Electrically conductive porous metal-organic frameworks (MOFs) exhibit a huge potential in a broad range of applications. However, how to endow MOFs with appropriate electrical conductivity remains a ...challenge. In this paper, we report a controllable growth of polypyrrole (PPy) nanofibers in the nanochannels of MOFs to construct a kind of nanocomposites. We can also use this strategy to directly demonstrate the straight nanochannel structure in MOFs. More importantly, the formed PPy/ZIFs nanocomposites show a highly tunable electrical conductivity as well as a tunable electromagnetic absorption (EMA) property. The maximal frequency width with absorbing higher than 90% of incident electromagnetic waves reaches 7.24 GHz, which is wider than those of most reported MOFs or conducting polymers based EMA materials. An electrical conductance loss and interfacial polarization relaxation are used to investigate the electromagnetic dissipation mechanism of theses PPy/ZIFs nanocomposites. It opens up the rational design of electrically conductive MOFs for excellent electromagnetic absorption.
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The design of novel hybrid nanostructures has been seen as an effective route to tune the properties of materials. Herein, we provide an in situ growth strategy to efficiently construct kebab-like ...hybrids, which are composed of one-dimensional SiC nanowires stringing polyhedral metal organic frameworks (MOFs). Through a heat-treatment process regardless of under air or argon, these hybrids generate an excellent electromagnetic absorption (EMA) ability. We comprehensively explored the growth and calcination process of these hybrids as well as their EMA enhanced mechanism. The results indicate that the MOFs kept as shrunken polyhedrons under air but decomposed to small particles under argon, due to the different calcination mechanism. In addition, the enhanced EMA ability should be attributed to the combined influences of the reduced dielectric constant, enlarged aspect ratio, and enhanced interface polarization. This research opens up the rational designs and applications of novel materials by the hybridizing of nanomaterials in multidimensions.
Electromagnetic (EM) pollution has raised significant concerns to human health with the rapid development of electronic devices and wireless information technologies, and created adverse effects on ...the normal operation of the sensitive electronic apparatus. Notably, the EM absorbers with either dielectric loss or magnetic loss can hardly perform efficient absorption, which thereby limits their applications in the coming 5G era. In such a context, the hotspot materials reported recently, such as graphene, MXenes, and metal-organic frameworks (MOF)-derived materials, etc., have been explored and applied as EM absorbing and shielding materials owing to their tunable heterostructures, as well as the facile incorporation of both dielectric and magnetic components. In this review, we deliver a comprehensive literature survey according to the types of EM absorbing and shielding materials, and interpret the connectivity and regularity among them on the basis of absorbing mechanisms and microstructures. Finally, the challenges and the future prospects of the EM dissipating materials are also discussed accordingly.
The authors describe the synthesis of carbon dots (CDs) that are highly doped with both nitrogen and phosphorus. Synthesis is accomplished via a hydrothermal reaction starting from ...diethylenetriaminepenta(methylenephosphonic acid) and m-phenylenediamine as the precursors. The high
N,P
-doping ratios renders the codoped CDs excellently water soluble, photostable over a wide range of pH values, and photostable in the presence of various metal ions. Ferric ions acts as a strong quencher of fluorescence. Their low cytotoxicity and strong green fluorescence (with excitation/emission peaks at 440/510 nm and a quantum yield of 0.32) make the CDs well suited for purposes of cell imaging, and this is demonstrated by fluorescent bioimaging of human lung carcinoma cells (type A549) and human breast cancer cells (type KB). Furthermore, the CDs were used as an effective probe for monitoring Fe(III) in both aqueous solution and living cells.
Graphical abstract
A highly
N,P
-codoped carbon dots (CDs) were synthesized for high-quality cellular Imaging and monitoring Fe
3+
in living cells. This water soluble CDs displayed high biocompatibility and emitted strong green fluorescence.
In this work, we successfully synthesize
N
-doped carbon nanoribbon (NCNR) from polypyrrole precursor and investigate their dielectric and microwaves absorption (MA) properties. NCNR appears as ...two-dimensional ribbon-like microstructure with tunable
N
-doping ratio. The dielectric property of NCNR can be tuned by
N
-doping content controlling. The results demonstrate that NCNR exhibits excellent MA performance at a filler-loading ratio of only 5 wt%. When the sample thickness is 3.3 mm, the maximal absorption reaches − 73.76 dB at 10.48 GHz. The maximum efficient bandwidth gets to 7.4 GHz (10.6–18 GHz), under a sample thickness of 2.7 mm. A model that refers to conductive loss, polarization relaxation, and impedance match is adopted to explain the MA mechanism of NCNR. This research opens up the exploration of NCNR in the field of MA, and provides a new idea for the design of carbon-related broad band MA materials.
Compared with chemically synthesized materials, biomass materials often exhibit unique intrinsic structures, which can be utilized through optimizing microstructures and activation process to furnish ...low-cost and efficient Microwave Absorption Materials. This research uses a common hydrophyte (
Cyperus malaccensis
Lam. var.
brevifolius
Bocklr) in South China as the raw material to fabricate carbon-based biomass-derived absorbers through one-step synthesis. The fabricated carbon materials show efficient Microwave Absorption (MA) performance with minimum reflection loss (RL
min
) of − 26.0 dB at 11.9 GHz from the sample pyrolyzed at 700 °C under the thickness of only 2 mm and wide effective absorption bandwidth of 4.6 GHz (11.6–16.2 GHz) from the sample annealed at 600 °C. Moreover, the effective MA bandwidth can cover the entire C to Ku band by tuning the thickness. A balance of dielectric loss mechanism and impedance matching is the reason why this biomass carbon-based absorber exhibits excellent MA performance. The results show that this biomass carbon has great potential to be low-cost, green and efficient carbon-based microwave absorbers.
Salecan is a novel water-soluble, high molecular mass extracellular β-glucan produced by Agrobacterium sp. ZX09. Salecan has excellent physicochemical and biological properties, making it very ...suitable for hydrogel preparation. In this study, a series of novel semi-interpenetrating polymer network (semi-IPN) hydrogels containing Salecan and poly(N,N-dimethylacrylamide-co-2-hydroxyethylmethacrylate) (poly(DMAA-co-HEMA)) were synthesized by radical polymerization and semi-IPN technology. Structure and morphology of the hydrogels were characterized by FTIR, XRD, TGA and SEM. The semi-IPNs had a well-interconnected porous structure with tunable pore size ranging from 6 to 41μm. Swelling capability of the hydrogels was improved by introducing the hydrophilic Salecan. Rheological results indicated that the incorporation of poly(DMAA-co-HEMA) into hydrogels enhanced the storage modulus. Compression tests revealed that these semi-IPNs were robust materials with compressive modulus between 13.3 and 90.5kPa, the addition of Salecan increased the fracture strain from 71.1% to 88.8%. Degradation and cytotoxicity tests demonstrated that semi-IPNs were degradable and non-toxic.
Amino functionalized zirconium-based metal–organic framework (NH
2
-UiO-66) and zinc-based zeolitic imidazolate framework (ZIF-8) were integrated to develop a core–shell architectured hybrid material ...(NH
2
-UiO-66@ZIF-8, NU66@Z8). The morphology and structure evolutions of core–shell NU6@Z8 were investigated by FE-SEM, XRD, FTIR, and XPS. The NU66@Z8 combined with carboxylated multi-walled carbon nanotubes (CMWCNT) was deposited on a glassy carbon electrode (GCE) for fabricating an electrochemical platform towards detecting Pb
2+
and Cu
2+
. The NU66@Z8/CMWCNT/GCE revealed significantly improved electrochemical performance for determination of Pb
2+
and Cu
2+
compared with the individual components, which can be attributed to the strong adsorption capacity, unique core–shell structure, and large electrochemical active surface area of NU66@Z8/CMWCNT. Under the optimal conditions, the developed sensor exhibited excellent sensing capability with a low limit of detection (Pb
2+
,1 nM; Cu
2+
, 10 nM) and a wide determination range (Pb
2+
,0.003–70 μM; Cu
2+
, 0.03–50 μM). The sensor showed high selectivity towards common interfering ions and good repeatability. The real sample recoveries of proposed sensor were in the range 95.0–103% for Pb
2+
(RSD ≤ 5.3%) and 94.2–106% for Cu
2+
(RSD ≤ 5.9%), suggesting that the NU66@Z8/CMWCNT is suitable for examining trace heavy metals in natural environment.
Graphical Abstract
A series of
N
-doped carbon nanotubes (NCNTs) have been synthesized via a temperature-controlled annealing of polypyrrole (PPy) hierarchical nanostructures. The microstructures, dielectric properties ...and microwaves response behavior of these NCNTs were systematically investigated. The results indicate that initial pyrrolic N in PPy was gradually converted into pyridinic and graphitic N during the annealing process. NCNT prepared at 700 °C exhibits excellent broadband microwave absorption performance, where its effective absorption bandwidth (reflection loss value lower than − 10 dB) reaches 8.20 GHz in the frequency range of 9.80–18.00 GHz. A model refers to conductive loss and polarization relaxation was adopted to explain the high-performance microwave absorption. This research greatly expands the development of
N
-doped CNTs for the application in microwave areas.
It is of great significance to regulate the dielectric parameters and microstructure of carbon materials by elemental doping in pursuing microwave absorption (MA) materials of high performance. In ...this work, the surface electronic structure of N-doped CNTs was tuned by boron doping, in which the MA performance of CNTs was improved under the synergistic action of B and N atoms. The B,N-doped carbon nanotubes (B,N-CNTs) exhibited excellent MA performance, where the value of minimum reflection loss was -40.04 dB, and the efficient absorption bandwidth reached 4.9 GHz (10.5-15.4 GHz). Appropriate conductance loss and multi-polarization loss provide the main contribution to the MA of B,N-CNTs. This study provides a novel method for the design of CNTs related MA materials.
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