Full-color Emission Research Articles

Loading Dyes into Chiral Cd/Zn-Metal-Organic Frameworks for Efficient Full-Color Circularly Polarized Luminescence.

Host-guest chemistry of chiral metal-organic frameworks (MOFs) has endowed them with circularly polarized luminescence (CPL), it is still limited for MOFs to systematically tune full-color CPL emissions and sizes. This work directionally assembles the chiral ligands, metal sites and organic dyes to prepare a series of crystalline enantiomeric D/L-Cd/Zn-n MOFs (n=1~5, representing the adding amount of dyes), where D/L-Cd/Zn with the formula of Cd2(D/L-Cam)2(TPyPE) and Zn2(D/L-Cam)2(TPyPE) (D/L-Cam=D/L-camphoric acid, TPyPE=4,4',4'',4'''-(1,2-henediidenetetra-4,1-phenylene)tetrakis[pyridine]) were used as the chiral platforms. The framework-dye-enabled emission and through-space chirality transfer facilitate D/L-Cd/Zn-n bright full-color CPL activity. The ideal yellow CPL of D-Cd-5 and D-Zn-4, with |glum| as 4.9 × 10-3 and 1.3×10-3 and relatively high photoluminescence quantum yield of 40.79 % and 45.40 %, are further assembled into a white CPL light-emitting diode. The crystal sizes of D/L-Cd/Zn-n were found to be strongly correlated to the types and additional amounts of organic dyes, that the positive organic dyes allow for the preparation of > 7 mm bulks and negative dyes account for sub-20 μm particles. This work opens a new avenue to fabricate full-color emissive CPL composites and provides a potentially universal method for controlling the size of optical platforms.

Bio-sourced flexible supramolecular glasses for dynamic and full-color phosphorescence

Glass, a diverse family of amorphous materials, has significantly advanced human society across various fields. The demand for flexible ultrathin glass, driven by modern optical displays and portable optoelectronics, presents challenges in energy consumption, fabrication complexity, and recycling. Here, we demonstrate flexibility and full-color luminescence in large-scale ultrathin glasses derived from readily available natural resources, specifically egg albumen (EA) and gelatin (GEL), via an evaporation-driven self-assembly process. The dynamic crosslinked networks formed through hydrogen bonding between EA and GEL impart both high hardness and flexibility to the glasses, with hardness and flexural strength values comparable to state-of-the-art inorganic and organic glasses. Additionally, the EA–GEL-based glasses exhibit excitation-dependent and time-gated chiral ultralong phosphorescence with color from blue and red, and a lifetime of up to 180.4 ms. With their easy processability and full-color emission, these biogenic glasses can be fabricated into anti-counterfeiting patterns and optical information codes.

Full-Color Emissive Zirconium-Organic Frameworks Constructed via in situ "One-Pot" Single-Site Modification for Tryptophan Detection and Energy Transfer.

Organic linker-based luminescent metal-organic frameworks (LMOFs) have received extensive studies due to the unlimited species of emissive organic linkers and tunable structure of MOFs. However, the multiple-step organic synthesis is always a great challenge for the development of LMOFs. As an alternative strategy, in situ "one-pot" strategy, in which the generation of emissive organic linkers and sequential construction of LMOFs happen in one reaction condition, can avoid time-consuming pre-synthesis of organic linkers. In the present work, we demonstrate the successful utilization of in situ "one-pot" strategy to construct a series of LMOFs via the single-site modification between the reaction of aldehydes and o-phenylenediamine-based tetratopic carboxylic acid. The resultant MOFs possess csq topology with emission covering blue to near-infrared. The nanosized LMOFs exhibit excellent sensitivity and selectivity for tryptophan detection. In addition, two component-based LMOFs can also be prepared via the in situ "one-pot" strategy and used to study energy transfer. This work not only reports the construction of LMOFs with full-color emissions, which can be utilized for various applications, but also indicates that in situ "one-pot" strategy indeed is a useful and powerful method to complement the traditional MOFs construction method for preparing porous materials with tunable functionalities and properties.

Unconventional Luminescence Polymer with Color-Tunability based on Solvent-Induced Electrostatic Potential Distribution of Fluorophore.

Tuning full-color emission of polymers holds significant promise. However, preparing unconventional luminescence polymers with color-tunability in dilute solution and understanding the relationship between non-covalent interactions and luminescent behavior remains a great challenge. We report two emitters (P1 and P2) incorporating tetracoordinate boron. The P1 with non-conjugated D-π-A structure, exhibited red delayed fluorescence at 645 nm with quantum yield of 9.15 % in aggregates. Notably, the emission wavelength of P1 can be tuned from 418 to 588 nm at different solvent. Similarly, the emission wavelength of P2 can also be adjusted by manipulating the interactions between the solvent and fluorophore. Experimental characterization and theoretical calculations indicate that the B←N bond and electronic interactions between solvent and fluorophore significantly regulate the equilibrium the electrostatic potential (ESP) and the intramolecular O⋅⋅⋅O interactions of P1, thereby modulating its emission wavelength. Additionally, these polymers showed excellent potential in fluoride ions detection. This work provides new insights into the complex effects of intermolecular interactions on luminescent properties.

Circularly Polarized Phosphorescence Energy Transfer Combined with Chirality-Selective Absorption for Modulating Full-Color and White Circularly Polarized Long Afterglow.

Circularly polarized long afterglow (CPLA) attracts great interests in multi-disciplinary fields with significant potentials in optical multiplexing applications, but achieving full-color and white CPLA is still challenging. The present contribution reports the first success in utilizing circularly polarized phosphorescence energy transfer (CPP-ET) combined with chirality-selective absorption (CSA) to construct full-color and white CPLA materials. Blue CPLA with luminescence dissymmetry factor (glum) of 3×10-2 is firstly obtained via the CSA effect of chiral helical polyacetylene and blue ultralong afterglow of inorganic phosphor BP. Significantly, full-color and white CPLA films are prepared by simply blending different fluorophores into the blue-CPLA films via CPP-ET. Benefited from the persistent luminescence of BP, the lifetimes of the fluorophores increase from nanoseconds to minutes, and ultralong full-color CPLA emissions lasting for more than 20 min are realized with glum of 10-3. Also noticeably, chiral optoelectronic devices, multi-dimension information encryption and chiral logic gate are developed based on the full-color tunable CPLA-active materials. The established strategy provides a universal platform for future development of CPLA-active materials with great applications.

Polymer Free Volume-Controlled Molecular Clock and Emitter for Multicolored Transient Data Display in Advanced Photonic Cryptography.

The booming demand on data security has aroused great interest for developing smart materials with temporal display feature and dynamic multicolor fluorescence. However, it remains challenging to implement both features on most responsive molecules. Herein, we construct a polymer free volume-controlled "molecular clock and emitter" via covalently embedding a multi-stimuli responsive molecular switch (i.e., spiropyran) into a polymer network (i.e., poly(pentafluorophenyl acrylate)) with programmable crosslink density and free volume. By the aminolysis of pentafluorophenyl ester with different amount of diamine crosslinkers, pPFPA-co-SP networks with controllable crosslink densities are generated, which have different confinement effects on the rate constant of SP/MC isomerization, thus leading to time-dependent photochromism. In addition, PTF1, a fluorescent probe that is sensitive to polymer rigidity, is introduced to further endow pPFPA-co-SP system with phototunable dynamic full-color emission. Therefore, relying on their synergistical responses to the rigidity of the polymer network, we have successfully developed a versatile molecular clock and emitter via an "one stone two birds" manner, which shows time-dependent data display along with dynamic multicolor fluorescence switching, providing great potential for advanced encryption and anticounterfeiting with a high security level.

Surface State Modulation via Electrochemical Heterogeneous Redox Reactions for Full-Color Emission Carbon Dots.

Carbon dots (CDs) still suffer from unclear surface state fluorescence mechanism for fine modulation. Here, redox reactions for cathode and anode within electrochemical method are firstly employed to construct differentiated strategy for surface-state modulation, so as to obtain CDs with controllable emission in separated electrodes simultaneously. The fluorescence peaks of CDs from blue to red centered at 425 nm (mCDs-), 530 nm (mCDs+), 580 nm (oCDs-) and 665 nm (oCDs+) are mainly originated from the different bombardment effects of the ions and reaction tendencies of modifier during the electrolysis process. The phenylenediamine (as modifier) tends to introduce the amino groups on the surface of CDs- while introduced nitrogen atoms into the carbon nucleus skeleton around the anode, thus leading to much larger size and the formation of the graphite N for CDs+. It is the different surface states formed by phenylenediamine and the absorption redshift triggered by graphite N that ensures the tunable emission. The improved electrochemical method is of great significance for finely spectra modulation and efficient synthesis.

A single phased full color emitting pyrochlore type phosphor La2Y0.66Sn0.66Sb0.66O7: Bi3+, Eu3+ for white light emitting diode applications (WLEDs)

The phosphor converted white light emitting diodes (pc-WLEDs) are advancing rapidly in replacing the conventional fluorescent and incandescent light sources. However, the current technology of pc-WLEDs limits their large scale indoor lighting applications due to their high correlated color temperature (CCT) and poor color rendering index (CRI). In this work, a single phased full color emitting phosphor in the pyrochlore oxide system, La2Y0.66Sn0.66Sb0.66O7: Bi3+, Eu3+ has been developed by the high temperature ceramic route. The developed phosphors are characterized by powder X-ray diffraction, luminescence and lifetime measurements. Upon near UV excitation wavelength, the singly doped phosphor, La2Y0.66Sn0.66Sb0.66O7: Bi3+ show intense blue green light in the wavelength region 400–600 nm due to the characteristic transitions (3P1 → 1S0) of Bi3+. The emission spectral analysis suggests that there exist two luminescence centers of Bi3+ due to occupation of different crystallographic sites in the pyrochlore lattice of La2Y0.66Sn0.66Sb0.66O7. The deficit of red component in the emission spectra is overcome by the Eu3+ co-doping in the system, La2Y0.66Sn0.66Sb0.66O7: Bi3+, Eu3+ which results in the full color emission covering the visible spectral range up to 700 nm with broad peaks along with sharp narrow characteristic peaks of Eu3+. The full color emission of the La2Y0.66Sn0.66Sb0.66O7: 0.04Bi3+, yEu3+ phosphors can be tuned by adjusting the suitable Eu3+ dopant concentration and using appropriate energy transfer from Bi3+ to Eu3+. The full color emitting phosphor, La2Y0.66Sn0.66Sb0.66O7:0.04Bi3+, 0.06Eu3+ can be realized with the color coordinates (0.30, 0.36), and correlated color temperature (4383K). All these results demonstrate that La2Y0.66Sn0.66Sb0.66O7:xBi3+, yEu3+ are potential single phased full color emitting phosphors for the development of pc-WLEDs.

An ultrawide-range photochromic molecular fluorescence emitter

Photocontrollable luminescent molecular switches capable of changing emitting color have been regarded as the ideal integration between intelligent and luminescent materials. A remaining challenge is to combine good luminescence properties with wide range of wavelength transformation, especially when confined in a single molecular system that forms well-defined nanostructures. Here, we report a π-expanded photochromic molecular photoswitch, which allows for the comprehensive achievements including wide emission wavelength variation (240 nm wide, 400–640 nm), high photoisomerization extent (95%), and pure emission color (<100 nm of full width at half maximum). We take the advantageous mechanism of modulating self-assembly and intramolecular charge transfer in the synthesis and construction, and further realize the full color emission by simple photocontrol. Based on this, both photoactivated anti-counterfeiting function and self-erasing photowriting films are achieved of fluorescence. This work will provide insight into the design of intelligent optical materials.

Achieving Colorful Ultralong-Lifetime Room-Temperature Phosphorescence Based on Benzocarbazole Derivatives through Resonance Energy Transfer.

It is of practical significance to develop polymer-based room-temperature phosphorescence (RTP) materials with ultralong lifetime and multicolor afterglow. Herein, the benzocarbazole derivatives were selected and combined with a poly(vinyl alcohol) (PVA) matrix by a coassembly strategy. Owing to the hydrogen-bonding interactions between benzocarbazole derivatives and the PVA matrix, the nonradiative transition and the quenching of triplet excitons are effectively inhibited. Therefore, the maximum phosphorescence emission lifetime of 2202.17 ms from ABfCz-PVA and the maximum phosphorescence quantum efficiency of 34.97% from ABtCz-PVA were obtained, respectively. In addition, commercially available dye molecules were selected to construct phosphorescent resonance energy transfer (PRET) systems for energy acceptors, enabling full-color afterglow emission in blue, green, yellow, red, and even white. Based on the characteristics of prepared RTP materials, multifunctional applications to flexibility, information encryption, and erasable drawing were deeply explored.

Organic Cocrystal Alloys: From Three Primary Colors to Continuously Tunable Emission and Applications on Optical Waveguides and Displays.

Multicolor luminescence of organic fluorescent materials is an essential part of lighting and optical communication. However, the conventional construction of a multicolor luminescence system based on integrating multiple organic fluorescent materials of a single emission band remains complicated and to be improved. Herein, organic alloys (OAs) capable of full-color emission are synthesized based on charge transfer (CT) cocrystals. By adjusting the molar ratio of electron donors, the emission color of the OAs can be conveniently and continuously regulated in a wide visible range from blue (CIE: 0.187, 0.277), to green (CIE: 0.301, 0.550), and to red (CIE: 0.561, 0.435). The OAs show analogous 1D morphology with smooth surface, allowing for full-color waveguides with low optical-loss coefficient. Impressively, full-color optical displays are easily achieved through the OAs system with continuous emission, which shows promising applications in the field of optical display and promotes the development of organic photonics.

Donor-donor-acceptor (D-D-A) luminogens containing a central carbazole core: Aggregation-induced emission (AIE), full-color solid-state emission and diverse mechanofluorochromic characteristics

The construction of multi-functionalized luminophores with full-color emission based on the same core skeleton is an appealing yet significantly challenging task. In this work, we rationally designed and facilely constructed a series of donor-donor-acceptor (D-D-A) based luminogens by representative Suzuki-Miyaura cross-coupling reaction. Using electron-donating carbazole with hexyl chain as basic core structure, a series of donor-donor-acceptor (D-D-A) typed luminogens with different donor and acceptor units were designed and synthesized. Some compounds showed AIEE or aggregate fluorescence change behaviors due to TICT and RIM. Among them, these compounds displayed diverse mechanofluorochromic characteristics, including reversible or irreversible, red-shifted or blue-shifted mechanofluorochromisms. This provided new ideas for the development of multifunctional organic light-emitting molecules.

Integrating Full-Color 2D Optical Waveguide and Heterojunction Engineering in Halide Microsheets for Multichannel Photonic Logical Gates.

Ensuring information security has emerged as a paramount concern in contemporary human society. Substantial advancements in this regard can be achieved by leveraging photonic signals as the primary information carriers, utilizing photonic logical gates capable of wavelength tunability across various time and spatial domains. However, the challenge remains in the rational design of materials possessing space-time-color multiple-resolution capabilities. In this work, a facile approach is proposed for crafting metal-organic halides (MOHs) that offer space-time-color resolution. These MOHs integrate time-resolved room temperature phosphorescence and color-resolved excitation wavelength dependencies with both space-resolved ex situ optical waveguides and in situ heterojunctions. Capitalizing on these multifaceted properties, MOHs-based two-dimensional (2D) optical waveguides and heterojunctions exhibit the ability to tune full-color emissions across the spectra from blue to red, operating within different spatial and temporal scales. Therefore, this work introduces an effective methodology for engineering space-time-color resolved MOH microstructures, holding significant promise for the development of high-density photonic logical devices.

Dual-state emissive imidazo[1,2-α]pyridines with full color emission, acidochromism, viscosity-dependent fluorescence, and bioimaging applications

Five novel dual-state emissive imidazo[1,2-α]pyridine-based luminogens IP1-5 were rationally designed and prepared by varying the conjugation length and the nature of donor-acceptor (D-A) units. These D-A chromophores displayed cyan, green, yellow, and red fluorescence in the solid state, with full-color emission achieved for the first time through modification of imidazo[1,2-α]pyridine core. Interestingly, IP1 and IP5 in the solid state exhibited an abnormal remarkable blue-shift emission compared with those in THF, probably due to the highly twisted molecular conformations and solvent effect by theoretical calculations as well as crystal structure analyses. Importantly, IP1-5 revealed remarkable reversible acid-induced acidichromism, accompanied with dual change of colorimetric and fluorometric determination. Viscosity-dependent fluorescence was next conducted, indicting IP1-3 can be utilized for local viscosity detection. Moreover, IP1-5 served as promising candidates for multicolor bioimaging with low cell toxicity and good biocompatibility.

Bioinspired polymeric supramolecular columns as efficient yet controllable artificial light-harvesting platform

Light-harvesting is an indispensable process in photosynthesis, and researchers have been exploring various structural scaffolds to create artificial light-harvesting systems. However, achieving high donor/acceptor ratios for efficient energy transfer remains a challenge as excitons need to travel longer diffusion lengths within the donor matrix to reach the acceptor. Here, we report a polymeric supramolecular column-based light-harvesting platform inspired by the natural light-harvesting of purple photosynthetic bacteria to address this issue. The supramolecular column is designed as a discotic columnar liquid crystalline polymer and acts as the donor, with the acceptor intercalated within it. The modular columnar design enables an ultrahigh donor/acceptor ratio of 20000:1 and an antenna effect exceeding 100. Moreover, the spatial confinement within the supramolecular columns facilitates control over the energy transfer process, enabling dynamic full-color tunable emission for information encryption applications with spatiotemporal regulation security.

Rational Design of Full-Color Fluorescent C3N Quantum Dots.

Carbon-based quantum dots (QDs) exhibit unique photoluminescence due to size-dependent quantum confinement, giving rise to fascinating full-color emission properties. Accurate emission calculations using time-dependent density functional theory are a time-costing and expensive process. Herein, we employed an artificial neural network (ANN) combined with statistical learning to establish the relationship between geometrical/electronic structures of ground states and emission wavelength for C3N QDs. The emission energy of these QDs can be doubly modulated by size and edge effects, which are governed by the number of C4N2 rings and the CH group, respectively. Moreover, these two structural characteristics also determine the phonon vibration mode of C3N QDs to harmonize the emission intensity and lifetime of hot electrons in the electron-hole recombination process, as indicated by nonadiabatic molecular dynamics simulation. These computational results provide a general approach to atomically precise design the full-color fluorescent carbon-based QDs with targeted functions and high performance.

Helical-caging enables single-emitted large asymmetric full-color circularly polarized luminescence

Colorful circularly polarized luminescence materials are desired for 3D displays, information security and asymmetric synthesis, in which single-emitted materials are ideal owing to self-absorption avoidance, evenly entire-visible-spectrum-covered photon emission and facile device fabrication. However, restricted by the synthesis of chiral broad-luminescent emitters, the realization and application of high-performing single-emitted full-color circularly polarized luminescence is in its infancy. Here, we disclose a single-emitted full-color circularly polarized luminescence system (spiral full-color emission generator), composed of whole-vis-spectrum emissive quantum dots and chiral liquid crystals. The system achieves a maximum luminescence dissymmetry factor of 0.8 and remains an order of 10−1 in visible region by tuning its photonic bandgap. We then expand it to a series of desired customized-color circularly polarized luminescence, build chiral devices and further demonstrate the working scenario in the photoinduced enantioselective polymerization. This work contributes to the design and synthesis of efficient chiroptical materials, device fabrication and photoinduced asymmetric synthesis.

A Universal Approach Toward Intrinsically Flexible All-Inorganic Perovskite-Gel Composites with Full-Color Luminescence.

The combination of all-inorganic perovskites (PVSKs) and polymers allows for free-standing flexible optoelectronic devices. However, solubility difference of the PVSK precursors and concerns over the compatibility between polymer carriers and PVSKs imply a great challenge to incorporate different kinds of PVSKs into polymer matrices by the same manufacturing process. In this work, PVSK precursors are introduced into poly(2-hydroxyethyl acrylate) (PHEA) hydrogels in sequence, in which the PVSK-gel composites are achieved with full-color emissions by simply varying the precursor species. Moreover, it is found that CsBr has a higher interaction energy with the (111) plane of CsPbBr3 than the (110) plane; thus, the CsPbBr3 crystals with a shape of truncated cube and tetragon are observed during the CsPbBr3-Cs4PbBr6 phase transition over time. The PVSK-gel composites feature excellent bendability, elasticity, and stretchable deformation (tensile strain > 500%), which allows for 3D printing emissive customized stereoscopic architectures with shape-memory features.

Large-scale and flexible circularly polarized room temperature phosphorescence with a high dissymmetry factor and chiral sensing

&lt;p&gt;Circularly polarized luminescence (CPL) materials have attracted great attention because of their rich optical information and excellent sensitivity. However, the strategy to prepare CPL materials with a high dissymmetry factor (&lt;i&gt;g&lt;/i&gt;) is still limited. Herein, we demonstrate a facile route to scale up the fabrication of circularly polarized organic room-temperature phosphorescent (CP-RTP) materials with a high &lt;i&gt;g&lt;/i&gt; value, outstanding flexibility and complete biodegradability, via the reconstruction and enhancement of hydrogen-bonding interactions of cellulose. The absorption dissymmetry factor (g&lt;sub&gt;&lt;i&gt;abs&lt;/i&gt;&lt;/sub&gt;) and luminescence dissymmetry factor (g&lt;sub&gt;&lt;i&gt;lum&lt;/i&gt;&lt;/sub&gt;) of the CP-RTP materials are as high as 0.48 and 0.16, respectively, which are one or two orders of magnitude larger than previous records. These cellulose-based CP-RTP materials have full-color emission, and can be processed into different format. In particular, the CP-RTP materials exhibit chiral recognition performance in an instrument-free visual mode. They give a change of RTP performance once meeting different enantiomers, including lysine, histidine, cysteine, 2-chloromandelic acid, and 1-(2-naphthyl) ethanol. The novel strategy and new CP-RTP materials could promote the enrichment and practical applications of CPL materials.&lt;/p&gt;

New insight into π–π interactions: realization of full color emission from blue to red under hydrostatic pressure without exogenous intramolecular charge transfer

A new strategy to disclose the relationship between π–π stacking without exogenous ICT and photophysical properties was propounded through the construction of smart piezochromic materials with a discrete π–π dimer and high-pressure technique.