PolyMOF Nanoparticles: Dual Roles of a Multivalent polyMOF Ligand in Size Control and Surface Functionalization

Metal–organic framework nanoparticles (MOF NPs) have emerged as an important class of materials that display significantly enhanced performance in many applications compared to bulk MOF materials; their synthesis, however, commonly involves a tedious sequence that controls particle size and surface properties in separate steps. Now, a simple strategy to access functional MOF NPs in one pot is reported that uses a polyMOF ligand possessing a polymer block for surface functionalization and a coordination block with tunable multivalency for size control. This strategy produces uniform polyMOF‐5 NPs with sizes down to 20 nm, displaying exceptional structural and colloidal stability upon exposure to ambient conditions. A detailed time‐dependent study revealed that the polyMOF NPs were formed following an aggregation‐confined crystallization mechanism. Generality was demonstrated through the synthesis of well‐defined polyUiO‐66 NPs.     

Fmoc-protected amino acids as luminescent and circularly polarized luminescence materials based on charge transfer interaction

Fluorenylmethyloxycarbonyl (Fmoc)-protected amino acids are effective building blocks in self-assembled architectures at hierarchical levels, which however show limited luminescent properties and chiroptical activities. Here we introduce a charge-transfer strategy to build two-component luminescent materials with emerged circularly polarized luminescence properties. A library of Fmoc-amino acids was built, which selectively form charge-transfer complexes with the electron-deficient acceptor. Embedding in amorphous polymer matrix or physical grinding could trigger the charge-transfer luminescence with adjusted wavelengths in a general manner. X-ray diffraction results suggest the multiple binding modes between donor and acceptor. And, the solution-processed coassembly could selectively exhibit circularly polarized luminescence with high dissymmetry g-factors. This work illustrates a noncovalent charge-transfer strategy to construct luminescent and chiroptical organic composites based on the easy-accessible and economic chiral N-terminal aromatic amino acids.     

New Wine in Old Bottles: Prolonging Room‐Temperature Phosphorescence of Crown Ethers by Supramolecular Interactions

Supramolecular macrocyclic hosts have long been used in smart materials. However, their triplet emission and regulation at crystal level is rarely studied. Herein, ultralong and universal room‐temperature phosphorescence (RTP) is reported for traditional crown ethers. A supramolecular strategy involving chain length adjustment and morphological locking through complexation with K⁺ was explored as a general method to tune the phosphorescence lifetime in the solid state. A maximum 10‐fold increase of lifetime after complex formation accompanied with by invisible to visible phosphorescence was achieved. A deep encryption based on this activated RTP strategy was also facilely fabricated. This work thus opens a new world for supramolecular macrocycles and their intrinsic guest responsiveness offers a new avenue for versatile smart luminescent materials.     

Effect of OH- on the luminescent efficiency and lifetime of Tb3+-doped yttrium orthophosphate synthesized by solution precipitation

In this work, we use the solution precipitation method to synthesize Tb3+-doped yttrium orthophosphate, which is a green-emission luminescent material. The evolution of hydrated yttrium orthophosphate (YPO4.2H2O) to dehydrated yttrium orthophosphate (YPO4) is observed in the heat-treatment process, simultaneously, accompanying the structural transformation from monoclinic churchite-type to tetragonal xenotime-type structure. Furthermore, the luminescent efficiency of Tb3+-doped YPO4 presents a sharp jump at a critical temperature in this heat-treatment process. Interestingly, this critical temperature is close to the structural transformation temperature. The remarkable change of luminescent efficiency seems to be related to the structural transformation. However, the FTIR and fluorescent decay measurements at 10 and 300 K indicate that the OH group is the origin of luminescent efficiency change. OH- ions with high vibration frequency provide an efficient means to quench the luminescence. The comparison of the luminescent efficiency, OH- content, and lifetime of 5D4 of Tb3+ between two samples with the same crystal structure proves that the structural transformation has no significant effect on the luminescent efficiency and lifetime. On the basis of these results, it is proposed that correctly preventing OH- ions inside the host matrix or effectively eliminating them may improve the luminescent efficiency greatly. This idea also may be applied to other optical systems.     

Real‐Time Detection of Traces of Benzaldehyde in Benzyl Alcohol as a Solvent by a Flexible Lanthanide Microporous Metal–Organic Framework

Luminescent 3D lanthanide metal–organic framework (Ln‐MOF) {[Tb₂(TATAB)₂] ? 4 H₂O ? 6 DMF}_n ( 1 ) was synthesized under solvothermal conditions by using flexible ligand 4,4′,4′′‐s‐triazine‐1,3,5‐triyltri‐p‐aminobenzoate (TATAB). A phase transition was observed between low temperature and room temperature. The luminescence of 1 could be enhanced by formaldehyde and quenched efficiently by trace amounts of benzaldehyde in solvents such as benzyl alcohol (0.01–2.0 vol %) and ethanol (0.01–2.5 vol %). This is the first use of a Ln‐MOF as chemical sensor for both formaldehyde and benzaldehyde. The high sensitivity and selectivity of the luminescence response of 1 to benzaldehyde allows it to be used as an excellent sensor for identifying benzaldehyde and provides a simple and convenient method for detecting traces of benzaldehyde in benzyl alcohol based injections. This work establishes a new strategy for detection of benzaldehyde in benzyl alcohol by luminescent MOFs.     

New Strategy for Optimizing the Properties of Copper Halide Organic-Inorganic Hybrid Lighting-emitting Materials

Copper(I) halide organic-inorganic hybrid luminescent materials have many advantages, such as diverse structure, facile synthesis, high luminescent efficiency, tunable optical performance, etc., and show a broad application prospect in energy-saving lighting, display and other fields. However, compared with commercial rare-earth-metal-based phosphors, the reported hybrids generally suffer from poor stability and low luminescent efficiency, which are the bottleneck problem of their practical application. With the aim of developing high-performance organic-inorganic hybrid luminescent materials, a new synthesis strategy has been reported. This strategy can systematically design and synthesis copper(I) halide ionic hybrid structures by combining the covalent bonding and ionic bonding between inorganic and organic components into one structure, and use their synergistic effect to optimizing their properties. This design method is expected to develop high-performance organic-inorganic hybrid luminescent materials, promote the in-depth understanding of this field, and provide new ideas for the optimization of other types of hybrid materials.     

Highly luminescent CdTe/CdSe colloidal heteronanocrystals with temperature-dependent emission color

In this work we present the preparation of highly luminescent anisotropic CdTe/CdSe colloidal heteronanocrystals. The reaction conditions used (low temperature, slow precursor addition, and surfactant composition) resulted in a tunable shape from prolate to branched CdTe/CdSe nanocrystals. Upon CdSe shell growth the heteronanocrystals show a gradual evolution from type-I to type-II optical behavior. These heteronanocrystals show a remarkably high photoluminescence quantum yield (up to 82%) and negligible thermally induced quenching up to temperatures as high as 373 K.     

Amorphous Ionic Polymers with Color‐Tunable Ultralong Organic Phosphorescence

Amorphous purely organic phosphorescence materials with long‐lived and color‐tunable emission are rare. Herein, we report a concise chemical ionization strategy to endow conventional poly(4‐vinylpyridine) (PVP) derivatives with ultralong organic phosphorescence (UOP) under ambient conditions. After the ionization of 1,4‐butanesultone, the resulting PVP‐S phosphor showed a UOP lifetime of 578.36 ms, which is 525 times longer than that of PVP polymer itself. Remarkably, multicolor UOP emission ranging from blue to red was observed with variation of the excitation wavelength, which has rarely been reported for organic luminescent materials. This finding not only provides a guideline for developing amorphous polymers with UOP properties, but also extends the scope of room‐temperature phosphorescence (RTP) materials for practical applications in photoelectric fields.     

Stable luminescence from individual carbon nanotubes in acidic, basic, and biological environments

Aqueous surfactant suspensions of single walled carbon nanotubes (SWNTs) are very sensitive to environmental conditions. For example, the photoluminescence of semiconducting SWNTs varies significantly with concentration, pH, or salinity. In most cases, these factors restrict the range of applicability of SWNT suspensions. Here, we report a simple strategy to obtain stable and highly luminescent individualized SWNTs at pH values ranging from 1 to 11, as well as in highly saline buffers. This strategy relies on combining SWNTs previously suspended in sodium dodecylbenzene sulfonate (SDBS) with biocompatible poly(vinyl pyrrolidone) (PVP), which can be polymerized in situ to entrap the SWNT-SDBS micelles. We present a model that accounts for the photoluminescence stability of these suspensions based on PVP morphological changes at different pH values. Moreover, we demonstrate the effectiveness of these highly stable suspensions by imaging individual luminescent SWNTs on the surface of live human embryonic kidney cells (HEK cells).     

Thermally Triggered Frame‐Guided Assembly

We report a thermally triggered frame‐guided assembly (FGA) strategy for the preparation of vesicles. We employ thermally responsive poly(propylene oxide) (PPO) to make the leading hydrophobic groups (LHGs) thermally responsive, so that they are hydrophilic below the low critical solution temperature (LCST) and the frame forms in a homogeneous environment. When the temperature is increased above the LCST, the LHGs become hydrophobic and the assembly process is triggered, which drives DNA‐b‐PPO to assemble around the LHGs, forming vesicles. This work verified that FGA is a general strategy and can be applied to polymeric systems. The thermally triggered assembly not only provides more controllability over the FGA process but also promotes an in‐depth understanding of the FGA strategy and in a broad view, the formation mechanism and functions of cell membrane.     

Synthesis and Mechanical Properties of sub 5-μm PolyUiO-66 Thin Films on Gold Surfaces

Metal-organic framework (MOF) thin films currently lack the mechanical stability needed for electronic device applications. Polymer-based metal-organic frameworks (polyMOFs) have been suggested to provide mechanical advantages over MOFs, however, the mechanical properties of polyMOFs have not yet been characterized. In this work, we developed a method to synthesize continuous sub-5 μm polyUiO-66(Zr) films on Au substrates, which allowed us to undertake initial mechanical property investigations. Comparisons between polyUiO-66 and UiO-66 thin films determined polyUiO-66 thin films exhibit a lower modulus but similar hardness to UiO-66 thin films. The initial mechanical characterization indicates that further development is needed to leverage the mechanical property advantages of polyMOFs over MOFs. Additionally, the demonstration in this work of a continuous surface-supported polyUiO-66 thin film enables utilization of this emerging class of polyMOF materials in sensors and devices applications.     

Interaction of oxygen-sensitive luminescent probes Ru(phen)(3)(2+) and Ru(bipy)(3)(2+) with animal and plant cells in vitro. Mechanism of phototoxicity and conditions for non-invasive oxygen measurements.

Understanding the role of oxygen in the physiology, pathophysiology and radio- and chemosensitivity of animal cells requires accurate and non-invasive measurements of oxygen concentrations in the range of 0-2x10(-4) M, in cells in vitro or in vivo. High resolution 3D imaging techniques could be particularly useful in investigating tissue oxygenation in vivo and in model tissues (multicellular spheroids) in vitro. The goals of this work were to develop microscopy techniques and (i) to define conditions under which two oxygen-sensitive luminescent dyes, Ru(bipy)(3)(2+) (tris(2,2'-bipyridyl)ruthenium(II) chloride hexahydrate) and Ru(phen)(3)(2+) (tris(1,10-phenanthroline)ruthenium(II) chloride hydrate) can be used to probe oxygen concentrations within viable cells in vitro, when no phototoxic effects are evident, and (ii) to investigate the mechanism of phototoxicity once cell damage occurs. This report demonstrates that Ru(bipy)(3)(2+) and Ru(phen)(3)(2+) do not pass through intact biological membranes, do not cause measurable photodamage to plasma membranes at a concentration of 0.2 mM and, when loaded into endosomes, yield a strong luminescent signal. However, at an extracellular concentration of 1 mM, in the presence of 457-nm light, detectable amounts of both complexes accumulate at the plasma membrane and cause a loss of membrane integrity via a mechanism which may involve the generation of singlet oxygen.     

Photoswitchable and Reversible Fluorescent Eutectogels for Conformal Information Encryption

Smart fluorescent materials that can respond to environmental stimuli are of great importance in the fields of information encryption and anti-counterfeiting. However, traditional fluorescent materials usually face problems such as lack of tunable fluorescence and insufficient surface-adaptive adhesion, hindering their practical applications. Herein, inspired by the glowing sucker octopus, we present a novel strategy to fabricate a reversible fluorescent eutectogel with high transparency, adhesive and self-healing performance for conformal information encryption and anti-counterfeiting. Using anthracene as luminescent unit, the eutectogel exhibits photoswitchable fluorescence and can therefore be reversibly written/erased with patterns by non-contact stimulation. Additionally, different from mechanically irreversible adhesion via glue, the eutectogel can adhere to various irregular substrates over a wide temperature range (−20 to 65 °C) and conformally deform more than 1000 times without peeling off. Furthermore, by exploiting surface-adaptive adhesion, high transparency and good stretchability of the eutectogel, dual encryption can be achieved under UV and stretching conditions to further improve the security level. This study should provide a promising strategy for the future development of advanced intelligent anti-counterfeiting materials.     

New Wine in Old Bottles: Prolonging Room-Temperature Phosphorescence of Crown Ethers by Supramolecular Interactions

Supramolecular macrocyclic hosts have long been used in smart materials. However, their triplet emission and regulation at crystal level is rarely studied. Herein, ultralong and universal room-temperature phosphorescence (RTP) is reported for traditional crown ethers. A supramolecular strategy involving chain length adjustment and morphological locking through complexation with K⁺ was explored as a general method to tune the phosphorescence lifetime in the solid state. A maximum 10-fold increase of lifetime after complex formation accompanied with by invisible to visible phosphorescence was achieved. A deep encryption based on this activated RTP strategy was also facilely fabricated. This work thus opens a new world for supramolecular macrocycles and their intrinsic guest responsiveness offers a new avenue for versatile smart luminescent materials.     

Lanthanide Luminescent Nanocomposite for Non-Invasive Temperature Monitoring in Vivo

Temperature monitoring in vivo plays a vital role in the investigation of biological processes of organisms and the improvement of disease theranostic methods. The development of lanthanide luminescent nanocomposite-derived temperature probes in vivo allows accurate and reliable interrogation of biological thermodynamic processes due to their superior photostability, high sensitivity, and non-invasive sensing fashion. This concept presented an overview of the recent development of lanthanide luminescent nanocomposite which are suitable for in vivo temperature monitoring, including the thermometric principles, key features, materials designs as well as their potential biomedical applications for non-invasive temperature detection in the living body. The perspectives of these lanthanide luminescent nanocomposite thermometers for the optimization of temperature monitoring performance and potential future development are also discussed.     

Diverse effect of PEO-PPO-PEO and PPO-PEO-PPO triblock copolymers on temperature responsive behavior of luminescent hard-soft colloids

The present work introduces the interaction of hard and soft colloids in aqueous solutions at various temperatures and concentrations, as well as at critical conditions of temperature induced phase separation. Hard and soft colloids are represented by luminescent silica nanoparticles and aggregates of PEO-PPO-PEO and PPO-PEO-PPO triblock copolymers correspondingly. The formation of the mixed aggregates between hard and soft colloids in equilibrium conditions has been revealed by dynamic light scattering measurements. The distribution of silica nanoparticles between aqueous and surfactant rich phases after phase separation highlights the effect of pH, architecture and concentration of triblock copolymers on the mixed hard-soft colloids aggregation at cloud point conditions. The peculiar aggregation and phase behavior of PPO-PEO-PPO pluronics should be assumed as the main reason of the enhanced mixed aggregation with SNs at increased temperatures and concentrated conditions.     

High‐Capacity Upconversion Wavelength and Lifetime Binary Encoding for Multiplexed Biodetection

Optical multiplexing plays an important role in fields ranging from advanced biological assays to security. However, conventional codes based on fluorescent color and intensity are limited to spectral overlap and background interference. Herein, we present a new multiplexing concept by manipulating the luminescence emission color and decay lifetimes of upconversion nanoparticles (τ_λ‐UCNPs) separately for the first time through designing the core/multi‐shell structure and controlled energy relay method. This new color/lifetime binary strategy exhibits exponentially scalable encoding capacity (>10⁵), three orders of magnitudes higher than that of conventional color/intensity way. The strategy enables the multiplexed detection of human papilloma virus (HPV) subtypes in patient samples and robust anti‐counterfeiting. This work opens new opportunities for optical multiplexing with luminescent materials.     

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

Materials with controllable luminescence colors are highly desirable for numerous promising applications, however, the preparation of such materials, particularly with color-controllable room-temperature phosphorescence (RTP), remains a formidable challenge. In this work, we reported on a facile strategy to prepare color-controllable RTP materials via the pyrolysis of a mixture containing 1-(2-hydroxyethyl)-urea (H-urea) and boric acid (BA). By controlling the pyrolysis temperatures, the as-prepared materials exhibited ultralong RTP with emission colors ranging from cyan, green, to yellow. Further studies revealed that multiple luminescent centers formed from H-urea, which were in-situ embedded in the B₂O₃ matrix (produced from BA) during the pyrolysis process. The contents of the different luminescent centers could be regulated by the pyrolysis temperatures, resulting in color-tunable RTP. Significantly, the luminescent center engineering and in-situ immobilization strategy not only provided a facile method for conveniently preparing color-controllable RTP materials, but also endowed the materials prepared at relatively lower temperatures with color-changeable RTP features under thermal stimulus. Considering their unique properties, the potential applications of the as-obtained materials for advanced anti-counterfeiting and information encryption were preliminarily demonstrated.     

Selective complexation and transport of europium ions at the interface of vesicles

The aim of the present work was to design functionalized lipidic membranes that can selectively interact with lanthanide ions at the interface and to exploit the interaction between membranes induced by this molecular-recognition process with a view to building up self-assembled vesicles or controlling the permeability of the membrane to lanthanide ions. Amphiphilic molecules bearing a beta-diketone unit as head group were synthesized and incorporated into phospholipidic vesicles. Binding of Eu(III) ions to the amphiphilic ligand can lead to formation of a complex involving ligands of the same vesicle membrane (intravesicular complex) or of two different vesicles (intervesicular complex). The effect of Eu(III) ions on vesicle behavior was studied by complementary techniques such as fluorimetry, light scattering, and electron microscopy. The formation of an intravesicular luminescent Eu/beta-diketone ligand (1/2) complex was demonstrated. The linear increase in the binding constant with increasing concentration of ligands in the membrane revealed a cooperative effect of the ligands distributed in the vesicle membrane. The luminescence of this complex can be exploited to monitor the kinetics of complexation at the interface of the vesicles, as well as ion transport across the membrane. By encapsulation of 2,6-dipicolinic acid (DPA) as a competing ligand which forms a luminescent Eu/DPA complex, the kinetics of ion transport across the membrane could be followed. These functional vesicles were shown to be an efficient system for the selective transport of Eu(III) ions across a membrane with assistance by beta-diketone ligands.     

Crosslink-enhanced strategy to achieve multicolor long-lived room temperature phosphorescent films with excellent photostability

Room temperature phosphorescence (RTP) films have recently attracted increasing attention due to their excellent luminescent properties for information encryption, optoelectronic devices, and sensors. However, polyvinyl alcohol (PVA) films with abundant hydrogen bonds to suppress triplet energy dissipation suffered from the humidity induced phosphorescence quenching under storage in the air for a long time. In this work, poly(acrylic acid) (PAA) was selected to crosslink PVA matrix through esterification reactions for preparing water resistant RTP films. The blue, cyan, and orange emissive RTP films were successfully obtained by incorporating three different organic compounds into PVA-PAA crosslinking films. Crosslinking strategy significantly improved the phosphorescence emissions of the doped films, and effectively blocked the absorption of water molecular, leading to the excellent photostability of the developed films. As a proof of concept, the white light phosphorescence film and anti-counterfeiting applications were successfully demonstrated.