Interaction of colloidal AgTiO2 nanoparticles with bovine serum albumin

The interaction between colloidal AgTiO₂ nanoparticles and bovine serum albumin (BSA) was studied by using absorption, steady state, time resolved and synchronous fluorescence spectroscopy measurements. Absorption spectroscopy proved the formation of a ground state BSA?AgTiO₂ complex. Upon excitation of BSA, colloidal AgTiO₂ nanoparticles effectively quenched the intrinsic fluorescence of BSA. The number of binding sites (n = 1.06) and apparent binding constant (K = 3.71 × 10⁵ M⁻¹) were calculated by the fluorescence quenching method. A static mechanism and conformational changes of BSA were observed.     

Study on the Langmuir aggregation of fluorinated surfactants on protein

The microphase adsorption-spectral correction (MPASC) technique was described and applied to the study of the interactions of fluorinated surfactants such as potassium perfluorooctanesulfonate (PFOS) and potassium perfluorobutanesulfonate (PFBS) with human serum albumin (HSA). Sodium octanesulfonate (SOS) was also studied as non-fluorinated surfactant. The aggregation of PFOS, PFBS and SOS obeys the Langmuir monolayer adsorption. The results show that the adsorption ratios of surfactants to HSA are PFOS:HSA = 120:1, PFBS:HSA = 205:1 and SOS:HSA = 18:1. The adsorption constants are K_PFOS-HSA = 5.01 × 10³, K_PFBS-HSA = 9.79 × 10² and K_SOS-HSA = 4.03 × 10³. The detection limits are 2.7 mg/L for BSA using PFOS, 3.1 mg/L using PFBS and 3.1 mg/L using SOS. It was found that fluorinated surfactant exhibited stronger interaction with protein than hydrogenated one, and fluorinated surfactant with long hydrophobic chain exhibited stronger interaction with protein than that with short hydrophobic chain.     

Detection of cationic guest molecules by quenching of luminescence of a self-assembled host molecule consisting of terbium(III) and calix[4]arene-p-tetrasulfonates

By self-assembly in aqueous solution, calix- (CAS) and thiacalix[4]arene-p-tetrasulfonate (TCAS) formed luminescent complexes Tb^III·(CAS)₂ and Tb^III·TCAS, respectively, which were utilized as a host for cationic guests. Addition of 1-ethylpyridinium guest quenched luminescence of Tb^III·(CAS)₂ in accordance with the Stern-Volmer (SV) relation with a low detection limit (D.L.) of 5.94 × 10⁻⁸ M (S/N = 3, M ≡ mol dm⁻³). On the other hand, 1-ethylquinolinium quenched luminescence of Tb^III·TCAS most efficiently, affording a very low D.L. (6.71 × 10⁻¹⁰ M). The agreement of the SV coefficients obtained with luminescent intensity (K_SV,all = 6.74 × 10⁶ M⁻¹) and lifetime (K_SV,Tb = 6.50 × 10⁶ M⁻¹) implied that dynamic quenching of ⁵D₄ excited state of Tb^III was predominant in the quenching processes. The quenching rate was estimated to be k_q,Tb = 9.94 × 10⁹ M⁻¹ s⁻¹, which was as fast as diffusion-limited rate. Quenching of Tb^III·(CAS)₂ was also applied to detection of NAD⁺, with a D.L. of 2.78 × 10⁻⁷ M.     

A method for rapid screening of interactions of pharmacologically active compounds with albumin

We determine the association constants for ligand–protein complex formation using the flow injection method. We carry out the measurements at high flow rates (F = 1 mL min⁻¹) of a carrier phase. Therefore, determination of the association constant takes only a few minutes. Injection of 1 nM of the ligand (10 μL of 1 μM concentration of the ligand solution) is sufficient for a single measurement. This method is tested and verified for a number of complexes of selected drugs (cefaclor, etodolac, sulindac) with albumin (BSA). We obtain K = 4.45 × 10³ M⁻¹ for cefaclor, K = 1.00 × 10⁵ M⁻¹ for etodolac and K = 1.03 × 10⁵ M⁻¹ for sulindac in agreement with the literature data. We also determine the association constants of 20 newly synthesized 3β- and 3α-aminotropane derivatives with potential antipsychotic activity – ligands of 5-HT_1A, 5-HT_2A and D₂ receptors with the albumin. Results of the studies reported here indicate that potential antipsychotic drugs bind weakly to the transporter protein (BSA) with K ≈ 10²–10³ M⁻¹. Our method allows measuring K in a wide range of values (10²–10⁹ M⁻¹). This range depends only on the solubility of the ligand and sensitivity of the detector.     

Langmuir Aggregation of Coomassie Brill Blue on Protein and Determination of Protein by MPASC

The microphase adsorption–spectral correction technique (MPASC) has been applied to investigate the aggregation of coormassie brill blue G250 (CBBG) on protein in which the microelectrostatic fields exist. The Langmuir adsorption of CBBG in protein was confirmed, and the interaction is sensitive at pH 3.78. Results show that the adsorption ratio of CBBG to five proteins, e.g., BSA, OVA, Hb, Mb and -G are 100, 65, 30, 98 and 210, respectively, their adsorption constants are 9.92 × 10⁴, 8.04 x 10⁴, 9.38 × 10⁴, 1.66 × 10⁵, and 2.75 × 10⁴, and their absorptivities are 2.33 × 10⁶, 1.56 × 10⁶, 1.98 × 10⁶, 5.61 × 10⁵, and 4.48 × 10⁶ Lmol^–1 at 670 nm. The study indicates that 1 mg of protein adsorbs about 1.54 mmol of CBBG. For the protein determination of samples, the recovery of protein is between 88.0 and 111% and the relative standard deviation is 2.6%.     

Langmuir Aggregation of Chromophore in Biomacromolecule and its Application: Interaction of Picramine CA (PCA) with Proteins

The microphase adsorption-spectral correction (MPASC) technique has been described. The formation of microelectrostatic fields in macromolecule is proposed and it causes the aggregation of a chromophore in protein. We have studied the interaction of picramine CA (PCA) with five proteins: bovine serum albumin (BSA), human n -globulin ( n -G), bovine hemoglobin (Hb), horse myoglobin (Mb) and ovalbumin (OVA). Results show that at pH 2.21, the adsorption ratios of PCA to BSA, n -G, Hb, Mb and OVA are 46, 54, 35, 15 and 21, respectively, their adsorption constants 3.17 ‐ 10 5 , 6.58 ‐ 10 4 , 1.40 ‐ 10 5 , 8.99 ‐ 10 4 and 1.68 ‐ 10 5 and their absorptivities 3.56 ‐ 10 5 , 3.06 ‐ 10 5 , 2.91 ‐ 10 5 , 1.10 ‐ 10 5 and 1.97 ‐ 10 5 l mol m 1 cm m 1 at 630 nm. The analysis of samples has given the satisfactory result.     

A novel strapped porphyrin receptor for molecular recognition

A novel strapped porphyrin receptor Zn1, in which two electron-rich bis(p-phenylene)-34-crown ether-10 units are incorporated, has been designed and synthesized from the newly developed intermediate 7 for investigating new chemistry of molecular recognition. ¹H NMR and UV-Vis studies revealed that Zn1 displays relatively weak binding abilities to neutral electron deficient naphthalene-1,8,4,5-tetracarboxydiimide (NDI) derivatives 13 (no simple complexing stoichiometry was observed), 19 (K_a=48(±5) M⁻¹) and 30 (K_a=46(±5) M⁻¹) in chloroform-d, strong binding ability to pyridine derivative 25, (K_a=1.5(±0.12)×10³ M⁻¹) in chloroform, moderately strong binding ability to tetracationic compound 35·4PF₆ (K_a=475(±50) M⁻¹) in acetone-d₆, and very strong binding affinity to compound 22 (K_a=6.5(±0.7)×10⁵ M⁻¹), which consists of one pyridine and two NDI units, in chloroform. Remarkable cooperative effect of the intermolecular metal-ligand coordination and donor-acceptor interactions in complex Zn1·22 was observed by comparing the complexing behaviors between Zn1 and the appropriately designed guests. Complex Zn1·22 possesses an unique three-dimensional tri-site binding feature. For comparison, the complexing affinity of 1 toward compounds 13, 19, and 30 in chloroform-d and 35·4PF₆ in acetone-d₆ has also been investigated and the binding patterns in different complexes were explored. The results demonstrate that strapped porphyrin derivatives are ideal precursors for constructing new generation of three-dimensional multi-site artificial receptors for molecular recognition and host-guest chemistry.     

Tetrazole derivatives and matrices as novel cobalamin coordinating compounds

Cobalamin (Cbl, vitamin B₁₂) consists of two moieties: (i) the corrin ring with the central Co-ion in the oxidation states Co^3+/2+/1+ and (ii) the nucleotide side chain. The lower position of the ring is typically occupied by the nucleotide base (Bzm), whereas the upper surface coordinates exchangeable ligands. We have found that amino-tetrazole can coordinate to H₂O · Cbl (Co³⁺) with K_d = 10⁻⁵-10⁻⁶ M. A specific group (presumably tetrazole, TZ) can be easily created in CNBr-activated Sepharose by treatment with . The prepared matrix (STZ) contained ≈10 mM of the active groups, which bound H₂O · corrinoids with K_d = 10⁻⁵-10⁻⁶ M. Stability of STZ-Cbl bonds gradually increased and reached K_d = 10⁻⁷ M over 10-20 h (20 °C, pH 6-7). This effect can be ascribed to partial displacement of Bzm and coordination of TZ to the lower position. The binding was most efficient at pH 4-7 and low ionic strength, yet, noticeable adsorption took place even at extreme conditions, pH 1-9 and I = 0-2 M. Reduced corrins (Co²⁺) also exhibited high affinity for STZ. The bound ligands could be eluted as H₂O · Cbl (pH 0), HO · Cbl (pH 14) or diCN · Cbl (pH 9-12, CN⁻). The adsorbent is applicable for one-step purification of corrins from a crude extract; separation of aquo- and diaquo-forms; specific capturing of H₂O · Cbl from a mixture containing organo-Cbls or protein-bound Cbl, analysis of peptide-Cbl dissociation kinetics, etc.     

Thermodynamic Studies on NdFeO3(s)

The enthalpy increments and the standard molar Gibbs energy of formation of NdFeO₃(s) have been measured using a high-temperature Calvet microcalorimeter and a solid oxide galvanic cell, respectively. A λ-type transition, related to magnetic order-disorder transformation (antiferromagnetic to paramagnetic), is apparent from the heat capacity data at ∼687 K. Enthalpy increments, except in the vicinity of transition, can be represented by a polynomial expression: {H°_m(T)−H°_m(298.15 K)}/J·mol⁻¹ (±0.7%)=−53625.6+146.0(T/K) +1.150×10⁻⁴(T/K)² +3.007×10⁶(T/K)⁻¹; (298.15≤T/K ≤1000). The heat capacity, the first differential of {H°_m(T)−H°_m(298.15 K)} with respect to temperature, is given by C^o_{p, m}/J·K⁻¹·mol⁻¹=146.0+2.30×10⁻⁴(T/K)−3.007×10⁶(T/K)⁻². The reversible emf's of the cell, (−) Pt/{NdFeO₃(s) +Nd₂O₃(s)+Fe(s)}//YDT/CSZ//{Fe(s)‘FeO’(s)}/Pt(+), were measured in the temperature range from 1004 to 1208 K. It can be represented within experimental error by a linear equation: E/V:(0.1418±0.0003)−(3.890±0.023)×10⁻⁵(T/K). The Gibbs energy of formation of solid NdFeO₃ calculated by the least-squares regression analysis of the data obtained in the present study, and data for Fe_0.95O and Nd₂O₃ from the literature, is given by Δ_fG°_m(NdFeO₃, s)/kJ·mol⁻¹(±2.0)=−1345.9+0.2542(T/K); (1000≤T/K ≤1650). The error in Δ_fG°_m(NdFeO₃, s, T) includes the standard deviation in emf and the uncertainty in the data taken from the literature. Values of Δ_fH°_m(NdFeO₃, s, 298.15 K) and S°_m(NdFeO₃, s, 298.15 K) calculated by the second law method are −1362.5 (±6) kJ·mol⁻¹ and 123.9 (±2.5) J·K⁻¹·mol⁻¹, respectively. Based on the thermodynamic information, an oxygen potential diagram for the system Nd-Fe-O was developed at 1350 K.     

Spectrometric study of the interaction between Alpinetin and bovine serum albumin using chemometrics approaches

The binding interaction of Alpinetin (APT) with bovine serum albumin (BSA) was studied by fluorescence, UV-visible and synchronous fluorescence spectroscopy (SFS) under simulated physiological conditions. The measured complex spectra were resolved by multivariate curve resolution-alternating least squares (MCR-ALS), yielding a host of data and information, which otherwise would have been impossible to obtain. The extracted profiles corresponded to the spectra of the single species in the APT/BSA mixture. In addition, the presence of the APT-BSA complex was demonstrated, and it was shown that the associated quenching of the fluorescence from the BSA protein resulted from the formation of APT-BSA complex via a static mechanism. The binding constant (K_a(ave) = 2.34 × 10⁶ L mol⁻¹) and the number of sites (n = 1) were obtained by fluorescence methods as were the thermodynamic parameters (ΔH⁰, ΔS⁰ and ΔG⁰). This work suggested that the principal binding between APT to BSA was facilitated by hydrophobic interactions. The thermodynamic parameters for APT were compared to those from the structurally similar Chrysin and Wogonin molecules. It appeared that the entropy parameters were relatively more affected by the small structural changes. SFS from the interaction of BSA and APT showed that the ligand affected the conformation of BSA. The competitive interaction of APT and site makers with BSA indicated site I as the binding area of APT in BSA.     

Solubility products for aminocarboxylate ligands: determination, validation and speciation uses

A method combining glass electrode potentiometry and computer simulation of speciation is described and used to determine the solubility product for S,S′-ethylenediamine disuccinate (EDDS) (also known as ethylenediiminodibutanedioic acid). This previously unpublished constant is validated by re-measuring K_sp for isomeric EDTA⁴⁻·H₄⁺ and by a linear free energy relationship. For EDDS⁴⁻·H₄⁺, log K_sp=−25.75±0.30.     

Heat-capacity measurements and thermodynamic functions of crystalline adenine; revised thermodynamic properties of aqueous adenine

The standard molar heat capacity C^°_p,m of adenine(cr) has been measured using adiabatic calorimetry over the range 6<(T/K)<310 and the results used to derive thermodynamic functions for adenine(cr) at smoothed temperatures. At T=298.15 K, C^°_p,m=(142.67±0.29) J · K⁻¹ · mol⁻¹ and the third law entropy S^°_m=(145.62±0.29) J · K⁻¹ · mol⁻¹. The standard molar Gibbs free energy of formation Δ_fG^°_m at T=298.15 K for crystalline adenine was calculated, using the standard molar enthalpy of formation for the compound and entropies of the elements from the literature, and found to be Δ_fG^°_m=(301.4±1.0) kJ · mol⁻¹. The results were combined with solution calorimetry and solubility measurements from the literature to yield revised values for the standard molar thermodynamic properties of aqueous adenine at T=298.15 K: Δ_fG^°_m=(313.4±1.0) kJ · mol⁻¹, Δ_fH^°_m=(129.5±1.4) kJ · mol⁻¹, and S_m^°=(217.68±0.44) J · K⁻¹ · mol⁻¹.     

Photometrisch-potentiometrische Bestimmung der Hydrolysenkonstanten vonN-Bromverbindungen

The equilibrium concentrations of all reaction products emerging from the hydrolysis ofN-bromo compounds in the presence of bromide and thereby also the hydrolysis constants (K ₁) have been calculated from the absorbance at 392.8 nm, thepH-value and the initial concentrations of theN-bromo compound and the bromide. The following compounds have been investigated:N-bromo-succinimide:K ₁=2.2·10^–6, 1,3-dibromo-5,5-dimethylhydantoin:K ₁=1.7·10^–5,N-bromoacetamide:K ₁=1.8·10^–6,N-bromo-monochloroacetamide: 5.2·10^–6,N-bromo-dichloroacetamide:K ₁=8.9·10^–6 andN-bromo-trichloroacetamide:K ₁=1.8·10^–5. The precision of the method, which is mainly suited for weak hydrolizingN-bromocompounds (K ₁<10^–4) are discussed and the overall error of the calculated values was found to be in the range of ±5–12%. The reactivities in aqueous solution of the most frequently usedN-bromo compounds are compared by means of the calculated HOBr equilibrium concentrations. The differences to be expected on the basis of the latters are at concentrations >10^–5 mol/l rather great, while they can be neglected in very dilute solutions (-10^–6 mol/l).

     

Syntheses, topological analyses and photoelectric properties of Ag(I)/Cu(I) metal-organic frameworks based on a tetradentate imidazolate ligand

A new tetradentate imidazolate ligand 1,1′,1″,1′′′-(2,2′,4,4′,6,6′-hexamethylbiphenyl-3,3′,5,5′-tetrayl)tetrakis(methylene)(1H-imidazole) (L) and four Ag(I)/Cu(I) coordination polymers, namely [(MCN)₃L]_n (1: M=Ag; 2: M=Cu), and [(MSCN)₂L]_n (3: M=Ag; 4: M=Cu) are described. All four new coordination polymers were fully characterized by infrared spectroscopy, elemental analysis and single-crystal X-ray diffraction. Compound 1 features a 3D supramolecular framework constructed by 1D chains through inter-chain Ag-N(CN) and inter-layer Ag-N(L) weak interactions with an uninodal 6⁶ topology. Complex 2 presents a 3D framework characterized by a tetranodal (3,4)-connected (3·4·5·10²·11)(3·4·5·6·7·9)(3·6·7)(6·10²) topology. Complexes 3 and 4 are isostructural, and both have a 3D network of trinodal 4-connected (4·8⁵)₂(4²·8²·10²)(4²·8⁴)₂ topology. The luminescent properties for these compounds in the solid state as well as the possible ferroelectric behavior of 1 are discussed.     

Adsorption of a protein-porphyrin complex at a liquid-liquid interface studied by total internal reflection synchronous fluorescence spectroscopy

Interfacial analysis has attracted more and more attention owing to its fundamental and biological importance. Total internal reflection fluorescence (TIRF) spectroscopy is a useful method to study interfacial properties. The synchronous scanning fluorescence technique provides a selective tool to analyze a specific component in a complex system. The interaction and adsorption of bovine serum albumin (BSA) and meso-tetrakis(4-sulfonatophenyl)porphyrin (TPPS) at toluene-water interface were studied successfully by the coupling technique of total internal reflection synchronous fluorescence (TIRSF). New methods are provided for the determination of the critical micelle concentration (cmc), apparent adsorption equilibrium constant (K_ad) and maximum amount of adsorption (f_max) at the liquid-liquid interface. The results indicated that BSA could adsorb onto the toluene-water interface as a complex of BSA-TPPS in a ratio of 1:1 ratio based on Langmuir adsorption isothermal model. The cmc, apparent K_ad and f_max for BSA at pH 3.1 were determined to be 1.0 × 10⁻⁴ mol L⁻¹, 1.15 × 10⁵ L mol⁻¹ and 1.14 × 10⁻⁹ mol cm⁻², respectively.     

Low-temperature heat capacity and thermodynamic properties of endo-Tricyclo[5.2.1.0]decane

Endo-Tricyclo[5.2.1.0^2,6]decane (CAS 6004-38-2) is an important intermediate compound for synthesizing diamantane. The lack of data on the thermodynamic properties of the compound limits its development and application. In this study, endo-Tricyclo[5.2.1.0^2,6]decane was synthesized and the low temperature heat capacities were measured with a high-precision adiabatic calorimeter in the temperature range from (80 to 360) K. Two phase transitions were observed: the solid-solid phase transition in the temperature range from (198.79 to 210.27) K, with peak temperature 204.33 K; the solid-liquid phase transition in the temperature range from 333.76 K to 350.97 K, with peak temperature 345.28 K. The molar enthalpy increments, ΔH_m, and entropy increments, ΔS_m, of these phase transitions are ΔH_m=2.57 kJ · mol⁻¹ and ΔS_m=12.57 J · K⁻¹ · mol⁻¹ for the solid-solid phase transition at 204.33 K, and, Δ_fusH_m=3.07 kJ · mol⁻¹ and Δ_fusS_m=8.89 J · K⁻¹ · mol⁻¹ for the solid-liquid phase transition at 345.28 K. The thermal stability of the compound was investigated by thermogravimetric analysis. TG result shows that endo-Tricyclo[5.2.1.0^2,6]decane starts to sublime at 300 K and completely changes into vapor when the temperature reaches 423 K, reaching the maximal rate of weight loss at 408 K.     

Sub- and post-micellar catalytic and inhibitory effects of cetlytrimethylammonium bromide in the permanganate oxidation of phenylalanine

The kinetics of phenylalanine (phe) oxidation by permanganate has been investigated in absence and presence of cetlytrimethylammonium bromide (CTAB) using conventional spectrophotometric technique. The rate shows first- and fractional-order dependence on [MnO₄⁻] and [phe] in presence of CTAB. At lower values of [CTAB] (≤10.0 × 10⁻⁴ mol dm⁻³), the catalytic ability of CTAB aggregates are strong. In contrast, at higher values of [CTAB] (≥10.0 × 10⁻⁴ mol dm⁻³), the inhibitory effect was observed in absence of H₂SO₄. We find that anions (Br⁻, Cl⁻ and NO₃⁻) in the form of sodium salts are strong inhibitors for the CTAB catalyzed oxidation. Kinetic and spectrophotometric evidences for the formation of an intermediate complex and an ion-pair complex between phe and MnO₄⁻, CTAB and MnO₄⁻, respectively, are presented. A mechanism consistent with kinetic results has been discussed. Complex formation constant (K_c) and micellar binding constant (K_s) were calculated at 30 °C and found to be K_c = 319 mol⁻¹ dm⁻³ and K_s = 1127 mol⁻¹ dm⁻³, respectively.     

Electromigration of carrier-free radionuclides

Dependences of La(III) overall ion mobilities on concentrations of ox^2– and tart^2– anions of oxalic and tartaric acid in aqueous solutions of 0.01 overall ionic strength and temperature 298.1 K were obtained by direct measurements of electromigration of carrierfree¹⁴⁰La-lanthanum(III). Concentration stability constants K_n and individual ion mobilities u _i ^o of oxalate and tartrate complexes of La(III) have been calculated for nitrate and perchlorate electrolytes, respectively: [La(ox)]⁺, lg K₁=5.63(9), u⁰[La(ox)]⁺=1.95(15)·10^–4 cm²·s^–1·V^–1; [la(ox)₂]^–, lg K₂=4.05(19) u⁰[La(ox)₂]^–=–1.76(20)·10^–4 cm²·s^–1·V^–1; [La(tart)]⁺, lg K₁=4.40(5), u⁰[La(tart)]⁺=+1.99(18)·10^–4 cm²·s^–1·V^–1.Results are compared with literature data. Additional, limiting individual La³⁺ ion mobility was calculated: =+6.9(1)·10^–4 cm²·s^–1·V^–1 for pure water at 298.1 K.     

Electroanalysis of myoglobin and hemoglobin with a boron-doped diamond electrode

The electrochemical behavior of myoglobin (Mb) and hemoglobin (Hb) was investigated with a boron-doped diamond (BDD) electrode by cyclic voltammetry. In acetate buffer solutions, the oxygen reduction at the BDD electrode showed a very high overpotential while the reduction of Mb or Hb was observed in the more positive potential region. Owing to the electrocatalytic reaction of O₂ and the participation of H⁺ following the electrochemical reduction of ferric proteins, the voltammetric responses for Mb and Hb on the BDD electrode in the negative going scans became remarkable in acidic buffer solutions in air. The peak current was linearly proportional to the concentration of Mb in the range 1×10⁻⁶–2×10⁻⁵ M or the concentration of Hb from 1×10⁻⁶ to 1×10⁻⁵ M.     

Modeling of iron adsorption on HTTA-loaded polyurethane foam using Freundlich,Langmuir and D-R isotherm expressions

The sorption of Fe(III) at low pH range from 1 to 4.5 on open cell polyether type HTTA-loaded polyurethane foam has been carried out using batch technique. The optimum shaking time for 2.5· 10^–4M solution of Fe(III) was found to be 30 minutes. The concept of macropore and micropore nature of polyurethane foam sorbent offers unique advantages of adsorption. Freundlich and Langmuir adsorption isotherms are followed at low concentration range from 1·10^–4 to 3·10^–4M solution of Fe(III). The Freundlich constant (1/n=0.46±0.013 andK=9.16±1.39 mg·g^–1) and Langmuir isotherm constants(M=21.78 mg·g^–1 andb=88.41±9.731·g^–1) were established. The sorption mean free energyE=12.22±0.09 kJ·mol^–1 and loading capacityC _m =145.21±6.1 mg·g^–1 were evaluated using Dubinin-Radushkevich isotherm, which suggested that the adsorption mechanism was chemisorption.