Synthesis and Characterization of Silver Sulfide Nanoparticles Containing Sol-Gel Derived HPC-Silica Film for Ion-Selective Electrode Application

Silver sulfide nanoparticles dispersed in sol-gel derived hydroxypropyl cellulose (HPC)-silica films have been successfully synthesized using H₂S gas diffusion method. This is the first attempt to produce silver sulfide nanoparticles using this technique. Ag₂S nanoparticles are generated through reaction of H₂S gas with AgNO₃ precursor dissolved in the HPC-silica matrix. Transmission electron microscope (TEM) and atomic force microscope (AFM) analysis reveal nanoparticles size distribution from 2.5 nm to 56 nm for H₂S gas exposed sample. The surface chemistry of Ag₂S nanoparticles and sol-gel derived HPC-silica matrix is confirmed by X-ray photoelectron spectroscopy (XPS). The negative shifts in the core-level XPS Ag (3d) binding energy of Ag₂S nanoparticles are attributed to Ag : S surface atomic ratio exhibited by these nanoparticles with varying processing conditions. Following processing and characterization, suitability of the present method to produce silver sulfide ion-selective electrode is demonstrated by depositing Ag₂S nanoparticles on a graphite rod. The high reponse function of the electrode is due to the presence of nanoparticles.     

Simultaneous synthesis of silver nanoparticles and poly(2,5‐dimethoxyaniline) in poly(styrene sulfonic acid)

Silver nanoparticles were formed in situ along with poly(2,5‐dimethoxyaniline) (PDMA) in an interconnected network matrix (reactor), comprising the electronic conductive polymer, PDMA, and a polyelectrolyte, poly(styrene sulfonic acid) (PSS), through the simultaneous reduction of Ag⁺ ions and polymerization of 2,5‐dimethoxyaniline. In situ ultraviolet‐visible spectroscopy showed that peaks corresponding to the plasmon resonance of silver nanoparticles at 411 nm and the polaronic transition of PDMA at 438 nm provided evidences for the simultaneous formation of silver nanoparticles and PDMA. Transmission electron microscopy and size distribution analysis revealed the presence of spherical silver nanoparticles with an average diameter of 12 nm in the composite. X‐ray photoelectron spectroscopy showed that the amine units in PDMA changed to imine units upon the formation of silver nanoparticles. A comprehensive mechanism for the formation of the PDMA‐PSS‐Ag nanocomposite is proposed. A 10‐fold increase in the conductivity was noticed for the PDMA–PSS–Ag nanocomposite (1 S/cm) in comparison with the PDMA–PSS composite (0.1 S/cm). © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3843–3852, 2006     

Chemical alteration of poly(tetrafluoroethylene) Teflon induced by exposure to vacuum ultraviolet radiation and comparison with exposure to hyperthermal atomic oxygen

The chemical alteration of poly(tetrafluoroethylene) Teflon by vacuum ultraviolet radiation (VUV) (115–400 nm) has been examined with X‐ray photoelectron spectroscopy (XPS). The initial F/C atom ratio of 1.98 decreases to 1.65 after a 2‐h exposure. The F/C atom ratio is further reduced to a steady‐state value of 1.60 after a 74‐h exposure. The high‐resolution XPS C1s data indicate that new chemical states of carbon form as F is removed and that the relative amounts of these states depend on the F content of the near‐surface region. The states are most likely due to C bonded only to one F atom, C bonded only to other C atoms, and C that has lost a pair of electrons through the emission of F^?. The exposure of the VUV‐damaged surface to research‐grade O₂ results in the chemisorption of a very small amount of O, and this indicates that large quantities of reactive sites are not formed during the chemical erosion by VUV. Further exposure to VUV removes this chemisorbed oxygen. A comparison of the XPS data indicates that the mechanisms of chemical alteration by VUV radiation and hyperthermal (～5 eV) atomic oxygen are different, as expected, because the excitation sources are quite different. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 552–561, 2005     

Methane plasma polymerization by low‐temperature cascade arc discharge for enhanced adhesion of primer to thermoplastic olefins

Improvement of primer adhesion to thermoplastic olefins (TPOs) by methane plasma polymerization with a low‐temperature cascade arc discharge was investigated. Methane plasma with a low‐temperature cascade arc plasma torch can be used for improving the primer adhesion to TPOs. Tape‐adhesion tests (ASTM 3359‐92a method) demonstrated this improvement, with a rating of 0 for untreated TPOs and 5 for methane plasma‐polymerized TPOs at certain plasma conditions even for aging at 60 °C and 80% relative humidity for 5 days. The adhesion to primer for the soft, flexible TPOs (ETA‐3041c and ETA‐3101) was easily enhanced. The adhesion to primer for the hard and brittle TPOs (ETA‐3183) needs to optimize the plasma conditions to pass the dry‐ and wet‐adhesion test with methane plasmas. To relate the surface characteristics of methane plasma‐polymerized TPOs to adhesion performance with primer, the wettability and polarity of TPOs were evaluated by the contact‐angle measurements of primer and deionized water to TPOs. TPO surface morphology was evaluated with scanning electron microscopy. The surface composition was characterized with electron spectroscopy for chemical analysis. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 2004–2021, 2003     

Surface modification on thermoplastic olefins by low‐temperature cascade arc discharge‐air plasmas for enhanced adhesion with primer

Improvement of primer adhesion to thermoplastic olefins (TPOs) by surface modification with a low‐temperature cascade arc discharge‐air plasmas was investigated. Air plasma with a low‐temperature cascade arc plasma torch can be used for improving the primer adhesion to TPOs. Tape‐adhesion tests (ASTM 3359‐92a method) demonstrated this improvement with a rating of “0” for untreated TPOs and “5” for air plasma‐modified TPOs at certain plasma conditions even for aging at 60 °C and 80% relative humidity for 5 days. The adhesion to primer for the soft and flexible kind of TPOs (ETA‐3041c and ETA‐3101) was easily enhanced. The adhesion to primer for the hard and brittle TPOs (ETA‐3183) needs to optimize the plasma conditions to pass the wet‐adhesion test using air plasmas. To relate the surface characteristics of air plasma‐modified TPOs to adhesion performance with primer, the wettability and polarity of TPOs were evaluated by the contact‐angle measurements of primer and deionized water to TPOs. TPO surface morphology was evaluated using scanning electron microscopy. The surface composition was characterized with electron spectroscopy for chemical analysis. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 623–637, 2002; DOI 10.1002/polb.10122     

State of Art in the SIMS (Secondary Ion Mass Spectrometry) Application to Archaeometry Studies

One of the main problems of cultural heritages in all the different forms (buildings, monuments, painting) is their deterioration caused by natural and artificial decay processes. To address the conservation issue specific studies are required to determine, for example, origin, date, materials composition, technology processes involved, etc. The use of microanalysis techniques, in particular secondary ion mass spectrometry (SIMS), in the cultural heritage area has been demonstrated extremely useful to approach and provide this kind of information and support the experts involved in studies within this area (art historians, archaeologists, curators etc.). In this work, an up to date overview of possible SIMS applications to archaeological topics is given, pointing out the peculiarity and the main limitations and drawbacks of this analytical approach. One example of SIMS application to archaeological glasses is reported. Moreover the wide technique flexibility and its strength in combination with other complementary techniques are remarked.     

Polymer Composites with Plasmonic Metal Nanoparticles

Summary: A two-phase method has been adapted for the preparation of polymer composites consisting of regioregular poly(3-octylthiophene-2,5-diyl) and Au or Ag nanoparticles. This work compares optical and morphological properties of nanocomposites formed by mixing metal organosols and polymer solution (type I composites) with nanocomposites formed by in-situ reduction in polymer solutions (type II composites). Both types contained very small metal nanoparticles (1–10 nm). Interestingly, more than ten-fold enhancement of Raman scattering of the polymer by the electromagnetic (EM) mechanism of SERS (surface-enhanced Raman scattering) resulted from the coupling of the polymer with plasmonic Au nanoparticles into a nanocomposite system.     

Distribution of melamine in polyester–melamine surface coatings cured under nonisothermal conditions

The influence of experimental cure parameters on the diffusion of reactive species in polyester–melamine thermoset coatings during curing has been investigated with X‐ray photoelectron spectroscopy and attenuated total reflectance Fourier transform infrared. The diffusion of melamine plays a vital role in the curing process and, therefore, in the ultimate properties of coatings. At a low (<20%) hexamethoxymethylmelamine (HMMM) crosslinker concentration, the matrix composition is uniform, but at high HMMM concentrations, excess HMMM rapidly segregates to the air–coating interface. The rate of migration is governed by the difference in the surface free energies of polyester and HMMM and the concentration gradient of HMMM between the bulk and the surface. An increased rate of energy absorption also increases the rate of migration of HMMM to the surface. A physical model has been proposed to explain this surface segregation phenomenon in terms of cocondensation and self‐condensation reactions. It suggests that an appropriate amount of melamine can be segregated on the surface and allowed to self‐condense to form a desired thickness of a melamine topcoat through the control of the binder composition and cure conditions. This technique can be implemented to apply a melamine topcoat during cure. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 83–91, 2004     

Long‐Term Stable Silver Subsurface Ion‐Exchanged Glasses for SERS Applications

We report on the formation of silver subsurface ion‐exchanged metal oxide (silver SIMO) glasses and their surface‐enhanced Raman scattering (SERS) activity. The samples were prepared by a combined thermal and chemical three‐step methodology and characterized by transmission electron microscopy (TEM), atomic force microscopy (AFM), environmental electron scanning microscopy (ESEM), and UV/Vis spectroscopy. This unique method provides SERS substrates with protection against contamination and strong, reliable and reproducible SERS enhancement. The Raman enhancement factors of the long‐term stable SIMO glasses were estimated to approximately 10⁷.     

Evolution of particle morphology during the synthesis of hybrid acrylic/CeO2 nanocomposites by miniemulsion polymerization

The evolution of the morphology of an acrylic/CeO₂ hybrid latex synthesized by a two step seeded semibatch emulsion polymerization process was investigated. The seed was produced by batch miniemulsion polymerization and in the second step a neat monomer preemulsion was fed to the seed to increase the solids content and encapsulate the inorganic material. The morphology of the hybrid miniemulsion droplets, the seed and the final latex was analyzed by TEM. The morphologies achieved could be explained by theoretical equilibrium morphology maps based on the interfacial tensions of the monomeric, polymeric, inorganic and aqueous phases. © 2014 Wiley Periodicals, Inc. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 792–799     

Characterization of the surface content,hydrolysis ratio,and condensation degree of polyalkoxysiloxane segregated to the surface of a polyurethane crosslinked film by X‐ray photoelectron spectroscopy

We report, using an electron spectrometer equipped with both monochromatized Al Kα and unmonochromatized Mg Kα sources, the quantitative characterization of the surface content, hydrolysis ratio, and condensation degree of polyalkoxysiloxane segregated to the surface of a polyurethane crosslinked film consisting of acryl polyol, polyisocyanate, and polyalkoxysiloxane. Unmonochromatized Mg Kα X‐ray irradiation extremely accelerated the decomposition of alkoxy groups of polyalkoxysiloxane. The surface content and hydrolysis ratio were determined from C 1s, Si 2p, and N 1s spectral intensities measured with monochromatized Al Kα X rays after decomposition by unmonochromatized Mg Kα X‐ray irradiation. The condensation degree was determined by the kinetic energy of the silicon KLL Auger electron after decomposition. We applied the established characterization method for a polyurethane film containing polyalkoxysiloxane. After 20 days, the surface content of polyalkoxysiloxane was greater than 60 wt %, the hydrolysis ratio ranged from 0.8 to 0.95, and the higher hydrolysis ratio resulted in a larger condensation degree. The hydrophilicity of the film surface became higher as the surface content and hydrolysis ratio increased, and the crack density became higher as the condensation degree increased. A method for characterizing the practical properties of coating film surfaces containing polyalkoxysiloxane was established. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2917–2926, 2002     

Crosslinking induced by in‐situ coordination in acrylonitrile butadiene rubber/poly(vinyl chloride) alloy,filled with anhydrous copper sulfate particles

Acrylonitrile butadiene rubber (NBR)/poly(vinyl chloride) (PVC) alloy, filled with anhydrous copper sulfate (CuSO₄) particles, was investigated for the first time. The material could be crosslinked in the existence of CuSO₄ by heat pressing, without any other crosslink agents. The crosslinking in the material was induced by in situ coordination between nitrile groups of NBR and solid CuSO₄ particles, which is thoroughly different from the traditional vulcanization of rubber materials. The coordination crosslinking is formed during heat pressing, other than in solutions, which is valuable for practical applications. The resulting material showed excellent tensile properties, and the maximum strength was close to 90 MPa. The CuSO₄ particles act not only as crosslink agents, but also as reinforcing fillers in the polymer matrix. In this work, dynamic mechanical analysis, differential scanning calorimetry, Fourier transform infrared spectrum, X‐ray photoelectron spectroscopy, scanning electron microscope, energy‐dispersive X‐ray spectrum, equilibrium swelling method, and tensile test were performed for the characterization of the material. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 378–386, 2006     

Role of anions in the polymerization of 2,5‐dimethoxyaniline in the presence of poly(styrene sulfonic acid)

Poly(2,5‐dimethoxyaniline) (PDMA)–Ag composites were successfully obtained through the oxidative polymerization of 2,5‐dimethoxyaniline in poly(styrene sulfonic acid) with CH₃SO₃Ag and AgNO₃ as oxidants. In situ ultraviolet–visible spectroscopy results showed that the growth rate of PDMA was strongly affected by CH₃SO and NO. The coupling reaction of PDMA and NO was proposed to explain the lower growth rate of PDMA with AgNO₃ as the oxidant in comparison with CH₃SO₃Ag. X‐ray photoelectron spectroscopy and Fourier transform infrared spectroscopy were used to validate the proposed coupling reaction through the monitoring of the side products and oxidized state of PDMA. The results showed that there were more side products and lower oxidized states for the composite structure in the presence of NO than in the presence of CH₃SO, and this agreed with the proposal. Transmission electron microscopy showed that the Ag nanoparticles had almost the same size, regardless of the anions. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 6624–6632, 2006     

Efficient photoinduced In situ preparation of clay/poly(glycidyl methacrylate) nanocomposites using hydrogen‐donor silane

Clay/poly(glycidyl methacrylate) nanocomposites (clay/PGMA) were prepared by in situ radical photopolymerization using N,N‐dimethylaminopropyltrimethoxysilane(DMA)‐modified bentonite clay acting as hydrogen donor for benzophenone in solution. This initiating system permits to photopolymerize glycidyl methacrylate between the lamellae of the DMA‐modified clay. The approach provides exfoliated nanocomposites as judged by the measurements of X‐ray diffraction. However, a low fraction of persistent intercalated clay regions was visible by transmission electron microscopy. X‐ray photoelectron spectra analyses indicate that the nanocomposites have PGMA‐rich surface. The clay/PGMA nanocomposites can be readily dispersed in ethanol. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 800–808     

Conjugated Polymers for Optoelectronic Applications

Novel conjugated polymers containing carbazole, phenothiazine or triphenylamine units in the main chain were designed and synthesized via Wittig, Knovenagel or Heck condensations respectively. A majority of them have good solubility in common organic solvents, high thermal stability and good hole-injection ability. Their diluted solutions in THF showed strong absorption with the absorption maximum in the range of 294∼470 nm and the optic band gaps located in the range of 1.90∼2.75 eV. When irradiated by ultraviolet or visible light, the diluted solutions in THF of the polymers emitted light from purple to yellow color with the emission maximum in the range of 347∼597 nm and the full width at half maximum located in the range of 59∼119 nm. Several polymeric light-emitting diodes (PLEDs) devices were fabricated using these polymers as light-emitting materials, and a double-layer device composed of ITO/PEDOT:PSS/PQTN/Mg:Ag showed a good performance, in which the maximum brightness was measured as 2434.0 cd/m² under a 11.0 V forward bias voltage. Photovoltaic devices were also investigated using these polymers as an active layer, and a device composed of ITO/PNB/PTCDI-C₁₃/Al showed a good performance, which was estimated to have external quantum efficiency at around 1% at 330 nm. From these preliminary experimental results, we may infer that these polymers are good light-emitting materials for PLEDs; while for photovoltaic applications, their absorption spectra need to be further improved to match the solar illumination.     

X-ray and UV photoelectron spectroscopy of Ag nanoclusters

The main purpose of the present work is to analyze a series of Ag nanoparticles (NPs) with different size or ligand functionalization by using X-ray photoelectron spectroscopy (XPS) and to identify the differences in the band-shape and energy peak position of photoemission spectra due to the particle dimension. A transmission electron microscopy characterization was performed, to verify the consistency of the results. Three types of samples were prepared starting from AgNO₃ water solution and adding different capping agents. In the first two cases, the formation of NPs was promoted by the reduction of silver ions Ag⁺¹ to metallic Ag⁰ through the addition of sodium borohydride, whereas in the last case, it was triggered by the exposure to UV light. Depending on the size of the NPs, a different physical behavior can be recognized. NPs with diameter of about 5 nm are characterized by the phenomenon of localized surface plasmon resonance (LSPR). The other type of samples having a diameter of about 1.5 nm presents discrete energy levels instead of electronic bands, and in this case, a typical fluorescence phenomenon can be observed. In the latter case, we can refer to such systems as nanoclusters. The XPS analyses were focused on the Ag 3D spectra looking for the possible shifts of the Ag doublet as a function of the particles size. The ultraviolet photoelectron spectroscopy with He II source was used for the investigation of possible changes in the valence band.     

Surface Modification of Polyurethanes with Covalent Immobilization of Heparin

Thrombus formation and blood coagulation is a major problem associated with blood contacting products such as catheters, vascular grafts, arteries, artificial hearts and heart valves. An intense research is being conducted towards the synthesis of new hemocompatible materials and modifications of surfaces with biological molecules. In this study, polyurethane (PU) films were synthesized in medical purity from diisocyanate and polyol without using any other ingredients and their surfaces were modified by covalent immobilization of heparin. Two types of heparin, unfractionated (UFH) and low molecular weight heparin (LMWH), were immobilized to investigate their effect on cell adhesion. The surface properties of the modified PUs were examined with ESCA, ATR-FTIR and AFM. ESCA results demonstrated sulfur peaks indicating the presence of heparin and AFM results showed the alteration of surface structure after coating with heparin. Cell adhesion studies were conducted with heparinized whole human blood. The surfaces of the UFH immobilized films resulted in lesser red blood cell adhesion in comparison to LMWH demonstrating strong anti-thrombogenic activity of the latter.     

近红外响应硫化铜纳米粒子/液晶弹性体复合材料研究

报道了一种新型近红外响应光热转换试剂/液晶弹性体复合材料.目前绝大多数近红外吸收的无机金属纳米粒子,由于自身或其稳定剂(如长链硫醇或季铵盐)的化学性质,会致使经典的Finkelmann两步硅氢化加成反应中所使用的催化剂中毒失活,从而极大地限制了无机金属纳米粒子/液晶弹性体复合材料的拓展与应用.为了解决这一科学问题,我们采用了两步硫醇-烯点击化学快速制备单畴取向液晶弹性体薄膜的技术,将对近红外光有强吸收的油溶性硫化铜纳米粒子,成功地掺杂入聚硅氧烷液晶弹性体体系中,制备了近红外响应的硫化铜纳米粒子/液晶弹性体复合薄膜.通过使用紫外可见光谱、透射电子显微镜、扫描电子显微镜、偏光显微镜、示差扫描量热法、变温广角X射线散射对该复合材料进行了深入的研究,结果表明:该薄膜材料在980 nm近红外光源的照射下,可以实现高效的光热转换,从而实现快速、可逆的二维伸缩运动.     

Interactions of Hydrogen with Pd@MOF Composites

Physisorption and chemisorption of hydrogen on solid-state materials are two fundamentally different interactions, both of which display advantages and drawbacks for hydrogen storage. It has been hypothesised that their combination by merging two classes of materials showing different sorption behaviour towards hydrogen in the same composite may synergistically combine their desirable properties. As representatives of such composites, palladium nanoparticles, nanoclusters, and single atoms have been encapsulated in a metal-organic framework matrix, embedded, or immobilised in its pores, respectively. In this minireview, we review advances on the understanding and potential applications of the combination of Pd with metal-organic framework matrices through the analysis of the nanocomposite materials’ interaction with hydrogen and sorption properties.