Dongpeng Yan

Fabrication of host–guest UV-blocking materials by intercalation of fluorescent anions into layered double hydroxides

Materials for blocking UV light play important roles in a variety of areas such as protecting the human skin and increasing the lifetime of polymers. In this work, a new type of host–guest UV-blocking material has been synthesized by the introduction of a fluorescent anion, 2-[2-[4-[2-(4-carboxyphenyl)vinyl]phenyl]vinyl]benzoate (CPBA), into the interlayer galleries of a ZnAl–NO3 layered double hydroxide (LDH) precursor by an anion-exchange method. The structure and the thermal and photostability of the intercalated ZnAl–CPBA-LDH were investigated by powder X-ray diffraction (XRD), infrared spectroscopy (FTIR), thermogravimetry and differential thermal analysis (TG-DTA), fluorescence spectroscopy and UV-vis spectroscopy. The supramolecular layered host–guest structure of ZnAl–CPBA-LDH enables both physical shielding and absorption of UV light. Furthermore, in contrast to conventional UV blocking materials—which convert UV light into thermal energy—the CPBA anions in the LDH interlayer galleries convert UV light (in the range 250–380 nm) into lower energy fluorescence emission (λemmax = 430 nm), thus reducing the thermal aging of the polymer composite materials. Intercalation of the CPBA anions into the LDH host also markedly enhances the thermal stability of CPBA. In polypropylene (PP) aging performance tests, after adding 1–5 wt% ZnAl–CPBA-LDH to PP, the resistance to UV degradation of the resulting ZnAl–CPBA-LDH/PP composites is higher than that of pristine PP or a CPBA/PP composite. Therefore, this work provides a way to construct a new type of host–guest layered material for UV-blocking applications.

Micro‐/Nanostructured Multicomponent Molecular Materials: Design, Assembly, and Functionality

Molecule-based micro-/nanomaterials have attracted considerable attention because their properties can vary greatly from the corresponding macro-sized bulk systems. Recently, the construction of multicomponent molecular solids based on crystal engineering principles has emerged as a promising alternative way to develop micro-/nanomaterials. Unlike single-component materials, the resulting multicomponent systems offer the advantages of tunable composition, and adjustable molecular arrangement, and intermolecular interactions within their solid states. The study of these materials also supplies insight into how the crystal structure, molecular components, and micro-/nanoscale effects can influence the performance of molecular materials. In this review, we describe recent advances and current directions in the assembly and applications of crystalline multicomponent micro-/nanostructures. Firstly, the design strategies for multicomponent systems based on molecular recognition and crystal engineering principles are introduced. Attention is then focused on the methods of fabrication of low-dimensional multicomponent micro-/nanostructures. Their new applications are also outlined. Finally, we briefly discuss perspectives for the further development of these molecular crystalline micro-/nanomaterials.

Nanohybrids of organo-modified layered double hydroxides and polyurethanes with enhanced mechanical, damping and UV absorption properties

The construction of high-performance polymer–clay nanocomposites plays an important role in developing new types of organic–inorganic hybrids. In this work, a series of polymer–clay nanocomposites were prepared based on polyurethane (PU) and chemical grafting of γ-aminopropyltriethoxysilane (APS) onto dodecyl sulfonate (DS) intercalated MgAl layered double hydroxide (APS–DS–LDH). The detailed morphology, damping properties, mechanical behavior, thermal stability as well as ultraviolet absorption ability of the PU/LDH nanocomposites were studied systematically. Results reveal that the addition of APS grafted DS/LDH nanoparticles can enhance the damping properties and the thermal decomposition temperature, compared with the pristine PU. A mechanical test shows that the flexibility of the nanocomposites is significantly improved by the incorporation of APS–DS–LDH, especially for the LDH content of 3%. Meanwhile, ultraviolet absorption intensity also increases by 33%. It is expected that the PU/APS–DS–LDH nanocomposites can be used as structural damping materials and elastomers in practical applications.

Stimuli-responsive fluorescence based on the solid-state bis[2-(2-benzothiazoly)phenolato]zinc(II) complex and its fiber thin film

While metal-based complexes with single-stimulus-responsive fluorescence have been largely developed recently, examples of dual-stimuli-responsive systems are still relatively limited. In this work, a bis[2-(2-benzothiazoly)phenolato]zinc(II) complex was synthesized through a one-step solution process, and the as-prepared solid-state sample exhibited fluorescent emission changes upon dual external stimuli such as mechanical force and pH. In addition, the related luminescent properties (such as wavelength, fluorescence lifetime, color, and two-photon emission) after mechanical- and pH-stimuli can be easily recovered and recycled several times. Moreover, to develop a film material for easy operation, the Zn(BTZ)2 complex was further incorporated into a poly(vinyl alcohol) (PVA) matrix to obtain a microfiber thin film based on an electrospinning process, and the as-fabricated Zn(BTZ)2@PVA system showed changeable luminescence upon heat treatment. These observations confirm that the Zn(BTZ)2 complex is a stimuli-responsive luminescent system sensitive to pH and force external changes in the powder state, and sensitive to temperature changes in the film state. Therefore, compared with the well-developed noble metal-based complexes with stimuli-responsive properties, this work suggests that the Zn-based complex can provide an alternative to develop potential low-cost luminescent sensors and optical antiforgery systems.

Novel Eu-containing titania composites derived from a new Eu(III)-doped polyoxotitanate cage

A new Eu(III)-doped polyoxotitanate (POT) cage [Ti2O(OEt)8(EtOH)EuCl]2 can be used as a single-source precursor for the formation of nanostructured Eu-containing titania composites and flexible fluorescent films, which exhibit significant red luminescence and are attractive fluorescent materials.

Nano-photosensitizer based on layered double hydroxide and isophthalic acid for singlet oxygenation and photodynamic therapy

Singlet oxygen has won a great deal of attention to catalysis and biological studies due to its strong oxidizing properties. However, the photosensitizers which require for the generation of singlet oxygen remain inadequate because of their lack of long-wavelength absorption, weak hydrophilicity, and poor biocompatibility. Here, we develop near-infrared laser activated supramolecular photosensitizers (isophthalic acid/layered double hydroxide nanohybrids) for efficient two-photon photodynamic therapy. The singlet oxygen quantum yield of nanohybrid is up to 0.74. Critically, in vitro tests verify the superior anti-cancer properties of nanohybrid with an IC50 determine to be 0.153 μg mL−1. The nanohybrids take advantage of the superior tissue penetration of 808 nm laser irradiation and exhibit a dramatically strong ability to ablate tumors in vivo, with extremely low toxicity. This work provides the proof of concept that ultralong-lived triplet excitons can function as two-photon-activated photosensitizers for an effective singlet oxygen generation.Usually, several components are needed for efficient 2-photon photodynamic therapy (PDT). Here, the authors sandwiched carboxylic acids between layered double hydroxide nanosheets to obtain a single-handed biocompatible photosensitizer that generates singlet oxygen in high quantum yield.

Recent Advances in Micro-/Nanostructured Metal-Organic Frameworks towards Photonic and Electronic Applications

Micro- and nanometer-sized metal-organic frameworks (MOFs) materials have attracted great attention due to their unique properties and various potential applications in photonics, electronics, high-density storage, chemo-, and biosensors. The study of these materials supplies insight into how the crystal structure, molecular components, and micro-/nanoscale effects can influence the performance of inorganic-organic hybrid materials. In this Minireview article, we introduce recent breakthroughs in the controlled synthesis of MOF micro-/nanomaterials with specific structures and compositions, the tunable photonic and electronic properties of which would provide a novel platform for multifunctional applications. Firstly, the design strategies for MOFs based on self-assembly and crystal engineering principles are introduced. Attention is then focused on the methods of fabrication of low-dimensional MOF micro-/nanostructures. Their new applications including two-photon excited fluorescence, multi-photon pumped lasing, optical waveguides, nonlinear optical (NLO), and field-effect transistors are also outlined. Finally, we briefly discuss perspectives on the further development of these hybrid crystalline micro-/nanomaterials.