Luminescence Energy Transfer Research Articles

Synthesis and spectroscopic analysis of NaCaYF6:Nd3+, Yb3+NIR emitting phosphor

Near Infra–red (NIR) emitting NaCaYF6:Nd3+and co–doped with Yb3+phosphor has been prepared by hydrothermal synthesis. The formation of Gagarinite structure of the host matrix with space group P63/m was confirmed by XRD and Rietveld analysis. FESEM analysis confirms the spherical morphology along with the homogeneity, and mapping of elemental composition by EDS analysis. NIR emission at 1065 nm due to 4F3/2→4I11/2 electronic transition of Nd3+ ion upon the exposure to 577 nm light. The prominent PL emission at 994 nm from NaCaYF6:Nd3+,Yb3+ phosphor was obtained due to 2F5/2→2F7/2 electronic transition of Yb3+ion. Yb3+ emission was sensitized by Nd3+ activator. The intensity of Yb3+emission increases at the cost of the Nd3+ luminescence. The results are ascribed to the energy transfer from Nd3+to Yb3+. The theoretical Judd-Ofelt (J-O) analysis was also reported to confirm the obtained luminescence behaviour and energy transfer (ET) mechanism of the phosphor. The obtained results specify that the phosphor has a potential application such as in–vivo, in−vitro imaging and NIR laser applications.

Investigation of luminescence properties and energy transfer mechanism in Sm3+ and Eu3+ co-doped BaY2ZnO5 red phosphors

In this investigation, the photoluminescence properties, energy transfer phenomenon of BaY2ZnO5:Sm3+/Eu3+ doped/co-doped phosphor are reported and synthesized by high temperature solid state reaction method. The crystal structure, micromorphology, optical diffuse reflectance and photoluminescence properties of the samples were studied. The results show that concentration quenching phenomenon is found. With the increase of Eu3+ ion concentration, the emission peaks of Sm3+ gradually decrease, indicating that energy transfer between Sm3+ and Eu3+. The optimal concentrations are 0.05 mol and 0.2 mol for single doping Sm3+ and Eu3+, respectively. The energy transfer efficiency is calculated to be 78.47–95.19 %. The BaY2ZnO5 phosphors have potential application value in the fields of white light LEDs and anti-counterfeiting.

Chiral Perovskite Heterostructure Films of CsPbBr3 Quantum Dots and 2D Chiral Perovskite with Circularly Polarized Luminescence Performance and Energy Transfer.

This work reports the synthesis of chiral perovskite heterostructure films by combining a two-dimensional (2D) chiral (R-/S-MBA)2PbI4 perovskite with CsPbBr3 quantum dots (QDs). The as-synthesized chiral heterostructure films exhibit obvious circularly polarized luminescence (CPL) properties, even though pure 2D chiral perovskite cannot present photoluminescence. It indicates that the chirality of the excited state of the QDs originates from the 2D chiral perovskite. The circular polarization-resolved transient absorption (TA) spectra further demonstrate that the CPL response of heterostructure films originates from the energy transfer between the chiral perovskite layer and QDs layer and the suppression of spin relaxation, which induces the imbalance of the spin population of excited states in QDs layer. In addition, the photoluminescence (PL), circular dichroism (CD), and CPL spectra of these heterostructure films can be controlled by varying the thickness and component of the chiral perovskite layer, which demonstrates that the anion exchange between chiral perovskite and CsPbBr3 QDs can tune the chemical composition and optoelectronic properties due to the low bonding energy difference between them and decrease the strain within the QDs layer to reduce the radiative recombination lifetime. This work provides guidance for the synthesis of chiral perovskites with a strong CPL response and further provides insight into the origination of CPL.

Energy transfer and color tunability in high-thermal-stability Dy3+/Tb3+ co-doped K3YF6 transparent oxyfluoride glass ceramics

The production process and comprehensive analysis of the co-doping of Dy3+ and Tb3+ in K3YF6 oxyfluoride glass-ceramics (GCs) are delved. The primary focus is on investigating the luminescent properties and energy transfer (ET) mechanisms within these systems. The embedding of well-formed K3YF6 nanocrystals within the matrix was verified through detailed analyses using X-ray diffraction (XRD) and transmission electron microscopy (TEM). Fine-tuning the Tb3+ concentration facilitated the achievement of tunable emission, ranging from a subtle yellow to a yellowish green hue, demonstrating the remarkable flexibility in color manipulation. Fluorescence analysis unmistakably demonstrates the occurrence of energy transfer occurring between Dy3+ and Tb3+ ions, attaining a peak energy transfer efficiency of 51.33 %. Additional analysis applying Dexter's energy transfer formula affirms that the fundamental mechanism of energy transfer between Dy3+ and Tb3+ ions is dipole-dipole interaction. The K3YF6 glass ceramics (GCs) incorporating Dy3+/Tb3+ nanocrystals exhibit a remarkable thermal stability, retaining 89.07 % of their original relative emission intensity at 423 K when stimulated by 350 nm light. These findings indicate that Dy3+/Tb3+ co-doped K3YF6 GCs hold significant potential in solid state lighting, positioning them as a candidate for future lighting.

Effective red emission of Sb3+ sensitized Ho3+ doped Cs2NaGdCl6 perovskite under blue excitation

Red LEDs excited by blue light have a wide range of applications in plant growth due to their simple structure. The preparation of efficient red phosphors has attracted much attention from researchers. In this paper, Cs2NaGdCl6:Ho3+ Sb3+ phosphors were synthesized by the solvothermal method, which produced the characteristic emission of Ho3+5F5→5I8 at 655 nm under 460 nm excitation. The red light at 655 nm is further enhanced after the introduction of Sb3+, and the quantum efficiency can reach 39.85 %. The luminescence mechanism and energy transfer of Sb3+ and Ho3+ were further investigated. The produced phosphor was encapsulated with a 460 nm blue chip into an LED to realize red and blue dual emission, which meets the demand for blue and red light for plant growth.

Efficient Quasi-2D Perovskite Based Blue Light-Emitting Diodes with Carbon Dots Modified Hole Transport Layer.

Quasi-2D perovskites based blue light-emitting diodes (LEDs) suffer from its poor electroluminescence performance, mainly caused by the nonradiative recombination in in defect-rich low-n phases and the unbalanced hole-electron injection in the device. Here, we developed a highly efficient quasi-2D perovskite based sky-blue LEDs behaving recorded external quantum efficiency (EQE) of 21.07% by employing carbon dots (CDs) as additives in the hole transport layer (HTL). We ascribe the high EQE to the effective engineering of CDs: (1) The CDs at the interface of HTLs can suppress the formation of low-efficient n = 1 phase, resulting a high luminescence quantum yield and energy transfer efficiency of the mixed n-phase quasi-2D perovskites. (2) The CDs additives can reduce the conductivity of HTL, partially blocking the hole injection, and thus making more balanced hole-electron injection. The CDs-treated devices have excellent Spectral stability and enhanced operational stability and could be a new alternative additive in the perovskite optoelectronic devices.

Construction of UCNPs-aptamer-AuNPs luminescence energy transfer probe for ratio detection of Staphylococcus aureus.

A ratio luminescence probe was developed for detecting Staphylococcus aureus (S. aureus) based on luminescence energy transfer (LET) using double-wavelength emission (550 nm and 812 nm) upconversion nanoparticles (UCNPs) as donor, gold nanoparticles (AuNPs) as acceptor and the aptamer for S. aureus as the specific recognition and link unit. The LET process could cause luminescence quenching because of the spectral overlap between the acceptor and the donor at 550 nm. In the presence of S. aureus, S. aureus selectively combined with the aptamer, and the AuNPs left the surface of UCNPs, which weakened the quenching effect and restored the luminescence of UCNPs. Based on this, the ratio detection was realized by monitoring the change of the luminescence signal of the probe at 550 nm and taking the luminescence signal at 812 nm as the reference signal. Crucially, the probe has a fast reaction speed, with a reaction time of 25 min, and the detection of S. aureus is realized in the concentration range of 5.0 × 103-3.0 × 105 CFU/ml, with the detection limit of 106 CFU/ml. Therefore, the ratio probe has great potential for detecting of S. aureus in food because of its high sensitivity, fast speed and good selectivity.

Broadband ∼2 μm luminescence properties and energy transfer in Tm3+/Ho3+ co-doped TeO2–Al2O3–BaF2 glass

Tm3+/Ho3+ co-doped tellurite aluminate glasses were prepared using the melt-quenching technique. Under 808 nm laser diode (LD) excitation, these glasses exhibit intense 2 μm band luminescence, with a full width at half-maximum (FWHM) of 144 nm. The energy transfer mechanism between Tm3+ and Ho3+ was explored to investigate the luminescence behavior further. Furthermore, the forward energy transfer coefficient (Tm3+→Ho3+) is greater than the backward energy transfer coefficient (Ho3+→Tm3+), indicating that Tm3+ can effectively sensitize Ho3+. As mentioned above, Tm3+/Ho3+ co-doped tellurite aluminate glass is a competitive material in the laser field.

Luminescent properties and energy transfer mechanism from Tb3+ to Eu3+ in color adjustable nano Ca5(PO4)3(OH): Eu3+,Tb3+ phosphors

Luminescent properties and energy transfer mechanism from Tb3+ to Eu3+ in color adjustable nano Ca5(PO4)3(OH): Eu3+,Tb3+ phosphors

Luminescence Study and Energy Transfer from Ce3+ to Yb3+ in Sr5(BO3)3Cl Phosphor

Luminescence Study and Energy Transfer from Ce3+ to Yb3+ in Sr5(BO3)3Cl Phosphor

Luminescence properties and energy transfer of broadband NIR phosphor Li2MgZrO4: 1.0%Cr3+, y%Yb3+

The discovery of high thermal stability, broad-band near-infrared (NIR) fluorescent phosphors holds significant potential in applications such as non-destructive testing, promoting plant growth, and night vision devices. In this study, a novel broad-band NIR phosphors Li2MgZrO4 (LMZ): 1.0 %Cr3+, y%Yb3+ were synthesized via a high-temperature solid-state reaction method, with the optimal doping concentration found to be y = 1.5. These phosphors exhibited broad NIR emission in the range of 700–1050 nm by effective energy transfer from Cr3+ to Yb3+. The maximum full width at half maximum (FWHM) of the Cr3+/Yb3+ co-doped LMZ phosphor is 270 nm. The thermal stability of the phosphors was improved with Yb3+ co-doping. Additionally, energy transfer from Cr3+ to Yb3+ was confirmed through luminescence spectra and lifetime analysis. Finally, NIR pc-LED devices composed of a 460 nm ultraviolet chip and LMZ: 1.0 %Cr3+, 1.5 %Yb3+ phosphors were fabricated, offering a highly promising source of invisible light. These results demonstrate the wide-ranging potential applications of this novel, high thermal stability, and ultra-broad NIR emitting fluorescent phosphor.

Luminescence properties and energy transfer of Ce3+, Tb3+ codoped Ba2GaB4O9Cl Phosphor

In this paper, a series of Ba2GaB4O9Cl:Ce3+,Tb3+ phosphors were synthesized by the conventional high-temperature solid-state reaction. The incorporation of Ce3+ ions as sensitizers significantly enhances the absorption and luminescence intensity of Tb3+ ions in the Ba2GaB4O9Cl phosphor. The energy transfer from Ce3+ to Tb3+ occurs through the electric quadrupole-quadrupole interaction, with an energy transfer efficiency of 48 %. The internal quantum efficiency of Ba2GaB4O9Cl:Ce3+,Tb3+ phosphor is 39.95 % upon 316 nm excitation. At 423 K, the emission intensity of Ba2GaB4O9Cl:Ce3+,Tb3+ can keep 53.28 % of its initial value at room temperature. All these results indicate that the Ba2GaB4O9Cl:Ce3+,Tb3+ phosphor has potential application for white LED.

Infrared luminescence properties and energy transfer mechanism in NaYGeO4:Tm3+ powders

Two series of NaY1-xTmxGeO4 olivines with x = 0.005–0.04 and x = 0.0–0.2 have been prepared by the solid state reaction method and citrate technique, respectively. These germanates crystallize in olivine structure and have the orthorhombic lattice, space group Pnma, Z = 4. The diffuse reflectance spectra have been measured and the optical band gap has been estimated. Under 808 nm laser diode excitation, the NaY1-xTmxGeO4 samples yield luminescence in the range of 1300–1600 nm (3H4 → 3F4) and 1600–2200 nm (3F4 → 3H6). The maximum of luminescence integrated intensity has been achieved for the composition NaY0·85Tm0.15GeO4. The luminescence decay kinetics has been explained using migration. The parameters of the cross–relaxation process: 3H4 + 3H6 → 3F4 + 3F4 were obtained taking into account the energy transfer rate between thulium ions. It is shown that the presented materials are characterized by an effective migration-accelerated cross-relaxation process, which occurs as a result of dipole-dipole interactions.

Doping a highly charged, water-soluble lanthanide complex into a hydrophobic polymer for the preparation of luminescent films

Doping a highly charged water-soluble complex in a hydrophobic polymethyl methacrylate (PMMA) to form transparent film is demonstrated with using a heptaanionic tri-TbIII complex of thiacalix[4]arene-p-tetrasulfonate (TCAS), formulated as Tb3TCAS2. A bulky hydrophobic countercation, trihexyl(tetradecyl)phosphonium (THTDP+), enabled the isolation of the Tb3TCAS2 salt, which was soluble in a PMMA solution in chloroform. The drop casting of a polymer solution containing 10 wt% THTDP–Tb3TCAS2 salt yielded a transparent film with energy-transfer luminescence. Near-infrared emitting films with Yb3TCAS2 and Nd3TCAS2 were also prepared. The luminescence lifetime (τ) (1.15 ms) of 1.0 wt% Tb3TCAS2-doped PMMA films surpassed that of the salt (0.924 ms), while the luminescence quantum yield (Φ) of the film (0.17) was smaller than that of the salt (0.33). DMSO was the suitable solvent for the salt, providing longer τ (1.40 ms) and larger Φ (0.44) at 0.50 wt%. A low salt concentration in PMMA resulted in a long lifetime. Spin-coated films had longer lifetimes (1.47 ms) at 1.0 wt% owing to a solution-like PMMA environment preventing Tb3TCAS2 aggregation. Drop-casted films had larger Φ values than spin-coated films, as the former might contain salt-like Tb3TCAS2 aggregates.

Mechanistic Insights into the Bacterial Luciferase-based Bioluminescence Resonance Energy Transfer Luminescence: The Role of Protein Complex Dimer.

Bacterial bioluminescence holds significant potential in the realm of optical imaging due to the inherent advantages of bioluminescence and ease of operation. However, its practical utility is hindered by its low light intensity. The fusion of bacterial luciferase with a highly fluorescent protein has been demonstrated to significantly enhance autonomous luminescence. Nevertheless, the underlying mechanism behind this enhancement remains unclear, and there is a dearth of research investigating the mechanistic aspects of bioluminescence resonance energy transfer (BRET) luminescence, whether it occurs naturally or can be achieved through experimental means. In this study, we investigated the phenomenon of bacterial luciferase-based BRET luminescence employing a range of computational techniques, including structural modeling, molecular docking, molecular dynamics simulations, as well as combined quantum mechanics and molecular mechanics calculations. The theoretical findings suggest that the BRET luminescence occurs through resonance energy transfer between the excited bioluminophore and the ground chromophore within the protein complex dimer. The proposed mechanism of the protein complex dimer offers a microscopic understanding of the intriguing BRET phenomenon and has the potential to inspire further practical applications in the field of optical imaging.

Clickable Polymerization-Induced Emission Luminogens Toward Color-Tunable Modification of Non-Traditional Intrinsic Luminescent Polymers.

Non-traditional intrinsic luminescent (NTIL) polymer is an emerging field, and its color-tunable modification is highly desirable but still rarely investigated. Here, a click chemistry approach for the color-tunable modifications of NTIL polymers by introducing clickable polymerization-induced emission luminogen (PIEgen), is demonstrated. Through Cu-catalyzed azide-alkyne cycloaddition click chemistry, a series of PIEgens is successful prepared, which is further polymerized via reversible addition-fragmentation chain transfer (RAFT) polymerization. Interestingly, after clickable modification, these monomers are nonemissive in both solution and aggregation states; while, the corresponding polymers exhibit intriguing aggregation-induced emission (AIE) characteristics, confirming their PIEgen characteristics. By varying alkynyl substitutions, color-tunable NTIL polymers are achieved with emission wavelength varying from 448 to 498nm, revealing a series of PIEgens and verifying the importance of modification of NTIL polymers. Further luminescence energy transfer application is carried out as well. This work therefore designs a series of clickable PIEgens and opens a new avenue for the modification of NTIL polymers via click chemistry, which may cause inspirations to the research fields including luminescent polymer, NTIL, click chemistry, AIE and modification.

Luminescence properties and energy transfer study of color temperature tunable CaSrSiO4:Dy3+,Eu3+ white phosphors

A series of CaSrSiO4:xDy3+,yEu3+ white phosphors were successfully synthesized by high-temperature solid-phase reaction technique. The physical phase, optical performance, energy transfer mechanism and thermal stability of the samples were studied. It has been shown that the concentration quenching point of CaSrSiO4:xDy3+ phosphors is x = 0.05 at the excitation of 365 nm. In CaSrSiO4:0.05Dy3+,yEu3+ phosphors, the emission intensity of Dy3+ gradually decreases with the increase of Eu3+ doping concentration. While the emission intensity of Eu3+ first increases and then decreases, the concentration quenching point of Eu3+ is y = 0.08. The analysis of the lifetime decay curves demonstrates the existence of an energy transfer process from Dy3+ to Eu3+ in CaSrSiO4:Dy3+,Eu3+ phosphors. The energy transfer from Dy3+ to Eu3+ is dominated by dipole-dipole interactions, with the highest energy transfer efficiency of 63.1 %. By adjusting the doping concentration of Eu3+, the doping of Eu3+ not only effectively improves the stability of phosphor, but also enables tunable color temperature from cold white light to neutral white light, which is a potentially promising white light emitting material.

Strong green upconversion emission from submicron spindle-shaped SrMoO4:Yb3+,Er3.

Upconversion luminescence (UCL) is a fluorescence process where two or more lower-energy photons convert into a higher-energy photon. Lanthanide (Ln3+)-doped UCL materials often suffer from weak luminescence, especially when directly synthesized by a hydrothermal (HT) process due to the existing hydroxyl group and undesirable arrangement of dopants within host lattices which quench luminescence and limit energy transfer. Therefore, additional heat treatment processes are required to enhance their UCL emission, even though direct hydrothermal synthesis without further heat treatment has the advantages of low energy consumption, fast synthesis, and wide applicability to generate UCL materials. In this study, via a HT process without annealing, we have produced Yb3+ and Er3+ co-doped SrMoO4 submicron spindles with a strong green UCL emission which can be seen with the naked eye, which HT produced oxide-based UCL materials often fail to demonstrate. We have investigated different HT synthesis conditions, such as temperature, time, pH and dopant composition, which control the nucleation, growth, lattice structure arrangement, and ultimately their UCL properties through XRD, SEM, EDS and UCL measurements. The bright green UCL from the SrMoO4:Yb,Er submicron spindles is further enhanced by post-synthesis annealing within a molten NaNO3/KNO3 system to prevent particle size growth. The green UCL intensity from the annealed SrMoO4:Yb,Er submicron spindles surpasses samples produced by the solid-state method and is comparable to that from the commercial NaYF4:Yb,Er sample. We have further studied the temperature-dependent luminescence of both the HT-prepared and molten-salt annealed SrMoO4:Yb,Er submicron spindle samples. The strong UCL from our SrMoO4:Yb,Er submicron spindles could warrant their candidacy for bioimaging and anticounterfeiting applications.

Luminescence performance and energy transfer mechanism investigation of RE3+ (Eu3+/Tb3+/Ce3+)-doped Y2O3 phosphors

Tb3+ can serve as a bridge for energy transfer between Ce3+ and Eu3+, overcoming the MMCT quench existing in Eu3+–Ce3+.

Luminescence Characteristics and Energy Transfer of Tm3+-Doped Calcium Fluoroborate Glasses for Fiber Amplifiers

The conventional melt quenching method was employed to fabricate calcium fluoroborate glasses doped with Tm2O3 (CFBTm). Optical absorption and photoluminescence spectra were recorded in the UV, Vis, and NIR wavelength ranges. Judd-Ofelt (J-O) and free-ion parameters were computed based on the absorption band intensities and energy level positions. Utilizing the J-O parameters, various radiative parameters were determined for distinct excited states of Tm3+ ions in CFB glasses. Stimulated emission cross-sections (se) and effective bandwidths (Dleff) were calculated for the observed emission bands. The increase in Tm2O3 concentration resulted in an augmentation of emission peak intensities in the visible range, followed by a decline at higher concentrations. The quenching of emission intensities was attributed to energy transfer through cross-relaxation mechanisms. The NIR emission spectrum, excited by an 808 nm laser diode (LD), exhibited a peak at 1.47 mm corresponding to the 3H4-3F4 transition, with the intensity of the NIR emission peak increasing with the concentration of Tm2O3. Furthermore, Beer-Lambert and McCumber theories were applied to assess the absorption and emission cross-sections for the prominent 3F4–3H6 transition at the 1.82 mm emission wavelength.