of 140 °C or above. [4,5] While dielectric ceramics are traditional materials for high-temperature capacitors, [6] they are severely limited by scalability, weight, fracture toughness, and breakdown strength in comparison to their polymer counterparts. [7][8][9][10][11][12][13][14][15][16][17] Biaxially oriented polypropylene film (BOPP), the state-of-the-art commercially available polymer dielectric, however, shows largely degraded high-field dielectric properties when operating at temperatures above 100 °C. [18] To address these imperative needs, a variety of well-established engineering polymers, including polycarbonate, polyimide (PI), polyetherimides, and poly(ether ether ketone), have been exploited as hightemperature dielectric materials. [19][20][21][22][23][24][25] As these aromatic polymers have high glass transition temperatures (T g ) and excellent thermal stability, it is anticipated that the engineering polymers would retain electromechanical properties and thus dielectric stability at high temperatures. However, when subjected to high applied fields, the engineering polymers exhibit limited working temperatures that are much lower than their T g s. [19,20] More recently, inorganic fillers represented by boron nitride nanosheets (BNNSs) have been incorporated into crosslinked divinyltetramethyldisiloxane-bis(benzocyclobutene) (c-BCB) to yield the dielectric polymer composites capable of operating efficiently at high temperatures, e.g. 150 °C. [26][27][28][29] Herein, we describe the hightemperature dielectric properties and capacitive performance of the PI-based polymer nanocomposites prepared via in situ polycondensation. Compared with c-BCB, PI possesses the inherent advantages including much better processability, considerably lower cost, and greater mechanical strength and flexibility, which potentially offers a scalable route toward robust hightemperature dielectric materials. [30,31] The investigation of the polymer composites containing the inorganic nanofillers with systematically varied dielectric constants (K) and bandgap (ΔE), including aluminium oxide (Al 2 O 3 ) with a K of 9.5 and a ΔE of 8.6 eV, hafnium dioxide (HfO 2 ) with a K of 25 and a ΔE of 5.8 eV, titanium dioxide (TiO 2 ) with a K of 110 and a ΔE of 3.5 eV, and BNNS with a K of 4 and a ΔE of 5.97 eV, [26,[32][33][34] would provide experimental guidelines for the design of highperformance high-temperature dielectric polymer composites. Modern electronics and electrical systems demand efficient operation of dielectric polymer-based capacitors at high electric fields and elevated temperatures. Here, polyimide (PI) dielectric composites prepared from in situ polymerization in the presence of inorganic nanofillers are reported. The systematic manipulation of the dielectric constant and bandgap of the inorganic fillers, including Al 2 O 3 , HfO 2 , TiO 2 , and boron nitride nanosheets, reveals the dominant role of the bandgap of the fillers in determining and improving the high-temperature capacitive performance of the polymer compo...

The increasing demands for optical anti-counterfeiting technology require the development of versatile luminescent materials with multiple models and tunable photoluminescence. Herein, the combination of luminescent perovskite nanocrystals and lanthanide-based metal-organic frameworks (Ln-MOFs) has been developed to offer such a high-tech anti-counterfeiting solution. The hybrid materials have been fabricated via the encapsulation of perovskite CHNHPbBr nanocrystals in europium-based metal-organic frameworks (Eu-MOFs) and they display multistage anti-counterfeiting behavior. CHNHPbBr@Eu-MOF hybrids were developed in a two-step process, where the PbBr@Eu-MOF precursor was formed first and, then, the composites can be formed quickly by the addition of CHNHBr into the precursors. Accordingly, the hybrid composites exhibited both excitation wavelength and temperature-dependent luminescence properties in the form of powders or films. Furthermore, the photoluminescence of the CHNHPbBr@Eu-MOF composites can be quenched and recovered through water immersion and CHNHBr conversion, and the anti-counterfeiting applications have also been discussed. Therefore, this finding will open the opportunity to fabricate the hybrid materials with controlled photoluminescence properties, and it also acts as the emerging anti-counterfeiting materials in versatile fields.

For the first time, structurally defined manganese pincer complexes catalyze the dehydrogenation of aqueous methanol to hydrogen and carbon dioxide, which is a transformation of interest with regard to the implementation of a hydrogen and methanol economy. Excellent long-term stability was demonstrated for the Mn-PNPiPr catalyst, as a turnover of more than 20 000 was reached. In addition to methanol, other important hydrogen carriers were also successfully dehydrogenated.

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We investigated the evolution in silver nanoparticle (AgNP) properties during a series of 10-50 day experiments on suspensions with different pH (5-9), electrolyte type (NaNO and NaCl) and concentration (2 and 6 mM), Suwannee River humic acid (SRHA) concentration (0-13.2 mg C/L), and light exposure (artificial sun light exposure for 8 h per day or dark). Of these factors, pH most influenced the AgNPs' properties as it modifies surface charge as well as AgNP dissolution and oxidation and Ag reduction reactions. As a result, particle behavior differed in basic and acidic conditions. Trends with pH varied, however, based on the electrolyte and SRHA concentration. In the presence of chloride which forms AgCl(s), for example, we observed the particle size decreased with increasing pH. The opposite was observed in identical systems in NaNO. This behavior was modified by SRHA, with increasing SRHA reducing dissolution and enhancing stability. Light exposure enhanced processes resulting in AgNP dissolution, resulting in higher dissolved Ag concentrations than under similar conditions in the dark. Overall, our results highlight how AgNP properties evolve over time and provide insight needed to confidently extend model system behavior to predict the environmental fate of AgNPs.

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The influences of the free volume and the termperature on the damping property of chlorinated isoprene-isobutylene rubber (CIIR) were first investigated by positron annihilation lifetime spectroscopy (PALS), dynamic mechanical analysis (DMA), and differential scanning calorimetry (DSC), respectively. From the variations of ortho-positronium (o-Ps) lifetimes as a function of temperature, two transition temperatures can be observed, i.e., Tg and TB. We found that there exists a pre-rubbery state between the glass transition temperature Tg and TB. The DMA results indicate that the tan delta peak of CIIR has a very broad temperature distribution because of the existence of a liquid-liquid transition (Tll). The temperature dependence of the average free volume size can be linearly fitted below Tg and above TB, respectively. It is very interesting that the difference spectrum of the free volume size between the results fitted by two lines (below Tg and above TB) and experimental data is very similar to the dynamic mechanical spectrum of CIIR. In order to clarify the damping mechanics, the Williams-Landel-Ferry (WLF) equation based on free volume theory has been successfully used to establish a direct quantificational relationship between the free volume and the damping property, which indicates that the free volume plays an important role in determining the damping property.

The importance of mitochondrial delivery of an anticancer drug to cancer cells has been recognized to improve therapeutic efficacy. The introduction of lipophilic cations, such as triphenylphosphonium (TPP), onto the surface of nanocarriers was utilized to target mitochondria via strong electrostatic interactions between positively charged TPP and the negatively charged mitochondrial membrane. However, the highly positive charge nature of TPP leads to rapid clearance from the blood, decrease of circulation lifetime, and nonspecific targeting of mitochondria of cells. Here, we report a strategy for improving the anticancer efficacy of paclitaxel via redox triggered intracellular activation of mitochondria-targeting. The lipid-polymer hybrid nanoparticles (LPNPs) are composed of poly(d,l-lactide-co-glycolide) (PLGA), a TPP-containing amphiphilic polymer (C-PEG-TPP) and a reduction-responsive amphiphilic polymer (DLPE-S-S-mPEG). The charges of TPP in LPNPs were almost completely shielded by surface coating of a PEG layer, ensuring high tumor accumulation. After uptake by cancer cells, the surface charges of LPNPs were recovered due to the detachment of PEG under intracellular reductive conditions, resulting in rapid and precise localization in mitochondria. This kind of simple, easy and practicable mitochondria-targeting nanoplatform showed high anticancer activity, and the activatable strategy is valuable for developing a variety of nanocarriers for application in the delivery of other drugs.