Color-Tunable Supramolecular Luminescent Materials

Transient cucurbit[7]uril-mediated host-guest complexes for time-dependent fluorescence and information-self-erasing hydrogel

A non-equilibrium cucurbit[7]uril-mediated supramolecular host-guest system is fabricated by using urea/urease to control aqueous solution pH on time dimension, showing transient assembly behavior and time-dependent fluorescence. The dynamic assembly can be also achieved in hydrogel network, resulting in a time-dependent fluorescent hydrogel for information encryption.

Pillar[5]arene-Based Ion-Pair Recognition for Encapsulation of a Stilbazolium-Type Dye with Enhanced Photophysical Properties and Nonlinear Optical Activity

Constructing organic composite materials through molecular recognition has emerged as an important theme in materials science. Here we report an ion-pair recognition system involving the use of a propoxylated pillar[5]arene (PrP5) to modulate the solid-state photophysical properties of dye trans-4'-(dimethylamino)-N-methyl-4-stilbazolium hexafluorophosphate (DMASP). Single crystal X-ray diffraction analysis reveals that the dye guest DMASP is encapsulated by PrP5 to form a 2 : 1 host-guest complex 2PrP5⸧DMASP in the crystalline state. The macrocyclic skeleton of PrP5 imposes restrictions on the intramolecular motions of the dye guest, leading to a significant enhancement of its fluorescence emission. Additionally, within the 2PrP5⸧DMASP complex crystal structure, DMASP molecules are found to display two possible opposite orientations in the one-dimensional channels formed by PrP5 molecules. This arrangement is believed to alter the overall solid-state packing structure of DMASP, thereby activating its nonlinear optical activity. This work not only reports a novel ion-pair molecular recognition system based on pillararenes but also provides valuable insights into the modulation of the crystalline state photophysical properties of organic dyes via cocrystal engineering.

Triple-Phosphorescent Gold Nanoclusters Enabled by Isomerization of Terminal Thiouracils in the Surface Motifs

Metal nanoclusters (NCs) hold great promise for expressing multipeak emission based on their well-defined total structure with diverse luminescent centers. Herein, we report the surface motif-dictated triple phosphorescence of Au NCs with dynamic color turning. The deprotonation-triggered isomerization of terminal thiouracils can evolve into a mutual transformation among their hierarchical motifs, thus serving a multipeak-emission expression with good tailoring. More importantly, the underlying electron transfer is thoroughly identified by excluding the radiative and nonradiative energy transfer, where electrons flow from the first phosphorescent state to the last two ones. The findings shed light on finely tailing motifs at the molecular level to motivate studies on customizable luminescence characteristics of metal NCs.

Photoacoustic Imaging-Guided Self-Adaptive Hyperthermia Supramolecular Cascade Nano-Reactor for Diabetic Periodontal Bone Regeneration

Commencing with the breakdown of the diabetic osteoimmune microenvironment, multiple pathogenic factors, including hyperglycemia, inflammation, hypoxia, and deleterious cytokines, are conjointly involved in the progression of diabetic periodontal bone regeneration. Based on the challenge of periodontal bone regeneration treatment and the absence of real-time feedback of blood oxygen fluctuation in diabetes mellitus, a novel self-adaptive hyperthermia supramolecular cascade nano-reactor ACFDG is constructed via one-step supramolecular self-assembly strategy to address multiple factors in diabetic periodontal bone regeneration. Hyperthermia supramolecular ACFDG possesses high photothermal conversion efficiency (32.1%), and it can effectively inhibit the vicious cycle of ROS-inflammatory cascade through catalytic cascade reactions, up-regulate the expression of heat shock proteins (HSPs) under near-infrared (NIR) irradiation, which promotes periodontal bone regeneration. Remarkably, ACFDG can provide real-time non-invasive diagnosis of blood oxygen changes during periodontal bone regeneration through photoacoustic (PA) imaging, thus can timely monitor periodontal hypoxia status. In conclusion, this multifunctional supramolecular nano-reactor combined with PA imaging for real-time efficacy monitoring provides important insights into the biological mechanisms of diabetic periodontal bone regeneration and potential clinical theranostics.

Comprehensive Study of Artificial Light-Harvesting Systems with a Multi-Step Sequential Energy Transfer Mechanism

Artificial light-harvesting systems (LHSs) with a multi-step sequential energy transfer mechanism significantly enhance light energy utilization. Nonetheless, most of these systems exhibit an overall energy transfer efficiency below 80%. Moreover, due to challenges in molecularly aligning multiple donor/acceptor chromophores, systems featuring ≥3-step sequential energy transfer are rarely reported. Here, a series of artificial LHSs is introduced featuring up to 4-step energy transfer mechanism, constructed using a cyclic peptide-based supramolecular scaffold. These LHSs showed remarkably high energy transfer efficiencies (≥90%) and satisfactory fluorescence quantum yields (ranging from 17.6% to 58.4%). Furthermore, the structural robustness of the supramolecular scaffold enables a comprehensive study of these systems, elucidating the associated energy transfer pathways, and identifying additional energy transfer processes beyond the targeted sequential energy transfer. Overall, this comprehensive investigation not only enhances the understanding of these LHSs, but also underscores the versatility of cyclic peptide-based supramolecular scaffolds in advancing energy harvesting technologies.

Surficial Host-Guest Responsive CsPbBr3 Perovskite Nanocrystals for Programmable Multi-Level Information Encryption

The design of smart stimuli-responsive photoluminescent materials capable of multi-level encryption and complex information storage is highly sought after in the current information era. Here, a novel adamantyl-capped CsPbBr3 (AD-CsPbBr3) perovskite NCs, along with its supramolecular host-guest assembly partner a modified β-CD (mCD), mCD@AD-CsPbBr3, are designed and prepared. By dispersing these two materials in different solvents, namely, AD-CsPbBr3 in toluene, mCD@AD-CsPbBr3 in toluene, and mCD@AD-CsPbBr3 in methanol, the three solutions exhibit diverse photoluminescence (PL) turn-on/off or PL discoloration response upon supramolecular stimulus. Based on these responses, a proof-of-principle programmable Multi-Level Photoluminescence Encoding System (MPLES) is established. Three types of four-level and three types of three-level information encoding are achieved by the system. A layer-by-layer four-level information encryption and decryption as well as a two-level encrypted 3D code are successfully achieved.

Tunable Nano-Bending Structures of Loosened/Tightened Lassos with Bi-Stable Vibration-Induced Emissions for Multi-Manipulations of White-Light Emissions and Sensor Applications

The first tunable nano-bending structures of [1]rotaxane containing a single-fluorophoric N,N'-diphenyl-dihydrodibenzo[a,c]phenazine (DPAC) moiety (i.e., [1]RA) are developed as a loosened lasso structure to feature the bright white-light emission [CIE (0.27, 0.33), Φ = 21.2%] in THF solution, where bi-stable states of bending and twisted structures of DPAC unit in [1]RA produce cyan and orange emissions at 480 and 600 nm, respectively. With acid/base controls, tunable loosened/tightened nano-loops of corresponding [1]rotaxanes (i.e., [1]RA/[1]RB) can be achieved via the shuttling of macrocycles reversibly, and thus to adjust their respective white-light/cyan emissions, where the cyan emission of [1]RB is obtained due to the largest conformational constraint of DPAC moiety in its bending form of [1]RB with a tightened lasso structure. Additionally, the non-interlocked analog M-Boc only shows the orange emission, revealing the twisted form of DPAC fluorophore in M-Boc without any conformational constraint. Moreover, the utilization of solvents (with different viscosities and polarities), temperatures, and water fractions could serve as effective tools to adjust the bi-stable vibration-induced emission (VIE) colors of [1]rotaxanes. Finally, tuning ratiometric emission colors of adaptive conformations of DPAC moieties by altering nano-bending structures in [1]rotaxanes and external stimuli can be further developed as intelligent temperature and viscosity sensor materials.

Strategies for Constructing Macrocyclic Arene-Based Color-Tunable Supramolecular Luminescent Materials

Over the past decades, supramolecular luminescent materials (SLMs) have attracted considerable attention due to their dynamic noncovalent interactions, versatile functions, and intriguing applications in many research fields. From construction to application, great efforts and progress have been made in color-tunable SLMs in recent years. In order to realize multicolor luminescence, various design strategies have been proposed. Macrocyclic chemistry, one of the brightest jewels in the field of supramolecular chemistry, has played a crucial role in the construction of stimuli-responsive and emission-tunable SLMs. Moreover, the flexible and tunable conformation and multiple noncovalent complexation sites of the macrocyclic arenes (MAs) afford a new opportunity to create such dynamic smart luminescent materials. Inspired by our reported work on the color-tunable supramolecular crystalline assemblies modulated by the conformation of naphth[4]arene, this Concept provides a summary of the latest developments in the construction of color-tunable MA-based SLMs, accompanied by the various construction strategies. The aim is to provide researchers with a new perspective to construct color-tunable SLMs with fascinating functions.

Finely manipulating room temperature phosphorescence by dynamic lanthanide coordination toward multi-level information security

Room temperature phosphorescence materials have garnered significant attention due to their unique optical properties and promising applications. However, it remains a great challenge to finely manipulate phosphorescent properties to achieve desirable phosphorescent performance on demand. Here, we show a feasible strategy to finely manipulate organic phosphorescent performance by introducing dynamic lanthanide coordination. The organic phosphors of terpyridine phenylboronic acids possessing excellent coordination ability are covalently embedded into a polyvinyl alcohol matrix, leading to ultralong organic room temperature phosphorescence with a lifetime of up to 0.629 s. Notably, such phosphorescent performance, including intensity and lifetime, can be well controlled by varying the lanthanide dopant. Relying on the excellent modulable performance of these lanthanide-manipulated phosphorescence films, multi-level information encryption including attacker-misleading and spatial-time-resolved applications is successfully demonstrated with greatly improved security level. This work opens an avenue for finely manipulating phosphorescent properties to meet versatile uses in optical applications.

Dynamic multicolor emissions of multimodal phosphors by Mn2+ trace doping in self-activated CaGa4O7

The manipulation of excitation modes and resultant emission colors in luminescent materials holds pivotal importance for encrypting information in anti-counterfeiting applications. Despite considerable achievements in multimodal and multicolor luminescent materials, existing options generally suffer from static monocolor emission under fixed external stimulation, rendering them vulnerability to replication. Achieving dynamic multimodal luminescence within a single material presents a promising yet challenging solution. Here, we report the development of a phosphor exhibiting dynamic multicolor photoluminescence (PL) and photo-thermo-mechanically responsive multimodal emissions through the incorporation of trace Mn2+ ions into a self-activated CaGa4O7 host. The resulting phosphor offers adjustable emission-color changing rates, controllable via re-excitation intervals and photoexcitation powers. Additionally, it demonstrates temperature-induced color reversal and anti-thermal-quenched emission, alongside reproducible elastic mechanoluminescence (ML) characterized by high mechanical durability. Theoretical calculations elucidate electron transfer pathways dominated by intrinsic interstitial defects and vacancies for dynamic multicolor emission. Mn2+ dopants serve a dual role in stabilizing nearby defects and introducing additional defect levels, enabling flexible multi-responsive luminescence. This developed phosphor facilitates evolutionary color/pattern displays in both temporal and spatial dimensions using readily available tools, offering significant promise for dynamic anticounterfeiting displays and multimode sensing applications.

Photodynamic O2 Economizer Encapsulated with DNAzyme for Enhancing Mitochondrial Gene-Photodynamic Therapy

Emerging research suggests that mitochondrial DNA is a potential target for cancer treatment. However, achieving precise delivery of deoxyribozymes (DNAzymes) and combining photodynamic therapy (PDT) and DNAzyme-based gene silencing together for enhancing mitochondrial gene-photodynamic synergistic therapy remains challenging. Accordingly, herein, intelligent supramolecular nanomicelles are constructed by encapsulating a DNAzyme into a photodynamic O2 economizer for mitochondrial NO gas-enhanced synergistic gene-photodynamic therapy. The designed nanomicelles demonstrate sensitive acid- and red-light sequence-activated behaviors. After entering the cancer cells and targeting the mitochondria, these micelles will disintegrate and release the DNAzyme and Mn (II) porphyrin in the tumor microenvironment. Mn (II) porphyrin acts as a DNAzyme cofactor to activate the DNAzyme for the cleavage reaction. Subsequently, the NO-carrying donor is decomposed under red light irradiation to generate NO that inhibits cellular respiration, facilitating the conversion of more O2 into singlet oxygen (1 O2 ) in the tumor cells, thereby significantly enhancing the efficacy of PDT. In vitro and in vivo experiments reveal that the proposed system can efficiently target mitochondria and exhibits considerable antitumor effects with negligible systemic toxicity. Thus, this study provides a useful conditional platform for the precise delivery of DNAzymes and a novel strategy for activatable NO gas-enhanced mitochondrial gene-photodynamic therapy.

Cucurbit[8]uril Confinement-Based Secondary Coassembly for High-Efficiency Phosphorescence Energy Transfer Behavior

Aqueous supramolecular long-lived near-infrared (NIR) material is highly attractive but still remains great challenge. Herein, we report cucurbit[8]uril confinement-based secondary coassembly for achieving NIR phosphorescence energy transfer in water, which is fabricated from dicationic dodecyl-chain-bridged 4-(4-bromophenyl)-pyridine derivative (G), cucurbit[8]uril (CB[8]), and polyelectrolyte poly(4-styrene-sulfonic sodium) (PSS) via the hierarchical confinement strategy. As compared to the dumbbell-shaped G, the formation of unprecedented linear polypseudorotaxane G⊂CB[8] with nanofiber morphology engenders an emerging phosphorescent emission at 510 nm due to the macrocyclic confinement effect. Moreover, benefiting from the following secondary assembly confinement, such tight polypseudorotaxane G⊂CB[8] can further assemble with anionic polyelectrolyte PSS to yield uniform spherical nanoparticle, thereby significantly strengthening phosphorescence performance with an extended lifetime (i.e., 2.39 ms, c.f., 45.0 μs). Subsequently, the organic dye Rhodamine 800 serving as energy acceptor can be slightly doped into the polyelectrolyte assembly, which enables the occurrence of efficient phosphorescence energy transfer process with efficiency up to 80.1% at a high donor/acceptor ratio, and concurrently endows the final system with red-shifted and long-lived NIR emission (710 nm). Ultimately, the as-prepared assembly is successfully exploited as versatile imaging agent for NIR window labeling and detecting in living cells.

Photo-Responsive Dynamic Organic Room-Temperature Phosphorescence Materials Based on a Functional Unit Combination Strategy

A rational molecular design strategy facilitates the development of a purely organic room-temperature phosphorescence (RTP) material system with precisely regulated luminescence properties, which surely promotes its functional integration and intelligent application. Here, a functional unit combination strategy is proposed to design novel RTP molecules combining a folding unit with diverse luminescent cores. The different luminescent cores are mainly responsible for tunable RTP properties, while the folding unit contributes to the spin-orbit coupling (SOC) enhancement, which makes the RTP material design as workable as the building block principle. By this strategy, a series of color/lifetime-tunable RTP materials is achieved with unique photo-responsive RTP enhancement when subjected to UV irradiation, which expands their application scenarios in reusable privacy tags, advanced "4D" encryption, and phase separation analysis of blended polymers. This work suggests a simple and effective strategy to design purely organic RTP materials with tunable color and lifetime, and also provides new application options for photo-responsive dynamic RTP materials.

Light-Driven Reversible Multicolor Supramolecular Shuttle

Light-driven multicolor supramolecular systems mainly rely on the doping of dyes or a photo-reaction to produce unidirectional luminescence. Herein, we use visible light to drive the bidirectional reversible multicolor supramolecular shuttle from blue to green, white, yellow, up to orange by simple encapsulation of spiropyran-modified cyanostilbene (BCNMC) by the macrocyclic cucurbit[8]uril (CB[8]) monomer. The resultant host-guest complex displayed enhanced fluorescence properties, i.e. the multicolor fluorescence shuttle changed from blue to orange in the dark within 2 hours and reverted to the original state upon visible light irradiation for 30 s. Benefiting from the sensitivity of the spiropyran moiety to light, it can spontaneously isomerize from the ring-opened state to a ring-closed isomer in aqueous solution, and this photo-isomerization reaction is a reversible process under visible light irradiation, leading to the multicolor luminescence supramolecular shuttle as a result of intramolecular energy transfer. In addition, the light also drove the reversible conversion of the topological morphology of the host-guest complex from two-dimensional nanoplatelets to nanospheres. Different from the widely reported molecular rotaxane "shuttle", the spiropyran supramolecular shuttle confined in the macrocyclic host CB[8] not only modulated a reversible topological morphology by light but also exhibited multicolor luminescence, which was successfully applied in programmed and rewritable information encryption.

A Versatile Assembly Approach toward Multifunctional Supramolecular Poly(Ionic Liquid) Nanoporous Membranes in Water

Hydrogen (H)-bonding-integration of multiple ingredients into supramolecular polyelectrolyte nanoporous membranes in water, thereby achieving tailor-made porous architectures, properties, and functionalities, remains one of the foremost challenges in materials chemistry due to the significantly opposing action of water molecules against H-bonding. Herein, a strategy is described that allows direct fusing of the functional attributes of small additives into water-involved hydrogen bonding assembled supramolecular poly(ionic liquid) (PIL) nanoporous membranes (SPILMs) under ambient conditions. It discloses that the pore size distributions and mechanical properties of SPILMs are rationally controlled by tuning the H-bonding interactions between small additives and homo-PIL. It demonstrates that, benefiting from the synergy of multiple noncovalent interactions, small dye additives/homo-PIL solutions can be utilized as versatile inks for yielding colorful light emitting films with robust underwater adhesion strength, excellent stretchability, and flexibility on diverse substrates, including both hydrophilic and hydrophobic surfaces. This system provides a general platform for integrating the functional attributes of a diverse variety of additives into SPILMs to create multifunctional and programmable materials in water.

A Smart Single-Fluorophore Polymer: Self-Assembly Shapechromic Multicolor Fluorescence and Erasable Ink

A novel smart fluorescent polymer polyethyleneimine-grafted pyrene (PGP) is developed by incorporating four stimuli-triggers at molecular level. The triggers are amphiphilicity, supramolecular host-guest sites, pyrene fluorescence indicator, and reversible chelation sites. PGP exhibits smart deformation and shape-dependent fluorescence in response to external stimuli. It can deform into three typical shapes with a characteristic fluorescence color, namely, spherical core-shell micelles of cyan-green fluorescence, standard rectangular nanosheets of yellow fluorescence, and irregular branches of deep-blue fluorescence. A quasi-reversible deformation between the first two shapes can be dynamically manipulated. Moreover, driven by reversible coordination and the resulting intramolecular photoinduced electron transfer, PGP can be used as an aqueous fluorescence ink with erasable and recoverable properties. The fluorescent patterns printed by PGP ink on paper can be rapidly erased and recovered by simple spraying a sequence of Cu2+ and ethylene diamine tetraacetic acid aqueous solutions. This erase/recover transformation can be repeated multiple times on the same paper. The multiple stimulus responsiveness of PGP makes it have potential applications in nanorobots, sensing, information encryption, and anticounterfeiting.

Emission color tuning and dual-mode luminescence thermometry design in Dy3+/Eu3+co-doped SrMoO4phosphors

The challenge of building a highly reliable contactless temperature probe with high sensitivity, good temperature-induced color discriminability, and economical synthesis has prompted the research community to work in the field of rare-earth-based luminescence thermometry. Moreover, the fast-growing market for optoelectronic devices has increased the demand for tunable color-emitting phosphors. In this study, Dy3+/Eu3+co-doped SrMoO4phosphors were developed as tunable color-emitting source and dual-mode luminescence thermometer. A facile and cost-effective auto-combustion method was used to synthesize the phosphors. Our work demonstrates a viable scheme for tailoring the emission of single-phase phosphors by precisely controlling the dopant concentrations and by modulating excitation wavelength. The overall emission is tuned from greenish-yellow to white and greenish-yellow to reddish-orange. A detailed energy transfer process from the host to the Ln3+ions and between the Ln3+ions is discussed. Further, anti-thermal quenching in the emission of Dy3+ion is observed when excited with 297 nm. The dual-mode luminescence thermometry has been studied by analyzing the fluorescence intensity ratio of Dy3+and Eu3+ions upon excitation at 297 nm. The maximum relative sensitivity value for 4% Eu3+co-doped SrMoO4:4%Dy3+phosphor is 1.46% K-1at 300 K. Furthermore, the configurational coordinate diagram is presented to elucidate the nature of temperature-dependent emission. Therefore, our research opens up new avenues for the development of color-tunable luminescent materials for various optoelectronic and temperature-sensing applications.

Color-tunable emissions realized by Tb3+ to Eu3+ energy transfer in ZnGdB5O10 under near-UV excitation

Photoluminescent (PL) energy transfer (ET) between two typical rare earth activators Tb3+ and Eu3+ is utilized to achieve color-tunable emission and the color range is apparently dependent on the ET efficiency. In the target host ZnGdB5O10 (ZGBO), the relatively low symmetric coordination environment of the rare earth cation not only suppresses the parity-forbidden law of the 4f-4f transitions of Tb3+ in the near-UV region, but also enhances the internal quantum efficiency (IQE), where the optimal IQE is 65.61% for ZGBO:0.8Tb3+. Moreover, its ET to Eu3+ is highly efficient, i.e. 94.71% in ZGBO:0.8Tb3+,0.10Eu3+, which eventually leads to a wide range of color-tunable emissions from green (0.2915, 0.5915) to red (0.6207, 0.3731). The systematic PL spectral study on Tb3+/Eu3+ singly doped and co-doped phosphors suggests that the ET mechanism takes place through the electric dipole-dipole interaction according to the Inokuti-Hirayama (I-H) model. Additionally, the in situ high temperature PL spectra indicate the very high thermal stability of ZnGd0.19Tb0.8Eu0.01B5O10, indicating that it can be a potential candidate for near-UV light emitting diode-pumped phosphors.

Synthesis of Naphthalimide Derivatives and Their Luminescence upon Complexation with Cucurbit[n]uril Hosts

A series of naphthalimide derivatives are synthesized and their binding behavior upon complexation with cucurbit[n]urils (CB[n]s) has been investigated. With a heavy atom (bromine) on the naphthalimide core, 4-bromo-1,8-naphthalimide derivatives 1-4 show short room-temperature phosphorescence (RTP) lifetimes with low quantum yields. Their RTP properties are significantly enhanced in the presence of CB[8] or CB[10] both in aqueous solution and solid state owing to the efficient suppression of nonradiative decay and isolation of quenching factors by the rigid cavity of CB[n]. Without the bromine atom, 1,8-naphthalimide derivatives 5 and 6 show strong excimer emission upon complexation with CB[10] accompanied by fluorescence transition from blue to cyan. The fluorescence colors of 4-(dimethylamino)-1,8-naphthalimide derivatives 7 and 8 change from blue to white to yellow with the addition of CB[n]. This host-guest complexation strategy to modulate the luminescence of the luminophore would further broaden the application of luminescent materials.

High-Temperature, Reversible, and Robust Thermochromic Fluorescence Based on Rb2 MnBr4 (H2 O)2 for Anti-Counterfeiting

Thermochromic fluorescent materials (TFMs) characterized by noticeable emission color variation with temperature have attracted pervasive attention for their frontier application in stimulus-response and optical encryption technologies. However, existing TFMs typically suffer from weak PL reversibility as well as limited mild operating temperature and severe temperature PL quenching. PL switching under extreme conditions such as high temperature will undoubtedly improve encryption security, while it is still challenging for present TFMs. In this work, high-temperature thermochromic fluorescence up to 473 K and robust structural and optical reversibility of 80 cycles are observed in Rb2 MnBr4 (H2 O)2 and related crystals, which is seldom reported for PL changes at such a high temperature. Temperature-driven nonluminous, red and green light emission states can be achieved at specific temperatures and the modulation mechanism is verified by in situ optical and structural measurements and single particle transition. By virtue of this unique feature, a multicolor anti-counterfeiting label based on a broad temperature gradient and multidimensional information encryption applications are demonstrated. This work opens a window for the design of inorganic materials with multi-PL change and the development of advanced encryption strategies with extreme stimuli source.

Crystalline Nanoparticles of Water-Soluble Covalent Basket Cages (CBCs) for Encapsulation of Anticancer Drugs

We herein describe the preparation, assembly, recognition characteristics, and biocompatibility of novel covalent basket cage CBC-11, composed of four molecular baskets linked to four trivalent aromatic amines through amide groups. The cage is tetrahedral in shape and similar in size to small proteins (Mw =8637 g/mol) with a spacious nonpolar interior for accommodating multiple guests. While 24 carboxylates at the outer surface of CBC-11 render it soluble in aqueous phosphate buffer (PBS) at pH=7.0, the amphiphilic nature prompts its assembly into nanoparticles (d=250 nm, DLS). Cryo-TEM examination of nanoparticles revealed their crystalline nature with wafer-like shapes and hexagonally arranged cages. Nanoparticulate CBC-11 traps anticancer drugs irinotecan and doxorubicin, with each cage binding up to four drug molecules in a non-cooperative manner. The inclusion complexation resulted in nanoparticles growing in size and precipitating. In media containing mammalian cells (HCT 116, human colon carcinoma), the IC50 value of CBC-11 was above 100 μM. While this work presents the first example of a large covalent organic cage operating in water at the physiological pH and forming crystalline nanoparticles, it also demonstrates its biocompatibility and potential to act as a polyvalent binder of drugs for their sequestration or delivery.

Turning enol* emission of SBOH via restricting twisted intramolecular charge transfer behavior by pressure

Stimuli-responsive luminogens with aggregation-induced emission and excited state intramolecular proton transfer (ESIPT) properties have applications in storage devices, anti-counterfeiting, imaging, and sensors. Nevertheless, group rotation appears in twisted intramolecular charge transfer (TICT) state, resulting in decreased fluorescence intensity. Inhibiting TICT remains a challenge based on their intrinsic molecular configuration. Herein, we present a simple facile pressure-induced method to restrict the TICT behavior. Steady-state spectroscopy measurement shows that fluorescence enhancement and color shifts can be achieved under high pressure. Combined with in situ high-pressure ultrafast spectroscopy and theoretical calculations, the TICT behavior was restricted in two aspects. The ESIPT process was damaged, hence more particles stored in the E* state, and transferred to the TICT state hardly. Also, the rotation of (E)-dimethyl5-((4-(diethylamino)-2-hydroxybenzylidene)amino)isophthalate (SBOH) was restricted, significantly increasing the fluorescence intensity. This approach provides a new strategy for the development of stimulus-responsive materials.

Thermochromic Ni(II) Organometallics With High Optical Transparency and Low Phase-Transition Temperature for Energy-Saving Smart Windows

Thermochromic smart windows with rational modulation in indoor temperature and brightness draw considerable interest in reducing building energy consumption, which remains a huge challenge to meet the comfortable responsive temperature and the wide transmittance modulation range from visible to near-infrared (NIR) light for their practical application. Herein, a novel thermochromic Ni(II) organometallic of [(C₂ H₅ )₂ NH₂ ]₂ NiCl₄ for smart windows is rationally designed and synthesized via an inexpensive mechanochemistry method, which processes a low phase-transition temperature of 46.3 °C for the reversible color evolution from transparent to blue with a tunable visible transmittance from 90.5% to 72.1%. Furthermore, cesium tungsten bronze (CWO) and antimony tin oxide (ATO) with excellent NIR absorption in 750-1500 and 1500-2600 nm are introduced in the [(C₂ H₅ )₂ NH₂ ]₂ NiCl₄ -based smart windows, realizing a broadband sunlight modulation of a 27% visible light modulation and more than 90% of NIR shielding ability. Impressively, these smart windows demonstrate stable and reversible thermochromic cycles at room temperature. Compared with the conventional windows in the field tests, these smart windows can significantly reduce the indoor temperature by 16.1 °C, which is promising for next-generation energy-saving buildings.

The Green Box: Selenoviologen-Based Tetracationic Cyclophane for Electrochromism, Host-Guest Interactions, and Visible-Light Photocatalysis

The novel selenoviologen-based tetracationic cyclophanes (green boxes 3 and 5) with rigid electron-deficient cavities are synthesized via S_N2 reactions in two steps. The green boxes exhibit good redox properties, narrow energy gaps, and strong absorption in the visible range (370-470 nm), especially for the green box 5 containing two selenoviologen (SeV²⁺) units. Meanwhile, the femtosecond transient absorption (fs-TA) reveals that the green boxes have a stabilized dicationic biradical, high efficiency of intramolecular charge transfer (ICT), and long-lived charge separation state due to the formation of cyclophane structure. Based on the excellent photophysical and redox properties, the green boxes are applied to electrochromic devices (ECDs) and visible-light-driven hydrogen production with a high H₂ generation rate (34 μmol/h), turnover number (203), and apparent quantum yield (5.33 × 10^-2). In addition, the host-guest recognitions are demonstrated between the green boxes and electron-rich guests (e.g., G1:1-naphthol and G2:platinum(II)-tethered naphthalene) in MeCN through C-H···π and π···π interactions. As a one-component system, the host-guest complexes of green box⊃G2 are successfully applied to visible-light photocatalytic hydrogen production due to the intramolecular electron transfer (IET) between platinum(II) of G2 and SeV²⁺ of the green box, which provides a simplified system for solar energy conversion.

Highly Tough, Stretchable, and Recyclable Ionogels with Crosslink-Enhanced Emission Characteristics for Anti-Counterfeiting and Motion Detection

Traditional luminescent ionogels often suffer from poor mechanical properties and a lack of recyclability and regeneration, which limits their further application and sustainable development. Herein, a luminescent ionogel with strong mechanical properties and good recyclability has been designed and fabricated by introducing dynamic coordination bonds via in situ one-step crosslinking of acrylic acid in ionic liquid of 1-ethyl-3-methylimidazolium diethylphosphate by zinc dimethacrylate. Due to the special crosslinking of dynamic coordination bonds along with the hydrogen bond interaction, the as-prepared ionogel displays excellent stretchability and toughness, good self-adhesiveness, fast self-healability, and recyclability. Interestingly, the obtained ionogels exhibit tunable photoluminescence caused by the crosslink-enhanced emission (CEE) effect from the coordination bonds. Importantly, ionogels can be applied in information storage, information encryption, anti-counterfeiting due to their simple and in situ preparation method, and their special fluorescence performances. Moreover, an ionogel-based wearable sensor has rapid response time and a high gauge factor of 3.22 within a wide strain range from 1 to 700%, which can monitor various human movements accurately from subtle to large-scale motions. This paper offers a promising way to fabricate sustainable functional ionic liquid-based composites with CEE characteristics via an in situ one-step polymerization method.

Enzyme Grafting with a Cofactor-Decorated Metal-Organic Capsule for Solar-to-Chemical Conversion

Semi-artificial approaches to solar-to-chemical conversion can achieve chemical transformations that are beyond the capability of natural enzymes, but face marked challenges to facilitate in vivo cascades, due to their inevitable need for cofactor shuttling and regeneration. Here, we report on an enzyme grafting strategy to build a metal-organic capsule-docking artificial enzyme (metal-organic-enzyme, MOE) that comprised the self-assembly of a cofactor-decorated capsule and the supramolecular enzyme-recognition features between the enzyme scaffold and the capsule to bypass cofactor shuttling and regeneration. The incorporated NADH mimics within the metal-organic capsule interacted with the imine intermediate that formed from the condensation of the amines and the dehydrogenation of alcohol substrates in the microenvironment to form complexes within the capsule and subsequently served as an in situ-generated photoresponsive cofactor. Upon illumination, the photoresponsive cofactor facilitates efficient proton/electron transport between the inner space (supramolecular hydrogenation) and outer space (enzymatic dehydrogenation) of the capsule to dehydrogenize the alcohols and hydrogenize the imine intermediates, respectively, circumventing the conventionally complex multistep cofactor shuttling and regeneration. The semi-artificial enzyme endows the conversion of diverse types of alcohol to amine products in both aqueous/organic solutions and Escherichia coli with high efficiency, offering a wide range of opportunities for sustainable and environmentally friendly biomanufacturing of commodity and fine chemicals.

Fluorophore-based host-guest assembly complexes for imaging and therapy

Recently, supramolecular chemistry with its unique properties has received considerable attention in many fields. Supramolecular fluorescent systems constructed on the basis of macrocyclic hosts are not only effective in overcoming the limitations of imaging and diagnostic reagents, but also in enhancing their performances. This paper summarizes the recent advances in supramolecular fluorescent systems based on host-guest interactions and their application in bioimaging and therapy as well as the challenges and prospects in developing novel supramolecular fluorescent systems.

Dual and Sequential Locked/Unlocked Photochromic Effects on FRET Controlled Singlet Oxygen Processes by Contracted/Extended Forms of Diarylethene-Based [1]Rotaxane Nanoparticles

Manipulations of singlet oxygen (¹ O₂ ) generations by the integration of both aggregation-induced emission luminogen (AIEgen) photosensitizer and photochromic moieties have diversified features in photodynamic therapy applications. Through Förster resonance energy transfer (FRET) pathway to induce red PL emissions (at 595 nm) for ¹ O₂ productions, [1]rotaxane containing photosensitive tetraphenylethylene (TPE) donor and photochromic diarylethene (DAE) acceptor is introduced to achieve dual and sequential locked/unlocked photoswitching effects by pH-controlled shuttling of its contracted/extended forms. Interestingly, the UV-enabled DAE ring closure speeds follow the reversed trend of DAE self-constraint degree as: contracted < extended < noninterlocked forms in [1]rotaxane analogues, thus FRET processes can be adjusted in contracted/extended forms of [1]rotaxane upon UV irradiations. Accordingly, the contracted form of [1]rotaxane is FRET-OFF locked and inert to UV exposure due to the larger bending conformation of DAE parallel (p-)conformer, compared with its extended and noninterlocked analogues possessing switchable FRET-OFF/ON behaviors activated by dual and sequential pH- and photoswitching. Owing to the advantages of ¹ O₂ productions tuned by multistimuli inputs (pH, UV, and blue light), an useful logic circuit for toxicity outputs of the surface modified [1]rotaxane nanoparticles (NPs) has been demonstrated to offer promising ¹ O₂ productions and managements based on mechanically interlocked molecules for future bioapplications.

Photoresponsive Supramolecular Polymers: From Light-Controlled Small Molecules to Smart Materials

Photoresponsive supramolecular polymers are well-organized assemblies based on highly oriented and reversible noncovalent interactions containing photosensitive molecules as (co-)monomers. They have attracted increasing interest in smart materials and dynamic systems with precisely controllable functions, such as light-driven soft actuators, photoresponsive fluorescent anticounterfeiting and light-triggered electronic devices. The present review discusses light-activated molecules used in photoresponsive supramolecular polymers with their main photo-induced changes, e.g., geometry, dipole moment, and chirality. Based on these distinct changes, supramolecular polymers formed by light-activated molecules exhibit photoresponsive disassembly and reassembly. As a consequence, photo-induced supramolecular polymerization, "depolymerization," and regulation of the lengths and topologies are observed. Moreover, the light-controlled functions of supramolecular polymers, such as actuation, emission, and chirality transfer along length scales, are highlighted. Furthermore, a perspective on challenges and future opportunities is presented. Besides the challenge of moving from harmful UV light to visible/near IR light avoiding fatigue, and enabling biomedical applications, future opportunities include light-controlled supramolecular actuators with helical motion, light-modulated information transmission, optically recyclable materials, and multi-stimuli-responsive supramolecular systems.

Fluorescent Nanoassemblies in Water Exhibiting Tunable LCST Behavior and Responsive Light Harvesting Ability

Responsive fluorescent nanomaterials have been received considerable attention in recent years. In this work, a bola-type amphiphilic molecule, CSO, was synthesized which contains a hydrophobic cyanostilbene core and hydrophilic oligo(ethylene glycol) (OEG) coils at both sides. The cyanostilbene group is aggregation-induced emission (AIE) active, while the OEG coils are thermo-responsive. As a result, the CSO molecules can self-assemble into blue-fluorescent nanoassemblies with lower critical solution temperature (LCST) behavior in aqueous media. It is noteworthy that the LCST behavior can be reversibly regulated with changes in concentration and the introduction of K⁺ . Intriguingly, fluorescence of CSO assembly shows a blue-shift upon heating. Finally, by employing CSO as a light capturing antenna and energy donor, an artificial light harvesting system with tunable emission and thermo-responsive characteristics was fabricated. This study not only demonstrates an integrated approach to create responsive fluorescent nanomaterials, but also shows great potential for producing luminescent materials and mimicking photosynthesis in nature.

Color-Tunable Upconversion-Emission Switch Based on Cocrystal-to-Cocrystal Transformation

Cocrystal engineering, involving the assembly of two or more components into a highly ordered solid-state superstructure, has emerged as a popular strategy for tuning the photophysical properties of crystalline materials. The reversible co-assembly and disassembly of multicomponent cocrystals and their reciprocal transformation in the solid state remain challenging objectives. Herein, we report a color-tunable upconversion-emission switch based on the interconversion between two cocrystals. One red- and one yellow-emissive cocrystal, composed of an electron-deficient naphthalenediimide-based triangular macrocycle and different electron donors, have been obtained. The red- and yellow-emissive cocrystals undergo reversible transformations on exchanging the electron donors. Benefiting from intermolecular charge transfer interactions, the two cocrystals display superior two-photon excited upconversion emission. Accompanying the interconversion of the two cocrystals, their luminescent color changes between red and yellow, forming a dual-color upconversion-emission switch. This research provides a rare yet critical example involving precise control of cocrystal-to-cocrystal transformation and affords a reference for fabricating color-tunable nonlinear optical materials in the solid state.

Characteristic stacked structures and luminescent properties of dinuclear lanthanide complexes with pyrene units

A novel design strategy of stacked organic fluorophores using dinuclear lanthanide (Ln(III)) complexes is demonstrated for the formation of excimer. The dinuclear Ln(III) complexes are composed of two Ln(III) (Eu(III) or Gd(III)) ions, six hexafluoroacetylacetonate (hfa), and two pyrene-based phosphine oxide ligands. Single-crystal analysis revealed a rigid pyrene-stacked structure via CH-F (pyrene/hfa) intramolecular interactions. The rigid aggregation structures of the two-typed organic ligands around Ln(III) resulted in high thermal stability (decomposition temperature: 340°C). The aggregated ligands exhibited excimer-type green emission from the stacked pyrene-center. The change in the Ln(III) ion promotes effective shifts of excimer emissions (Gd(III):500 nm, Eu(III):490 nm). The organic aggregation system using red-luminescent Eu(III) also provides temperature-sensitive ratiometric emission composed of π-π* and 4f-4f transitions by energy migration between aggregated ligands and Eu(III).

Dynamic Timing Control of Molecular Photoluminescent Systems

Dynamic control of molecular photoluminescence offers chemical solutions to designing functional emissive materials. Although stimuli-switchable molecular luminescent systems are well established, how to encode these dynamic emissive systems with a "timing" feature, that is, time-dependent luminescent properties, remains challenging. This Concept aims to summarize the design principles of dynamic timing molecular photoluminescent systems by discussing the state-of-the-art of this topic and the shaping of fabrication strategies at both the molecular and supramolecular levels. An outlook and perspectives are given to outline the future opportunities and challenges in the rational design and potential applications of these smart emissive systems.

Color-Tunable Binary Copolymers Manipulated by Intramolecular Aggregation and Hydrogen Bonding

Construction of color-tunable luminescent polymeric materials with enhanced emission intensity and room-temperature phosphorescence (RTP) performance regulated by a single chromophore component is highly desirable in the scope of photoluminescent materials. Herein, a set of binary copolymers were facilely synthesized using free radical polymerization by selecting different types of polymer matrix and N-substituted naphthalimides (NPA) as chromophores. Surprisingly, the fluorescence emission of copolymers could be remarkably enhanced, because of the intramolecular aggregation of NPA manipulated by a single polymer chain in both solution and solid state. Moreover, RTP signals of binary copolymers were all clearly observed in the air without any processing procedure, because of the embedding of phosphors into hydrogen bonding networks after copolymerization with vinyl-based acrylamide monomers. Taking advantages of the synergistic effect of copolymerization-induced aggregation and copolymerization-induced rigidification to promote optical performance, UV stimulus-responsive luminescent polymer films with processability, flexibility, and adjustable emission wavelength were simply prepared using a drop-casting method in large scale, the setting of which is the basis for application in the fields of organic optoelectronics, information security, and bioimaging/sensing.

Development of Yellow-to-Orange Photoluminescence Molecules Based on Alterations in the Donor Units of Fluorinated Tolanes

Since the aggregation-induced emission (AIE) phenomenon was first reported by Tang et al., much effort has been devoted to the development of solid-state luminescent molecules by chemists worldwide. Our group successfully developed fluorinated tolanes as novel compact π-conjugated luminophores with blue photoluminescence (PL) in the crystalline state. Moreover, we reported the yellow-green PL molecules based on their electron-density distributions. In the present study, we designed and synthesized fluorinated tolanes with various amine-based donors and evaluated their photophysical properties. The carbazole-substituted fluorinated tolane exhibited strong PL in the solution state, whereas piperidine- or phenothiazine-substituted fluorinated tolanes showed a dramatic decrease in PL efficiency. Notably, fluorinated tolanes with piperidine or phenothiazine substituents displayed yellow-to-orange PL in the crystalline state; this may have occurred because these tolanes exhibited tightly packed structures formed by intermolecular interactions, such as H···F hydrogen bonds, which suppressed the non-radiative deactivation process. Moreover, fluorinated tolanes with amine-based donors exhibited AIE characteristics. We believe that these yellow-to-orange solid PL molecules can contribute to the development of new solid luminescent materials.

Morpholine-Functionalized Multicomponent Metallacage as a Vector for Lysosome-Targeted Cell Imaging

Metallacages with suitable cavities and specific functions are promising delivery vectors in biological systems. Herein, we report a morpholine-functionalized metallacage for lysosome-targeted cell imaging. The efficient host-guest interactions between the metallacage and dyes prevent them from aggregation, so their emission in aqueous solutions is well maintained. The fluorescence quantum yield of these host-guest complexes reaches 74.40%. Therefore, the metallacage is further employed as a vector to deliver dyes with different emission colors (blue, green, and red) into lysosomes for targeted imaging. This research affords a type of vector for the delivery of various cargos toward biological applications, which will enrich the usage of metallacages in biomedical engineering.

A dynamic assembly-induced emissive system for advanced information encryption with time-dependent security

The development of advanced materials for information encryption with time-dependent features is essential to meet the increasing demand on encryption security. Herein, smart materials with orthogonal and temporal encryption properties are successfully developed based on a dynamic assembly-induced multicolour supramolecular system. Multicolour fluorescence, including blue, orange and even white light emissions, is achieved by controlling the supramolecular assembly of pyrene derivatives by tailoring the solvent composition. By taking advantage of the tuneable fluorescence, dynamically controlled information encryption materials with orthogonal encryption functions, e.g., 3D codes, are successfully developed. Moreover, time-dependent information encryption materials, such as temporal multi-information displays and 4D codes, are also developed by enabling the fluorescence-controllable supramolecular system in the solid phase, showing multiple pieces of information on a time scale, and the correct information can be identified only at a specified time. This work provides an inspiring point for the design of information encryption materials with higher security requirements.

Self-assembled Fluorescent Nanoparticles with Tunable LCST Behavior in Water

The development of stimuli-responsive fluorescent materials in water based on organic molecule has drawn significant interest. Herein, we designed and synthesized an amphiphilic molecule M containing a fixed tetraphenylethylene moiety (FTPE) as hydrophobic part and tri(ethylene glycol) (TEG) chains as hydrophilic part. Notably, the FTPE moiety is aggregation-induced emission (AIE) active, while the TEG chains are thermo-responsive. M can self-assemble into fluorescent nanoparticles (NPs) in water, which showed lower critical solution temperature (LCST) behavior. Moreover, its clouding point can be reversibly tuned upon the concentration variation. Interestingly, the NPs can be acted as a fluorescence thermometer in aqueous media owing to their unique AIE and LCST behaviors. Our work herein not only provides an integration strategy to construct stimuli-responsive fluorescent materials but also shows great potential in biological applications including bioimaging and biosensors.

A Calix[3]acridan-Based Host-Guest Cocrystal Exhibiting Efficient Thermally Activated Delayed Fluorescence

A supramolecular strategy to construct thermally activated delayed fluorescence (TADF) materials through host-guest charge transfer interactions was proposed. Consequently, a new class of macrocycle namely calix[3]acridan was conveniently synthesized in 90 % yield. The host-guest cocrystal formed by calix[3]acridan and 1,2-dicyanobenzene exhibited efficient TADF properties due to intense intermolecular charge transfer interactions. Moreover, the spatially separated highest occupied molecular orbital and lowest unoccupied molecular orbital resulted in a very small singlet-triplet energy gap of 0.014 eV and hence guaranteed an efficient reverse intersystem crossing for TADF. Especially, a high photoluminescence quantum yield of 70 % was achieved, and it represents the highest value among the reported intermolecular donor-acceptor TADF materials.

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.

Dynamic Timing Control over Multicolor Molecular Emission by Temporal Chemical Locking

Dynamic control over molecular emission, especially in a time-dependent manner, holds great promise for the development of smart luminescent materials. Here we report a series of dynamic multicolor fluorescent systems based on the time-encoded locking and unlocking of individual vibrational emissive units. The intramolecular cyclization reaction driven by adding chemical fuel acts as a chemical lock to decrease the conformational freedom of the emissive units, thus varying the fluorescence wavelength, while the resulting chemically locked state can be automatically unlocked by the hydrolysis reaction with water molecules. The dynamic molecular system can be driven by adding chemical fuels for multiple times. The emission wavelength and lifetime of the locking states can be readily controlled by elaborating the molecular structures, indicating this strategy as a robust and versatile way to modulate multi-color molecular emission in a time-encoded manner.

Recent Advances in Mechanochromism of Metal-Organic Compounds

Smart luminescent materials, which can respond to the changing of external environment (light, electricity, force, temperature, etc.), have always been one of the research hotspots. Mechanochromism refers to the materials whose emission color or intensity can be altered under the stimulation of external mechanical force. This kind of smart materials have been widely used in data storage, information encryption and sensors due to its simple operation, obvious and rapid response. The introduction of metal atoms in metal-organic compounds brings about fascinating metalophilic interactions and results in more interesting and surprising mechanochromic behaviors. In this mini-review, recent advances in mechanochromism of metal-organic compounds, including mono-, di-, multinuclear metal-organic complexes and metallic clusters are summarized. Varies mechanisms are discussed and some design strategies for metal-organic compounds with mechanochromism are also presented.

Systematic arrangement control of functional organic molecules

Systematic and precise arrangement control of functional organic molecules without changing both their molecular and layered structure was established.

A novel thermally activated delayed fluorescence macrocycle

A novel luminescent macrocycle was conveniently synthesized, which exhibited flexible conformations and excellent thermally activated delayed fluorescence properties.