Absolute Quantum Research Articles

(Invited) Calibration of Upconverting Materials and Nanoprobes

Upconversion has attracted much attention for the potential applications of nanomaterials and bulk materials. Upconversion nanoprobes and sensors rely on the non-linear emission of the reporters, which present a low efficiency due to their anti-Stokes nature. For these two reasons, the materials require accurate and contrastable efficiency measurements, typically by measuring the absolute upconversion quantum yield (UCQY). The methodology for such measurements will vary from traditional photoluminescence quantum yield techniques that have been applied for downshifting materials [1]. Effects like the scattering, broadband absorption and reemission, inner-filter effects, thickness, self-absorption, and temperature, have to be considered [2].This presentation will focus on some of these effects. The scattering has usually been neglected, however systems with scattering can increase the power density and subsequently the UCQY, as demonstrated both experimentally and via simulations [3]. Furthermore, this energy concentration also provides a new method for identifying the refractive index of phosphors, which is useful since some phosphors cannot be produced in macroscopic sizes. Broadband characterisation enables a route for characterisation exploiting the wide energy levels at the near-infrared. However, it introduces new challenges such as reemission [4]. In the case of applications that use a thick upconverted, the thickness is also a key parameter that can be responsible up to 50% of the emission [5].Finally, one of the applications that is been intensively researched is the use of upconverting and downshifting nanoparticles as temperature reporters. Absolute upconversion photoluminescence quantum yield characterisation for different probes will be presented with a modified integrating sphere that allows in-situ absorption and emission measurements.

Evaluation of radiative and non-radiative recombination lifetimes in InGaN quantum wells with different ion-implantation damage

In this study, we have separately evaluated the radiative and non-radiative recombination lifetimes for InGaN quantum well (QW) samples with different amounts of ion-implantation damage, and have investigated their temperature dependence. The radiative and non-radiative recombination lifetimes were calculated from photoluminescence (PL) decay time measured by time-resolved PL measurements, combined with the absolute internal quantum efficiency values estimated by the simultaneous photoacoustic and PL measurements. As a result, the experimentally observed radiative recombination lifetimes are almost the same for all samples, while the non-radiative recombination lifetimes are shorter for samples with larger ion-implantation damage. These findings will lead to a comprehensive understanding of carrier dynamics in InGaN-QW optical devices.

Synthesis of High-Fluorescent Diphenyl-anthracene Derivatives and Application in Detection of Nitroaromatic Explosives and Fingerprint Identification.

The development of high-intensity fluorescent materials is always the focuses and forefront projects because of their important applications in displays, sensing and detection fields. In recent years, the detection of explosives has attracted increasing attention due to security and counterterrorism issues. Herein, two diphenyl-anthracene (DPA) derivatives were designed and synthesized by introducing strong electron withdrawing fluorine atoms and cyano-groups to DPA, which exhibited strong fluorescence both in the solution and solid phase with the absolute quantum yields up to 70.4 % and 45.9 % respectively. The detection behavior of nitroaromatic explosives such as picric acid (PA), 2,4,6-trinitrotoluene (TNT) and 3-Nitropropionic acid (3-NP) also shows good sensitivity with the quenching constant as high as 6.3×104 L mol-1 . Theoretical calculation demonstrates that the fluorescence quenching behavior of the two DPA derivatives is caused by the behavior of photoinduced electron transfer (PET) and the resonance energy transfer (RET) studies explained the higher sensitivity and selectivity of both compounds towards PA than other nitro-containing explosives. Furthermore, the strong solid-state fluorescence of the DPA derivatives also shows excellent advantages in enhancing latent fingerprint recognition.

Creation of an oxygen-enriched environment during synthesis as an effective way to improve luminescent properties of Y2O3:Eu3+

The growing demand for luminescent nanomaterials intended for various applications increases the necessity to develop and improve approaches to the creation of highly efficient nanosized phosphors. In current study, an approach to enhancing the efficiency of red luminescence of monoclinic Y2O3:Eu3+ with the particle size of ∼20 nm by creating the oxygen-enriched environment during the gas-phase synthesis was developed. To investigate the effect of oxygen amount during the synthesis on characteristics of the phosphor, a series of nanostructured Y2O3:Eu3+ with the addition of 0–40 vol% O2 to the main buffer gas Ar was synthesized by laser vaporization. It is shown that the amount of added O2 exerts virtually no effect on the phase composition and particle size, but significantly improves the luminescent characteristics of Y2O3:Eu3+. Thus, the addition of 30 vol% O2 leads to virtually a 20-fold growth in the photoluminescence (PL) intensity caused by 5D0→7F0–4 transitions in Eu3+ and an increase in the absolute PL quantum yield from 3% to 53% (λex = 395 nm) compared to the sample synthesized without O2. The addition of oxygen also improves the emission color coordinates from (0.571, 0.320) to (0.630, 0.322) due to the removal of a considerable fraction of oxygen vacancies. The synthesized nanopowders are shown to be highly stable: upon storage under ambient conditions for two years. Quantum yield (QY) of the samples decreases by less than 2%. It is expected that the key features underlying the proposed approach will be useful for various methods used to synthesize oxide nanophosphors.

Quantification strategy of absolute chemiluminescence efficiency for systems of luminol with hydrogen peroxide

An important feature to be determined in mechanistic studies on chemiluminescence (CL) is its quantum efficiency, which can give significant chemical reaction information on the influence of the reactant structures and reaction conditions. However, most of the previous quantitative measurements of luminescence and quantum efficiencies are complex and incomplete. To overcome the inconvenience and underestimated quantum efficiency in each measurement, we report a simple and highly effective strategy to determine the absolute CL quantum efficiencies for three systems of luminol with hydrogen peroxide by means of a spectrometer along with an integrating sphere. The integrating sphere facilitated collection of all the emitted light and then transferred it to the spectrometer via an optical fiber proportionally. The CL quantum efficiency was determined by taking the ratio of total photons generated in the reaction system to the number of the limiting reactant molecules consumed. Absolute CL efficiencies of three luminol-H2O2 reaction systems with varied reactant concentrations or coreactants were found to be 37 %, 7.0 % and 6.6 % in a time course, which are much higher than those previously reported values of 1.0–1.3 %. Due to our complete photon collection design, a higher absolute CL efficiency can be realized. Furthermore, spooling CL spectra also provided a powerful visualization tool to observe the real-time CL evolution and devolution, allowing the study on kinetics of CL reaction systems. The above investigations are anticipated to promote further development of CL methodologies and their applications.

Insights on salting-out triggering aggregation-induced emission in nitrogen-doped graphene quantum dots

A straightforward methodology for obtaining Nitrogen-doped Graphene Quantum Dots (N-GQDs) with aggregation-induced emission (AIE) using salting-out purification processes is presented in this work. Various salts, including NaCl at concentrations of 50 mM, were found to be effective for stratification of graphene-based materials (GBMs) by salting-out treatments. These salts were shown to be safer, more cost-effective, and environmentally sustainable alternatives to (NH4)2SO4 reported in previous works. Remarkably, this method demonstrated the ability to promote the self-assembly of N-GQDs into stable J-aggregates-like arrays with an average fluorescence decay time of ca. 4 ns and absolute quantum yield with values of 3.5 % and 6.9 % for 100 mM and 2 M, respectively. In contrast to a typical quenching effect caused by π-stacking, these arrays exhibited aggregation-induced emissions, as evidenced by the presence of new excitation and emission bands at 532 and 600 nm, respectively. The scalability of the process, along with the absence of additional purification steps, renders these results of great scientific and technological interest. Furthermore, the modulable fluorescence, size, and stability of these GBMs suggest their potential application in energy cells, sensors, and biomedical imaging.

Solid superacid catalysts promote high-performance carbon dots with narrow-band fluorescence emission for luminescence solar concentrators

Facile and efficient method for constructing carbon dots (CDs) with narrow full width at half maximum (FWHM) is a major challenge in the field, and researches on regulating the FWHM of CDs are also rare and scarce. In this work, we delved into the synthesis of CDs with narrow fluorescence emission FWHM (NFEF-CDs) in the m-phenylenediamine (m-PD)/ethanol system, utilizing solid superacid resin as catalyst with solvothermal method. The resulting NFEF-CDs exhibit a photoluminescent (PL) emission peak at 521 nm with a narrow FWHM of 41 nm, an absolute PL quantum yield (QY) of 80%, and display excitation-independent PL behavior. Through comprehensive characterization, we identified the protonation of edge amino on NFEF-CDs as the key factor in achieving the narrow FWHM. Subsequently, we validated the broad applicability of solid superacid resins as catalysts for synthesizing CDs with narrow FWHM in the m-PD/ethanol system. Finally, we utilized a self-leveling method to prepare NFEF-CDs film on the surface of poly(methyl methacrylate) (PMMA) substrate and investigated the solid-state fluorescence properties of NFEF-CDs as well as their performance as luminescence solar concentrator (LSC) for photovoltaic conversion. The results revealed that the as-prepared LSC exhibit an internal quantum efficiency (ηint) of 42.39% and an optical efficiency (ηopt) of 0.68%. These findings demonstrate the promising prospects of NFEF-CDs in the field of LSCs and provide a theoretical basis for their application in photovoltaic conversion.

Dipolar 1,3,6,8-tetrasubstituted pyrene-based emitters containing hole- and electron-transporting moieties: Syntheses, structures, optical properties, electrochemistry and electroluminescence

A series of dipolar 1,3,6,8-tetrasubstituted pyrene-based compounds (PyTPA, PyCaZ and Py3CaZ) with a D-π-A configuration were designed and synthesized. The characteristic of these report compounds is that the pyrene core possesses two electron-transporting benzimidazole moieties at 1,8-positions and two hole-transporting arylamine segments at 3,6-sites. These compounds were structurally characterized and their photoelectric properties were investigated by spectroscopy, electrochemical and theoretical studies. The intermolecular π-π interactions successfully suppressed in these polysubstituted pyrenes, which leads to relatively high absolute fluorescence quantum efficiencies in film state (73.89–85.74 %). These three compounds exhibit high thermal stability with their decomposition temperature up to 520 °C. Two types of solution-processing devices were fabricated using compounds PyTPA and Py3CaZ as representatives to investigate their electron-transporting, hole-transporting and light-emitting properties. The single layer device based on PyTPA exhibits a current efficiency of 8.02 cd/A and a maximum brightness of 24439 cd/m2 at 7.8 V.

Multi‐Color Pure Organic Room Temperature Phosphorescent Materials with Long Lifetime and High Efficiency

AbstractOrganic room temperature phosphorescent (ORTP) materials have garnered significant interest in the fields of anti‐counterfeiting, optical display, and bio‐imaging owing to their distinctive optical properties. However, a major drawback of most existing ORTP materials is their short phosphorescence lifetime and low quantum yields (QYs), which greatly limit their applicability across multiple fields. In this paper, a covalently assisted host‐guest doping strategy that involves embedding three aminobenzoic acids with different carboxylate substitution positions into a cyanuric acid (CA) matrix through covalent bonding using microwave heating is proposed. All three prepared ORTP materials exhibit long phosphorescence lifetime exceeding 600 ms and high phosphorescence quantum yields (PhQYs) surpassing 20%. Among them, the composite of 2‐aminoterephthalic acid (2‐A) anuric acid stands out with its unique blue phosphorescence, boasting an exceptional absolute photoluminescence quantum yield (PLQY) of 98.95% and remarkable phosphorescence quantum yield (PhQY) of 76.42%, along with a long lifetime of 800 ms. Importantly, these high‐performance ORTP materials have been successfully utilized in anti‐counterfeiting and display applications.

Enhancing Circularly Polarized Luminescence in Quantum Dots through Chiral Coordination-Mediated Growth at the Liquid/Liquid Interface.

Here, we develop a novel methodology for synthesizing chiral CdSe@ZnS quantum dots (QDs) with enhanced circularly polarized luminescence (CPL) by incorporating l-/d-histidine (l-/d-His) ligands during ZnS shell growth at the water/oil interface. The resulting chiral QDs exhibit exceptional absolute photoluminescence quantum yield of up to 67.2%, surpassing the reported limits of 40.0% for chiral inorganic QDs, along with absorption dissymmetry factor (|gabs|) and luminescence dissymmetry factor (|glum|) values of 10-2, exceeding the range of 10-5-10-3 and 10-4-10-2, respectively. Detailed investigations of the synthetic pathway reveal that the interface, as a binary synthetic environment, facilitates the coordinated ligand exchange and shell growth mediated by chiral His-Zn2+ coordination complexes, leading to a maximum fluorescent brightness and chiroptical activities. The growth process, regulated by the His-Zn2+ coordination complex, not only reduces trap states on the CdSe surface, thereby enhancing the fluorescence intensity, but also significantly promotes the orbital hybridization between QDs and chiral ligands, effectively overcoming the shielding effect of the wide bandgap shell and imparting pronounced chirality. The proposed growth pathway elucidates the origin of chirality and provides insights into the regulation of the CPL intensity in chiral QDs. Furthermore, the application of CPL QDs in multilevel anticounterfeiting systems overcomes the limitations of replication in achiral fluorescence materials and enhances the system's resistance to counterfeiting, thus opening new opportunities for chiral QDs in optical anticounterfeiting and intelligent information encryption.

Electron‐Withdrawing Substituents Allow Boosted NIR‐II Fluorescence in J‐Type Aggregates for Bioimaging and Information Encryption

AbstractDeveloping molecular fluorophores with enhanced fluorescence in aggregate state for the second near‐infrared (NIR‐II) imaging is highly desirable but remains a tremendous challenge due to the lack of reliable design guidelines. Herein, we report an aromatic substituent strategy to construct highly bright NIR‐II J‐aggregates. Introduction of electron‐withdrawing substituents at 3,5‐aryl and meso positions of classic boron dipyrromethene (BODIPY) skeleton can promote slip‐stacked J‐type arrangement and further boost NIR‐II fluorescence of J‐aggregates via increased electrostatic repulsion and intermolecular hydrogen bond interaction. Notably, NOBDP‐NO2 with three nitro groups (−NO2) shows intense NIR‐II fluorescence at 1065 nm and high absolute quantum yield of 3.21 % in solid state, which can be successfully applied in bioimaging, high‐level encoding encryption, and information storage. Moreover, guided by this electron‐withdrawing substituent strategy, other skeletons (thieno‐fused BODIPY, aza‐BODIPY, and heptamethine cyanine) modified with −NO2 are converted into J‐type aggregates with enhanced NIR‐II fluorescence, showing great potential to convert aggregation caused emission quenching (ACQ) dyes into brilliant J‐aggregates. This study provides a universal method for construction of strong NIR‐II emissive J‐aggregates by rationally manipulating molecular packing and establishing relationships among molecular structures, intermolecular interactions, and fluorescence properties.

Electron-Withdrawing Substituents Allow Boosted NIR-II Fluorescence in J-Type Aggregates for Bioimaging and Information Encryption.

Developing molecular fluorophores with enhanced fluorescence in aggregate state for the second near-infrared (NIR-II) imaging is highly desirable but remains a tremendous challenge due to the lack of reliable design guidelines. Herein, we report an aromatic substituent strategy to construct highly bright NIR-II J-aggregates. Introduction of electron-withdrawing substituents at 3,5-aryl and meso positions of classic boron dipyrromethene (BODIPY) skeleton can promote slip-stacked J-type arrangement and further boost NIR-II fluorescence of J-aggregates via increased electrostatic repulsion and intermolecular hydrogen bond interaction. Notably, NOBDP-NO2 with three nitro groups (-NO2 ) shows intense NIR-II fluorescence at 1065 nm and high absolute quantum yield of 3.21 % in solid state, which can be successfully applied in bioimaging, high-level encoding encryption, and information storage. Moreover, guided by this electron-withdrawing substituent strategy, other skeletons (thieno-fused BODIPY, aza-BODIPY, and heptamethine cyanine) modified with -NO2 are converted into J-type aggregates with enhanced NIR-II fluorescence, showing great potential to convert aggregation caused emission quenching (ACQ) dyes into brilliant J-aggregates. This study provides a universal method for construction of strong NIR-II emissive J-aggregates by rationally manipulating molecular packing and establishing relationships among molecular structures, intermolecular interactions, and fluorescence properties.

Sulfone/Carbonyl-Based Donor-Acceptor Fluorescent Dyes: Synthesis, Structures, Photophysical Properties and Cell Imaging.

Electron-accepting units play vital roles in constructing donor-acceptor (D-A) conjugated organic optoelectronic materials; the electronic structures and functions of the acceptors need to be carefully unveiled to controllably tailor the optoelectronic properties. We have synthesized two D-A conjugated organic fluorophores, TPA-SO and TPA-CO, with similar molecular skeletons based on sulfone- or carbonyl-containing polycyclic aromatic acceptors. Both TPA-SO and TPA-CO display obvious solvent polarity-dependent photophysical properties and large Stokes shift of over 100 nm for strong intramolecular charge transfer processes. Experimental evidence indicates that the sulfone group in TPA-SO merely serves as a strong electron-withdrawing unit. TPA-SO shows yellowish-green emission with a peak at 542 nm and an absolute photoluminescence quantum yield (PLQY) of 98 % in solution, whereas the carbonyl group in TPA-CO can act as both an electron-withdrawing unit and spin transition convertor, so TPA-CO displays red emission with a low absolute PLQY of 0.32 % in solution. Impressively, upon going from solution to aggregate state, TPA-SO nanoparticles keep a high PLQY of 9.5 % and moderate biocompatibility, thus they are good nano-agents for cellular fluorescence imaging. The results reveal that the inherent acceptor characteristic acts as a crucial effect in the photophysical properties and applications of the organic fluorophores.

Enhancing blue phosphorescence in matrix-free carbon dots through covalent crosslinking

Room temperature phosphorescence (RTP) of carbon dots (CDs) has received extensive attention due to its excellent performance and promising application. Here, a novel kind of matrix-free CDs with blue phosphorescence emission was synthesized by a simple one-step hydrothermal method of heating (3-Aminopropyl) trimethoxysilane (APTMS) and phosphoric acid in aqueous solution. The obtained CDs show a phosphorescence lifetime of 315.73 ms, and the absolute photoluminescence quantum yield (PLQY) and the phosphorescence quantum yield (PQY) can reach up to 37.8 % and 12.4 %, respectively. From the experimental results, we speculate that the generation of RTP is attributed to the restriction effect of the covalent crosslinking structure of SiOSi, SiOC, or SiC bonds formed on the CDs surface. In addition, phosphoric acid as a crosslinking agent and heteroatom dopant can promote the formation of cross-linked structures and facilitate the intersystem crossing (ISC) process, thus enhancing room temperature phosphorescence. Finally, the CDs were successfully used in information encryption and anti-counterfeiting.

Particle size effect on the structure, morphology and optical properties of europium doped ZrO2 nanoparticles

In the recent decade, various potential applications of the luminescence of nanosized ZrO2:Eu3+ have been demonstrated. However, the particle size effect on the luminescence properties of ZrO2:Eu3+ still requires intensive investigation. To this end, a series of tetragonal ZrO2:Eu3+ nanopowders with the europium concentration of 4 wt% and particle size of 3.0 ± 0.7 to 12.0 ± 4.8 nm was synthesized by laser vaporization. It was shown that the dominant role in the optical properties of ZrO2:Eu3+ nanoparticles belongs to OH groups, oxygen vacancies, and Eu3+ ions. It was found that a decrease in the particle size is accompanied by a significant increase in the emission intensity in the region of ∼440 nm. Based on the results of thermal analysis, IR and UV–vis DR spectroscopies, it was concluded that this luminescence is due to the emission of adsorbed OH groups. At the same time, a decrease in the number of vacancies with a decrease in the particle size leads to a change in the absolute quantum yield QY from ∼7 to 3.5%. In addition, despite the overall decrease in the intensity of the red luminescence of Eu3+, a decrease in the particle size leads to the appearance and increase in the emission intensity of the surface Eu3+. Thus, changing the particle size from 12.0 to 3.0 nm leads to a twofold decrease in the luminescence efficiency of ZrO2:Eu3+ and a shift in the color of its emission from pink-red (0.36, 0.26) to blue (0.19, 0.10). The results obtained are expected to be useful for further optimization of the luminescence properties of nanosized ZrO2:Eu3+ in numerous applications.

Crystal structures and solid-state luminescent properties of Eu(III), Gd(III) and Tb(III) complexes with hexafluoroacetylacetone and 4′-substituted terpyridine ligands

Six mononuclear lanthanide complexes [Ln(hfac)3(ptpy)] (Ln(III) = Eu (1), Gd (2), Tb (3)) and [Ln(hfac)3(ftpy)] (Ln(III) = Eu (4), Gd (5), Tb (6)), synthesized with 1,1,1,5,5,5-hexafluoroacetylacetone (hfac) as a first ligand and 4′-phenyl-2,2′:6′,2″-terpyridine (ptpy) or 4′-furan-2,2′:6′,2″-terpyridine (ftpy) as a second ligand, were characterized by elemental analyses, infrared spectroscopy, single-crystal X-ray diffraction, and powder X-ray diffraction. Thermogravimetric analyses indicate that these ternary lanthanide complexes possess very good thermal stability. Solid-state samples of 1-Eu and 4-Eu exhibit characteristic red luminescence at CIE: 0.6721, 0.3276 and CIE: 0.6859, 0.3139, with absolute quantum yields of 59.95% and 83.14% and luminescence lifetimes of 0.819 and 0.727 ms, respectively. Solid-state samples of 3-Tb and 6-Tb display characteristic green luminescence at CIE: 0.2736, 0.7167 and CIE: 0.2674, 0.7219, with absolute quantum yields of 2.58% and 0.52% and luminescence lifetimes of 0.040 and 0.033 ms, respectively. The results suggest that terpyridine is a good sensitizer for Eu(III), while hfac is a good sensitizer for Tb(III). In solid-state, the synergistic sensitization effect of hfac and terpyridine is significant for Eu(III), but less for Tb(III). And the electron-donating substituent at the 4′-position make terpyridine more suitable for the sensitization of Eu(III), but unfavorable for Tb(III).

A red-emitting ultrasensitive fluorescent probe for specific detection and biological visualization of cysteine in vitro and in vivo

Developing efficient strategies for specific detection of cysteine (Cys) is of great importance for identifying complicated biological roles in physiological and pathological processes. Herein, an ultrasensitive red-emission fluorescent probe (termed 1) is constructed for specific detection and biological visualization of Cys. The linked-anthocyanin fluorophore modified with a twisted N, N-diethylamino moiety shows improved red-shifted emission (642 nm) and absolute quantum yield (0.224 in dimethyl sulfoxide), as well as minimal fluorescence background signal and good water solubility. Meanwhile, utilizing acryloyl chloride as recognition group endows the probe 1 with excellent sensitivity and selectivity towards Cys (limit of detection: 2.93 nM). More importantly, the in vitro and in vivo results confirm that the probe 1 has the capacity of fluorescence imaging of Cys and good biological safety, which holds great promise for bioanalysis and biosensing of Cys.

Fluorophenyl-modified AIPE-active cationic Pt(II) complexes for detecting picric acid in aqueous media

Two new fluorophenyl-modified cationic cyclometalated Pt(II) complexes have been synthesized. The effects of the fluorophenyl substituents on the properties of the Pt(II) complexes were investigated systematically in comparison with a phenyl-modified complex. The absolute quantum yields of the complexes are significantly increased due to the presence of fluorophenyl groups. All complexes exhibit evident aggregation-induced phosphorescent emission activities in a CH3CN/H2O system. Furthermore, they can effectively detect picric acid (PA) in CH3CN/H2O. Among them, the complex with a 2,4-difluorophenyl group exhibits the lowest limit of detection at 0.09 μM. These complexes exhibit excellent selectivity for detecting PA in complicated environments and work well in real water samples. The luminescence quenching of the complexes is caused by photo-induced electron transfer.

Single Molecular Persistent Room-Temperature Phosphorescence and Circularly Polarized Luminescence from Binaphthol-Decorated Optically Innocent Cyclotriphosphazenes.

Circularly polarized luminescence (CPL) features of BINOL-decorated cyclotriphosphazenes (CPs) are reported for the first time. The luminescence dissymmetry factor (glum ) of these compounds in chloroform solutions and polymethyl methacrylate (PMMA) thin films with wt 1 % doping concentrations are found to be 1.0×10-3 , and 2.9×10-3 , respectively. However, no CPL signal is observed for the pristine solids. The enantiomers (CP-(R)/CP-(S)) show ultraviolet photoluminescence (~350-360 nm) in solution and the solid state. These compounds show ~10 times larger absolute photoluminescence quantum yield (PLQY) than the simple BINOLs in the solutions state. In the solid state, CP-(R) shows larger PLQY than binaphthol-(R); in contrast, the S enantiomer shows lower PLQY than binaphthol-(S); this indicates that the isomer-dependent solid-state packing of these compounds plays a crucial role in controlling the PL. Thin films with more than 1 % doping concentration and pristine solids of these compounds do not show persistent room-temperature phosphorescence (pRTP) due to concentration-caused quenching. However, thin films with wt 1 % of these chiral emitters exhibit pRTP characteristics with a ~159-343 ms lifetime under vacuum. Theoretical calculations reveal that the cyclophosphazene acts as an optically innocent dendritic core, and the optical features of these compounds are dictated by the pendent BINOL chromophore.

Photochemically and Thermally Generated BN-Doped Borafluorenate Heterocycles via Intramolecular Staudinger-Type Reactions.

A series of BN-incorporated borafluorenate heterocycles, bis(borafluorene-phosphinimine)s (11-15), have been formed via intramolecular Staudinger-type reactions. The reactions were promoted by light or heat using monodentate phosphine-stabilized 9-azido-9-borafluorenes (R3P-BF-N3; 6-10) and involve the release of dinitrogen (N2), migration of phosphine from boron to nitrogen, and oxidation of the phosphorus center (PIII to PV). Density functional theory (DFT) calculations provide mechanistic insight into the formation of these compounds. Compounds 11-15 are blue emissive in the solution and solid states with absolute quantum yields (ΦF) ranging from 12 to 68%.