Graphyne Nanoribbons Research Articles

Compensation temperature and hysteresis behaviors of the ferrimagnetic bilayer zigzag graphyne nanoribbon with RKKY interaction

In this study, a bilayer zigzag graphyne nanoribbon with RKKY interaction is described using a ferrimagnetic mixed-spin (2, 5/2) Ising model. The compensation behaviors and hysteresis characteristics of the system generated by various physical parameters, such as crystal fields of sublattices, interlayer exchange coupling and the intralayer exchange coupling are explored using Monte Carlo simulation. In the research results, we found that among the 30 possible spin configurations that may occur in the ground state of the system, only 21 spin configurations are stable. At the same time, under certain parameters, the system exhibit interesting behaviors such as compensation phenomena and multi-loop hysteresis. This can provide a theoretical reference for multi-state magnetic recording.

Reduced reverse degree-based topological indices of graphyne and graphdiyne nanoribbons with applications in chemical analysis

Graphyne and Graphdiyne Nanoribbons reveal significant prospective with diverse applications. In electronics, they propose unique electronic properties for high-performance nanoscale devices, while in catalysis, their excellent surface area and reactivity sort them valuable catalyst supports for numerous chemical reactions, contributing to progresses in sustainable energy and environmental remediation. The topological indices (TIs) are numerical invariants that provide important information about the molecular topology of a given molecular graph. These indices are essential in QSAR/QSPR analysis and play a significant role in predicting various physico-chemical characteristics. In this article, we present a formula for computing reduced reverse (RR) degree-based topological indices for graphyne and graphdiyne nanoribbons, including the RR Zagreb indices, RR hyper-Zagreb indices, RR forgotten index, RR atom bond connectivity index, and RR Geometric-arithmetic index. We also execute a graph-theoretical analysis and comparison to demonstrate the critical significance and validate the acquired results. Our findings provide insights into the structural and chemical properties of these nanoribbons and contribute to the development of new materials for various applications.

Graphyne and graphdiyne nanoribbons: from their structures and properties to potential applications.

Graphyne (GY) and graphdiyne (GDY) have properties including unique sp- and sp2-hybrid carbon atomic structures, natural non-zero band gaps, and highly conjugated π electrons. GY and GDY have good application prospects in many fields, including catalysis, solar cells, sensors, and modulators. Under the influence of the boundary effect and quantum size effect, quasi-one-dimensional graphyne nanoribbons (GYNRs) and graphdiyne nanoribbons (GDYNRs) show novel physical properties. The various structures available give GYNRs and GDYNRs greater band structure and electronic properties, and their excellent physical and chemical properties differ from those of two-dimensional GY and GDY. However, the development of GYNRs and GDYNRs still faces problems, including issues with accurate synthesis, advanced structural characterization, the structure-performance correlation of materials, and potential applications. In this review, the structures and physical properties of quasi-one-dimensional GYNRs and GDYNRs are reviewed, their advantages and disadvantages are summarized, and their potential applications are highlighted. This review provides a meaningful basis and research foundation for the design and development of high-performance materials and devices based on GYNRs and GDYNRs in the field of energy.

Hybrid scheme of DFT and machine learning to accelerate the design of graphyne nanoribbons as electrocatalysts for the ORR and HER

Recently, graphyne and its family members (GYFs) have emerged as promising carbon-based metal-free catalysts (CMFCs) for the oxygen reduction reaction (ORR) and hydrogen evolution reaction (HER). Herein, we performed density functional theory simulations to explore the ORR and HER performances of β-graphyne/graphdiyne nanoribbons (βGyNRs/βGDyNRs), which have received scant attention. Our results reveal that βGyNRs/βGDyNRs are excellent bifunctional CMFCs after functionalization by manipulating the edge shape or N-doping. Moreover, we verified the role of the binding strength of the H atom (ΔEH*) as a universal descriptor for predicting the bifunctional activities for the ORR and HER on GYFs. We also proposed a machine learning model based on an extreme gradient boosting algorithm for predicting the bifunctional activities of GYFs. Feature importance analysis indicated that the atomic charge of the catalytic site (Q) played a determining role in the ORR activity of the GYFs. This study not only identifies promising GYFs, but also accelerates the search for highly active GYFs for the ORR and HER.

On the molecular structure modelling of gamma graphyne and armchair graphyne nanoribbon via reverse degree-based topological indices

ABSTRACT Reverse degree-based topological indices (RDTIs) are applied to analyze the structural properties of molecules such as gamma graphyne and armchair graphyne nanoribbons. RDTIs provide valuable information about the connectivity patterns of atoms within a molecule, aiding in understanding its chemical and physical properties. For gamma graphyne and armchair graphyne nanoribbons, RDTIs would involve calculating the contributions from various atom pairs based on the degree differences between them. These indices consider the reverse order in which degrees are subtracted. RDTIs capture important aspects of molecular structure, including branching, degree distribution, and connectivity. Using RDTIs, one can assess the complexity, stability, and other characteristics of gamma graphyne and armchair graphyne nanoribbons. This paper focus on two structures made from hexagonal honeycomb graphite lattices, like gamma graphyne, and armchair graphyne nanoribbons. The methodology used in this study is First and second reverse Gourava indices, hyper first and second reverse Gourava indices, reverse multiplicative sum connectivity Gourava index, and reverse multiplicative product connectivity Gourava. Furthermore, these indices play a vital role in quantitative structure–property relationships and offer insights into the behaviour and reactivity of these unique molecular structures. Further research and computational analysis of RDTIs will deepen our understanding of these fascinating carbon-based materials.

Spin-resolved transport of multifunctional C18 molecule-based nanodevices: a first-principles study

As is well known, Kasier et al first synthesized a cyclic molecule C18, as characterized by high-resolution atomic force microscopy, is a polyalkylene structure in which the 18 carbon atoms are linked by alternating single and triple bonds Kaiser et al (2019 Science 365 1299–301). Early studies have found that the C18 molecule has semiconducting properties, suggesting that a similar straight-chain carbon structure could become a molecular device. Inspired by this, an analysis of spin-resolved electronic transport of nanodevices made by C18 sandwiched between zigzag graphyne nanoribbon leads or zigzag graphene nanoribbon leads presents here. The computational results demonstrate that a good spin-filtering effect, spin rectifying effect and an obvious negative differential resistance behavior in designed model devices can be obtained. Moreover, a stable dual-spin filtering effect or diode effect can be occurred in considered model devices with leads in an antiparallel state. The intrinsic mechanisms of molecular nanodevices are explained in detail by analyzing the transmission spectrum under different bias voltage, local density of states, molecular projection Hamiltonian, Current–Voltage (I–V) characteristics, transmission pathways, et al. These results are particularly significant for the development of multifunctional spintronic nanodevices.

Compensation behaviors and magnetic properties of an ising-type bilayer graphyne nanoribbon

In this work, we employ Monte Carlo method to examine the compensation behaviors and magnetic properties of an Ising-type bilayer graphyne nanoribbon. Consideration is given to how the magnetic characteristics of the system are affected by the length of the graphyne nanoribbon and the number of Monte Carlo steps. The influence of different parameters such as exchange coupling, crystal field, temperature and external magnetic field on the studied system are investigated. It is presented that the system can show the interesting behaviors such as double compensation points and multi-loop hysteresis behaviors under certain parameters. These may offer theoretical reference for multi-state magnetic recording.

Computation of some important degree-based topological indices for γ- graphyne and Zigzag graphyne nanoribbon

Topological indices serve as mathematical tools for characterising the molecular structure of a compound, and are useful to anticipate its properties. Actually, these are quantitative measures that can provide valuable information regarding the structure of a molecule, such as its connectivity and symmetry. By analysing these indices, researchers can make predictions about the behaviour of the molecule, such as its reactivity, solubility, and toxicity, among others. The γ-Graphyne is a fascinating carbon allotrope that has recently gained significant attention due to its unique electronic, optical, and mechanical properties. As a result, there has been increasing interest in exploring its potential applications in various fields of science and technology. The molecular descriptors for the characterisation of γ-Graphyne have not yet been investigated. Therefore, it is of much importance to predict its molecular topology to well understand the physicochemical properties. In this work, a graph theory-based edge partitioning technique is used to model the molecular topology of γ-Graphyne and Zigzag graphyne nanoribbon, and mathematical closed-form expressions for some of its essential degree-based molecular descriptors are derived. These computed indices have been illustrated with the help of graphical representations and numerical tables.

On degree-based topological descriptors of graphyne and graphdiyne nanoribbons

On degree-based topological descriptors of graphyne and graphdiyne nanoribbons

Spin Properties and Metal-Semiconductor Transition of Nitrogen-Containing Zigzag Graphyne Nanoribbon Caused by Magnetic Atom Doping

In this study, the density function theory (DFT) was used to study the influence of the magnetic atoms (Fe, Co, Ni) doping on the electrical properties of nitrogen-containing zigzag graphyne-like nanoribbon (N-ZGyNR). The results show that, by doping different atoms into the natural “holes” of N-ZGyNR, the changes in the structure, magnetic moment distribution and electrical properties of N-ZGyNR are different. Due to the incomplete saturation of the edge C atoms, the initial N-ZGyNR presents metallicity and spin degeneracy. The doping of Fe atoms will cause the C-C bond in N-ZGyNR to be completely broken, resulting in structural distortion, and about 0.8e- will transfer from Fe to N-ZGyNR. Compared with Fe doping, Co/Ni doping has a smaller effect on the N-ZGyNR and will not cause structural distortion, but will redistribute the spin charge in N-ZGyNR, thereby forming a band gap of 60 meV near the Fermi level to realize the transition of metal-semiconductor. The above results show that the electrical properties of N-ZGyNR can be controlled by magnetic atom doping, and the metal-semiconductor transition can be realized by Co/Ni doping, which provides a new alternative for spintronic devices.

Perfect spin Seebeck effect, spin-valve, spin-filter and spin-rectification based on the heterojunction of sawtooth graphene and graphyne nanoribbons.

In order to develop low-power-consumption electronic devices, we studied a heterojunction composed of a 5,4-sawtooth graphene nanoribbon and 6,6,12-graphyne nanoribbon by using first-principles calculations combined with the non-equilibrium Green's function approach. Some spin caloritronic and spintronic devices can be realized based on the heterojunction, exhibiting excellent and multifunctional properties: a net spin current and perfect spin Seebeck effect are generated, a thermal induced and bias induced colossal magnetoresistance is obtained, and a spin filter with 100% spin polarization and a spin rectification with a high rectification ratio are acquired. Our results indicate that the proposed heterojunction is a promising candidate for multi-effect and low-power-consumption electronic devices.

The electronic properties of non-conventional α-graphyne nanoribbons.

Graphyne nanocarbons are composed of a mixture of sp and sp2 hybridized atoms in different ratios and distributions. In addition to pure hexagonal systems, non-conventional graphynic structures can also accommodate non-hexagonal rings, as proposed recently on the basis of previously studied haeckelites. Here we use computational simulations to investigate the electronic properties emerging from quantum confinement when such 2D systems are cast into different families of nanoribbons. We show that the electronic behavior of these ribbons closely follow those of their 2D counterparts. However, we find that part of these quasi-1D systems become semiconductors due to the emergence of spin-polarized states at their edges. We further investigate how such multiple spin-configurations influence the electronic transport properties of nanojunctions involving these non-conventional graphyne nanoribbons. These findings highlight how details of these graphyne nanoribbons' atomic structure can be used to tune their electronic properties for targeted applications in nanoelectronics.

Exploring the enhancement of the thermoelectric properties of bilayer graphyne nanoribbons

The electronic and thermoelectric properties of bilayer α-graphyne nanoribbons are investigated using density functional theory and the NEGF method. The power factor (σS2) is increased for the bilayer nanoribbons in comparison with isolated ribbons.

Modulating the spin-dependent electronic structures and transport properties of zigzag $$\upalpha $$-2 graphyne nanoribbons by boron doping

We investigated the electronic structure and spin-dependent transport properties of zigzag $$\upalpha $$ -2 graphyne nanoribbons (Z $$\upalpha $$ -2GYNRs) with boron (B) atomic doping by using first-principle non-equilibrium Green’s function method. We observed a spin-polarized semi-metallic electronic structure with an acetylenic (sp hybridized) carbon at the edge which is substituted by boron. We also calculated the spin-dependent transport properties and observed both unidirectional and bidirectional spin-filtering effects. Our results demonstrated boron substitution as an effective method for modulating the spin-dependent electronic property of the Z $$\upalpha $$ -2GYNRs. This work would provide a new scheme for designing graphyne-based spintronics devices.

Improving the thermoelectric properties of graphene through zigzag graphene–graphyne nanoribbon heterostructures

Thermoelectric materials can convert thermal energy and electrical energy into each other, which have attracted extensive attention in recent years. In this paper, we systematically investigate the ballistic thermoelectric performance of four zigzag graphene–graphyne nanoribbon heterostructures M $$i(i=1{-}4)$$ through utilizing non-equilibrium Green’s function method. Our results show that heterostructures possess superior thermoelectric properties with respect to pristine graphene nanoribbon. Especially, the ZT value of M4 reaches 1.5 at 700 K, which is about 15 times that of graphene. Such improvement mainly originates from the reduction of phononic and electronic thermal conductance and the increase of Seebeck coefficient. Meanwhile, because M4 has the lowest phonon thermal conductance and favorable thermal power, its thermoelectric figure of merit is the best. These findings in this paper demonstrate that heterostructure is a viable approach to optimize the thermoelectric performance of graphene, which provides useful guidance for the design and fabrication of nanoscale thermoelectric devices.

Effect of vacancy defects on transport properties of α-armchair graphyne nanoribbons

The effect of vacancy defects on electrons transport behavior of the alpha-armchair graphyne nanoribbons has been studied by density-functional tight-binding and non-equilibrium Green’s function methods. Three different widths of the nanoribbons with 6, 7 and 8 atoms and four types of vacancy defects contain one, two, three and four missing atoms were selected in this study. In relaxed structures, the structural changes around the defects are observed. Some of the free hands form new atomic chains containing 6 or 7 atoms. Comparing with perfect devices, the current decreases at the defective devices with 8 atoms width, whereas, it increases for devices with 6 atoms width. By calculating the density of states, transmission spectrums and molecular energy spectrums for devices with 6-atoms widths, there is a resonance state for DDOS and T(E) peaks in the QV device, while the peak of the density of states and transmission spectrums does not match in the SV1 device. Also, the results show that HOMO-LUMO gap energy in the SV1 device is much more than the perfect and QV devices. For devices with 8 atoms width, the transmission spectrums are reduced for all defects due to the lower density of the energy level of molecular energy. However, the orbital distribution of LUMO state in the device with the defect is localized but for the perfect structure, both the LUMO and the HOMO orbital distribution are quite delocalized.

Interesting Odd–Even Effect, Ohmic Contact, Negative Differential Resistance, and Current Stabilizer Behavior in All-Carbon Graphyne/Carbon-Chain Junctions

A new and simple kind of all-carbon junction nanodevice, which is free of metal electrodes, is constructed by carbon chains seamlessly connected to two graphyne nanoribbons (GYNRs) electrodes. The electron transport properties of the constructed nanodevices are systematically investigated using self-consistent charge density-functional tight-binding combined with nonequilibrium Green’s function (NEGF) formalism. The effects of contact type and contact position on the electron transport properties of these devices are discussed. The calculated results show that the electron transport properties can be well modulated by the contact geometry of the carbon chain. In GYNRs connected by both horizontal and tilted single-carbon chain, an evident even–odd behavior of conductivity is observed. In addition, the linear, monotonous currents in a wide bias voltage range show good Ohmic contact. The negative differential resistance also appears under both positive and reverse bias voltages, indicating applications in bidirectional tunnel diodes. Comprehensive analyses of the physical mechanisms for the odd–even behavior are given. Remarkably, in GYNRs connected by double-carbon chains, a noticeable current stabilizer behavior occurs, suggesting that the graphyne nanodevices contacted with double-carbon chains can be used as a current stabilizer in circuits. This article provides valuable insight into all-carbon functional nanodevices.

Highly spin polarized transport in γ-zigzag graphyne nanoribbon junctions

Using density functional calculations combined with non-equilibrium Green’s functions, we investigate the BN co-doping effects on the electronic structure of zigzag γ -graphyne nanoribbons and spin-dependent transport properties of related transport heterojunctions. The results show that, when properly selecting the doping sites of the B and N atoms at the two edges, half-metallicity is obtained due to the opposite energy shift in the two spin channels caused by the potential generated by the BN pairs. In transport junctions constructed by connecting two ribbons by only one edge of each ribbon to form a ‘Z’-shape structure, highly spin polarized transport is achievable, depending on the relative positions of the B and N dopants in the two ribbons. Our finding opens a new possibility of graphyne in spintronic device applications.

Weighted Mostar indices as measures of molecular peripheral shapes with applications to graphene, graphyne and graphdiyne nanoribbons

ABSTRACTIn this study we consider relatively new bond-additive Mostar indices that appear to provide quantitative measures of peripheral shapes of molecules. We have computed weighted Mostar, edge-Mostar and total-Mostar indices of graphene, -types of graphyne and graphdiyne, which are of considerable interest owing to their novel properties and thus find applications in a number of areas such as sensors, catalysis, chemisorption and nanomedicine. We have implemented the results to analyse the weighted Mostar indices and have obtained exact analytical expressions for the title molecules. We propose that Mostar indices together with frontier molecular orbitals, and HOMO–LUMO gaps can provide measures of chemical reactivity and analysis of peripheral molecular shapes.

Spin multiple functional devices in zigzag-edged graphyne nanoribbons based molecular nanojunctions

Graphyne, a two-dimensional carbon allotrope being proven to possess amazing electronic properties as graphene, have been successively proposed in theory and experiment. Here, the electronic band structures of zigzag-edged δ graphyne nanoribbons (ZδGYNR) and zigzag-edged γ graphyne nanoribbons (ZγGYNR) have been revealed with a metallic behavior in non-magnetic state, a metallic spin splitting in ferromagnetic state and a spin degeneracy with a direct band gap in antiferromagnetic state, which is much similar to zigzag-edged graphene case. We also report a comprehensive study of the intrinsic spin-resolved transport properties for the three junctions with a carbon chain sandwiching between ZδGYNR/ZγGYNR leads by using density functional theory coupled with the non-equilibrium Green’s function method. The results reveal that the designed junctions perform multiple functions with wonderful spin filtering, rectification, and a spin negative differential resistance(SNDR) effect, and so on. Specifically, the spin filtering efficiency approximate 100% within a large bias range, the maximum rectification ratio can be up to 1.5×104 and an obvious SNDR with the maximum peak to valley ratio up to 9.10×103 can also be found. The GYNR-based multiple functional device is demonstrated, and mechanisms are proposed for the above phenomena.