Standard Entropy Change Research Articles

Role of carbonate electrolytes on interaction of quinolone drug with anionic surfactant at various temperatures: A conductometric study

AbstractThe role of different carbonate salts on the interaction of anionic surfactant sodium dodecyl sulfate (SDS) with employed quinolone antibiotic drug (ciprofloxacin hydrochloride [CFH]) was explosively inspected through measuring specific conductivity (κ) of the investigated system. The drug, CFH, is an excellent antibiotic for the treatment of different bacterial infections like skin, urinary tract, and respiratory infections. The estimated critical micelle concentrations (cmc) of SDS were observed to be dwindled in the attendance of electrolytes and cmc reduction continues with the escalation of the electrolyte's concentration. The magnitudes of cmc for the SDS + CFH mixture were reduced with the elevation of temperature in K2CO3 and CaCO3 medium while increased with the rise of the temperature in the Na2CO3 medium. The magnitudes of counterion binding to micelles (β) were increased with the increase of the concentration of Na2CO3 and K2CO3 up to definite value and then reduced with the increase of successive rise of concentration of both salts at all temperatures while decreased monotonically with the rise of electrolyte concentration in CaCO3 medium. The values of standard free energy ( ) were achieved to be negative in each case suggesting spontaneous self‐assembly formation. The standard entropy change ( ) along with enthalpy change ( ) was also assessed and discussed elaborately.

Use of Masson's and Jones–Dole equations to study different types of interactions of three pharmacologically important drugs in ethanol

AbstractThe volumetric and viscometric study of three allopathic drugs (sodium valporate, benzalkonium chloride, and losartan potassium) in ethanol solvent is reported here. This study was carried out at four different temperatures that is, from 288.15 to 318.15 K. The accurately measured density values were used to calculate partial molar volume at infinite dilution, solute–solute interaction parameter, Hepler's constant, partial molar expansivity constant, and isobaric thermal expansion coefficient. The viscosity measurements were carried out for the calculation of constants of Jones–Dole equation and to calculate different thermodynamic parameters of viscous flow which include standard free energy change, standard enthalpy change, and standard entropy change of viscous flow. All these viscometric and volumetric parameters are useful for understanding the different types of interactions of drugs in solution and to study the drug action in body. The results of both volumetric and viscometric studies showed that all drugs had structure promoting effect on solvent, existing of strong solute–solvent interaction, and very weak solute–solute interaction. For all these drugs, solvophobic interaction was found to be dominant over electrostriction. Viscometric studies also showed the existing of stronger solute–solvent interaction in ground state as compared to that in transition state.

Experimental Investigation of Thermodynamics, Kinetics, and Equilibrium of Nickel Ion Removal from Wastewater Using Zinc Oxide Nanoparticles as the Adsorbent

In the present study commercial zinc oxide (ZnO) nanoparticles in the size of 30 nm were utilized as an adsorbent for the removal of Ni (II) ion from synthetic waste aqueous solution. Adsorption capacity of ZnO for removing Ni (II) ions from aqueous solutions was measured at different pH, adsorbent dose, contact time, temperature and metal ion concentration. Moreover, adsorption isotherms, kinetics and thermodynamics were studied to understand the nature and mechanism of adsorption. ZnO nanoparticles were characterized by X-Ray diffract analysis(XRD),Fourier Transform Infrared Spectroscopy(FT-IR), scanning electron microscopy (SEM),energy dispersive X-ray spectroscopy(EDS) and Brunauer-Emmett-Teller (BET). The maximum amount of Ni (II) removal were found to be (98.71%) from its aqueous solutions by ZnO nanoparticles which was achieved at the evaluated optimum conditions. The experimental kinetic data were examined using the pseudo-second-order rate model with a high regression coefficient. The adsorption isotherm was well described to the equilibrium data by Langmuir isotherm model (R2=0.990). In addition, the calculated thermodynamic parameters, the standard Gibbs free energy ΔGo, the change in standard enthalpy ∆Ho and the standard entropy change ∆So showed that the adsorption of Ni (II) onto ZnO nanoparticles was feasible, endothermic and spontaneous respectively. The experimental results suggest that ZnO nanoparticles can be used as a potential adsorbent for the efficient removal of heavy metals from aqueous solutions than any other adsorbent because an economical and low- consumption energy due to its ambient operation conditions.

Thermodynamic and acoustic studies of quercetin with sodium dodecyl sulfate in hydro-ethanolic solvent systems: A flavonoid-surfactant interaction study

The thermodynamic and acoustic studies for well-known flavonoid; quercetin with an anionic surfactant sodium dodecyl sulfate (SDS) have been reported. The properties of micellar systems exhibiting various hydrophobic and hydrophilic interactions have been studied. The studies were performed in four different hydro-ethanolic concentrations i.e., aqueous, 30% v/v, 70% v/v and absolute ethanol at five different temperatures (293.15 K to 313.15 K with a difference of 5 K). Various parameters such as conductivity (κ), density (ρ), ultrasonic sound velocity (μ) and relative viscosity (ηr) were determined and resulting data was used to calculate the thermodynamic and acoustic parameters, namely, standard enthalpy change (ΔHom), standard entropy change (ΔSom), standard Gibbs energy change (ΔGom) of micellization, apparent molar volume (ϕv) and apparent molar compressibility (ϕk). Moreover, 1H NMR spectroscopic analysis of SDS and micelles was performed in order to confirm the location of quercetin in micellar structure of surfactant. These studies are helpful in investigating the extent of hydrophobic interactions within the system which might be utilized in determining a stable flavonoid-surfactant concentration in preparing pharmaceutical formulations.

Thermodynamic modelling, Hansen solubility parameter and solvent effect of oxaprozin in thirteen pure solvents at different temperatures

The solubility of oxaprozin in thirteen organic solvents (methanol (MeOH), ethanol (EtOH), n-propanol (n-PrOH), n-butanol (n-BuOH), n-pentanol (n-PeOH), methyl acetate (MeAC), ethyl acetate (EtAC), n-propyl acetate (n-PrAC), n-butyl acetate (n-BuAC), n-amyl acetate (n-AmAC), N,N-dimethylacetamide (DMAC), N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO)) was determined using a laser monitoring method at atmospheric pressure in this work. The measured temperature range for all selected solvents is 278.15 K to 323.15 K except DMSO 293.15 K to 323.15 K. Through the entire studied temperature range, the results turned out that oxaprozin solubility in selected solvents has a positive correlation with temperature variation. Four mathematical models were employed to correlate the solubility data including two empirical models (modified Apelblat model, λh model) and two activity coefficient models (UNIQUAC model, NRTL model), with the modified Apelblat model giving the best regression. Solubility order of oxaprozin in thirteen solvents was analysed by using the Hansen solubility parameter (HSP) and the solvent effect (solvent interaction) was investigated through correlating oxaprozin solubility in selected solvents based on KAT-LSER model. Moreover, according to van’t Hoff equation, thermodynamic properties including apparent standard molar enthalpy change (ΔsolH °), apparent standard molar Gibbs energy change (ΔsolG°) and apparent standard molar entropy change (ΔsolS) of the dissolution process of oxaprozin were also calculated and discussed.

Investigation on hydrogen dissociation pressure, heat of formation and strain energy of metal hydrides

Abstract We analyzed the relation among the dissociation pressure, the heat of formation, and the strain energy of metal hydrides, thermodynamically. Logarithm of hydrogen dissociation pressure PMH of alloy-based metal hydrides with different composition ratio linearly increased with the calculated bulk modulus of the hydrogen storage alloys Bc. The heat of formation ΔH0 also linearly increased with the calculated bulk modulus of the hydrogen storage alloys Bc. Those hydrogen dissociation pressure and the heat of formation were analyzed by the thermodynamic relations including strain energy. We obtained the following equation [dΔH0/dBc]/[d(RTln(PMH))/dBc] >1 for metal hydrides having different composition ratio. The value above 1 of this equation was based on the experimental results that the standard entropy change was proportional to the heat of formation of the metal hydride.

Thermodynamics of formation of solid solutions between BaZrO3 and BaPrO3

A linear relationship between the standard enthalpy of formation from binary oxides, ΔfHox, and the Goldschmidt tolerance factor, t, for some AIIBIVO3 (A = Ca, Sr, Ba; B = Ti, Zr, Hf, Ce, Pr, Tb, U, Pu, Am) perovskite oxides was used for estimation of ΔfHox of Pr-substituted barium zirconates BaZr1–xPrxO3. A dependence of the relative change of the standard entropies, S298, on the relative change of the molar volumes in the reactions of formation of AIIBIVO3 (A = Ca, Sr, Ba; B = Ti, Zr, Hf, Ce) from binary oxides was also found to be linear. Using this dependence, a relatively precise method of estimating S298 was proposed, and S298 of BaPrO3 was calculated as (162.8 ± 2.8) J·mol-1·K-1. Knowing S298 of BaPrO3 and using the literature data for S298 of BaZrO3, the values of S298 of BaZr1–xPrxO3 were predicted on the assumption that BaZr1–xPrxO3 is a regular or ideal solution of BaPrO3 in BaZrO3 as evidenced by the very small enthalpy of mixing calculated based on the estimated ΔfHox. The values of standard entropy changes, ΔfSox, and Gibbs energy changes, ΔfGox, for the reactions of formation of BaZr1–xPrxO3 from BaO, ZrO2 and PrO2 were also estimated. Substituting Pr for Zr in BaZr1–xPrxO3 results in ΔfHox and ΔfGox becoming more positive, indicating the decrease of the relative stability with respect to the corresponding binary oxides. Expanded uncertainties of the estimated values of ΔfHox and ΔfGox are equal to 14 kJ∙mol-1, and those of S298 and ΔfSox – less than 2.8 J∙mol-1·K-1 and 3.5 J∙mol-1·K-1, respectively, for BaZr1–xPrxO3 (x = 0.0–1.0).

Green Synthesis of S- and N-Codoped Carbon Nanospheres and Application as Adsorbent of Pb (II) from Aqueous Solution

In this paper, green and facile synthesis of sulfur- and nitrogen-codoped carbon nanospheres (CNs) was prepared from the extract of Hibiscus sabdariffa L by a direct hydrothermal method. Finally, sulfur-carbon nanospheres (CNs) were used as the adsorbent to remove Pb+2 ions from aqueous solutions because of the high surface area of S-CNs from CNs and N-CNs. The synthesized nanospheres were examined by Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), field emission scanning electron microscopy, transmission electron microscopy (TEM), and nitrogen adsorption-desorption isotherms. The results show spherical shapes have a particle size of up to 65 nm with a high surface area capable of absorbing lead ions efficiently. Additionally, the factors affecting the process of adsorption that include equilibrium time, temperature, pH solution, ionic intensity, and adsorbent dose were studied. The equilibrium removal efficiency was studied employing Langmuir, Freundlich, and Temkin isotherm forms. The kinetic data were analyzed with two different kinetic models, and both apply to the adsorption process depending on the values of correlation coefficients. The thermodynamic parameters including Gibbs free energy (ΔG°), standard enthalpy change (ΔH°), and standard entropy change (ΔS°) were calculated for the adsorption process.

Preparation and utilization of cigarette filters based activated carbon for removal CIP and SDS from aqueous solutions

The smoked cigarette filters were used to prepare high-surface-area activated carbons by KOH activation. The highest BET specific surface area of cigarette-filters-based activated carbon (CFAC) was 2726 m2·g−1 obtained at the activation parameter of carbonized materials/KOH = 1:5 and activation temperature of 900 °C, which could concluded that smoked cigarette filters were excellent raw materials for preparation activated carbons. The ciprofloxacin (CIP) and Sodium dodecyl sulfat (SDS) adsorption isotherms, adsorption kinetics and adsorption thermodynamics from aqueous solution using cigarette filters based activated carbon were investigated. The results indicated that Langmuir model and pseudo-second-order models were suitable to describe the CIP and SDS adsorption process of CFAC. More negative standard free energy (ΔG) and positive entropy change (ΔS) of CIP adsorption with increasing temperature indicated the spontaneous nature and increasing randomness of the CIP adsorption process. While More positive ΔG and negative ΔS of SDS adsorption indicated the non-spontaneous processes. The both positive enthalpy change (ΔH) indicated endothermic of CIP and SDS adsorption process.

Fabrication of a novel hybrid biocomposite based on amino-thiocarbamate derivative of alginate/carboxymethyl chitosan/TiO2 for Ni(II) recovery

A novel hybrid biocomposite based on amino-thiocarbamate derivative of alginate, carboxymethyl chitosan and TiO2 (TiO2/TSC-CMC) was fabricated and characterized using Fourier transform Infrared spectroscopy (FTIR), Scanning electron microscopy (SEM) and Energy dispersive X-ray spectroscopy (EDX). The TiO2/TSC-CMC mass ratio (5.0–30.0%) was optimized and 3TiO2/TSC-CMC (hydrogel beads with TiO2/TSC-CMC mass ratio of 20.0%) was selected as the best sorbent for effective biosorption of Ni(II). Batch sorption experiments were conducted, instantaneous and equilibrium sorption capacities were investigated as function of pH, sorbent dose, initial metal concentration, contact time and temperature. Kinetic data could be well explained through pseudo second order rate equation (PSORE) depicting that the rate determining step involves the transfer of electron density from sorbent functional sites to central metal ion. Langmuir model fitted well with isothermal sorption data and maximum monolayer sorption capacity (qm) was computed as 172 mg/g at pH 6.0 and temperature 298 K. The values of thermodynamic parameters such as standard enthalpy change (16.94 kJ/mol) and standard Gibbs energy change (−18.67, −19.48, −20.57, and −21.38 kJ/mol) and standard entropy change (0.12 kJ/mol·K) concluded that sorption process is endothermic, spontaneous and resulted with increase in randomness. Hence, 3TiO2/TSC-CMC was found efficient and reusable sorbent.

Correlations between Thermodynamics and Structure of Carbonic Anhydrase-Inhibitor Binding

The fundamental principles that determine the affinity between a protein and a small compound are not well understood. Therefore, novel pharmaceuticals are often discovered by performing laborious and expensive high-throughput random screens while the rational protein-target structure-based drug design is complicated and compound structures are difficult to be discovered in silico. We investigate a family of twelve structurally similar human proteins, carbonic anhydrases (CAs), and their inhibitors, aromatic compounds with a pharmacophoric sulfonamide group. This system is suitable both as a model for biophysical understanding of protein-small compound interactions and also a new inhibitor could have a potential to be clinically applicable. Our aim is to correlate the crystal structures with the binding thermodynamic parameters (change in standard enthalpy, entropy, and Gibbs energy upon binding) between the protein and small molecule. We have determined a number of examples where the influence of water molecules on binding, steric interference, the influence of halogen atoms of compound and other structurally distinct effects have been demonstrated. Testing of chemically similar compound binding to CAs gives an opportunity to track changes of binding affinity and selectivity. Despite the similarity between CA isoforms, we have come to understand some rules on how to design compounds with pM affinity and high selectivity for certain CA isoforms.

Investigation of interactions between quercetin and Tween 80 through electrolyte induced thermodynamic approach

The research work represents the thermodynamic studies of well known flavonoid quercetin in presence of non-ionic surfactant Tween 80. The studies were performed in hydro-ethanolic solvent system (30% v/v ethanol) at five different temperatures (20–40 °C with difference of 5 °C) in order to analyze the changes in thermodynamic properties with respect to temperature change. As Tween 80 is non-ionic surfactant, 1% sodium chloride solution was added as an electrolyte to ensure the flow of electrons. The conductance studies for the flavonoid-surfactant system were carried out and the data thus obtained was utilized to calculate various thermodynamic parameters i.e. standard enthalpy change (ΔHom), standard entropy change (ΔSom) and standard Gibbs free energy change (ΔGom) of micellization. Overall, the effects of quercetin on micellization process of Tween 80 at different temperatures and hydro-ethanolic solvent have been reported.

New Insights into the Partitioning of Phenothiazine Dyes in Aqueous Two-Phase Systems

Aqueous two-phase systems (ATPSs) have proven to be efficient and environmentally safe methods for extracting chemical species. However, the driving forces behind the partition of solutes in these systems are still little understood. A complete thermodynamic partitioning of phenothiazine dyes was investigated in poly(ethylene oxide) (PEO) + salt + water ATPSs. Standard transfer parameters (Gibbs free energy change (ΔtrGo), enthalpy change (ΔtrHo) and entropy change (TΔtrSo)) were evaluated, and their dependence on the dye structure, electrolyte nature and tie line length (TLL). All phenothiazine dyes are concentrated predominantly in the polymer enriched phase, with ΔtrGo values ranging from -4.1 up to -13.4 kJ mol-1. Due to the dye-PEO attractive interactions that occur mainly via benzene condensed ring present in the structures of phenothiazine dyes, the partitioning of these dyes was enthalpically driven, with -11.4 ≥ ΔtrHo ≥ -52 kJ mol-1 and -4.93 ≥ TΔtrSo ≥ -38 kJ mol-1.

Thermodynamic analyses of the orthorhombic-to-tetragonal phase transition in Pr2-xNdxNiO4+δ under controlled oxygen partial pressures.

The behavior of the structural orthorhombic-tetragonal phase transition of Pr2-xNdxNiO4+δ, a candidate material for solid oxide fuel cells and oxygen permeation membranes, was investigated by differential scanning calorimetry and thermogravimetry (TG), under controlled oxygen partial pressures, P(O2). The structural phase transition temperature, TP, of Pr2-xNdxNiO4+δ increased with increasing Nd content, x, or increasing P(O2). The phase transitions of all compositions involved discrete variations in the oxygen content, Δδ, which were observed in the TG curves under various P(O2) values. Δδ of Pr2-xNdxNiO4+δ with 0.5 ≤x≤ 1.5 were between those of Nd2NiO4+δ and Pr2NiO4+δ, regardless of P(O2), and were slightly increased with decreasing P(O2). It was proposed that the effect of the valence change of the Pr ion on Δδ was decreased with increasing Nd content. The standard enthalpy change, ΔH°, and entropy change, ΔS°, of the phase transition were estimated from the Ellingham diagrams and van't Hoff plots, which were prepared from the relationship between P(O2) and TP using an ideal solution model. ΔS° was decreased with increasing Nd content for the specimens with 0.0 ≤x≤ 1.5. The ΔH° of Pr2-xNdxNiO4+δ with 0.0 ≤x≤ 1.5 was almost constant for all Nd contents. The increase in the phase transition temperature of Pr2-xNdxNiO4+δ with increasing x from 0.0 to 1.5 was successfully explained using the calculated values of ΔH° and ΔS°.

Adsorption Study of Rhodamine B and Methylene Blue Dyes with ZSM-5 Directly Synthesized from Bangka Kaolin without Organic Template

Rhodamine B (RB) and Methylene Blue (MB) dyes adsorption using adsorbent ZSM-5 synthesized from Bangka kaolin were investigated in this study. The effects of the initial concentration, contact time and temperature on the adsorption process were also analyzed. The effect of the initial concentration and contact time played an important role in the adsorption process; however, the effect differs significantly in both dyes. The temperature plays little role in the dye adsorption process. The results showed the adsorption process occurred in ZSM-5 adhere to Langmuir isothermal adsorption model showing that the adsorption process occurred to be monolayer. Based on the kinetics studies, the pseudo-first-order kinetic model represents the adsorption kinetics that occurs for both dyes onto the synthesized ZSM-5. Thermodynamic parameters namely Gibbs free energy (ΔG°), standard entropy changes (ΔS°) and standard enthalpy (ΔH°) reveal that the adsorption process onto ZSM-5 for both dyes was spontaneous and exothermic.

Solubility of ketoconazole in the binary mixtures of 2-propanol and water at different temperatures

In the present study, the solubility of ketoconazole is measured by a shake – flask method in the binary solvent mixtures of 2-propanol + water at different temperatures. The experimental solubility data are correlated/back-calculated by some cosolvency models i.e. van't Hoff, Yalkowsky, Jouyban-Acree, Jouyban-Acree-van't Hoff, the mixture response surface and the modified Wilson models. Moreover, the density of ketoconazole saturated solutions is fitted by Jouyban-Acree model and the obtained equation is reported. The accuracy of these models is investigated by calculation of the corresponding MRD%. The apparent thermodynamic parameters including dissolution standard enthalpy change (ΔH∘), standard entropy change (ΔS∘), Gibbs free energy change (ΔG∘) for ketoconazole dissolution are calculated by using van't Hoff and Gibbs equations. Moreover, the preferential solvation analysis demonstrates that ketoconazole is preferentially solvated by water in water-rich and in 2-propanol-rich mixtures, but preferentially solvated by 2-propanol in mixtures of composition 0.19 < x1 < 0.58.

Inclusion complexation of novel synthesis amino acid based ionic liquids with β-cyclodextrin

Inclusion complex formation between amino acid based ionic liquids (AAILs) i.e., 1-(2-(octylamino)-2-oxoethyl)pyridin-1-ium bromide and 4-((hydroxyimino)methyl)-1-(2-(octylamino)-2-oxoethyl)pyridin-1-ium bromide into β-cyclodextrin have been investigated in solution. The inclusion complexes (ICs) of AAILs with β-CD were synthesized through the co-precipitation method. The solid IC formation is characterized by numerous analytical techniques, primarily by UV–vis spectroscopy and secondary by major techniques i.e., FT-IR and 1H NMR. The binding constant and 1:1 stoichiometric of ICs nature of the complex between AAILs and β-CD in solution were determined by Job's plot method using UV–vis spectroscopy. As results suggest, the binding constants of ICs are higher for OAOEPB-β-CD as compared to HIMOAOEPB-β-CD. The different thermodynamic parameters such as change in standard Gibbs free energy (ΔG0), standard enthalpy changes (ΔH0) and standard entropy change (ΔS0) have been estimated with the help of van't Hoff equation. Noteworthy changes of IR stretching frequency also support the IC formation. 1H NMR results suggest that the tail part of AAILs is more suitably included inside the hydrophobic cavity of β-CD and it shows 1:1 stoichiometric ICs formation.

In-vitro binding analysis of bovine serum albumin with sulindac/chlorpromazine: Spectroscopic, calorimetric and computational approaches

The current study was undertaken to explore the bindingof sulindac (SDC), and chlorpromazine (CPZ) with the bovine serum albumin (BSA) by fluorescence, isothermal titration calorimetric (ITC), UV–visible, site marker, circular dichroism (CD), and molecular docking studies. The fluorescence intensity of native BSA was quenched on increasing concentration of SDC/CPZ in a static manner. The thermodynamic parameters, association constant (Ka), standard enthalpy change (∆H°), standard entropy change (∆S°) and standard Gibbs free energy change (∆G°) were obtained from ITC. Site marker experiment highlighted that SDC/CPZ binds at Sudlow's site I by using warfarin and ibuprofen probes for site I and site II, respectively. The distance between donor, BSA and acceptor, SDC/CPZ was calculated by applying the FRET theory. Alteration in the secondary structure of BSA by SDC/CPZ was revealed by UV–vis, synchronous and 3D fluorescence studies. The stability of native BSA increases and decreases, respectively in the presence of SDC and CPZ as shown by CD spectroscopy. Molecular docking was performed to further confirm the binding site, amino acid residues and type of interactions involved in the binding process. This study provides an insight into interaction at molecular level between SDC/CPZ and BSA and will help to understand the thermodynamics and mechanism of drug binding.

Cadmium (II) Adsorption from Aqueous Solutions Using Onion Skins

The potential of onion skins for removal of aqueous Cd(II) was investigated. Onion skin powder was chemically modified using thioglycolic acid to develop a suitable, low-cost, and efficient adsorbent for the removal of Cd(II) from aqueous solutions. Influences of temperature, contact time, initial concentration of Cd(II), adsorbent dosage, and pH on the removal of Cd(II) were probed. Optimal adsorption conditions were found at pH 5 and 4, and at 60- and 30-min equilibrium time for the modified and native onion skins, respectively. The equilibrium process was well described by the Freundlich isotherm model. The maximum Cd(II) adsorption capacities, from the Langmuir model, are 17.86 mg/g (modified) and 21.28 mg/g (native). The adsorption process followed the mechanism of physisorption. Pseudo second-order rate equation fitted the kinetic data better than the pseudo first-order rate equation for the two adsorbents. Thermodynamic parameters, such as standard free energy change (ΔG°), standard enthalpy change (ΔH°), and standard entropy change (ΔS°), were calculated for adsorption experimental studies. The results showed that the adsorption of Cd(II) on native/unmodified and modified onion skins was a feasible process and exothermic under the studied conditions. The Cd(II) adsorbed was efficiently desorbed from adsorbent using 0.3 M HCl.

Fabrication of Reduced Graphene Oxide-Ag Nanocomposites and Analysis on the Interaction with BSA

Graphene is an excellent platform to support and stabilize silver nanoparticles (AgNPs). The reduced graphene oxide-silver nanoparticles (rGO-AgNPs) were synthesized by the chemical reduction method and characterized by using ultraviolet-visible (UV-vis) absorption, transmission electron microscopy (TEM), X-ray diffractometer (XRD), and scanning probe microscopy (SPM). The binding reaction of rGO-AgNPs with bovine serum albumin (BSA) was investigated by using fluorescence spectrometry and SPM. As the concentration of AgNPs increased, the fluorescence spectrum was quenched, and the quenching process of rGO-AgNPs and BSA was static quenching. Thermodynamic parameters of the absorption process were evaluated at different temperatures, and the negative values of Gibbs free energy ( Δ G ) showed that this process was spontaneous. The main type of interaction was hydrophobic interaction according to the values of changes in standard enthalpy ( Δ H ) and entropy ( Δ S ). In addition, the morphology changes of proteins interacting with nanomaterials were detected by SPM.