Intramolecular Energy Transfer Mechanism Research Articles

A coumarin-naphthalimide-based fluorescent probe for the ratiometric detection of Hg2+ utilizing an ICT-FRET mechanism

Mercury, as one of the most toxic elements in environmental and biological samples, can poses a grave threat to the integrity of the nervous, reproductive, immune, and digestive systems. Hence, it is significant to exploit convenient and rapid fluorescent probes featuring high sensitivity and selectivity for monitoring the concentration level of mercury ions (Hg2+). In this paper, a ratiometric fluorescent probe for Hg2+ based on intramolecular charge transfer (ICT) and fluorescence resonance energy transfer (FRET) mechanisms was developed by using coumarin ad energy donor and naphthalimide as energy acceptor, and thionocarbonate as the recognizing group for Hg2+. When the probe alone was present in the system, the thionocarbonate group of the probe prevented the electron transfer and the ICT process was off, thus preventing the FRET process of the probe as well. The probe alone emitted the intrinsic blue fluorescence of coumarin upon excitation at 397 nm. After providing Hg2 the thionocarbonate unit reacted with Hg2+, which restored the ICT process of the naphthalimide donor, and the FRET process in turn took place. Upon adding Hg2+, the probe emitted yellow fluorescence. In addition, the fluorescence intensity ratio at 548 nm and 476 nm (I548 nm/I476 nm) of the probe linearly corrected with the concentration of Hg²⁺ ions in the range of 0.1–12 μM. A limit of detection of 0.055 μM was obtained. Meanwhile, the probe exceptional recognized Hg2+ across a broad pH range (pH=4.00–10.00), including physiological pH. Cellular studies further confirmed the probe's negligible cytotoxicity and its potential for ratiometric fluorescence imaging of intracellular Hg²⁺ ions in A549 cells. In addition, the probe was loaded on filter paper to make test strips and combined with a smartphone to achieve rapid visual quantitative detection of Hg2+.

Temperature-dependent vibrational energy relaxation of hydrogen-bonded and free OD groups at the air-water interface.

Water interfaces play a crucial role in regulating interactions and energy flow. Vibrational sum-frequency generation (vSFG) spectroscopy provides structural and dynamic information on water molecules at interfaces. It has revealed, for instance, the presence of the hydrogen-bonded and free OH groups at the air-water interface. Here, using temperature-dependent, time-resolved vSFG, we focus on the vibrational energy relaxation dynamics of interfacial heavy water (D2O). We reveal that while the relaxation timescale for hydrogen-bonded OD stretch modes is temperature-independent, the lifetime of the free OD stretch mode decreases with increasing temperature. Our data, supported by simulations, suggest that both intramolecular energy transfer and rotational reorientation mechanisms jointly contribute to the energy relaxation process of the free OD, with temperature influencing these mechanisms differently.

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.

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.

Photoswitchable Molecular Units with Tunable Nonlinear Optical Activity: A Theoretical Investigation.

The first-, second-, and third-order molecular nonlinear optical properties, including two-photon absorption of a series of derivatives, involving two dithienylethene (DTE) groups connected by several molecular linkers (bis(ethylene-1,2-dithiolato)Ni- (NiBDT), naphthalene, quasilinear oligothiophene chains), are investigated by employing density functional theory (DFT). These properties can be efficiently controlled by DTE switches, in connection with light of appropriate frequency. NiBDT, as a linker, is associated with a greater contrast, in comparison to naphthalene, between the first and second hyperpolarizabilities of the "open-open" and the "closed-closed" isomers. This is explained by invoking the low-lying excited states of NiBDT. It is shown that the second hyperpolarizability can be used as an index, which follows the structural changes induced by photochromism. Assuming a Förster type transfer mechanism, the intramolecular excited-state energy transfer (EET) mechanism is studied. Two important parameters related to this are computed: the electronic coupling (VDA) between the donor and acceptor fragments as well as the overlap between the absorption and emission spectra of the donor and acceptor groups. NiBDT as a linker is associated with a low electronic coupling, VDA, value. We found that VDA is affected by molecular geometry. Our results predict that the linker strongly influences the communication between the open-closed DTE groups. The sensitivity of the molecular nonlinear optical properties could assist with identification of molecular isomers.

Theoretical study on the pyrolysis process of POSS nanocomposites based on the molecular vibration frequency

Identifying the factors that determine the thermal stability of polymer nanocomposites with inorganic fillers is vital. This study investigates how the modulation of polyhedral oligomeric silsesquioxanes (POSSs) affects the polymer-chain thermodynamics, using a multiscale analysis that integrates reactive molecular dynamics, first-principles calculations, and classical vibrational dynamics. The intramolecular energy transfer mechanism depending on the polymer-chain vibration frequency and covalent structure was analyzed for the entire pyrolysis process. The results revealed that the low-frequency vibration of POSS is key for the superior nanocomposite thermal stability. The dual frequency of the C–Si stretching mode directly contributes to the collection and dissipation of the thermal energy contained in the crosslinked polymer chain. The ability to block exothermic reaction pathways under pyrolysis conditions was also identified. This result elucidates the mechanism by which inorganic fillers perturb the thermodynamics and thermochemistry of polymer matrices as energy transfer within molecular chains.

An ICT-FRET-based ratiometric fluorescent probe for hydrogen polysulfide based on a coumarin-naphthalimide derivative

Hydrogen polysulfide (H2Sn, n > 1), as one of the important members of reactive sulfur species (RSS), plays a vital part in the processes of both their physiology and pathology. In this work, a ratiometric fluorescent probe for H2Sn had been designed and prepared based on the combination mechanism of intramolecular charge transfer (ICT) and fluorescence resonance energy transfer (FRET). The probe chose a coumarin derivative as the energy donor, a naphthalimide derivative as the energy acceptor and 2-fluoro-5-nitrobenzoate as the H2Sn recognition group. When H2Sn was not present in the system, the ICT process of the naphthalimide acceptor was inhibited and the FRET process from the coumarin donor to the naphthalimide acceptor was turned off. When H2Sn was added, both ICT and FRET occurred due to the nucleophilic substitution-cyclization reactions between the probe and hydrogen polysulfide. In addition, the ratio value of the emission intensities at 550 nm and 473 nm (I550 nm/I473 nm) of this probe had a good linear relationship with H2Sn concentration in the range of 6.0 × 10-7-5.0 × 10-5 mol·L-1, and a detection limit of 1.8 × 10-7 mol·L-1 was obtained. The developed probe had high selectivity and sensitivity, as well as good biocompatibility. Additionally, the probe had been used to successfully image both indigenous and exogenous hydrogen polysulfide in A549 cells using confocal microscope.

Integration of Exciton Donor and Acceptor in a Blue‐Emitting Molecule with Zero Radius of Intramolecular Energy Transfer Mechanism for Highly Efficient and Stable Fluorescent OLEDs

AbstractMultimaterial emission layer (EML) with host and dopant is known for its advantages in efficiency and lifetime for organic light‐emitting diodes (OLEDs). However, as the compositions and the mixing ratio in the EML diversify, complex device physics and photophysics and complicated fabrication processes become challenging issues. Herein, a new concept to integrate exciton donor (host) and acceptor (dopant) into a single emitting molecule is suggested. 9‐(8,9,10,11‐Tetradeuterospiro[benzo[de]anthracene‐7,9′‐fluoren]‐2'‐yl)‐9H‐carbazole (SBAF‐Cz) and 8,9,10,11‐tetradeutero‐N‐(9,9‐dimethyl‐9H‐fluoren‐2‐yl)‐N‐phenylspiro[benzo[de]anthracene‐7,9′‐fluoren]‐3‐amine (FPA‐SBAF) are used as host and dopant, respectively. By integrating two units, 8,9,10,11‐tetradeutero‐2′‐(9H‐carbazol‐9‐yl)‐N‐(9,9‐dimethyl‐9H‐fluoren‐2‐yl)‐N‐phenylspiro[benzo[de]anthracene‐7,9′‐fluoren]‐3‐amine (FPA‐SBAF‐Cz) is synthesized, and photophysical and electrical properties are characterized. Density functional theory and experimental results consistently reveal that SBAF‐Cz and FPA‐SBAF are photophysically and electrically independent. The electrical properties of FPA‐SBAF‐Cz behave independently, while the photophysical properties are the sum of those of SBAF‐Cz and FPA‐SBAF, which is attributed to the zero radius of intramolecular energy transfer (ZRIET) between donor and acceptor in FPA‐SBAF‐Cz. The single‐component blue OLED with FPA‐SBAF‐Cz exhibits a maximum external quantum efficiency of 4.18%, which is higher than those of OLEDs with SBAF‐CZ:FPA‐SBAF multicomponent EMLs. Surprisingly, the device lifetime to 50% decrease from initial luminance is 114 h in FPA‐SBAF‐Cz OLED, which is 2.2 times longer than that of SBAF‐Cz:FPA‐SBAF OLEDs.

Synthesis, solid state characterization, theoretical and experimental spectroscopic studies of the new lanthanide complexes

Three new complexes Na[Ln(pic)4]ּ⋅2.5H2O (Ln = Tb, Eu or Gd; pic = picolinate) were synthesized and characterized by infrared spectroscopy, powder X-ray diffraction and thermogravimetric analyses. The molecular structures of the complexes have been determined by single-crystal X-ray diffraction. The three isostructural lanthanide complexes crystalize in the hexagonal system with space group P6122 to Eu complex and Gd complex and space group P6522 to Tb complex. In each of the complexes, the picolinate ligands are bonded to Ln3+ and Na+ ions by different coordination modes promoting polymeric structures. The photoluminescent properties of complexes were studied and combined with theoretical studies using the density functional theory (DFT: B3LYP, PBE1PBE) and the semiempirical method AM1/Sparkle from the single crystal X-ray diffraction structures to assign a suitable model for describing the system. The B3LYP DFT functional was considered the most adequate for providing structural properties of the compounds and for describing luminescence properties. The excited triplet states (T1) and excited singlet states (S1) of the ligand were determined theoretically using Time-dependent DFT calculations (TD-DFT: B3LYP, CAM-B3LYP and LC-wPBE) and INDO/S-CIS, with the best agreement with experimental values obtained from the LC-wPBE DFT functional. The photoluminescent spectra of the complexes and their lifetime measurements were determined indicating that the Eu complex and Tb complex display different intramolecular energy transfer mechanisms with higher efficiency to ligand-to-terbium energy transfer. In addition, the experimental and theorical Judd-Ofelt intensity parameters and quantum yields of the complexes were also determined and discussed besides to a proposed 9-state diagram to describe the luminescence properties of the Eu complex. The low value of emission quantum efficiency of 5D0 emitting level of Eu(III) ion was explained by the presence of the ligand-to-metal charge transfer state (LMCT) evidenced experimentally and theoretically. A good agreement was obtained between the proposed kinetic model and experimental results showing the consistency of the set of rate equations assumed and the intramolecular pathways proposed.

High-Gain of NdIII Complex Doped Optical Waveguide Amplifiers at 1.06 and 1.31µm Wavelengths Based on Intramolecular Energy Transfer Mechanism.

Chelate phosphine oxide ligand (9,9-dimethyl-9H-xanthene-4,5-diyl) bis (diphenylphosphineoxide) (XPO) is prepared as a neutral ligand to synthesize complex Nd (TTA)3 (XPO) (TTA = 2-thenoyltrifluoroacetone). An appropriate energy gap between the XPO and TTA ligands, which can support two additional energy transfer routines from the first excited triplet state (T1 ) energy level of the XPO to that of the TTA, improves energy transfer in the Nd complex. Based on intramolecular energy transfer mechanism, optical gains at 1.06 and 1.31µm are demonstrated in Nd (TTA)3 (XPO)-doped polymer waveguides with the excitation of low-power light-emitting diodes (LEDs) instead of semiconductor lasers as pump sources. Using the vertical top-pumping mode of a 365nm LED, relative gains of 22.5 and 8.4dBcm-1 are obtained at 1.06 and 1.31µm, respectively, in a 0.2 cm long embedded waveguide with a cross-section of 8×5µm2 . The active core layer is Nd (TTA)3 (XPO)-doped SU-8 polymer. Moreover, relative gains are achieved in evanescent-field waveguide with a cross-section of 6×4µm2 . The 21.0 and 5.6dBcm-1 relative gains are achieved at 1.06 and 1.31µm, respectively, with a net gain of 13.8±0.3dBcm-1 obtained at 1.06µm in a 0.9 cm long SU-8 waveguide with Nd (TTA)3 (XPO)-doped polymethylmethacrylate as upper cladding.

Optical gain at 1.55 µm of Er(TMHD)3 complex doped polymer waveguides based on the intramolecular energy transfer effect.

Based on the intramolecular energy transfer mechanism between organic ligand TMHD (2, 2, 6, 6-tetramethyl-3, 5-heptanedione) and central Er3+ ions, optical gains at 1.55 µm were demonstrated in three structures of polymer waveguides using complex Er(TMHD)3-doped polymethylmethacrylate (PMMA) as the active material. With the excitation of two low-power UV light-emitting diodes (LEDs) instead of 980 or 1480 nm lasers, relative gains of 3.5 and 4.1 dB cm-1 were achieved in a 1-cm-long rectangular waveguide with an active core of Er(TMHD)3-doped PMMA polymer. Meanwhile, relative gain of 3.0 dB cm-1 was obtained in an evanescent-field waveguide with cross-section of 4 × 4 µm2 using passive SU-8 polymer as core and a ∼1-µm-thick Er(TMHD)3-doped PMMA as upper cladding. By growing a 100 nm thick aluminum mirror and active lower cladding, the optical gain was doubled to 6.7 dB cm-1 in evanescent-field waveguides because of the stimulated excitation of Er3+ ions in the upper and lower cladding and the improved absorption efficiency.

Preparation, Structure and Spectroscopic Properties of NH4[Ln(S2CNH2)4] ⋅ H2O (Ln=La, Eu)

AbstractThe title compounds were prepared under mild ambient conditions by a facile co‐precipitation route. NH4[Eu(S2CNH2)4] ⋅ H2O (a) and NH4[La(S2CNH2)4] ⋅ H2O (b) crystallize isotypically in the monoclinic space group P21/c with a=8.4461(3), b=13.6367(3), c=16.2945(5) Å, β=103.759(2)° (for (a)), and a=8.50484(9), b=13.84476(16), c=16.20816(17) Å, β=103.7644(11)° for (b), respectively. The spectroscopic data reveal the presence of a ligand‐to‐metal charge transfer (LMCT) process of low energy in a and in the solid solutions NH4[La1−xEux(S2CNH2)4] ⋅ H2O (x=0.016 and 0.05). Despite of the consequent efficient luminescent quenching, it was possible to recorded excitation and emission spectra at room temperature. These spectra are characterized by narrow bands due to intraconfigurational‐4f transitions of the Eu3+ ion. However, broad bands associated to the LMCT state were also observed, mainly for the solid solutions NH4[La1−xEux(S2CNH2)4] ⋅ H2O (x=0.016 and 0.05). Consequently, an intramolecular energy transfer mechanism is proposed, taking into account the role of the LMCT on the spectroscopic properties of dithiocarbamate complexes.

Pyrene modification enables enhanced two-photon excited ligand dissociation of a Ru(II) complex containing monodentate ligands

Ru(II) complexes which can undergo photo-induced ligand dissociation display potentials for biological applications in some aspects. However, their short excitation wavelengths limit tissue penetration and therefore applications. Two-photon technic is a general way to shift the excitation wavelength to the near-infrared region (NIR), but few Ru(II) complexes with photolabile ligands having large two-photon absorption cross sections (δ2) have been reported so far. In this work, by modification with a pyrene group on the tpy ligand, the resultant complex [Ru(tpy-py)(CH3CN)3]2+ (1) displayed enhanced two-photon induced ligand dissociation compared with the parent complex [Ru(tpy)(CH3CN)3]2+ (2), probably through an intramolecular energy transfer mechanism. The ligand dissociation process was investigated in detail by absorption, 1H NMR, ESI MS spectra and theoretical calculations.

Ultrafast Electron/Energy Transfer and Intersystem Crossing Mechanisms in BODIPY-Porphyrin Compounds

Meso-substituted borondipyrromethene (BODIPY)-porphyrin compounds that include free base porphyrin with two different numbers of BODIPY groups (BDP-TTP and 3BDP-TTP) were designed and synthesized to analyze intramolecular energy transfer mechanisms of meso-substituted BODIPY-porphyrin dyads and the effect of the different numbers of BODIPY groups connected to free-base porphyrin on the energy transfer mechanism. Absorption spectra of BODIPY-porphyrin conjugates showed wide absorption features in the visible region, and that is highly valuable to increase light-harvesting efficiency. Fluorescence spectra of the studied compounds proved that BODIPY emission intensity decreased upon the photoexcitation of the BODIPY core, due to the energy transfer from BODIPY unit to porphyrin. In addition, ultrafast pump-probe spectroscopy measurements indicated that the energy transfer of the 3BDP-TTP compound (about 3 ps) is faster than the BDP-TTP compound (about 22 ps). Since the BODIPY core directly binds to the porphyrin unit, rapid energy transfer was seen for both compounds. Thus, the energy transfer rate increased with an increasing number of BODIPY moiety connected to free-base porphyrin.

Optical properties of organic neodymium complex doped optical waveguides based on the intramolecular energy transfer effect

We report a method of using neodymium complexes as active waveguide core materials to achieve optical gain at the 1060 nm wavelength when using an LED instead of an 808 nm semiconductor laser as the pump source. Through the intramolecular energy transfer mechanism between ligands and Nd3+ ions, the photoluminescence spectrum could be obtained on a 100µm thick film of neodymium complex doped PMMA polymer under excitation of a 380 nm-450 nm LED. We also present calculations showing that the pump power required to generate optical gain (turn-on power) for a LED and 808 nm laser is 3.3 mW and 40 mW, respectively. An optical gain of about 6 dB can be obtained on a 20-mm-long waveguide when pumped by a 25 mW LED compared with that of about 1.4 dB excited by a 60 mW 808 nm semiconductor laser.

Synthesis, NMR and optical features of intense green color terbium(III) complexes

The paper reports the three highly green luminescent terbium(III) complexes functionalized with 1,1,1,5,5,6,6,6-octafluorohexane-2,4-dione (L) as main ligand, 1,10-phenanthroline (phen) and2,2′-bipyridyl (bipy) as ancillary ligands. These complexes were characterized by means of IR, 1H-NMR, elemental analysis, UV–vis, TG-DTG and photoluminescence (PL) spectroscopy. In 1H-NMR spectra, large highfield and lowfield shifts are noticed in these paramagnetic complexes. The proton resonances of phen and bipy have been shifted to highfield, while, the resonance of methine proton in main ligand has been shifted to lowfield. In this way, all the proton signals are resolved as revealed in NMR spectra. The photoluminescent features clearly indicate that the substitution of solvent molecules by ancillary ligand in the coordination sphere enhance the emission intensity and decay time of the complexes. Furthermore, the intramolecularenergy transfer mechanism shows that an efficient transfer of energy from triplet level of ligands to the emitting level of terbium(III) ion takes place in the complexes. In this manner, main ligand and ancillary ligands sensitize the terbium(III) ion yielding the intense and characteristic green luminescence in the complexes. The CIE color coordinates of Tb(L)3bipy complex exactly matches with standard pure green color (x = 0.21, y = 0.71) of NTSC (National Television Standard Committee) which makes them pure green promising component for potencial application as luminescent materials. The beauty of complexes is that these acts as NMR shift reagent as well as these are of great interest in the field of emitting material and display devices.

Real-Time Mapping of Ultratrace Singlet Oxygen in Rat during Acute and Chronic Inflammations via a Chemiluminescent Nanosensor.

Sensing nonradiation-induced singlet oxygen (1 O2 ) in whole-animal is deemed as one of the most challenging tasks in noninvasive techniques due to the µs level lifetime of 1 O2 and quenching by numerous reductants in tissues. Here a distinct chemiluminescent (CL) nanosensor (NTPE-PH) that boasts ultrahigh concentrated CL units in one nanoparticle is reported. Taking advantage of the intramolecular energy transfer mechanism that promises high energy transfer efficiency and the aggregation-induced emission behavior that guarantees high CL amplification, the NTPE-PH sensor is sensitive to a nm level 1 O2 . Experiments demonstrate that the NTPE-PH yields a highly selective CL response toward 1 O2 among common reactive oxygen species. With proved low cytotoxicity and good animal compatibility, real-time mapping of ultratrace 1 O2 in whole-animal during acute and chronic inflammations is first achieved. It is anticipated that the NTPE-PH sensor can be a useful tool for monitoring 1 O2 variation during immune response and pathological processes corresponding to different stimuli, even with drug treatment included.

Investigation of ultrafast energy transfer mechanism in BODIPY–Porphyrin dyad system

Novel β-fused BODIPY-Porphyrin compounds that contain free base porphyrin (TPP2BDP) and its Ni(II) complex (NiTPP2BDP) were synthesized to investigate intramolecular energy transfer mechanisms of β-fused BODIPY-porphyrin dyads and effect of the unfilled d shell metal ion on energy transfer mechanism. Fluorescence spectra of compounds exhibited that BODIPY emission was diminished upon excitation of the BODIPY unit because of the energy transfer from BODIPY to porphyrin unit. Femtosecond pump-probe spectroscopy measurements revealed that energy transfer of investigated compounds are faster than previous studies in literature. Rapid energy transfer (about 500 fs) from BODIPY to porphyrin was observed for both compounds when BODIPY unit is excited due to direct linkage of BODIPY to porphyrin unit. Intersystem crossing mechanism was also observed for the compound that contains free base porphyrin (TPP2BDP), whereas d-d transition was observed for the compound that contains metalloporphyrin (NiTPP2BDP) due to unfilled d orbital of Ni(II) ion.

Dual resonance energy transfer in triple-component polymer dots to enhance electrochemiluminescence for highly sensitive bioanalysis.

Polymer dots (Pdots) have become a type of attractive illuminant for electrochemiluminescence (ECL). However, the low ECL efficiency severely limits their practicability. Here, we design a dual intramolecular resonance energy transfer (RET) mechanism with newly synthesized triple-component Pdots to achieve great ECL enhancement. This mechanism efficiently shortens the path of energy transmission, thus greatly promoting the ECL amplification by 380 and 31 times compared to systems with no and single RET, and results in a relative ECL efficiency of 23.1% (vs. 1mM Ru(bpy)32+). Using metal-organic frameworks to carry the triple-component Pdots, a highly luminescent probe is proposed. By integrating the probe with target-mediated enzymatic circulation amplification and DNA arrays, a highly sensitive ECL imaging method is designed for simultaneous visual analysis of two kinds of proteins, mucin 1 and human epidermal growth factor receptor 2, on living cells, which exhibited linear ranges of 1 pg mL-1 to 5 ng mL-1 and 5 pg mL-1 to 10 ng mL-1 with limits of detection of 1 pg mL-1 and 5 pg mL-1, respectively. The proposed strategy showed promising application in bioanalysis.