Solid-state room-temperature phosphorescence activated by the end-capping strategy of cyano groups

Avoiding the tedious process of crystal cultivation and directly obtaining organic crystals with desirable phosphorescent performance is of great significance for studying their structure and properties.Herein,a set of benzophenone-cored phos-phors with bright green afterglow are obtained on a large scale through in-situ generation via an end-capping strategy to suppress non-radiative triplet excitons and reinforce the intermolecular interactions.The ordered arrangement of phosphors with alkyl-cyano groups as regulators is crucial for the enhancement of room-temperature phosphorescence(RTP)emission,which has been further verified by the attenuated lifetimes in isolated states through the formation of inclusion complexes upon binding with pillar[5]arenes.Moreover,the hierarchical interactions of phos-phors,including hydrogen bonding,π-πstacking interactions,and van der Waals forces,are quantified by crystal structures and theoretical calculation to deeply inter-pret the origins of RTP emission.With this study,we provide a potential strategy for the direct acquisition of crystalline organic phosphors and modulation of RTP.

Recent Advances in Pure-Organic Host-Guest Room-Temperature Phosphorescence Systems Toward Bioimaging

Organic room-temperature phosphorescence(RTP)materials have garnered considerable attention in the fields of biosensing,optoelectronic devices,and anticounterfeiting because of their substantial Stokes shifts,tunable emission wavelengths,and prolonged lifetimes.These materials offer remarkable advantages for biological imaging applications by effectively reducing environmental autofluorescence and enhancing imaging resolution.Recently,host-guest systems have been employed as efficient approaches to fabricate pure-organic RTP materials for bioimaging,providing benefits such as controllable preparation and flexible modulation.Consequently,an increasing number of corresponding studies are being reported;however,a comprehensive systematic review is still lacking.Therefore,we summarize recent advances in the development of pureorganic RTP materials using host-guest systems with regard to bioimaging,including rigid matrices and sensitization.The challenge and potential of RTP for biological imaging are also proposed to promote the biomedical applications of organic RTP materials with excellent optical properties.

Room-Temperature Phosphorescence and Lifetime of Fossil Resins (Amber) from Dominican Republic, Mexico, Baltic Sea, Myanmar, and Fushun, China

Amber can emit room temperature phosphorescence(RTP)under the well-known 365 nm fluorescence ultraviolet light.This paper is devoted to the phosphorescence study of 20 pieces of amber materials from the Dominican Republic,Mexico,Baltic sea,Myanmar,and Fushun,China.The results show that amber from the same geographic origin has similar shape in phosphorescence spectra.However,the shape of the amber phosphorescence spectra varies depending on their different localities.Burmite(amber from Myanmar)and Fushun amber have a bright yellow phosphorescence with a long lifetime,while the Dominican and Mexican ones are weaker and last shorter.The irradiation of Baltic amber becomes faint or even inert.Phosphorescence spectral Gaussian fitting results suggest an emission maximum near 550 nm in most amber samples.Their phosphorescence lifetime,analyzed through the exponential function fitting,is up to 1 second in Burmite and Fushun samples,shorter in the Dominican and Mexican ones,about 0.230 s,and the shortest in Baltic amber,close to 0.151 s.These variations of phosphorescence lifetime and intensity are related to the relative geological ages of these amber.It indicated that the phosphorescence agent was probably formed during the long geological time.While the anomaly occurred in Baltic amber,the only one found in a sea secondary deposit form,it demonstrated that the terrestrial geological environment these amber preserved has prevented the phosphorescence agent to be deactivated.

Study on Room-Temperature Phosphorescence of 1-Bromonaphthalene in Media of Surfactant and β-Cyclodextrin

Sdrictants(S) induced room-ternperature phorphorescence(RTP) frorn l-bromonaplithalene(l-BrN) in aerated aqueous solutions of o-cyclodextha(β-CD) hasbeco mvestigated m detail. lt has been fotmd that the partial incIu5ion and coil ofhydIocarbon chain of edctans at the mouth of the 6-CD ca\4ty' is reSPoedle foTbright RTP

A new insight into aggregation structure of organic solids and its relationship to room-temperature phosphorescence effect

In order to improve the performance of organic luminescent materials,lots of studies have been carried out at the molecular level.However,these materials are mostly applied as solids or aggregates in practical applications,in which the relationship between aggregation structure and luminescent property should be paid more attention.Here,we obtained five phenothiazine 5,5-dioxide(O-PTZ)derivatives with distinct molecular conformations by rational design of chemical structures,and systematically studied their room-temperature phosphorescence(RTP)effect in solid state.It was found that O-PTZ dimers with quasi-equatorial(eq)conformation tended to show strongerπ-πinteraction than quasi-axial(ax)conformers in crystal state,which was more conducive to the generation of RTP.Based on this result,a multi-level structural model of organic solids was proposed to draw the relationship between aggregation structure and RTP effect,just like the research for the structureproperty relationship of proteins.Using this structural model as the guide,boosted RTP efficiency from 1%to 20%was successfully achieved in the corresponding host-guest doping system,showing its wide applicability.

Photoactivated Circularly Polarized Room-Temperature Phosphorescence from Phenoselenazine Derivative and Its Application in Information Security

Room-temperature phosphorescence(RTP)materials have experienced rapid development due to their potential in organic light-emitting diode,information security,bioimaging,etc.However,the design of chiral organic phosphors with circularly polarized RTP(CPP)property remains a formidable challenge.Here,we introduce a chiral perturbation approach using a combination of chiral binaphthol and phenoselenazine derivative to achieve CPP.The photoactivated CPP in polystyrene(PS)film demonstrates a luminescence dissymmetry factor(glum),emission efficiency,and RTP lifetime up to 9.32×10^(–3),27.0%,and 40.0 ms,respectively.The remarkable sensitivity of PS film to oxygen and temperature enables the adjustable emission colors,ranging from green to offwhite and blue under varying conditions.The doping systems,utilizing hosts of triphenylphosphine and 9-phenylcarbazole,demonstrate an extended CPP lifetime of 85.9 ms and exhibit a persistent mechanoluminescence property with low pressure response threshold as low as 0.15 N.The information security provided by this CPP material was attained via the using of diverse emission colors and afterglow generated by distinct UV irradiation times and host materials.Alternately,it can also be achieved by observing different emission patterns using R-and L-polarizer.The research has presented a reliable approach for producing CPP materials with high emission efficiency and glum.

Photoinduced Room-Temperature Phosphorescence of Triphenylamine-Phenothiazine Derivative-Doped Polymers

Photo-responsive room-temperature phosphorescent(RTP)materials have garnered significant interest due to the advantages of rapid response,spatiotemporal control,and contactless precision manipulation.However,the development of such materials remains in its infancy,underscoring the importance of exploiting novel and efficient light-responsive RTP molecules.In this work,three phenothiazine derivatives of TPA-PTZ,TPA-2PTZ,and TPA-3PTZ were successfully synthesized via the Buchwald-Hartwig C—N coupling reaction.By embedding these molecules as RTP guests into polymethyl methacrylate(PMMA)matrix,photo-induced RTP properties were realized.Upon sustained UV irradiation,there was an enhancement of 19 times in the quantum yield to reach a value of 5.68%.Remarkably,these materials exhibit superior alongside robust light and thermal stability,maintaining high phosphorescence intensity even after prolonged UV exposure(irradiation for>200 s by a 365 nm UV lamp with the power of 500μW·cm-2)or at higher temperature up to 75℃.The outstanding properties of these photo-induced RTP materials make them promising candidates for applications in information encryption,anti-counterfeiting,and advanced optical materials.

Detection of Oxygen Based on Host-Guest Doped Room-Temperature Phosphorescence Material

Quantitative oxygen detection,especially at low concentrations,holds significant importance in the realms of biology,complex environments,and chemical process engineering.Due to the high sensitivity and rapid response of the triplet excitons of phosphorescence to oxygen,pure organic room-temperature phosphorescence(RTP)materials have garnered widespread attention in recent years for oxygen detection.However,simultaneously achieving ultralong phosphorescence at room temperature and quantitative oxygen detection from pure organic host-guest doped materials poses challenges.The d ensely packed materials may decrease non-radiative decay to increase the phosphorescence,but are unsuitable for oxygen diffusion in oxygen detection.Herein,the oxygen sensitivity of host-guest doped RTP materials using 4-bromo-N,N-bis(4-(tertbutyl)phenyl)aniline(TPABuBr)as the host and 6-bromo-2-butyl-1H-benzo[de]isoquinoline-1,3(2H)-dione(NIBr)as the guest was developed.The doped material exhibits fluorescence-phosphorescence dual-emission behavior at room temperature.The tert-butyl groups in TPABuBr facilitate appropriate intermolecular spacing in the crystal state,enhancing oxygen permeability.Therefore,oxygen penetration can quench the phosphorescence emission.The observed linear relationship between the phosphorescence intensity of the doped material and the oxygen volume fraction conforms to the Stern-Volmer equation,suggesting its potential for quantitative analysis of oxygen concentration.The calculated limit of detection is 0.015%(φ),enabling the analysis of oxygen with a volume fraction of less than 2.5%(φ).Moreover,the doped materials demonstrate rapid response and excellent photostability,indicating their potential utility as oxygen sensors.This study elucidates the design and characteristics of NIBr/TPABuBr doped materials,highlighting their potential application in oxygen concentration detection and offering insights for the design of oxygen sensors.

Hydrogen-Bonded Supramolecular Network Triggers High-Efficiency Blue Room-Temperature Phosphorescence

Hydrogen bonding has been employed to suppressnonradiative decay in organic compounds that showroom-temperature phosphorescence (RTP);however, the small number of structurally diverse examplesmakes it unclear how general this strategy is to turnon RTP. In this study, we report highly efficient blueRTP from 4,4′,4′′-nitrilotribenzoic acid (TPA-CO_(2)H)in five structurally and chemically distinct hydrogenbonded supramolecular networks. In doped films inpoly(vinyl alcohol) (PVA), the phosphorescencequantum yield and lifetime (ΦPh and τPh) reach 52%and 275 ms. Boric acid can also be used to turn onRTP, and the performance changes significantlywhen the sample is heated beyond the dehydrationtemperature of this host where there is a 14-foldenhancement in the ΦPh after heat treatment. BlueRTP similar to that observed in PVA was also observed using granulated sugar, gelatine, and paper ashost matrices. This work elucidates for the first timethe role and the generality of hydrogen bonding inactivating efficient blue RTP and examines how thechoice of hydrogen bonding host influences RTPperformance. We further demonstrate how the emission color can be tuned by codoping the films withRhodamine 6G.

Responsive organic room-temperature phosphorescence materials for spatial-time-resolved anti-counterfeiting

Stimulus-responsive room-temperature phosphorescence(RTP)materials have gained significant attention for their important optoelectronic application prospects.However,the fabrication strategy and underlying mechanism of stimulus-responsive RTP materials remain less explored.Herein,we present a reliable strategy for achieving pH-responsive RTP materials by integrating poly(vinyl alcohol)(PVA)with carboxylic acid or amino group functionalized terpyridine(Tpy)derivatives.The resulting Tpy derivativesbased RTP materials displayed reversible changes in emission color,intensity,and lifetime of both prompt and delayed emission.Notably,the RTP emission undergoes a significant diminish upon exposure to acid due to the protonation of Tpy units.Taking advantage of the decent RTP emission and pH-responsiveness of these RTP films,a spatial-time-resolved anti-counterfeiting application is demonstrated as a proof-ofconcept for largely enhancing the security level.This study not only provides new prospects for developing smart RTP materials but also promotes the advancement of optical anti-counterfeiting applications.

Eco-friendly fractionation of natural straws:sustainable ultralong room-temperature phosphorescence and super anti-ultraviolet materials

We demonstrate a new green solvent consisting of ionic liquid and polyol to achieve a selective fractionation of lignin from biomass.The lignin from corn straw is rich in syringyl unit and phenolic hydroxyl group,resulting in excellent room-temperature phosphorescence(RTP)performance,antioxidation property and long-term photostability.Flexible film,fiber,aerogel and coatings with an ultralong RTP lifetime of 0.654 s are obtained.The lignin from corn straw completely blocks UV light of290–400 nm at an extremely low usage due to many p-coumarate units.When the content is as low as 1.54 mg/g,which is two orders of magnitude lower than the previous reports,the corresponding sunscreen cream has a super-high sun protection factor(SPF)of 183.9.More importantly,the lignin self-assembles into nanospheres of 250–350 nm,preventing penetration into the skin.Such easily-available,abundant,low-cost,safe and natural lignin provides an innovative avenue for sustainable optical function materials.

Organic Host-Guest Materials with Bright Red Room-Temperature Phosphorescence for Persistent Bioimaging

Organic room-temperature phosphorescence(RTP)materials have attracted immense attention in bioimaging due to their long emission lifetime and large Stokes shift.RTP materials with long emission wavelength can improve the penetration depth for bioimaging.However,the design of red persistent RTP materials is still challenging.In this study,a fused-ring structure has been proposed to effectively decrease the triplet energy level,thus extending the emission wavelength of phosphorescence.In addition,the fused-ring structure exhibits a high molar extinction coefficient(ɛ)and high luminescence efficiency due to the rigid structure.A new class of crystalline hosts(iminodibenzyl,IDB)are developed to stabilize the triplet excitons that are generated from the fused-ring molecules.The maximum RTP wavelength of doping materials can reach 635 nm with a lifetime of 9.35 ms.Water-disperse nanoparticles are successfully prepared for in vivo time-resolved bioimaging,which eliminates the background fluorescence interference from biological tissues.These reveal a delicate design strategy for the construction of long-wavelength emissive RTP materials for high-resolution bioimaging.

Recent Advances in Organic Room-Temperature Phosphorescence of Heteroatom(B/S/P)-Containing Chromophores

Purely organic room-temperature phosphors,which have received extensive attention as emerging stateof-the-art luminescent materials in various fields,have a longer lifetime than fluorophores.The energy gap law and El-Sayed’s rule provide clear design principles for the development of organic room-temperature phosphorescence.Therefore,the incorporation of heteroatoms(such as sulfur and phosphorus)usually promotes the intersystem crossing rate and increases the 3(π,π*)configuration to realize long lifetimes.Furthermore,boron-containing phosphors not only display excellent phosphorescence properties but also expand El-Sayed’s rule without(n,π*)transitions.This review summarizes recent work on organic phosphorescence of heterocycles with boron,sulfur,and phosphorus heteroatoms and highlights the significance of the guidelines for constructing efficient phosphorescence molecules.This work is instrumental in further diversifying the pool of phosphorescent molecules and developing new and effective design strategies.

Generation of color-controllable room-temperature phosphorescence via luminescent center engineering and in-situ immobilization

Materials with controllable luminescence colors are highly desirable for numerous promising applications, however, the preparation of such materials, particularly with color-controllable room-temperature phosphorescence(RTP), remains a formidable challenge. In this work, we reported on a facile strategy to prepare color-controllable RTP materials via the pyrolysis of a mixture containing 1-(2-hydroxyethyl)-urea(H-urea) and boric acid(BA). By controlling the pyrolysis temperatures, the as-prepared materials exhibited ultralong RTP with emission colors ranging from cyan, green, to yellow. Further studies revealed that multiple luminescent centers formed from H-urea, which were in-situ embedded in the B2O3matrix(produced from BA) during the pyrolysis process. The contents of the different luminescent centers could be regulated by the pyrolysis temperatures, resulting in color-tunable RTP. Significantly, the luminescent center engineering and in-situ immobilization strategy not only provided a facile method for conveniently preparing color-controllable RTP materials, but also endowed the materials prepared at relatively lower temperatures with color-changeable RTP features under thermal stimulus. Considering their unique properties, the potential applications of the as-obtained materials for advanced anti-counterfeiting and information encryption were preliminarily demonstrated.

A gated strategy stabilizes room-temperature phosphorescence

Room-temperature phosphorescence(RTP)of purely organic materials is easily quenched with unexpected purposes because the excited triplet state is extremely susceptible to external stimuli.How to stabilize the RTP property of purely organic luminogens is still challenging and considered as the bottleneck in the further advancement of the bottom-up approach.Here,we describe a gated strategy that can effectively harness RTP by employing complexation/dissociation with proton.Due to the order-disorder transition orientation of intermolecular packing,the RTP of organic molecules 2,4,6-tris(4′-bromo-[1,1′-biphenyl]-4-yl)-1,3,5-triazine(Br-TRZ)will easily vanish upon mechanical force.Impressively,by enhancing its intramolec-ular charge transfer effect,the protonated Br-TRZ stubbornly possesses an obvious RTP under external grinding,whatever in the ordered or disordered intermolec-ular arrangement state.Consequently,the“Lock”gate of RTP was achieved in the protonated Br-TRZ molecule.Combined with theoretical calculation analy-sis,the enhanced charge transfer effect can narrow the energy gap singlet-tripletsignificantly,and stabilize the RTP property of triazine derivative sequentially.Fur-thermore,the locked RTP can be tuned via proton and counterions repeatedly and show excellent reversibility.This gated RTP concept provides an effective strategy for stabilizing the RTP emission of purely organic systems.

Effect of stereoregularity on excitation-dependent fluorescence and room-temperature phosphorescence of poly(2-vinylpyridine)

Preparation of non-conjugated luminescent polymers(NCLPs)with excellent cluster luminescence(CL)performance is of great significance for scientific and industrious applications,and yet improving the performance of NCLPs through proper structural design is still a huge challenge.Herein,we report a non-conjugated ionized polymeric system consisting of(−)-camphorsulfonic acid((−)-CSA)and poly(2-vinylpyridine)(P2VP).These acid-base complexes exhibit typical excitationdependent fluorescence and room-temperature phosphorescence(RTP)with a lifetime up to 364 ms.We discover that changing the stereoregularity from atactic to isotactic significantly improves the CL performance of the complex.It(1)broadens the fluorescence emission spectra to cover the entire visible region,(2)enhances the fluorescence emission intensity at long wavelength beyond 500 nm,(3)enhances the phosphorescence intensity,and(4)extends the phosphorescence lifetime.Systematical experimental characterization and molecular dynamics simulation unravel the key role of stereoregularity in determining the formation of different pyridine aggregates that strongly influence the CL performance.Moreover,the different luminescence shows great potential in excitation divided information display and time-resolved encrypted display.This work not only points to a new direction for developing NCLPs with excellent performance,but also broadens the applications of NCLPs materials.

Colorful ultralong room-temperature phosphorescence in dual-ligand metal-organic framework

Long afterglow organic-inorganic hybrid materials have attracted much attention in recent years and are widely used in information security, biological imaging and many other fields. Since up-conversion long-persistence materials are promising for bio-optical imaging due to their high penetration depth and elimination of autofluorescence background, it is highly desirable to combine down-conversion and up-conversion pathways to obtain smart materials with excitation-dependent tunable room-temperature phosphorescence properties. In this work, a metal-organic framework(Zn-DCPS-BIMB), consisting of divalent zinc ions, o-bis(imidazol-1-ylmethyl)benzene and 4,4-dicarboxydiphenylsulfone, is designed to stabilize triplet excitons, coordinate the emission of different ligands, and endow materials with tunable emission color and up-conversion properties via heavy atoms effects promoting single-triplet orbital coupling and intersystem crossing.

Room-temperature phosphorescence materials from crystalline to amorphous state

Room temperature phosphorescence(RTP)in metal-free organic materials has attracted considerable attention due to its rich excited state properties,high quantum efficiency,long luminescence lifetimes,etc.,showing great potential in organic optoelectronic devices,bioimaging,information anti-counterfeiting,and so forth.The crystals have excellent rigidity and clear molecular packing patterns,which can effectively avoid non-radiative transitions of excitons for phosphorescence enhancement.In the early stages,researchers paid great attention to the regulation of RTP performance in crystalline states.However,due to the complex preparation and poor processability of crystals,amorphous materials with RTP features have become a new research topic recently.This perspective aims to summarize the recent advances of RTP materials from crystalline to amorphous states,and analyze their molecular design strategies and luminescence mechanisms in detail.Finally,we prospect the future research directions of amorphous RTP materials.This perspective will provide a guideline for the future study of advanced RTP materials.

Multi-modal anti-counterfeiting and encryption enabled through silicon-based materials featuring pH-responsive fluorescence and room-temperature phosphorescence

Nano Research volume 13,pages1614–1619(2020)Cite this article 236 Accesses Metrics details Abstract Optical silicon(Si)-based materials are highly attractive due to their widespread applications ranging from electronics to biomedicine.It is worth noting that while extensive efforts have been devoted to developing fluorescent Si-based structures,there currently exist no examples of Si-based materials featuring phosphorescence emission,severely limiting Si-based wide-ranging optical applications.To address this critical issue,we herein introduce a kind of Si-based material,in which metal-organic frameworks(MOFs)are in-situ growing on the surface of Si nanoparticles(SiNPs)assisted by microwave irradiation.Of particular significance,the resultant materials,i.e.,MOFs-encapsulated SiNPs(MOFs@SiNPs)could exhibit pH-responsive fluorescence,whose maximum emission wavelength is red-shifted from 442 to 592 nm when the pH increases from 2 to 13.More importantly,distinct room-temperature phosphorescence(maximum emission wavelength:505 nm)could be observed in this system,with long lifetime of 215 ms.Taking advantages of above-mentioned unique optical properties,the MOFs@SiNPs are further employed as high-quality anti-counterfeiting inks for advanced encryption.In comparison to conventional fluorescence anti-counterfeiting techniques(static fluorescence outputs are generally used,thus being easily duplicated and leading to counterfeiting risk),pH-responsive fluorescence and room-temperature phosphorescence of the resultant MOFs@SiNPs-based ink could offer advanced multi-modal security,which is therefore capable of realizing higher-level information security against counterfeiting.

A facile and green strategy to obtain organic room-temperature phosphorescence from natural lignin

Seeking pure organic functional luminescent materials that are processed from green, low-cost, and sustainable resources remains a challenging but beneficial task. As an abundant natural polymer composed of crosslinked phenol ether units, lignin is a potential source of organic luminescent material because of the presence of extensive aromatic fragments. In the present work, a remarkable afterglow involving room-temperature phosphorescence(RTP) was achieved via simply embedding alkalized lignin into polyvinyl alcohol(PVA) matrix, and an ultralong luminescence lifetime of more than 160 ms was observed. More importantly, our study revealed that small fragments of hydrolyzed lignin(named LA-H) bearing extensive phenolic oxygen anions were the effective luminescent species. When embedded into a PVA matrix, LA-H showed remarkably high luminescence quantum yield and long lifetime of RTP emission compared with those of unprocessed lignin. Additionally, the various phenol oxygen anion moieties endowed LA-H with an excitation-dependent characteristic: the color-tunable RTP could be simply tuned from a maximum emission wavelength of 434–532 nm via altering the excitation wavelength. Thus, the color-tunable afterglow of emissive LA-H could be facilely obtained with a yield up to 38.4% using simple acid hydrolysis of lignin without other complex synthesis procedures. This work opens new avenues in the large-scale preparation of low-cost and sustainable pure organic RTP materials.