Nano Research

To achieve excellent electromagnetic wave (EMW) absorption properties, the microstructure design of the absorber is critical. In this work, six kinds of N-Ni/C nanostructures with different morphologies were prepared by one-step hydrothermal method and high temperature carbonization by adjusting the types of nickel salts and reaction solvents. The EMW absorption performance of six different morphologies of N-Ni/C nanostructures was compared and analyzed. Among them, it is found that the nanoflower-like N-Ni/C composite has excellent dielectric loss and magnetic loss synergistic effect due to its polycrystalline structure, and can obtain excellent EMW absorption performance. The minimum reflection loss value at a thickness of 1.9 mm is −59.56 dB at 16.88 GHz, and the effective absorption bandwidth value reaches 6.0 GHz at a thickness of 2.2 mm. Our research shows that different morphologies and multiple lattice structures of nanostructures with the same composition have a significant influence on EMW absorption performance, which provides new research ideas for developing high-performance EMW absorbing materials.

Enhancement of open-circuit voltage (Voc) is an effective way to improve power conversion efficiency (PCE) of the perovskite solar cells (PSCs). Theoretically, work function engineering of TiO2 electron transport layer can reduce both the loss of Voc and current hysteresis in PSCs. In this work, two-dimensional g-C3N4 nanosheets were adopted to modify the compact TiO2 layers in planar PSCs, which can finely tune the work function (WF) and further improve the energy level alignment at the interface to enhance the Voc and diminish the hysteresis. Meanwhile, the quality of perovskite films and charge transfer of the devices were improved by g-C3N4 nanosheets. Therefore, the PCE of the planar PSCs was champed to 19.55% without obvious hysteresis compared with the initial 15.81%, mainly owing to the remarkable improvement of VOC from 1.01 to 1.11 V. In addition, the stability of the devices was obviously improved. The results demonstrate an effective strategy of WF engineering to enhance Voc and diminish hysteresis phenomenon for improving the performance of PSCs.

It is an important goal for supramolecular chemistry to develop synthetic enzyme mimics rivaling native enzymes, while de novo fabrication of such mimics remains a challenge. Alternatively, the catalytic groups from the supramolecular complex can be integrated with the active sites of natural enzymes. Herein, we present a supramolecular catalytic hybrid that is self-assembled from oligohistidine-based peptides and a heme-dependent peroxidase. The results indicate that the peptides altered the enzyme conformation, promoted the transitions between the resting and the intermediate states of the heme, and increased the turnover rate of the enzyme by up to three-fold. We propose that the histidine residues from the peptides may collaborate with the groups in the natural heme pocket to accelerate the catalytic cycles of the enzyme. Our observations underline the advantages of the supramolecular approach and suggest that molecular self-assembly may combine with enzymes to provide a simple strategy to engineer the enzymatic active sites.

The extraordinary optical and electronic properties of anisotropic two-dimensional materials, such as black phosphorus, ReS2, and GeSe, enable them a promising component of polarization-sensitive photodetectors. However, these applications are significantly limited by the challenges of air-stability, response time, and linearly dichroic ratio. Interestingly, palladium diselenide (PdSe2) with high air stability is an emerging material that has robust in-plane anisotropy induced by its asymmetric pentagonal lattice structure. We have successfully prepared a few-layer PdSe2 using micromechanical exfoliation, and here we demonstrate the strong linear dichroism behavior of PdSe2 by polarization-resolved absorption spectra measurements. Such unique linear dichroism, endows the PdSe2 photodetector powerful ability to detect polarized light. The photodetector based on 5L PdSe2, as tested with polarization-dependent photocurrent mapping, exhibited competitive capability to detect polarized light, achieving a significant photocurrent on/off ratio (> 102), the quite fast response time (< 11 ms) and robust linearly dichroic ratios (/max//min ≈ 1.9 at 532 nm). These results are essential advance in the development of polarization-sensitive photodetector, a crucial step towards opening up a new avenue for the application of 2D optoelectronic devices.

Nanozymes have received great attention owing to the advantages of easy preparation and low cost. Unlike natural enzymes that readily adapt to physiological environments, artificial nanozymes are apt to passivate in complex clinical samples (e.g., serum), which may damage the catalytic capability and consequently limit the application in biomedical analysis. To conquer this problem, in this study, we fabricated novel nanozyme@DNA hydrogel architecture by incorporating nanozymes into a pure DNA hydrogel. Gold nanoparticles (AuNPs) were adopted as a model nanozyme. Results indicate that AuNPs incorporated in the DNA hydrogel retain their catalytic capability in serum as they are protected by the hydrogel, whereas AuNPs alone totally lose the catalytic capability in serum. The detection of hydrogen peroxide and glucose in serum based on the catalysis of the AuNPs@DNA hydrogel was achieved. The detection limit of each reaches 1.7 and 38 μM, respectively, which is equal to the value obtained using natural enzymes. Besides the mechanisms, some other advantages, such as recyclability and availability, have also been explored. This nanozyme@DNA hydrogel architecture may have a great potential for the utilization of nanozymes as well as the application of nanozymes for biomedical analysis in complex physiological samples.

Single-atom nanozyme (SAzyme) is the hot topic of the current nanozyme research. Its intrinsic properties, such as high activity, stability, and low cost, present great substitutes to natural enzymes. Moreover, its fundamental characteristics, i.e., maximized atom utilizations and well-defined geometric and electronic structures, lead to higher catalytic activities and specificity than traditional nanozymes. SAzymes have been applied in many biomedical areas, such as anti-tumor therapy, biosensing, antibiosis, and anti-oxidation therapy. Here, we will discuss a series of representative examples of SAzymes categorized by their biomedical applications in this review. In the end, we will address the future opportunities and challenges SAzymes facing in their designs and applications.

We present a facile and versatile method for introducing various non-precious metal nanoparticles (NPs) in small nanotubes, such as single-walled carbon nanotubes (SWNTs), including 3d-metals (V, Mn, Fe and Co), 4d-metals (Mo), and 5d-metals (W). This is realized by oxidizing encapsulated cycloalkene metal carbonyl complexes below their sublimation temperatures. This novel technique is significant because it avoids the diffusion and deposition of metal species on the outer walls of nanotubes, which has been challenging to achieve using the conventional filling methods. High-resolution transmission electron microscopy (HRTEM), high angle annular dark field scanning transmission electron microscopy (HAADF-STEM), energy-dispersive X-ray spectroscopy (EDX), Raman, and X-ray photoelectron spectroscopy (XPS) analyses revealed high filling efficiencies (> 95% SWNTs filled with metal NPs). This method also provides a unique approach to fabricate highly dispersed and uniform SWNT–metal nanoparticle encapsulates with lower valence states, which are often not stable in the bulk.