Search

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.

Strategic incorporation of a meta dimethylamino (-NMe2 ) group on the conformationally locked green fluorescent protein (GFP) model chromophore (m-NMe2 -LpHBDI) has drastically altered molecular electronic properties, counterintuitively enhancing fluorescence of only the neutral and cationic chromophores in aqueous solution. A ~200-fold decrease in fluorescence quantum yield of m-NMe2 -LpHBDI in alcohols (e.g., MeOH, EtOH, and 2-PrOH) supports this GFP-derived compound as a fluorescence turn-on water sensor, with large fluorescence intensity differences between H2 O and ROH emissions in various H2 O/ROH binary mixtures. A combination of steady-state electronic spectroscopy, femtosecond transient absorption, ground-state femtosecond stimulated Raman spectroscopy (FSRS), and quantum calculations elucidates an intermolecular hydrogen-bonding chain between a solvent -OH group and the chromophore phenolic ring -NMe2 and -OH functional groups, wherein fluorescence differences arise from an extended hydrogen-bonding network beyond the first solvation shell, as opposed to fluorescence quenching via a dark twisted intramolecular charge transfer state. The absence of a meta-NMe2 group twisting coordinate upon electronic excitation was corroborated by experiments on control samples without the meta-NMe2 group or with both meta-NMe2 and para-OH groups locked in a six-membered ring. These deep mechanistic insights stemming from GFP chromophore scaffold will enable rational design of organic, compact, and environmentally friendly water sensors.

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.

Recent advances in sustainable optoelectronics including photovoltaics, light-emitting diodes, transistors, and semiconductors have been enabled by π-conjugated organic molecules. A fundamental understanding of light-matter interactions involving these materials can be realized by time-resolved electronic and vibrational spectroscopies. In this Minireview, the photoinduced mechanisms including charge/energy transfer, electronic (de)localization, and excited-state proton transfer are correlated with functional properties encompassing optical absorption, fluorescence quantum yield, conductivity, and photostability. Four naturally derived molecules (xylindein, dimethylxylindein, alizarin, indigo) with ultrafast spectral insights showcase efficient energy dissipation involving H-bonding networks and proton motions, which yield high photostability. Rational design principles derived from such investigations could increase the efficiency for light harvesting, triplet formation, and photosensitivity for improved and versatile optoelectronic performance.

A strategy of chiral donor-acceptor copolymerization is proposed to develop chiral nonconjugated polymers with thermally activated delayed fluorescence (TADF). Based on this strategy, two pairs of chiral polymers ( R , R )-/( S , S )- pTpAcDPS and ( R , R )-/( S , S )- pTpAcBP were synthesized. The alternating copolymerization of the chiral donors and acceptors could effectively separate the frontier molecular orbitals, which made the polymers show small Δ E ST of 0.01-0.03 eV and efficient TADF properties. Moreover, the polymers also showed the quantum yield of up to 92% and the circularly polarized luminescence. The solution-processed circularly polarized organic light-emitting diodes showed circularly polarized electroluminescence signals with high external quantum efficiencies of up to 22.1% and maximum luminance of up to 34350 cd m -2 . This is the first report of CP-OLEDs based on chiral TADF polymer, which provides a useful and valuable guidance for the development of high-efficiency CPEL polymers.

In this study, we have demonstrated a two-legged, upright molecular design method for monochromatic and bright red luminescent LnIII -silica nanomaterials. A novel EuIII -silica hybrid nanoparticle was developed by using a doubly binding TPPO-Si(OEt)3 (TPPO: triphenyl phosphine oxide) linker. The TPPO-Si(OEt)3 was confirmed by 1 H, 31 P, 29 Si NMR spectroscopy and single-crystal X-ray analysis. Luminescent Eu(hfa)3 and Eu(tfc)3 moieties (hfa: hexafluoroacetylacetonate, tfc: 3-(trifluoromethylhydroxymethylene)camphorate) were fixed onto TPPO-Si(OEt)3 -modified silica nanoparticles, producing Eu(hfa)3 (TPPO-Si)2 -SiO2 and Eu(tfc)3 (TPPO-Si)2 -SiO2 , respectively. Eu(hfa)3 (TPPO-Si)2 -SiO2 exhibited the higher intrinsic luminescence quantum yield (93 %) and longer emission lifetime (0.98 ms), which is much larger than those of previously reported EuIII -based hybrid materials. Eu(tfc)3 (TPPO-Si)2 -SiO2 showed an extra-large intrinsic emission quantum yield (54 %), although the emission quantum yield for the precursor Eu(tfc)3 (TPPO-Si(OEt)3 )2 was found to be 39 %. These results confirmed that the TPPO-Si(OEt)3 linker is a promising candidate for development of EuIII -based luminescent materials.

The luminophore Ru(bpy)2 (dcbpy)2+ (bpy=2,2'-bipyridine; dcbpy=4,4'-dicarboxy-2,2'-bipyridine) is covalently linked to a chitosan polymer; crosslinking by tripolyphosphate produced Ru-decorated chitosan fibers (NS-RuCh), with a 20 : 1 ratio between chitosan repeating units and RuII chromophores. The properties of the RuII compound are unperturbed by the chitosan structure, with NS-RuCh exhibiting the typical metal-to-ligand charge-transfer (MLCT) absorption and emission bands of RuII complexes. When crosslinks are made in the presence of IrO2 nanoparticles, such species are encapsulated within the nanofibers, thus generating the IrO2 ⊂NS-RuCh system, in which both RuII photosensitizers and IrO2 water oxidation catalysts are within the nanofiber structures. NS-RuCh and IrO2 ⊂NS-RuCh have been characterized by dynamic light scattering, scanning electronic microscopy, and energy-dispersive X-ray analysis, which indicated a 2 : 1 ratio between RuII chromophores and IrO2 species. Photochemical water oxidation has been investigated by using IrO2 ⊂NS-RuCh as the chromophore/catalyst assembly and persulfate anions as the sacrificial species: photochemical water oxidation yields O2 with a quantum yield (Φ) of 0.21, definitely higher than the Φ obtained with a similar solution containing separated Ru(bpy)3 2+ and IrO2 nanoparticles (0.05) or with respect to that obtained when using NS-RuCh and "free" IrO2 nanoparticles (0.10). A fast hole-scavenging process (rate constant, 7×104 s-1 ) involving the oxidized photosensitizer and the IrO2 catalyst within the IrO2 ⊂NS-RuCh system is behind the improved photochemical quantum yield of IrO2 ⊂NS-RuCh.

A novel hybrid photocatalyst composed of nano hollow carbon spheres (NCS) and graphitic carbon nitride (CN) curly nanosheets has been prepared by the calcination of NCS precursor and freeze-dried urea. The optimized photocatalyst exhibits an efficient photocatalytic performance under visible light irradiation with the highest H 2 generation rate of 3612.3 μmol g -1 h -1 , leading to an apparent quantum yield of 10.04% at 420 nm, 5 times higher than the widely reported benchmark photocatalyst CN (2.01% AQY). The materials characterization shows that NCS-modified CN curly nanosheets can promote photoelectron transfer and suppress charge recombination through their special coupling interface and NCS as an electron acceptor, which significantly improves the photocatalytic efficiency. Thus, this study provides a new strategy for the design of highly-efficient photocatalyst, particularly suitable for polymeric materials to construct a totally metal free photocatalytic structure.

Thermally activated delayed fluorescence (TADF) materials with through-space charge transfers (CT) have attracted particularly interest recently. However, the slow reverse intersystem crossing (RISC) and radiative decay always limit their electroluminescence performances. Herein, TADF molecules with ortho-linked multiple donors-acceptor (ortho-Dn -A) motif are developed to create near-degenerate excited states for the reinforcement of spin-orbit coupling. The incorporation of both through-bond and through-space CT enlarges oscillator strength. The optimal ortho-D3 -A compound exhibits a photoluminescence quantum yield of ca. 100 %, a high RISC rate of 2.57×106 s-1 and a high radiative decay rate of 1.00×107 s-1 simultaneously. With this compound as the sensitizer, a TADF-sensitized-fluorescent organic light-emitting diode shows a maximum external quantum efficiency of 31.6 % with an ultrapure green Commission Internationale de L'Eclairage y coordinate value of 0.69.

The synthesis, characterization and photoluminescent properties of four cyclometalated (C N)-type gold(III) complexes bearing a bidentate diacetylide ligand, tolan-2,2'-diacetylide (tda), are reported. The complexes exhibit highly tunable excited state properties and show photoluminescence (PL) across the entire visible spectrum from sky-blue (λPL =493 nm) to red (λPL =675 nm) with absolute PL quantum yields (PLQY) of up to 75 % in solution, the highest PLQY found for any monocyclometalated Au(III) complex in solution. As a consequence of the use of the strongly rigidifying diacetylide bidentate ligand, a significant increase in the excited state lifetimes (τ0 =16-258 μs) was found in solution and in thin films. The complexes showed remarkable singlet oxygen generation in aerated solution with absolute singlet oxygen quantum yield (ϕ1Δ ) values reaching up to 7.5×10-5 and singlet oxygen lifetimes (τ01Δ ) in the range of 66-95 μs. Furthermore, the radiative and non-radiative rates of singlet oxygen were determined using the ϕ1Δ and τ01Δ values and correlations are drawn between the formation of singlet oxygen and its interaction with cyclometalated (C N) gold(III) complexes.

Highly efficient inorganic phosphors are crucial for solid-state lighting. In this paper, a new method of low-temperature self-reduction was used for preparing a highly efficient deep blue-emitting phosphor of Ca[B8 O11 (OH)4 ] : Eu2+ (CBH : Eu2+ ). The crystal structure, morphology, chemical state, and photoluminescence (PL) properties of the CBH : Eu2+ phosphor have been investigated. By using the screened hybrid function (HSE06), the band gap (Eg ) of CBH was calculated to be 7.48 eV, which is a necessary condition for achieving high quantum yield phosphors. The experiment results show that almost all the added raw materials of Eu3+ can be reduced to Eu2+ in CBH crystal under a non-reducing atmosphere. The CBH : Eu2+ phosphor shows a broad excitation spectrum centered at 277 and 327 nm in the range of 220 to 400 nm, and a narrow-band emission spectrum centered at 428 nm in the range of 400 to 500 nm, with a full width at half maximum (fwhm) of 42.35 nm. Under UV radiation, the CBH : 2 %Eu2+ exhibits high photoluminescence quantum yield (PLQY=95.0 %), high external quantum efficiency (EQE=31.1 %), and ultra-high color purity (97.6 %). The PL intensity of CBH : 2 %Eu2+ remains 62.6 % of the initial intensity at 150 °C. Finally, the white light-emitting diodes (WLED) fabricated by CBH : 2 %Eu2+ , excited by a 365 nm chip, presents outstanding performances with a luminous efficacy (LE) of 13.9 lm/W, a color rendering index (CRI) of 89.4, and a correlated color temperature (CCT) of 5825 K. The above results show that CBH : Eu2+ can be used as a promising blue phosphor for WLED. This new method of low-temperature self-reduction can be applied to design and prepare other new types of highly efficient phosphors.

Developing organic luminophores with unique capability of strong narrowband emission is both crucial and challenging for the further advancement of organic light-emitting diodes (OLEDs). Herein, a nanographitic fused-nonacyclic π-system (BSBS-N1), which was strategically embedded with multiple boron, nitrogen, and sulfur atoms, was developed as a new multi-resonance thermally activated delayed fluorescence (MR-TADF) emitter. Narrowband sky-blue emission with a peak at 478 nm, full width at half maximum of 24 nm, and photoluminescence quantum yield of 89 % was obtained with BSBS-N1. Additionally, the spin-orbit coupling was enhanced by incorporating two sulfur atoms, thereby facilitating the spin-flipping process between the excited triplet and singlet states. OLEDs based on BSBS-N1 as a sky-blue MR-TADF emitter achieved a high maximum external electroluminescence quantum efficiency of 21.0 %, with improved efficiency roll-off.

Solution phase room-temperature phosphorescence (RTP) from organic phosphors is seldom realized. Herein we report one of the highest quantum yield solution state RTP (ca. 41.8 %) in water, from a structurally simple phthalimide phosphor, by employing an organic-inorganic supramolecular scaffolding strategy. We further use these supramolecular hybrid phosphors as a light-harvesting scaffold to achieve delayed fluorescence from orthogonally anchored Sulforhodamine acceptor dyes via an efficient triplet to singlet Förster resonance energy transfer (TS-FRET), which is rarely achieved in solution. Electrostatic cross-linking of the inorganic scaffold at higher concentrations further facilitates the formation of self-standing hydrogels with efficient RTP and energy-transfer mediated long-lived fluorescence.

Recently graphene quantum dot (GQD) based nanohybrid materials have received much attention. Herein, a highly fluorescent biocompatible GQD and N-functionalized dithienopyrrole (DTP-PPD) modified nanohybrid system was fabricated (DTP-PPD-fn-GQD) for the first time. Modification resulted in stable fluorescence with a quantum yield of approximately 22% and 36 nm redshift compared to unmodified GQD. The apparent bandgap tuning along with fluorescence property changes was investigated by cyclic voltammetry measurements and density functional theory studies. This water-soluble system was then applied for the sensitive and selective detection of Pb2+ ions. As a result of a specific interaction towards Pb2+ ions, the fluorescence intensity was quenched. The detection limit is found to be 1.02 nM within the linear range of 3 to 30 nM. Finally, the feasibility of the developed probe was tested with real samples of water. Chemically modified GQDs are already widely exploited for Pb2+ sensing, whereas GQD/thiophene-based nanohybrid systems are less utilized. This newly developed nanohybrid of GQD (DTP-PPD-fn-GQD) has excellent fluorescence properties and bandgap tunability. Moreover, effective fluorometric sensing of Pb2+ ions in an aqueous medium is well investigated. This gives more insight into developing GQD-based highly promising nanohybrid colorimetric as well as fluorescent sensors.

Noble-metal-free composites with good photocatalytic property are of great interest. Here, CeO2 nanorods composites loaded with amorphous Fe(OH)3 cocatalyst were designed and prepared via a secondary water bath at 100 °C. The as-synthesized CeO2 /amorphous Fe(OH)3 composites exhibited superior light photocatalytic activities compared to pure CeO2 , especially the sample with a loading time of 60 min. The photocatalytic oxygen generation rate could reach to 357.2 μmol h-1 g-1 , and the average apparent quantum yield (AQY) was 24.67 %, which was a 5.5-fold increase compared to the CeO2 sample. The improvement of photocatalytic performance could be ascribed to three main reasons: First, loading the amorphous Fe(OH)3 enlarged the specific surface area and passivated the surface of the pristine CeO2 . Second, the amorphous Fe(OH)3 ,which acted as a cocatalyst, provided many active sites, and reduced the reaction activation energy. Thirdly, the maximum interface with intimate contact between CeO2 and amorphous Fe(OH)3 cocatalyst accelerated the photogenerated charge separation efficiency and thus improved the photocatalytic performance of CeO2 in photocatalytic water oxidation.

The simultaneous achievement of efficient photoluminescence quantum yield (PLQY) and horizontal orientation of a transition dipole moment (TDM) in thermally-activated delayed fluorescence (TADF) emitters remain a significant challenge toward the realization of high-performance organic light-emitting diodes (OLEDs). Herein, three TADF molecules, namely PQ1, PQ2, and PQ3, are composed of electron-accepting (A) tetrabenzo[a,c]phenazine (TBPZ) and electron-donating (D) phenoxazine (PXZ) units are designed and characterized. The combined effects of planar acceptor manipulation and high steric hindrance between D and A units endow high molecular rigidity that suppresses nonradiative decay of the excitons with improved PLQYs. Particularly, the well-aligned excited states involving a singlet and a triplet charge-transfer excited states and a localized excited triplet state in PQ3 enhances the reverse intersystem crossing rate constant (kRISC) with a short delay lifetime (τd). Moreover, PQ3 exhibited a completely horizontal orientation of the TDM in the film, attributed to the expansion of the π-conjugated acceptor plane with 4-cyanophenyl groups incorporation. Consequently, the orange-red OLED based on PQ3 displays a maximum external EL quantum efficiency (EQE) of 27.4 % with a well-suppressed EL efficiency roll-off. These results provide a feasible design strategy to construct efficient orange-red TADF emitters by concurrently attaining high EQE and horizontal TDM orientation through rational design engineering.

A multi-environment computational approach is proposed to study the modulation of the emission behavior of the triphenylamine (Z)-4-benzylidene-2-methyloxazol-5(4H)-one (TPA-BMO) molecule [Tang et al., J. Phys. Chem. C 119, 21875 (2015)]. We aim at (1) proposing a realistic description of the molecule in several environments (solution, aggregate, polymer matrix), (2) modelling its absorption and emission properties, and (3) providing a qualitative understanding of the experimental observations by highlighting the photophysical phenomena leading to the emission modulation. To this purpose, we rely on (TD-)DFT calculations and classical Molecular Dynamics simulations, but also on the hybrid ONIOM QM/QM' approach and the in situ chemical polymerization methodology. In low-polar solvents, the investigation of the potential energy surfaces and the modulation of the emission quantum yield can be attributed to possible photophysical energy dissipation caused by low-frequency vibrational modes. In the aggregate and in the polymer matrix, the emission modulation can be qualitatively interpreted in terms of the possible restriction of the intramolecular vibrations. For these two systems, our study highlights that a careful modelling of the environment is far from trivial but is fundamental to model the optical properties of the fluorophore.

We present a method for atomically precise nanocluster synthesis. As an illustration, we introduced the reducing-ligand induction combined method and synthesized a novel nanocluster, which was determined to be Au28 (SCH2 Ph-t Bu)22 with the same number of gold atoms as existing Au28 (SR)20 nanoclusters but different ligands (hetero-composition-homo-size). Compared with the latter, the former has distinct properties and structures. In particular, a novel kernel evolution pattern is reported, i.e., the quasi-linear growth of Au4 -tetrahedron by sharing one vertex and structural features, including a tritetrahedron kernel with two bridging thiolates and two Au6 (SCH2 Ph-t Bu)6 hexamer chair-like rings on the kernel surface were also first reported, which endow Au28 (SCH2 Ph-t Bu)22 with the best photoluminescence quantum yield among hydrophobic thiolated gold nanoclusters so far, probably due to the enhanced charge transfer from the bi-ring to the kernel via Au-Au bonds.

Herein, we reported an ultrapure blue multiple-resonance-induced thermally activated delayed fluorescence (MR-TADF) material (ν-DABNA-O-Me) with a high photoluminescence quantum yield and a large rate constant for reverse intersystem crossing. Because of restricted π-conjugation of the HOMO rather than the LUMO induced by oxygen atom incorporation, ν-DABNA-O-Me shows a hypsochromic shift compared to the parent MR-TADF material (ν-DABNA). An organic light-emitting diode based on this material exhibits an emission at 465 nm, with a small full-width at half-maximum of 23 nm and Commission Internationale de l'Eclairage coordinates of (0.13, 0.10), and a high maximum external quantum efficiency of 29.5 %. Moreover, ν-DABNA-O-Me facilitates a drastically improved efficiency roll-off and a device lifetime compared to ν-DABNA, which demonstrates significant potential of the oxygen atom incorporation strategy.

The halogenido stannates(II) [BMIm][Sn$_{3}$Cl$_{7}$] and [BMIm][Sn$_{4}$4Br$_{9}$] are obtained by ionic-liquid-based synthesis with SnX$_{2}$ and [BMIm]X (X=Cl, Br; [BMIm]=1-butyl-3-methylimidazolium) near room temperature (45–50 °C). Both form colorless, moisture-sensitive crystals and exhibit layered anionic networks. [BMIm][Sn$_{3}$3Cl$_{7}$7] contains “horseshoe”-like $_{∞}$$^{1}$(SnCl$_{171}$Cl$_{2/2}$) chains that are linked via [SnCl$_{3}$]− anions to $_{∞}$$^{2}$[Sn$_{3}$Cl$_{7}$]− zigzag-planes. [BMIm][Sn$_{4}$Br$_{9}$] contains a complex $_{∞}$$^{2}$[Sn$_{4}$Br$_{9}$]− network with altogether four different crystallographic Sn$_{2+}$ sites and different coordination. For comparison with these complex halogenido stannates(II), PbCl$_{2}$/PbBr$_{2}$ are reacted with similar conditions, which, however, only results in [BMIm][PbCl$_{3}$] containing $_{∞}$$^{1}$[PbCl$_{3}$]− chains. Beside the crystal structures, the thermal and optical properties are examined and feature certain emission of visible light for all title compounds at room temperature. Whereas the quantum yields of [BMIm][Sn$_{4}$Br$_{9}$9] (3 %) and [BMIm][PbCl$_{3}$] (21 %) are low, [BMIm][Sn$_{3}$Cl$_{7}$] shows surprisingly efficient photoluminescence with a quantum yield of 46 %.

Organic ultralong room temperature phosphorescence (OURTP) materials with photophysical properties sensitive to external stimulus are highly attractive for advanced applications. However, most OURTP molecules are in crystal and OURTP materials with good practicability and stimulus-responsive character are hard to be achieved. Here, we report, for the first time, the highly efficient, ultralong-lived and deep-blue OURTP materials by simply doping boron phosphor into cyanuric acid host. Thus constructed host-guest OURTP composites with abundant and tunable H-bond network are highly stable in air with ultralong lifetime of 5.08 s at room temperature, and more interestingly, are sensitive to water, which can strength the H-bond network to significantly enhance OURTP quantum yield from 16.1% to 37.6%. With the extraordinary water-responsive OURTP, anti-counterfeiting paper was facilely prepared for water-jet printing and the jet-printed high-resolution OURTP patterns can be easily erased by solvent fuming for another printing/erasing cycle with high reversibility.

As an alternative strategy for H2 production under ambient conditions, solar-driven lignocellulose-to-H2 conversion provides a very attractive approach to store and utilize solar energy sustainably. Exploiting efficient photocatalyst for photocatalytic lignocellulose-to-H2 conversion is of huge significance and remains the key challenge for development of solar H2 generation from lignocellulose. Herein, 2D-2D MoS2 /TiO2 photocatalysts with large 2D nanojunction were constructed for photocatalytic lignocellulose-to-H2 conversion. In this smart structure, the 2D nanojunctions acted as efficient channel for charge transfer from TiO2 to MoS2 to improve charge separation efficiency and thus enhance photocatalytic lignocellulose-to-H2 conversion activity. The 2 % MoS2 /TiO2 photocatalyst showed the highest photocatalytic lignocellulose-to-H2 conversion performance with the maximal H2 generation rate of 201 and 21.4 μmol h-1 g-1 in α-cellulose and poplar wood chip aqueous solution, respectively. The apparent quantum yield at 380 nm reached 1.45 % for 2 % 2D-2D TiO2 /MoS2 photocatalyst in α-cellulose aqueous solution. This work highlights the importance of optimizing the interface structures of photocatalyst for solar-driven lignocellulose-to-H2 conversion.

The design and synthesis of nitrogen-doped aromatic belts with conjugated structures still remain a challenge. Here, we report the first nitrogen-doped aromatic belt with a [6]cycloparaphenylene skeleton, which is conveniently synthesized from the easily available calix[3]carbazole. The aromatic belt has a rigid conjugated structure and deep cavity, and it can encapsulate one dichloromethane both in solution and in the solid state. Interestingly, the aromatic belt shows strong green fluorescence with a quantum yield of 0.39 and exhibits a narrow HOMO-LUMO energy gap of 2.02 eV. The belt-shaped conjugated structure composed of three carbazole subunits has specific optoelectronic properties that will promote wide applications in supramolecular chemistry and materials science.

Fluorescence and phosphorescence are known as two kinds of fundamental optical signals, which have been used for myriad applications. Of particular note, simultaneous activation of stable fluorescence and long-lived room temperature phosphorescence (RTP) emission in aqueous phase remains a big challenge up to present. Herein, we prepare a kind of zinc-doped silica nanospheres (Zn@SiNSs) with fluorescence and RTP properties through a facile hydrothermal synthetic strategy. For the as-prepared Zn@SiNSs, the recombination of electrons and holes in defects and defect-stabilized excitons derived from oxygen vacancy/C=N bonds lead to the production of stable fluorescence and long-lived RTP (emission lasting for ~9 s, quantum yield (QY): ~33.6%, RTP lifetime: ~236 ms). In addition, the internal Si-O bonded networks and hydrophilic surface in Zn@SiNSs can reduce nonradiative decay to form self-protective RTP, and also provide high water solubility, excellent pH- and photo-stability.

The effects of defect states on the fluorescence (FL) and electrochemiluminescence (ECL) properties of graphite phase carbon nitride (g-CN) are systematically investigated for the first time. The g-CN nanosheets (CNNSs) obtained at different condensation temperatures are used as the study models. It can be found that all the CNNSs have two kinds of defect states, one is originated from the edge of CNNSs (labeled as CN-defect) and the other is attributed to the partially carbonization regions (labeled as C-defect). Both two kinds of defect states substantially affect the luminescent properties of CNNSs. Both the FL and ECL signals of CNNSs contain a band gap emission and two defect emissions. For the FL of CNNSs, decreasing the density of defect states can increase efficiently the FL quantum yield, while increasing the density of defect states can make the FL spectra red shift. For the ECL of CNNSs, increasing the density of CN-defect states and decreasing the density of C-defect states are greatly important to improve the ECL activity. This work provides a deep insight into the FL and ECL mechanisms of g-CN, and is of significance in tuning the FL and ECL properties of g-CN. Also, it will greatly promote the applications of CNNSs based on the FL and ECL properties.

Zero-dimensional metal halides have attracted much attention due to their attractive photoelectric properties. Here, we propose a new strategy of synthesizing metal halides crystals by recrystallization in water. The as-synthesized Cs2 InCl5 (H2 O)-orange crystals are dissolved and recrystallized in water (Cs2 InCl5 (H2 O)-blue), with its photoluminescence (PL) changing from orange to blue, both of which are derived from self-trapping excitons (STEs). The time-resolved photoluminescence (TRPL) spectrum of Cs2 InCl5 (H2 O)-blue shows that it has an ultralong lifetime up to milliseconds (τ=52.98 ms), which is expected to be applied in biological sensors. The photoluminescence quantum yield (PLQY) increases from 2.25% to 11.61% in the self-assembly process. By using a post-doping method, the PL of crystals turns into red when we introduce Mn2+ as dopant while there is no obvious change upon using a traditional solvent-thermal method. Recrystallization in water and post-doping provide a new perspective for the synthesis and doping of metal halides.

Bis(1‐(4‐tolyl)‐carboran‐2‐yl)‐(4‐tolyl)‐borane [(1‐(4‐MeC6H4)‐closo‐1,2‐C2B10H10‐2‐)2(4‐MeC6H4)B] (1), a new bis(o‐carboranyl)‐(R)‐borane was synthesised by lithiation of the o‐carboranyl precursor and subsequent salt metathesis reaction with (4‐tolyl)BBr2. Cyclic voltammetry experiments on 1 show multiple distinct reduction events with a one‐electron first reduction. In a selective reduction experiment the corresponding paramagnetic radical anion 1.− was isolated and characterized. Single‐crystal structure analyses allow an in‐depth comparison of 1, 1.−, their calculated geometries, and the S1 excited state of 1. Photophysical studies of 1 show a charge transfer (CT) emission with low quantum yield in solution but a strong increase in the solid state. TD‐DFT calculations were used to identify transition‐relevant orbitals., Stabilization via three‐coordinate boron allows the isolation of a paramagnetic radical anion of ortho‐carborane. A photophysical, electrochemical and crystallographic study backed by DFT calculations shines light on closo‐nido intermediate structures, charge transfer processes and electron accepting ability.

Anthracene-naphthalimide (An-NI) compact electron donor-acceptor dyads were prepared, in which the orientation and distance between the two subunits were varied by direct connection or with intervening phenyl linker. Efficient intersystem crossing (ISC) and long triplet state lifetime (ΦΔ =92 %, τT =438 μs) were observed for the directly connected dyads showing a perpendicular geometry (81°). This efficient spin-orbit charge transfer ISC (SOCT-ISC) takes 376 fs, inhibits the direct charge recombination (CR) to ground state (1 CT→S0 , takes 3.04 ns). Interestingly, efficient SOCT-ISC for dyads with intervening phenyl linker (ΦΔ =40 % in DCM) was also observed, although the electron donor and acceptor adopt almost coplanar geometry (dihedral angle: 15°). Time-resolved electron paramagnetic resonance (TREPR) spectroscopy shows that the electron spin polarization of the triplet state, i. e. the electron spin selectivity of ISC, is highly dependent on the dihedral angle and the linker. For the dyads showing weaker coupling between the donor and acceptors, the charge separation and the intramolecular triplet energy transfer are inhibited at 80 K (frozen solution), because both the 3 An and 3 NI states were observed and the ESP are same as compared to the native anthracene and naphthalimide, which unravel their origin. The dyads were used as triplet photosensitizers for triplet-triplet annihilation upconversion (TTA UC). High UC quantum yield (ΦUC =12.9 %) as well as a large anti-Stokes shift (0.72 eV) was attained by excitation into the CT absorption band.

The construction of solid-state fluorescent materials with high quantum yield and good processability is of vital importance in the preparation of organic light-emitting devices. Herein, a series of tetraphenylethylene (TPE)-based multicomponent emissive metallacages are prepared by the coordination-driven self-assembly of tetra-(4-pyridylphenyl)ethylene, cis-Pt(PEt3 )2 (OTf)2 and tetracarboxylic ligands. These metallacages exhibit good emission both in solution and in the solid state because the coordination bonds and aggregation restrict the molecular motions of TPE synergistically, which suppresses the non-radiative decay of these metallacages. Impressively, one of the metallacages achieves very high fluorescence quantum yield (ΦF =88.46 %) in the solid state, which is further used as the coatings of a blue LED bulb to achieve white-light emission. The study not only provides a general method to the preparation of TPE-based metallacages but also explores their applications as solid-state fluorescent materials, which will promote the future design and applications of metallacages as useful emissive devices.

To overcome the limited brightness of existing fluorogenic molecular probes for biomolecular targets, we introduce a concept of fluorogenic dendrimer probe, which undergoes polarity-dependent switching due to intramolecular aggregation-caused quenching of its fluorophores. Based on a rational design of dendrimers with four and eight squaraine dyes, we found that octamer bearing dyes through a sufficiently long PEG(8) linker displays >400-fold fluorescence enhancement from water to non-polar dioxane. High extinction coefficient (~2,300,000 M -1 cm -1 ) resulted from eight squaraine dyes and quantum yield (~25%) make this octamer the brightest environment-sensitive fluorogenic molecule reported to date. Its conjugate with cyclic RGD used at low concentration (3 nM) enables integrin-specific fluorescence imaging of cancer cells with high signal-to-background ratio. The developed dendrimer probe is a "golden middle" between molecular probes and nanoparticles, combining small size, turn-on response and high brightness, important for bioimaging.

A series of highly emissive inert and chiral CrIII complexes displaying dual circularly polarized luminescence (CPL) within the NIR region have been prepared and characterized. The helical [Cr(dqpR)2 ]3+ (dqp=2,6-di(quinolin-8-yl)pyridine; R=OCH3 , Br or C≡CH) complexes were synthesized as racemic mixtures and resolved into their respective PP and MM enantiomers by chiral stationary phase HPLC. The corresponding enantiomers show large glum ≈0.2 and high quantum yield of up to 17 %, which afford important CPL brightness of up to 170 m-1 cm-1 , a key point for applications as chiral luminescent probes. Moreover, the long-lived CP-NIR emission provided by these chromophores (ms range) in aqueous solution opens the way toward the quantification of chiral targets in biological systems with time-gated detection. Thus, such chiral chromophores based on earth abundant and inert 3d metals open new perspectives in the field of CPL and represent an alternative to precious 4d, 5d and to labile 4f metal-based complexes.

Ultra-bright fluorescent nanoparticles (NPs) hold great promise for demanding bioimaging applications. Recently, extremely bright molecular crystals of cationic fluorophores were obtained by hierarchical co-assembly with cyanostar anion-receptor complexes of associated counterions. These small-molecule ionic isolation lattices (SMILES) ensure spatial and electronic isolation to prohibit dye aggregation quenching. We report a simple, one-step supramolecular approach to formulate SMILES materials into NPs. Rhodamine-based SMILES NPs stabilized by glycol amphiphiles show high fluorescence quantum yield (30%) and brightness per volume (5000 M -1 cm -1 / nm 3 ) with 400 dyes packed into 16-nm particles, corresponding to a particle absorption coefficient of 4 × 10 7 M -1 cm -1 . UV excitation of the cyanostar component leads to highest brightness (>6000 M -1 cm -1 / nm 3 ) by energy transfer to rhodamine emitters. Coated NPs stain cells and are thus promising for bioimaging.

Herein, we report the design of novel ultraviolet luminescent CsPbCl3 nanocrystals (NCs) with the emission peak at 381 nm through doping of cadmium ions. Subsequently, a surface passivation strategy with CdCl2 is adopted to improve their photoluminescence quantum yield (PLQY) with the maximum value of 60.5 %, which is 67 times higher than that of the pristine counterparts. The PLQY of the surface passivated NCs remains over 50 % after one week while the pristine NCs show negligible emission. By virtue of density functional theory calculations, we reveal that the higher PLQY and better stability after surface passivation may result from the significant elimination of surface chloride vacancy (VCl ) defects. These findings provide fundamental insights into the optical manipulation of metal ion-doped CsPbCl3 NCs.

A luminescent bimetallic AuI complex comprised of N-heterocyclic carbene (NHC) and carbazole (Cz) ligands, that is, (NHC')Au(NHC)AuCz has been synthesized and studied. Both carbene ligands in the bimetallic complex act as electron acceptors in tandem to increase the energy separation between the ground and excited state, which is higher than those found in either monometallic analogue, (NHC)AuCz and (NHC')AuCz. A coplanar geometry designed into the tandem complex ensures sufficient electronic coupling between the π-orbitals of the ligands to impart a strong oscillator strength to the singlet intra-ligand charge-transfer (1 ICT) transition. Theoretical modelling indicates that the emissive ICT excited state involves both NHC ligands. The tandem complex gives blue luminescence (λmax =480 nm) with a high photoluminescent quantum yield (ΦPL =0.80) with a short decay lifetime (τ=0.52 μs). Temperature-dependent photophysical studies indicate that emission is via thermally assisted delayed fluorescence (TADF) and give a small singlet-triplet energy difference (ΔEST =50 meV, 400 cm-1 ) consistent with the short TADF lifetime.

Near-IR organic light-emitting diodes (NIR-OLEDs) are potential light-sources for various sensing applications as OLEDs have unique features such as ultra-flexibility and low-cost fabrication. However, the low external electroluminescence (EL) quantum efficiency (EQE) of NIR-OLEDs is a critical obstacle for potential applications. Here, we demonstrate a highly efficient NIR emitter with thermally activated delayed fluorescence (TADF) and its application to NIR-OLEDs. The NIR-TADF emitter, TPA-PZTCN, has a high photoluminescence quantum yield of over 40 % with a peak wavelength at 729 nm even in a highly doped co-deposited film. The EL peak wavelength of the NIR-OLED is 734 nm with an EQE of 13.4 %, unprecedented among rare-metal-free NIR-OLEDs in this spectral range. TPA-PZTCN can sensitize a deeper NIR fluorophore to achieve a peak wavelength of approximately 900 nm, resulting in an EQE of over 1 % in a TADF-sensitized NIR-OLED with high operational device durability (LT95 >600 h.).

We demonstrate that multi-fluorinated boron-fused azobenzene (BAz) complexes can work as a strong electron acceptor in electron donor-acceptor (D-A) type π-conjugated polymers. Position-dependent substitution effects were revealed, and the energy level of the lowest unoccupied molecular orbital (LUMO) was critically decreased by fluorination. As a result, the obtained polymers showed near-infrared (NIR) emission (λPL =758-847 nm) with high absolute photoluminescence quantum yield (ΦPL =7-23%) originating from low-lying LUMO energy levels of the BAz moieties (-3.94 to -4.25 eV). Owing to inherent solid-state emissive properties of the BAz units, deeper NIR emission (λPL =852980 nm) was detected in film state. Clear solvent effects prove that the NIR emission is from a charge transfer state originating from a strong D-A interaction. The effects of fluorination on the frontier orbitals are well understandable and predictable by theoretical calculation with density functional theory. This study demonstrates the effectiveness of fluorination to the BAz units for producing a strong electron-accepting unit through fine-tuning of energy gaps, which can be the promising strategy for designing NIR absorptive and emissive materials.

Dimeric cycloparaphenylene (CPP) architectures with well-defined flipping motion are constructed taking advantage of an efficient cyclocondensation reaction. Variable-temperature nuclear magnetic resonance (VT-NMR) analyses and theoretical calculations indicate rapid interconversion of cis and trans conformers at room temperature, while energetically favorable trans conformer exists at low temperature with the metastable cis conformer hidden. The trihexylsilylethynyl-substituted dimer exhibits bright emission in solution at 616 nm with quantum yield up to 80 %, representing the brightest CPP-based emitter beyond 600 nm. A 1:2 host-guest complex of the dimer and C60 is established with negative cooperativity, demonstrating the first example of 1:2 complex from CPP derivatives.

Well defined detection and analysis of nanoparticle-sized samples such as extracellular vesicles or viruses may be important for potential disease diagnostics. However, using conventional flow-cytometry optical methods to evaluate such small particles is quite challenging. The reason is that the particle is smaller than the diffraction limit, making detection difficult. An alternative approach is fluorescence detection via conjugated fluorochromes attached to the nanoparticles; the challenge in this case is the limitation imposed upon detection of a very small number of emitted photons buried in high background photon counts. Emitted fluorescence is described by the well-known equation kf = σa I Q, which describes the emitted fluorescence rate (kf) (photons/s) as the multiplication of molecular absorption cross section(σa), excitation intensity (I), and quantum yield (Q). In addition, the excitation rate is equal to 1/t, which is the inverse of the lifetime of several ns representing the most typical conjugated fluorescent molecules used in flow cytometry. We recently developed a sub-ns photon sensor that is faster than most fluorescence lifetimes, since sub-ns speed is a critically important parameter for the separation of individual emitted photons. Based on our observation of fluorescence and background levels on typical commercial flow cytometers it is evident that a significant component of the background is induced by water-molecular vibrations. Therefore, understanding what constitutes all the components that contribute to the signals we measure in flow cytometry would help in defining what we currently call "background signals." We attempted to define a theoretical model to try to unravel these issues. This model was based on use of a reflective dry surface in the absence of water molecules. Our objective was to determine if it is possible to minimize background and enhance signal, and to provide valuable information on the contributing components of the signals collected. In order to test this model, we tested a single dried particle 50 nm in diameter on a reflective surface with minimum background. While this is clearly not a standard biological system, our results suggest that this quantum approach closely follows established photon base theory. Our goal was to define the parameters for practical nanoparticle-fluorescence analysis while enhancing our knowledge of the contribution of background properties.

Although the production of near-infrared (NIR)-absorbing organic polymers with an excellent nonlinear optical (NLO) response is vital for various optoelectronic devices and photodynamic therapy, the molecular design and relevant photophysical investigation still remain challenging. In this work, large NLO activity is observed for an NIR-absorbing bithiophene-based polymer with a unique head-to-head linkage in the NIR region. The saturable absorption coefficient and modulation depth of the polymer are determined as ∼-3.5×105 cm GW-1 and ∼32.43%, respectively. Notably, the polymer exhibits an intrinsic nonlinear refraction index up to ∼-9.36 cm2 GW-1 , which is six orders of magnitude larger than that of CS2 . The maximum molar-mass normalized two-photon absorption cross-section (σ2 /M) of this polymer can be up to ∼14 GM at 1200 nm. Femtosecond transient absorption measurements reveal significant spectral overlap between the 2PA and excited state absorption in the 1000-1400 nm wavelength range and an efficient triplet quantum yield of ∼36.7%. The results of this study imply that this NIR-absorbing polymer is promising for relevant applications.

There has been controversy surrounding the roles of the metal core (metal-metal interaction) and the shell (metal-ligand interaction) in photoluminescence of ligand-protected metal nanoclusters. We have discovered aggregation-induced room-temperature phosphorescence of a platinum-thiolate complex and its silver ion inclusion complex (a silver-doped platinum sub-nanocluster). The inclusion of silver ion boosted the photoluminescent quantum yield by 18 times. Photophysical measurements indicate that the rate of nonradiative decay was slower for the silver-doped platinum sub-nanocluster. DFT calculations showed that the LUMO, which had the main contribution from Ag s-orbital and Pt d-orbitals, played a critical role in suppressing the structural distortion at the excited state. This work will hopefully stimulate more research on designing strategies based on molecular orbitals of atomicity-precise luminescent multimetallic nanoclusters.

Molecules showing mechanochromic luminescence (MCL) are promising for use in the in the fields of sensing and probes. We report the design and synthesis of new naphthalimide-based hydrazone derivatives, NI-TPE and NI-3BA. Both the luminogens are weakly emissive with s Φf =0.3 % and 0.5 % respectively when aggregated in amorphous states as strong π-π stacking and intermolecular interaction prevent luminescence. On the contrary, in the crystalline state, single crystal analysis of two derivatives shows that nonradiative decay is reduced or inhibited by molecular stacking modes and intermolecular interactions. Increases of fluorescence emission intensity to s Φf =5.5 % and 6.0 % upon solvent evaporation are attributed to weak π-π overlapping and hydrogen bonding (N-H ⋅⋅⋅ O, distance 2.99 A), which are beneficial to the formation of molecules with a loose packing. At the same time, the packing modes that the two derivatives adopt in the crystal lattice are destroyed to result in a low solid-state fluorescence quantum yield and a bathochromic shift of 23-25 nm upon grinding. All these factors cause the two derivatives show an unusual "turn off" MCL phenomenon. The fluorescence emission, its pH reversibility, and selective response to fluoride and acetate ions of up to 91-93 % in dilute solutions were also demonstrated.