Carbon nanotubes (CNTs) have been under scientific investigation for more than fifteen years because of their unique properties that predestine them for many potential applications. The field of nanotechnology and nanoscience push their investigation forward to produce CNTs with suitable parameters for future applications. It is evident that new approaches of their synthesis need to be developed and optimized. In this paper we review history, types, structure and especially the different synthesis methods for CNTs preparation including arc discharge, laser ablation and chemical vapour deposition. Moreover, we mention some rarely used ways of arc discharge deposition which involves arc discharge in liquid solutions in contrary to standard used deposition in a gas atmosphere. In addition, the methods for uniform vertically aligned CNTs synthesis using lithographic techniques for catalyst deposition as well as a method utilizing a nanoporous anodized aluminium oxide as a pattern for selective CNTs growth are reported too.

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Methods for carbon nanotubes synthesis—review

As elemental main group materials (i.e., silicon and germanium) have dominated the field of modern electronics, their monolayer 2D analogues have shown great promise for next-generation electronic materials as well as potential game-changing properties for optoelectronics, energy, and beyond. These atomically thin materials composed of single atomic variants of group III through group VI elements on the periodic table have already demonstrated exciting properties such as near-room-temperature topological insulation in bismuthene, extremely high electron mobilities in phosphorene and silicone, and substantial Li-ion storage capability in borophene. Isolation of these materials within the postgraphene era began with silicene in 2010 and quickly progressed to the experimental identification or theoretical prediction of 15 of the 18 main group elements existing as solids at standard pressure and temperatures. This review first focuses on the significance of defects/functionalization, discussion of different allotropes, and overarching structure-property relationships of 2D main group elemental materials. Then, a complete review of emerging applications in electronics, sensing, spintronics, plasmonics, photodetectors, ultrafast lasers, batteries, supercapacitors, and thermoelectrics is presented by application type, including detailed descriptions of how the material properties may be tailored toward each specific application.

Emerging Applications of Elemental 2D Materials

Recent advances in hybrid organic-inorganic materials with spatial architecture for state-of-the-art applications

Green synthesis of nitrogen, sulfur-co-doped worm-like hierarchical porous carbon derived from ginger for outstanding supercapacitor performance

Chemical vapor deposition (CVD) has been used historically for the fabrication of thin films composed of inorganic materials. But the advent of specialized techniques such as plasma-enhanced chemical vapor deposition (PECVD) has extended this deposition technique to various monomers. More specifically, the deposition of polymers of responsive materials, biocompatible polymers, and biomaterials has made PECVD attractive for the integration of biotic and abiotic systems. This review focuses on the mechanisms of thin-film growth using low-pressure PECVD and current applications of classic PECVD thin films of organic and inorganic materials in biological environments. The last part of the review explores the novel application of low-pressure PECVD in the deposition of biological materials.

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Exploration of Plasma-Enhanced Chemical Vapor Deposition as a Method for Thin-Film Fabrication with Biological Applications

We explore the stability, electronic properties, and quantum capacitance of doped/co-doped graphene with B, N, P, and S atoms based on first-principles methods. B, N, P, and S atoms are strongly bonded with graphene, and all of the relaxed systems exhibit metallic behavior. While graphene with high surface area can enhance the double-layer capacitance, its low quantum capacitance limits its application in supercapacitors. This is a direct result of the limited density of states near the Dirac point in pristine graphene. We find that the triple N and S doping with single vacancy exhibits a relatively stable structure and high quantum capacitance. It is proposed that they could be used as ideal electrode materials for symmetry supercapacitors. The advantages of some co-doped graphene systems have been demonstrated by calculating quantum capacitance. We find that the N/S and N/P co-doped graphene with single vacancy is suitable for asymmetric supercapacitors. The enhanced quantum capacitance contributes to the formation of localized states near the Dirac point and/or Fermi-level shifts by introducing the dopant and vacancy complex.

Improving the Quantum Capacitance of Graphene-Based Supercapacitors by the Doping and Co-Doping: First-Principles Calculations.

Silicene with a buckled atomic layer has double surfaces with a high surface/volume ratio similar to nanocarbon materials and is expected to have potential applications for supercapacitors. With first-principles calculations, it is found that introduction of vacancy defects with the doping in silicene can enhance the quantum capacitance of silicene-based electrodes. The enhancement of quantum capacitance is attributed to the presence of localized states around the Fermi level. Furthermore, the quantum capacitance is observed to increase with the increase of the defect’s concentration. It is also observed that the localized states around the Fermi level lead to spin polarization in the cases of B-doping and S-doping near the vacancies.

Quantum Capacitance of Silicene-Based Electrodes from First-Principles Calculations

Using first-principle calculations, we studied the interaction between Li and graphene by considering two kinds of models, which are related to the configurations of Li adsorption and the concentration of Li on graphene. In a low concentration, the 2s state of Li is fully unoccupied due to charge transfer. With the increase of Li concentration, the 2s state is broadened and occupied partly by electrons. With a high concentration, such as Li : C = 1 : 6, Li cluster adsorption seems to become popular by the free formation energy of clusters with thermal effects.

Density functional theory study of Li binding to graphene

Co-seismic landslide mapping after earthquake event is essential for emergency rescue, geohazard prevention, and post-disaster reconstruction. Most co-seismic landslide mapping is primarily achieved via field surveys or visual interpretation of remote sensing images. However, such methods are highly labor-intensive and time-consuming, particularly over large areas. This paper proposed an automated co-seismic landslide mapping approach, which has three main advantages compared to state-of-the-art methods. First, it removes the dependence on the manual labeling for training samples through an unsupervised change detection process. Second, the approach takes the lead in introducing multi-scale extended morphological profiles to comprehensively describe the characteristics of various landslides induced by earthquake. Third, it is also the first attempt to employ ensemble strategy in landslide identification, which integrates the advantages of different machine learning-based classifiers, further improving the accuracy of recognition. Three experiments were carried out through multi-temporal Sentinel-2 and PlanetScope images acquired in China and Haiti. The results demonstrated the effectiveness and superiority of the proposed approach compared to other methods, providing an effective solution for complicated co-seismic landslide mapping task in the future. 

Change detection-based co-seismic landslide mapping through extended morphological profiles and ensemble strategy

Germanene with folded atomic layers has double surfaces and high surface/volume ratio, similar to carbon nanomaterials, and is expected to be used in supercapacitors and field effect transistors. B...

Qiang Xu

Papers

Improving the Quantum Capacitance of Graphene-Based Supercapacitors by the Doping and Co-Doping: First-Principles Calculations.

Quantum Capacitance of Silicene-Based Electrodes from First-Principles Calculations

Density functional theory study of Li binding to graphene

Change detection-based co-seismic landslide mapping through extended morphological profiles and ensemble strategy

First-Principles Calculation of Optimizing the Performance of Germanene-Based Supercapacitors by Vacancies and Metal Atoms