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Colloidal Crystals of NaYF <sub/>4</sub> Upconversion Nanocrystals Studied by Small-Angle X-Ray Scattering (SAXS)
摘要： Spherical NaYF4 upconversion nanocrystals with mean radii of about 5 and 11 nm are observed to form colloidal crystals, i.e., 3D assemblies of the particles with long-range order. The colloidal crystals of the larger particles form directly in solution when dispersions of the particles in toluene are stored at room temperature for several weeks. Crystallization of the smaller particles takes place when their dispersions in hexane are slowly dried at elevated temperatures. The formation and the structure of the colloidal crystals are studied by small-angle X-ray scattering (SAXS). SAXS measurements show that the smaller as well as the larger particles assemble into a face-centered cubic lattice with unit cell dimensions of a = 18.7 nm and a = 35.5 nm, respectively. The SAXS data also show that the particles in the colloidal crystals still bear a layer of oleic acid on their surfaces. The thickness of this layer is 1.5–1.8 nm, as determined by comparing the unit cell dimensions of the colloidal crystals with the mean particle sizes. The latter could be very precisely determined from the distinct oscillations observed in the SAXS data of dilute colloidal dispersions of the nanocrystals.
关键词： upconversion,colloidal crystals,nanocrystals,small-angle X-ray scattering
更新于2025-09-09 09:28:46
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Synthesis of Li+-ion activated NaYF4: Er3+/Yb3+ phosphors via a modified solid-state process for latent fingerprint detection
摘要： Li+-ion codoped NaYF4: Er3+/Yb3+ phosphors (β-NaYF4) with a hexagonal structure were synthesized via a modified solid-state route. High-speed planetary ball milling and solid-liquid mixing were simultaneously used to overcome the drawbacks of high synthesis temperatures in conventional routes. A pure β-NaYF4 phase was obtained through calcination at 600°C for 3 h. Increases in the codoping content of Li+ ion caused a slight shift in X-ray diffraction peak positions toward high angles owing to the distortion of the local crystal field. Field emission scanning electron microscope images showed agglomerated spherical particles of approximately 0.7 μm with narrow size distribution. The upconversion properties of β-NaYF4 codoped with Li+-ion were explored. Two emission bands in the green regions (520 nm and 545 nm) and one emission band in the red region (615 nm) were observed owing to the 2H11/2→4I15/2, 4S3/2→4I15/2, and 4F9/2→4I15/2 transitions of Er3+, respectively. Codoping with 6 mol% Li+ increased the upconversion intensity by three times, which was explained using the energy level diagram. The present phosphors with improved upconversion properties were utilized for latent fingerprint detection on smooth surfaces of regularly used polymer sheets, glass substrates, and compact discs. Using the present phosphors, the base elements with three-level features, such as sharp ridges, valleys, ridge flow, bifurcation, ridge shapes, and dots, were observed on all hydrophilic and hydrophobic surfaces. The prepared phosphors exhibited promising characteristics to detect the features of fingerprint impression for individual identification in forensic applications.
关键词： fingerprint detection,solid-liquid mixing,upconversion,ball milling,Li+-ion codoping
更新于2025-09-09 09:28:46
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Tuning visible emission from red to yellow of PbWO4:Yb3+/Ho3+ nanophosphor by modulating activator ion concentration
摘要： Lanthanide doped upconverting nanophosphors possesses a great appulse in many emerging applications due to their stupendous luminescence property, photostability, effective quantum efficiency, etc. In this article Yb3+ and Ho3+ doped lead tungstate synthesized by hydrothermal method has been reported. The synthesized materials were characterized by XRD, FTIR, HRTEM and photoluminescence study was carried out with the help of spectroflurophotometer. The synthesized nanophosphor is an exposition of a strong red emission which was tuned to yellow emission by increasing the concentration of Ho3+ based on green emission at 542 nm due to 5S2/5F4→5I8 transition of Ho3+ and red emission at 657 nm due to 5F5→5I8 transition of Ho3+ upon excitation at 980nm. The study of dependency of emission intensity with pump power as lnP vs lnI curve corroborate that the upconversion mechanism involves two photon process. The radiative lifetimes measured for the emission were 23.31 μs for green emission (5S2/5F4→5I8) and 50.96 μs for red emission (5F5→5I8). The club-shaped nanophosphor which we have synthesized can be bestowed in different sectors as it has a tuneable red to yellow emission characteristics and hence, it could be exercised in many applications.
关键词： Lead tungstate,Hydrothermal,Rare-earth,Upconversion,Nanophosphor
更新于2025-09-09 09:28:46
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Effect of NaF Removal on the Upconversion Phosphor NaYF <sub/>4</sub> :Yb <sup>3+</sup> , Tm <sup>3+</sup>
摘要： To improve the light conversion efficiency of the upconversion phosphor NaYF4:Yb3+, Tm3+ for use in solar cells, its phosphor surface was treated by removing the NaF phase from the surface of the NaYF4 host crystals. The surface of the phosphor was treated by a simple procedure consisting of washing, filtering, and drying. It is confirmed that the NaF compound is efficiently eliminated from the surface of NaYF4-based phosphors by this surface treatment. The experimental results strongly suggest that the removal of NaF from the surface of the NaYF4:Yb3+, Tm3+ phosphor reduces surface defects and enhances the photoluminescence characteristics of upconversion phosphors.
关键词： Water Washing,Upconversion Phosphors,NaF,NaYF4
更新于2025-09-09 09:28:46
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Near-infrared excited cooperative upconversion in luminescent Ytterbium(ΙΙΙ) bioprobes as light-responsive theranostic agents
摘要： Near-infrared (NIR) Ytterbium(III) complexes namely [Yb(dpq)(DMF)2Cl3] (1), [Yb(dppz)(DMF)2Cl3] (2), [Yb(dpq)(ttfa)3] (3) and [Yb(dppz)(ttfa)3] (4) based on photosensitizing antenna: dipyrido-[3,2-d:2’,3’-f]-quinoxaline (dpq), dipyrido-[3,2-a:2′,3′-c]-phenazine (dppz) and 4,4,4-trifluoro-1-(2-thienyl)-1,3-butanedione (Httfa), were designed as NIR bioimaging agents utilizing cooperative upconversion luminescence (CUCL) of Yb(III). Their structures, detailed photophysical properties, biological interactions, photo-induced DNA cleavage, NIR photocytotoxicity and cellular internalization and bioimaging properties were examined. Discrete mononuclear complexes adopt a seven-coordinated {LnN2O2Cl3} mono-capped octahedron (1, 2) and eight-coordinated {LnN2O6} distorted square antiprism geometry (3, 4) with bidentate N, N-donor dpq, dppz and O,O-donor ttfa ligands. The designed Yb(III) probes (3, 4) having advantages of dual sensitizing antennae (dpq/dppz and Httfa) to modulate the desirable optical properties in NIR region for bioimaging in biologically transparent window and light-responsive intracellular damage with spatiotemporal control. The lack of inner-sphere water (q = 0), remarkable photostability, large Stokes’ shifts, presence of energetically rightly poised ligand 3T states allows efficient energy transfer (ET) to the emissive 2F5/2 state of Yb(III). The unique cooperative upconversion luminescence (CUCL) of Yb(III) was observed in 1-4 in the visible blue region (λem = 490 nm) upon NIR excitation at 980 nm, makes them special candidates for NIR-to-visible or NIR-to-NIR cellular imaging probes. The CUCL property of Yb(III) were observed in the discrete mononuclear complexes both in solid state and solution. We elegantly utilized this remarkable property of Yb(III) for cellular imaging application for the first time to the our knowledge including potential uses in CUC/multiphoton excitation microscopy. The complexes exhibit significant binding propensity to DNA, HSA and BSA (K ~ 105 M-1). They effectively cleave supercoiled (SC) DNA to its nicked circular (NC) form at 365 nm via photoredox pathways. The cellular uptake studies evidently displayed cytosolic and nuclear localization of the complexes. Finally, the capability of Yb(III) complexes usage for PDT were demonstrated through significant near-IR photocytotoxicity at 980 nm CW laser. The results depicted here offers an intelligent strategy towards developing light-responsive highly photostable Yb(III) probes for NIR theranostic application in the biologically transparent phototherapeutic window.
关键词： Cooperative upconversion luminescence,NIR photocytotoxicity,NIR cellular imaging,Phototherapeutic,NIR excitation,Ytterbium
更新于2025-09-09 09:28:46
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Enhancement of Red Upconversion Emission of LiGdF <sub/>4</sub> :Yb <sup>3+</sup> /Ho <sup>3+</sup> Nanorods by Doping with Ce <sup>3+</sup>
摘要： A series of tetragonal phase LiGdF4:Yb3+/Ho3+ nanorods tri-doped with Ce3+ have been successfully prepared via a facile oil heated method at 200 °C. The visible green and red upconversion emissions have been achieved and the red emission intensity is enhanced gradually with increasing Ce3+ concentration. The ratio of red to green emission of the Ho3+ ions is boosted about 20-fold due to efficient cross relaxation processes between Ho3+ and Ce3+ ions, which promote the red emission and weaken the green emission. The crystal phase and morphology of the nanorod samples were inspected by X-ray diffraction and transmission electron microscopy, respectively. This work has great potential applications in the biological imaging, biomedical and color display applications.
关键词： Energy Transfer,Upconversion Luminescence,Nanorods LiGdF4
更新于2025-09-04 15:30:14
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Upconversion Tm3+:CeO2/Palygorskite as direct Z-scheme heterostructure for photocatalytic degradation of bisphenol A
摘要： Novel Tm3+:CeO2/palygorskite (Pal) nanocomposites were prepared by a hydrothermal-deposition method. X-ray diffraction (XRD), transmission electron microscopy (TEM), UV-Vis spectrum（UV-Vis）, photoluminescence spectroscopy（PL）and Mott-Schottky analysis were employed to characterize the products. Results indicated that Pal skeleton possessed abundant adsorption sites and shortened band gap after modified by hydrochloric acid. Tm3+ doping enhanced the utilization of solar light due to its upconversion from visible to ultraviolet light. Meanwhile, the adsorption edge of the Tm3+:CeO2 was extended to visible region with the formation of heterojunctions. The product intimated Tm3+:CeO2/Pal behaved strongest upconversion luminescence when the doping fraction of Tm3+ was optimized to be 0.02, and the photocatalytic degradation of bisphenol A (BPA) reached 86 % when the mass content of Tm3+:CeO2 as compared to Pal was optimized to 10 wt%. The direct Z-scheme system was constructed between Pal and Tm3+:CeO2 leading to the improved charge-separation efficiency and maintenance of high redox potential.
关键词： CeO2,Upconversion,Palygorskite,Photocatalysis,Z-scheme
更新于2025-09-04 15:30:14
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Upconversion Properties of BaY2(MoO4)4:Er3+/Yb3+ Green Phosphors Synthesized via Cyclic Microwave-Modified Sol-Gel Route
摘要： The double molybdate BaY2(MoO4)4:Er3+/Yb3+ phosphors with the doping concentrations of Er3+ and Yb3+ (Er3+ = 0.05, 0.1, 0.2 and Yb3+ = 0.2, 0.45) have been successfully synthesized by a cyclic microwave-modified sol-gel process and their upconversion properties have been investigated. Well-crystallized particles were formed after heat treatment at 900 °C for 12 h, showing a fine and homogeneous morphology. Under excitation at 980 nm, BaY2(MoO4)4:Er3+/Yb3+ particles exhibited a strong 525 nm emission band and a weak 550 nm emission band in the green region and a very weak 655 nm emission band in the red region. The Raman spectra of the particles indicated the strong peaks at higher frequencies and weak peaks at lower frequencies.
关键词： Raman Spectroscopy,Upconversion properties,Green phosphors,Microwave-modified sol-gel
更新于2025-09-04 15:30:14
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Combination of CuS and g-C3N4 QDs on upconversion nanoparticles for targeted photothermal and photodynamic cancer therapy
摘要： Combined therapy with multimodal therapeutic agents based on nanomaterials has been shown as a promising approach to cancer treatment. In this report, a highly efficient multifunctional anti-cancer nanocomposite was fabricated by assembling a photothermal agent (CuS nanoparticles) and a photodynamic agent (g-C3N4 quantum dots) on upconversion nanoparticles (UCNPs) after mesoporous silica coating. Then, the surface modification of the obtained nanocomposite (abbreviated as CUSCs) with polyethylene glycol (PEG) and folic acid (FA) endows the final sample (denoted as CUSCs-PEG-FA) with an excellent cancer cell targeting effect and biocompatibility. In this nanoplatform, CuS nanoparticles are an inorganic substance with low toxicity and high photothermal conversion efficiency. g-C3N4 QDs have excellent biocompatibility and are beneficial for cellular uptake due to their small size. UCNPs can be excited by near-infrared (NIR) light to produce ultraviolet and visible (UV-vis) light emission, which overlaps with the UV absorption peak of high fluorescence g-C3N4 quantum dots (QDs). Therefore, when the nanocomposite is excited by 808 nm NIR light, a synergistic treatment effect will be presented. Since the wavelengths absorbed by the chosen photothermal agent and the photosensitizer are different, sufficient utilization of energy can be achieved. Combining photothermal therapy (high photothermal conversion efficiency of 27.4%) and photodynamic therapy can inhibit cancer more effectively compared to any monotherapy. Moreover, as a result of the inherent performance ability of the doped rare earth ions, excellent applicability for computed tomography (CT), upconversion luminescence (UCL) and magnetic resonance imaging (MRI) has been achieved.
关键词： CuS,Upconversion,g-C3N4,Synergistic treatment,Biocompatibility
更新于2025-09-04 15:30:14
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Photon Upconverted Circularly Polarized Luminescence via Triplet-Triplet Annihilation
摘要： 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 glum through energy transfer process and dual upconverted and downconverted CPL emission through chirality and energy transfer process.
关键词： triplet–triplet annihilation,photon upconversion,energy transfer,triplet energy migration,circularly polarized luminescence
更新于2025-09-04 15:30:14