Dipole-dipole Energy Transfer Research Articles

Expanding near-infrared emission bandwidth in K2NaCrF6:Fe3+ phosphors through dipole-dipole energy transfer

Currently, the application potential of Cr3+ doped near-infrared (NIR) fluoride phosphors excited by blue light is promising. However, the development of near-infrared fluoride phosphors with wider emission bandwidth remains a challenge. Herein, we employed the hydrothermal method to prepare K2NaCrF6:Fe3+ phosphors. Upon excitation at 432 nm, the K2NaCrF6:xFe3+ phosphors exhibited broad near-infrared emission, with the main peak ranging from 752 nm to 780 nm. As the Fe3+ concentration increased, the luminescence intensity of the K2NaCrF6:xFe3+ phosphor decreased, accompanied by a redshift in the emission band and an increase in the full width of the emission spectrum half-peak. These changes can be attributed to the dipole-dipole interaction, specifically the energy transfer between Fe3+ and Cr3+, leading to the 4T2(4F) → 4A2(Cr3+) and 4T1(4G) → 6A1(6S) (Fe3+) transitions.

Europium-doped strontium gadolinium oxide phosphor: Investigating structural and photoluminescence characteristics via sol-gel combustion synthesis

SrGd2O4 phosphors doped with Eu3+ were successfully synthesized through a sol-gel combustion method, covering a range of dopant concentrations from 0.25 mol% to 3 mol%. The structural analysis of these phosphor materials was comprehensively conducted utilizing various techniques, including X-ray powder diffraction analysis (XRD), Energy Dispersive X-ray (EDX), and Fourier-transform infrared spectroscopy (FTIR). In addition to unveiling the structural characteristics, these analyses provide valuable insights into the compositional aspects, enhancing our understanding of the synthesized SrGd2O4:Eu3+ phosphors across different doping levels. XRD analysis findings validate the successful generation of the intended SrGd2O4 host, demonstrating orthorhombic system structures consistent with JPCD card number 98-019-3592. FTIR analyses conducted on the phosphor samples not only identify bending modes but also reveal intricate details about small vibration bonds within the material. When excited by the 349 nm laser, SrGd2O4:xEu3+ phosphors exhibit distinct photoluminescence (PL) properties like red emission at 614 nm from Eu3+. From the emission spectra, one can clearly observe that Eu3+ with an ionic radius close to the Gd3+ ion preferentially occupies the symmetry sites of the host lattice. The optimal doping concentration was determined to be 0.5 mol%, as revealed by the data in our study. Additionally, a deeper understanding of the luminescence quenching mechanism was attained, pinpointing the involvement of dipole-dipole (d-d) energy transfer in this intriguing phenomenon. This optimal concentration not only enhances the material's properties but also underscores the pivotal role of d-d interactions in governing the luminescence behavior within the doped system.

Experimental evidence of Förster energy transfer enhancement in the near field through engineered metamaterial surface waves

Plasmonics has been demonstrated to provide fine tuning of the emission properties of single quantum sources (brightness, polarization, directivity, spectrum, lifetime…). However, significantly less is known about the role of surface plasmons in mediating subwavelength Förster resonant energy transfer (FRET) when a second emitter is introduced. Here, we report microwave experiments showing that excitation of surface waves on a dedicated metasurface can strongly mediate FRET in the near-field regime. This work paves the way for metasurfaces engineered to control dipole-dipole energy transfer with applications in lighting sources, photovoltaics, quantum information processing and biophysics.

Upconversion luminescence enhancement of the ytterbium oxide with gold nanoparticles on anodized titanium surface

This paper presents a study of the cooperative luminescence (upconversion) process of Yb2O3 with gold nanoparticles on the anodized titanium surface. The luminescence of the samples was registered under two-photon excitation with using infrared laser (λ = 980 nm) and a quasi-continuous femtosecond laser (λ = 1030 nm). It was found that the quantum yield of luminescence in the presence of gold nanoparticles increases in 5.6 times fold as a result of non-radiative plasmon energy transfer. The constant of non-radiative dipole-dipole energy transfer was calculated with using the Förster model under the plasmon energy generation. It is also shown that under photoexcitation with wavelength of 980 nm at low temperatures (80 K), the intensity of upconversion luminescence increases according to the quadratic function of the excitation energy, which confirms the existence of upconversion luminescence generation by the mechanism of simultaneous energy transfer involving two Yb3+ ions in the oxide crystal.

Role of Spin-Orbit Coupling in Long Range Energy Transfer in Metal-Organic Frameworks.

Metal-organic frameworks (MOFs) are emerging as a promising platform for solar energy conversion applications. Their potential utilization as efficient chromophores in artificial photosynthesis is closely related to the understanding of light-harvesting and energy transfer processes that occur within these molecular scaffolds. Herein, we present the photophysical investigation of Ru(II), Ir(III), and Os(II) polypyridyl complexes incorporated into the backbone of UiO-67. In this work, we systematically study the effect of spin-orbit coupling on dipole-dipole energy transfer in MOFs using steady-state and time-resolved spectroscopic techniques. The results of our work indicate successful triplet-to-singlet energy transfer and a sizable increase in the transfer kinetics and critical distance, as direct consequences of strong spin-orbit couplings. Remarkably, the reported R0 value for OsDCBPY (R0 = 88 ± 10 Å) represents one of the largest Förster distances observed in an MOF. Collectively, this work contributes to the general knowledge of energy transfer in materials and provides groundwork for efficient utilization in artificial photosynthetic assemblies.

Detection of energy transfer mechanisms in nanoscopic optical rulers

Understanding the energy transfer dynamics in fluorescein-gold nanoparticle systems is crucial for future optoelectronic devices based on energy transfer. Dominant energy transfer mechanisms including the dipole-dipole (FRET) and dipole-surface energy transfer (SET) are investigated. We have compared the measured performance values with the theoretical predictions for both FRET and SET models, specifically the importance of interactions between various scales. It has been shown that the highly sensitive FRET process is limited and focused on the Forster radius range (R0), while the high efficiency of the SET over longer distances provides better resolution than the FRET process. The detection and quantitation of the energy transfer mechanism might be to playing a critical role in improving spatial resolution, distance range, and spectral sensitivity for biophysical studies. Graphical abstract

Single-Chain Lanthanide Luminescence Biosensors for Cell-Based Imaging and Screening of Protein-Protein Interactions.

SummaryLanthanide-based, Förster resonance energy transfer (LRET) biosensors enabled sensitive, time-gated luminescence (TGL) imaging or multiwell plate analysis of protein-protein interactions (PPIs) in living cells. We prepared stable cell lines that expressed polypeptides composed of an alpha helical linker flanked by a Tb(III) complex-binding domain, GFP, and two interacting domains at each terminus. The PPIs examined included those between FKBP12 and the rapamycin-binding domain of m-Tor (FRB) and between p53 (1–92) and HDM2 (1–128). TGL microscopy revealed dramatic differences (>500%) in donor- or acceptor-denominated, Tb(III)-to-GFP LRET ratios between open (unbound) and closed (bound) states of the biosensors. We observed much larger signal changes (>2,500%) and Z′-factors of 0.5 or more when we grew cells in 96- or 384-well plates and analyzed PPI changes using a TGL plate reader. The modular design and exceptional dynamic range of lanthanide-based LRET biosensors will facilitate versatile imaging and cell-based screening of PPIs.

Dipole-dipole energy transfer mechanism to the blue-white-red color-tunable emission presented by CaYAlO4:Tb3+,Eu3+ biocompatibility material obtained by the simple and low cost of chemical route

Color tunable blue-white-red emitting CaY0.99-xTb0.01EuxAlO4 phosphors were prepared by an easy and low-cost chemical route using citric acid as precursor. The structural and morphological properties were evaluated by XRD and SEM techniques. The photoluminescence spectra and decay curves under excitation at 352 nm reveals the energy transfer process from Tb3+ to Eu3+. The dependence of temperature on energy transfer was evaluated, indicating higher efficiency as the temperature increases The dominant mechanism was demonstrated to be dipole-dipole type. By adjusting the excitation wavelength, the color emission of CaYAlO4:Tb3+,Eu3+solids can be tuned from blue to red, through white light. The cell viability of this materials was performed in the saccharomyces cerevisiae medium culture observing the biocompatibility with 160 and 320 μg/mL of concentration. In parallel the white emission performance was analyzed by determining the CIE coordinates and color correlated temperature (CCT). The CaY0.985Tb0.01Eu0.005AlO4 material showed CIE coordinates (0.327, 0334) and CCT = 5755 K, making this material an example of single-phase white emitting system.

Tunable blue-green emission and energy transfer properties in Ba2SiO4:Tb3+ obtained from sol-gel method

Herein, we introduce an adapted sol-gel synthesis of blue-green-emitting phosphors based on Ba2SiO4:Tb3+, which were obtained in a quite-soft calcination condition (1100 °C/2 h) as a monophasic crystalline phase, space group Pmcn (62), characterized by high-agglomerated particles. The optical band gap value decreases as the amount of Tb3+ increases, from 5.65 eV (undoped) to 4.40 eV (5 %-doped). All doped samples are excited by UV radiation (250 nm), emitting in the blue and green spectral region as a result of the Tb3+ transitions arising from the 5D3 and 5D4 excited levels, respectively. Yet, the overall emitted color of the phosphor is tuned by the Tb3+ concentration since the increase of the activator amount dislocates the emission color from blue toward green due to a dipole-dipole energy transfer between two close Tb3+ ions. The emission quantum efficiency of the 5D4 state is a function of the emission intensity and it enhances up to the 4 %-doped sample. A new approach to calculate the 5D3 state quantum efficiency of Tb3+ is also proposed and these values decrease from 95.3% to 42.4% as the doping amount enhances from 0.1 up to 5%. Thus, both the green-blue color tunability and the high quantum efficiency qualify this material for future photonic applications.

NanoBRET: The Bright Future of Proximity-Based Assays.

Bioluminescence resonance energy transfer (BRET) is a biophysical technique used to monitor proximity within live cells. BRET exploits the naturally occurring phenomenon of dipole-dipole energy transfer from a donor enzyme (luciferase) to an acceptor fluorophore following enzyme-mediated oxidation of a substrate. This results in production of a quantifiable signal that denotes proximity between proteins and/or molecules tagged with complementary luciferase and fluorophore partners. BRET assays have been used to observe an array of biological functions including ligand binding, intracellular signaling, receptor-receptor proximity, and receptor trafficking, however, BRET assays can theoretically be used to monitor the proximity of any protein or molecule for which appropriate fusion constructs and/or fluorophore conjugates can be produced. Over the years, new luciferases and approaches have been developed that have increased the potential applications for BRET assays. In particular, the development of the small, bright and stable Nanoluciferase (NanoLuc; Nluc) and its use in NanoBRET has vastly broadened the potential applications of BRET assays. These advances have exciting potential to produce new experimental methods to monitor protein-protein interactions (PPIs), protein-ligand interactions, and/or molecular proximity. In addition to NanoBRET, Nluc has also been exploited to produce NanoBiT technology, which further broadens the scope of BRET to monitor biological function when NanoBiT is combined with an acceptor. BRET has proved to be a powerful tool for monitoring proximity and interaction, and these recent advances further strengthen its utility for a range of applications.

Temperature-dependent fluorescence decay and energy transfer in Nd/Cr:YAG ceramics

This work investigates the energy-transfer processes from Cr3+ to Nd3+ in yttrium aluminum garnet (YAG) ceramics by comparing the fluorescence decay of Cr3+ for Nd/Cr:YAG with that of Cr:YAG from 293 to 473 K. The experimentally determined fluorescence decay of Nd3+ excited through Cr3+ is consistent with the theoretical predictions when energy-transfer processes are taken into account by including in the rate equations the dipole-dipole interaction and energy transfer via excitation-energy migration. Furthermore, the results presented herein clarify that the efficiency of energy transfer from Cr3+ to Nd3+ increases slightly with increasing temperature.

Dipole-Dipole Non-Radiative Energy Transfer Mediated by Surface Plasmons on a Metallic Interface

We have investigated the surface plasmon-mediated energy transfer between two optically active ions in vacuum near a metallic surface using methods of molecular quantum electrodynamics. We have studied the electric dipole-electric dipole energy transfer process only, this being the most dominant mechanism in interionic interaction between two ions in a medium when their wavefunctions do not significantly overlap. The matrix elements for energy transfer, hence energy transfer rates, are calculated using two classes of Feynman diagrams. The intermediate states for one class of diagrams do not satisfy the energy conservation principle, hence they are purely virtual states. Of particular interest are the dependencies of the energy transfer process on (1) the relative positions of the ions with respect to one another projected onto the interface and (2) the distance of each ion from the metal surface. The overall energy transfer process has been found to have both the short range and long-range components, the former being driven by virtual plasmons and the latter by the real plasmons in a non-lossy medium.

Nonradiative energy transfer and ion-ion interactions in terbium-praseodymium coactivated borate glass

A study of energy transfer between Tb3+ and Pr3+ in borate glass is being presented. From our measurement of fluorescence emission and decay times of donor (Tb3+), in the presence of different concentrations of acceptor (Pr3+), the energy transfer probability (Pda) and transfer efficiency (ɳT) have been calculated. Analyzing the data it is observed that the non-radiative energy transfer in our borate glass system occurs by dipole-dipole interactions, contrary to the observations made by Nakazawa and Shionoya (dipole-quadrupole interaction) in phosphate glass. A linear dependence of Pda versus C at low acceptor concentration suggests the migration of excitation energy among donor ions before the energy is finally transferred to the acceptor ion. At high acceptor concentrations a plot of Pdavs (C0 + C)2; where C0 is donor concentration and C is the acceptor concentration, presents a linear dependence suggesting thereby that one donor interacts with two neighbouring acceptors consistent with Fong-Diestler mechanisms of dipole-dipole energy transfer interactions.

Blue-yellow emission adjustability with aluminium incorporation for cool to warm white light generation in dysprosium doped borate glasses

A series of white light emitting Dy3+ doped lead borate (DY) and lead alumino borate (DYA) glasses have been prepared by melt quench technique and are explored by XRD, FTIR, optical absorptions, fluorescence and density measurements. In this paper an effort has been made to compare the structural changes and luminescence efficiencies of prepared glasses by changing dysprosium oxide content and glass network environment by adding aluminium oxide. The XRD profile of all the glasses confirms their amorphous nature and FTIR study shows the presence of BO3 and BO4 groups. Incorporation of Al2O3 in the glass system is responsible for a strong effect on luminescence of the present glass system. There is a strong correlation between Dy3+ ions concentration and the host glass composition on the energy transfer mechanism. The decay curves deviate gradually from single exponential function at lower concentrations to non-exponential behavior at higher concentrations. The Inokutie Hirayama (IH) model for S= 6 fits well the non-exponential decay curves that indicate dipole-dipole type energy transfer between donor and acceptor ions. The calculated chromaticity coordinates lie in the white region of CIE 1931 chromaticity diagram and are in excellent proximity with the standard equal energy white illuminant (0.333, 0.333). Furthermore, the calculated correlated color temperature and the yellow to blue (Y/B) ratio of the synthesized photonic glasses may offer the possibility of tuning the white light by varying concentration and host environment which could be useful for various photonic based device applications.

Picosecond absorption spectroscopy of self-trapped excitons and transient Ce states in LaBr3 and LaBr3 :Ce

Picosecond time-resolved optical absorption spectra induced by two-photon interband excitation of ${\mathrm{LaBr}}_{3}$ are reported. The spectra are similar in general characteristics to self-trapped exciton (STE) absorption previously measured in alkali halides and alkaline-earth halides. A broad ultraviolet absorption band results from excitation of the self-trapped hole within the STE. A series of infrared and red-visible bands results from excitation of the bound outer electron within the STE similar to bands found in alkali halides corresponding to different degrees of ``off-center'' relaxation. Induced absorption in cerium-doped ${\mathrm{LaBr}}_{3}$ after band-gap excitation of the host exhibits similar STE spectra, except it decays faster on the tens-of-picoseconds scale in proportion to the Ce concentration. This is attributed to dipole-dipole energy transfer from STE to ${\mathrm{Ce}}^{3+}$ dopant ions. The absorption spectra were also measured after direct excitation of the ${\mathrm{Ce}}^{3+}$ ions with sufficient intensity to drive two- and three-photon resonantly enhanced excitation. In this case, the spectrum attributed to STEs created adjacent to ${\mathrm{Ce}}^{3+}$ ions decays in 1 ps suggesting dipole-dipole transfer from the nearest-neighbor separation. A transient absorption band at 2.1 eV growing with Ce concentration is found and attributed to a charge-transfer excitation of the ${\mathrm{Ce}}^{3+*}$ excited state responsible for scintillation in ${\mathrm{LaBr}}_{3}$:Ce crystals. This study concludes that the energy transport from host to activator responsible for the scintillation of ${\mathrm{LaBr}}_{3}$:Ce proceeds by STE creation and dipole-dipole transfer more than by sequential trapping of holes and electrons on ${\mathrm{Ce}}^{3+}$ ions.

Photoluminescence properties and energy transfer of a single-phased white-emitting NaAlSiO4:Ce3+,Sm3+ phosphor

A series of tunable phosphors NaAlSiO4:Ce3+,Sm3+ were synthesized using a conventional high-temperature, solid-state method. Crystal structure, photoluminescence excitation, and emission spectra with fluorescence decay curves were investigated. Under UV excitation (325 nm), NaAlSiO4:Ce3+,Sm3+ showed strong blue emission located at 444 nm and orange-reddish emission centered at 563, 601, 648 and 712 nm, stemming from the characteristic emission for 4f-5d transition of Ce3+ and 4G5/2→6HJ (J=5/2, 7/2, 9/2, 11/2) transition of Sm3+, respectively. In addition, we studied the detailed energy transfer process between Ce3+ and Sm3+ and found that it belonged to dipole-dipole resonance energy transfer. Furthermore, we noted that the white light emitting from the Ce3+, Sm3+ co-doped phosphors with the color coordinate (x=0.313, y=0.283) could be observed under 325 nm excitation, which was close to the ideal white light (x=0.33, y=0.33). The results indicated that this phosphor has a potential application as a single-phased alumino-silicate phosphor for ultraviolet white light-emitting diodes (UV-WLEDs).

Enhanced luminescence at 2.7 μm of Na5Lu9F32 single crystals co-doped Er3+/Pr3+ grown by Bridgman method.

Na5Lu9F32 single crystals co-doped with 1 mol. % Er3+ and various concentrations (0.1 mol. %, 0.3 mol. %, 0.5 mol. %, 0.7 mol. %, and 1 mol. %) of Pr3+ were successfully grown using the Bridgman method. Optical spectroscopic investigations of the obtained single crystal were reported for the absorption, emission, and luminous decay. The obtained single crystal appears with almost no absorption at the 2.7 μm band, attributable to the OH- bond. According to the Judd-Ofelt (J-O) theory, the J-O intense parameters of Er3+ ions were calculated. Under the 980 nm LD pumping, an obviously enhanced emission at 2.7 μm was obtained in the Er3+/Pr3+ co-doped crystal compared with the Er3+ singly doped crystal due to the energy transfer from Er3+ to Pr3+. The most intense emission at 2.7 μm was obtained when the doping concentrations of Er3+ and Pr3+ were 1 mol. % and 0.5 mol. % in the present research. The maximum emission cross-section and gain cross-section at 2.7 μm were also estimated. Moreover, using the Dexter theory, the energy transfer microscopic parameters have been calculated, and the decay curve fitting using the Inokuti-Hirayama expression indicated the dipole-dipole energy transfer from Er3+ to Pr3+ ions.

BaZrO3 perovskite nanoparticles as emissive material for organic/inorganic hybrid light-emitting diodes

In the present work we have demonstrated double-channel emission from organic exciplexes coupled to inorganic nanoparticles. The process is demonstrated by yellow-green emission in light-emitting diodes based on organic exciplexes hybridized with perovskite-type dispersed BaZrO3 nanoparticles. Such double-channel emission provides a broadening of the electroluminescence spectrum and a resultant yellow-green emission color of the device. We have realized an energy transfer from the exciplexes arranged by the interface between two organic layers and the spherical-shaped BaZrO3 nanoparticles randomly deposited on the organic interface constructed of the tris(4-carbazoyl-9-ylphenyl)amine and 4,7-diphenyl-1,10-phenanthroline molecules. The fabricated device exhibits a current efficiency value of 3.88 C d/A, maximum brightness of 3465 cd/m2 (at 15 V), and external quantum efficiency of about 1.26%. In order to estimate the efficiency of the energy transfer from the exciplex to the BaZrO3 nanoparticles we have applied the Förster model for the dipole-dipole energy transfer accounting for the mutual overlap of the exciplex emission spectrum and the absorption spectrum of the BaZrO3 nanoparticles.

Luminescence properties of Er3+/Nd3+ co-doped Na5Lu9F32 single crystals for 2.7 μm mid-infrared laser

The enhanced 2.7 μm mid-infrared emission from the Er3+:4I11/2 → 4I13/2 transition with Nd3+ ions as the sensitizer was achieved in the Na5Lu9F32 single crystal which was successfully grown by a Bridgman method. The transmission spectrum was tested and almost no absorption of 2.7 μm band was observed. It was indicated that the content of OH- ion was very low in the crystal and it was beneficial to the 2.7 μm mid-infrared laser output. Intense 2.7 μm emissions were achieved with Nd3+ ions sensitizing Er3+ ions under the 800 nm LD pumping and the energy transfer processes between Er3+ and Nd3+ ions were analyzed. Meanwhile, the greatly decreased near infrared emission at 1.5 μm and green up-conversion emission were obtained. Additionally, the optimized concentration ratio of Er3+ to Nd3+ for efficient 2.7 μm emission was investigated in this work and the maximum emission cross section at 2.7 μm was calculated. The decay curve of 1.5 μm emission could be well fitted by Inokuti-Hirayama expression, which was strongly indicated the dipole-dipole energy transfer from Er3+ to Nd3+ ions. The results showed that Er3+/Nd3+ co-doped Na5Lu9F32 single crystal had potential applications in 2.7 μm mid-infrared laser.

Strong 1.54 μm cathodoluminescence from core-shell structures of silicon nanoparticles and erbium

We report on the development of efficient infrared-active core-shell Er2O3-Si nanoparticle architecture. Sub 3-nm H-terminated Si nanoparticles are used to reduce/deposit Er3+ ions on the nanoparticles, which in an aqueous environment simultaneously oxidize to produce the core-shells. Our results show strong cathodoluminance at 1543 nm while being able to resolve the Stark splitting. The strong luminescence afforded by the core-shell architecture in which the Si-Er interspacing drops appreciably supports a sensitive interspacing-dependent dipole-dipole energy transfer interaction model, while the hydrogenated silicon-core allows increased loading and reduced segregation of Er as in amorphous silicon material. The room temperature-wet procedure, with pre-prepared and -sorted Si nanostructures affords promising applications in electronic and optical technologies.