Resonance Energy Transfer Process Research Articles

Quantification of the resonant energy transfer processes in Er3+/Yb3+ co-doped Ca3Al2Si3O12 glasses

The resonant cross relaxation processes between Yb3+ and Er3+ ions in calcium alumino-silicate glasses have been quantified under selective Er3+ excitation. The infrared emission spectra, measured under steady state conditions (CW excitation to the 4I9/2 erbium level), have allowed to obtain an experimental relationship linking the transfer (Yb3+ → Er3+) and back transfer (Er3+ → Yb3+) parameters. These measurements combined with the dynamics of the main emitting levels, measured under pulsed excitation to the 2H11/2 erbium level, have allowed the fully quantification of the energy transfer parameters. The obtained values, C25=5.5×10−18cm3s−1 (Yb3+ → Er3+), C52=1.5×10−18cm3s−1 (Er3+ → Yb3+) and C27=7.6×10−18cm3s−1 (up-conversion mechanism, estimated from the Judd-Ofelt analysis previously reported), can be used to predict the temporal evolution of the main luminescent emission bands.

Donor–Acceptor Structure-Dependent Electrochemiluminescence Sensor for Accurate Uranium Detection in Drinking Water

As is known to all, uranium is regarded as an important hazardous element in drinking water and extremely limited by the World Health Organization. To realize the accurate monitoring of uranyl in drinking water, an efficient strategy for designing an electrochemiluminescence (ECL) sensor with a low ECL potential as well as high sensitivity and selectivity is reported in this work. In detail, a donor–acceptor type structure is built in polymer dots (Pdots) to obtain a low ECL potential and long-wavelength absorbance waves to give a resonance energy transfer process from uranyl to Pdots, which is beneficial for developing a uranyl ECL sensor with high sensitivity and selectivity. The obtained Pdots are modified with ssDNA chains to be prepared into a uranyl sensor, which gives a quite low limit of detection of 6.4 ng/L as well as excellent selectivity. Furthermore, an accurate determination is then realized in practical tap water samples. This work provides a novel strategy for designing efficient ECL sensors for trace uranyl ion monitoring in drinking water, indicating its significance in environmental and public security fields.

New Benzotriazole and Benzodithiophene-Based Conjugated Terpolymer Bearing a Fluorescein Derivative as Side-Group: In-Ternal Förster Resonance Energy Transfer to Improve Organic Solar Cells.

A new benzodithiophene and benzotriazole-based terpolymer bearing a fluorescein derivative as a side group was synthesized and studied for organic solar cell (OSC) applications. This side group was covalently bounded to the backbone through an n-hexyl chain to induce the intramolecular Förster Resonance Energy Transfer (FRET) process and thus improve the photovoltaic performance of the polymeric material. The polymer exhibited good solubility in common organic chlorinated solvents as well as thermal stability (TDT10% > 360 °C). Photophysical measurements demonstrated the occurrence of the FRET phenomenon between the lateral group and the terpolymer. The terpolymer exhibited an absorption band centered at 501 nm, an optical bandgap of 2.02 eV, and HOMO and LUMO energy levels of -5.30 eV and -3.28 eV, respectively. A preliminary study on terpolymer-based OSC devices showed a low power-conversion efficiency (PCE) but a higher performance than devices based on an analogous polymer without the fluorescein derivative. These results mean that the design presented here is a promising strategy to improve the performance of polymers used in OSCs.

Active Manipulation of Luminescent Dynamics via Au NPs‐CsPbBr3 Interfacial Engineering

AbstractManipulating photocarrier dynamics for luminescent materials is fundamentally important for steering luminescent properties of optoelectronic devices. Here, interfacial engineering is realized by constructing Au NPs‐CsPbBr3 interfaces toward resonant coupling between localized surface plasmon and exciton. Through ultrafast laser spectroscopic measurements, it is demonstrated that photoluminance originating from CsPbBr3 excitonic recombination is significantly enhanced at the interface with prolonged lifetimes. Interfacial photocarrier dynamics are mediated by plasmon‐induced hot electron transfer (PHET) and plasmon‐induced resonant energy transfer (PIRET) processes. By simply varying excitation laser wavelengths, PHET path of photocarriers is actively switched on and off. The results are of great significance for actively manipulating photocarrier dynamics of perovskite luminescent devices.

Novel Stimuli-Responsive Spiropyran-Based Switch@HOFs Materials Enable Dynamic Anticounterfeiting.

Developing smart fluorescent materials having very advanced levels, showing dynamic displays of encrypted messaging, remains a huge challenge. In this paper, we present a unique method based on combining a common photochromic molecule spiropyran (SP) with hydrogen-bonded organic frameworks (HOFs), which allows for reversible switching of SP in solid states and shows dynamic displays of encrypted information. With the irradiation time extended, the fluorescence emission undergo an evident transformation from yellow-green to orange to red, because of the fluorescence resonance energy transfer (FRET) process between the unique HOFs and merocyanine (MC) isomer. By doping with polydimethylsiloxane (PDMS), we obtained free-standing membranes with high flexibility and mechanical strength, which can be reversibly and repeatedly bent and folded at angles of >90°. Notably, the comparison of fatigue resistance between SP2/PDMS (can be used for no more than 5 times) and SP2 ⊂ HOF2/PDMS (can be used for more than 100 times) further proved the importance of HOFs. This composite system has many advantages: (1) it has diverse dynamic fluorescence emission and visible colors regulated by ultraviolet radiation with high contrast and can be reversibly converted; (2) these changes in behavior can be achieved by simple UV illumination; and (3) compared with previous work, this work not only shows the dynamic fluorescence emission, but also shows the dynamic information during the decryption.

24.3: High Efficient Persistent Luminescence from F�rster resonance Energy Transfer Processes

Metal‐free organic systems with persistent room temperature phosphorescence (pRTP) have attracted considerable attention due to their long‐lived emission (over 0.1 s) after removal of the excitation, plus their advantages of good biocompatibility and facile functionality.[1] Thus, organic pRTP materials show great potential applications in bioimaging, information storage, and optical sensing. A variety of organic pRTP materials have been developed by promoting the intersystem crossing and suppressing the non‐radiative decay as much as possible. However, their pRTP emissions were generally in the spectral region of below 600 nm, for whether crystalline phosphors or polymeric systems, let alone emission in NIR region of over 750 nm.[2]

Vibrational dynamics of the OD stretch in an atomistic simulation of HDO in H2O

An all-atom molecular dynamics (MD) simulation of dilute HDO in H2O was used to obtain vibrational frequency spectra from the classical MD trajectories and a wavelet-based method was developed to obtain the frequency-frequency correlation functions (FFCFs) of the OD stretch vibrations. Time constants were obtained on the order of 30 fs, 150–260 fs and 3.2–3.6 ps. An OD covalent bond length correlation function was calculated and a long-timescale decay constant of 1.73 ps was obtained, similar to experimental values that range from 1.45 ps to 1.8 ps. An O-O hydrogen bond length correlation function was calculated and found to exhibit an oscillation at 150 fs and a long-timescale decay time of 3.47 ps, both in good agreement with the FFCFs. Such results suggest that the spectral diffusion observed in FFCFs can be primarily attributed to fluctuations in O-O distances. An OD stretch energy correlation function was calculated, which consists of exponential decay with a time constant of 1.13 ps. The energy correlation function also exhibits two oscillations that are indicative of resonant energy transfer processes involving the OD stretch.

A 1D helical eco-friendly Mn(II) halide coordination polymer: Luminescent properties involving resonant energy transfer and magnetic characterization

In the present work, we discuss the synthesis of nontoxic Mn(II) halide coordination polymer and explore the potential light emission properties for solar-cell devises through experimental and computational studies. The crystal structure was unveiled through Single Crystal Diffraction, whereas physical properties were investigated by means of thermal, spectroscopic, magnetic, optical and photoluminescence measurements. The observed left-right handed helical structure is built up from an infinite 1-D chains of Mn(II) octahedra. The polymeric network is stabilized through inter-molecular hydrogen bonding interactions and π···π face-to-face interactions. Furthermore, ferro-antiferromagnetic ordering has been proven through magnetic measurements. A deep investigation of the photoluminescence study reveals the presence of a bright bluish light emission with corresponding CIE color coordinates of (0.27, 0.35), CCT value of 8092 K and a very high CRI value of 96. The origin of this intense light emission is mainly attributed to the occurrence of the resonant energy and charge transfer processes between Triazolate ligand and inorganic Mn–Cl sub-lattices. Such behavior leads to the conversion of Frenkel excitons localized within the organic part to Mott-Wannier excitons localized in inorganic clusters. Based on these results, we strongly believe that the elaborated material can be a promising candidate for eco-friendly electronic applications.

Multi-stimuli responsive fluorescence switching behaviours of AIE polymers for acid-base vapour sensing and highly sensitive ferric ion detection

Novel aggregation-induced emission (AIE) polymers, i.e., P1-SP and P2-SP, consisting of AIEgenic tetraphenylethylene (TPE) and photochromic spiropyran (SP) units are reported. Both P1-SP and P2-SP exhibit excellent AIE behaviours of TPE moieties in near-aqueous solutions THF/H2O (95% water) and solid states with strong cyan and blue emissions at 494 and 477 nm, respectively. Upon acidification, the close forms of P1-SP and P2-SP can be opened and switched to open P1-MCH+ and P2-MCH+ structures of protonated merocyanine (MCH+), resulting in fluorescence quenching of TPE units through corresponding intramolecular charge transfer (ICT) and Förster resonance energy transfer (FRET) processes. The fluorescence recovery of TPE can be monitored by the neutralization of P1-MCH+ and P2-MCH+ with base solutions under ambient/visible light attributed to the re-close P1-SP and P2-SP structures, which led to respective turn-off ICT and FRET phenomena. Distinct fluorescence quenching behaviours of P1-SP and P2-SP can be observed under various stimuli, including acid conditions and ferric ion interactions, which are also confirmed by theoretical studies. Moreover, P1-SP and P2-SP can be utilized as fluorescence quenching sensors for nanomolar level detections of ferric ion (LOD = 166 and 110 nM for corresponding P1-SP and P2-SP) with excellent selectivities in near-aqueous solutions and paper test strips. Additionally, the interesting visible and fluorescence colour changes of coated cellulosic papers, blended PMMA films and powder forms based on P1-SP and P2-SP under multi-external stimuli (acid-base vapour and visible light/heating processes) are also explored in this report.

Low-threshold and narrow-emission random lasing in a self-assembly TiN nanoparticle-doped carbon quantum dot/DCM nanowire composite

The random lasing in quantum dot systems is in anticipation for widespread applications in biomedical therapy and image recognition, especially in random laser devices with high brightness and high monochromaticity. Herein, low-threshold, narrowband emission, and stable random lasing is realized in carbon quantum dot (CQD)/DCM nanowire composite-doped TiN nanoparticles, which are fabricated by the mixture of carbon quantum dots and self-assembly DCM dye molecules. The Förster resonance energy transfer process results in a high luminescence efficiency for the composite of carbon dots and DCM nanowires, allowing significant random lasing actions to emerge in CQD/DCM composite as TiN particles are doped that greatly enhance the emission efficiency through the plasmon resonance and random scattering. Thus, sharp and low-threshold random lasing is finally realized and even strong single-mode lasing occurs under higher pumping energy in the TiN-doped CQD/DCM composite. This work provides a promising way in high monochromaticity random laser applications.

Highly Selective and Sensitive Ratiometric Detection of Sn2+ Ions Using NIR-Excited Rhodamine-B-Linked Upconversion Nanophosphors

Detection of Sn2+ ions in environmental and biological samples is essential owing to the toxicological risk posed by excess use tin worldwide. Herein, we have designed a nanoprobe involving upconversion nanophosphors linked with a rhodamine-based fluorophore, which is selectively sensitive to the presence of Sn2+ ions. Upon excitation with near-infrared (NIR) light, the green emission of the nanophosphor is reabsorbed by the fluorophore with an efficiency that varies directly with the concentration of the Sn2+ ions. We have explored this NIR-excited fluorescence resonance energy transfer (FRET) process for the quantitative and ratiometric detection of Sn2+ ions in an aqueous phase. We have observed an excellent linear correlation between the ratiometric emission signal variation and the Sn2+ ion concentration in the lower micromolar range. The detection limit of Sn2+ ions observed using our FRET-based nanoprobe is about 10 times lower than that observed using other colorimetric or fluorescence-based techniques. Due to the minimal autofluorescence and great penetration depth of NIR light, this method is ideally suited for the selective and ultrasensitive detection of Sn2+ ions in complex biological or environmental samples.

The cyclotriphosphazene-based covalent organic frameworks constructed entirely by flexible building blocks for adsorping and fluorescence sensing iodine

A series of flexible cyclotriphosphazene-based COFs, we call them fully flexible cyclotriphosphazene-based COFs (HDADE, HBAPB and HBPDA), were prepared by means of reversible Schiff base polycondensation reactions for the first time, which were constructed entirely by flexible building blocks, not only hexa(4-formyl-phenoxy)cyclotriphosphazene (NOP–6–CHO) as a flexible knot but also aromatic ether diamine as flexible linkers. The fully flexible cyclotriphosphazene-based COFs are crystalline porous materials. Their crystallinity and BET specific surface areas increase with the length of the linkers, and are higher than that of the corresponding COFs constructed by the rigid linkers. HDADE, HBAPB and HBPDA can absorb iodine in both gas or liquid phase. The adsorptive capacities are 5.22, 4.55, and 3.86 g g−1, respectively, which are higher than the corresponding COFs formed by rigid linkers. The fully flexible cyclotriphosphazene-based COFs can fluorescently sense iodine with high sensitivity. Their quenching constants (KSV) are 2.22 × 104, 7.07 × 104, and 1.04 × 104 L mol−1. Their LODs are 1.35 × 10−10, 4.24 × 10−11, and 2.88 × 10−10 mol L−1, respectively. The fluorescence quenching of iodine to the fully flexible cyclotriphosphazene-based COFs has both photo-induced charge transfer and resonant energy transfer processes.

Rational Design of NIR-II AIEgens with Ultrahigh Quantum Yields for Photo- and Chemiluminescence Imaging.

Fluorescence imaging in the second near-infrared window (NIR-II, 1000-1700 nm) using small-molecule dyes has high potential for clinical use. However, many NIR-II dyes suffer from the emission quenching effect and extremely low quantum yields (QYs) in the practical usage forms. The AIE strategy has been successfully utilized to develop NIR-II dyes with donor-acceptor (D-A) structures with acceptable QYs in the aggregate state, but there is still large room for QY improvement. Here, we rationally designed a NIR-II emissive dye named TPE-BBT and its derivative (TPEO-BBT) by changing the electron-donating triphenylamine unit to tetraphenylethylene (TPE). Their nanoparticles exhibited ultrahigh relative QYs of 31.5% and 23.9% in water, respectively. By using an integrating sphere, the absolute QY of TPE-BBT nanoparticles was measured to be 1.8% in water. Its crystals showed an absolute QY of 10.4%, which is the highest value among organic small molecules reported so far. The optimized D-A interaction and the higher rigidity of TPE-BBT in the aggregate state are believed to be the two key factors for its ultrahigh QY. Finally, we utilized TPE-BBT for NIR-II photoluminescence (PL) and chemiluminescence (CL) bioimaging through successive CL resonance energy transfer and Förster resonance energy transfer processes. The ultrahigh QY of TPE-BBT realized an excellent PL imaging quality in mouse blood vessels and an excellent CL imaging quality in the local arthrosis inflammation in mice with a high signal-to-background ratio of 130. Thus, the design strategy presented here brings new possibilities for the development of bright NIR-II dyes and NIR-II bioimaging technologies.

Synthesis, TD-DFT, and optical properties study of a chromeno-quinoline (acceptor) and mirror-less laser action enabled by energy transfer from a conjugated-polymer (Donor)

Structurally interesting chromeno-quinolines were constructed via the cyclization reaction of O-propargylated naphthaldehyde and substituted anilines in good yields. We explored compound methyl-chromenoquinoline (MCQ) in detail for its optical properties using Time-dependent density-functional theory (TD-DFT) and experimental studies. The conjugated-polymer (CP) Poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-(2,5-p-xylene)] or [(ADS145UV or PFOPX)] was studied as donor. The TD-DFT implied that MCQ is a fluorescent compound with well-defined highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) structure at −5.327 eV and −1.836 eV, respectively, with an energy gap of 3.49 eV in toluene captivity. The TD-DFT-based model and experimental study showed an energy gap of 3.326 eV and 3.351 eV, respectively, and the deviation was 0.025 eV. The experimental studies of MCQ showed solvent-dependent fluorescence peak shifted from 445 ± 2 nm to 538 ± 2 nm for dielectric constant ranging from 0.01 (hexane) to 10.2 (water). Despite the good optical properties, MCQ produced a weak laser-induced fluorescence (LIF) and not produce amplified spontaneous emission (ASE) to any pump energy of 3rd harmonic from Nd:YAG laser (5 ns, 355 nm). When PFOPX of concentration 500 nM (500 μL) was added to MCQ of 506 mM (3.5 mL) concentration, the LIF suddenly improved tenfold due to efficient Fluorescence resonance energy transfer (FRET) process. At the optimal concentration of PFOPX (670 nM) in MCQ solution, the spectrum changed dramatically. The spectrum has five peaks with a LIF in the background, where peaks around 393.5 nm and 417.3 nm attribute to the oligomer; 438.7 nm attributed to a combined fluorescence of PFOPX and MCQ; 466.4 nm, and 493.1 nm corresponding to MCQ. Analysis shows that the peaks at 440 nm (partly) and 493 nm were ASE from MCQ.

An upconversion biosensor based on DNA hybridization and DNA-templated silver nanoclusters for the determination of acrylamide

Acrylamide is widely present in many fried and baked foods, that has been proved as potentially carcinogenic to humans. In this work, a novel biosensor using core-shell upconversion nanoparticles (CSUCNPs) with aptamer as recognized element was designed for the determination of acrylamide. The principle of this work was based on the fluorescence resonance energy transfer (FRET) process from CSUCNPs to silver nanoclusters (AgNCs). Whereas the binding between acrylamide and the aptamer disturbed the DNA structure and inhibited the synthesis of AgNCs, which induced a higher fluorescence intensity. Under the optimal conditions, a low limit of detection (LOD) was calculated as 1.13 nM in the range of 1–105 nM. This biosensor was further applied in the spiked food samples to validate the applicability that recoveries were at the range of 78.52–117.09% with a relative standard deviation of 1.54–10.46%. The approach was compared with the standard HPLC method in great agreement (P ＞ 0.05).

Selective sensing of explosive nitrophenol compounds by using hydrophobic carbon nanoparticles

Nitroaromatic compounds (NACs) have been polluting the soil and groundwater via anthropogenic activities. Due to their well-known explosive and toxic nature, their selective-sensitive detection specifically 2,4,6-trinitrophenol (TNP) and 2,4-dinitrophenol (DNP) become essential. Herein, hydrophobic carbon nanoparticles (HCNPs) have been synthesized by a single-step and simple methodology by refluxing maleic acid in the presence of oleylamine. The as-synthesized HCNPs possess a spherical shape with a diameter of 60 ± 5 nm and is insoluble in an aqueous medium but soluble in non-aqueous solvents. HCNPs show brightly blue emission at ∼464 nm with ∼24% quantum yield. The fluorescence property of HCNPs is applied towards the selective sensing of NACs. The fluorescence intensities of HCNPs have been significantly quenched selectively only after the addition of TNP and DNP from the tested many NACs. The detection limit of HCNPs for TNP and DNP is low as ∼242 nM and ∼276 nM, respectively. Concerning the plausible mechanism of selective fluorescence-based detection, TNP/DNP molecules interact with HCNPs, which involves the dynamic quenching behavior with both the Förster resonance energy transfer (FRET) and photo-induced electron transfer (PET) process.

Blue Phosphorescence and Hyperluminescence Generated from Imidazo[4,5-b]pyridin-2-ylidene-Based Iridium(III) Phosphors.

Four isomeric, homoleptic iridium(III) metal complexes bearing 5‐(trifluoromethyl)imidazo[4,5‐b]pyridin‐2‐ylidene and 6‐(trifluoromethyl)imidazo[4,5‐b]pyridin‐2‐ylidene‐based cyclometalating chelates are successfully synthesized. The meridional isomers can be converted to facial isomers through acid induced isomerization. The m‐isomers display a relatively broadened and red‐shifted emission, while f‐isomers exhibit narrowed blue emission band, together with higher photoluminescent quantum yields and reduced radiative lifetime relative to the mer‐counterparts. Maximum external quantum efficiencies of 13.5% and 22.8% are achieved for the electrophosphorescent devices based on f‐tpb1 and m‐tpb1 as dopant emitter together with CIE coordinates of (0.15, 0.23) and (0.22, 0.45), respectively. By using f‐tpb1 as the sensitizing phosphor and t‐DABNA as thermally activated delayed fluorescence (TADF) terminal emitter, hyperluminescent OLEDs are successfully fabricated, giving high efficiency of 29.6%, full width at half maximum (FWHM) of 30 nm, and CIE coordinates of (0.13, 0.11), confirming the efficient Förster resonance energy transfer (FRET) process.

Enhanced Resonant Energy Transfer by Decorating Au Nanoparticles on the Sidewalls of InGaN Multiple‐Quantum‐Well Nanorods

An enhanced resonant energy transfer (RET) process between green InGaN multiple quantum wells (MQWs) and CdSe/ZnS quantum dots (QDs) is investigated by decorating the sidewalls of InGaN MQW nanorods with Au nanoparticles. The InGaN MQW nanorods are shallow‐etched to the region of InGaN MQWs or deep‐etched through InGaN MQWs completely. The Au nanoparticles can provide localized surface plasmon coupling to both InGaN MQWs and QDs, leading to accelerated decay rates. The localized surface plasmons also enhance the RET process between InGaN MQWs and QDs. Compared to the bare nanorods without Au nanoparticles, the enhancement factors of the RET process are 1.8 and 5.6 for shallow‐ and deep‐etched MQW nanorods, respectively. The larger enhancement factor for deep‐etched nanorods is mainly attributed to the weaker localized surface plasmon coupling with InGaN MQWs, which is proposed to compete with the RET process. The RET efficiency in the deep‐etched InGaN MQW nanorods is calculated as 62%, demonstrating high potential for usage in energy conversion devices.

Superbly long lifetime over 13,000 h for multiple energy transfer channels in deep blue phosphorescence organic light-emitting diodes with Ir complex under CIEy of 0.17

Despite over two decades of relentless endeavor, the industrial application of blue phosphorescent organic light-emitting diodes (PhOLEDs) has not been realized due to extremely short lifetime. The degradation of PhOLEDs is generally accelerated at high current levels since high triplet energy with long exciton lifetime are mostly concentrated on host molecules and transferred to dopant via slow Dexter energy transfer (DET) processes rather than fast Förster resonance energy transfer (FRET) processes. Herein, we propose a novel device architecture that creates multiple energy transfer channels by employing an Ir-complex intermediate energy carrier (IEC). Unlike exciplex or electroplex, no excitons were generated between the host and the IEC even though the IEC also behaves as a p-type host. The most crucial role of the IEC is to diversify the energy transfer channels. By introducing the IEC in deep blue PhOLEDs, both FRET and DET channels were additionally created between the IEC and the host, and the IEC and the dopant. Consequently, an unprecedentedly long half luminance lifetime of 13,830 h at an initial luminance of 100 cd/m2 was obtained with a high efficiency of 14.4% and CIEy = 0.17. To our best knowledge, the lifetime in our report is the longest with a deep blue phosphorescent Ir complex.

Spectral analysis on the acceptor concentration-dependent fluorescence resonance energy transfer process in CuInS2@ZnS-SQ complexes.

Owing to the broad spectral response and flexible choices of donors and acceptors, fluorescence resonance energy transfer (FRET) system based on quantum dots (QDs) is a potential candidate for enhancing performance of solar cells and other optoelectronic devices. Thus it is necessary to develop such FRET systems with high efficiency and understand the involved photophysical dynamics. Here, with type I CuInS2@ZnS core-shell quantum dots as the energy donor, series of CuInS2@ZnS-SQ complexes are synthesized by adjusting the acceptor (squaric acid, SQ) concentration. The FRET dynamics of the samples is systematically investigated by virtue of steady-state emission, time-resolved fluorescence decay, and transient absorption measurements. The experimental results display a positive correlation between the energy transfer efficient (η). The best energy transfer efficient achieved from experimental data is 52%. This work provides better understanding of the photophysical dynamics in similar complexes and facilitates further development of new photoelectronic devices based on relevant FRET systems.