Chiral thermally activated delayed fluorescence materials for circularly polarized organic light-emitting diodes

Chirality is an important natural characteristic of organic molecules,and chiral organic molecules have shown extensive application in areas such as pharmaceutical development and material science.Benefiting from the ability to achieve circularly polarized luminescence(CPL),chiral luminescent materials have shown potential applications in anti-glare display,optical communication and,3D display,etc.Due to the ability to harvest both singlet and triplet excitons by a fast reverse intersystem crossing process without involving noble metals,chiral thermally activated delayed fluorescence(TADF)materials with point chirality,axial chirality,planar chirality and helical chirality are regarded as the state-of-the-art materials for circularly polarized organic light-emitting diodes(CP-OLEDs).In recent years,the chiral TADF materials and CP-OLEDs have rapidly developed,but unfortunately,the dissymmetry factors(g)are far from the requirement of practical applications.The ideal emitters and devices should have both high efficiency and a g factor,or at least a balance between these two elements.This review gives an overview of recent progress in chiral TADF materials,with a particular focus on the chiral skeleton,CPL property and device performance.Furthermore,the molecular design concept,device structure and methods to improve the g factors of chiral materials and CP-OLEDs are also discussed.

Ultrastable and ultrasensitive pH-switchable carbon dots with high quantum yield for water quality identification,glucose detection,and two starch-based solid-state fluorescence materials

It is attractive and encouraging to develop new fluorescent carbon dots(CDs)with excellent optical properties and promising applications prospects.Herein,highly-efficient green emissive CDs(m-CDs)with a high quantum yield(QY)of 71.7%in water are prepared through a facile solvothermal method.Interestingly,the m-CDs exhibit excellent fluorescence stability in the pH range of 1–9.However,the fluorescence intensity of the m-CDs is almost completely quenched as the pH is increased from 9 to 10.The mechanism of the unique pH-responsive behavior is discussed in detail and a plausible mechanism is proposed.Owing to the unique pH-responsive behavior,the m-CDs are used as a on-off fluorescent probe for water quality identification.By combining the reversible pH-ultrasensitive optical properties of the m-CDs in the pH range of 9–10 with the glucose oxidase-mimicking(GOx-mimicking)ability of Au nanoparticles(AuNPs),glucose can be quantitatively detected.Finally,two environment-friendly starch-based solid-state fluorescence materials(powder and film)are developed through green preparation routes.

Thermally activated delayed fluorescence carbazole-triazine dendrimer with bulky substituents

Carbazole-triazine dendrimers with a bulky terminal substituent were synthesized,and the thermally activated delayed fluorescence(TADF)property was investigated.Compared to unsubstituted carbazole dendrimers,dendrimers with bulky terminal substituents showed comparable to better photoluminescence quantum yields(PLQY)in neat films.Phenylfluorene(PF)-substituted dendrimers showed the highest PLQY of 81%,a smallΔEst of 0.06 eV,and the fastest reverse intersystem crossing(RISC)rate of∼1×10^(5 )s^(−1) compared to other dendrimers.Phosphorescence measurements of dendrimers and dendrons(fragments)indicate that the close proximity of the triplet energy of phenylfluorene-substituted carbazole dendrons(^(3)LE)to that of phenylfluorene-substituted dendrimers(^(1)CT,^(3)CT)contributes to RISC promotion and improves TADF efficiency.Terminal modification fine-tunes the energy level and suppresses intermolecular interactions,and this study provides a guideline for designing efficient solution-processable and non-doped TADF materials.

Fluorescent Silk Obtained by Feeding Silkworms with Fluorescent Materials

Comprehensive Summary Fluorescent silk has potential application in many fields such as bioimaging,tissue engineering scaffolds,luminescent marks,and dazzling fabrics.Among the methods to endow natural silk with fluorescent properties,feeding silkworms with fluorescent additives is facile,low-cost and environment friendly,which has the prospect of large-scale production.In this paper,we reviewed the research progress for this aim in the past ten years,and summarized the unified characteristics for the substances that can enter the silk gland by digestive tract of silkworms.The advantages and disadvantages of various fluorescent materials for this application are compared in detail.And the future research directions are suggested to overcome the shortcomings of the present research.

Structure,Calculation,Optical Properties and Bioimaging of an Organic Fluorescence Compound

A π-conjugated optical functional organic compound comprising an electron donor(D) and acceptor(A) was synthesized. The crystal structure was determined through single-crystal X-ray diffraction analysis. It crystallizes in monoclinic, space group P2_(1) with a = 9.6610(5), b = 8.9093(4), c = 26.303(1)Å, β = 96.262(4)°, V = 2250.5(2)Å^(3), Z = 4, D_(c)= 1.220 Mg/m^(3), F(000) = 872, Μr = 413.50, μ = 0.072 mm^(-1), the final R = 0.0569 and wR = 0.1700 for 8976 observed reflections with I > 2σ(I). Optical properties were studied in detail through theoretical calculation and experimental study. The result reveals that the compound exhibits excellent fluorescence performance and it can be compatible in the cytoplasm of NIH/3T3 cells, showing potential in fluorescence microscopy bioimaging.

A Novel 3D Zn-based Luminescence Metal-organic Framework: Synthesis, Structure and Fluorescence Enhanced Sensing of Ammonia Vapor in Air

A three-dimensional(3D)zinc metal-organic framework(MOF),Zn4(μ4-O)(bcd)3(complex 1)has been synthesized by using 1-[bis(4-carboxylphenyl)methyl]-1,3-diazole(H2 bcd)and Zn(NO3)2·6 H2O under hydrothermal conditions.The structure has been determined by single-crystal X-ray diffraction analyses and further characterized by elemental analyses,IR spectra,powder X-ray diffraction(PXRD)and thermogravimetric analyses(TGA).Single-crystal X-ray diffraction analyses reveal that complex 1 crystallizes in trigonal system,space group R3 with a=23.0521(6),b=23.0521(6),c=15.3326(6)A,γ=120°,V=7056.2(4)A^3,Z=6,C54H36N6O13Zn4,Mr=1242.37,Dc=1.754 g/cm^3,F(000)=3756,the final R=0.0411 and wR=0.1007 for 2743 observed reflections(I>2σ(I)).Complex 1 consists of a 3D network constructed by four nuclear clusters Zn4(μ4-O)(COO)6 N3 and the bcd2-ligand.Interestingly,1 exhibits strong luminescent emission in solid state at room temperature and could be used as a qualitative fluorescence enhancing sensor for ammonia vapor in air.

Fluorescence-resonance energy transfer(FRET)within the fluorescent metallacycles

During past few years,the construction of fluorescent metallacycles featuring the fluorescenceresonance energy transfer behavior has attracted extensive attention due to their diverse applications such as real-time monitoring the dynamics of coordination-driven self-assembly,photoswitching fluorescence-resonance energy transfer,and light-controlled generation of singlet oxygen for cancer therapy.This review focuses on the recent advances on the design principles,preparation methods,optical properties,and the wide applications of fluorescent metallacycles with the FRET property.

Pure-Blue Fluorescence Molecule for Nondoped Electroluminescence with External Quantum Efficiency Approaching 13%

A pure-blue light-emitting material is one of the key components in the preparation of organic lightemitting diode(OLED)displays.Although highefficiency blue OLEDs have been realized in thermally activated delayed fluorescence(TADF)materials,they need to be dispersed into suitable hostmaterials.Hence,exploring efficient nondoped,pure-blue luminous molecules is important.

Highly emissive perylene diimide-based bowtie-shaped metallacycles

Metallacycles hold great promise for fluorescence-based sensing due to their synthetic advantages and unique physicochemical properties. However, it remains highly challenging to develop a versatile methodology for constructing highly emissive metallacycles with targeted functionalities and therefore soughtafter properties. Herein, we report a general strategy to construct a series of highly emissive perylene diimide-based metallacycles via the self-assembly of perylene diimide-based tetrapyridyl ligand with different dicarboxylic ligands featuring fixed angles and cis-Pt(PEt_(3))_(2)(OTf)_(2). Single crystal X-ray diffraction analyses verify the formation of bowtie-like metallacycles with two triangular cavities. Notably, the fluorescence quantum yields of most assemblies exceed 98%, amongst the highest values for metallacycles.Additionally, such metallacycles exhibit sensitive fluorescence responses toward picric acid with a detection limit of 2.8 × 10^(-6)mol/L. This study not only provides a rational strategy for preparing highly emissive bowtie-shaped metallacycles, but also sheds light on their usage in the detection of picric acid and associated compounds.

Preparation and characterization of NaYF_4:Er^(3+),Tm^(3+)@NaYF_4:Ce^(3+),Tb^(3+) microcrystals with dual-mode emissions at the single-particle level

Under hydrothermal environment,we synthesized lanthanide ions doped sodium yttrium fluoride(NaYF4:Er,Tm@NaYF4:Ce,Tb) luminescent microcrystals via an epitaxial growth technique.The structure and morphology of these microcrystals were examined by SEM,TEM,EDS and XRD measurements.These particles show dual-mode emissions with red upconversion(UC) and green down conversion(DC) as single particles level.The mean length and diameter of these microparticles increase from 0.43 to2.26 μm and from 1.33 to 1.86 μm,respectively.Most interestingly,the photoluminescence properties of NaYF4:Er,Tm@NaYF4:Ce,Tb phosphor crystals are highly dependent on the crystallite size.The microcrystals fluoresce emit dual-mode emissions when they are solid or dispersed in solvents.Benefiting its intensive fluorescence and uniform morphology,these materials hold great potential for security and anti-counterfeiting applications.

Metal-Organic Frameworks-Based Fluorescent Nanocomposites for Bioimaging in Living Cells and in vivo

Metal-organic frameworks(MOFs)as a class of porous functional materials have attracted more and more attention for biomedical applications.To date,MOFs have been developed for bioimaging based on a series of advantages such as the large surface areas,high porosity,fluorescence functionalities and good biocompatibility.It is worth noting that organic or inorganic fluorescent materials such as fluorescent dyes,quantum dots,metal nanoclusters and nanosheets can combine MOFs or be encapsulated in MOFs to form fluorescent nanocomposites for excellent imaging function.Importantly,excellent imaging capabilities are of great significance in living cells and in vivo for detection,diagnosis and cancer therapy.In this review,we focus on the recent research of the bioimaging in living cells and in vivo based on various MOF-based nanocomposites and their potential biological clinical applications.

Preparation of a fixed-tetraphenylethylene motif bridged ditopic benzo-21-crown-7 and its application for constructing AIE supramolecular polymers

Benzo-21-crown-7(B21 C7)is one of the most important crown ethers,which not only shows excellent physicochemical properties but also exhibits promising binding capability with dialkylammonium salts.In this paper,we designed and synthesized a fixed-tetraphenylethylene(FTPE)motif bridged ditopic benzo-21-crown-7 molecule(H).The fixed tetraphenylethylene motif endows H with aggregation induced emission(AIE)prope rty.In the presence of a ditopic dialkylammonium salt guest molecule(G),a fluorescent supramolecular polymer with golden luminescent property could be fabricated.This B21 C7-based host-guest supramolecular polymer with golden fluorescence may have potential application in dynamic luminescent materials.

Catalytic chemodivergent annulations betweenα-diketones and alkynylα-diketones

Four types of unprecedented and chemodivergent reactions betweenα-diketones and alkynylα-diketones have been achieved under the catalysis of phosphine and Br?nsted base,respectively,leading to the rapid construction of four different classes of biologically important but synthetically challenging molecular scaffolds including 2-hydroxyfuran-3(2H)-ones,4-hydroxy-2-oxabicyclo[2.2.1]heptan-3-ones,1,3-diaryl cyclobutanes,and 4-(furan-2(3H)-ylidene)cyclopent-2-enones.The formation of the products includes two novel rearrangement processes,and further transformations on the products can be easily achieved to deliver value-added substances such as highly functionalized cyclopentanes.Moreover,the 2-hydroxyfuran-3(2H)-one products display promising photophysical properties such as green luminescence under UV light and aggregation-induced emission effect,showing the practical application value of this work.The great potential ofα-diketones in both synthetic chemistry and material science has been unambiguously demonstrated.

Versatile core-shell magnetic fluorescent mesoporous microspheres for multilevel latent fingerprints magneto-optic information recognition

Latent fingerprints are extremely vital for personal identification and criminalinvestigation,and potential information recognition techniques have been widelyused in the fields of information and communication electronics.Although physicalpowder dusting methods have been frequently employed to develop latent fingerprintsand most of them are carried out by using single component powders ofmicron-sized fluorescent particles,magnetic powders,or metal particles,there isstill an enormous challenge in producing high-resolution image of latent fingerprintsat different backgrounds or substrates.Herein,a novel and effectivenanoimpregnation method is developed to synthesize bifunctional magnetic fluorescentmesoporous microspheres for latent fingerprints visualization by growthof mesoporous silica(mesoSiO_(2))on magical Fe_(3)O_(4) core and then deposition offluorescent YVO4:Eu^(3+)nanoparticles in the mesopores.The obtainedFe_(3)O_(4)@mesoSiO_(2)@YVO4:Eu^(3+)microspheres possess spatially isolated magneticcore and fluorescent shell which were insulated by mesoporous silica layer.Dueto their small particle size of submicrometer scale,high magnetization and lowmagnetic remanence as well as the combined magnetic and fluorescent properties,the microspheres show superior performance in visual latent fingerprint recognitionwith high contrast,high anti-interference,and sensitivity as well as goodretention on multifarious substrates regardless of surface permeability,roughness,refraction,colorfulness,and background fluorescence interference,and it makesthem ideal candidates for practical application in fingerprint visualization andeven magneto-optic information storage.