Finely regulated luminescent Ag-In-Ga-S quantum dots with green-red dual emission toward white light-emitting diodes

Ag-In-Ga-S(AIGS)quantum dots(QDs)have recently attracted great interests due to the outstanding optical properties and eco-friendly components,which are considered as an alternative replacement for toxic Pb-and Cd-based QDs.However,enormous attention has been paid to how to narrow their broadband spectra,ignoring the application advantages of the broadband emission.In this work,the AIGS QDs with controllable broad green-red dual-emission are first reported,which is achieved through adjusting the size distribution of QDs by controlling the nucleation and growth of AIGS crystals.Resultantly,the AIGS QDs exhibit broad dual-emission at green-and red-band evidenced by photoluminescence(PL)spectra,and the PL relative intensity and peak position can be finely adjusted.Furthermore,the dual-emission is the intrinsic characteristics from the difference in confinement effect of large particles and tiny particles confirmed by temperature-dependent PL spectra.Accordingly,the AIGS QDs(the size consists of 17 nm and 3.7 nm)with 530 nm and 630 nm emission could successfully be synthesized at 220°C.By combining the blue light-emitting diode(LED)chips and dual-emission AIGS QDs,the constructed white light-emitting devices(WLEDs)exhibit a continuous and broad spectrum like natural sunlight with the Commission Internationale de l’Eclairage(CIE)chromaticity coordinates of(0.33,0.31),a correlated color temperature(CCT)of 5425 K,color rendering index(CRI)of 90,and luminous efficacy of radiation(LER)of 129 lm/W,which indicates that the AIGS QDs have huge potential for lighting applications.

Pressure Distinguishes the Dual Emissions in Pseudohalide 2D Ruddlesden-Popper Perovskite Cs_(2)Pb(SCN)_(2)Br_(2)

Two-dimensional(2D)Ruddlesden-Popper(RP)halide perovskites with diverse structures and properties have drawn increasing attention due to their promising optoelectronic applications.Recently,a new all-inorganic Cs_(2)Pb(SCN)_(2)Br_(2) has been reported that opens up new potential for the development of 2D RP perovskites.However,recent reports of unusual dual emissions and two-edge absorption in Cs_(2)Pb(SCN)_(2)Br_(2) have generated intense debate about its origin and remains controversial.Here,by combining continuous pressure tuning with in situ diagnostics,we have unambiguously revealed the underlying mechanisms that the 2D Cs_(2)Pb(SCN)_(2)Br_(2) exhibits an intrinsic blue emission at 2.66 eV and an absorption edge close to the emission peak.While the gradually formed CsPbBr_(3) is responsible for the green emission at 2.33 eV with the absorption shoulder at 2.41 eV.Furthermore,by fitting the temperature-dependent intensity of the intrinsic blue emission,we have determined the corrected value of exciton binding energy for 2D Cs_(2)Pb(SCN)_(2)Br_(2) to be 90 meV.Intriguingly,an emission enhancement of 2.5 times is achieved in Cs_(2)Pb(SCN)_(2)Br_(2) under a mild pressure within 0.8 GPa,caused by the pressuresuppressed exciton-phonon interaction.This work not only elucidates the origin of the dual emissions and two-edge absorption in Cs_(2)Pb(SCN)_(2)Br_(2),but it also provides a potential means to regulate and optimize the optoelectronic properties of 2D perovskites.

A gelable pure organic luminogen with fluorescence-phosphorescence dual emission

Pure organic luminogens with room temperature phosphorescence(RTP) have drawn much attention due to their fundamental importance and promising applications in optoelectronic devices, bioimaging, sensing, etc. Fluorescence-phosphorescence dual emission at room temperature, however, is rarely observed in pure organic materials. Herein, we reported a metal-and heavy-atom free pure organic luminogen with tert-butyl groups, DtBuCZBP, which is ready to form organogels in dimethylsulfoxide(DMSO).It emits prompt and delayed fluorescence, as well as RTP, namely dual emission in as-prepared solid, gels and polymeric films.To the best of our knowledge, it is the first example of metal-and heavy-atom free pure organic gelator with RTP emission. Such unique RTP and moreover dual emission properties in different states make DtBuCZBP a potential material for diverse applications.

Self-twisting for macrochirality from an achiral asterisk molecule with fluorescence-phosphorescence dual emission

Understanding of the role of supramolecular chirality for tuning material optoelectronic properties has been restricted by the limited number of cases. A particular challenge is to impose supramolecular chirality onto multicolor luminescent systems that can emit in aggregation state. Here we present a self- assembly strategy from a well-selected asterisk molecule for generating supramolecular chirality with fluorescence-phosphorescence dual emission. The work takes advantages of （1） achiral chemical structure dependent peculiar self-assembly that can spontaneously undergo symmetry breaking to produce macrochirality, and （2） the assembly process can be monitored by time which due to the crystallization-driven self-assembly by self-twisting, allowing a self-progressing chiral amplification. A multicolor luminescence induced by the fluorescence-phosphorescence dual emission along with such a self-assembly behavior was also observed at a single solution system versus the time. The self-twisting chiral self-assembly fashion provides new prospects for understanding the establishment of nanochirality from achiral molecular building blocks.

Dual emission of singlet and triplet states boost the sensitivity of pressure-sensing

Pressure-related sensing materials in mechanochromic luminescent materials have received wide attention.However,at present,most piezochromic luminescence(PCL)materials have problems such as aggregation-caused quenching(ACQ)effect due to the presence of powder form,complicated preparation methods and fluorescence quenching effect under high pressure.To solve these problems,we employ three components containing carbon dots(CDs),layered double hydroxides(LDHs)and polyvinyl alcohol(PVA)to construct the CDs-LDHs/PVA film.The LDHs can provide a rigid environment for CDs and improve the luminescent efficiency of CDs.The film shows high sensitivity,stability and reversibility.Moreover,the compressed film can recover to its original state by heating.Therefore,the PCL film with dual emission(fluorescence and phosphorescence)characteristic is constructed,which boosts the sensitivity of pressure-sensing.

AIEgen configuration transition and aggregation enable dual prompt emission for single-component nondoped white OLEDs

The dual emission(DE)feature in materials holds great potential to revolutionize the development of one-component system white organic lightemitting diodes(WOLEDs).However,the reported DE materials remain scarce owing to the formidable challenge of breaking Kasha’s rule and managing the intricate energy/charge transfer processes.Herein,we have introduced a groundbreaking DE AIEgen,2CzAn-TPE,which possesses a simple structure and undergoes Z-to-E isomerization and exhibits yellow and red fluorescence powders for pre-and post-sublimation,respectively.With relatively lower potential energy,Z-conformation((Z)-1,2-diphenyl-1,2-bis(4-(10-(9-phenyl-9H-carbazol-3-yl)anthracen-9-yl)phenyl)ethene)of 2CzAn-TPE can be readily transformed into E-conformation((E)-1,2-diphenyl-1,2-bis(4-(10-(9-phenyl-9Hcarbazol-3-yl)anthracen-9-yl)phenyl)ethene)via vacuum sublimation.The utilization of X-ray diffraction and grazing-incidence-wide-angle X-ray scattering techniques confirms the structural transformation,while the crystallographic analysis reveals the establishment of numerous intermolecular CH⋅⋅⋅πinteractions between the tetraphenylethene(TPE)moiety and both the anthracene and carbazole units.This allows a densely packed molecular arrangement,thereby offering propitious conditions for excimer generation in the E-conformation aggregated state.By utilizing the sublimated 2CzAn-TPE as an emitter,a nondoped one-component WOLED was prepared,exhibiting an exceptionally high external quantum efficiency(EQE)of 5.0%,which represents one of the highest performances among all one-componentWOLEDs.This research introduces a novel,simple,and efficient approach to realize highly efficient one-molecule WOLEDs.

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.

Efficient photo-induced RTP materials based on phenothiazine and polycyclic aromatic hydrocarbons:Tunable emission color and thermal stimulus response

The development of photo-responsive room temperature phosphorescence(RTP)materials has attracted more and more attention for their broad application pro-spects.Until now,it is still difficult to obtain the related ma-terials with both high efficiency and long lifetime.And the lacking of emission in blue and red regions also largely re-stricts their further applications.In this work,we reported a new strategy to maintain both high efficiency and long lifetime in RTP luminogens through the integration of phenothiazine to facilitate n-π*transition and polycyclic aromatic hydro-carbons(PAHs)dominated byπ-π*transition.When they were doped into polymer matrix,full color photo-induced RTP materials were obtained for the changedπ-conjugation of PAHs.Among them,PTri@PVP showed the best RTP per-formance with phosphorescence efficiency of 20.73%and lifetime up to 819 ms.Specifically,after turning off the ul-traviolet-visible(UV)irradiation upon this system,time-de-pendent phosphorescence afterglow from green to blue was exhibited,which was found to originate from two distinct molecular conformations and could be further regulated by thermal stimulus.Accordingly,multiple anti-counterfeiting applications,including screen printing,multi-color patterns and multi-dimensional information encryption,were suc-cessfully demonstrated.

How ligand coordination and superatomic-states accommodate the structure and property of a metal cluster:Cu_(4)(dppy)_(4)Cl_(2)vs.Cu_(21)(dppy)_(10)with altered photoluminescence

We have synthesized two copper nanoclusters(NCs)with a protection of the same ligand diphenylphosphino-2-pyridine(C_(17)H_(14)NP,dppy for short),formulated as Cu_(4)(dppy)_(4)Cl_(2)and Cu21(dppy)10,respectively.The former one bears a distorted tetrahedron Cu4 core with its six edges fully protected by chlorine and dppy ligands,while the latter presents a symmetric Cu_(21)core on which ten dppy molecules function as monolayer protection via well-organized monodentate or bidentate coordination.Interestingly,the Cu_(4)(dppy)_(4)Cl_(2)cluster exhibits a strong yellow emission at∼577 nm,while Cu_(21)(dppy)_(10)displays dual emissions in purple(∼368 nm)and green(∼516 nm)regions respectively.In combination with TD-DFT calculations,we demonstrate the origin of altered emissions and unique stability of the two copper nanoclusters pertaining to the ligand coordination and metallic superatomic states.

Development of Dual Phosphorescent Materials Based on Multiple Stimuli-Responsive Ir(Ⅲ)Acyclic Carbene Complexes

A new series of Ir(Ⅲ)carbene complexes with luminescent mechanochromism derived from trans-cis isomerization has been developed.Through the introduction of π-conjugating groups into the acyclic carbene ligand,the mechanochromic trans-and cisconfigurations can be readily interconverted,leading to dual emissive properties in the solid state.Moreover,the solid-or film-forming solvent system can control the dual emission and mechanoresponsive properties in the solid state.The potential uses of a single emissive complex to develop multicolor emissive and multiple stimuli-responsive films have been studied.

Transfer of an Aluminum Atom:An Avenue to Aluminum Heterocycles

Synthetic chemistry enables constructing molecular complexity using simple substrates through simple processes.We disclose an unprecedented Al-atom transfer strategy for the synthesis of aluminum heterocycles with high atom economy.This strategy involves an effective cycloaddition of a free carbazolyl-aluminylene with unsaturated hydrocarbons,followed by facile cleavage of the N-Al bond.The aluminylene formally behaves as a tetra-active ambiphilic[Al+]cation transfer reagent in a two-step manner,and the only byproduct is a carbazolide salt that can be utilized to regenerate the aluminylene.The carbazolyl Al-heterocycles show unique luminescent properties,in which one exhibits dual emission.Our approach not only has a significant impact on the future design of single-atom addition reactions but also paves the way for emissive materials based on Al-heterocycles.