Intramolecular Energy Transfer Research Articles

Quantum–Chemical Study of the Photophysical Behavior of Mesogenic Europium(III) Complexes with β‐Diketones and Lewis Bases

AbstractMetal‐containing liquid crystals such as Ln(III) complexes possess unique structural, liquid‐crystalline (LC), optical, and magnetic properties and represent modern cutting‐edge multifunctional materials. Application of mesogenic Ln(III) complexes is hindered by their nontrivial structure–property relationships. These relationships, in turn, depend on various factors, including insufficiently studied physicochemical processes. Although a proper Ln(III) element and the respective ligand environment are selected prior to synthesis of such complexes, the structural features of the coordination polyhedra, especially upon photoexcitation, are not uniquely defined. Therefore, this work focuses on the development of theoretical approaches to creating multifunctional materials represented by highly luminescent mesogenic Eu(III) complexes with β‐diketones and Lewis bases. The relationships between their structure, the parameters of Voronoi–Dirichlet polyhedra, the luminescence efficiency, and the LC properties were considered. The calculated excited states and intramolecular energy transfer rates were used to determine intramolecular energy transfer channels. The LC behavior of the studied materials was shown to mainly depend on the ligand environment, whereas their optical properties were found to be mostly governed by the coordination polyhedra.

Full Picture of Energy Transfer in a Trivalent Europium Complex with Bidentate β-Diketonate Ligand.

Trivalent europium (Eu(III)) complexes emit narrow-band luminescence as a result of energy transfer following the photoexcitation of antenna ligands. Bidentate β-diketonates are typically used as antenna ligands; however, their entire energy transfer mechanism to Eu(III) remains unknown. We used time-resolved photoluminescence spectroscopy and femtosecond transient absorption spectroscopy to map the complete intramolecular energy transfer process in the [Eu(hfa)3(TPPO)2] (hfa = hexafluoroacetylacetonate, TPPO = triphenylphosphine oxide) complex; hfa is a β-diketonate antenna ligand. Our analysis provides a "full picture" of energy transfer, tracing each step from initial photoexcitation to final relaxation: intersystem crossing in the ligands, energy transfer from the ligands to the metal center, and multiple internal conversion of Eu(III). We demonstrated that the direct bonds of the bidentate ligands enabled a quick and near-unity-efficiency energy transfer from the triplet state of the ligand to the 5D2 state of Eu(III). We also revealed that the loss of the ligand-centered intersystem crossing process reduces the overall sensitization efficiency. Our findings provide a foundation for the rational design of advanced luminescent materials, paving the way for advances in lanthanide-based luminescence research.

Multiple Energy Transfer Modes From o‐Carborane Dyad Induced by Synergetic Conformational Regulations and Intense Circularly Polarized Luminescence in Self‐Assembly Aggregates

AbstractPhotothermal modulated excited conformations in traditional optoelectronic materials have been extensively investigated for the manipulation of emissive properties. However, photoinduced molecular synergetic conformational changes, which are promising for controlling intramolecular energy transfer modes through molecular orbital breaking, are never been explored. Herein, a novel o‐carborane dyad composed of carbazole units as electron donors and triazine derivatives as electron acceptors is demonstrated to achieve conformation‐dependent emissions and abundant emissions via synergetic conformational changes. Notably, the resulting dyad exhibited multiple conformational changes that induced emissions through different energy transfer modes involved “through space” and “through bond.” Exactly, the electron spin from singlet to triplet state took a flip accompanied by molecular orbitals from π–π molecular orbitals in the space charge transfer style to π and σ molecular orbitals in the bond charge transfer mode. The circularly polarized luminescence (CPL) properties are systematically investigated, exhibiting intense CPL with large glum values. These results provide novel perspectives for elucidating the complicated emission changes in aggregated states, as well as unique perspectives on the relationship between molecular conformations, energy transfer modes, and molecular orbital breaking.

Triad photosensitizers based on iodo-aza-Bodipy and naphthalenediimides (NDI) with broadband absorption: Study of resonance energy transfer and electron transfer

Two organic photosensitizers based on resonance energy transfer (A-1 and A-2) are prepared. Naphthalenediimides was used as intramolecular energy donor and iodo-aza-Bodipy was used as intramolecular energy acceptor/spin converter. A-1(ε = 42800 at 618 nm and ε = 59600 at 674 nm) and A-2 (ε = 33300 at 514 nm and ε = 68300 at 674 nm) give the two strong absorption band and both of them show broadband absorption in visible region. The photophysical properties of the compounds were studied with steady state and time-resolved spectroscopy in detail. With steady state and time-resolved spectroscopy, we found that photoexcitation into the energy donor was followed by singlet energy transfer, then via the intersystem crossing (ISC) of the energy acceptor. By nanosecond time-resolved transient absorption spectroscopy and DFT calculation, triplet excited state is localized on the iodo-aza-Bodipy moiety. Quantum yield of singlet oxygen of A-1 and A-2 is 39.7% and 40.9 %, respectively. Based on fluorescence lifetime quenching, the efficiency of intramolecular energy transfer is estimated to be 15.9% and 27.7% for A-1 and A-2. And PET is responsible for the relatively low efficiency, which is identified by the calculation of kcs / kFRET and the Gibbs free energy change(△G0cs). A-1 and A-2 were used for singlet oxygen (1O2) mediated photooxidation of 1,5-dihydroxylnaphthalene and the photosensitizing ability are more efficient than the triplet photosensitizers with the mono-chromophore photosensitizer.

Comparative analysis of the interaction mechanism of γ-globulin and hemoglobin with spherical and rod-shaped gold nanoparticles

The interaction mechanism of spherical gold nanoparticles (AuNPs) and rod-shaped gold nanoparticles (AuNRs) with γ-globulin and hemoglobin was comprehensively and comparatively analyzed. γ-Globulin and hemoglobin have high affinity with AuNPs, and with two different types of binding sites on AuNRs surface. Except hemoglobin interaction with the first binding site of AuNRs, the interaction between γ-globulin/hemoglobin and AuNPs/AuNRs is the spontaneous, endothermic and entropy-driven process, and hydrophobic interaction plays a dominant role. The molecular adsorption mechanism of γ-globulin/hemoglobin on AuNPs and AuNRs surface conforms to Langmuir model and Freundlich model, respectively. The kinetic molecular mechanism between them conforms to the pseudo-second-order model, and chemisorption is the rate-limiting step. AuNPs result in the loosening and unfolding of γ-globulin backbone. AuNRs have no significant effect on γ-globulin backbone. AuNPs/AuNRs result in no significant changes in hemoglobin structure and heme group microenvironment. AuNPs/AuNRs decrease the hydrophobicity of Trp microenvironment of γ-globulin, but there is an intramolecular energy transfer from Trp residue to Tyr residue of hemoglobin. The β-sheet of γ-globulin and the α-helix of hemoglobin reduce by increasing concentrations of AuNPs/AuNRs. Molecular docking is suggesting that the specific amino acid residues of γ-globulin and hemoglobin interaction with AuNPs/AuNRs, and validates the experimental results.

Designing Semiconducting Polymer Dots for High-Efficiency CO2 Photoreduction Using the Intramolecular Energy Transfer Strategy

Designing Semiconducting Polymer Dots for High-Efficiency CO₂ Photoreduction Using the Intramolecular Energy Transfer Strategy

Maximizing Nanoscale Downshifting Energy Transfer in a Metallosupramolecular Cr(III)-Er(III) Assembly.

Pseudo-octahedral CrIIIN6 chromophores hold a unique appeal for low-energy sensitization of NIR lanthanide luminescence due to their exceptionally long-lived spin-flip excited states. This allure persists despite the obstacles and complexities involved in integrating both elements into a metallosupramolecular assembly. In this work, we have designed a structurally optimized heteroleptic CrIII building block capable of binding rare earths. Following a complex-as-ligand synthetic strategy, two heterometallic supramolecular assemblies, in which three peripherical CrIII sensitizers coordinated through a molecular wire to a central ErIII or YIII, have been prepared. Upon excitation of the CrIII spin-flip states, the downshifted Er(4I13/2 → 4I15/2) emission at 1550 nm was induced through intramolecular energy transfer. Time-resolved experiments at room temperature reveal a CrIII → ErIII energy transfer of 62-73% efficiencies with rate constants of about 8.5 × 105 s-1 despite the long donor-acceptor distance (circa 14 Å). This efficient directional intermetallic energy transfer can be rationalized using the Dexter formalism, which is promoted by a rigid linear electron-rich alkyne bridge that acts as a molecular wire connecting the CrIII and ErIII ions.

Intramolecular energy transfer and its influence on the overall quantum yields of Eu3+ and Tb3+ chelates with dimethyl(phenylsulfonyl)amidophosphate ligands

Lanthanide chelates with dimethyl(phenylsulfonyl)amidophosphate (labeled as HSP) and Lewis base ligands (bpy = 2,2;-bipyridine and phen = 1,10-phenanthroline) of formula Na[Ln(SP)4] (1Ln), [Ln(SP)3bpy] (2Ln); [Ln(SP)3phen] (3Ln) (Ln = Eu3+, Gd3+, Tb3+ and Lu3+) were obtained and characterized by the X-ray, photoluminescence spectroscopy at 293 and 77 K as well as by intrinsic (QLnLn) and overall (QLnL) luminescence quantum yields. These phosphors manifest a very strong emission after excitation in the UV range of the molecular singlet states (S1) and two of them have very high QLnL values (Eu3+ and Tb3+ chelates of the type 2Ln and 3Ln). The dynamics of the excited states are discussed based on the intramolecular energy transfer theory, considering the dipole–dipole, the dipole-multipole and the exchange mechanisms. From the calculated energy transfer rates, a rate equation model was constructed and, thus, the theoretical QLnL can be obtained. A good correlation between the experimentally determined and theoretically calculated QLnL values was achieved, with the triplet state (T1) playing a predominant role in the energy transfer process for Eu3+ compounds, while the sensitization for Tb3+ compounds is dominated by the energy transfer rates from the singlet state (S1).

Europium‐Based Metal–Organic Framework with N─H···π Interaction and Intramolecular Energy Transfer Mechanisms for Self‐Electrochemiluminescence

AbstractThis work proposes a europium‐based metal–organic framework ([Eu2(HNCP)4Cl4(H2O)2]n, named ZL‐1), featuring dinuclear Eu2(COO)2 clusters as connecting nodes, linked by benzimidazolyl tridentate ligand 2‐(4‐carboxyphenyl)‐imidazo[4,5‐f]‐1,10‐phenanthroline (HNCP) for efficient self‐electrochemiluminescence (self‐ECL). The cathodic ECL emission shows two peaks with a maximum intensity of 7500 a.u.at 0 ∼ −1.8 V in pH 9.0 phosphated buffered solution (PBS) without extra coreactant. The cleavage of N─H bond in benzimidazolyl group can occur under alkaline conditions to generate neutral radical ZL‐1•. After applying voltage, the ZL‐1 can be reduced twice to form ZL‐1Re1•− and ZL‐1Re2•−. Then, ZL‐1Re1•− and ZL‐1Re2•− react with ZL‐1•, accompanied by transferring energy from HNCP to central Eu3+ to produce excited ZL‐1Re1* and ZL‐1Re2* for ECL1 and ECL2 emissions. The local excitation in the HNCP unit is demonstrated with cyclic voltammetry (CV) and stepping pulse ECL. The stimulated and luminous species are confirmed by density functional theory calculations and ECL spectra. This design approach of self‐ECL materials, which coordinated functional ligands with lanthanide metal ions as 3D‐structured MOF, broadened the applications of ECL systems to loose conditions and facilitated mechanistic exploration of ECL processes.

A coumarin-naphthalimide-based ratiometric fluorescent probe for nitroxyl (HNO) based on an ICT-FRET mechanism

Nitroxyl (HNO) is an important reactive nitrogen that is associated with various states in physiology and pathology and plays a unique function in living systems. So, it is important to exploit fluorescent probes with high sensitivity and selectivity for sensing HNO. In this paper, a novel ratiometric fluorescent probe for HNO was developed utilizing intramolecular charge transfer (ICT) and fluorescence resonance energy transfer (FRET) mechanisms. The probe selected coumarin as energy donor, naphthalimide as energy receptor and 2-(diphenylphosphino)benzoate as the sensing site for detecting HNO. When HNO was not present, the 2-(diphenylphosphino)benzoate unit of the probe restricted electron transfer and the ICT process could not occur, leading to the inhibition of FRET process as well. Thus, in the absence of HNO the probe displayed the intrinsic blue fluorescence of coumarin. When HNO was added, the HNO reacted with the 2-(diphenylphosphino)benzoate unit of the probe to yield a hydroxyl group which resulting in the opening of ICT process and the occurring of FRET process. Thus, after providing HNO the probe displayed yellow fluorescence. In addition, the probe showed good linearity in the ratio of fluorescence intensity at 545 nm and 472 nm (I545 nm/I472 nm) with a concentration of HNO (0.1–20 μM). The probe processed a detection limit of 0.014 μM and a response time of 4 min. The probe also specifically identified HNO over a wide pH scope (pH = 4.00–10.00), including physiological conditions. Cellular experiments had shown that this fluorescent probe was virtually non-cytotoxic and could be applied for ratiometric sensing of HNO in A549 cells.

Optical Amplification at 1.5µm in ErIII Coordination Polymer-Doped Waveguides Based on Intramolecular Energy Transfer.

9,9-bis (diphenylphosphorylphenyl) fluorene (FDPO) and dibenzotetrathienoacene (DBTTA), are synthesized as the neutral and anionic ligands, respectively, to prepare the ErIII coordination polymer [Er(DBTTA)3(FDPO)]n. Based on the intramolecular energy transfer, optical gains at 1.5µm are demonstrated in [Er(DBTTA)3(FDPO)]n-doped polymer waveguides under excitations of low-power light-emitting diodes (LEDs) instead of laser pumping. A ligand-sensitization scheme between organic ligands and Er3+ ions under an excitation of an ultraviolet (UV) LED is established. Relative gains of 10.5 and 8.5dBcm-1 are achieved at 1.53 and 1.55µm, respectively, on a 1-cm-long SU-8 channel waveguide with a cross-section of 2×3µm2 and a 1.5-µm-thick [Er(DBTTA)3(FDPO)]n-doped polymethylmethacrylate (PMMA) as upper cladding. The ErIII coordination polymer [Er(DBTTA)3(FDPO)]n can be conveniently integrated with various low-loss inorganic waveguides to compensate for optical losses in the C-band window. Moreover, by relying on the intramolecular energy transfer and UV LED top-pumping technology, it is easy to achieve coupling packaging of erbium-doped waveguide amplifiers (EDWAs) with pump sources in planar photonic integrated chips, effectively reducing the commercial costs.

The effect of the outer-sphere cations on the photophysical and magnetic properties of rare earth complexes with 2,2,2-trichloro-N-(diphenylphosphoryl)acetamide

Two series of rare earth coordination compounds have been synthesized (Na[RE(L4)] (labeled as 1RE) and PPh4[RE(L4)] (labeled as 2RE), where RE = Y3+, Eu3+, Tb3+, L = 2,2,2-trichloro-N-(diphenylphosphoryl)acetamide) to determine the possibility of modifying their photophysical and magnetical properties by changing the counterion. The crystal structure of 1RE was determined based on the single-crystal X-ray diffraction and the crystal structure of 2RE was determined based on quantum chemistry computational procedures. Characterization of the physicochemical properties of the compounds was carried out using differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), 1H and 31P NMR spectroscopy as well as FT-IR, absorption and luminescence spectroscopy in the temperature range of 300 - 77 K. The rate constants of radiative (Arad) and non-radiative (Anrad) transitions, intrinsic (QLnLn) and overall (QLnL) emission quantum yields, sensitization efficiency (ηsens), the experimental and theoretical intensity parameters (Ωλ), the forward (WS, WT) and backward (WbS, WbT) intramolecular energy transfer (IET) rates were determined. Magnetic properties of Tb3+ compounds were studied in a constant field of 0.5 T in the temperature range of 1.8–300 K. Dynamic AC magnetic susceptibility measurements were carried out as a function of temperature and frequency for 1Tb and 2Tb. Only in the case of 2Tb, in the presence of an external DC field, a slight temperature dependence of in-phase χ′ and out-of-phase χ'' susceptibility was recorded. Based on experimental and theoretical results, the significant effect of counterion on the photophysical and magnetic properties of RE chelates has been demonstrated and clarified, providing valuable guidance for the design of bifunctional electromagnetic radiation converters.

Demonstration of Optical Gain at 1535 nm Based on ErIII Complex‐Doped Polymer Waveguides Under Light‐Emitting Diode Excitation

AbstractA near‐infrared luminescent complex Er(DBTTA)3(DBFDPO) [where DBTTA = dibenzotetrathienoacene; DBFDPO = 4,6‐bis (diphenylphosphoryl) dibenzofuran] is synthesized. Based on the intramolecular energy transfer between organic ligands and Er3+ ions, optical gains at 1535 nm are demonstrated in Er(DBTTA)3(DBFDPO)‐doped polymer waveguides under the excitation of light‐emitting diodes (LEDs) instead of laser pumping. Relative gains of 6.4, 8.2, and 10.6 dB are obtained in 1 cm long waveguides with cross‐sectional dimensions of 6 × 4, 4 × 4, and 2 × 3 µm2 respectively, using the vertical top‐pumping mode of a 365 nm LED with 462 mW. Incorporating an ≈100 nm thick aluminum reflector grown under the lower cladding, enhanced the optical gain to 11.6 dB cm−1 in a waveguide with a cross‐section of 4 × 4 µm2, and an internal gain of ≈7.4 dB cm−1 is achieved. By relying on the intramolecular energy transfer and LED top‐pumping technology, the upconversion luminescence of Er3+ ions and thermal damage to polymer waveguides caused by the high power density of laser pumping can be effectively reduced. The complex Er(DBTTA)3(DBFDPO)‐doped polymer can be spin‐coated on different types of waveguides to compensate for optical losses at 1.5 µm and is expected to have a critical role in planar photonic integration.

Supramolecular assembly activated single-molecule phosphorescence resonance energy transfer for near-infrared targeted cell imaging

Pure organic phosphorescence resonance energy transfer is a research hotspot. Herein, a single-molecule phosphorescence resonance energy transfer system with a large Stokes shift of 367 nm and near-infrared emission is constructed by guest molecule alkyl-bridged methoxy-tetraphenylethylene-phenylpyridines derivative, cucurbit[n]uril (n = 7, 8) and β-cyclodextrin modified hyaluronic acid. The high binding affinity of cucurbituril to guest molecules in various stoichiometric ratios not only regulates the topological morphology of supramolecular assembly but also induces different phosphorescence emissions. Varying from the spherical nanoparticles and nanorods for binary assemblies, three-dimensional nanoplate is obtained by the ternary co-assembly of guest with cucurbit[7]uril/cucurbit[8]uril, accompanying enhanced phosphorescence at 540 nm. Uncommonly, the secondary assembly of β-cyclodextrin modified hyaluronic acid and ternary assembly activates a single intramolecular phosphorescence resonance energy transfer process derived from phenyl pyridines unit to methoxy-tetraphenylethylene function group, enabling a near-infrared delayed fluorescence at 700 nm, which ultimately applied to mitochondrial targeted imaging for cancer cells.

Interplay between Theory and Photophysical Characterization in Symmetric α-Substituted Thienyl BODIPY Molecule.

4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY)-based molecules have emerged as interesting materials for optoelectronic applications due to the possibility to easily fine-tune their photophysical and optical properties, dominated by two main absorption bands in the visible range. However, no studies have been reported on the nature of these spectral features. By means of ultrafast spectroscopy, we detect intramolecular energy transfer in a spin-coated film of di-thieno-phenyl BODIPY (DTPBDP) dispersed in a polystyrene matrix after pumping the high-energy absorption band. The same effect is not present upon pumping the lowest-energy band, which instead allows the achievement of efficient amplified spontaneous emission. Density functional calculations indicate the different nature of the two main absorption bands, explaining their different photophysical behavior.

Non-conventional exciplex system by leveraging zero-radius of intramolecular energy transfer mechanism: Seamless integration of p-host and fluorescent dopant for highly efficient OLEDs

A multi-component emissive layer (EML) composed of a mixture of p- and n-type hosts and a dopant is a widely used structure in organic light-emitting diodes (OLEDs) due to its high efficiency and operational stability. However, multi-component EML devices impose limitations such as difficulty in accurately controlling the mixing ratio and profiles in the manufacturing process, high costs, and complexity in the photophysical properties of the components.In this paper, a p-type host fused with a blue fluorescent dopant, 5,9-di([1,1′-biphenyl]-2-yl)-2′-(9H-carbazole-9-yl)3,7-dimethyl-5,5a,5a1,9,9a,16a-hexahydrospiro[5,9-diaza-16b-boraindeno[2,1-b]naphtho[1,2,3-fg]anthracene-11,9′-fluorene] (DABNA-Spiro-Cz), was designed and successfully synthesized to construct a novel EML structure. Completely fused within DABNA-Spiro-Cz, the p-type host and blue fluorescent dopant can independently perform their respective roles. An exciplex is formed between n-type host and p-type host unit in the DABNA-Spiro-Cz molecule and its energy is effectively transferred to the blue fluorescent dopant unit in DABNA-Spiro-Cz. In other words, a degree of freedom is earned from a conventional 3-component exciplex-dopant system. A high external quantum efficiency of 14.9 % was achieved thanks to “zero-radius of intramolecular energy transfer in exciplex (ZETPLEX)” system, which is completely non-conventional and novel. We believe the ZETPLEX mechanism opens a new era of designing emissive materials and paves a new way of constructing a novel EML and device architecture for highly efficient OLEDs.

Constructing an Asymmetric Covalent Triazine Framework to Boost the Efficiency and Selectivity of Visible-Light-Driven CO2 Photoreduction.

The photocatalytic reduction of CO2 represents an environmentally friendly and sustainable approach for generating valuable chemicals. In this study, a thiophene-modified highly conjugated asymmetric covalent triazine framework (As-CTF-S) is developed for this purpose. Significantly, single-component intramolecular energy transfer can enhance the photogenerated charge separation, leading to the efficient conversion of CO2 to CO during photocatalysis. As a result, without the need for additional photosensitizers or organic sacrificial agents, As-CTF-S demonstrates the highest photocatalytic ability of 353.2µmolg-1 and achieves a selectivity of ≈99.95% within a 4h period under visible light irradiation. This study provides molecular insights into the rational control of charge transfer pathways for high-efficiency CO2 photoreduction using single-component organic semiconductor catalysts.

Viscosity-modulated intramolecular excitation energy transfer for mitochondria-targeted sensing and photokilling

Viscosity is a key parameter of mitochondria that related to several diseases. To design a probe acting as both the mitochondria-targeted viscosity sensor and photosensitizer is meaningful for diagnosis and therapies. Herein, we report a ratiometric viscosity sensor with dual-emission mediated by excitation energy transfer (EET) effect, which can detect the mitochondrial viscosity and serve as an efficient photosensitizer to eradicate cancer cells. The probe comprises of a blue-emitting imidazole moiety as the energy donor and a green-emitting boron dipyrromethene (BODIPY) core as the energy acceptor, respectively. Via viscosity-modulated EET effect, the dual-emissive probe can sensitively detect the medium viscosity in a ratiometric model. Directed by imidazole as the targeting factor, the probe can specifically accumulate in mitochondria and ratiometrically determine the intracellular viscosity increase induced by Nystatin treatment. Furthermore, it also exhibits light-triggered reactive oxygen species (ROS) generation including singlet oxygen and superoxide radical, which can efficiently kill the cancer cells under white light illumination. Thus, this work provides a versatile and promising candidate for disease diagnosis and phototherapy.

Luminescent Ln3+-based silsesquioxanes with a β-diketonate antenna ligand: toward the design of efficient temperature sensors.

We report the synthesis and single-crystal X-ray diffraction, magnetic, and luminescence measurements of a novel family of luminescent cage-like tetranuclear silsesquioxanes (PhSiO1.5)8(LnO1.5)4(O)(C5H8O2)6(EtOH)2(CH3CN)2⋅2CH3CN (where Ln = Tb, 1; Tb/Eu, 2; and Gd, 3), featuring seven-coordinated lanthanide ions arranged in a one-capped trigonal prism geometry. Compounds 1 and 2 exhibit characteristic Tb3+ and Tb3+/Eu3+-related emissions, respectively, sensitized by the chelating antenna acetylacetonate (acac) ligands upon excitation in the UV and visible spectral regions. Compound 3 is used to assess the energies of the triplet states of the acac ligand. For compound 1, theoretical calculations on the intramolecular energy transfer and multiphonon rates indicate a thermal balance between the 5D4 Stark components, while the mixed Tb3+/Eu3+ analog 2, with a Tb:Eu ratio of 3:1, showcases intra-cluster Tb3+-to-Eu3+ energy transfer, calculated theoretically as a function of temperature. By utilizing the intensity ratio between the 5D4→7F5 (Tb3+) and 5D0→7F2 (Eu3+) transitions in the range 11-373K, we demonstrate the realization of a ratiometric luminescent thermometer with compound 2, operating in the range 11-373K with a maximum relative sensitivity of 2.0% K-1 at 373K. These findings highlight the potential of cage-like silsesquioxanes as versatile materials for optical sensing-enabled applications.

DNA tetrahedral nanostructure-corbelled DNA walker for intramolecular electrochemiluminescence resonance energy transfer sensing of tumor exosomes

Exosomes as new noninvasive biomarkers play a prominent role in early cancer diagnosis, but tumor-derived exosomes are difficult to detect upon tumor initiation because of their low levels. Herein, we proposed a novel and stable strategy for exosomes detection based on intramolecular electrochemiluminescence resonance energy transfer (ECL-RET) and DNA tetrahedral nanostructures (DTNs)-corbelled DNA walker. To enhance the ECL efficiency of luminophores, abundant Ru(bpy)32+ molecules were coordinatively immobilized on Zr12-adb nanoplates (NPs) to form Ru-Zr12-adb NPs. So, high ECL-RET efficiency based on the combination of Zr12-adb NPs (donor) and Ru(bpy)32+ (acceptor) into one nanostructure resulted in considerably enhanced ECL response. Impressively, DNA walker with six track strands supported by DTNs demonstrated enhanced walking speed and high reaction efficiency because of the improved local concentration and space confinement effect of DTNs. In consequence, this as-designed ingenious ECL biosensor exhibited excellent sensing performance for exosomes.