Observation of different charge transport regimes and large magnetoresistance in graphene oxide layers

We report a systematic study on charge transport properties of thermally reduced graphene oxide (rGO) layers, from room temperature to 2 K and in presence of magnetic fields up to 7 T. The most conductive rGO sheets follow different transport regimes: at room temperature they show an Arrhenius-like behavior. At lower temperature they exhibits a thermally activated behavior with resistance R following a R = R₀exp(T₀/T)^p law with p = 1/3, consistently with 2D Mott Variable Range Hopping (VRH) transport mechanism. Below a given temperature T_c, we observe a crossover from VHR to another regime, probably due to a shortening of the characteristic lengths of the disordered 2D system. The temperature T_c depends on the reduction grade of the rGO. Magnetoresistance ΔR/R of our rGO films shows as well a crossover between positive and negative and below liquid He temperature ΔR/R reaches values larger than ∼–60%, surprisingly high for a – nominally – non magnetic material.     

Crystal and geometry-optimized structure,Hirshfeld surface analysis and spectroscopic studies of tetrachlorocuprate and nitrate salts of 1-(2-fluorophenyl)piperazine cations, (C10H15FN2)[CuCl4] (I) and (C10H14FN2)[NO3] (II)

Two new organic-inorganic hybrid materials, 1-(2-fluorophenyl)piperazine-1,4-diium tetrachlorocuprate, (C₁₀H₁₅FN₂)[CuCl₄] (I) and 1-(2-fluorophenyl)piperazin-4-ium nitrate, (C₁₀H₁₄FN₂)[NO₃] (II), have been synthesized by an acid/base reaction at room temperature in the presence of 1-(2-fluorophenyl)piperazine as an organic-structure directing agent and their structures were determined by single crystal X-ray diffraction. Compound (I), (C₁₀H₁₅FN₂)[CuCl₄], crystallizes in the monoclinic system and P2₁/c space group with a = 7.5253 (2), b = 20.6070 (7), c = 9.7281 (3) Å, β = 103.6730 (17)°, V = 1465.82 (8) Å³ with Z = 4. Full-matrix least-squares refinement converged at R = 0.037 and wR(F²) = 0.088. Compound (II), (C₁₀H₁₄FN₂)[NO₃], belongs to the monoclinic system, space group P2₁/c with the following parameters: a = 10.8034 (2), b = 7.5775 (1), c = 14.4670 (3) Å, β = 111.761 (2)°, V = 1099.91 (4) ų and Z = 4. The structure was refined to R = 0.044, wR(F²) = 0.136.In the structures of (I) and (II), the anionic and cationic entities are interconnected by means of set of hydrogen bonding contacts forming three-dimensional networks. Intermolecular interactions were investigated by Hirshfeld surfaces and the contacts of the four different chloride atoms were notably compared. The results of the optimized molecular structure are presented and compared with the experimental one. The Molecular Electrostatic Potential (MEP) maps and the HOMO and LUMO energy gap of both compounds were computed. The vibrational absorption bands were identified by infrared spectroscopy. Theory (DFT) calculations of normal mode frequencies are compared with experimental ones.     

Densification behavior and electrical properties of CuO-doped Pb(In1/2Nb1/2)O3–Pb(Mg1/3Nb2/3)O3–PbTiO3 ternary ceramics

CuO modified Pb(In_1/2Nb_1/2)O₃–Pb(Mg_1/3Nb_2/3)O₃–PbTiO₃ (PIN–PMN–PT) ternary relaxor based ferroelectrics with the composition near the morphotropic phase boundary were synthesized by two-step columbite precursor method. The introduction of CuO significantly improved the sinterability of PIN–PMN–PT ceramics, resulting in the full densification of samples at lower sintering temperatures. It also profoundly modified the crystal structure and fracture mode of the ceramics. Properly increasing CuO content led to the disappearance of rhombohedral-tetragonal phase transition, remarkably improved the Curie temperature (T_c), and made the ceramics more relaxorlike. The ternary ceramics doped with 0.25 wt% CuO possessed optimum piezoelectric properties (d₃₃=584 pC/N, d₃₃^*=948 pC/N, and k_p=0.68), high ferroelectric properties (E_c=9.9 kV/cm, and P_r=33.1 μC/cm²), low dielectric loss (tan δ=0.9%), and wider temperature usage range (T_c=225 °C). The obtained properties are much higher than those of previously reported PIN–PMN–PT based ceramics, indicating that CuO doped PIN–PMN–PT is a promising candidate for electromechanical applications with high performance and wide temperature/electric field usage ranges.     

Frequency scaling of ac hopping transport in amorphous carbon nitride

The dynamics of hopping transport in amorphous carbon nitride is investigated in both Ohmic and non-linear regimes. Dc current and ac admittance were measured in a wide range of temperatures (90 K < T < 300 K), electric fields (F < 2 × 10⁵ V cm^− 1) and frequencies (10² < f < 10⁶ Hz).The dc Ohmic conductivity is described by a Mott law, i.e. a linear ln(σ_OHMIC) vs T^− 1/4 dependence. The scaling of field-enhanced conductivity as ln(σ / σ_OHMIC) = ϕ[F^S / T] with S ≈ 2/3, observed for F > 3 × 10⁴ V cm^− 1 over 5 decades in σ(T,F), is explained by band tail hopping transport; the filling rate, Γ_F(E_DL), of empty states at the transport energy is obtained with a “filling rate” method which incorporates an exponential distribution of localized states, with a non-equilibrium band tail occupation probability f(E) parametrized by an electronic temperature T_EFF (F).As the ac frequency and temperature increase, the increase in conductance G is accurately described by Dyre's model for hopping transport within a random spatial distribution of energy barriers. This model predicts a universal dependence of the complex ac conductivity of the form σ_ac = σ(0)[iωτ / ln(1 + iωτ)], where σ(0) is the zero frequency ac conductivity and τ(T,F) is a characteristic relaxation time. We find that the inverse characteristic time 1 / τ can also be described by a Mott law. It is compatible with the filling rate Γ_F(E_DL) at the transport energy, which governs the dc conductivity; this rate increases with increasing dc field, as more empty states become available in the band tail for hopping transitions. This “universal” scaling law for the ac conductance provides a scaling parameter K(T,F) = τ(T,F) σ(T,F,ω = 0) / ɛ which is found to decrease with increasing electric field from 5 to 0.5, depending weakly on temperature. Our band tail hopping model predicts a high-field value of K(T,F) smaller than the Ohmic value, under the condition (eFγ^− 1 / E°) ≤ (kT / E°)^1/4, where γ^− 1 is the localization radius and E° the disorder energy of the band tail distribution.     

Piezoelectric properties and temperature stabilities of Mn- and Cu-modified BiFeO3–BaTiO3 high temperature ceramics

The structures, microstructures, electrical properties and the thermal stability have been investigated for the MnO₂-doped (1 ? x)BF–xBT system and the MnO₂ and CuO-doped (1 ? x)BF–xBT system, where x ranges from 0.25 to 0.35. The XRD analysis shows that the two systems have a single perovskite phase, and the MnO₂ and CuO-doped (1 ? x)BF–xBT system has a morphotropic phase boundary (MPB) with the coexistence of rhombohedral and pseudo-cubic phases in the system about x = 0.325. The addition of small amount of CuO was quite effective to lower the sintering temperature. The diffusive phase transition characteristics were observed in the MnO₂-doped (1 ? x)BF–xBT system and a normal ferroelectric phase transition characteristics were observed in the MnO₂ and CuO doped (1 ? x)BF–xBT system. Compared with the MnO₂ doped (1 ? x)BF–xBT system, the ?_m, Curie temperature (T_c), depoling temperature (T_d), and piezoelectrical properties were improved evidently with the MnO₂ and CuO doping.     

A predictive method for the solubility of drug in supercritical carbon dioxide

We present a predictive approach for the solubility of drug in supercritical CO₂. The fugacity of drug in the solid phase is estimated from its melting temperature and heat of fusion, and the fugacity of the drug in its hypothetical liquid state. The fugacity of the drug is calculated from the Peng–Robinson (PR) EOS. Temperature and composition dependence of the interaction parameters a(T,x) and b(x) of the PR EOS are obtained from the quantum mechanics-based, COSMO-SAC solvation model. As a consequence, the method does not require input of experimental data of the mixture. The average logarithmic deviation (ALD-x) in predicted solubility of 46 drugs in subcritical and supercritical carbon dioxide (T = 293.15–473 K, P = 8.5–50 MPa, and 1160 solubility data ranging from 10⁻⁷ to 10⁻²) was found to be 0.81 (a factor of 5.3). The same method was also examined for solid solubility in a variety of solvents (60 solids including 34 different solvents (with different polarities) and 190 drug-solvent pairs) at ambient pressure. The ALD-x was found to be slightly better (0.58 or a factor of 2.89). The proposed method, the PR + COSMOSAC EOS, is thus a useful tool for a priori prediction of solid solubility in scCO₂, as well as for other solvents.     

Electrical properties of [Li0.04(K0.5Na0.5)0.96−xAgx](Nb1−ySby)O3 ceramics

Dependence of electrical properties on the structural characteristics of Li_0.04(K_0.5Na_0.5)_0.96(Nb_1?ySb_y)O₃ (LKNNS (x = 0, 0.00 ≤ y ≤ 0.10)) and [Li_0.04(K_0.5Na_0.5)_0.96?xAg_x](Nb_0.925Sb_0.075)O₃ (LKNANS (0.01 ≤ x ≤ 0.05, y = 0.075)) were investigated. The oxygen octahedral distortion was dependent on Ag⁺ and/or Sb⁵⁺ content which affected to the phase transition temperature of LKNNS and LKNANS ceramics. The orthorhombic–tetragonal and tetragonal–cubic phase transition temperatures (T_O–T, T_C) of the specimens were decreased with increasing of average octahedral distortion. With increasing of Sb⁵⁺ content, the electromechanical coupling factor (k_p), piezoelectric constant (d₃₃) and dielectric constant (?_r) of the sintered specimens were increased up to y = 0.075, and then decreased. These results could be attributed to the shift of T_O–T to near room temperature for Li_0.04(K_0.5Na_0.5)_0.96(Nb_0.0925Sb_0.075)O₃.     

Use of artificial neural networks for prediction of phase equilibria in the binary system containing carbon dioxide

Present work investigated the potential of artificial neural network (ANN) model to correlate the bubble and dew points pressures of binary systems containing carbon dioxide (CO₂) and hydrocarbon systems as functions of reduced temperature of non-CO₂ compounds, critical pressure, acentric factor of non-CO₂ compounds and CO₂ composition. In this regards, five binary systems at the temperature and pressure ranges of 263.15–393.15 K at 0.18–12.06 MPa were used to examine the feasibility of cascade-forward back-propagation ANN model. In this regard, the collected experimental data were divided in to two different subsets namely training and testing subsets. The training subset was selected in a way that covers all the ranges of the experimental data and operating conditions. Then, the accuracy of the proposed ANN model was evaluated through a test data set not used in the training stage. The optimal configuration of the proposed model was obtained based on the error analysis including minimum average absolute relative deviation percent (AARD %) and the appropriate (close to one) correlation coefficient (R²) of test data set. The obtained results show that the optimum neural network architecture was able to predict the phase envelope of binary system containing CO₂ with an acceptable level of accuracy of AARD % of 2.66 and R² of 0.9950 within their experimental uncertainty. In addition, comparisons were done between the Peng–Robinson (PR) equation of state (EOS) and ANN model for three different binary systems including CO₂ + 1-hexene, CO₂ + n-Hexane, and CO₂ + n-butane. Results show that developed optimal ANN model is more accurate compared to the PR EOS.     

Kinetic and thermodynamic investigations of non-isothermal decomposition process of a commercial silver nitrate in an argon atmosphere used as the precursors for ultrasonic spray pyrolysis (USP): The mechanistic approach

The non-isothermal decomposition process of commercial silver nitrate used as the precursor for the USP procedure was investigated by simultaneous TGA–DTA measurements at different heating rates, in an argon atmosphere. Detailed kinetic and thermodynamic analyses, with special emphasis on the formation of a complete mechanistic scheme of the process were performed. It was found that the process under study can be described by the acceleratory power law kinetic model (P2), in the range of the extent of conversion (α) values (0.15 ≤ α ≤ 0.85), where the value of the apparent activation energy (E_a) can be considered as the constant (141.3 kJ mol⁻¹). The kinetic prediction analysis was shown that only the power law kinetic model (f(α) = 2α^1/2) gives the value of E_a which is consistent with the value obtained from the isothermal conditions. The critical temperature (T_c) of decomposition process was determined. The resulting value of T_c was in fairly good agreement with the starting temperature of thermal decomposition of silver oxide (Ag₂O). The thermodynamic functions of decomposition process are calculated by the activated complex theory and showed that the silver–oxygen bond secession can be interpreted as a “slow” stage of the decomposition process.     

Reactivity of cyrhetrenylphosphines: Synthesis and characterization of oxides,boranes and selenides

Reaction of cyrhetrenylphosphines, of general formula (η⁵-C₅H₄PR₂)Re(CO)₂L (R = Ph, L = CO (1); R = Cy; L = CO (2); R = Ph, L = PMe₃ (3) and R = Ph, L = P(OMe)₃ (4)), with H₂O₂, BH₃·THF or selenium gives the respective cyrhetrenylphosphine oxides, boranes and selenides. These species were characterized by standard spectroscopic techniques (FT-IR, ¹H and ³¹PNMR). Based on the ³¹P⁷⁷Se coupling constant (¹J_P-Se) of the phosphine-selenides, we established the following order of basicity of the parent cyrhetrenylphosphine 2 > 3 > 4 > 1. We also confirmed the opposite electronic effects of the cyrhetrenyl and ferrocenyl groups attached to a –PR₂ unit. Finally, phosphine selenides 2c and 4c were structurally characterized by X-ray diffraction.     

Synthesis,characterization and sinterablity of 10 mol% Sm2O3-doped CeO2 nanopowders via carbonate precipitation

A carbonate coprecipitation method has been used for the facile synthesis of highly reactive 10 mol% Sm₂O₃-doped CeO₂ (20SDC) nanopowders, employing nitrates as the starting salts and ammonium hydrogen carbonate (AHC) as the precipitant. The AHC/RE³⁺ (RE = Ce + Sm) molar ratio (R) and the reaction temperature (T) affect significantly the final yield and precursor properties, including chemical composition and particle morphology. Suitable processing conditions are T = 60 °C and R = 5.0–10, under which precipitation is complete and the resultant precursors show ultrafine particle size, spherical particle shape, and good dispersion. Thus, the processed precursors are rare-earth carbonates with an approximate formula of Ce_0.8Sm_0.2(CO₃)_1.5·1.8H₂O, which directly yield oxide solid-solutions upon thermal decomposition at a low temperature of ∼440 °C. The 20SDC solid solution powders calcined at 700 °C show excellent reactivity and have been densified to ∼99% of the theoretical via pressureless sintering at a very low temperature of 1200 °C for 4 h.     

Preparation of highly oriented β-SiC bulks by halide laser chemical vapor deposition

Highly oriented β-SiC bulks with high hardness were fabricated by halide laser chemical vapor deposition (HLCVD) using SiCl₄, CH₄ and H₂ as precursors. The effects of total pressure (P_tot) and deposition temperature (T_dep) on the preferred orientation, microstructure, deposition rate (R_dep) and micro-hardness were investigated. The 〈110〉-oriented β-SiC bulks were obtained at low P_tot (2–4 kPa), non-oriented β-SiC bulks were obtained at mediate P_tot (6 kPa), and 〈111〉-oriented β-SiC bulks were obtained at high P_tot (10–40 kPa), exhibiting faceted, cauliflower-like and six-fold pyramid-like microstructure, respectively. The maximum R_dep of 〈111〉- and 〈110〉-oriented β-SiC bulks were 3600 and 1300 μm/h at, respectively. The activation energy obtained by the plot of lgR_dep-T_dep⁻¹ is 170 to 280 kJ mol⁻¹, showing an exponential relation with P_Si. The Vickers micro-hardness of β-SiC bulks increased with increasing P_tot and showed the highest value of 35 GPa at P_tot = 40 kPa with a complete 〈111〉 orientation.     

Defect chemistry of a high-k ‘Y5V’ (Ba0.95Eu0.05)TiO3 ceramic

The influence of the sintering temperature (T_s) on the structure, dielectric and valence-state properties of (Ba_1−xEu_x)TiO₃ (x=0.05) ceramics was investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), electron paramagnetic resonance (EPR), Raman spectroscopy, and dielectric temperature measurements. An increase in T_s can increase the solubility limit of Eu in BaTiO₃. When the T_s was increased to 1450 °C, a high-k ‘Y5V’ (ε′_RT=8500) ceramic (C-BE5T) with a single-phase cubic structure was obtained. The dielectric peak shifted rapidly toward lower temperatures with increasing T_s at a rate of −0.46 °C/K. A symmetric (200) XRD peak, exaggerated grain growth (5.6 μm), a mixed valence of Eu²⁺/Eu³⁺, an asymmetric main Raman band at 2494 cm⁻¹ and a weak sharp band at 1516 cm⁻¹ in the high-wavenumber region are characteristics of cubic symmetry of C-BE5T. The formation of a solid solution of C-BE5T and defect chemistry are discussed.     

Decomposition of allantoin in the presence of Cu(II) ions resulting in the formation of a coordination polymer containing oxalate species

A novel Cu(II) coordination polymer, [Cu(ox)(DMSO)₂]_n (1) (ox-oxalate dianion, DMSO-dimethyl sulphoxide) has been prepared in the reaction of copper nitrate dihydrate and allantoin (5-ureidohydantoin) in DMSO/water solution. Compound (1) crystallizes in the monoclinic, space group P121/c1 with a = 5.1785(7), b = 13.6311(18), c = 8.5386(12) Å, β = 107.524(12)°, V = 574,76(14) Å³, Z = 4, D_cal = 1779 mg/m³, R₁ = 0.0449. The metal ion coordinates through four oxygen atoms belonging to two bidentate bridging oxalate ligands, and two oxygen atoms from two DMSO ligands forming an elongated octahedron. The crystal structure was confirmed by FT-IR and Uv–vis spectroscopic data.     

Pyroelectric,ferroelectric, piezoelectric and dielectric properties of Na0.5Bi0.5TiO3 ceramic prepared by sol-gel method

Sodium bismuth titanate (BNT) nanopowder of molar composition 50/50 (Na_0.5Bi_0.5TiO₃) was prepared by a sol-gel processing method. The structure and microstructure of the precursor gel as well as the ferroelectric, pyroelectric, dielectric and piezoelectric properties of the BNT were studied. BNT crystallized in the rhombohedra perovskites structure Na_0.5Bi_0.5TiO₃ was obtained from the precursor gel by heating at 700 °C for 2 h in air. The BNT ceramic at 1100 °C sintering temperature present high crystallinity, good dielectric properties at 1 kHz (ε′=885, tan δ=0.03, T_c=370 °C), piezoelectric properties (k₃₃=0.39, c₃₃=105 GPa, e₃₃=12.6 C/m², d₃₃=120 pC/N), high remnant polarization (P_r=47 μC/cm²) and pyroelectric coefficient ($p$=707 μC/m² K) and low coercive field (E_c=55 kV/cm). Hence, the BNT prepared by sol-gel method could be used for silicon based memory device application where a low synthesis temperature is a key requirement.     

Effect of MnO2 on the dielectric and piezoelectric properties of alkaline niobate based lead free piezoelectric ceramics

Lead free ferroelectric ceramics of the KNN–LiTaO₃–LiSbO₃ system were prepared using the mixed oxide route. This work reports the effect of doping (K_0.44Na_0.52Li_0.04)(Nb_0.86Ta_0.1Sb_0.04)O₃ produced through the conventional solid state sintering method with different amounts of MnO₂. With 1 mol% of the dopant, ～96.5% of the theoretical density of the ceramics was achieved while grain growth inhibition was attained through pinning of the grain boundary movement. A polymorphic phase transition (PPT) was induced in the ceramic from the orthorhombic crystal structure to the tetragonal structure with increasing dopant amount. At lower temperatures, the doped samples had higher epsilon values but there was a decrease in both T_c (from 333 °C to 249 °C) and epsilon value at T_c (from ≈9500 to <6000). At temperatures below 300 °C however, the loss tangent in the doped samples (≈2.5 mol%) was much lower and steady when compared to the undoped one. The ferroelectric properties were slightly lowered with the addition of MnO₂. The remnant polarisation (P_r) was lowered from ～18 μC/cm² to ～9 μC/cm², the coercive field (E_c) from ～8.5 kV/cm to ～6.2 kV/cm and the piezoelectric charge coefficient (d₃₃) decreased as well.     

Influence of the electrohydrodynamic process on the properties of dried button mushroom slices: A differential scanning calorimetry (DSC) study

In this paper, drying of button mushroom (Agaricus bisporus) slices with an innovative drying technique of hot air combined with Electrohydrodynamic (EHD) drying process was investigated at three electrode gaps (5, 6, and 7 cm) and voltage levels (17, 19, and 21 kV). The effects of different hot air combined with EHD drying treatments on the temperature of the mushroom slices, drying time, final color and protein denaturation features including enthalpy (ΔH), onset temperature (T_o), peak transition temperature (T_p), conclusion temperature (T_c), and temperature range (T_c–T_o) of endothermic peaks were systematically evaluated. In addition, water state changes in DSC cooling thermograms of dried mushroom slices were investigated. The results obtained by differential scanning calorimetry showed that the ΔH values in the DSC traces of the EHD-dried mushroom slices were reduced with a decrease in the electrode gap and an increase in the voltage. Specifically, among voltages of 21, 17, and 19 kV, a voltage of 21 kV resulted in the lowest ΔH and T_c–T_o values and the highest T_p and T_o values. This result indicated that voltage had a significant effect on these responses. Similarly, the DSC results showed a considerable effect of high electric field intensity on ΔH, T_c–T_o and T_p responses related to protein denaturation in comparison to low electric field intensity.     

Reactions of benzophenone imine complex [Tp(NH═CPh2)(PPh3)Ru–Cl] with alkyne and dimerization of terminal alkynes in the presence of Et3N

Treatment of benzophenone imine complex [Tp(PPh₃)(NH═CPh₂)Ru–Cl] (1) {Tp═HB(pz)₃, pz = pyrazolyl} with 4-Ethynyltoluene in the presence of H₂O in distilled ethanol afforded the chelate alkenyl ketone complex [Tp(PPh₃)RuCCH₂(p-MeC₆H₄)═CHC(O)(p-MeC₆H₄)] (2). On the other hand, reaction of 1 with HC≡C(O)OR₁ in R₂OH produced the chelate vinyl ether complexes [Tp(PPh₃)Ru–C(OR₂)═CHC(O)OR₁] (3a, R₁ = Me, R₂ = Me; 3b, R₁ = Et, R₂ = Me; 3c, R₁ = Et, R₂ = Et; 3d, R₁ = Me, R₂ = Et), respectively. Preliminary results on the catalytic activity of 1 are also presented. Intriguingly, complex 1 is found to catalyze the dimerization of terminal alkynes HC≡CR (R = p-MeC₆H₄, C(O)OCH₃) in the presence of Et₃N to give eynes. The structures of 3c and 3d have been determined by X-ray diffraction analysis.     

Voltammetric investigation of iron(III) complexes with siderophore chrysobactin in aqueous solution

Voltammetric investigations of iron(III)–chrysobactin complexes in aqueous solution at static mercury electrode, were performed. With c_Fe = (0.5–30) × 10^?7 mol dm^?3 and c_Cb = (0.5–100) × 10^?7 mol dm^?3 in pH range 6.7–10, reduction peaks with E_p ?0.64 to ?0.74 V (1) and E_p ?0.50 to ?0.62 V (2) vs. Ag/AgCl, were registered. These reduction processes were time dependent as well as solution composition (c_Fe, c_Cb and pH). Complexes are adsorbed at the mercury drop surface. Presumed stoichiometry of the detected complexes was Fe^IIICb₃ (1) and Fe^IIICb₂(OH)_x (2). Their formation/dissociation processes were described. These investigations are of biological importance as well, since provide an insight into possible reduction mechanism in the bacterial cells that use chrysobactin to acquire the iron.     

Determination of surface area of carbon-black by simple cyclic-voltammetry measurements in aqueous H2SO4

Determination of the surface area of commercial carbon-black (CB) by cyclic-voltammetry (CV) measurements of the electrochemical double-layer charge (Q) in aqueous sulfuric acid was investigated. Various factors that affect the Q value associated with CB, including: the presence of redox-reversible function-groups, the binders used for the formation of thin-film CB electrodes, the scan rates of the CV measurement, H₂SO₄ electrolyte concentration and the volume of air contained in the pores of the CB samples were examined. Conditions for measuring Q without interference from these factors were investigated and the data derived, without interference, was found to correlate well with the surface area of the CB. The results show that the total Brunauer–Emmett–Teller (BET) surface area shows good correlation (R² = 0.993) with the Q value corresponding to a full charge/discharge of the CB (Q₀), obtained by extrapolation at a zero scan rate; additionally, the CB micropore surface area (diameter < 2 nm) shows good linear correlation with the Q deficiency (Q₀–Q), measured at 5 mV s^?1 (R² = 0.998).