DDA Molecules Research Articles

Mechanism of sodium lauryl sulfate reducing froth stability of dodecylamine in hematite flotation: Experiments and molecular dynamics simulation

In this study, the influence of sodium lauryl sulfate (SLS) on the stability of dodecylamine (DDA) froth during the reverse flotation of hematite was investigated due to the frequent issue of excessively viscous foam leading to suboptimal reverse flotation outcomes. The research involved conducting flotation tests and two/three-phase froth stability assessments to explore how a specific molar ratio combination of DDA and SLS could enhance the flotation performance while simultaneously mitigating froth stability. The investigation into the mechanism by which SLS reduces the stability of DDA froth was aided by molecular dynamics simulations. The findings revealed that in the collector system comprising DDA and SLS, several key changes occurred at the molecular level. These included a decrease in the thickness of the electric double layer at the interface, a reduction in the thickness of the gas–liquid interface layer, weakening of the interaction strength between the head group and water molecules, a decrease in the coordination numbers of water molecules in the first hydration layer, and an enhanced migration ability of water molecules. Furthermore, there was an increased inclination angle between the head groups or molecular chains of the collector and the Z-axis, resulting in a diminished interaction depth between the head group and water and a closer positioning of the molecular tail chain to the gas–liquid interface with a more pronounced curvature. Consequently, these molecular adjustments led to a sparser arrangement of DDA molecules at the gas–liquid interface, lower coverage of the interface adsorption layer, and increased gas permeation, ultimately reducing DDA froth stability. The aforementioned conclusions provide a comprehensive molecular-level analysis of the principal mechanisms that can effectively reduce foam stability, including the attenuation of molecular head group-water interactions, reduction in gas–liquid interface layer thickness, decrease in gas–liquid interface orderliness, and enhancement of water molecule migration capability. The implications of this research extend to providing theoretical insights for addressing foam control challenges in DDA flotation processes.

Enhancement mechanism of polysorbate surfactant at solid/liquid and gas/liquid interfaces in magnesite tailings flotation desilication via MD and DFT calculations

To achieve the efficient flotation desilication of magnesite tailings (MT), this research systematically investigated the selective adsorption behavior of dodecylamine (DDA) and its compound collectors formed by mixing with Polysorbate surfactants and DDA. The investigation integrated experimental and simulation approaches. The results of the flotation experiment showed that the compound collector improved the MgO grade of the concentrate by 0.20% compared to DDA alone. Additionally, the SiO2 content was reduced by 1.04%, and the concentrate achieved a MgO grade of 41.95%. Molecular simulations provided new insights into the enhanced flotation mechanism with compound collectors, focusing on the size effect of collectors at the solid/liquid interface and bubble modification of collectors at the gas/liquid interface. The analysis indicates that small-size compound collectors can optimally utilise the collecting performance of individual DDA molecules, thereby effectively reducing reagent consumption per unit. Correlation tests indicate a notable enhancement in the hydrophobicity of the quartz surface subsequent to the application of the compound collector, suggesting that the compound collector exhibits a more solidophilic characteristic than DDA. The collectors of the compound facilitate the movement of water molecules on the bubble surface. This leads to a significant increase in the hydrophobicity of the bubble surface, which in turn increases the likelihood of bubble-particle contact collision and adhesion. Compared to DDA, the low dosage of compound collector has the potential to reduce costs and lay the foundation for industrial-grade MT flotation purification.

Selective flotation separation of fluorite from calcite using mixed anionic/cationic collectors

In this study, anionic/cationic collector sodium oleate (NaOL) mixed with dodecylamine (DDA) and salted water glass were used to separate fluorite from calcite. The flotation separation performance and underlying mechanism were researched by micro-flotation experiments, Fourier transform infrared (FTIR) analysis, wettability analysis, fluorescence spectrum analysis and atomic force microscopy (AFM). Micro-flotation experiment results show that the mixed anionic/cationic collectors (NaOL: DDA = 9:1) have strong flotation selectivity for two minerals, and the salted water glass can selectively depress calcite. This combined reagent system can achieve the separation of fluorite and calcite. The FTIR measurement results show that NaOL and DDA are co-adsorbed on the surface of fluorite, whereas only NaOL is adsorbed on the surface of calcite. The wettability analysis results show that the salted water glass hinders the adsorption of mixed collectors on the surface of calcite and selectively inhibits its flotation. The fluorescence spectrum analysis results show that the mixed collectors can produce large micelles, reduce the critical micelle concentration (CMC) and obtain greater molecular activity compared with a single collector. The AFM imaging results shows that single NaOL is uniformly adsorbed on the surface of fluorite. When using the mixed collectors, DDA molecules are interspersed amongst the molecules of NaOL to increase the hydrophobic end and make the surface of fluorite more hydrophobic. Based on these analyses, an adsorption model of the mixed collector NaOL/DDA on the mineral surface was drawn, which showed that the mixed collector produced a strong synergistic effect compared with a single collector. Therefore, it is more conducive to the separation of fluorite and calcite.

The Reactivity of CsPbBr3 Nanocrystals toward Acid/Base Ligands.

The interaction of lead bromide perovskite nanocrystals with charged ligands, such as salts, zwitterions, or acid–base pairs, has been extensively documented over the past few years. On the other hand, little is known about the reactivity of perovskite nanocrystals toward neutral ligands. To fill this gap, in this work we study the interaction of CsPbBr3 nanocrystals passivated with didodecyldimethylammonium bromide (DDABr) toward a series of exogenous acid/base ligands using a combined computational and experimental approach. Our analysis indicates that DDABr-capped nanocrystals are inert toward most ligands, except for carboxylic, phosphonic, and sulfonic acids. In agreement with the calculations, our experimental results indicate that the higher the acidity of the ligands employed in the treatment, the more etching is observed. In detail, dodecylbenzenesulfonic acid (pKa = −1.8) is found to etch the nanocrystals, causing their complete degradation. On the other hand, oleic and oleylphosphonic acids (pKa 9.9 and 2, respectively) interact with surface-bound DDA molecules, causing their displacement as DDABr in various amounts, which can be as high as 40% (achieved with oleylphosphonic acid). Despite the stripping of DDA ligands, the optical properties of the nanocrystals, as well as structure and morphology, remain substantially unaffected, empirically demonstrating the defect tolerance characterizing such materials. Our study provides not only a clear overview on the interaction between perovskite nanocrystals and neutral ligands but also presents an effective ligand stripping strategy.

Adsorption configuration of dodecylamine at gas–liquid interface and its relationship with foam stability: MD simulation and ToF-SIMS investigation

Dodecylamine (DDA) as a collector was widely applied in flotation, but its high foam stability has also been proven in many laboratories or beneficiation plants. In this work, the adsorption configuration of DDA at the gas–liquid interface and its relationship with foam stability at different pH and concentration levels was investigated to gain insights into the performance and stability mechanism of DDA. A direct, reliable, and new way to investigate the gas–liquid interface information was introduced. Froth stability experiments, surface tension measurements, time-of-flight secondary ion mass spectrometry (ToF-SIMS) measurements assisted by principal component analysis (PCA), and molecular dynamics (MD) simulation were carried out. Results revealed that the foam stability of DDA was extremely high under strong acidic condition. It increased gradually and then decreased as the DDA concentration increased, and reached the maximum at the critical micelle concentration. The positive adsorption of DDA was directly observed and confirmed by ToF-SIMS. The primary factor affecting the foam stability of DDA at different pH levels was not the adsorption capacity of DDA at the gas–liquid interface (surface tension) but the interaction intensity between the head groups of DDA and water molecules. The dominant factors affecting the foam stability of DDA at different concentrations were the adsorption capacity of DDA at the gas–liquid interface (surface tension), the interaction intensity between the head groups and water molecules, and the arrangement configuration of DDA molecules at gas–liquid interface.

Enabling synchronous activation of inner-core and mesoporous outer-shell of monodispersed Fe3O4@SiO2 by in-situ implanted MnO to synergistically deliver enhanced catalytic activity

Abstract Herein, we report a facile synthetic method enabling the synchronously activated decoration of the inner core and mesoporous outer shell of monodispersed Fe3O4@meso-silica using in situ implanted MnOx. This approach can maintain the catalytic activity of the internal core without loss of its inherent magnetic properties even when undergoing calcination. The developed catalyst exhibits a well-defined core-shell configuration with a MnOx coating on an Fe3O4 internal core and a MnOx-modified mesoporous outer shell, obtained via only a one-pot output cycle. The thin MnOx coating layer prevents excess oxidation of the unoxidized Fe3O4 core during the annealing process. Additionally, the mesopores in the coated silica were synchronously functionalized by the assistance of dodecylamine (DDA) as surfactant because of the coordination effect of Mn2+ and DDA molecules. The optimal nanocatalyst exhibits improved catalytic activity for styrene oxidation and recoverability due to its magnetic-responsive properties, in contrast to postsynthesized and shell-only functionalized catalysts.

Multidimensional insights into the corrosion inhibition of 3,3-dithiodipropionic acid on Q235 steel in H2SO4 medium: A combined experimental and in silico investigation

3,3-Dithiodipropionic acid (DDA) as a potential corrosion inhibitor for Q235 steel in 0.5 M H2SO4 solution was examined. A variety of research approaches including electrochemical impedance spectroscopy (EIS), potentiodynamic polarization (PDP), scanning electron microscopy (SEM), atomic force microscopy (AFM), and computational techniques were employed. The toxicity and solubility of DAA were reasonably assessed. Its inhibition efficiency can reach approximately 93% when the optimal concentration is 5 mM. The results of PDP curves manifest that DDA is a mixed type corrosion inhibitor. EIS data indicate that the charge transfer resistance increases with increasing concentration of DDA. Gibbs free energy obtained from the Langmuir isotherm model suggests that DDA molecules hinder the acid attack mainly by chemisorption. Surface topography analysis strongly confirmed the electrochemical findings. Moreover, the simulation results based on density functional theory (DFT) calculation and molecular dynamics (MD) simulations supported the successful interfacial adsorption of DDA on Fe(1 1 0) surface.

Scale sorting high-purity semiconducting single-walled carbon nanotubes in oil/water bi-continuous system using alkanolamide surfactants

So far, separation and scale production of high-purity semiconducting single-walled carbon nanotubes (s-SWNTs) remains one of the foremost hurdles in SWNT applications. N, N-bis (2-hydroxyethyl) dodecanamide (DDA), a kind of nonionic alkanolamide surfactant with a π-conjugated amide group, exhibits strong selectivity for s-SWNTs within a certain diameter range by constructing a specific oil/water bi-continuous system. It was found that the amide groups of DDA molecules showed specific recognition ability to s-SWNTs by electrostatic complementarity in nonpolar medium, while the diameter selectivity resulted from the different adsorption geometries of the alkyl chains of DDA molecules on s-SWNTs under hydrophobic interaction in the constructed oil/water bi-continuous system. The high yield (∼33.6%) of the sorted s-SWNTs benefited from the precision of the self-assembly behavior of surfactant molecules. The finding in this work not only is meaningful for paving a way to selectively separate s-SWNTs in large scale with low-cost, but also reveals one kind of critical interaction between amide groups and s-SWNTs, which may be an essential point influencing the exploitation of the potential applications of s-SWNTs in many fields.

Self-assembly of mixed dodecylamine–dodecanol molecules at the air/water interface based on large-scale molecular dynamics

Dodecylamine (DDA)–alcohol mixtures have motivated great interest recently due to their superior performance in industrial processes compared with pure DDA. Self-assembly of surfactants at the air/water interface plays an important role in their surface properties. However, the self-assembly of mixed DDA–alcohol at an atomic level is still unknown. In this study, large-scale atomistic dynamic simulations of DDA–dodecanol (DOD) mixtures with different ratios were performed to clarify their molecular arrangement and explain the synergistic effect. The structural properties, such as molecular aggregation, orientation, angle distributions, and H bond distributions, of DDA–DOD mixtures were characterized in detail. Simulation results show considerable differences in the behavior of mixed DDA–DOD molecules with different ratios. The self-assembly of pure DDA molecules is not significant due to the strong electrostatic repulsion between head groups. The surface activity of pure DOD molecules is not strong due to their poor water solubility based on their fewer amounts of H-bonds with water. For mixed DDA–DOD, the addition of DOD does not directly affect the arrangement of DDA molecules; rather, DOD molecules insert between DDA molecules and form stable clusters at the air/water interface due to the van der Waals interactions between surfactant chains. Two main interaction patterns exist between DDA and DOD, including van der Waals interactions between the surfactant chains and H bonds between their head groups. DOD and DDA play an important role in forming the cluster and solvent action, respectively. The ratio of these two surfactants can affect the two above properties. This study provides a good strategy to investigate the self-assembly cluster of mixed surfactants and supports the experimental theory at the atomic level.

In Situ Synthesis of MoP Nanoflakes Intercalated N-Doped Graphene Nanobelts from MoO3 -Amine Hybrid for High-Efficient Hydrogen Evolution Reaction.

Molybdenum phosphide (MoP) is a promising non-noble-metal electrocatalyst in the hydrogen evolution reaction (HER), but practical implementation is impeded by the sluggish HER kinetics and poor chemical stability. Herein, a novel high-efficiency HER electrocatalyst comprising MoP nanoflakes intercalated nitrogen-doped graphene nanobelts (MoP/NG), which are synthesized by one-step thermal phosphiding organic-inorganic hybrid dodecylamine (DDA) inserted MoO3 nanobelts, is reported. The intercalated DDA molecules are in situ carbonized into the NG layer and the sandwiched MoO3 layer is converted into MoP nanoflakes which are intercalated between the NG layers forming the alternatingly stacked MoP/NG hybrid nanobelts. The MoP nanoflakes provide abundant edge sites and the sandwiched MoP/NG hybrid enables rapid ion/electron transport thus yielding excellent electrochemical activity and stability for HER. The MoP/NG shows a low overpotential of 94 mV at 10 mA cm-2 , small Tafel slope of 50.1 mV dec-1 , and excellent electrochemical stability with 99.5% retention for over 22 h.

Dynamic surface tension measurement of dodecylamine solutions—a pendant bubble tensiometer with modified cell system

A pendant bubble tensiometer was modified for the dynamic surface tension (ST) measurement of a dodecylamine (DDA) surfactant solution. The dynamic STs of DDA solutions showed a peculiar relaxation: the ST relaxed from the ST of the solvent, reached a minimum, and then increased to ∼72 mN/m. The pH values of aqueous DDA solutions indicated that the DDA was partially ionized, with an ionization degree between 2 and 7%. The partially protonated DDA molecules probably prefer to adsorbed on the quartz surface of the sample cell and the metal needle surface, thereby depleting the bulk concentration and causing the desorption of the previously adsorbed DDA molecules at the air–solution interface. A coated quartz cell and a continuous pumping system were implemented in the pendant bubble tensiometer. The dynamic STs of DDA in the 0, 50, and 500 mM NaCl solutions smoothly relaxed from the ST of the solvent, reached the equilibrium ST (γe) and remained at γe for a long time without any increase. This pendant bubble tensiometer with modified cell system is capable of measuring the dynamic ST of the partially ionized dodecylamine surfactant solution.

Effect of pH on the adsorption of dodecylamine on montmorillonite: Insights from experiments and molecular dynamics simulations

The hydrophobic aggregation in cationic surfactant suspension is an effective method to enhance the dewatering of clay-rich tailing. The solution pH can affect the adsorption behavior of cationic surfactant on clay mineral. The effect of pH on the adsorption of dodecylamine (DDA) on montmorillonite was investigated by the sedimentation test and the characterization of flocs images, contact angle, adsorption quantity, and fourier transform infrared (FTIR) spectroscopy, as well as molecular dynamics (MD) simulation. It was found that DDA ions were adsorbed on montmorillonite basal surfaces mainly by physical adsorption, including the electrostatic attraction and hydrogen bonding. A certain number of neutral DDA molecules can favor the adsorption of DDA. At pH around 8, the effect of hydrophobic modification was the best because DDA molecules and ions form compact and well-organized monolayer. The MD simulation results were in good agreement with that of contact angle, adsorption quantity and FTIR.

Adsorption behavior of mixed cationic/anionic surfactants and their depression mechanism on the flotation of quartz

Mixed cationic/anionic surfactants are generating increasing attention as effective collectors during the flotation of muscovite, feldspar and spodumene ores. Many papers have been published focusing on the flotation mechanisms of these valuable minerals. However, the depression mechanisms on gangue minerals such as quartz have rarely been reported. In this study, mixed dodecylamine (DDA)/sodium oleate (NaOL) surfactants were used in the flotation separation of muscovite and quartz, and their depression mechanisms on quartz were investigated. Compared to DDA alone, the use of mixed surfactants resulted in a significantly higher adsorption amount of surfactants on the quartz but a lower flotation recovery and contact angle with the quartz. This is attributed to the different molecular self-assembly mechanisms between solely DDA and mixed surfactants at the quartz/water interface, as revealed by molecular dynamics simulations. A hydrophobic monolayer coating forms for solely DDA, with the head groups adsorbing on the quartz via electrostatic interactions. In the case of mixed surfactants, DDA preferentially interacts with NaOL via electrostatic interaction through the oppositely charged head groups and hydrophobic interactions between their carbon chains. As a result, most DDA and NaOL molecules form hydrophilic spherical-like micelles near quartz, whereas only a few DDA molecules adsorb directly on the quartz via hydrogen bonding. These act as a bridge linking the rest of the surfactants, leading to a relatively lower flotation recovery and contact angle for the quartz. This study is beneficial for complementing the flotation theories and mechanisms of mixed cationic/anionic surfactants on minerals.

PH effects on adsorption behavior and self-aggregation of dodecylamine at muscovite/aqueous interfaces

In this work, molecular dynamics simulation was used to examine the effect of solution pH on the adsorption behavior and self-aggregation of dodecylamine hydrochloride (DDA) on the muscovite (0 0 1) surface. The properties of surfactants are assessed in terms of density profiles in the direction perpendicular to the muscovite surface. Results show that although DDA can adsorb at muscovite at all pH we discussed, the self-aggregation of DDA varies significantly at different pH values. At pH 10, a compact hydrophobic monolayer forms on the muscovite surface. At pH 3, hemi-micelle aggregated structure forms with several DDA cations far away from muscovite surface. At pH 12, it has been confirmed that adsorption of DDA neutral molecules occurs with only a few DDA molecules adsorbing on muscovite directly and acting as a bridge linking the rest DDA molecules, which exists nearby muscovite surface irregularly. Density profiles revealed that at pH 10, DDA cations play a dominant role in the interaction between DDA surfactants and muscovite. While DDA molecules have difficulty in forming a hydrogen bond with the oxygen atom on the muscovite surfaces, and they co-adsorb onto muscovite through the electrostatic interactions with muscovite and hydrophobic force with DDA cations. Therefore, the hydrophobization of muscovite in the presence of DDA are higher at pH 10 than that at pH 3 and pH 12. Our results indicate that molecular dynamics simulation can be a power tool in charactering adsorption behavior of surfactants onto mineral surfaces at different pH values.

Structural characterization of 2,3,5,6-tetramethyl-p-phenylenediamine radical cation and its dimer in molecular crystals

Reaction between 2,3,5,6-tetramethyl-p-phenylenediamine (DDA) and bromanil (BA) gave two different crystalline products, needle-like and block-shaped crystals. The former was an alternate-stack 1:1 charge-transfer complex between DDA and BA with an electron-transfer ratio of about 0.7. The latter was a bromide salt of DDA, which was crystallized simultaneously with the decomposition of BA anions. The DDA molecules in the salt were dimerized even at room temperature. The similar products were obtained by a reaction between DDA and chloranil. The molecular and electronic structures are discussed with the calculation results of the density functional theory. This report has two additional meanings on the synthesis of charge-transfer complexes with using haloanils, which are commonly used as electron acceptors: (1) special attention must be paid for contaminating halide ions in characterizing reaction products and in discussing their properties, and (2) a new moderate synthetic root of halide complexes becomes available when using haloanils.

Diaza-adamantane derivatives as corrosion inhibitor for copper in nitric acid medium

The effect of newly synthesized 6-hydroxy-5,7-diphenyl-1,3-diazaadamantane (HDDA) and 5,7-diphenyl-1,3-diazaadamantan-6-one (DDA) against the corrosion of copper in 1 M HNO3 solution was investigated using potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and weight loss measurements. These measurements show that the inhibition efficiency (IE %) obtained by these compounds increased by increasing their concentrations, and maximum IE % to 90.84 % for HDDA and 89.87 % for DDA were found at 300 ppm. Data obtained from EIS studies were analyzed by an equivalent circuit model. EIS plots indicated that the inhibitor performance depends on the adsorption of the molecules on the metal surface. Polarization measurements showed that both HDDA and DDA are mixed-type but predominantly cathodic in 1 M HNO3 solution. The adsorption of inhibitors on the copper surface from the nitric acid follows the Langmuir adsorption isotherm with a negative value of free energy, and these values indicated that adsorption of both HDDA and DDA molecules adsorbs physically on the copper surface. The surface morphology was examined by scanning electron microscope and atomic force microscope. Further, theoretical calculations were carried out and relationships between computed parameters and experimental IE % were discussed. All the results confirmed that e HDDA showed better efficiency in 1 M HNO3 compared to DDA.

Characteristics of hydrogen bond revealed from water clusters

The hydrogen bond network is responsible for the exceptional physical and chemical properties of water, however, the description of hydrogen bond remains a challenge for the studies of condensed water. The investigation of structural and binding properties of water clusters provides a key for understanding the H-bonds in bulk water. In this paper, a new set of geometric parameters are defined to describe the extent of the overlap between the bonding orbital of the donor OH and the nonbonding orbital of the lone-pair of the acceptor molecule. This orbital overlap plays a dominant role for the strength of H-bonds. The dependences of the binding energy of the water dimer on these parameters are studied. The results show that these parameters properly describe the H-bond strength. The ring, book, cage and prism isomers of water hexamer form 6, 7, 8 and 9 H-bonds, and the strength of the bonding in these isomers changes markedly. The internally-solvated and the all-surface structures of (H2O)n for n = 17, 19 and 21 are nearly isoenergetic. The internally-solvated isomers form fewer but stronger H-bonds. The hydrogen bonding in the above clusters are investigated in detail. The geometric parameters can well describe the characters of the H-bonds, and they correlate well with the H-bond strength. For the structures forming stronger H-bonds, the H-bond lengths are shorter, the angle parameters are closer to the optimum values, and their rms deviations are smaller. The H-bonds emanating from DDAA and DDA molecules as H-donor are relatively weak. The vibrational spectra of (H2O)n (n = 17, 19 and 21) are studied as well. The stretching vibration of the intramolecular OH bond is sensitive to its bonding environment. The H-bond strength judged from the geometric parameters is in good agreement with the bonding strength judged from the stretching frequencies.

Complexation of starch with dodecylamine

The chemical nature of the interaction of starch and dodecylamine (DDA), which generally act as depressant and collector, respectively, in the reverse flotation of bauxite, was investigated using starch-iodine tests. The results obtained from the blue-value measurements for starch+DDA+iodine system indicate the formation of the inclusion complex for amylose-DDA system at low DDA concentration (<2 mmol/L). However, it is less likely for amylopectin-DDA system with short helix. UV-Vis spectra of starch-iodine complexes show that each helix of amylose can accommodate two DDA molecules locating separately at its two ends, and in the helical cavity there is room available for the upcoming iodine. When concentrated DDA is tested, amylose-DDA system exhibits no characteristic starch-iodine color, owing to the presence of a compact coating of DDA molecules on starch via hydroxyl/amine hydrogen bonding. 1H NMR spectroscopy and surface tension determination help to clarify the interaction mechanism of amylose with DDA.

Effect of degree of substitution of carboxymethyl starch on diaspore depression in reverse flotation

Carboxymethyl starchs (CMS) with low and high degrees of substitution (CMS L and CMS H in short, respectively) were employed as depressants of diaspore in cationic reverse flotation using dodecylamine (DDA) as collector. The effect of degree of substitution of CMS on its depression performance was examined and the interaction mode and behavior were investigated in a comparative manner. Micro-flotation test showed that CMS L exhibited better performance in depressing diaspore than CMS H in a broad pH range. The adsorption of CMS on diaspore was studied by adsorption test, zeta potential measurement, and atomic force microscopy. It was found that CMS H corresponds to lower adsorption amount, thinner adsorption layer, and more negative charge than CMS L, resulting from the more chelating sites brought by the high degree of substitution. The surface tension measurement and DDA adsorption test further revealed that CMS L/DDA system gives a better depressing performance benefiting from the trapping effect by enveloping some DDA molecules inside the loop chains, while CMS H/DDA system is likely considered a quasi-surfactant.

Effects of dodecylamine and dodecanethiol on the conductive properties of nano-Ag films

Nano-Ag particles, with dodecylamine (DDA) and dodecanethiol (DDT) as the protective agent, were prepared and studied in order to investigate the effect of protective agent in the post heat-treatment of nano-Ag films. Results of electrical resistivity, micro-structural evolution and thermal analysis showed that the Ag–DDA films require a lower treatment temperature to convert into conductive materials compared to that of the Ag–DDT films. And the Ag–DDA films also have lower final electrical resistivity as well as more uniform and dense microstructure in comparison with the Ag–DDT films. Further study indicated that Ag–DDA films are thermodynamically unstable and the sinter of Ag–DDA particles could occur spontaneously even at room temperature. FT-IR, 1H NMR and X-ray diffraction determinations revealed that both DDA and DDT molecules coordinate to the surface of nano-Ag particles through their head-groups. The bonding energy of Ag–S is higher than that of Ag–N and the alkyl chains ordering of chemisorbed DDT is also higher than that of chemisorbed DDA. It is implied that the post heat-treatment temperature and final resistivity of nano-Ag films are associated with the bonding energy and configuration of different capping molecules. Finally the conductive ink was prepared with well dispersed Ag–DDA nanoparticles and the ink-jet printed patterns on PI films show a sheet resistance of 166mΩ/□ after heat-treating at 140°C for 60min.