Design of Soft/Hard Interface with High Adhesion Energy and Low Interfacial Thermal Resistance via Regulation of Interfacial Hydrogen Bonding Interaction.

Adhesion ability and interfacial thermal transfer capacity at soft/hard interfaces are of critical importance to a wide variety of applications, ranging from electronic packaging and soft electronics to batteries. However, these two properties are difficult to obtain simultaneously due to their conflicting nature at soft/hard interfaces. Herein, we report a polyurethane/silicon interface with both high adhesion energy (13535 J m-2) and low thermal interfacial resistance (0.89 × 10-6 m2 K W-1) by regulating hydrogen interactions at the interface. This is achieved by introducing a soybean-oil-based epoxy cross-linker, which can destroy the hydrogen bonds in polyurethane networks and meanwhile can promote the formation of hydrogen bonds at the polyurethane/silicon interface. This study provides a comprehensive understanding of enhancing adhesion energy and reducing interfacial thermal resistance at soft/hard interfaces, which offers a promising perspective to tailor interfacial properties in various material systems.

Elastomer Composites with High Damping and Low Thermal Resistance via Hierarchical Interactions and Regulating Filler.

Modern microelectronics and emerging technologies such as wearable electronics and soft robotics require elastomers to integrate high damping with low thermal resistance to avoid damage caused by vibrations and heat accumulation. However, the strong coupling between storage modulus and loss factor makes it generally challenging to simultaneously increase both thermal conductance and damping. Here, a strategy of introducing hierarchical interaction and regulating fillers in polybutadiene/spherical aluminum elastomer composites is reported to simultaneously achieve extraordinary damping ability of tan δ > 1.0 and low thermal resistance of 0.15 cm2 K W-1, which surpasses state-of-the-art elastomers and their composites. The enhanced damping is attributed to increased energy dissipation via introducing the hierarchical hydrogen bond interactions in polybutadiene networks and the addition of spherical aluminum, which also functions as a thermally conductive filler to achieve low thermal resistance. As a proof of concept, the polybutadiene/spherical aluminum elastomer composites are used as thermal interface materials, showing effective heat dissipation for electronic devices in vibration scenarios. The combination of outstanding damping performance and extraordinary heat dissipation ability of the elastomer composites may create new opportunities for their applications in electronics.

Low-cost flexible textile electrocatalyst for overall water splitting.

Through the braidability of cotton fiber and the richness of surface functional groups, cotton fiber can be woven into any shape, and catalytically active centers can be stably anchored on the fibers. During the electrocatalytic overall water splitting (OWS) process, catalyst shedding and activity reduction can be effectively avoided.

How chemical cross-linking and entanglements in polybutadiene elastomers cope with tearing.

New applications of elastomers, such as flexible electronics and soft robotics, have brought great attention to tear resistance since elastomers are prone to shear failure. Most elastomers contain chemical cross-links and entanglements. The effects of both on their mechanical properties have been intensively studied, while how they cope with tearing remains elusive. Here, in polybutadiene elastomers, we find that the energy release rate of tearing (Gtearing), often employed as a measure of tear resistance, is influenced synergistically by chemical cross-linking and entanglements, while its threshold (G0) is only related to the chemical cross-linking. At a low tear speed, the polybutadiene elastomers with low cross-linking density have Gtearing up to 4 times higher than their G0 compared to highly cross-linked ones. Different from conventional reinforcement due to volume dissipation of a polymer network, enhancement of Gtearing significantly depends on the degree of cross-linking. The enhancement of Gtearing at low cross-linking degrees may be related to a novel mechanism, the friction-strengthening phenomenon, which was possibly caused by the pull-out of the chains at a high degree of orientation.

The Synergy of Hydrogen Bond and Entanglement of Elastomer Captures Unprecedented Flaw Insensitivity Rate.

Elastomers are regarded as one of the best candidates for the matrix material of soft electronics, yet they are susceptible to fracture due to the inevitable flaws generated during applications. Introducing microstructures, sacrificial bonds, and sliding cross-linking has been recognized as an effective way to improve the flaw insensitivity rate (Rinsen ). However, these elastomers still prone to failure under tensile loads with the presence of even small flaws. Here, this work reports a polybutadiene elastomer with unprecedented Rinsen via the synergy of hydrogen bond and entanglement. The resulting polybutadiene elastomer exhibits a Rinsen  ≈1.075, which is much higher than those of reported elastomers. By molecular chain interaction and molecular chain conformation analysis, this work demonstrates that the synergistic effect of hydrogen bond dissociation and entanglement slip in the polybutadiene elastomers during stretching leads to the high Rinsen . Using polybutadiene elastomer as matrix of thermal interface materials, this work demonstrates effective heat transfer for strain sensor and electronic devices. In addition, cytocompatibility of the elastomers is verified by cell proliferation and live/dead viability assays. The combination of outstanding biocompatible and excellent mechanical properties of the elastomers creates new opportunities for their applications in electronic skin.

Photocatalytic reduction of Cr(VI) over cinder-based nanoneedle in presence of tartaric acid: Synergistic performance and mechanism.

Cr(VI) is a common heavy metal ion, which will seriously harm human body and environment. Therefore, the removal of Cr(VI) has become an attractive topic. In this work, cinder was used as a raw material to synthesize a nanoneedle material: γ-(AlOOH@FeOOH) (γ-Al@Fe). The physicochemical properties of γ-Al@Fe were thoroughly characterized, and its effectiveness as a catalyst for photocatalytic reduction of Cr(VI) was evaluated. The results showed that Cr(VI) could be efficiently reduced by γ-Al@Fe in the presence of tartaric acid (TA) under visible light. The variable factors on the reaction were investigated in detail, and the results showed that under optimal conditions (γ-Al@Fe 0.4 g/L, TA 0.6 g/L, pH 2), Cr(VI) was completely reduced within 7 min. Besides, scavenger experiments and EPR proved that O2• - and CO2• - played a significant role in the photocatalytic reduction of Cr(VI). TA acts as a sacrificial agent to trap the holes and generate strong reducing free radicals: CO2• -. Dissolving O2 could react with electrons to generate O2• -. This work discussed the performance and mechanism of photocatalytic reduction of Cr(VI) in detail, which provided a new idea for the resource utilization of solid waste and the treatment of heavy metal sewage.

Crystallinity-dependent photodegradation of metallic Bi in situ grown on perovskite Bi3TiNbO9 nanosheets toward antibiotic.

Owing to its wide band gap of ~3.2 eV, perovskite Bi3TiNbO9 only absorbs the solar spectrum in the ultraviolet range, which restricts its use as an effective photocatalyst. Here, a controllable and facile reduction strategy was adopted to promote the in-situ growth of metallic Bi in perovskite Bi3TiNbO9 nanosheets. The in-situ growth of metallic Bi extended photoresponse to cover the whole visible region. Adsorption of tetracycline hydrochloride (TC-H) on the surface of Bi3TiNbO9 with in-situ growth of metallic Bi (BTNOOV-Bi0) was dramatically enhanced, while BTNOOV-Bi0 exhibited a superior photocatalytic performance for tetracycline hydrochloride (TC-H) degradation under visible light irradiation with the degradation rate of 5 times higher than that of pristine Bi3TiNbO9. Moreover, the degradation activity was strongly dependent on the crystallinity of metallic Bi phase in BTNOOV-Bi0 samples. On the basis of experiment results, the visible-light driven catalytic mechanism of BTNOOV-Bi0 was elucidated. Besides, the in-situ growth of metallic Bi was also introduced in perovskite Bi5FeTi3O15, resulting in an enhanced photocatalytic activity, which indicated an enormous potential of this strategy in semiconductor structure tuning. Our study provides an effective approach to boost the performance of photocatalysts for solar-energy conversion.

Surface structure tuning of BiOCl nanosheets by the sequential introduction of oxygen vacancies, PO43- and Ag+ for boosting photodegradation of tetracycline hydrochloride.

The surface structure significantly impacts the physicochemical properties of semiconductors. Constructing heterojunction is a universal approach to tune surface structure, which can effectively accelerate the charge transfer at the interface. Here, BiOCl nanosheets which occupy high ratio of surface atoms to entire atoms were used as a model photocatalyst, and a strategy was proposed to tune its surface structure by sequential introduction of oxygen vacancies, PO43- and Ag+ on surface of BiOCl nanosheets. In order to inhibit the overgrowth of heterogeneous component, the excess PO43- was timely removed by centrifugation before adding Ag+. As a result, the as-obtained optimal sample which was confirmed to be a composite composed of BiOCl, BiPO4 and AgCl showed superior photocatalytic activity for tetracycline hydrochloride degradation with the rate of 38 times higher than that of pristine BiOCl, which was mainly attributed to the quick migration of photongenerated carrier. The active species h+ and •O2- played a vital role in this degradation process. Our strategy not only greatly saved investment of noble metal Ag, but also provide superior stability. On the basis of experimental results and density functional theory calculation, the visible-light driven catalytic mechanism was revealed.

Boosting Photocatalytic Performance in Mixed-Valence MIL-53(Fe) by Changing FeII/FeIII Ratio.

One of vital issues that inhibit photoactivity of metal-organic frameworks is the poor electrical conductivity. In this work, one-dimensional mixed-valence iron chains are used to improve this poor situation in MIL-53(Fe). A series of mixed-valence MIL-53(Fe) photocatalysts were obtained through heating at different temperatures in vacuum. The effect of FeII coordinatively unsaturated metal sites (CUS) and one-dimensional mixed-valence iron chains on their photocatalytic property was discussed. The experimental results indicated that mixed-valence MIL-53(Fe) with a reference FeII/FeIII ratio of 0.2725 displayed the best photocatalytic performance, which showed 96.28 and 95.01% removal efficiencies of RhB and TC-H in 100 min, respectively. Moreover, MIL-53(Fe) heated in vacuum displayed better catalytic activity than MIL-53(Fe) heated in air for RhB and TC-H degradation. Based on the analysis of various characterizations, the reinforced catalytic activity can be attributed to the charge mobilities in mixed-valence FeII/FeIII chains. It is worth mentioning that the method is also applicable to MIL-88(Fe) and MIL-101(Fe). Additionally, mixed-valence MIL-53(Fe) can also perform the catalysis reaction in the nighttime by activating persulfate (PS) to produce free radicals. Interestingly, it was found that the FeII CUS lost in activating PS can be supplemented by self-reduction of photogenerated electrons during illumination in the daytime, so as to achieve a more stable cycle. This work demonstrated that the photoactivity of MIL-53(Fe) can be improved by adjusting the ratio of FeII/FeIII and the feasibility of using as an all-day-active catalyst.

Exceptional Catalytic Activities of Iron Tungstophosphoric Acid Pillared Montmorillonite Photo-Fenton Catalyst for Organic Pollutant Decomposition.

Iron tungstophosphoric acid pillared montmorillonite (TPAFe-Mt) as a highly efficient, stable and visible-light-responsive photo-Fenton catalyst have successfully been prepared via an impregnation method. The TPAFe-Mt catalyst exhibits exceptional visible-light photo-Fenton catalytic activities for azo-dye methyl orange, phenol and 2,4-dinitrophenol in a wide pH range from 1.0 to 5.0. Especially, 40 mg/L of methyl orange could be completely degraded in 40 min, and the TOC removal rate was as high as 73.3%. The high catalytic performance arises from the following reasons: (i) The support of TPAFe rendered a significant increase in specific surface area and a slight increase in interlayer spacing of montmorillonite, thus improving the adsorption performance. (ii) The incorporation of tungstophosphoric acid (TPA) not only effectively anchor iron but also improved visible light absorption capacity, which greatly promoted the Fenton reaction. Moreover, the catalyst showed excellent chemical stability. After ten consecutive degradation cycles, the degradation efficiency still reached about 99% due to the good fixation iron of TPA. The possible mechanism involving in photo-Fenton process is proposed mainly based on the experimental result. This work opens up a new feasible route to synthesize visible-light-responsive high-activity photo-Fenton catalyst for efficient environmental remediation.

Fe1-xZnxS ternary solid solution as an efficient Fenton-like catalyst for ultrafast degradation of phenol.

Heterogeneous Fenton-like system has been proved to be an promising alternative to Fenton system due to its easy separation. However, it's a challenge to design heterogeneous Fenton-like catalysts with high activity and great durability. Here, ternary solid solution Fe1-xZnxS were prepared via hydrothermal synthesis as heterogeneous Fenton-like catalysts. The Fe0.7Zn0.3S sample exhibited state of the art activity for yielding OH by H2O2 decomposition, and the ultrafast degradation of phenol was achieved in 4 min at initial acidic condition under room temperature. The phenol degradation rate constant of Fe0.7Zn0.3S was 99 and 70 times of ZnS and FeS, respectively. Further, we show that the unique structural configuration of iron atoms, the formation of FeS2-pyrite with (200) plane, are responsible for the excellent activity. The intermediate products were identified by LC-MS and a possible pathway was accordingly proposed to elucidate the mechanism of phenol degradation by OH. Overall, this work provides an idea for the rational design of the relevant heterogeneous Fenton-like catalysts.

Polycarbonate-based core-crosslinked redox-responsive nanoparticles for targeted delivery of anticancer drug.

We reported a facile and efficient strategy for the construction of polycarbonate-based core-crosslinked redox-responsive nanoparticles (CC-RRNs), which can efficiently regulate the drug loading content and redox-responsive drug release. A series of CC-RRNs for delivery of doxorubicin (DOX) were synthesized by the click reaction between alkyne-bearing amphiphilic block copolymer PEG-b-poly(MPC)n (PMPC) and azide-terminated α-lipoic acid derivative (LA) and 6-bromohexanoic acid derivative (AHE) at different ratios, followed by introduction of crosslinked networks under a catalytic amount of dithiothreitol (DTT). Dynamic light scattering (DLS) experiments showed that the CC-RRNs presented more excellent stability over non-crosslinked unresponsive nanoparticles (NC-URNs) under physiological conditions. Interestingly, the DOX loading content of nanoparticles (NPs) increased as the proportion of LA moieties increased, and the maximum value was up to 20.0 ± 0.6%, close to the theoretical value of 23.1%. The in vitro redox-responsive release of DOX and MTT assays confirmed that the ratio of LA-to-AHE of PMPC-based polymers not only determined the ultimate drug release of DOX-loaded CC-RRNs in a reductive environment, but also dominated the cytotoxicity towards HepG2 cells. Confocal laser scanning microscopy (CLMS) and flow cytometry further proved the enhancement of cellular uptake and tumor accumulation. This facile strategy overcomes tedious fabrication procedures for drug nanocarriers, offers an opportunity for regulating the functionality of NPs, and thus paves the pathway for scale-up production of biodegradable drug carriers with biocompatibility, stability and targetability.

Hydroxyalkylation of phenol to bisphenol F over heteropolyacid catalysts: The effect of catalyst acid strength on isomer distribution and kinetics.

Hydroxyalkylation of phenol with formaldehyde to bisphenol F over heteropolyacid impregnated on clay was investigated. These catalysts displayed excellent catalytic performance for this reaction, especially that the effects of acid sites on the isomer distribution are obvious. Various solid catalysts were prepared by impregnating heteropolyacid on different kind of clay matrices, and their chemical compositions, textural properties, and acid strength of the heteropolyacid catalysts were characterized by EDX, BET, NH3-TPD, XRD, and FT-IR. Moreover, the effects of acid sites and reaction temperature on the yield and 4,4'-isomer distribution were launched by comparing the data obtained from the two kinds of catalysts. Furthermore, the kinetics of the hydroxyalkylation of phenol to BPF was established.