Construction of 1D Heterogeneous Co/C@Ag Nws With Tunable Electromagnetic Wave Absorption And Shielding Performance.

In this study, silver nanowires (Ag NWs) are synthesized at first, and then the 1D heterogeneous Co/C@Ag NWs with a kebab- and popsicle-like microstructures are constructed by in situ growth ZIF-67 on Ag NWs combined with calcination. Results show that the EM wave prevention performance of composites depends on the loading of Co/C particles threaded on the Ag NWs. The popsicle-like structure with high Co/C loading gives Co/C@Ag NWs excellent EM wave absorption performance, which achieved a minimum reflection loss (RLmin ) of -44.5 dB with a low filling of 30 wt.% in paraffin; while the kebab-like structure with low Co/C loading shows good electromagnetic interference (EMI) shielding effectiveness (SET ) of 30.2 dB at the same filler ratio. The enhanced EM wave absorption performance is attributed to the synergy of multiple energy dissipation mechanisms including dielectric loss, magnetic loss, polarization loss, eddy-current loss, multiple reflection loss, as well as proper impedance matching; the good EMI shielding performance is mainly due to the conduction loss brought by the Ag NWs with ultrahigh conductivity. This work provides a reference for the design of electromagnetic wave prevention material with tuned absorption and shielding performance.

Rational design of heterointerface between MoO2 and N-doped carbon with tunable electromagnetic interference shielding capacity.

Exploring highly efficient electromagnetic interference (EMI) shielding filler is urgently desired for next-generation wireless communication and integrated electronics. In this regard, a series of heterogeneous MoO2/N-doped carbon (MoO2/NC) nanorods with tunable conductivity have been successfully synthesized by regulating the pyrolysis temperature within 600, 700 and 800 °C. Profiting from the rational design of heterointerface and low-dimensional structure, the MoO2/NC powder achieves stronger EMI shielding capacity with the incremental temperature. It is found that the MoO2/NC-800 nanorods exhibit the optimal average EMI shielding effectiveness (SE) of 57.2 dB at a thickness of ∼0.3 mm in the X band. Meanwhile, the corresponding shielding mechanisms of MoO2/NC nanorods are also elaborately explained. More interestingly, the increase of sintering temperature makes an obvious effect on absorption loss but has little influence on reflection loss, demonstrating that adjusting the pyrolysis temperature is an effective strategy to strengthen the electromagnetic energy dissipation.

Heterostructured ZnCdS@ZIF-67 as a Photocatalyst for Fluorescent Dye Degradation and Selectively Nonenzymatic Sensing of Dopamine.

Dopamine (DA) plays the role of the transmitter of information in the brain. Neurological diseases and depression are in close relationship with DA release. In this study, we developed a co-catalyst Zn0.2Cd0.8S@zeolitic imidazolate framework-67 (Zn0.2Cd0.8S@ZIF-67) to improve the photocatalyst efficacy of Rhodamine B (RhB) and electrochemical sensing of DA. Results show that Zn0.2Cd0.8S@ZIF-67 exhibits optimal photocatalytic activity with the addition of 80 mg ZIF-67. The degradation percentage of RhB by Zn0.2Cd0.8S@ZIF-67 reached 98.40% when the co-catalyst was 50 mg. Radical trapping experiments show that ·O2- played a significant role in the photocatalytic degradation of RhB. The catalytic mechanism of the Zn0.2Cd0.8S@ZIF-67 was found as a Z-type photocatalysis. Finally, a DA biosensor was constructed and displayed a high response and selectivity to DA. This can be attributed to the heterojunction between Zn0.2Cd0.8S and ZIF-67, which can significantly enhance the separation of e-/h+ and improve charge transfer. These findings will play a positive role in the in-situ monitoring of neurological diseases and depression.

A facile method of functional derivatization based on starch acetoacetate.

In the present work, we constructed a methodology to graft starch with special groups, such as alkyl, phenolic, naphthalimide derivatives (ND) and polymer, by a simple reaction under generally mild conditions without catalysts or UV irradiation, based on precursor starch acetoacetate (SAA). The completeness of these reactions has been proved to be ideal. After grafting, the starch derivatives have some common changes, for instance, their solubility is improved in certain solvents. On the other hand, the introduction of different functional groups will also bring some characteristics to the derivatives (e.g. ND brings fluorescence). In addition, part of the derivatives shows excellent machinability, and their hot-pressed samples exhibit great transparency and mechanical strength. Specially, the alkyl grafted starch displays excellent toughness, properties of deformation and self-recovery. In conclusion, this method has good universality and methodological significance, and offers insights into the larger-scale industrial application of starch.

Construction of one-dimensional MoO2/NC heteronanowires for microwave absorption.

A combination of a special micro-nanostructure and multiple components has been proven as an effective strategy to strengthen the microwave attenuation capacity. In this work, one-dimensional MoO2/N-doped carbon (NC) nanowires with a heterostructure have been successfully prepared by utilizing mild in situ chemical oxidative polymerization and pyrolysis treatment. After compounding them with a thermoplastic polyurethane (TPU) matrix, the flexible composites exhibit tunable wave absorbing performance by modulating the filler loading of MoO2/NC heteronanowires. Experimental results demonstrate that the minimum reflection loss value of the MoO2/NC-TPU hybrid is up to -35.0 dB at 8.37 GHz under a thickness of only 2.3 mm with 40 wt% filler amounts. Moreover, the effective absorption bandwidth enables 3.26 GHz to be achieved (8.49-11.75 GHz) when the thickness changes to 2.0 mm, covering almost the whole X-band. Meanwhile, when the filler loading becomes 30 wt%, dual-absorption peaks appear. The relevant absorption mechanism is mainly attributed to the dielectric loss including strong dipolar/interfacial polarizations, Debye relaxation loss and multiple reflection and scattering.

Facile Fabrication of PBS/CNTs Nanocomposite Foam for Electromagnetic Interference Shielding.

In order to reduce the pollutants of environment and electromagnetic waves, environment friendly polymer foams with outstanding electromagnetic interference shielding are imminently required. In this paper, a kind of electromagnetic shielding, biodegradable nanocomposite foam was fabricated by blending poly (butylene succinate) (PBS) with carbon nanotubes (CNTs) followed by foaming with supercritical CO2 . The crystallization temperature and melting temperature of PBS/CNTs nanocomposites with 4 wt % of CNTs increased remarkably by 6 °C and 3.1 °C compared with that of pure PBS and a double crystal melting peak of various PBS samples appeared in DSC curves. Increasing the CNT content from 0 to 4 wt % leads to an increase of approximately 3 orders of magnitude in storage modulus and nearly 9 orders of magnitude in enhancement of electrical properties. Furthermore, CNTs endowed PBS nanocomposite foam with adjustable electromagnetic interference (EMI) shielding property, giving a specific EMI shielding effectiveness of 28.5 dB cm3 /g. This study provides a promising methodology for preparing biodegradable, lightweight PBS/CNTs foam with outstanding electromagnetic shielding properties.

Antioxidant Behavior Affected by Polarity in the Olive Oil: Experimental and Molecular Simulation Investigations.

Natural antioxidants are essential potential sources for protecting the oxidation of food oils. However, until now, the mechanisms are still not very clear, especially from the quantitatively theoretical level to analyze the antioxidant behavior. In this work, the micromechanisms of the antioxidant behavior affected by polarity in the olive oil were systematically investigated by experimental and computational methods. The results showed that the polarity of antioxidants decreased with the growth of the alkyl chains, which had multiple impacts on the effectiveness of antioxidants. The excessive polarity gap between the antioxidant and oil molecules would cause the antioxidant to be dispersed at the oil-air interface, which could enhance their antioxidant ability. Meanwhile, the antioxidants with longer alkyl chains had lower polarity and better dispersibility but decreased mobility. Hence, compared with other antioxidants, medium polarity antioxidants presented both good dispersion and relatively suitable migration, indicating that they would have an optimal antioxidant effect.

Highly Thermally Conductive and Superior Electrical Insulation Polymer Composites via In Situ Thermal Expansion of Expanded Graphite and In Situ Oxidation of Aluminum Nanoflakes.

Polymer composites with highly thermally conductive and electrical insulation are urgently demanded for thermal management in modern electrical and energy applications. However, the incorporation of metal fillers in traditional polymeric composites usually fails to meet the requirements for simultaneously high thermal conductivity and high electrical insulation. Here, we successfully fabricated composites with high thermal conductivity and high electrical insulation by in situ thermal expansion of expandable graphite (EG) and in situ oxidation of aluminum (Al) nanoflakes in aluminum-plastic package waste (APPW). Due to the synergistic effect of the hybrid filler framework, the maximum thermal conductivity reached as high as 8.7 W m-1 K-1 for APPW/EG10/Al60-F composites. In addition, the formation of the nano Al2O3 layer around the Al filler surface brings extremely low electrical conductivity (<10-14 S cm-1) and low dielectric loss (<0.06). Based on the results of finite element simulation, the heat flowed mainly along the effective filler framework and the high thermal conductivity is attributed to the interconnection of the high aspect ratio filler. Furthermore, the strong thermal management capability of the prepared composites was demonstrated in the heat dissipation experiment. The present work suggests that surface-oxidized Al nanoflakes demonstrate fascinating performance and show promising application as thermal management materials in emerging electrical systems and electronic devices.

Anomalously Shaped Functional Particles Prepared by Thiol-Isocyanate Off-Stoichiometric Click Dispersion Polymerization.

Anomalously shaped microparticles have attractive advantages in applications. They are usually prepared by chain-growth polymerizations in heterogeneous systems. Recently, thiol-X step-growth polymerizations have been used to produce functional particles with a regular shape but rarely anomalous shapes. Herein, we report the preparation of anomalously shaped particles by thiol-isocyanate dispersion polymerization (Dis.P) in ethanol using polyvinylpyrrolidone (PVP) as a stabilizer and catalyst. Papillae-shaped, raspberry-like, and multibulged particles are prepared by tuning monomer combinations, contents, and feed ratios. Particle morphology evolutions during polymerization are observed by scanning electron microscopy (SEM). Distinct from previous works, particles with residual -SH groups are obtained even with equal moles of monomers added initially. The residue of -SH groups is revealed by Fourier transform infrared spectroscopy (FT-IR) analyses and confirmed by detection with a fluorescent probe containing disulfide linkage. Moreover, fluorescent particle probes are formed by the reaction of excess -NCO groups on particles with fluorescein isothiocyanate isomer I (FITC) and dithioacetal-functionalized perylenediimide (DTPDI). The probes are sensitive in detection of glutathione (GSH) and Hg2+ in water. Hg2+ as low as 1-0.1 ppb is detected using a raspberry-like particle probe with DTPDI.

Recent Advances in the Construction of Flexible Sensors for Biomedical Applications.

The fabrication of flexible sensors is a potential way to promote the progress of modern social science and technology due to their wide applications in high-performance electronic equipment and devices. Flexible sensors based on organic materials combine the unique advantages of flexibility and low cost, increasing interest in healthcare monitoring, treatment, and human-machine interfaces. Advances in materials science and biotechnology have rapidly accelerated the development of bio-integrated multifunctional sensors and devices. Due to their excellent mechanical and electrical properties, many types of functional materials provided benefits for the construction of various sensors with improved flexibility and stretchability. In this review, recent advance in the fabrication of flexible sensors by using functional nanomaterials including nanoparticles, carbon materials, metal-organic materials, and polymers is presented. In addition, the potential biomedical applications of the fabricated flexible sensors for detecting gas molecules signals, small molecules, DNA/RNA, proteins, others are introduced and discussed.

Practical PBT/PC/GNP composites with anisotropic thermal conductivity.

Most of the highly thermally conductive polymer-based composites currently face problems that must be solved before they can be directly used in industrial production. Herein, a practical polybutylene terephthalate (PBT)/polycarbonate (PC)/graphite nanoplatelet (GNP) thermally conductive composite with relative low filler content was prepared by a conventional melt-blending technique. GNPs selectively distributed and oriented in the PBT phase afford the composite a low percolation threshold and anisotropic thermal conductivity. Investigation of the influence of filler content on the final comprehensive performance showed that a prepared PBT/PC/GNP composite with 20 vol% GNPs exhibited superior performance in thermal conductivity, heat resistance, and mechanical properties. The in-plane and through-plane thermal conductivities of the composite were 5.82 W m-1 K-1 and 1.06 W m-1 K-1, respectively, which were increased by 2430% and 361% as compared to that of a neat PBT/PC blend. The Vicat softening temperature increased by 17.7 °C and reached 213.7 °C, while the mechanical properties also maintained a good application level.

A Novel Polyaniline-Coated Bagasse Fiber Composite with Core-Shell Heterostructure Provides Effective Electromagnetic Shielding Performance.

A facile route was proposed to synthesize polyaniline (PANI) uniformly deposited on bagasse fiber (BF) via a one-step in situ polymerization of aniline in the dispersed system of BF. Correlations between the structural, electrical, and electromagnetic properties were extensively investigated. Scanning electron microscopy images confirm that the PANI was coated dominantly on the BF surface, indicating that the as-prepared BF/PANI composite adopted the natural and inexpensive BF as its core and the PANI as the shell. Fourier transform infrared spectra suggest significant interactions between the BF and PANI shell, and a high degree of doping in the PANI shell was achieved. X-ray diffraction results reveal that the crystallization of the PANI shell was improved. The dielectric behaviors are analyzed with respect to dielectric constant, loss tangent, and Cole-Cole plots. The BF/PANI composite exhibits superior electrical conductivity (2.01 ± 0.29 S·cm-1), which is higher than that of the pristine PANI with 1.35 ± 0.15 S·cm-1. The complex permittivity, electromagnetic interference (EMI), shielding effectiveness (SE) values, and attenuation constants of the BF/PANI composite were larger than those of the pristine PANI. The EMI shielding mechanisms of the composite were experimentally and theoretically analyzed. The absorption-dominated total EMI SE of 28.8 dB at a thickness of 0.4 mm indicates the usefulness of the composite for electromagnetic shielding. Moreover, detailed comparison of electrical and EMI shielding properties with respect to the BF/PANI, dedoped BF/PANI composite, and the pristine PANI indicate that the enhancement of electromagnetic properties for the BF/PANI composite was due to the improved conductivity and the core-shell architecture. Thus, the composite has potential commercial applications for high-performance electromagnetic shielding materials and also could be used as a conductive filler to endow polymers with electromagnetic shielding ability.