emission. Both BSA and BSA@γ-CD assembly can spontaneously form spherical aggregates in aqueous solution with diameter at about 30 nm and 20 nm, respectively. By using BSA and BSA@γ-CD as energy donor and sulforhodamine 101 (SR101) as energy acceptor, we fabricated two artificial light-harvesting systems in aqueous solution. Significantly, an efficient energy transfer process was revealed to occur between the BSA or BSA@γ-CD assembly and the loaded SR101 to obtain high energy transfer efficiency and antenna effect. More importantly, energy transfer efficiency and antenna effect can be greatly improved in these two systems only just by addition of γ-CD.
关键词： Energy transfer,Fluorescence enhancement,Pseudorotaxane,Light-harvesting,Self-assembly
更新于2025-09-23 15:21:01
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Metal-Ion Displacement Approach for Optical Recognition of Thorium: Application of a Molybdenum(VI) Complex for Nanomolar Determination and Enrichment of Th(IV)
摘要： An azine-based molybdenum (Mo(VI)) complex (M1) is exploited for selective detection of thorium (Th(IV)) ions through a metal-ion displacement protocol. Th(IV) displaces Mo(VI) from M1 instantly leading to the formation of the Th(IV) complex, having orange-red emission. Consequently, a red shift of the emission wavelength along with 41-fold ?uorescence enhancement is observed. This unique method allows detection of Th(IV) as low as 1.5 × 10?9 M. The displacement of Mo(VI) from M1 by Th(IV) is established by spectroscopic studies and kinetically followed by the stopped-?ow technique. The displacement binding constant for Th(IV) is notably strong, 4.59 × 106 M?1. Extraction of Th(IV) from aqueous solution to the ethyl acetate medium using M1 has been achieved. The silica-immobilized M1 e?ciently enriches Th(IV) from its reservoir through solid-phase extraction. Computational studies (density functional theory) support experimental ?ndings.
关键词： Solid-phase extraction,Molybdenum(VI) complex,Fluorescence enhancement,Thorium detection,Metal-ion displacement
更新于2025-09-23 15:21:01
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Silver Soret Nanoparticles for Femtomolar Sensing of Glutathione in a Surface Plasmon-Coupled Emission Platform
摘要： Surface plasmon-coupled emission (SPCE) has emerged as an interdisciplinary, versatile sensing platform due to its highly directional, solid-state and polarized emission. Here, we report the distinct properties rendered by Ag-Soret Colloids (Ag-SCs) such as nanovoids and nanocavities to observe 104-fold enhancement in emission intensity of omnidirectionally radiating emitter dipoles. Unlike earlier reports utilizing templated Ag-nanoparticles in spacer or cavity architectures, here we employ template-free, linker-less Ag-SCs. Purcell factor (PF - maximum of 120.6) obtained using the finite-difference time-domain (FDTD) simulations for soret nanocavities are in excellent agreement with the trend in emission enhancements obtained experimentally. Thermal gradient created by adiabatic cooling of Ag nanoparticles (AgNPs) drives their thermo-diffusion resulting in monodisperse nanoparticle assemblies (Ag-SCs). In addition, we report an extended-cavity architecture with Ag-SCs, as a novel pseudo-metal-dielectric-metal (p-MDM) interface, for achieving 80-fold SPCE. This study also features the unique properties of Ag-SCs as interfacial nanomaterials in SPCE platform to achieve femtomolar detection of glutathione (GSH). The quenching of fluorescence from alizarin red S-boric acid (ARS-BA) complex upon addition of Cu2+ ions and the dequenching upon GSH addition studied with Ag-SCs as spacer layer remarkably increased the sensitivity of the analyte. The uniform and intense electromagnetic field-confinement provided by these intricate architectures and hybrid interfaces, along with its ease of fabrication and versatility for variety of analytes, is critical to achieve augmented SPCE. This is accomplished without compromising on the reliability of detection as demonstrated with the use of a cellphone camera, CIE color space and luminosity plots for the turn-on fluorescence. The emission images were acquired using an android phone camera by aligning it with its angular emission, making it amenable for point-of-care diagnostics.
关键词： Soret colloids,Surface plasmon-coupled emission,spacer engineering,smartphone-based detection,template-free approach,fluorescence enhancement,glutathione sensing
更新于2025-09-23 15:19:57
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Fluorescence and Raman Enhancement Effect Caused by a Chemical Mechanism in Metal-Tetraphenylporphyrin on 2D Layered Materials
摘要： Two-dimensional (2D) layered materials exhibiting a flat surface have been strong candidates for studies investigating both the fundamental Raman enhancement in these materials and their practical applications. Here, we explore the Raman and the fluorescence enhancement effects of metal-tetraphenylporphyrin (TPP) molecules on graphene and MoSe2. We attribute the enhancement behaviors to the charge transfer interaction between the 2D materials and the adsorbates. The enhancement factors for the two flat substrates are dissimilar due to the charge transfer ability resulting from the electronic structures. The charge transfer interaction can be explained by the adsorption probability based on Langmuir's model.
关键词： Fluorescence enhancement,Raman enhancement,Two-dimensional materials
更新于2025-09-19 17:15:36