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The loading strategy of cocatalysts affects its activity exerting and atom utilization. Here, a novel strategy for loading precious metal (Pt) cocatalysts by means of ultrathin N-doped carbon layer is reported. The strategy is based on a pyrolysis process of predesigned N-containing polymers and Pt complexes on hard-template surface, during which Pt can be reduced by carbon from pyrolysis at high temperatures. Finally, the hollow TiO2 composite with stable and dispersed Pt on its inner surface was prepared. It shows an ultrahigh photocatalytic H2 production activity as high as 25.7 mmol h−1 g−1 with methanol as sacrificial regent, and displays an apparent quantum yield as 13.2%. The improved photocatalytic activity and stability can be attributed to the highly dispersed and ultrafine Pt nanoparticles, enhanced interaction between Pt-species and carbon support, fast photo-excited electron transport from the high graphitization degree of NC layers, ample oxygen vacancies/defects, as well as the manipulated local charge distribution of Pt/NC-layer configuration. Additionally, the universality of the proposed strategy was demonstrated by replacing metal sources (such as, Ru and Pd). This work presented a promising strategy for the design and development of novel photocatalysts, which shows a broad application prospect.

Development of new photosensitizers (PSs) with high singlet oxygen quantum yield and minimal side effects is of great interest in photodynamic therapy (PDT). Herein, a facile strategy to significan...

By combining 5,10,15,20-tetra(4-chlorine)phenylporphyrin (TClPP) and α-Keggin polyoxometalate H5PV2Mo10O40 (H5PVMo) via a simple ion-exchange method, an organic-inorganic hybrid material [C44H28N4Cl4]1.5[H2PMo10V2O40]•2C2H6O (H2TClPP-H2PVMo) was prepared and thoroughly characterized by a variety of techniques. The homogeneous photocatalytic degradation of 2-chloroethyl ethyl sulfide (CEES) (5 μL) by H2TClPP-H2PVMo (1 × 10−6 mol/L) was studied in methanol and methanol-water mixed solvent (v/v = 1:1), in which the degradation rate of CEES reached 99.52% and 99.14%, respectively. The reaction followed first-order reaction kinetics, and the half-life and kinetic constant in methanol and the mixed solvent were respectively 33.0 min, -0.021 min−1 and 15.7 min, -0.043 min−1. Mechanism analysis indicated that under visible light irradiation in the air, CEES was degraded via oxidation and alcoholysis/hydrolysis in methanol and the mixed solvent. O2•− and 1O2 generated by H2TClPP-H2PVMo selectively oxidized CEES into a non-toxic sulfoxide. Singlet oxygen capture experiments showed that H2TClPP-H2PVMo (Φ = 0.73) had a higher quantum yield of singlet oxygen than TClPP (Φ = 0.35) under an air atmosphere and visible light irradiation.

Carbon nitride-based photocatalysts hold an enormous potential in producing hydrogen. A strategy to simultaneously create isotype heterojunctions and active sites in highly-crystallized carbon nitride is anticipated to significantly boost the photocatalytic activity, but is yet to be realized. Herein, we find that cobalt salt added in the ionothermal synthesis can promote the phase transition of heptazine-based crystalline carbon nitride (CCN) to triazine-based poly(triazine imide) (PTI), rendering the creation of single-atom cobalt coordinated isotype CCN/PTI heterojunction. Co-CCN/PTI exhibits an appreciable apparent quantum yield of 20.88% at 425 nm for photocatalytic hydrogen production with a rate achieving 3538 μmol h−1 g−1 (λ > 420 nm), which is 4.8 times that of CCN and 27.6 times that of PTI. The high photocatalytic activity is attributed to the Type II isotype highly-crystallized CCN/PTI heterojunction for promoting charge carrier migration, and the single-atom Co sites for accelerating surface oxidation reaction.

The synthesis of a novel polyhedral oligomeric silsesquioxane functionalized with eight rigid and directional terpyridine-based arms (Ter-POSS) was successfully achieved via a Sonogashira reaction. The POSS based ligand was extensively characterized using different techniques including 1H, 13C and 29Si NMR as well as UV-Vis and fluorescence spectroscopies. The assembly of these nano-caged units in the presence of different transition metal ions (Fe2+, Zn2+ and Cu2+) as well as of a cation from the lanthanides (Eu3+) was investigated using absorption and emission spectroscopies. The final materials display an evident emission in different regions of the visible spectrum as a function of the cation employed. Additional insights into the structural organization of Ter-POSS in the presence of metal cations were obtained via molecular mechanics and molecular dynamics simulations. The polymeric material resulting from the complexation with europium displays a white light emission ascribed to the presence of combined contributions from the blue, green and red regions. The final self-assembled organizations display an increased quantum yield with the highest value (29.6%) obtained in the presence of Zn2+. Moreover, the white-light emitting europium-based nanostructure exhibits one of the highest quantum yields reported in the literature for similar solids.

4,4′-(4-Phenylpyridine-2,6-diyl)dibenzonitrile (PyDCN) was designed to reduce the electron-withdrawing strength and to decentralize the unsaturated N atoms relative to triazine. PyDCN was used as an acceptor to construct thermally activated delayed fluorescence (TADF) emitters PyDCN–PXZ and PyDCN–DMAC with phenoxazine (PXZ) and 9,9-dimethyl-9,10-dihydroacridine (DMAC) as electron donors. The relatively high radiative transition rate constants (kF) in the order of 107 s−1, high photoluminescence quantum yields in the range of 80–90%, and balanced charge transportation were detected for both TADF emitters. PyDCN–DMAC exhibited electroluminescence (EL) with a peak at 472 nm and CIE coordinates of (0.17, 0.26), more approaching to real blue in comparison with most of DMAC based sky-blue TADF analogues. A high external quantum yield (ηext) of 25.6% was obtained for a PyDCN–DMAC doped organic light-emitting diode (OLED). PyDCN–PXZ exhibited green EL with a ηext of 26.9% at 519 nm in the doped OLED. Its non-doped yellow OLED also revealed a moderate ηext of 18.2% with a peak at 557 nm. Furthermore, PyDCN–DMAC was used as the blue host emitter to fabricate a single-emitting-layer all-TADF white OLED in combination with a yellow home-made TADF emitter PP–PXZ, which exhibited a maximum ηext of 18.5% with CIE coordinates of (0.38, 0.44) and excellent color stability.

Searching for non-noble-metal cocatalyst for hydrogen evolution in photocatalytic water–splitting has attracted much attention. Herein, molybdenum phosphide (MoP) as an efficient and stable cocatalyst was prepared in a facile phosphorization process at relatively low temperatures under N2 atmosphere, and the effect of preparation temperature (300–500 °C) was studied. Using Eosin Y (EY) and the prepared sample as catalyst (sensitizer) and cocatalyst, respectively, the photocatalytic activity for hydrogen evolution was investigated in aqueous trimethylamine (TMA) solution under visible light irradiation (λ ≥ 420 nm). MoP prepared at 400 °C (MoP-400) exhibits the highest sensitization activity and superior stability, and the maximal apparent quantum yield (AQY) for hydrogen evolution is up to 48.0% at 420 nm, much higher than the most reported data for MoP-based photocatalysts. The highest activity can be attributed to the highest P content in MoP-400 and the rapidest electron transfer between photoexcited EY and MoP-400. The possible mechanism was discussed.

Methyl group plays an important role in the regulation of the photoluminescence and electroluminescence properties of thermally activated delayed fluorescence (TADF) emitters. In this work, a new type of methyl effect was revealed by designing donor-accepter-donor (D-A-D) type TADF systems with decorating methyl on the ortho-position of the donor units. Different from previous work in which ortho-position methyl resulted in improved TADF properties, the insertion of methyl groups in this work led to the reduction of molecular rigidity, photoluminescence quantum yield (PLQY) and the ratio of delayed fluorescence, as well as the extension of the lifetime of delayed fluorescence. The unusual changes of the photoluminescence behavior were well explained by the theoretical simulations and further verified by the performance in electroluminescence devices. The blue organic light-emitting diodes (OLEDs) based on the new emitters achieved the maximum external quantum efficiency (EQE) of 19.3%.

A new catalyst for both water reduction and oxidation, based on an infinite chain, {[Ni(tn)2]3 [Fe(CN)4 (μ-CN)2]2}n, is formed by the reaction of NiCl2, 1,3-propanediamine (tn) and K3 [Fe(CN)6]. {[Ni(tn)2]3 [Fe(CN)4 (μ-CN)2]2}n can electro-catalyze hydrogen evolution from a neutral aqueous buffer (pH 7.0) with a turnover frequency (TOF) of 1561 mol of hydrogen per mole of catalyst per hour (H2/mol catalyst/h) at an overpotential (OP) of 837 mV {[Ni(tn)2]3 [Fe(CN)4 (μ-CN)2]2}n also can electro-catalyze O2 production from water with a TOF of ∼45 mol O2 (mol cat)−1s−1 at an OP of 591 mV. Under blue light (λ = 469 nm), together with CdS nanorods (CdS NRs) as a photosensitizer, and ascorbic acid (H2A) as a sacrificial electron donor, {[Ni(tn)2]3 [Fe(CN)4 (μ-CN)2]2}n can photo-catalyze hydrogen generation from an aqueous buffer (pH 4.0) with a turnover number (TON) of 11,450 mol H2 per mole of catalyst (mol of H2 (mol of cat)−1) during 10 h irradiation. The average of apparent quantum yield (AQY) is as high as 40.96% during 10 h irradiation. Studies indicate that {[Ni(tn)2]3 [Fe(CN)4 (μ-CN)2]2}n exists in two forms: a cyano-bridged chain ({[Ni(tn)2]3 [Fe(CN)4 (μ-CN)2]2}n) in solid, and a salt ([Ni(tn)2]3 [Fe(CN)6]2) in aqueous media; Catalytic reaction occurs on the nickel center of [Ni(tn)2]2+, and the introduction of [Fe(CN)6]3- can improve the catalytic efficiency of [Ni(tn)2]2+ for H2 or O2 generation. We hope these findings can afford a new method for the design of catalysts for both water reduction and oxidation.

The design of two-photon absorption (TPA) materials based on cocrystal engineering is an emerging strategy for constructing nonlinear materials. Here we observe that a prepared BDBT-TCNB cocrystal can retain well the TPA properties from the donor BDBT molecules, but the TPA properties of a BDBT-OFN cocrystal are inhibited upon using the same donor molecule but changing the acceptor molecule of the cocrystal. Via comparing the crystal structures and spectral data of the two cocrystals, we find that BDBT-TCNB cocrystals have obvious intermolecular charge transfer interactions, while the BDBT-OFN cocrystals exhibit totally different intermolecular arene–perfluoroarene interactions. Moreover, strong charge transfer interactions involving the BDBT-TCNB cocrystal also promote an enhancement of the fluorescence intensity and an increase in the lifetime and photoluminescence quantum yield (PLQY) relative to the monomers. Therefore, this example proves that intermolecular interactions involving cocrystals can be controlled via carefully selecting the donor and acceptor molecules, and then the TPA properties of the cocrystals can be selectively adjusted, promoting the development of TPA materials prepared via cocrystal engineering.

International audience; Three room-temperature metallomesogens based on Zn(II) cations pentacoordinated by different chelating N^N^N terpyridines and two monodentate gallate co-ligands were designed and synthesized. Depending on the terpyridine ligand's tip functionality, the complexes self-assemble into either a 3D hexagonal mesophase or into a columnar hexagonal mesophase. A systematic study between the structure (molecular architecture, arrangement of the molecules and columns, and chains in both types of mesophases) and photophysical properties (emission maxima and yields, lifetimes of the excited states in the mesophase), correlated with investigations of single molecules in solution, was conducted. Remarkably, one complex exhibited a record quantum yield of 95.0% in solution, while in the mesophase, despite quenching due to the radiative deactivation from the ILCT state, still retained a considerable emission yield of ϕ = 20.2%. The polarized emission of an oriented film, determined for the first time in columnar metallomesogens, shows a dichroic emission ratio (I||/I⊥) of 1.30. DFT and TDDFT computational studies confirmed the origin of the observed fluorescence anisotropy from the transition dipole moment oriented along the C2 symmetry axis of the molecule combined with a high level of order in the 3D mesophase.

An effort, investigate the photophysical belongings on pyrin-3-amine with 1-acetyl-2, 4-dihydroxybenzene Schiff base Erbium, and Ytterbium multiplexes have been created then categorised in spectroscopic methods identical UV, FTIR, Fluorescence, then Nuclear magnetic resonance spectroscopy. Proved thermal characterization of Schiff base metal complexes was to have high thermal stability by the TGA-DTA technique. Erbium and Ytterbium complexes have high luminescence in nature compared to a free ligand. A bioimaging study with Schiff base metal complexes is fluorescent staining dyes. It is appreciated quality in low cytotoxicity, simple preparation, photostability, and smudged cytoplasm structure. The quantum yield of lanthanides contributes to the brightness of Schiff base rare earth elements. The aim on molecular constructions limits intermolecular metal-ligand connections.

An ecofriendly microwave pyrolysis tactic was employed to synthesize N-doped fluorescent carbon nanodots (N-CNDs) using Gum ghatti and ethylenediamine as a carbon and nitrogen source. The fabricated N-CNDs exhibits high stability in water medium and emits bright blue fluorescence with the quantum yield of 23%. We further established N-CNDs as an excellent visual and selective fluorescent-based nanoprobe for mercury ions (Hg2+ ions) detection. The limit of detection was found to be 4.6 nM. When metal ion chelator ethylenediaminetetraacetic acid (EDTA) was added into the N-CNDs + Hg2+ ions system, the fluorescence was reverted effectively. Moreover, the fluorescent quenching principle of N-CNDs + Hg2+ ions system follows the static quenching mechanism. Finally, the Gum ghatti derived N-CNDs was efficiently applied in environmental water samples like tap and mineral water to determine mercury ions.

Nitrogen and sulfur co-doped carbon dots (N,S-CDs) with strongly orange fluorescent]ce were fabricated through a facile hydrothermal method using o-phenylenediamine and thiourea as original materials. The N,S-CDs performed excitation-independent photoluminescent behavior with excellent stability. The largest emission peak at 565 nm occurred at an excitation wavelength of 420 nm, and the quantum yield (QY) was 14.3%. It was found the absorption spectra of vitamin B12 (VB12) overlaps with the emission peak of N,S-CDs to a large extent, and based on the inner filter effect (IFE) between VB12 and N,S-CDs, a label-free and sensitive detection method of VB12 in drug was established. Under the optimal conditions, the concentration of VB12 performed a satisfactory linear correlation with the fluorescence quenching degree ∆F/F0 of the reaction system at 565 nm in the range of 0.25-20 μM, and the detection limit was 77.5 nM. The N,S-CDs with orange fluorescence emissive perform huge potential in the field of biological analysis.

Chemiluminescence (CL) has been widely used for bioanalysis owing to its high sensitivity, low background and simplicity. However, most of the CL systems need acidic/alkaline conditions or organic solvent to enhance their luminescent efficiency, and the non-physiological conditions can usually lead to the misfunction of biomolecules during biosensing. Herein, we report a highly luminous CL system under physiological conditions based on carbon dots-bis(2-carbopentyloxy-3,5,6-trichlorophenyl) oxalate (CDs-CPPO) micelles, and further used it in biosensing application. In the CL system, the amphiphilic surfactant packed CPPO and hydrophobic CDs together to form CDs-CPPO micelles. Such micelles solution not only isolated the CPPO from water to prevent its hydrolysis but also made the close proximity between CPPO and CDs, thus significantly enhancing the CDs quantum yield. The CL quantum yield was calculated to be 5.26 × 10−4 einsteins/mol, about 200-fold higher than that of the most commonly used luminol CL system. The oxidases (e.g., glucose oxidase) were tested to be susceptible to the organic solvent and non-physiological pH. Hence, the CL system was used for the detection of oxidase substrates (exemplified by glucose) in serum samples, and the limit of detection was as low as 8.4 nmol/L. The highly luminous CL system that can work under physiological conditions is promising for biosensing applications

The development of efficient and stable white-light emissive materials is highly desirable in displays and solid-state lighting. Here we present a high-quality white-light emitter based a dual-emitting MOF hybrid, which is achieved by dye encapsulation engineering within a robust Zr-MOF (PCN-128W) containing a highly luminescent tetraphenylethylene-based ligand. The pore confinement effect well isolates the incorporated dye molecules (trans-4-[4-(Dimethylamino)styryl]-1-methylpyridinium iodide (DSM)) and therefore suppress the aggregation caused luminescence quenching. The dye emission is mainly sensitized by PCN-128W host through Forster resonance energy transfer (FRET), and the FRET process is incomplete, thus enabling the hybrid to feature dual emissions upon a single excitation. The emission color of DSM@PCN-128W hybrid can be systematically tuned from blue to white, and to orange by regulating the dye encapsulation content. A broad white-light emission with a considerably high quantum yield (21.2%) is obtained in the case of dye contents of 0.15 wt%. The luminescence of DSM@PCN-128W hybrid is stable in ambient air for over 1 month, and show good resistance to continuous UV light irradiation, owing to the protective MOF Matrix that largely inhibits the UV exposure to dye molecules. What’s more, by combining DSM@PCN-128W with a commercial UV LED chip, we fabricate a white-light emitting prototype device showing CIE chromaticity coordinates of (0.34, 0.33), a CRI of 79.1, and a CCT of 5525 K.

Covalently attaching a visible light absorbing dye to the graphene quantum dot (GQD) was proven as a viable method to prepare single component metal-free photocatalyst for solar hydrogen production. Despite promising aspects with earlier reported Rhodamine dye attached GQD system, however, quick deterioration of its HER activity within several hours seriously limits its practical application. We have challenged this stability issue by combining the N/S hetero atom doping in GQD structure and molecular structural elaboration of organic dye. By employing 2,3-diaminophenazine (Phz) attached NS-co-doped GQD (Phz-NS_GQD) as a single component photocatalyst in this work, we could demonstrate a dye-sensitized system which sustained over two days without any deterioration (complete linearity up to 50 h was measured) of its HER activity. Higher Apparent Quantum Yield (AQY) values of 49% and 47.7% at 400, 450 nm wavelength respectively were well supported to its improved catalytic efficiency for H2 production. It was shown that the N,S–co doping and the highly efficient photoinduced electron transfer to GQD core facilitated by phenazine dye are responsible for the improved HER efficiency as well as outstanding photostability.

Excited-state intramolecular proton transfer (ESIPT) dyes typically show strong solid-state emission, but faint fluorescence intensity is observed in the solution state owing to detrimental molecular motions. This article investigates the influence of direct (hetero)arylation on the optical properties of 2-(2'-hydroxyphenyl)benzoxazole ESIPT emitters. The synthesis of two series of ESIPT emitters bearing substituted neutral or charged aryl, thiophene, or pyridine rings is reported herein along with full photophysical studies in solution and solid states, demonstrating the dual solution-/solid-state emission behavior. Depending on the nature of substitution, several excited-state dynamics are observed: quantitative or partially frustrated ESIPT process or deprotonation of the excited species. Protonation studies revealed that pyridine substitution triggered a strong increase of quantum yield in the solution state for the protonated species owing to favorable quinoidal stabilization. These attractive features led to the development of a second series of dyes with alkyl or aryl pyridinium moieties showing strong tunable solution/solid fluorescence intensity. For each series, ab initio calculations helped rationalize and ascertain their behavior in the excited state and the nature of the emission observed by the experimental results.

In quasi-two-dimensional (quasi-2D) perovskite films, carriers transport in the cascade structural systems involving various quantum wells (QWs) n, but their efficiency is limited by the severe nonradiative recombination within plentiful n = 1, 2, 3 domains induced by traditional ammonium bromide passivation. Here, we fabricate the quasi-2D films with the elimination of n = 1, 2, 3 domains by introducing the ionic liquid n-butylamine acetate (BAAc) instead of n-butylamine hydrobromide (BABr), which increases the photoluminescence quantum yield (PLQY) and lowers the surface roughness of films. Due to the anion exchange between BAAc and methylamine hydrobromide (MABr), BAAc exhibits a sole passivation effect on methylamine-based perovskites. As a result, the ionic liquid-derived perovskite light-emitting diodes (PeLEDs) display blue emission at 479 nm and show significantly improved performance on external quantum efficiency (EQE) and luminance. Our finding provides insights into the passivating effect of ionic liquid on quasi-2D perovskites and will benefit fabricating PeLEDs with enhanced performance.

Three A-π-A or D-π-D perylene diimide (PDI) derivatives with varied groups on π-conjugate were synthesized and characterized. The photophysical properties of these compounds were systematically studied by spectral experiments and density functional theory calculations. All compounds displayed intense absorption bands at 300-800 nm wavelengths. However, diverse groups on the π-conjugate influenced the UV-vis absorption. Electron-withdrawing groups on PDI-2 caused a slight red shift at the 350-400 nm wavelength and a blue shift after 400 nm wavelength. At the same time, the electron-donating substituents on PDI-3 caused an obvious red shift of this band. These PDI derivatives exhibited emission in solution at room temperature (λem = 500-850 nm). The quantum yield of PDI-3 decreased, while the electron-donating substituents were introduced to the π-conjugated motifs. However, the quantum yield of PDI-2 increased when electron-withdrawing substituents were introduced to the π-conjugated motifs. In addition, PDI-1 and PDI-2 exhibited broad triplet transient absorption in the visible region. These photophysical properties could help us to understand the relationship between structure and photophysical properties of perylene diimide derivatives and exploit more original perylene diimide-based optical functional materials.

Acridone and its derivatives have potential application as emitters for highly efficient blue organic light-emitting diodes (OLEDs). In this paper, we demonstrated ultrafast access of a solvent-independent singlet-triplet equilibrium state in acridone solutions by using femtosecond time-resolved spectroscopy. Our spectral data show that due to highly effective forward and reverse intersystem crossing (both kISC and krISC over 1010 s-1), a singlet-triplet equilibrium state is always populated in acridone in all solvents studied. However, the lifetimes of the equilibrium state varied a lot in different solvent environments and the final decay pathway of this state can switch between high quantum yield fluorescence emission and further internal conversion to the lowest triplet state. These findings provide direct experimental evidence to understand the distinct photophysical behaviors of acridone and also provide guidance for further design of acridone and its derivatives as blue OLED emitters.

Indium phosphide (InP) nanocrystals are emerging as an alternative to heavy metal containing nanocrystals for optoelectronic applications but lag behind in terms of synthetic control. Herein, luminescent wurtzite InP nanocrystals with narrow size distribution were synthesized via a cation exchange reaction from hexagonal Cu3P nanocrystals. A comprehensive surface treatment with NOBF4 was performed, which removes excess copper while generating stoichiometric In/P nanocrystals with fluoride surface passivation. The attained InP nanocrystals manifest a highly resolved absorption spectrum with a narrow emission line of 80 meV, and photoluminescence quantum yield of up to 40%. Optical anisotropy measurements on ensemble and single particle bases show the occurrence of polarized transitions directly mirroring the anisotropic wurtzite lattice, as also manifested from modeling of the quantum confined electronic levels. This shows a green synthesis path for achieving wurtzite InP nanocrystals with desired optoelectronic properties including color purity and light polarization with potential for diverse optoelectronic applications.

Coumarins are bioactive molecules that often serve as defenses in plant and animal systems, and understanding their fundamental behavior is essential for understanding their bioactivity. Aesculetin (6,7-dihydroxycoumarin) has recently attracted attention due to its ability to act as an antioxidant, but little is known about its photophysical properties. The fluorescence lifetimes of its neutral and anion form in water are 19 ± 2 ps and 2.3 ± 0.1 ns, respectively. Assuming the short lifetime of the neutral is determined by ESPT, we estimate kPT ~ 5 × 1010 s–1. Using steady-state and time-resolved fluorescence spectroscopy, we determine its ground and excited-state $${\text{p}}{K}_{a1}$$ to be 7.3 and –1, respectively, making it one of the strongest photoacids of the natural coumarins. Aesculetin exhibits a strong pH dependence of the relative fluorescence quantum yield becoming much more fluorescent above $${\text{p}}{K}_{a1}$$ . The aesculetin anion $${\text{has}}$$ slightly photobasic character. We also report that aesculetin forms a fluorescent catechol-like complex with boric acid, and this complex has a $${\text{p}}{K}_{c}$$ of 5.6.

Compared with red and green organic light-emitting diodes (OLEDs), blue is the bottleneck that restricts the wide development of OLEDs from being the next-generation technology for displays and lighting. As a new type of emitter, a Ce(III) complex shows many satisfactory advantages, such as a short excited-state lifetime, 100% theoretical exciton utilization efficiency, and tunable emission color. Herein we synthesized three heteroleptic Ce(III) complexes Ce(TpMe2)2(dtfpz), Ce(TpMe2)2(dmpz), and Ce(TpMe2)2(dppz) with the hydrotris(3,5-dimethylpyrazolyl)borate (TpMe2) main ligand and different substituted pyrazole ancillary ligands, namely, 3,5-di(trifluomethyl)pyrazolyl (dtfpz), 3,5-dimethylpyrazolyl (dmpz), and 3,5-diphenylpyrazolyl (dppz), and studied their structures and luminescence properties. All the Ce(III) complexes exhibited a near-unity photoluminescence quantum yield both in solution and as a powder with maximum emission wavelengths in the range of 450-486 nm. The OLED employing Ce(TpMe2)2(dppz) as the emitter showed the best performance, including a turn-on voltage, maximum luminance, and external quantum efficiency of 3.2 V, 29 200 cd m-2, and 12.5%, respectively.

Hybrid upconversion nanosystems have been reported to improve the low absorption efficiency of lanthanide-doped upconversion nanoparticles (UCNPs). However, the low quantum yield and poor photostability of NIR dyes pose challenges for practical uses. Here, we introduce a bulky moiety, 4-(1,2,2-triphenylvinyl)-1,1'-biphenyl (TPEO), to enhance its quantum yield by suppressing the bond rotation and improve the stability by deactivating the photoinduced oxidization. Compared with the conventional IR806, the formed NIR dye, TPEO-Cy, has been characterized to deliver three times higher quantum yield and seven times better photostability. Moreover, we take advantage of the strong affinity of sulfonate chains on the TPEO-Cy to bind to the surface of UCNPs. Taking together the synergistic effect, we have achieved a 242-fold upconversion emission enhancement over the benchmark of IR806-sensitized system and an ∼800 000-fold increase than the bare UCNPs. Our design of the NIR dyes suggests a new scope to search for more efficient upconversion nanohybrids.

With phenoxazine (PXZ) as the electron donor and perylene-3,4-dicarboximide (PMI) as the electron acceptor, we prepared a compact, orthogonal electron donor-acceptor dyad (PMI-PXZ) to study the spin-orbit charge transfer-induced intersystem crossing (SOCT-ISC). A weak charge transfer (CT) absorption band, due to S0 → 1CT transition, was observed (e = 2840 M-1 cm-1 at 554 nm, FWHM: 2850 cm-1), which is different from that of the previously reported analogue dyad with phenothiazine as the electron donor (PMI-PTZ), for which no CT absorption band was observed. A long-lived triplet state was observed (lifetime τT = 182 μs) with nanosecond transient absorption spectroscopy, and the singlet oxygen quantum yield (ΦΔ = 76%) is higher than that of the previously reported analogue dyad PMI-PTZ (ΦΔ = 57%). Ultrafast charge separation (ca. 0.14 ps) and slow charge recombination (1.4 ns) were observed with femtosecond transient absorption spectroscopy. With time-resolved electron paramagnetic resonance spectroscopy (TREPR), we confirmed the SOCT-ISC mechanism, and the electron spin polarization phase pattern of the triplet-state TREPR spectrum is (e, e, a, e, a, a), which is dramatically different from that of PMI-PTZ (a, e, a, e, a, e), indicating that the triplet-state TREPR spectrum of a specific chromophore in the electron donor-acceptor dyads is not only dependent on the geometry of the dyads but also dependent on the structure of the electron donor (or acceptor). Even one-atom variation in the donor structure may cause significant influence on the electron spin selectivity of the ISC of the electron donor-acceptor dyads.

Hydrogen peroxide (H2O2) is one of the most important industrial oxidants. In principle, photocatalytic H2O2 synthesis from oxygen and H2O using sunlight could provide a cleaner alternative route to the current anthraquinone process. Recently, conjugated organic materials have been studied as photocatalysts for solar fuels synthesis because they offer synthetic tunability over a large chemical space. Here, we used high-throughput experiments to discover a linear conjugated polymer, poly(3-4-ethynylphenyl)ethynyl)pyridine (DE7), which exhibits efficient photocatalytic H2O2 production from H2O and O2 under visible light illumination for periods of up to 10 h or so. The apparent quantum yield was 8.7% at 420 nm. Mechanistic investigations showed that the H2O2 was produced via the photoinduced stepwise reduction of O2. At longer photolysis times, however, this catalyst decomposed, suggesting a need to focus the photostability of organic photocatalysts, as well as the initial catalytic production rates.

It is generally accepted that while efficient suppression of molecular vibration is inevitable for purely organic phosphors due to their long emission lifetime in the regime of 1 ms or longer, fluorophores having a lifetime in the nanoseconds regime are not sensitive to collisional quenching. Here, however, we demonstrate that a fluorophore, 2,5-bis(hexyloxy)terephthaldehyde (BHTA), capable of having hydrogen bonding (H bonding) via its two aldehyde groups can have a largely enhanced (450%) fluorescence quantum yield (QY) in amorphous poly(acrylic acid) (PAA) matrix compared to its crystalline powder. We ascribe this enhanced QY to the efficient suppression of molecular vibrations via intermolecular H bonding. We confirm this feasibility by conducting temperature-dependent fluorescence emission intensity measurement. As gaseous phenol can intervene with the H bonding between BHTA and PAA, interestingly, BHTA embedded in PAA can selectively detect gaseous phenol by a sharp fluorescence emission intensity drop that is visibly recognizable by the naked eye. The results provide an insightful molecular design strategy for a fluorophore and fluorometric sensory system design for enhanced photoluminescence QY and convenient detection of various volatile organic compounds.

Exciplex or charge transfer blends can be emissive in a similar manner to thermally activated delayed fluorescent materials but without the requirement for covalent linkages. Exciplex blends have been mainly used in organic light-emitting diodes fabricated using thermal evaporation, which is in part due to the poor film forming properties of evaporable materials when processed from solution. In this paper, we report the synthesis of three oxadiazole derivatives designed to have good solubility and compare the properties with commercial 1,3-bis[2-(4-t-butylphenyl)-1,3,4-oxadiazo-5-yl]benzene (OXD-7). The acceptor materials have 4-(2-ethylhexyloxy)phenyl or 9,9-di-n-alkylfluoren-2-yl (where the alkyl groups are either n-propyl or n-hexyl) end groups as opposed to the 4-t-butylphenyl moieties of OXD-7. Neat films of the synthesized oxadiazole derivatives were found to have electron mobilities an order of magnitude higher than that of OXD-7. The oxadiazole derivatives were found to be miscible with the hole transporting 4,4′,4″-tris[phenyl(m-tolyl)amino]triphenylamine (m-MTDATA) with charge transfer emission from solution-processed films. The 4-(2-ethylhexyloxy)phenyl-oxadiazole derivative exhibited the best overall performance when blended with m-MTDATA, with the solution-processed films having a photoluminescence quantum yield of around 21 ± 3% and simple bilayer OLEDs having a maximum external quantum efficiency of 5.3 ± 0.3%.

International audience; A dimethyldihydropyrene (DHP) photochromic unit has been functionalized by donor (triphenylamine group) and acceptor (methyl-pyridinium) substituents. This compound was characterized by NMR, absorption and emission spectroscopies as well as cyclic voltammetry and its properties were rationalized by theoretical calculations. The incorporation of both electron donor and withdrawing groups on the photochromic center allows i) an efficient photo-isomerization of the system when illuminated at low energy (quantum yield: Фc-o = 13.3% at λex.= 660 nm), ii) the reversible and quantitative formation of two endoperoxyde isomers when illuminated under aerobic conditions at room temperature and iii) the storage and production of singlet oxygen. The photo-isomerization mechanism was also investigated by spin-flip TD-DFT (SF-TD-DFT) calculations.

Ortho-closo or ortho-nido-carborane-diphosphanes have been selected to prepare the heteroleptic cationic or neutral [Cu(N^N){(PPh2)2C2B10H10}]PF6 (1) and [Cu(N^N){(PPh2)2C2B9H10}] (2) [N^N = 2-(4-thiazolyl)benzimidazole], respectively. Complexes 1 and 2 display very different emissive behavior. Neutral complex 2 exhibits TADF (time activated delayed fluorescence) which has been studied both as powder and PMMA composite with similar ΔE(S1 – T1), τ(T1), and τ(S1) in both phases. Cationic complex 1 displays a much lower quantum yield than 2 and does not show TADF, but it exhibits a significant thermochromic luminescence, and its emission is very dependent on the medium. Theoretical studies show that metal–ligand (M–diphosphane) to ligand (L′, diimine) transitions, MLL′CT, are responsible of the transitions which originate the emissive properties, but with very different contribution of the copper center, carborane cluster, and diphosphane phenyl rings for 1 and 2., The authors also thank the Agencia Estatal de Investigación PID2019-104379RB-C21/AEI/10.13039/50110001103 and DGA-FSE (E07_20R) for financial support and to the Centro de Supercomputación de Galicia (CESGA) for providing access to the Finish Terrae supercomputer. A.A. appreciates the predoctoral contract award BES-2017-082997.

The syntheses of 3-formyl-4-hydroxybenzoic acid-derived ligands from ethylenediamine, diethylenetriamine, and triethylenetetramine are described. These ligands can further form hetero-binuclear complexes with transition metal ions (M2+ = Zn2+, Fe2+, Ni2+, Mn2+) and lanthanide ions (Ln3+ = Nd3+, Er3+, Yb3+). The spectroscopic properties were studied using near-infrared (NIR) luminescence emission spectra, fluorescence lifetime, and quantum yield. These hetero-nuclear complexes exhibited the characteristic lanthanide near-infrared luminescence in the solid state through energy-transfer from the chromophore to lanthanide ions. The d-block emission bands of transition metal ions in the solid state overlapped with f–f absorption bands of Yb(III), Er(III), or Nd(III), sensitizing the near-infrared luminescence of these hetero-binuclear complexes.

The bridging N atom in g-C3N4 structure plays a decisive role in photo-generated charge transfer because it usually confines photo-generated electrons and holes in each heptazine, thus leading to severe recombination. In this work, a kind of 2-aminoterephthalic acid-derived benzene ring group with rich π-electrons was considered to integrate with bridging N to break the above-mentioned confining effect. On the basis of density-functional theory calculations and experimental analysis, this 2-aminoterephthalic acid-derived bridging structure facilitated to draw photo-generated charge out of heptazine unit, and its polarized asymmetric structure promoted the directional transfer of photo-generated charge carriers across adjacent heptazines, thus efficiently reducing the recombination. Meanwhile, the 2-aminoterephthalic acid-derived bridging structure also reinforced the connectivity of heptazine units in g-C3N4 framework and led to high degree of polymerization, which thus extended the π-conjugated electronic system of g-C3N4 and modulated the band structure favoring photocatalytic hydrogen production. Consequently, a high photocatalytic H2-production activity of 24,595 μmol h−1 gcat-1 was achieved on the bridging regulated g-C3N4 under visible light, with an apparent quantum yield of 48.7% at 425 nm.

A new and innovative fluorescent structure was constructed on Cyclotriveratrylene affiliated to Dansyl chloride (DNSC) and was used to detect Cr (III) and Fe (III) among the various cations by using spectrofluorimetric method. The characterization of the new compound was carried out using the 1H-NMR, 13C-NMR, and ESI–MS techniques. The interaction and role of DNSC-CTV with cations was reviewed. A change in the spectra of absorption directed to the conclusion that there is substantial interaction of Cr (III) and Fe (III) with DNSC-CTV. Furthermore the interaction of the ligand DNSC-CTV with the metal ions Chromium (III) and Iron (III) showed quenching in the emission spectra. Quantum yield of the complexes were calculated and the stern volmer analysis was done to deduce the quenching mechanism of fluorescence to being either static or dynamic. The molecule DNSC-CTV was further studied with the help of computational methods such as molecular docking to study the binding interactions and properties of the molecule.

N,N,N',N'-Tetramethylethylenediamine (TMEDA) and ethylenediamine (EDA) were investigated in-depth in the ligand exchanges for water-soluble CdSe quantum dots (QDs). TMEDA could assist the phase transfer of QDs from apolar solvents to the aqueous solutions as stabilized by mercaptopropionic acid (MPA). We successfully maintained the stability of a series of MPA-capped QDs of different ligand densities for NMR characterizations in aqueous solutions. The proton NMR spectroscopies of MPA of the binding state were used to analyze the ligand densities on the surface of QDs, which were not explored in the past. The binding thermodynamics of the surface ligands of QDs, as analyzed using the Hill equation, demonstrated a positive promoting effect and possible interactions between ligands. EDA in the purification process underwent a spontaneous adsorption with two-stage thermodynamic behaviors as characterized by isothermal titration calorimetry. Due to the positive role of the already adsorbed ligands, excess EDA would further attach to the surface of QDs in the form of non-bonded physisorption, greatly improving the quantum yield (QY) of QDs, and the ligand of this part would almost not change the stability of QDs. We proposed a strategy for the preparation of aqueous QDs with a high QY, followed by fluorescence quenching-enhancement cycles caused by purification-adsorption operations. The strategy made it possible for the preparation of functional QDs with small molecules after purification operations. Kinetics of the sorption of ligands on the surface of QDs were determined by fluorescence spectroscopy. Modified pseudo-second-order kinetics after consideration of the ligand-ligand interaction effect could well analyze the kinetic data. This kinetic model had advantages over the previous ligand exchange model in terms of accuracy, reproducibility, and physical significance. Finally, we used the above strategy for the design of fluorescent QDs for bioimaging of lysosomes, mitochondria, and cancer cells. This work can simplify the preparation of multifunctional fluorescent QDs and avoid complicated ligand design.

The roles that chemical environment and viscosity play in the photochemical fate of molecules trapped in atmospheric particles are poorly understood. The goal of this work was to characterize the photolysis of 4-nitrocatechol (4NC) and 2,4-dinitrophenol (24DNP) in semisolid isomalt as a new type of surrogate for glassy organic aerosols and compare it to photolysis in liquid water, isopropanol, and octanol. UV/vis spectroscopy was used to monitor the absorbance decay to determine the rates of photochemical loss of 4NC and 24DNP. The quantum yield of 4NC photolysis was found to be smaller in an isomalt glass (2.6 × 10-6) than in liquid isopropanol (1.1 × 10-5). Both 4NC and 24NDP had much lower photolysis rates in water than in organic matrices, suggesting that they would photolyze more efficiently in organic aerosol particles than in cloud or fog droplets. Liquid chromatography in tandem with mass spectrometry was used to examine the photolysis products of 4NC. In isopropanol solution, most products appeared to result from the oxidation of 4NC, in stark contrast to photoreduction and dimerization products that were observed in solid isomalt. Therefore, the photochemical fate of 4NC, and presumably of other nitrophenols, should depend on whether they undergo photodegradation in a liquid or semisolid organic particle.

Full-color emissive carbon dots (CDs) hold a great promise for various applications, especially in light emitting diodes (LEDs). However, the existing synthetic routes for CDs are carried out in solutions, which suffer from low yields, high pressures, various byproducts, large amounts of waste solvents, and complicated photoluminescence (PL) origins. Therefore, it is necessary to explore large scale synthesis of CDs with high quantum yield (QY) across the entire visible range from a single carbon source by a solvent-free method. In this work, a series of CDs with tunable PL emission from 442 to 621 nm, QY of 23%–56%, and production yield within 34%–72%, are obtained by heating o-phenylenediamine with the catalysis of KCl. Detailed characterizations identify that, the differences between these CDs with respect to the graphitization degree, graphitic nitrogen content, and oxygen-containing functional groups, are responsible for their distinct optical properties, which can be modulated by controlling the deamination and dehydrogenation processes during reactions. Blue, green, yellow, red emissive films, and LEDs are prepared by dispersing the corresponding CDs into polyvinyl alcohol (PVA). All types of white LEDs (WLEDs) with high colorrendering- index (CRI), including warm WLEDs, standard WLEDs, and cool WLEDs, are also fabricated by mixing the red, green, and blue emissive CDs into PVA matrix by the appropriate ratios.

Shortwave infrared (SWIR)-emitting small molecules are desirable for biological imaging applications. In this study, four novel pentamethine indolizine cyanine dyes were synthesized with N,N-dimethylaniline-based substituents on the indolizine periphery at varied substitution sites. The dyes are studied via computational chemistry and optical spectroscopy both in solution and when encapsulated. Dramatic spectral shifts in the absorption and emission spectrum wavelengths with added donor groups are observed. Significant absorption and emission with an emissive quantum yield as high as 3.6% in the SWIR region is possible through the addition of multiple donor groups per indolizine.

Three V-shaped host molecules with a cyclohexane linker were successfully synthesized for thermally activated delayed fluorescence organic light-emitting diodes (TADF-OLEDs). The unipolar host molecules, BBCzC and BTDC, contained two 9-phenyl-9H-3,9'-bicarbazole (PBCz) moieties and two 2,12-di-tert-butyl-7-phenyl-5,9-dioxa-13b-boranaphtho[3,2,1-de]anthracene (PDBNA) moieties, respectively. BCzTC, a bipolar host molecule, consisted of a donor unit, PBCz, and an acceptor unit, PDBNA, connected by a cyclohexane linker. Three host molecules showed good solubility in various organic solvents, making them suitable for solution processing. Among the solution-processed green TADF-OLEDs using three host molecules and a green TADF emitter, the one with BCzTC showed the highest external quantum efficiency of up to 30% with a high power efficiency of 71 lm W-1 and a current efficiency of 102 cd A-1. Compared with BBCzC and BTDC, BCzTC exhibited a relatively high photoluminescence quantum yield (PLQY), an excellent balance in hole and electron transport properties in the emitting layer, and more efficient energy transfer to the emitter, giving such an excellent device performance.

Semiconducting polymer dots (Pdots) have emerged as versatile probes for bioanalysis and imaging at the single-particle level. Despite their utility in multiplexed analysis, deep blue Pdots remain rare due to their need for high-energy excitation and sensitivity to photobleaching. Here, we describe the design of deep blue fluorophores using structural constraints to improve resistance to photobleaching, two-photon absorption cross sections, and fluorescence quantum yields using the hexamethylazatriangulene motif. Scanning tunneling microscopy was used to characterize the electronic structure of these chromophores on the atomic scale as well as their intrinsic stability. The most promising fluorophore was functionalized with a polymerizable acrylate handle and used to give deep-blue fluorescent acrylic polymers with Mn > 18 kDa and Đ < 1.2. Nanoprecipitation with amphiphilic polystyrene-graft-(carboxylate-terminated poly(ethylene glycol)) gave water-soluble Pdots with blue fluorescence, quantum yields of 0.81, and molar absorption coefficients of (4 ± 2) × 108 M-1 cm-1. This high brightness facilitated single-particle visualization with dramatically improved signal-to-noise ratio and photobleaching resistance versus an unencapsulated dye. The Pdots were then conjugated with antibodies for immunolabeling of SK-BR3 human breast cancer cells, which were imaged using deep blue fluorescence in both one- and two-photon excitation modes.

Herein, we report the synthesis and properties of a [6,6] hollow bilayer cylindrical nanoring (HBCNR) from a planar macrocycle via a Diels-Alder and Yamamoto coupling reaction. The fluorescence quantum yield of HBCNR was determined to be ΦF = 52%, which is four times higher than its precursor. In addition, its hollow nanoring configuration was also simulated by theoretical studies, and the tension energy was estimated to be 47.1 kcal/mol.

A highly stable fluorescent terbium MOF (Tb4(paip)6·1.2H2O, paip = 5-(1H-pyrazole-4-yl)isophthalate) showing a sharp green emission (545 nm) and a quantum yield of 21.0% was successfully synthesized. This compound is shown to be a recyclable sensor for detecting picric acid in aqueous solution with both high sensitivity and selectivity, attributed to the electron transfer quenching mechanism.

Organic–inorganic hybrid metal halides have attracted intensive attention because of their unique electronic structure and solution processability. They have a rigid micro/nano-structure and heavy atom effect, which has obvious advantages in promoting organic room temperature phosphorescence (RTP). However, the toxicity of heavy metals has limited their further development. Herein, two metal-free 2D layered ammonium halides, homopiperonylammonium bromide and chloride (HLB and HLC), are described for the first time. Their layered structure consists of rigid inorganic ammonium halide laminates and neatly stacked organic layers. The rigid laminates and external heavy atom effect of halogen atoms make HLB and HLC produce green RTP. When phosphor guests with different triplet energies are doped into HLB, HLC, or phenylethylamine salt hosts, effective full-color and even white ultra-long RTP with phosphorescence quantum yield up to 18.7% and lifetime up to 1.7 s is realized through energy transfer between the host and guest. Due to the simple solution synthesis, 10 g-level doped layered organic ammonium halides with the same phosphorescence properties can be easily obtained. The information ink based on these doped halides and non-toxic ethanol solvent can form various patterns on filter paper. The fluorescence and phosphorescence of these patterns are sensitive to the excitation wavelength and acid–base vapor. Consequently, they can be applied to multiple complex anti-counterfeiting and fluorescence/phosphorescence dual-mode chemical sensors., A kind of metal-free organic ammonium halides characterized by a unique 2D layered structure show colorful ultralong phosphorescence. Phosphorescent quantum yield (up to 19%) and lifetime (up to 1.7 s) can be tuned by doping with different phosphors.

Platinum(II) compounds were synthesized with both chelate cyclometalated ligands and chelate diphosphine ligands. The cyclometalated ligands include phenylpyridine and a benzothiophene-containing ligand. The three new benzothiophene compounds were characterized by nuclear magnetic resonance (NMR) spectroscopy, high-resolution mass spectrometry (HR-MS), and photophysical measurements. In the case of one compound, L1-DPPM, the structure was determined by single crystal X-ray diffraction. The structural coherence of the noncrystalline emissive solid state was measured by X-ray total scattering real space pair distribution function analysis. Quantum yield values of all of the platinum compounds measured in the solid state and in PMMA films were much greater than in solution.

Carbon nanodots (CDs) based fluorescent nanoprobes have recently drawn much attention in chemo-/bio-sensing and bioimaging. However, it is still challenging to integrate the colorimetric and fluorometric dual readouts into a single CD. Herein, novel hybrid CDs (HCDs) are prepared by a simple microwave-assisted reaction of citric acid (CA), branched polyethyleneimine (BPEI) and potassium thiocyanate (KSCN). As-prepared HCDs show extraordinary properties, including excitation-dependent emission, satisfactory fluorescence quantum yield (46.8%), excellent biocompatibility and optical stability. Significantly, the fluorescence intensity at 450 nm exhibits linear correlation over the Fe3+ concentration from 1 μmol/L to 150 μmol/L with a detection limit (LOD) of 52 nmol/L. Meanwhile, the solution color changes from colorless to orange, and the absorbance at 460 nm increased linearly with Fe3+ concentration ranging from 0.02 mmol/L to 5 mmol/L (LOD: 3.4 μmol/L). All the evidence illustrates that the HCDs can be conditioned for specific Fe3+ sensing with colorimetric and fluorometric dual readouts, which has also been verified with paper-based microchips. The possible mechanism is attributed to the specific interactions between surface functional groups on the HCDs and Fe3+. Additionally, the HCDs are successfully applied in sensing Fe3+ in wastewater and living cells, demonstrating its potential applications in future environment monitoring and disease diagnosis.

A series of poly(phenylene-vinylene)-based copolymers are synthesized using the Gilch method incorporating monomers with sterically bulky sidechains. The photochemical upconversion performance of these polymers as emitters are investigated using a palladium tetraphenyltetrabenzoporphyrin triplet sensitizer and MEH-PPV as reference. Increased incorporation of sterically bulky monomers leads to a reduction in the upconversion efficiency despite improved photoluminescence quantum yield. A phosphorescence quenching study indicates issues with the energy transfer process between the triplet sensitizer and the copolymers. The best performance with 0.18% upconversion quantum yield is obtained for the copolymer containing 10% monomer with bulky sidechains.

Triplet-triplet annihilation (TTA) upconversion has shown promising potentials in the augmentation of solar energy conversion. However, challenging issues exist in improving TTA upconversion efficiencies in solid-states, one of which is the back energy transfer from upconverted singlet annihilators to sensitizers, resulting in decreasing upconversion emission. Here we present a light-harvesting molecular wire consisting of dendrons with 9,10-diphenylanthracene derivatives (DPAEH) at the periphery and p-phenylene ethynylene oligomers (PPE) as the wire core. The peripheral DPAEH antenna funnels singlet excitonic energy to the wire on a 12 ps time scale. Incorporating the molecular wire into the TTA upconversion solid consisting of the DPAEH annihilator and the porphyrin sensitizer evidently improves the upconversion quantum yield from 1.5% to 2.7% upon 532 nm excitation by suppressing the back energy transfer from the singlet annihilator to the sensitizer. This finding offers a potential route to use a singlet energy light-harvesting architecture for enhancing TTA upconversion.