An experimental and computational study of graphene oxide functionalized with tris(hydroxymethyl)aminomethane as an electrode material for supercapacitors.

In this research, graphene oxide (GO) functionalized with tris(hydroxymethyl)aminomethane (T) was synthesized with a simple one-pot method, and applied as an electrode material for supercapacitors. Electrochemical measurements on the synthesized tris(hydroxymethyl)aminomethane-functionalized graphene oxide (GO@T) indicated a specific capacitance of 549.8 F g- 1 at a specific current of 2.5 A g- 1 and a specific capacitance of 358 F g-1 at a specific current of 7 A g- 1 in the potential range of - 0.5-0.5 V versus Ag/AgCl. It also showed a high cyclic stability. According to the results, 80 and 68% of the initial capacitance was retained after 5500 and 9300 cycles, respectively. Density functional theory calculations were used to investigate the quantum capacitance, free energy change during functionalization reaction, and the layer distance of GO and GO@T.

Computational study of H2S adsorption on the pristine and transitional metal-doped phosphorene.

This study aimed to investigate the H2S molecule adsorption on the pristine and X-doped phosphorene (X = first-row transition metal) using DFT+U method. The doping of X atoms on the phosphorene has been evaluated from energetic and electronics aspects. The binding energy values and the results of projected density of states (PDOS) analysis revealed that Ti-, V-, Fe-, and Sc-doped phosphorene have more capability to adsorb H2S molecule in comparison with other systems. Moreover, the cohesive energy values showed that these (Ti, V, Fe, and Sc) doped surfaces are also energetically feasible.

Exploring the effect of phosphorus doping on the utility of g-C3N4 as an electrode material in Na-ion batteries using DFT method.

The suitability of P-doped g-C3N4 for sodium storage was assessed using density functional theory. The electronic structure of P-doped g-C3N4 was calculated and the results indicate that the presence of the P atom causes the band gap of g-C3N4 to narrow. Na adsorption on a P-g-C3N4 sheet was investigated. Projected density of states (PDOS) analysis revealed that pyridinic nitrogen atoms in g-C3N4 play the main role in Na adsorption. High binding energies were calculated for Na storage on g-C3N4, leading to a high voltage range (1-3 V) and a high Na diffusion barrier (2.3 eV). Doping the substrate with more P atoms resulted in lower voltages (below 2.2 V), easier Na diffusion (with a barrier of 1.2 eV), and therefore a material that was better suited than g-C3N4 for use in anodes.

Mixed micellization of gemini and conventional surfactant in aqueous solution: a lattice Monte Carlo simulation.

In the current study, we have investigated the micellization of pure gemini surfactants and a mixture of gemini and conventional surfactants using a 3D lattice Monte Carlo simulation method. For the pure gemini surfactant system, the effects of tail length on CMC and aggregation number were studied, and the simulation results were found to be in excellent agreement with the experimental results. For a mixture of gemini and conventional surfactants, variations in the mixed CMC, interaction parameter ß, and excess Gibbs free energy G(E) with composition revealed synergism in micelle formation. Simulation results were compared to estimations made using regular solution theory to determine the applicability of this theory for non-ideal mixed surfactant systems. A large discrepancy was observed between the behavior of parameters such as the activity coefficients fi and the excess Gibbs free energy G(E) and the expected behavior of these parameters as predicted by regular solution theory. Therefore, we have used the modified version of regular solution theory. This three parameter model contains two parameters in addition to the interaction parameters: the size parameter, ρ, which reflects differences in the size of components, and the packing parameter, P*, which reflects nonrandom mixing in mixed micelles. The proposed model provides a good description of the behavior of gemini and conventional surfactant mixtures. The results indicated that as the chain length of gemini surfactants in mixture is increased, the size parameter remains constant while the interaction and packing parameters increase.

Monte Carlo simulation of binary surfactant/contaminant/water systems.

Surfactant-enhanced remediation (SER) is an effective approach for the removal of absorbed hydrophobic organic compounds (HOCs) from contaminated soils. The solubilization of contaminants by mixed surfactants with attractive and repulsive head-head interactions was studied by measuring the micelle-water partition coefficient (K(C)) and molar solubilization ratio (MSR) using the lattice Monte Carlo method. The effect of surfactant mixing on the MSR and K(C) of contaminants displayed the following trend: C4 > C3 > C2. Synergistic binary surfactant mixtures showed greater solubilization capacities for contaminants than the corresponding individual surfactants. Mixed micellization parameters, including the interaction parameter ß, and activity coefficient f(i), were evaluated with Rubingh's approach. Synergistic mixed-surfactant systems can improve the performance of surfactant-enhanced remediation of soils and groundwater by decreasing the amount of applied surfactant and the cost of remediation.

Role of interaction energies in the behavior of mixed surfactant systems: a lattice Monte Carlo simulation.

We have investigated micellization in systems containing two surfactant molecules with the same structure using a lattice Monte Carlo simulation method. For the binary systems containing two surfactants, we have varied the head-head interactions or tail-tail repulsions in order to mimic the nonideal behavior of mixed surfactant systems and to manipulate the net interactions between surfactant molecules. The simulation results indicate that interactions between headgroups or tailgroups have an effect on thermodynamic properties such as the mixed critical micelle concentration (cmc), distribution of aggregates, shape of the aggregates, and composition of the micelles formed. Moreover, we have compared the simulation results with estimates based on regular solution theory, a mean-field theory, to determine the applicability of this theory to the nonideal mixed surfactant systems. We have found that the simulation results agree reasonable well with regular solution theory for the systems with attractions between headgroups and repulsions between tailgroups. However, the large discrepancies observed for the systems with head-head repulsions could be attributed to the disregarding of the correlation effect on the interaction among surfactant molecules and the nonrandom mixing effect in the theory.

Investigation of the mixing behavior of surfactants by lattice Monte Carlo simulation.

We have studied the behavior of binary surfactant mixtures using the Monte Carlo (MC) simulation technique with a three-dimensional lattice model of a binary surfactant mixture, in which the constituent surfactant species are represented by a series of connected grid sites. Head-head interactions, alone and along with tail-tail interactions, among identical surfactant species were varied to imitate non-ideal mixing and to manipulate the net attractions and repulsions between surfactant species. We found that the head-head and tail-tail interactions affect both the mixed critical micelle concentration and distribution of aggregates. The simulation results are analyzed in the light of the phase separation model, which considers micelles as separate bulk pseudo-phase. Our studies reveal that regular solution theories do not present a satisfactory description for such systems. The discrepancies observed between the theoretical and simulation results for the studied systems could be attributed to the nonrandom mixing effect in simulation, which is neglected in regular solution theory.