A DFT study of the adsorption of deep eutectic solvents onto graphene and defective graphene nanoflakes

The interaction of four deep choline chloride-derived eutectic solvents (DESs) with both graphene nanoflakes (GNF) and its defective double-vacancy and Stone–Wales forms (DV-GNF and SW-GNF), was evaluated using density functional theory (DFT). The presence of defects increases the adsorption energy of DESs, following the order DES∩DV-GNF \u3e DES∩SW-GNF \u3e DES∩GNF. Non-covalent interaction and energy decomposition analyses show that the interactions are noncovalent and dominated by dispersive forces. Furthermore, we find that the presence of aromatic moieties in the DESs increases the van der Waals interactions with the surfaces. These interactions decrease the HOMO-LUMO (Eg) energy gap of the surfaces and thus increase reactivity. Reactivity parameter calculations indicate that the chemical potential (μ) and chemical hardness (η) of the complexes follow the order DES∩GNF \u3e DES∩SW-GNF \u3e DES∩DV-GNF. This order is reversed for the global softness (S) and electrophilicity index (ω). Time-dependent DFT (TD-DFT) calculations predict that the adsorption of DESs onto DV-GNF and SW-GNF should red shift absorption, while the absorption spectrum of GNF surface remains unchanged upon DES adsorption. The biggest changes in the absorption spectra are observed upon adsorption of DESs on the DV-GNF surface due to the stronger affinity of the DESs for this surface

Laccase-catalyzed synthesis of conducting polyaniline-lignosulfonate composite

Enzymatic polymerization of aniline was first performed in lignosulfonate (LGS) template system. High-redox-potential catalyst laccase, isolated from Aspergillus, was used as a biocatalyst in the synthesis of conducting polyaniline/lignosulfonate (PANI-ES-LGS) complex using atmospheric oxygen as the oxidizing agent. The linear templates (LGS), also serving as the dopants, could facilitate the directional alignment of the monomer and improve the solubility of the conducting polymer. The process of the polymerization was monitored using UV-Vis spectroscopy, by which the conditions for laccase-catalyzed synthesis of PANI-ES-LGS complex were also optimized. The structure characterizations and solubility of the complex were carried out using corresponding characterization techniques respectively. The PANI-ES-LGS suspensions obtained was used as coating for cotton with a conventional padder to explore the applications of the complex. The variable optoelectronic properties of the coated cotton were confirmed by cyclic voltammetry and color strength test. The molecular weight changes of LGS treated by laccase were also studied to discuss the mechanism of laccase catalyzed aniline polymerization in LGS template system.This work was financially supported by National Natural Science Foundation of China (21274055, 51173071), Program for New Century Excellent Talents in University (NCET-12-0883), the Fundamental Research Funds for the Central Universities (JUSRP51312B), China Scholarship Council and the Graduate Student Innovation project (KYLX_1140)

Conducting polymer nanocomposite-based supercapacitors

The use of nanocomposites of electronically-conducting polymers for supercapacitors has increased significantly over the past years, due to their high capacitances and abilities to withstand many charge-discharge cycles. We have recently been investigating the use of nanocomposites of electronically-conducting polymers containing conducting and non-conducting nanomaterials such as carbon nanotubes and cellulose nanocrystals, for use in supercapacitors. In this contribution, we provide a summary of some of the key issues in this area of research. This discussion includes some history, fundamental concepts, the physical and chemical processes involved, and the challenges that these nanocomposite materials must overcome in order to become technologically viable. Due to space limitations, this is not a complete review of all the work that has been done in this field and we have focused on common themes that appear in the published work. Our aim is that this chapter will help readers to understand the advantages and challenges involved in the use of these materials in supercapacitors and to identify areas for further development

Preparation and Application of Electrodes in Capacitive Deionization (CDI): a State-of-Art Review

As a promising desalination technology, capacitive deionization (CDI) have shown practicality and cost-effectiveness in brackish water treatment. Developing more efficient electrode materials is the key to improving salt removal performance. This work reviewed current progress on electrode fabrication in application of CDI. Fundamental principal (e.g. EDL theory and adsorption isotherms) and process factors (e.g. pore distribution, potential, salt type and concentration) of CDI performance were presented first. It was then followed by in-depth discussion and comparison on properties and fabrication technique of different electrodes, including carbon aerogel, activated carbon, carbon nanotubes, graphene and ordered mesoporous carbon. Finally, polyaniline as conductive polymer and its potential application as CDI electrode-enhancing materials were also discussed

Effect of Mono-Vacant Defects on the Adsorption Properties of Deep Eutectic Solvents onto Hexagonal Boron-Nitride Nanoflakes

Hexagonal boron nitride is a promising material for a variety of electronic, optical, and material science applications. Both the synthesis of the material through exfoliation, and its various applications almost inevitably require its solvation. Deep eutectic solvents (DES) are extremely useful solvents for these types of applications due to their non-volatility, inflammability, biocompatibility, and reasonable cost. There are many different deep eutectic solvents available, and their suitability for any given application is particularly dependent on the specific of their structure. DES have been examined computationally for use with boron nitride, but these calculations use idealized, perfect boron nitride sheets instead of the more realistic, defect-containing systems. In this report, we investigated four DESs with two experimentally observed defective boron nitride, one with a single boron vacancy, the other with a single nitrogen vacancy. All DESs bound with higher affinity to the defective boron nitride than to the pristine surface. Charge transfer was minimal in all cases although the surfaces tended to donate electron density to the solvents. The interactions between the solvents and the surfaces are primarily non-covalent although in several cases natural bond order analysis indicates a partial covalent interaction that helps explain the higher-than-expected affinity for particular DES. The DESs have little effect on the predicted optical behaviour of the pristine boron nitride but do significantly change the adsorption spectrum of the defective boron nitride nanoflakes; the effect on bulk material might be limited. Together these results suggest that the choice of DES can either be made to limit any effect on the properties of the material (urea-choline chloride) or to affect the optical and electronic nature of the material (benzoic acid-choline chloride)

Effect of mono-vacant defects on the adsorption properties of deep eutectic solvents onto hexagonal boron-nitride nanoflakes

Hexagonal boron nitride is a promising material for a variety of electronic, optical, and material science applications. Both the synthesis of the material through exfoliation, and its various applications almost inevitably require its solvation. Deep eutectic solvents (DES) are extremely useful solvents for these types of applications due to their non-volatility, inflammability, biocompatibility, and reasonable cost. There are many different deep eutectic solvents available, and their suitability for any given application is particularly dependent on the specific of their structure. DES have been examined computationally for use with boron nitride, but these calculations use idealized, perfect boron nitride sheets instead of the more realistic, defect-containing systems. In this report, we investigated four DESs with two experimentally observed defective boron nitride, one with a single boron vacancy, the other with a single nitrogen vacancy. All DESs bound with higher affinity to the defective boron nitride than to the pristine surface. Charge transfer was minimal in all cases although the surfaces tended to donate electron density to the solvents. The interactions between the solvents and the surfaces are primarily non-covalent although in several cases natural bond order analysis indicates a partial covalent interaction that helps explain the higher-than-expected affinity for particular DES. The DESs have little effect on the predicted optical behaviour of the pristine boron nitride but do significantly change the adsorption spectrum of the defective boron nitride nanoflakes; the effect on bulk material might be limited. Together these results suggest that the choice of DES can either be made to limit any effect on the properties of the material (urea-choline chloride) or to affect the optical and electronic nature of the material (benzoic acid-choline chloride)

The interaction of deep eutectic solvents with pristine carbon nanotubes and their associated defects: A density functional theory study

In this study, the interaction of four deep eutectic solvents (DESs): [Choline chloride][Urea] ([ChCl][U]), [Choline chloride][Ethylene glycol] ([ChCl][EG]), [Choline chloride][Glycerol] ([ChCl][Gly]) and [Choline chloride][Benzoic acid] ([ChCl][BA]), with pristine carbon nanotube (CNT) and its defects: double-vacancy and Stone–Wales structures (CNT-DV and CNT-SW) is investigated using density functional theory (DFT) calculations. The geometry optimization, electronic property calculations, noncovalent interaction analysis and optical properties of the DES@nanotube complexes were carried out at the M06-2X/cc-pVDZ level of theory. The adsorption energy (Eads) calculations show that the presence of the DV and SW defects on the CNT increases the adsorption strength of the DESs, DES@CNT-SW \u3e DES@CNT-DV \u3e DES@CNT. On the other hand, the adsorption energy values increase with an increase in the volume of DESs due to the increase of noncovalent interactions, following the order [ChCl][BA] \u3e [ChCl][Gly] \u3e [ChCl][U] \u3e [ChCl][EG]. The calculation of the HOMO-LUMO energy gap (Eg) and chemical hardness (η) of the DES@nanotube complexes indicates that the DES@CNT-SW complexes have the largest Eg and η values and thus the lowest chemical reactivity. The analysis of the interactions between the nanotubes and the DESs using noncovalent interaction (NCI) plots and energy decomposition analysis (EDA) suggests that the DESs adsorb onto the nanotubes through van der Waals interactions and that dispersive interactions dominate (dispersion interaction energy (ΔEdisp) \u3e electrostatic interaction energy (ΔEelec) \u3e orbital interaction energy (ΔEorb)). Predicted ultraviolet–visible absorption spectra of the complexes show that the adsorption of DESs on the nanotubes has only a very marginal effect on the optical response of the nanotubes. Transition density matrix heat maps reveal that the electrons and holes localize to the CNT, CNT-DV and CNT-SW surfaces in the DES@nanotube complexes, indicating that the charge transfer occurs mostly on the surfaces