X-ray-activated Bi^(3+)/Pr^(3+)co-doped LiYGeO_4 phosphor with UV and NIR dual-emissive persistent luminescence

X-ray-activated luminescence materials have broad application prospects in photodynamic therapy of deep tissue.Among them,X-ray-activated persistent luminescence materials(PLMs)exhibiting multiple emission peaks have drawn extensive attention for the ir capacity to achieve a combination of bioimaging and therapeutic functions.Here,we developed a novel PLM,LiYGeO_4:Bi^(3+),Pr^(3+),that simultaneously exhibits UV and NIR dual persistent luminescence(PersL)emissions after irradiation by X-ray.The material can be re peatedly excited by X-ray and emits similar lumine scence intensity every time,which shows good PersL stability.In addition,LiYGeO_4:Bi^(3+),Pr^(3+)exhibits photostimulated PersL properties by stimulation with a red light-emitting diode(LED)or NIR laser after long-term decay.This work provides a new choice of X-ray-excited PLMs with UV and NIR dual emission and the novel phosphor shows promise as a potential candidate for the integration of treatment and diagnosis of deep tumors.

Green up-conversion Luminescence in Nd^(3+)-Ho^(3+) Co-doped Oxyfluorotellurite Glasses

Blue, green and red up-conversion luminescence at around 490, 545 and 650 nm, which result from the Ho^3＋5F3→5I8, （5F4,5S2）→3. 5I8 and 5F5→ 5I8 transitions, respectively, were observed in Nd3＋-Ho3. co-doped oxyfiuorotellurite glasses under 800 nm excitation. Among these up-conversion luminescence, the green emission was extremely strong and the blue and red emission intensities were very weak. Selectively strong green up-conversion luminescence of these glasses indicate a high possibility for realizing a green upconversion laser. Up-conversion processes for the blue, green and red emissions are two-photon processes assisted by Nd3^＋→Ho^3＋ energy transfer. It is proposed that the up-conversion mechanism for the blue and green emissions is different from that for the red emission. The respective mechanisms are discussed.

Aggregation-induced emission polymer systems with circularly polarized luminescence

Functional materials with circularly polarized luminescence(CPL)have attracted tremendous attention due to their promising applications in three-dimensional dis-plays,chiral recognition and catalysis,photoelectronic devices,contrast imaging,information encryption,and otherfields.Among various CPL-active materials,poly-meric systems with aggregation-induced emission(AIE)have emerged as excellent candidates because of their efficient aggregate-statefluorescence,large solid-state dissymmetry factor,excellent processibility,diversified self-assembly behaviors,and readily switchable CPL properties.This review summarizes and discusses the recent progress as well as future perspective of diverse AIE polymer systems with CPL,including CPL-active covalent AIE polymers,CPL-active supramolecular AIE polymers,and AIEgen/polymer composites with CPL.According to the loca-tion or introduction method of AIEgen in polymer structures,this review further divides CPL-active covalent AIE polymers into three categories,including polymers with AIEgen in main chains,polymers with AIEgen in side chains,and CPL-active polymers with clusterization-triggered emission.CPL-active supramolecular AIE polymers are discussed based on the driving force for the formation of supramolecular polymers,including host–guest interactions,metal coordination,and other non-covalent interactions.Moreover,examples on the construction of CPL-active AIEgen/polymer composites by physically mixing AIEgens with chi-ral(supra)polymers are also presented.This review is anticipated to provide readers with an overall view on the design strategies of CPL-active AIE polymers,and facil-itate further research on the development of CPL materials and AIE polymers with advanced applications.

Nucleophilic Substitution Polymerization-Induced Emission of 1,3-Dicarbonyl Compounds as a Versatile Approach for Aggregation-Induced Emission Type Non-Traditional Intrinsic Luminescence

Nucleophilic substitution reaction and 1,3-dicarbonyl compounds play significant roles in organic chemistry, and non-traditional intrinsic luminescence (NTIL) has become an emerging research area. Here, we demonstrate the successful nucleophilic substitution polymerization of 1,3-dicarbonyl compounds, including acetylacetone, 3,5-heptanedione, methyl acetoacetate, cyclopentane-1,3-dione, 1,3-indandione, 1-phenyl-1,3-butanedione and dibenzoylmethane, where reactive hydrogens at α position of 1,3-dicarbonyl compounds are involved. Through this base catalyzed nucleophilic substitution polycondensation between 1,3-dicarbonyl compounds and α,α’-dibromo xylene, a series of nonconjugated poly(1,3-dicarbonyl)s have been successfully prepared with high yield (up to >99%) under mild conditions. Investigations reveal that this nucleophilic substitution polycondensation exhibits self-accelerating effect and flexible stoichiometry characteristics, which exhibits advantages over traditional polycondensation methods. This polymerization also exhibits intriguing polymerization-induced emission (PIE) characteristics, where nonconjugated poly(1,3-dicarbonyl)s exhibit intriguing chemical structure dependent aggregation-induced emission (AIE) type NTIL. This work therefore expands the monomer, method, chemical structure and property libraries of polymer chemistry, which may cause inspirations to polymerization methodology, PIE, AIE and NTIL.

Upconverting and downshifting circularly polarized luminescence in a superstructural helix

The modulation of circularly polarized luminescence(CPL) has become an increasingly prominent area of research. In this study,we propose a unique “one-excitation-to-three-emissions” CPL system through the co-assembly of an upconversion system,incorporating one sensitizer(Pt(II) mesotetraphenyl tetrabenzoporphyrine, Pt TPBP) and two annihilators(R/S-DPA and R/SBDP) within liquid crystals. The chiral nature of the annihilators induces a transformation of the nematic liquid crystal into chiral nematic liquid crystals(N*LC), establishing an excellent chiral matrix. Upon the incorporation of the sensitizer Pt TPBP and subsequent excitation at 635 nm, the system demonstrates two independent triplet–triplet annihilation photon upconversion(TTA-UC) with the emission in blue and yellow, aided by thermally activated triplet–triplet energy transfer(TTET). This is accompanied by the simultaneous generation of upconverting circularly polarized luminescence(UC-CPL) and downshifting near-infrared circularly polarized luminescence(DS-CPL) originating from the residual luminescence of Pt TPBP. Remarkably,fine-tuning the ratio between the two annihilators allows the TTA-UC system to exhibit multicolor CPL emission with an amplified luminescence dissymmetry factor(glum, reaching up to 0.6). Our study unveils a previously unreported “one-excitation-to-three-emissions” system and provides a versatile strategy for modulating CPL emissions, surpassing conventional methodologies.

Multicolor Circularly Polarized Luminescence of a Single-Component System Revealing Multiple Information Encryption

Metal-free materials with multicolor tunable circularly polarized luminescence(CPL)are attractive because of their potential applications in information storage and encryption.Here,we designed two enantiomers composed of chiral dialkyl glutamides and achiral vibration-induced emission(VIE)moiety,which can switch on CPL after a simple gelation process.It is noteworthy that the CPL colors vary in different solvents,and this is attributed to various self-assembly-induced microstructures,in which the VIE moiety is restrained to different degrees.Accordingly,a multidimensional code system composed of a quick response code,a ultraviolet(UV)light-activated color code,and a CPL information figure was constructed.To our satisfaction,the system possesses multiple information-storage functions.The orthogonal anticounterfeiting and CPLenhanced encryption functions also improve the system information encryption ability.In brief,this study provides a practical example of CPL applied to information security and an effective approach to obtain a single-component color-tunable CPL material with multiple information storage and encryption functions as well.

Synthesis,structure,and luminescence properties of melilite Dy^(3+):Lu_(x)CaLa_(0.98-x)Ga_(3)O_(7) phosphors for use in yellow light-emitting devices

Dy^(3+) and Lu^(3+) co-doped CaLaGa_(3)O_(7) phosphors were prepared via high-temperature solid-phase reaction.The electronic structures of LuxCaLa_(0.98-x)Ga_(3)O_(7) were investigated by the first-principles calculations.The influence of Lu^(3+) on yellow light emission was studied using X-ray diffraction(XRD)and photoluminescence(PL) measurements.The XRD results indicate that compared to Dy^(3+):CaLaGa_(3)O_(7),the cell parameters of Dy^(3+):LuCaLaGa_(3)O_(7) tend to decrease,which is due to the smaller radius of Lu^(3+).When pumped by blue GaN laser diode(LD),the emission peaks of phosphors with different Lu^(3+)doping concentrations in the visible region are similar,with the strongest peak at 574 nm in the yellow light region,which is sensitive to human eyes.The optimal doping concentration of Lu^(3+) is confirmed to be1 at%,when all emission spectra and measured fluorescence lifetimes are taken into account.Moreover,the optimal phosphor composition Dy^(3+):Lu_(x)CaLa_(0.98-x)Ga_(3)O_(7)(x=0.01) has an internal quantum efficiency(IQE) of 46.94% and an external quantum efficiency(EQE) of 15.19%.Most notably,the prepared phosphor demonstrates excellent thermal stability and a high activation energy(0.203 eV).In addition,the International Illumination Commission color coordinates of the Dy^(3+):LuxCaLa_(0.98-x)Ga_(3)O_(7) phosphors are in the yellow light area.The above analysis indicates that the Dy^(3+):LuxCaLa_(0.98-x)Ga_(3)O_(7)(x=0.001)phosphor has promising application prospects in yellow light-emitting devices.

Three-primary-color molecular cocrystals showing white-light luminescence,tunable optical waveguide and ultrahigh polarized emission

Three-primary-color luminescent materials are highly desirable to construct white-light emitting resource,multi-color optical displays,and tunable photonic applications.However,the efficient strategy to establish the three-primary-color systems with unique photofunctionalities is still rather limited,particularly for molecular materials.Herein,we developed a molecular cocrystal route to obtain three-primary-color emissive materials by tuning different donor-acceptor units based on the same chromophore(4,4′-bis(2,5-dimethylstyryl)biphenyl,Bdb).The warm and cold white-light together with multi-color emission in most of visible region can be highly adjusted by rationally tuning different mixture components of three-primary-color cocrystals through an energy transfer mechanism.Furthermore,the blue/green/red emitters endow Bdb molecular cocrystals novel colortunable photonic properties(such as one-dimensional(1D)/2D optical waveguide,polarized fluorescence,up-conversion luminescence,and amplified spontaneous emission),benefitting from their well-defined micro/nanostructures and high crystallinity.Particularly,the high luminescence quantum yield(82.49%)and polarized anisotropy(0.723)outperform most of state-ofthe-art molecular crystalline materials.Therefore,this work supplies an effective way to fabricate new types of three-primarycolor phosphors through luminescent cocrystals,which have promising applications in the fields of full-color displays,whitelight irradiation,low-dimensional optical polarization,and micro/nanophotonics.

A novel Li^(+)-doped MgLuGaO_(4)phosphor with stable white-light emission and long persistent luminescence

In recent years,white persistent luminescence materials have received extensive attention due to the potential application of white light in the field of plant growth lighting.The white persistent luminescence materials synthesized by traditional methods either have strict requirements on the concentration of doped ions or cannot produce white light continuously and stably due to different decay rates of various emission centers,which limits their further application.In our work,we successfully synthesized a novel Li^(+)-doped MgLuGaO_(4)phosphor with stable white-light emission and long persistent luminescence.The broadband emission of MgLuGaO_(4):Li^(+)is mainly located at 350-650 nm,which has no change at different decay time,showing stable white-light emission.The persistent luminescence intensity is increased by 3.8 times and the persistent luminescence time is extended from 24 h to more than 36 h by doping Li+ions.Stable white-light and long persistent luminescence emission make it promising to be used in plant growth lighting.

Intercluster aurophilicity-driven aggregation lighting circularly polarized luminescence of chiral gold clusters

Herein,we prepared two novel pairs of enantiomeric gold cluster complexes,AU4PL4/Au4PD4 and(Au4L4)n/(Au4D4)n with atomic precision.In Au4PL4/Au4PD4,the discrete chiral Au4-based aggregation-induced emission(AIE)luminogens are separated by bulky substitutes.The corresponding aggregates are cyan-emitting with a photoluminescence quantum yield(PLQY)of 14.4%.Upon decreasing the size of the substituents,these chiral Au4 clusters are strung together by inter-cluster Au-Au interactions,which cause a low-energy green emission from the aggregated(Au4L4)n/(Au4D4)n with a much higher PLQY of 41.4%and more intense circularly polarised photoluminescence(CPL)with a dissymmetry factor|gPL|of 7.0×10^−3.Using(Au4L4)n/(Au4D4)n,circularly polarised organic light-emitting diodes(CP-OLEDs)were for the first time fabricated with|gEL|=|gPL|.These findings signify that inter-cluster metallophilic interactions are a new and important type of driving force for AIE and crystallization-induced emission(CIE),suggesting great potential of CPL-active metal clusters in CP-OLEDs.

Frontiers in circularly polarized luminescence:molecular design,self-assembly,nanomaterials,and applications

The research in circularly polarized luminescence has attracted wide interest in recent years.Efforts on one side are directed toward the development of chiral materials with both high luminescence efficiency and dissymmetry factors,and on the other side,are focused on the exploitations of these materials in optoelectronic applications.This review summarizes the recent frontiers(mostly within five years)in the research in circularly polarized luminescence,including the development of chiral emissive materials based on organic small molecules,compounds with aggregation-induced emissions,supramolecular assemblies,liquid crystals and liquids,polymers,metal-ligand coordination complexes and assemblies,metal clusters,inorganic nanomaterials,and photon upconversion systems.In addition,recent applications of related materials in organic light-emitting devices,circularly polarized light detectors,and organic lasers and displays are also discussed.

A NIR to NIR rechargeable long persistent luminescence phosphor Ca_(2)Ga_(2)GeO_(7):Yb^(3+),Tb^(3+)

Near infrared to near infrared(NIR-NIR)photo-stimulated persistent luminescence(PSPL)has shown excellent potential in high-resolution bioimaging for deep tissues.However,the PSPL in NIR-Ⅱregion(900-1700 nm)is still lacking.In this work,Ca_(2)Ga_(2)GeO_(7):Yb^(3+),Tb^(3+)(CGGYT)phosphor with unique lowdimensional crystal structure was synthesized by high-temperature solid-state reaction.Thanks to the carriers transferring from deep traps to shallow ones induced by low energy light,the 978 nm PSPL originating from ^(2)F_(5/2) to ^(2)F_(7/2) transition of Yb^(3+)induced by multimode stimulating(980 nm or WLED)is successfully realized after pre-excited by UV lamp.The NIR PSPL of the specimen can be repeatedly stimulated after placed in dark for 12 h.Moreover,the results indicate that codoping with Tb^(3+)can significantly enhance the NIR-ⅡPSPL owing to the quantum cutting persistent energy transfer(QC PET)from Tb^(3+)to Yb^(3+).Our study points to a new direction for the future development of multimode PSPL materials for bioimaging or multimode optical storage applications.

Circularly polarized luminescence induced by excimer based on pyrene-modified binaphthol

A new chiral bromobinaphthol-pyrene compound was developed to achieve a green circularly polarized luminescence(CPL)from its excimer with a dissymmetry factor(|glum|)value of 4.3×10^-3 and a high quantum yieldΦF,solid up to 55.9%,while no CPL signals could be observed for the blue luminescence from unimolecule.Meanwhile,reversal CPL signals can be observed from both concentrated solution and solid.

Simple sulfone-bridged heterohelicene structure realizes ultraviolet narrowband thermally activated delayed fluorescence,circularly polarized luminescence,and room temperature phosphorescence

Due to narrowband emission and high quantum efficiencies,polycyclic aromatic heterocycles with multi-resonance thermally activated delayed fluorescence(MR-TADF)properties have recently gained considerable attention in the organic optoelectronic field.Albeit their great promise in the full visible region covering from blue to red,MR-TADF emitters with ultraviolet emission have been rarely reported.Through locking the two ortho-positions of a triphenylamine core by sulfone groups,a simple polycyclic aromatic heterocycle,BTPT,was facilely constructed,exhibiting 368 nm ultraviolet emission with a narrow full width at half maximum(FWHM)of 33 nm.Its neat film exhibited distinct TADF property with a main emission peak at 388 nm.Noteworthily,the enantiomeric crystals of BTPT not only demonstrated significant circularly polarized luminescence(CPL)with large luminescence dissymmetry factor in the 10^(-3) order but also displayed obvious room temperature phosphorescence(RTP).The relationship between this innovative helical unit and unique photophysical properties,including ultraviolet MR-TADF,CPL,and RTP,was reasonably revealed.

Host molecule enhanced aggregation induced emission of chiral silver nanoclusters for achieving highly efficient circularly polarized electroluminescence

Chiral metal nanoclusters(MNCs)are competitive candidates for fabricating circularly polarized light-emitting diodes(CPLEDs),but the device performance is greatly limited by the poor emission of MNCs in solid thin films.Herein,host molecule enhanced aggregation induced emission(AIE)of MNCs is demonstrated for fabricating highly efficient CPLEDs.Namely,on the basis of the AIE effect of atomically precise enantiomeric(R/S)-4-phenylthiazolidine-2-thione capped silver(R/S-Ag_(6)(PTLT)_(6))NCs in solid thin films,1,3-bis(carbazol-9-yl)benzene(mCP)is introduced as a host molecule to control the orientation and packing arrangements of R/S-Ag_(6)(PTLT)_(6) NCs throughπ–πinteractions with the R/S-Ag_(6)(PTLT)_(6) NCs and further enhance the AIE.The as-fabricated Ag_(6)(PTLT)_(6) NC/mCP hybrid solid thin film shows a high photoluminescence quantum yield of 71.0%close to that of Ag_(6)(PTLT)_(6) NC single crystal.As the hybrid films are employed as the active emission layers of CPLEDs,mCP also suppresses the triplettriplet annihilation and balances the charge transport.Thus,the CPLEDs exhibit a maximum brightness of 3,906 cd/m^(2),peak external quantum efficiency of 10.0%,electroluminescence dissymmetry factors of−5.3×10^(−3)and 4.7×10^(−3).

NHC-derived carbon-centered luminescent radicals with shortwavelength emission via suppression of Kasha's rule

Luminescent organic radicals have garnered increasing attention owing to their versatile applications in sensing, imaging, and organic light-emitting diodes(OLEDs), attributed to their unique emission properties originating from the doublet spin state.However, the natural narrow bandgap of organic free radicals typically limits their emission to the long-wavelength region.Designing luminescent organic radicals with short-wavelength emission remains a significant challenge. Herein, a series of carbon-centered radicals with short-wavelength emission(383–476 nm) by combining N-heterocyclic carbenes with various polycyclic aromatic hydrocarbons(PAHs)(2-naphthyl, 2a~Ⅰ and 2b~Ⅰ;2-phenanthryl, 2a~Ⅱand 2b~Ⅱ;2-anthryl, 2a~Ⅲand 2b~Ⅲ;3-phenanthryl, 2a~Ⅳand 2b~Ⅳ). Theoretical calculations reveal that the introduction of PAHs significantly increases the ΔE_(D2-D1) in 2a^(Ⅰ–Ⅲ)and 2b^(Ⅰ–Ⅲ)compared to that in phenyl-derived radical congeners. Consequently, the internal transition from D2 to D1 is impeded, leading to a high yield of D2 emission and a suppressed Kasha's rule, thereby overcoming the limitations imposed by their narrow bandgap. For 2a~Ⅳ and 2b~Ⅳ, despite a moderately large ΔED2-D1value, the ΔED3-D1value exceeds 1 e V, indicating that their emission likely originates from the D3 state. Furthermore, we utilized 2a~Ⅲand 2b~Ⅲ as emissive materials in OLEDs,resulting in blue emissions with external quantum efficiencies of 7.5% and 6.5%, respectively.

Near Infrared Photoluminescence from Yb,Al Co-implanted SiO2 Films on Silicon

Intense room-temperature near infrared （NIR） photoluminescence （980 nm and 1032 nm） is observed from Yb,Al co-implanted SiO2 films on silicon. The optical transitions occur between the ^2F5/2 and ^2F7/2 levels of Yb^3＋ in SiO2. The additional Al-implantation into SiO2 films can effectively improve the concentration quenching effect of Yb^3＋ in SiO2. Photoluminescence excitation spectroscopy shows that the NIR photoluminescence is due to the non-radiative energy transfer from Al-implantation-induced non-bridging oxygen hole defects in SiO2 to Yb^3＋ in the Yb-related luminescent complexes. It is believed that the defect-mediated luminescence of rare-earth ions in SiO2 is very effective.

Photodegradation-Induced Turn-On Luminescence of Tetraphenylethylene-Based Trithiocarbonate Polymers

Main observation and conclusion Fluorescent intelligent materials have attracted wide attention because of their great potential applications.One major hurdle for the development and application of fluorescent intelligent materials is the aggregation-caused quenching effect in the solid state.Herein,tetraphenylethylene-based trithiocarbonate polymers with satisfactory molecular weights(Mw up to 24900)were synthesized through a one-pot polymerization route under mild conditions.The polymers were non-emissive due to the quenching effect of the trithiocarbonate group.However,upon UV irradiation,the polymers degraded and strong emission from the tetraphenylethylene unit was observed.Such a unique property endows them with great potential applications,such as photopatterning,anti-counterfeit labels,and UV detection.

Aggregation-amplified circularly polarized luminescence from axial chiral boron difluoride complexes

The development of small organic molecules with intense and switchable circularly polarized luminescence(CPL) is currently attracting great interest due to their promising applications in chiroptical devices and sensors. In this paper, CPL-active BF2-bridged azaanthracene dimers(BA1 and BA2) were facilely synthesized by incorporating boron difluoride unit to the binaphthalene. BA1 and BA2 show moderate CPL in diluted solutions, however, BA2 exhibited aggregation-amplified red CPL with large dissymmetry factor up to 1.6×10^(-2). Moreover, acid-/base-triggered CPL switch off/on were also realized via disaggregation/aggregation of BA2 in tetrahydrofuran(THF)/water binary solvents.

Fluorescence Emission Centres and the Corresponding Infrared Fluorescence Saturation in a Bismuth-Doped Silica Fibre

We investigate the fluorescence characteristics of bismuth doped silica fibres with and without A1 co-dopant which are fabricated by means of modified chemical vapour deposition （MCVD） technique, and find that the fluorescences in the red region （centred around 750nm） and in the infrared region （centred around llOOnm） may originate from different emission sites in the fibre. Strong upconversion phenomena are observed in both Al-codoped and non A1 codoped bismuth fibres when the fibres are excited by an acoustic-optic Q-switched Nd：YVO4 laser. Both the aspects indicate that the upper energy level absorption reported in the work of the bismuth doped silica fibre lasers may result from the fluorescence emission sites that are not responsible for the infrared emission. It is thus expected that optimizing the compositions and the fabrication conditions of the fibre and then transferring more fluorescence emission centres are helpful for the infrared emission.