Theoretical investigation on optical properties of Möbius carbon nanobelts in one-and two-photon absorption

The first successful synthesis of fully fused and fully conjugated Möbius carbon nanobelts(CNBs)has attracted considerable attention.However,theoretical calculations based on suchπ-conjugated Möbius CNB are still insufficient.Herein,we theoretically investigated molecular spectroscopy of Möbius CNBs without and with n-butoxy groups via visualization methods.The results show that the presence of n-butoxy groups can significantly affect Möbius CNBs’optical performance,changing electron-hole coherence and enhancing two-photon absorption cross-sections.Our work provides a deeper understanding of photophysical mechanisms of Möbius CNBs in one-and two-photon absorption and reveals possible applications on optoelectronic devices.

Carbon Nanobelts:Brief History and Perspective

Carbon nanotubes(CNTs)are an emerging nanomaterial because of their outstanding performance in various applications.In recent years,the segment molecules of CNTs,referred to as carbon nanorings(CNRs)or carbon nanobelts(CNBs),have gained attention for their unique structures and properties,as well as their potential as seed molecules for the precise synthesis of CNTs.CNBs are rigid and thick segments of CNTs whose synthesis has been addressed by scientists fascinated by the uniqueness of CNBs long before the discovery of CNTs.After 60 years of efforts by synthetic chemists all over the world,the synthesis of the first CNB,(6,6)CNB,was achieved by our group in 2017.Since this milestone,diverse types of nanobelts have been synthesized through various synthetic routes,thereby demonstrating their photophysical,magnetic,and redox properties derived from rigid belt structures.The applications of CNBs have also been introduced recently.The formation of the host−guest complex,transformation to three-dimensional molecules,and measurement of conductivity have been reported for CNBs.This paper summarizes the brief history and perspective of CNBs.Further synthetic campaigns and aggressive application of CNBs would create novel and groundbreaking scenes in materials science.

Fabrication of N-doped carbon nanobelts from a polypyrrole tube by confined pyrolysis for supercapacitors

In this present work,N-doped carbon nanobelts(N-CNBs)were prepared by a confined-pyrolysis approach and the N-CNBs were derived from a polypyrrole(Ppy)tube coated with a compact silica layer.The silica layer provided a confined space for the Ppy pyrolysis,thereby hindering the rapid overflow of pyrolysis gas,which is the activator for the formation of carbonaceous materials.At the same time,the confined environment can activate the carbon shell to create a thin wall and strip the carbon tube into belt morphology.This process of confined pyrolysis realizes self-activation during the pyrolysis of Ppy to obtain the carbon nanobelts without adding any additional activator,which reduces pollution and preparation cost.In addition,this approach is simple to operate and avoids the disadvantages of other methods that consume time and materials.The as-prepared N-CNB shows cross-linked nanobelt morphology and a rich porous structure with a large specific surface area.As supercapacitor electrode materials,the N-CNB can present abundant active sites,and exhibits a specific capacitance of 246 F·g^(−1),and excellent ability with 95.44%retention after 10000 cycles.This indicates that the N-CNB is an ideal candidate as a supercapacitor electrode material.

From Amorphous Carbon to Carbon Nanobelts and Vertically Oriented Graphene Nanosheets Synthesized by Plasma-enhanced Chemical Vapor Deposition

Carbon materials with various structures were produced via plasma-enhanced chemical vapor deposition by controlling substrate temperature and mixed gases in the atmosphere. Scanning electron microscopy（SEM）, transmission electron microscopy（TEM）, high resolution transmission electron microscopy（HRTEM） and Raman spectroscopy were employed to investigate the morphology and structure of the materials. The results show that at a low substrate temperature（100 ~C） in CHa：Ar（flow rate ratio was 100 cm3/min：10 cm3/min）, amorphous carbon formed on Si（100） that could act as a support for the growth of carbon nanobelt and layer graphene at 800 ~C. Vertically oriented multi-layer graphene nanosheets（GNs） were catalyst-free synthesized on Si and Ni foam at 800 ~C in a mixture of CHa：Ar（20 cm3/min：60, 80 and 100 cm3/min）. The capacitor character investigated by cyclic voltammetry and galvanostatic charge/discharge indicates that for the as-synthesized GNs, the electrochemical capacitance is very small（16 F/g at current density of 16 A/g）. However, having been treated in acidic solution, the GNs exhibited good capacitive behavior, with a capacitance of 166 F/g, and after 800 charge/discharge cycles at 32 A/g, the capacitance could retain about 88.4%. The enhancement of specific capacitance is attributed to the increase of specific surface area after etching treatment of them.

Synthesis of a Hydrogenated Zigzag Carbon Nanobelt

Zigzag carbon nanobelts are a long-sought-after yet unrealized target for organic synthesis.Herein,we report a study toward the synthesis of tetrabenzo[10]cyclacene,an undocumented zigzag carbon nanobelt.The synthetic precursor of tetrabenzo[10]cyclacene is its box-shaped tetraepoxy derivative,which is synthesized through iterative Diels–Alder reactions utilizing a“C”-shaped building block.Attempted aromatization of this tetraepoxy nanobox toward the formation of a fully conjugated nanobelt results in an octahydro derivative of tetrabenzo[10]cyclacene.The structures of the tetraepoxy nanobox and octahydrotetrabenzo[10]cyclacene were both unambiguously identified with single-crystal X-ray crystallography.

Palladium Nanoparticles Loaded on Carbon Modified TiO_2 Nanobelts for Enhanced Methanol Electrooxidation

Carbon modified TiO_2 nanobelts(TiO_2-C) were synthesized using a hydrothermal growth method,as a support material for palladium(Pd) nanoparticles(Pd/TiO_2-C) to improve the electrocatalytic performance for methanol electrooxidation by comparison to Pd nanoparticles on bare TiO_2 nanobelts(Pd/TiO_2)and activated carbon(Pd/AC). Cyclic voltammetry characterization was conducted with respect to saturated calomel electrode(SCE) in an alkaline methanol solution, and the results indicate that the specific activity of Pd/TiO_2-C is 2.2 times that of Pd/AC and 1.5 times that of Pd/TiO_2. Chronoamperometry results revealed that the TiO_2-C support was comparable in stability to activated carbon, but possesses an enhanced current density for methanol oxidation at a potential of -0.2 V vs. SCE. The current study demonstrates the potential of Pd nanoparticle loaded on hierarchical TiO_2-C nanobelts for electrocatalytic applications such as fuel cells and batteries.

Synthesis and Electrochemical Behaviors of a-MoO_3 Nanobelts/Carbon Nanotubes Composites for Lithium Ion Batteries

α-MoO3 nanobelts/carbon nanotubes（CNTs） composites were synthesized by simple hydrothermal method followed by CNTs incorporating, and characterized by X-ray diffraction（XRD） and scanning electron microscopy（SEM）. Cyclic voltammogram（CV）, electrochemical impedance spectroscopy（EIS）, and galvanostatic charge/discharge testing techniques were employed to evaluate the electrochemical behaviors of α-MoO3 nanobelts/CNTs composites. The results exhibited that compared to bare α-MoO3 nanobelts, the α-MoO3 nanobelts/CNTs composites have better electrochemical performances as cathode materials for lithium ion battery, maintaining a reversible specific capacity of 222.2 mAh/g at 0.3 C after 50 cycles, and 74.1% retention of the first reversible capacity. In addition, the Rct value of the α-MoO3 nanobelts/CNTs is 13 Ω, much lower than 66 Ω of the bare α-MoO3 nanobelts. The better electrochemical performances of the α-MoO3 nanobelts/CNTs composites can be attributed to the effects of the high conductive CNTs network.

A ketone-functionalized aromatic saddle as a potential building block for negatively curved carbon nanobelts

A novel ketone-functionalized aromatic saddle consisting of 72 sp^2 carbon atoms is successfully synthesized and unambiguously identified with X-ray crystallography.It can,in principle,be used as a building block for synthesis of negatively curved carbon nanobelts and for a bottom-up approach to negatively curved carbon allotropes.

Synthetic Strategies of Carbon Nanobelts and Beyond

Carbon nanobelts(CNBs)with aesthetically appealing molecular structures and outstanding physical properties have attracted more and more attentions from the scientific community due to their potential applications in synthetic materials,host-guest chemistry,optoelectronics,and so on.The synthesis of CNBs at different stages was overviewed and some representative breakthroughs and advances in synthetic strategies were highlighted and discussed.The key issue for the synthesis of CNBs is how to construct curved structures with high strain energy.We not only proposed a few unconventional CNBs as the promising target molecules,but also pointed out the bottom-up synthesis of conjugated tubular segments of carbon nanotubes sharing similar properties as carbon nanotubes is the next focus in this emerging area.

Fe/MgO催化裂解甲烷制备碳纳米带

采用溶胶-凝胶法制备了Fe/MgO催化剂(E)。以甲烷为碳源,通过催化化学气相沉积法在E上生长出了碳纳米带(F),其结构和形貌经SEM和TEM表征。在最佳制备条件[E中Fe负载量为50%,甲烷流速70mL·min-1,于870℃反应1 h]下制备的F宽度约135 nm,厚约89 nm,长度在几十微米量级。

Preparation and Dielectric Properties of Nanostructured ZnO Whiskers

By a novel controlled combustion synthesis method, a large number of nanostructured ZnO whiskers with different morphologies, such as tetra-needles, long-leg tetra-needles and multi-needles, are prepared without any additive in open air at high temperature. The morphologies and crystalline structures of the as-prepared ZnO nanostructured whiskers are investigated by SEM and XRD. The possible growth mechanism on the nanostructured ZnO whiskers is proposed. The experimental results indicate that the dielectric constants and losses of the nanostructured ZnO whiskers are very low, demonstrating that the nanostructured ZnO whiskers are low-loss materials for microwave absorption in X-band. However, obvious microwave absorption in nanostructured ZnO whiskers is observed. The quasi-microantenna model may be attributed to the microwave absorption of the ZnO whiskers.