Effects of silver nanoparticles on thermal properties of DBSA-doped polyaniline/PVC blends

Dodecylbenzenesulfonic acid (DBSA)-doped polyaniline (PAND) has been synthesized by redoping (PANDR) and aqueous polymerization (PANDA) methods. Silver nanoparticles were incorporated into the PANDR/tetrahydrofuran solution (PANDS) and then mixed with poly (vinyl chloride) (PVC) solution to prepare PANDS/PVC nanocomposites. In the present study, effects of silver nanoparticles on thermal properties of PAND/PVC blends have been investigated by employing thermal gravimetric analysis and heat flow microcalorimetry techniques. From these results it has been observed that the thermal stability of blends have increased by increasing the concentration of PAND in blends and nanocomposites. Addition of silver nanoparticles has suppressed the dehydrochlorination process and evolution/degradation of DBSA in PANDS/PVC nanocomposites. Presence of silver nanoparticles in PAND/PVC nanocomposites has reduced the mobility of PANI chains which in turn inhibited the transfer of free radicals formed during degradation of PAND and PVC through inter-chain reactions; hence, degradation process has been slowed down and thermal stability has been improved. Embedment of silver nanoparticles has reduced thermal weight loss corresponding to polymer degradation step and attains lower heat flow level in inert atmosphere for nanocomposites in contrast to those with no nanoparticles, thereby further improving thermal stability of nanocomposites. The heats of oxidation measured for blends and nanocomposites were independent of PAND/PVC blends composition.     

Highly Efficient Room Temperature Synthesis of Silver‐Doped Zinc Oxide (ZnO:Ag) Nanoparticles: Structural,Optical, and Photocatalytic Properties

Synthesis of silver‐doped zinc oxide (ZnO:Ag) nanoparticles through precipitation method has been reported. The synthesis was conducted at room temperature and no subsequent thermal treatment was applied. ZnO nanoparticles were characterized by X‐ray diffraction (XRD), transmission electron microscopy (TEM), X‐ray photoelectron spectroscopy (XPS), fourier transmission infrared spectroscopy (FTIR), and ultraviolet‐visible (UV–Vis) spectroscopy. Detailed crystallographic investigation was accomplished through Rietveld refinement. The effect of silver content on structural and optical properties of resultant ZnO nanoparticles has been reported. It was found that silver doping results in positional shifts for the XRD peaks and the absorption band edge of ZnO. These were attributed to the substitutional incorporation of Ag⁺ ions into Zn²⁺ sites within the ZnO crystal. In addition, higher silver incorporation resulted in smaller size for ZnO nanoparticles. The photocatalytic activity of the ZnO:Ag nanoparticles was also determined by methylene orange (MO) degradation studies and compared to that of undoped ZnO. Improved photocatalytic activity was obtained for ZnO:Ag nanoparticles. It has been shown that an optimum amount of silver dopant is required to obtain maximum photocatalytic activity.     

Preparation of silver hydrosols using polyethylene glycol modified with vinyl pyrrolidone

Hydrosols containing silver nanoparticles were prepared from copolymers of ethylene glycol (EG) and vinyl pyrrolidone (VPy). The copolymers were synthesized using a macro-azo-radical initiator appended with EG units. The hydrosols were prepared by simply stirring the copolymers with AgNO₃ in water at room temperature. The nanoparticles conferred thermal stability to the hydrosols, up to 80 °C. Spectroscopic, thermal, and gas chromatography analyses revealed that the silver nanoparticles were protected by EG and carbonyl groups with strong interaction between silver and the oxygen species of EG and VPy.     

Electron Beam Synthesis and Characterization of Poly Vinyl Alcohol/Poly Acrylic Acid Embedded Ni and Ag Nanoparticles

Electron beam irradiation was applied to prepare poly (vinyl alcohol) and poly (acrylic acid) P (PVA/AAc) containing nickel and silver nanoparticles. The prepared P (PVA/AAc)–Ni and P (PVA/AAc)–Ag nanoparticles were characterized by Fourier-transform infrared, UV–Visible spectroscopy, X-ray diffraction (XRD) and transmission electron microscope (TEM). The electrical conductivity and thermal gravimetrical analysis (TGA) have been investigated. Bacterial sensitivity toward nickel and silver nanoparticles was studied. The XRD and TEM confirmed that by increasing the Ni or Ag contents from 10 to 150?mmol in the copolymers, the metal particle size increases from 27.6 to 45.6?nm for Ni and from 14.8 to 37.4?nm for Ag. Meanwhile, the mean size particle increases from 33.02 to 45.05?nm for Ni and from 15.5 to 44.03?nm for Ag. The electrical conductivity of the polymer containing Ag is higher than that of Ni and it increased by increasing the metal content. The TGA studies confirmed that, the thermal stability increase by the introduction of metal into polymeric complex. Bacterial sensitivity to metal nanoparticles was found to vary depending on the microbial species. Disc diffusion studies with P. aeruginosa, E. coli and K. pneumoniae revealed greater effectiveness of the silver nanoparticles compared to the nickel nanoparticles, S. aureus depicted the highest sensitivity to nanoparticles compared to the other strains and was more adversely affected by the nickel nanoparticles.     

Silver Nanoparticles and Graphitic Carbon Through Thermal Decomposition of a Silver/Acetylenedicarboxylic Salt

Spherically shaped silver nanoparticles embedded in a carbon matrix were synthesized by thermal decomposition of a Ag(I)/acetylenedicarboxylic acid salt. The silver nanoparticles, which are formed either by pyrolysis at 300 °C in an autoclave or thermolysis in xylene suspension at reflux temperature, are acting catalytically for the formation of graphite layers. Both reactions proceed through in situ reduction of the silver cations and polymerization of the central acetylene triple bonds and the exact temperature of the reaction can be monitored through DTA analysis. Interestingly, the thermal decomposition of this silver salt in xylene partly leads to a minor fraction of quasicrystalline silver, as established by HR-TEM analysis. The graphitic layers covering the silver nanoparticles are clearly seen in HR-TEM images and, furthermore, established by the presence of sp² carbon at the Raman spectrum of both samples.     

Preparation and stability of silver/kerosene nanofluids

ABSTRACT: A series of silver nanoparticles surface-coated with di-n-dodecyldithiophosphate, di-n-cetyldithiophosphate, or di-n-octadecyldithiophosphate have been prepared and have good dispersity in alkanes or kerosene. Stable silver nanofluids can be formed in alkanes or kerosene with the surface-coated silver nanoparticles. Thermal stability of the silver nanofluids has been measured at different temperatures. The effects of the silver nanoparticles on the thermal oxidation of kerosene have been investigated at different temperatures. The coatings can be released from the surface of the silver nanoparticles above 150°C, giving oxygen access to the silver core and inhibiting the kerosene oxidized by oxygen.     

Synthesis and characterization of polyaniline derivative and silver nanoparticle composites

BACKGROUND: There has been a recent surge of interest in the synthesis and applications of electroactive polymers with incorporated metal nanoparticles. These hybrid systems are expected to display synergistic properties between the conjugated polymers and the metal nanoparticles, making them potential candidates for applications in sensors and electronic devices. RESULTS: Composites of polyaniline derivatives—polyaniline, poly(2,5‐dimethoxyaniline) and poly(aniline‐2,5‐dimethoxyaniline)—and silver nanoparticles were prepared through simultaneous polymerization of aniline derivative and reduction of AgNO₃ in the presence of poly(styrene sulfonic acid) (PSS). We used AgNO₃ as one of the initial components (1) to form the silver nanoparticles and (2) as an oxidizing agent for initiation of the polymerization reaction. UV‐visible spectra of the synthesized nanocomposites reveal the synchronized formation of silver nanoparticles and polymer matrix. The morphology of the silver nanoparticles and degree of their dispersion in the nanocomposites were characterized by transmission electron microscopy. Thermogravimetric analysis and differential scanning calorimetry results indicate an enhancement of the thermal stability of the nanocomposites compared to the pure polymers. The electrical conductivity of the nanocomposites is in the range 10^?4 to 10^?2 S cm^?1. CONCLUSION: A single‐step process for the synthesis of silver nanoparticle–polyaniline derivative nanocomposites doped with PSS has been demonstrated. The approach in which silver nanoparticles are formed simultaneously during the polymerization process results in a good dispersion of the nanoparticles in the conductive polymer matrix. Copyright © 2008 Society of Chemical Industry     

Radiation synthesis and characterization of poly(vinyl alcohol)/poly(N-vinyl-2-pyrrolidone) based hydrogels containing silver nanoparticles

A series of PVA/PVP based hydrogels at different compositions were prepared by gamma irradiation. The gel fraction degree of swelling were investigated. Highly stable and uniformly distributed silver nanoparticles have been obtained onto hydrogel networks. The morphology and structure of (PVA/PVP) hydrogel and dispersion of the silver nanoparticles in the polymeric matrix were examined by scanning electron microscopy (SEM) and infrared spectroscopy (FT-IR), respectively. The formation of silver nanoparticles has been confirmed by ultraviolet visible (UV–vis) spectroscopy. A strong characteristic absorption peak was found to be around 420 nm for the silver nanoparticles in the hydrogel nanocomposite. The X-ray diffraction pattern confirmed the formation of silver nanoparticles with average particle size of 12 nm. The diameter distribution of silver nanoparticles was determined by dynamic light scattering DLS. Transmission electron microscope (TEM) showed almost spherical and uniform distribution of silver nanoparticles through the hydrogel network and the mean size of silver nanoparticles ranging is 23 nm. The good swelling properties and antibacterial of PVA/PVP-Ag hydrogel suggest that it can be a good candidate as wound dressing.     

Synthesis and characterization of hydrogel‐silver nanoparticle‐curcumin composites for wound dressing and antibacterial application

Hydrogel silver nanocomposites are found to be excellent materials for antibacterial applications. To enhance their applicability novel hydrogel‐silver nanoparticle‐curcumin composites have been developed. For developing, these composites, the hydrogel matrices are synthesized first by polymerizing acrylamide in the presence of poly(vinyl sulfonic acid sodium salt) and a trifunctional crosslinker (2,4,6‐triallyloxy 1,3,5‐triazine, TA) using redox initiating system (ammonium persulphate/TMEDA). Silver nanoparticles are generated throughout the hydrogel networks using in situ method by incorporating the silver ions and subsequent reduction with sodium borohydride. Curcumin loading into hydrogel‐silver nanoparticles composite is achieved by diffusion mechanism. A series of hydrogel‐silver nanoparticle‐curcumin composites are developed and are characterized by using Fourier transform infrared (FTIR) and UV–visible (UV–vis) spectroscopy, X‐ray diffraction, thermal analyses, as well as scanning and transmission electron microscopic (SEM/TEM) methods. An interesting arrangement of silver nanoparticles i.e., a shining sun shape (ball) (～ 5 nm) with apparent smaller grown nanoparticles (～ 1 nm) is observed by TEM. The curcumin loading and release characteristics are performed for various hydrogel composite systems. A comparative antimicrobial study is performed for hydrogel‐silver nanocomposites and hydrogel‐silver nanoparticle‐curcumin composites. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Thermal decomposition as route for silver nanoparticles

Single crystalline silver nanoparticles have been synthesized by thermal decomposition of silver oxalate in water and in ethylene glycol. Polyvinyl alcohol (PVA) was employed as a capping agent. The particles were spherical in shape with size below 10 nm. The chemical reduction of silver oxalate by PVA was also observed. Increase of the polymer concentration led to a decrease in the size of Ag particles. Ag nanoparticle was not formed in the absence of PVA. Antibacterial activity of the Ag colloid was studied by disc diffusion method.     

Nanostructured Silver Substrates With Stable and Universal SERS Properties: Application to Organic Molecules and Semiconductor Nanoparticles

Nanostructured silver films have been prepared by thermal deposition on silicon, and their properties as SERS substrates investigated. The optimal conditions of the post-growth annealing of the substrates were established. Atomic force microscopy study revealed that the silver films with relatively dense and homogeneous arrays of 60–80-nm high pyramidal nanoislands are the most efficient for SERS of both organic dye and inorganic nanoparticles analytes. The noticeable enhancement of the Raman signal from colloidal nanoparticles with the help of silver island films is reported for the first time.     

An antibacterial submicron fiber mat with in situ synthesized silver nanoparticles

This work presents an alternative approach for fabricating electrospun submicron highly hydrophilic fiber mats loaded with silver nanoparticles. These fiber mats show a high efficient antibacterial behavior, very attractive for applications like wound healing and skin regeneration processes. The fabrication method is divided in two steps. First, poly(acrylic acid) (PAA) and β‐cyclodextrin (β‐CD) submicron fibers were electrospun and further stabilized using a thermal treatment, yielding stable hydrogel‐like fibers with diameters ranging from 100 nm up to several microns. In the second step, silver ions were loaded into the fibers and then reduced to silver nanoparticles in‐situ. The electrospinning parameters were adjusted to achieve the desired properties of the fiber mat (density, size) and afterwards, the characteristics of the silver nanoparticles (amount, size, aggregation) were tuned by controlling the silver ion loading mechanism. Highly biocide surfaces were achieved showing more than 99.99% of killing efficiency. The two‐step process improves the reproducibility and tunability of the fiber mats. To our knowledge, this is the first time that stable hydrogel fibers with a highly biocide behavior have been fabricated using electrospinning. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

巯基丙酸保护的纳米银制备及热分解行为研究

以双官能团配体巯基丙酸(MPA)为保护剂, 通过配体置换法和液相化学还原法制备得到纳米银.考察了双官能团配体对纳米银的制备及热分解的影响.配体置换法制备的纳米银粒径为50 nm左右,化学还原法制备的纳米银粒径为10 nm左右.元素分析结果和X射线光电子能谱表明MPA通过S原子与Ag原子形成共价键,同时通过烷基链之间的氢键作用及范德华力形成多层保护剂保护的纳米银.将纳米银在200 ℃下烧结并对烧结产物进行表征,结果表明加热使得C-S键断裂,Ag/MPA热分解形成硫化银.     

Fabrication,characterization, and thermal property evaluation of silver nanofluids

Silver nanoparticles were successfully prepared in two different solvents using a microwave heating technique, with various irradiation times. The silver nanoparticles were dispersed in polar liquids (distilled water and ethylene glycol) without any other reducing agent, in the presence of the stabilizer polyvinylpyrrolidone (PVP). The optical properties, thermal properties, and morphology of the synthesized silver particles were characterized using ultraviolet-visible spectroscopy, photopyroelectric technique, and transmission electron microscopy. It was found that for the both solvents, the effect of microwave irradiation was mainly on the particles distribution, rather than the size, which enabled to make stable and homogeneous silver nanofluids. The individual spherical nanostructure of self-assembled nanoparticles has been formed during microwave irradiation. Ethylene glycol solution, due to its special properties, such as high dielectric loss, high molecular weight, and high boiling point, can serve as a good solvent for microwave heating and is found to be a more suitable medium than the distilled water. A photopyroelectric technique was carried out to measure thermal diffusivity of the samples. The precision and accuracy of this technique was established by comparing the measured thermal diffusivity of the distilled water and ethylene glycol with values reported in the literature. The thermal diffusivity ratio of the silver nanofluids increased up to 1.15 and 1.25 for distilled water and ethylene glycol, respectively.     

十八烷基丙撑二胺/硝酸银水溶液体系中纳米银粒子的制备及其在材料保护中的应用

本文采用了十八烷基丙撑二胺/硝酸银水溶液体系,成功地制备了较稳定的纳米银粒子,并对这两种制备方法进行了简单的比较;并对其材料保护中的应用进行了进一步的探讨。     

Hydrogel networks as nanoreactors: A novel approach to silver nanoparticles for antibacterial applications

Hydrogel networks based on N-isopropylacrylamide (NIPAM) and sodium acrylate (SA) were prepared by redox-polymerization in the presence of N,N′-methylenebisacrylamide (MBA). Highly stable and uniformly distributed silver nanoparticles have been prepared using these hydrogel networks as a carrier via in situ reduction of silver nitrate in the presence of sodium borohydride as a reducing agent. It has been demonstrated that the hydrogel hybrid with different sizes of silver nanoparticles can be effectively employed as antibacterial material.     

Silver/polystyrene nanocomposites: Optical and thermal properties

Nanocomposites consisted of different quantities of silver (Ag) nanoparticles incorporated in a polystyrene (PS) matrix have been prepared by solution mixing method. Transmission electron microscopy was applied to determine the size distribution of the Ag nanoparticles, while the morphology of fractured surfaces of pure PS and Ag/PS nanocomposites was examined by scanning electron microscopy. Absorption spectra of nanocomposites were compared with theoretically calculated spectra based on the Maxwell‐Garnett effective medium theory. The influence of Ag content on thermal properties of Ag/PS nanocomposites was investigated by thermogravimetric analysis and differential scanning calorimetry. Thermal and thermo‐oxidative stability of the host polymer were improved by introduction of silver nanoparticles. The glass transition temperature of the prepared Ag/PS nanocomposites was lower in comparison with the neat PS and decreased with the increase of the Ag content due to the very weak interfacial interaction between Ag nanoparticles and polymer matrix. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers     

Preparation and characterization of cellulose/Ag nanocomposites

A simple, green, and efficient microwave‐assisted heating method was developed to synthesize the cellulose/Ag nanocomposites by reducing silver nitrate in aqueous solution. The structure of nanocomposites was analyzed with X‐ray diffraction and Fourier transform infrared, the results showed that nanosilver particles were synthesized successfully on the surface of cellulose and did not change the structure of cellulose obviously. The shape and average size of silver nanoparticles and its distribution on cellulose fiber surface were observed by scanning electron microscopy, and the results demonstrated that the silver nanoparticles had a good distribution on the surface of cellulose fiber and high dosage of polyvinyl pyrrolidone decreased the size of nanosilver particles. Atomic absorption spectroscopy was used to measure the silver content in the composites, it was found that the silver content was higher in composites obtained by microwave heating compared with oil bath heating. The effect of silver nanoparticles on the thermal stability of cellulose fiber was studied by thermogravimetric analysis and differential scanning calorimetry, and it revealed that the silver nanoparticles had no obvious influence on the thermal stability of cellulose. The excellent antimicrobial activity against both Escherichia coli (gram‐negative bacteria) and Staphylococcus aureus (gram‐positive bacteria) showed a potential application in medical and health care field. POLYM. COMPOS., 36:2220–2229, 2015. © 2014 Society of Plastics Engineers     

Preparation and properties of nanocomposite hydrogels containing silver nanoparticles by ex situ polymerization

A series of composite hydrogels containing silver nanoparticle used for bioadhesives were prepared from acrylic acid, poly(ethylene glycol) methyl ether acrylate, and silver nanoparticles through ex situ polymerization. Silver nanoparticles with a narrow size distribution were prepared by the reduction of a silver nitrate solution with ascorbic acid. The influence of the content of the silver nanoparticles in the hydrogels on the equilibrium swelling ratio, mechanical properties, electrical conductivity, and inactivation of Escherichia coli (E. coli) was investigated in this study. The results showed that the swelling ratios of the composite gels were reduced by silver nanoparticles in the gels but were not reduced with an increase in the content of silver nanoparticles. In addition, the crosslinking density and shear modulus of these hydrogels did not increase with an increase in the content of silver nanoparticles. The adhesive force of these hydrogels (the APECAg series) was not obviously changed. Finally, the initial rate of E. coli inactivation for the APECAg series hydrogels showed excellent antibacterial properties. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 3653–3661, 2006     

Development of a yellow ceramic pigment based on silver nanoparticles

In this study a yellow pigment was obtained for third-fire ceramic decorations, based on silver nanoparticles synthesised by the method of chemical reduction in aqueous phase, using silver nitrate and polyvinylpyrrolidone as raw materials. Monitoring of the nanoparticle synthesis reaction by UV–vis spectroscopy allowed optimum operating conditions to be defined in preparing these particles for use as chromophores. Under these conditions, a stable suspension of Ag nanoparticles, which were well dispersed and had an average diameter of 20–30 nm, was obtained. Polyvinyl alcohol and tetraethyl orthosilicate were then added to the nanoparticle suspension to obtain the pigment precursor. The pigment precursor was directly applied on to fired glazed ceramic tile. Subsequent thermal treatment at moderate temperature (700 °C) yielded a layer less than one micron thick, which generated an intense yellow colour.