Investigation of NH 3 adsorption behavior on graphdiyne nanosheet and nanotubes: A first-principles study

A first principles study of RbSnCl3 perovskite toward NH3, SO2, and NO gas sensing

The sensitivity of a RbSnCl3 perovskite 2D layer toward NH3, SO2, and NO toxic gases has been studied via DFT analysis. The tri-atomic layer of RbSnCl3 possessed a tetragonal symmetry with a band gap of 1.433 eV. The adsorption energies of RbSnCl3 for NH3, SO2 and NO are -0.09, -0.43, and -0.56 eV respectively with a recovery time ranging from 3.4 × 10-8 to 3.5 ms. RbSnCl3 is highly sensitive toward SO2 and NO compared to NH3. The adsorption of SO2 and NO results in a significant structural deformation and a semiconductor-to-metal transition of RbSnCl3 perovskite. A high absorption coefficient (>103 cm-1), excessive optical conductivity (>1014 s-1), and a very low reflectivity (<3%) make RbSnCl3 a potential candidate for numerous optoelectronic applications. A significant shift in optical responses is observed through SO2 and NO adsorption, which can enable identification of the adsorbed gases. The studied characteristics signify that RbSnCl3 can be a potential candidate for SO2 and NO detection.

Boosting thermophilic anaerobic digestion with conductive materials: Current outlook and future prospects

Thermophilic anaerobic digestion (TAD) can provide superior process kinetics, higher methane yields, and more pathogen destruction than mesophilic anaerobic digestion (MAD). However, the broader application of TAD is still very limited, mainly due to process instabilities such as the accumulation of volatile fatty acids and ammonia inhibition in the digesters. An emerging technique to overcome the process disturbances in TAD and enhance the methane production rate is to add conductive materials (CMs) to the digester. Recent studies have revealed that CMs can promote direct interspecies electron transfer (DIET) among the microbial community, increasing the TAD performance. CMs exhibited a high potential for alleviating the accumulation of volatile fatty acids and inhibition caused by high ammonia levels. However, the types, properties, sources, and dosage of CMs can influence the process outcomes significantly, along with other process parameters such as the organic loading rates and the type of feedstocks. Therefore, it is imperative to critically review the recent research to understand the impacts of using different CMs in TAD. This review paper discusses the types and properties of CMs applied in TAD and the mechanisms of how they influence methanogenesis, digester start-up time, process disturbances, microbial community, and biogas desulfurization. The engineering challenges for industrial-scale applications and environmental risks were also discussed. Finally, critical research gaps have been identified to provide a framework for future research.

Graphynes and Graphdiynes for Energy Storage and Catalytic Utilization: Theoretical Insights into Recent Advances

Carbon allotropes have contributed to all aspects of people's lives throughout human history. As emerging carbon-based low-dimensional materials, graphyne family members (GYF), represented by graphdiyne, have a wide range potential applications due to their superior physical and chemical properties. In particular, graphdiyne (GDY), as the leader of the graphyne family, has been practically applied to various research fields since it was first successfully synthesized. GYF have a large surface area, both sp and sp² hybridization, and a certain band gap, which was considered to originate from the overlap of carbon 2p_z orbitals and the inhomogeneous π-bonds of carbon atoms in different hybridization forms. These properties mean GYF-based materials still have many potential applications to be developed, especially in energy storage and catalytic utilization. Since most of the GYF have yet to be synthesized and applications of successfully synthesized GYF have not been developed for a long time, theoretical results in various application fields should be shared to experimentalists to attract more intentions. In this Review, we summarized and discussed the synthesis, structural properties, and applications of GYF-based materials from the theoretical insights, hoping to provide different viewpoints and comments.

Graphdiyne and Its Derivatives as Efficient Charge Reservoirs and Transporters in Semiconductor Devices

2D graphdiyne (GDY), which is composed of sp and sp² hybridized carbon atoms, is a promising semiconductor material with a unique porous lamellar structure. It has high carrier mobility, tunable bandgap, high density of states, and strong electrostatic interaction ability with ions and organic functional units. In recent years, interests in applying GDYs (GDY and its derivatives) in semiconductor devices have been growing rapidly, and great achievements have been made. Attractively, GDYs could act as efficient reservoirs and transporters for both carriers and ions, which endows them with enormous potential in future novel optoelectronics. In this review, the progress in this field is systematically summarized, aiming to bring an in-depth insight into the GDYs' intrinsic uniqueness. Particularly, the effects of GDYs on carrier dynamics and ionic interactions in various semiconductor devices are succinctly described, analyzed, and concluded.

Graphdiyne applications in sensors: A bibliometric analysis and literature review

Graphdiyne is a two-dimensional carbon nanomaterial synthesized artificially in 2010. Its outstanding performance is considered to have great potential in different fields. This article summarizes the work of graphdiyne in the sensing field by literature summary and bibliometrics analysis. The development of graphdiyne in the field of sensing has gone through a process from theoretical calculation to experimental verification. Especially in the last three years, there has been very rapid development. The theoretical calculations suggest that graphdiyne is an excellent gas sensing material, but there is little experimental evidence in this direction. On the contrary, graphdiyne has been widely reported in the field of electrochemical sensing. At the same time, graphdiyne can also be used as a molecular switch for DNA sequencing. Fluorescent sensors based on graphdiyne have also been reported. In general, the potential of graphdiyne in sensing still needs to be explored. Current research results do not show that graphdiyne has irreplaceable advantages in sensing. The bibliometric analysis used in this review also provides cooperative network analysis and co-citation analysis on this topic. This provides a reference for the audience wishing to undertake research on the topic. In addition, according to the analysis, we also listed the direction that which this field deserves attention in the future.

Influence of Animal/Plant Activated Biochar Properties on Methane Production from Corn Stalk by Anaerobic Fermentation

Activated biochar (ABC) was prepared from typical plant/animal biochar (pig bone biochar/corn stalk biochar) by optimizing the gas production characteristics of anaerobic fermentation. The effects of the physical and chemical properties (specific surface area, surface functional group and conductivity) of ABC on the gas production characteristics of anaerobic fermentation were investigated. The results showed that the effect of pig-bone activated biochar (PABC) on anaerobic fermentation gas production characteristics was better than that of corn-stalk activated biochar (CABC). The peak period of gas production or methane production was up to 4 days earlier than that of the control group, and the cumulative methane production was up to 68% higher; this can shorten the fermentation period for up to 7 days, and the effect of stabilizing pH is better. In addition, the surface functional groups are not the dominant factors affecting the gas production characteristics, but the effects of conductivity and specific surface area cannot be neglected. For most experimental groups, when the specific surface area of PABC is more than 90 m2/g and the specific surface area of CABC is more than 100 m2/g. Methane production increases with the specific surface area increases and the controllable range of CBAC is relatively wider than that of PBAC. When the conductivity of CABC is more than 650 μS/cm and the conductivity of PABC is more than 1000 μS/cm, the conductivity has a positive correlation with methane production.

Elucidation of noble gas cluster configurations bound on graphdiyne: A metaheuristic approach

Graphynes are a class of all-carbon two-dimensional membranes that have been intensely researched for various membrane-based technologies on account of their unique pore architectures. Herein, we report an investigation of the mechanism and energetics of adsorption of noble gases (He, Ne and Ar) on graphdiyne (GDY), the most popular form of graphynes. Two global optimization techniques, namely particle swarm optimization (PSO) and differential evolution are employed to predict the putative global minima configurations of rare gas clusters in the size range 1-30 when adsorbed on GDY. We use the 12-6 Lennard-Jones potential to represent the pairwise non-covalent interactions between various interacting atoms. Initially, the gas atoms adsorb as monolayers on GDY at the centers of the triangular pores until all the triangular pores are filled. This is followed by a second layer formation on top of the hexagonal pore centers or on top of the C-C bonds. The findings from the empirical approach are further validated by performing density functional theory calculations on the predicted adsorbed cluster configurations. We have also looked into the adsorption of noble gas clusters on bilayer GDY systems and have found that the intercalation of gas atoms within the bilayers is feasible. Our study suggests that the stochastic nature of the swarm intelligence technique, PSO can assist in an effective search of the potential energy surfaces for the global minima, eventually enabling large-scale simulations.

Nitrogen-Containing Gas Sensing Properties of 2-D Ti2N and Its Derivative Nanosheets: Electronic Structures Insight

In this work, the potentials of two-dimensional Ti2N and its derivative nanosheets Ti2NT2(T=O, F, OH) for some harmful nitrogen-containing gas (NCG) adsorption and sensing applications have been unveiled based on the quantum-mechanical Density Functional Theory calculations. It is found that the interactions between pure Ti2N and NCGs (including NO, NO2, and NH3 in this study) are very strong, in which NO and NO2 can even be dissociated, and this would poison the substrate of Ti2N monolayer and affect the stability of the sensing material. For the monolayer of Ti2NT2(T=O, F, OH) that is terminated by functional groups on surface, the adsorption energies of NCGs are greatly reduced, and a large amount of charges are transferred to the functional group, which is beneficial to the reversibility of the sensing material. The significant changes in work function imply the good sensitivity of the above mentioned materials. In addition, the fast response time further consolidates the prospect of two-dimensional Ti2NT2 as efficient NCGs' sensing materials. This theoretical study would supply physical insight into the NCGs' sensing mechanism of Ti2N based nanosheets and help experimentalists to design better 2-D materials for gas adsorption or sensing applications.

Carbon Nanostructures Doped with Transition Metals for Pollutant Gas Adsorption Systems

The adsorption of molecules usually increases capacity and/or strength with the doping of surfaces with transition metals; furthermore, carbon nanostructures, i.e., graphene, carbon nanotubes, fullerenes, graphdiyne, etc., have a large specific area for gas adsorption. This review focuses on the reports (experimental or theoretical) of systems using these structures decorated with transition metals for mainly pollutant molecules' adsorption. Furthermore, we aim to present the expanding application of nanomaterials on environmental problems, mainly over the last 10 years. We found a wide range of pollutant molecules investigated for adsorption in carbon nanostructures, including greenhouse gases, anticancer drugs, and chemical warfare agents, among many more.

Electrochemical sensing behavior of graphdiyne nanoflake towards uric acid: a quantum chemical approach

Though the gas sensing applications of graphdiyne have widely reported; however, the biosensing utility of graphdiyne needs to be explored. This study deals with the sensitivity of graphdiyne nanoflake (GDY) towards the uric acid (UA) within the density functional framework. The uric acid is allowed to interact with graphdiyne nanoflake from all the possible orientations. Based on these interacting geometries, the complexes are differentiated with naming, i.e., UA1@GDY, UA2@GDY, UA3@GDY, and UA4@GDY (Fig. 1). The essence of interface interactions of UA on GDY is derived by computing geometric, energetic, electronic, and optical properties. The adsorbing affinity of complexes is evaluated at ωB97XD/6-31 + G(d, p) level of theory. The stabilities of the complexes are quantified through the interaction energies (E_int) with reasonable accuracy. The calculated E_int of the UA1@GDY, UA2@GDY, UA3@GDY, and UA4@GDY complexes are - 31.13, - 25.87, - 20.59, and - 16.54 kcal/mol, respectively. In comparison with geometries, it is revealed that the higher stability of complexes is facilitated by π-π stacking. Other energetic analyses including symmetry adopted perturbation theory (SAPT), noncovalent interaction index (NCI), and quantum theory of atoms in molecule (QTAIM) provide the evidence of dominating dispersion energy in stabilizing the resultant complexes. The HOMO-LUMO energies, NBO charge transfer, and UV-vis analysis justify the higher electronic transition in UA1@GDY, plays a role of higher sensitivity of GDY towards the π-stacked geometries over all other possible interaction orientations. The present findings bestow the higher sensitivity of GDY towards uric acid via π-stacking interactions. Fig. 1 Optimized geometries (with interaction distances in Å) of UA@GDY complexes.

Post-modified Strategies of Graphdiyne for Electrochemical Applications

The new carbon material graphdiyne (GDY) has been verified to have a great application prospect in electrochemical field. In order to study its properties and expand its scope of application, various experiments including structural control tests are imposed on GDY. Among them, as one of the most commonly used methods to modify the structure, heteroatom doping is favored for its advantages in synthesis methods and the control of mechanical, electrical and even magnetic properties of carbon materials. According to the published studies, the top-down methods of doping heteroatoms for GDY only need cheap raw materials, simple synthetic route and strong controllability, which is conducive to rapid performance breakthroughs in electrochemical applications. This review selects the typical cases in the development of that post-modification method from the application of GDY in the electrochemical field. Here, based on the existed reports, the commonly used non-metal elements (such as nitrogen, sulfur) and metal elements (such as iron) have been introduced to post-modify GDY. Then, a detailed analysis is made for corresponding electrochemical applications, such as energy storage and electrocatalysis. Finally, the challenges and prospects of post-modified GDY in synthesis and electrochemical applications are proposed. This review provides us a useful guidance for the development of high-quality GDY suitable for electrochemical applications.

Exceptionally high NLO response and deep ultraviolet transparency of superalkali doped macrocyclic oligofuran rings

Cyclic oligofurans containing five and six furan rings (5CF & 6CF) doped with superalkalis are presented here as a new type of NLO material.

The Accelerating World of Graphdiynes

Graphdiyne (GDY), a 2D allotrope of graphene, is first synthesized in 2010 and has attracted attention as a new low-dimensional carbon material. This work surveys the literature on GDYs. The history of GDYs is summarized, including their relationship with 2D graphyne carbons and yearly publication trends. GDY is a molecule-based nanosheet woven from a molecular monomer, hexaethynylbenzene; thus, it is synthesized by bottom-up approaches, which allow rich variation via monomer design. The GDY family and the synthetic procedures are also described. Highly developed π-conjugated electronic structures are common important features in GDY and graphene; however, the coexistence of sp and sp² carbons differentiates GDY from graphene. This difference gives rise to unique physical properties, such as high conductivity and large carrier mobility. Next, the theoretical and experimental studies of these properties are described in detail. A wide variety of applications are proposed for GDYs, including electrocatalysts and energy devices, which exploit the carbon-rich nature, porous framework, and expanded π-electron system of these compounds. Finally, potential uses are discussed.

A comprehensive DFT study on the sensing abilities of cyclic oligothiophenes (nCTs)

Linear conducting polymers are extensively studied as sensors for various analytes, whereas studies on cyclic analogues are limited.

Direct interspecies electron transfer via conductive materials: A perspective for anaerobic digestion applications

Anaerobic digestion (AD) is a microbial process that produces renewable energy in the form of methane by treating organic waste and high-strength wastewater. Recent studies have demonstrated that conductive materials can promote direct interspecies electron transfer (DIET) between exoelectrogenic bacteria and methanogenic archaea. DIET via conductive materials is more effective for methane production than interspecies electron transfer using electron carriers such as hydrogen, a principal route of methane production in conventional AD. This critical review presents the current understanding of DIET via conductive materials for methane production, summarizes the relevant studies published to date, and analyzes these studies with regard to conductive materials, substrates, inocula, performance, and microorganisms. Based on this analysis, possible future directions are suggested for practical DIET applications via conductive materials in AD.