Ultralong Room Temperature Phosphorescence Research Articles

Combining π-conjugated groups by flexible alkyl chains for ultralong organic phosphorescence by photo-activation

Purely organic luminescent materials with ultralong room temperature phosphorescence by photo-activation have attracted great interest owing to their advantages of clean, safe, easy-to-use and control. Herein, we designed and synthesized a series of ultralong room temperature phosphorescence carbazole derivatives using flexible alkyl with different lengths to adjust the distance between two conjugated carbazole groups. Only, CzC3Cz crystal has the dynamic ultralong organic phosphorescence with increasing the excitation time of 365 nm UV light. By prolonging the UV excitation time (from 5 s to 3 min), room temperature phosphorescence intensity was improved about 10 times and phosphorescence lifetime increased from 48 ms to 898 ms. Additionally, it exhibited favorable stability and repeatability. Comparing the single crystal structure before and after photo-activation, intermolecular interaction of π···π and C–H···π bond strengthens indicating that metastable state appears after long-time excitation of UV light. Considering the photo-activation characteristic, encryption pattern was prepared using the sifted compounds with similar phosphorescence performance for the application of anti-counterfeiting.

Resonance-Induced Stimuli-Responsive Capacity Modulation of Organic Ultralong Room Temperature Phosphorescence.

Organic ultralong room temperature phosphorescence (OURTP) materials having stimuli-responsive attributes have attracted great attention due to their great potential in a wide variety of advanced applications. It is of fundamental importance but challengeable to develop stimuli-responsive OURTP materials, especially such materials with modulated optoelectronic properties in a controlled manner probably due to the lack of an authentic construction approach. Here, we propose an effective strategy for OURTP materials with controllably regulated stimuli-responsive properties by engineering the resonance linkage between flexible chain and phosphor units. A quantitative parameter to demonstrate the stimuli-responsive capacity is also established by the responsivity rate constant. The designed OURTP materials demonstrate efficient photoactivated OURTP with lifetimes up to 724 ms and tunable responsivity rate constants ranging from 0.132 to 0.308 min-1 upon continuous UV irradiation. Moreover, the applications of stimuli-responsive resonance OURTP materials have been illustrated by the rewritable paper for snapshot and Morse code for multiple information encryption. Our works, which enable the accomplishment of OURTP materials capable of on-demand manipulated optical properties, demonstrate a viable design to explore smart OURTP materials, giving deep insights into the dynamically stimuli-responsive process.

Stimulus-responsive room temperature phosphorescence materials with full-color tunability from pure organic amorphous polymers.

Achieving stimulus-responsive ultralong room temperature phosphorescence (RTP) in organic materials especially with full-color tunable emissions is attractive and important but rarely reported. Here, a strategy was reported to realize stimulus-responsive RTP effect with color-tunable emissions by using water as solvent in the preparation process without any organic solvent through covalent linkage of arylboronic acids with different π conjugations and polymer matrix of polyvinyl alcohol. The yielded polymer films exhibit outstanding RTP performance (2.43 s). Furthermore, an excitation-dependent RTP film was obtained, and the afterglow color changes from blue to green, then to red as the excitation wavelength increases. The RTP property of all the above materials is sensitive to water and heat stimuli, because the rigidity of the system could be broken by water. Last, they were successfully applied in a multilevel information encryption and multicolor paper and ink.

Light/Force‐Sensitive 0D Lead‐Free Perovskites: From Highly Efficient Blue Afterglow to White Phosphorescence with Near‐Unity Quantum Efficiency

Herein, new types of zero-dimensional (0D) perovskites (PA6InCl9 and PA4InCl7) with blue room-temperature phosphorescence (RTP) were obtained from InCl3 and aniline hydrochloride. These are highly sensitive to external light and force stimuli. The RTP quantum yield of PA6InCl9 can be enhanced from 25.2 % to 42.8 % upon illumination. Under mechanical force, PA4InCl7 exhibits a phase transform to PA6InCl9, thus boosting ultralong RTP with a lifetime up to 1.2 s. Furthermore, white and orange pure RTP with a quantum yield close to 100 % can be realized when Sb3+ was introduced into PA6InCl9. The white pure phosphorescence with a color-rendering index (CRI) close to 90 consists of blue RTP of PA6InCl9 and orange RTP of Sb3+ . Thus, this work not only overcomes long-standing problems of low quantum yield and short lifetime of blue RTP, but also obtains high-efficiency white RTP. It provides a feasible method to realize near-unity quantum efficiency and has great application potential in the fields of optical devices and smart materials.

Light/Force‐Sensitive 0D Lead‐Free Perovskites: From Highly Efficient Blue Afterglow to White Phosphorescence with Near‐Unity Quantum Efficiency

AbstractHerein, new types of zero‐dimensional (0D) perovskites (PA6InCl9 and PA4InCl7) with blue room‐temperature phosphorescence (RTP) were obtained from InCl3 and aniline hydrochloride. These are highly sensitive to external light and force stimuli. The RTP quantum yield of PA6InCl9 can be enhanced from 25.2 % to 42.8 % upon illumination. Under mechanical force, PA4InCl7 exhibits a phase transform to PA6InCl9, thus boosting ultralong RTP with a lifetime up to 1.2 s. Furthermore, white and orange pure RTP with a quantum yield close to 100 % can be realized when Sb3+ was introduced into PA6InCl9. The white pure phosphorescence with a color‐rendering index (CRI) close to 90 consists of blue RTP of PA6InCl9 and orange RTP of Sb3+. Thus, this work not only overcomes long‐standing problems of low quantum yield and short lifetime of blue RTP, but also obtains high‐efficiency white RTP. It provides a feasible method to realize near‐unity quantum efficiency and has great application potential in the fields of optical devices and smart materials.

Completely aqueous processable stimulus responsive organic room temperature phosphorescence materials with tunable afterglow color

Many luminescent stimuli responsive materials are based on fluorescence emission, while stimuli-responsive room temperature phosphorescent materials are less explored. Here, we show a kind of stimulus-responsive room temperature phosphorescence materials by the covalent linkage of phosphorescent chromophore of arylboronic acid and polymer matrix of poly(vinylalcohol). Attributed to the rigid environment offered from hydrogen bond and B-O covalent bond between arylboronic acid and poly(vinylalcohol), the yielded polymer film exhibits ultralong room temperature phosphorescence with lifetime of 2.43 s and phosphorescence quantum yield of 7.51%. Interestingly, the RTP property of this film is sensitive to the water and heat stimuli, because water could destroy the hydrogen bonds between adjacent poly(vinylalcohol) polymers, then changing the rigidity of this system. Furthermore, by introducing another two fluorescent dyes to this system, the color of afterglow with stimulus response effect could be adjusted from blue to green to orange through triplet-to-singlet Förster-resonance energy-transfer. Finally, due to the water/heat-sensitive, multicolor and completely aqueous processable feature for these three afterglow hybrids, they are successfully applied in multifunctional ink for anti-counterfeit, screen printing and fingerprint record.

Ultralong room temperature phosphorescence and ultraviolet fluorescence from simple triarylphosphine oxides

Ultralong room temperature phosphorescence of simple triarylphosphine oxides is reported. The lone pair electrons on the P in triarylphosphines facilitate faster intersystem crossing than those on the O of the P=O moiety in triarylphosphine oxides.

Ultralong room-temperature phosphorescence from polycyclic aromatic hydrocarbons by accelerating intersystem crossing within a rigid polymer network

A water-resistance polymer-based room temperature phosphorescence material (RTP) with an ultralong lifetime and afterglow was achieved by doping PAHs within a rigid polymeric network duringin situpolymerization.

Unveiling the crucial contributions of electrostatic and dispersion interactions to the ultralong room-temperature phosphorescence of H-bond crosslinked poly(vinyl alcohol) films.

Organic phosphors exhibiting room-temperature phosphorescence (RTP) in the amorphous phase are promising candidates for optoelectronic and biomedical applications. In particular, noncovalently embedding organic phosphors into a poly(vinyl alcohol) (PVA) matrix has emerged as the most commonly used yet effective approach to obtain amorphous organic RTP materials. While the role of intermolecular hydrogen-bonding interactions in determining the RTP properties of doping PVA systems has been well documented, we show that electrostatic and dispersion interactions contribute crucially to the ultralong RTP properties of doping PVA films. This impressive outcome reveals the nature of non-covalent interactions existing in doping PVA systems for the first time. We demonstrate this through detailed experimental and computational studies for a series of hydrogen-bond crosslinked PVA films where star-shaped organic phosphors containing active groups of carboxy, hydroxy, and amino act as multisite crosslinkers for the construction of extensive hydrogen-bonding networks. More importantly, we successfully obtain an ultralong RTP lifetime of up to 1.74 s by tuning the electrostatic and dispersion interactions between organic phosphors and the PVA matrix through simply modifying active groups of organic phosphors. This instructive work will provide new guiding principles for the exploration of amorphous organic RTP systems.

Cluster-luminescent polysiloxane nanomaterials: adjustable full-color ultralong room temperature phosphorescence and a highly sensitive response to silver ions

Non-conjugated polysiloxane nanomaterials with amino and urea groups show persistent cluster-induced phosphorescence regulated by doping different small molecules, and fluorescence/phosphorescence dual responses to Ag+ in aqueous solutions.

Fast photostimulus-responsive ultralong room-temperature phosphorescence behaviour of benzoic acid derivatives@boric acid

A series of ultralong RTP materials with photostimulus-responsive behavior were prepared by facile doping processes.

Chelation-activated ultralong room-temperature phosphorescence and thermo-/excitation-dependent persistent luminescence.

Multidentate chelation effect can be used to activate the ultralong room-temperature phosphorescence and stabilize the triplet excitons. The as-synthesized cadmium(II) based complexes further exhibit thermo- and excitation-dependent persistent luminescence as potential for optical logic gate.

Tailored Fabrication of Carbon Dot Composites with Full-Color Ultralong Room-Temperature Phosphorescence for Multidimensional Encryption.

Ultralong room‐temperature phosphorescence (RTP) is highly useful for information encryption, organic electronics, bioelectronics, etc. However, the preparation of related metal‐free materials with multiple colors across the full spectrum remains a major challenge. Herein, a facile method is developed to fabricate boron‐doped carbon dot (B‐CD) composites with full‐color long lifetime RTP continuously tailorable in the range of 466–638 nm simply by pyrolysis of the citric acid and boric acid precursors with various mass ratios at different temperatures. This leads to the formation of luminescent B‐CD centers in a rigid polycrystalline B2O3 matrix, which effectively stabilizes the triplet excited states of B‐CDs. Thus, the composites become phosphorescent over a relatively long period (5–12 s) after the removal of the irradiation source. Meanwhile, the increased particle size and oxidation degree of B‐CDs obtained at larger citric acid feeding or higher pyrolysis temperature continuously shift the phosphorescence from blue to red. Due to the formation of multiple luminescence centers, the RTP can also be finely modulated by the excitation wavelength. The resulting B‐CD composites with highly tunable long lifetime RTP further allow a variety of distinctive applications in multidimensional encryption handily utilizing space, time, and color variations.

Ultralong lifetime room-temperature phosphorescence in aqueous medium from silica confined polymer carbon dots for autoluminescence-free bioimaging and multilevel information encryption

Ultralong room-temperature phosphorescence (URTP) materials have innate superiority in eliminating autoluminescence for bioimaging, but achieving URTP in aqueous medium is a highly challenging task, especially for carbon dot-based materials. Here we present a facile one-step hydrothermal method to effectively promote RTP emission in an aqueous medium by confining polymer carbon dots (PCDs) in silica nanospheres (SNSs) with tetraethylorthosilicate as only raw material. The polymer carbon dots-silica nanosphere composites (PCDs-SNSs) exhibit ultralong lifetime up to 2.19 s (nearly 9 s to naked eye) at ambient temperature and atmosphere. To the best of our knowledge, this is the longest RTP lifetime of carbon dot-based materials in aqueous media to date. As indicated, RTP should originate from the subfluorescent CO groups. The shielding of SNSs to all kinds of quenching in the confined space in which there are strong interactions between PCDs and SNSs, e.g, covalent bond and hydrogen bond, which enhances the rigidity of cross-linked framework and protects emitting centers from non-radiative deactive processes of triplet state, is the main reason for the URTP observed in aqueous media. Besides, the PCDs-SNSs solution exhibits outstanding stability and low cytotoxicity. Based on the distinctive properties in aqueous media, the PCDs-SNSs have been successfully used as autoluminescence-free probes for bioimaging with high sensitivity and signal-to-noise ratio, and as security ink for strong concealment and moisture-related multilevel information protection.

Water‐Induced Blue‐Green Variable Nonconventional Ultralong Room Temperature Phosphorescence from Cross‐Linked Copolymers via Click Chemistry

AbstractUltralong room temperature phosphorescence is employed in information encryption, chemical sensing, lighting, and imaging on account of its long lifetime and high signal‐to‐noise ratio. As the triplet excitons can be easily quenched and interfered by nonradiative transition process, it is difficult to obtain long‐lived phosphorescence through conventional methods. Herein, a general design strategy to form cross‐linked networks by click chemistry is presented for efficiently promoting the phosphorescence performance. Using the hydrogen bonding interactions formed between CO···HN units and covalently cross‐linked network by the BO bond, the rigidity of the entire system is greatly enhanced, so the radiative transition process is well strengthened. Interestingly, under the influence of water molecule, the afterglow colors of the system change from blue (488 nm) to green (510 nm). Because of the presence of cross‐linked network, the emission is not directly quenched when the system is intervened by water. Having long phosphorescence lifetime (841.06 ms) and high quantum yield (10.48%), the obtained system is utilized for anti‐counterfeiting demonstration. This strategy paves a new way for the design of amorphous ultralong room temperature phosphorescence materials by efficient and user‐friendly click chemistry.

Theoretical Insight Into the Ultralong Room-Temperature Phosphorescence of Nonplanar Aromatic Hydrocarbon.

Purely aromatic hydrocarbon materials with ultralong room-temperature phosphorescence (RTP) were reported recently, but which is universally recognized as unobservable. To reveal the inherent luminescent mechanism, two compounds, i.e., PT with a faint RTP and HD with strong RTP featured by nonplanar geometry, were chosen as a prototype to study their excited-state electronic structures by using quantum mechanics/molecular mechanics (QM/MM) model. It is demonstrated that the nonplanar ethylene brides can offer σ-electron to strengthen spin-orbit coupling (SOC) between singlet and triplet excited states, which can not only promote intersystem crossing (ISC) of S1→Tn to increase the population of triplet excitons, but also accelerate the radiative decay rate of T1→S0, and thus improving RTP. Impressively, the nonradiative decay rate only has a small increase, owing to the synergistic effect between the increase of SOC and the reduction of reorganization energy of T1→S0 caused by the restricted torsional motions of aromatic rings. Therefore, a bright and long-lived RTP was obtained in aromatic hydrocarbon materials with twisted structure. This work provided a new insight into the ultralong RTP in pure organic materials.

Ultralong Polymeric Room Temperature Phosphorescence Materials Fabricated by Multiple Hydrogen Bondings Resistant to Temperature and Humidity

AbstractPolymeric room temperature phosphorescence (RTP) materials have attracted tremendous attentions owing to their excellent flexibility, easy processing, low cost, and good thermal stability. In this work, an improved strategy is proposed for ultralong RTP polymeric materials through copolymerizing the phosphor monomer with D (donor)−A (acceptor) structure and another monomer with ultrastrong multiple hydrogen bonds. A series of copolymers (P1–P4) containing different ratios of carbazole‐dibenzofuran (CDF) and ureidopyrimidinone (UPy) segments are successfully prepared. The obtained copolymers show ultralong phosphorescence lifetimes between 1.70 and 2.16 s with afterglow duration time between 15 and 17 s. The multiple hydrogen bonds of UPy groups can promote extremely intermolecular and intramolecular interactions, which immobilize the phosphors to prevent nonradiative transitions. Especially, these interactions lead to the copolymers can be robustly resistant to high temperature and humidity. Flexible and foldable anti‐counterfeiting with high temperature and humidity resistant features are achieved, which would be applied in practical special environments.

Multifunctional Optical Polymeric Films with Photochromic, Fluorescent, and Ultra‐Long Room Temperature Phosphorescent Properties

AbstractPhotochromism, fluorescence, and ultra‐long room temperature phosphorescence (URTP) are attractive phenomena in photonics. However, achieving multiple optical properties such as photochromism, fluorescence, and URTP on one material still remains a challenge. Here, the authors report a multifunctional optical polymeric film with photochromic, fluorescent, and URTP properties, fabricated by simply doping the naphthopyran molecule into epoxy polymer with 3D network. When the polymer network is loose, the naphthopyran‐doped film exhibits photochromic property but no fluorescence and phosphorescence. When the polymer network becomes dense, the film shows fluorescent and URTP behaviors but no photochromic property. It is noted that the room temperature phosphorescence lifetime is as high as 604 ms. Based on the excellent optical properties of reversible photochromism, fluorescence, and URTP, an advanced sixfold encryption application has been successfully established. This work not only opens up a new direction in design and fabrication of multifunctional optical materials but also offers principles for developing organic optical materials toward multilevel information encryption and data storage.

Persistent Room‐Temperature Phosphorescence from Purely Organic Molecules and Multi‐Component Systems

AbstractRecently, luminophores showing efficient room‐temperature phosphorescence (RTP) have gained tremendous interest due to their numerous applications. However, most phosphors are derived from transition metal complexes because of their intrinsic fast intersystem crossing (ISC) induced by strong spin–orbit coupling (SOC) constants of the heavy metal. Metal‐free RTP materials are rare and have become a promising field because they are inexpensive and environmentally friendly. This review summarizes organic molecular materials with long triplet lifetimes at room temperature from the perspective of whether they stem from a molecular or multi‐component system. Among purely organic phosphors, heteroatoms are usually introduced into the backbone in order to boost the singlet–triplet ISC rate constant. In multi‐component systems, useful strategies such as host–guest, polymer matrix, copolymerization, and supramolecular assembly provide a rigid matrix to restrict nonradiative pathways thus realizing ultralong RTP.

An Organic Host–Guest System Producing Room‐Temperature Phosphorescence at the Parts‐Per‐Billion Level

AbstractManipulation of long‐lived triplet excitons in organic molecules is key to applications including next‐generation optoelectronics, background‐free bioimaging, information encryption, and photodynamic therapy. However, for organic room‐temperature phosphorescence (RTP), which stems from triplet excitons, it is still difficult to simultaneously achieve efficiency and lifetime enhancement on account of weak spin–orbit coupling and rapid nonradiative transitions, especially in the red and near‐infrared region. Herein, we report that a series of fluorescent naphthalimides—which did not originally show observable phosphorescence in solution, as aggregates, in polymer films, or in any other tested host material, including heavy‐atom matrices at cryogenic temperatures—can now efficiently produce ultralong RTP (ϕ=0.17, τ=243 ms) in phthalimide hosts. Notably, red RTP (λRTP=628 nm) is realized at a molar ratio of less than 10 parts per billion, demonstrating an unprecedentedly low guest‐to‐host ratio where efficient RTP can take place in molecular solids.