Renaissance of One‐Dimensional Nanomaterials

In the early 1990s, following the discovery of carbon nanotubes (CNTs), many types of 1D nanomaterials including nanotubes, nanowires, nanorods, and nanobelts were prepared and investigated. Generally speaking, the development of 1D nanomaterials could be divided into two stages based on the well-known review paper by Profs. Yang and Xia in 2003 in Advanced Materials. For 15 years since the 1990s, research on 1D nanowires attained continuous prosperity and their unique electrical, optical, and thermal transport properties were extensively explored. Countless famous scientists have made outstanding contributions, and Prof. Sishen Xie from the Institute of Physics, Chinese Academy of Sciences, is one of the important pioneers. Since 1992, Prof. Xie has focused on the synthesis, structure, mechanical, thermal, optical, and transport properties of 1D and other nanomaterials. A series of breakthrough advances have been made in the preparation, structure, and physical properties of aligned CNTs. High density and high purity aligned CNT arrays were prepared, which was a landmark to realizing precise control over the diameter and orientation of CNTs and solved the problems of chaotic tendency, entanglement, and inclusion in the sintered bundles of CNTs obtained by conventional methods.[1] Large-area and discrete ultra-long CNT arrays were successfully fabricated, where the diameter of the obtained carbon nanotube was uniform and the length was up to 2 mm via the improved process of CNTs arrays.[2] Furthermore, the world's narrowest CNTs with a diameter close to the theoretical limit were successfully synthesized.[3] Meanwhile, Chinese scientists have achieved a series of important scientific findings in the field of 1D nanomaterials, and the overall strength of China has been at the forefront of the world. However, the study of 1D nanomaterials experienced somewhat of a downturn from 2003, partially due to research attention switching to the discovery of graphene and other 2D nanomaterials. Excitingly, thanks to the interdisciplinary efforts intersected by materials, chemistry, physics, information and biology, the development of 1D nanomaterials has been revitalized. Distinct from simple investigation of the structure–performance correlation, current research is focused on the integration of 1D nanomaterials into functional devices. For instance, CNTs are employed as both interconnects and functional units in the construction of next generation carbon-based computers; nanowire arrays are adopted into flexible electronic or energy devices; and 1D nanomaterials are used as tiny probes to delivery drugs, biomolecules, and even vaccines into living cells. Therefore, summarizing the state-of-the-art progress of 1D nanomaterials and future trends is of great significance for realizing the renaissance and practical application of 1D nanomaterials. On the occasion of the 80th birthday of Prof. Sishen Xie, we organized the International Symposium on One-Dimensional Nanomaterials and were able to bring together some of the most eminent scientists to share their knowledge and experiences, which was of great importance to boost the development of 1D nanomaterials. Then, we proposed this special issue in Advanced Functional Materials based on selected presentations at the symposium and invited submissions from world-renowned research groups in this field. This issue consists of 13 Research Articles, 6 Reviews and 1 Perspective, covering important aspects in the research of 1D nanomaterials from the fundamental research point of view to the practical applications. As the most important 1D nanomaterial, CNTs have been extensively explored from syntheses to properties and applications. Due to the tradeoff between controlled synthesis and mass production, there has been a long bottleneck period in both the science and engineering of CNTs. The advances in precise structure control and assembly towards the CNT industry is summarized by Zhu, Qian, Wei, and co-workers (article number 2109401). They focus on the morphological manipulation and technical routes towards CNT industrialization. Hou, Liu, Cheng, and co-workers comprehensively review state-of-the-art progress on the controlled growth of CNTs by floating catalyst chemical vapor deposition (FCCVD), which have a defined number of walls, controlled diameter, bundle size, and type of conductivity (article number 2108541). The properties and possible applications of CNTs and their hybrids are summarized. Zhang, Kauppinen, Jeon, and co-workers report production of large- diameter double-walled CNT transparent conductive film (TCFs) via FCCVD, which overcomes the dilemma between performance and yield (article number 2103397). Its conductivity is comparable to the best-performing single-walled CNT (SWCNT) TCFs reported to date, but showing a production yield greater than two orders of magnitude. Moreover, the application of double-walled CNT TCFs in perovskite solar cells exhibits a high power conversion efficiency. High-density horizontally aligned SWCNT arrays with high-purity semiconducting tubes are promising materials for energy-efficient electronics. However, realizing high density and high semiconducting purity via a direct-growth method is still quite challenging. Qian, Zhang, and co-workers overcome the problem through a spatially confined approach based on floating solid catalyst chemical vapor deposition system (article number 2106643). SWCNT horizontal arrays with a high density and semiconducting purity are realized, which hold potential for future application in carbon-based electronics. The intersubband plasmons (ISBPs) of SWCNTs have attracted considerable attention because they endow SWCNT-based optoelectronic devices with more functions. Wei, Liu, Xie, and co-workers report the electronic type and diameter dependence of ISBPs of SWCNTs (article number 2107489). Based on the ISBP characteristics of different SWCNTs, high-performance SWCNT-based near-infrared electrochromic devices are fabricated by mixing small-diameter metallic SWCNTs with semiconducting SWCNTs due to their high conductivity and negligible ISBP signals. In addition to CNTs, graphene-based 1D nanomaterials have also been extensively studied. Graphene fiber, as a new member of carbonaceous fibers assembled by graphene sheets as component units, is deemed to exhibit remarkable performance in one dimension by inheriting the superior electrical, mechanical, and thermal properties of intrinsic graphene. Cheng, Liu, and co-workers design a dynamic Joule heating system for continuous synthesis of graphene fibers with ultrashort high-temperature treating time and low electric energy consumption (article number 2103493). Electrical and mechanical performances of as-fabricated graphene fibers are further improved in comparison with thermally annealed graphene fibers without current applying. Gong, Li, Zhang, and co-workers report a modulus-tailorable, stretchable, and biocompatible carbonene fiber for adaptive neural electrode (article number 2107360). The straight carbonene fiber shows an optimized Young's modulus, 154 GPa, excellent electrical conductivity, and satisified biocompatibility. This work proposes a novel strategy for assembling the tailorable and biocompatible carbonene electrode, which opens an avenue for designing the next-generation neural electrode. Recently, van der Waals heterostructures based on nanotubes have attracted extensive research interest. Lloyd-Hughes, Kauppinen, Maruyama, and co-workers investigate the intertube excitonic coupling in nanotube van der Waals heterostructures (article number 2104969). Charge transfer and dipole-dipole interaction thus play prominent roles in different timescales, which establish possibilities for the multi-functional use of these new nano-scale coaxial cables. Benefitting from the controlled growth of 1D nanomaterials, the design and construction of different types of functional devices has become realistic. 1D nanomaterials are widely used in the fields of electronics, photoelectrical devices, and energy conversion, due to their unique ability to connect the nanometer and macroscopic worlds. Aligned semiconducting carbon nanotube (A-CNT) films are expected to be an ideal channel material for constructing field-effect transistors (FETs) that outperform conventional transistors on wafer scale. Zhang, Peng, and co-workers report high-performance enhancement-mode (E-mode) FETs based on A-CNT films by systematically optimizing the channel material and CNT/high-k/metal gate stack (article number 2104539). Based on the high performance and uniform E-mode FETs, ring oscillators with stage numbers of 5, 7, 9, and 11 are fabricated with an optimized design and high yield, exhibiting a record propagation gate delay of 11.3 ps among CNT- and other nanomaterial-based ICs. Nonvolatile memories have attracted a lot of interest because they retain the data when the power is interrupted. Peng, Zhang, Li, Liu, Sun, and co-workers report a molecular wire made of seamless junctions between semiconducting SWCNT and partially unzipped segments of SWCNT (article number 2107224). This novel nanostructure is demonstrated to be a nonvolatile memory, which works at room temperature under atmospheric conditions. The smaller size of SWNT and high working temperature may lead to the development of molecular nanomagnets as nonvolatile memory devices for practical applications. Wei, Fan, Zhang, and co-workers develop a reconfigurable carbon nanotube barristor on the basis of a Schottky barrier CNT transistor (article number adfm.202107454). The CNT barristor brings new functions to CNT electronic devices and also opens up a new methodology for future reconfigurable device design. The detectors based on 1D nanomaterials have been continuously designed and constructed. The terahertz detectors based on carbon nanomaterials are reviewed by Zhao, He, and co-workers (article number 2107499). The fundamental principles of thermal, electronic, and photonic effects in carbon-based THz detection are thoroughly discussed, together with the detailed summary of the major progress in the past decades. 1D nanostructure arrays have excellent light-trapping properties due to the multiple reflection and refractive index gradient on the surface. Jie, Lee, Zhang, and co-workers report a photodetector with high sensitivity for ultraweak IR signals based on a conformal MoS2/silicon nanowire array heterojunction with an ultrathin Al2O3 interfacial passivation layer (article number 2108174). The photodetectors exhibit broadband photoresponse, low noise current, large responsivity, and high specific detectivity. 1D ZnO nanomaterials play a vital role in the construction of photoelectrical devices due to its easily modulated morphology and band structure. The precise preparation of 1D-ZnO and 1D-ZnO based heterostructures by traditional epitaxial growth and emerging van der Waals stacking is summarized by Zhao, Liao, Zhang, and co-workers (article number 2106887). The opportunities and challenges of interface engineering in 1D-ZnO based heterostructures for next-generation photoelectrical devices are presented. Impressively, semiconductor nanowires have shown favorable results in deciphering biological communications and translating this cellular language through the nanowire-based biointerfaces. Tian, Shi, and co-workers analyze the most recent developments of semiconductor nanowire-based biointerface technology (article number 2107997). The progress of functionalized nanowires in drug delivery and bioenergy production is summarized, and furthermore, the current limitations of nanowires and an outlook into the next generation of nanowire-based devices at biointerfaces are concluded. Developing efficient electrocatalysts with reduced noble metals loading or without noble metals is highly desirable. In the past decade, CNTs-based electrocatalysts have been proven to be efficient in many typical electrocatalytic reactions, and its strong structure operability and easy accessibility enable the utilization of related electrocatalysts to be sustainable. Thus, CNTs-based electrocatalysts is summarized by He, Ajayan, Ci, Song, and co-workers (article number 2106684). They outline the research progress in CNTs-based electrocatalysts that have been widely used in various electrochemical reactions. The challenges for shedding light on the very essence of the activity and the research perspectives are suggested. 1D nanowire arrays have the unique advantage of high specific surface area alongside their high length-diameter ratio, which makes them likely to be used in the field of electrocatalysis to develop high-performance catalysts. Qi, Xue, He, Li, and co-workers synthesize nanowire-structured heterogeneous MnCo2O4/graphdiyne arrays (NW-MnCo2O4/GDY) on the surface of 3D carbon cloth by using in-situ assembly and a coupling strategy (article number 2107179). The special core/shell-nanowire structure and synergistic interaction between the MnCo2O4 and GDY greatly improve the electric conductivity, facilitate mass/ion transport and gas emissions, and expose more active sites. Wu, Yang, Zhao, and co-workers develop a molecularly-dispersed cobalt phthalocyanine loaded on carbon nanotube for high-current long-term CO2 to CO electrolysis (article number 2107301). This work provides a triumphant approach to catalyze commercial-scale CO production using molecularly dispersed phthalocyanine electrocatalysts. Other works on nanomaterials-based energy conversion are also reported. The development of efficient alcohol oxidation reaction electrocatalysts with high mass activity, high durability, high Faradaic efficiency, and low overpotential is central for realizing practical alkaline direct alcohol fuel cells. Fu, Huang, Duan, and co-workers review the development of noble metal based electrocatalysts for alcohol oxidation reactions in alkaline media (article number 2106401). The strategies to enhance Faradaic efficiency and lower overpotential are discussed. A brief perspective on the key challenges and future opportunities is concluded. Wu, Zhang, Chen, and co-workers report the chemical design for both molecular and morphology optimization toward high-performance LIBs cathode material based on covalent organic framework (COFs) (article number 2107703). By introducing a flexible building unit containing sp3 N redox-active centers, a bipolar-type TP-TA COF assembled using uniform 2D hexagonal nanosheets is synthesized in a one-step reaction without any post-processing, achieving the much challenging simultaneous optimization of both molecular structure and morphology required for high performance electrode materials. Altogether, this special issue provides a platform for exchange between scholars in this field all over the world. It is of great significance to promote the future development of advanced functional materials, especially for 1D nanomaterials. During the preparation of this special issue, we have received great support from Dr. Emily Hu and the editorial team. We are greatly grateful for their help that makes this special issue possible. Last but not least, we are also greatly indebted to all authors for their significant contributions and enthusiastic support for this special issue. The authors declare no conflict of interest.

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