Antibacterial activity of silver‐doped manganese dioxide nanoparticles on multidrug‐resistant bacteria

BACKGROUND: As a result of evolution of multiple drug resistance in human pathogens (bacteria) there is increasing demand for novel antibacterial agents, and recently, due to their high antibacterial and catalytic activities, metal nanoparticles have attracted the attention of researchers and medical microbiologists worldwide. RESULTS: Ni‐, Ce‐ and Ag‐doped MnO₂ nanoparticles were synthesized by a co‐precipitation method. Antibacterial activity of these synthesized nanoparticles on methicillin‐resistant Staphylococcus aureus and lead‐resistant Pseudomonas aeruginosa strain 4EA was investigated using a disc diffusion method. Only Ag‐doped MnO₂ nanoparticles showed an antibacterial property against methicillin‐resistant Staphylococcus aureus and lead‐resistant Pseudomonas aeruginosa strain 4EA at low levels of 60 µg/disc and 85 µg/disc, respectively. Scanning electron microscopy and transmission electron microscopy (SEM‐TEM) coupled with energy dispersive X‐ray (EDX) analysis revealed the nano‐size and composition of these synthesized nanoparticles. CONCLUSION: It was confirmed through a disc diffusion method that chemically synthesized silver doped MnO₂ nanoparticles have antibacterial activity against multidrug‐resistant Staphylococcus aureus and lead‐resistant Pseudomonas aeruginosa strain 4EA at low levels therefore these nanoparticles can be employed to fight and prevent infections caused by multidrug‐resistant bacterial pathogens. © 2012 Society of Chemical Industry     

Flame synthesis of mixed tin‐silver‐copper nanopowders and conductive coatings

The single‐step direct synthesis of tin‐silver‐copper nanopowders and nanostructured coatings using the flame‐based high‐temperature reducing jet (HTRJ) process is reported. Nanostructured coatings were deposited and sintered within the HTRJ reactor to study the effect of reductive sintering temperature on their electrical conductivity and surface morphology. Although the ultimate application of these nanoparticles is in printed electronics, which requires dispersing them as stable inks before depositing and sintering them, our approach of direct deposition from the gas phase provides an upper limit on the conductivity achievable with a given composition. The directly deposited coatings had high electrical conductivity, including a value of 2 × 10⁶ S/m for 36 wt % Cu‐40 wt % Ag‐24 wt % Sn sintered at 200°C. This is twice the conductivity of a pure silver coating prepared under similar conditions. Moreover, similarly high electrical conductivity was achieved using only 20% Ag with sintering at 300°C. © 2015 American Institute of Chemical Engineers AIChE J, 62: 408–414, 2016     

Enhanced photoluminescence property and mechanism of Eu3+‐doped tellurite glasses by the silver and gold nanoparticles

In this work, the silver or gold nanoparticle single‐existing and co‐existing tellurite glasses doped with Eu³⁺ were prepared, and the influence of gold or silver nanoparticles on the photoluminescence of tellurite glasses doped with Eu³⁺ were investigated. The photoluminescence of tellurite glasses doped with Eu³⁺ was enhanced by the surface plasmon absorption of gold or silver nanoparticles, and the maximum luminescence enhancement factors caused by the silver and gold nanoparticles are 4.8 and 3.5 factors, respectively. The differentiation of luminescence enhancement mechanisms caused by the gold or silver nanoparticles was demonstrated. The enhanced luminescence mechanism of the Au nanoparticle single‐existing tellurite glasses doped with Eu³⁺ was from the increasing of radiative decays rate caused by the Au nanoparticles. The excitation field enhancement caused by the Ag nanoparticles was responsible for the luminescence enhancement of the Ag single‐existing tellurite glasses doped with Eu³⁺. About 4.2‐factor luminescence enhancement was observed in the Ag and Au nanoparticle co‐existing tellurite glasses doped with Eu³⁺, which is attributed to the increasing of radiative decays rate and excitation field enhancement caused by the Au and Ag nanoparticles.     

A water‐soluble self‐doped conducting polypyrrole‐based copolymer

A water‐soluble self‐doped conducting polypyrrole‐based copolymer was synthesized via the grafting of pyrrole onto the p‐aminodiphenylamine moieties of a water‐soluble copolymer. The conductive copolymer exhibited a conductivity as large as 3.4 S/cm. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 86–89, 2001     

Optoelectronic performances on different structures of Al‐doped ZnO

ZnO films and Al‐doped ZnO (AZO) films were deposited on p‐Si substrate by magnetron sputtering to investigate its chemical composition, structural and photoelectric properties. XRD and FTIR show that Al ions can enter into the substitutional and interstitial site of ZnO crystal, and O atoms in AZO films are more abundant. Three different structures of Al‐doped ZnO (substitutional Al, interstitial Al, and O‐rich Al‐doped ZnO) were built using first‐principles method based on experimental results, charge density difference, and density of States (DOS) illustrate that there are strong ionic interactions between Al and O atoms in substitutional Al‐doped ZnO, moreover, substitutional and interstitial Al doping both are beneficial to N type, but oxygen‐enriched ZnO is not conducive to N type. Furthermore, the optical properties of 3 different Al‐doped ZnO structures were investigated respectively. Compared with pure ZnO, the real and imaginary part of dielectric function of O‐rich and interstitial Al have a significant increase and move to lower energy (red shift), the reflectivity of O‐rich is 3 times of pure ZnO and substitutional Al‐doped ZnO. The results are hoped to be helpful to study AZO thin film and predict the properties of Al‐doped ZnO.     

Acrylic acid‐doped polyaniline sensitive to ammonia vapors

Acrylic acid and HCl‐doped polyanilines were synthesized by chemical oxidative polymerization. The synthesized materials were used as sensors for ammonia. Comparison of the responses of the two polymers reveal that the acrylic acid‐doped polymer exhibits higher sensitivity and reversibility. Further, the resistance is observed to decrease on exposing the acrylic acid‐doped polyaniline to saturated ammonia vapors. A reversed trend is observed in the case of HCl‐doped polyaniline. The results are explained in terms of the differences in the chemical interactions of the two polymers with respect to ammonia vapors. The proposed mechanism is further supported by the X‐ray diffraction and FTIR analysis. The X‐ray diffractogram of acrylic acid‐doped polymer shows an enhancement in the crystallinity on exposure to ammonia vapors, while the HCl‐doped polymer exhibits a loss in crystallinity. The FTIR spectra shows a higher doping level in acrylic acid doped polymer as observed from the intense peak of the dopant ion at 1158 cm⁻¹, which is seen to be shifted to a lower wavenumber i.e. ∼1128 cm⁻¹ on exposing the polymer to ammonia vapors. On the other hand, in HCl‐doped polyaniline, the peak of the dopant ion ∼1120 cm⁻¹ is initially less intense, which is further suppressed on exposure to ammonia. Conductivity measurements show a large vapor‐induced increase in conductivity, in the case of ammonia‐exposed acrylic acid‐doped polyaniline, which results in the formation of a more crystalline‐conducting phase. Exactly the opposite results were obtained in the case of HCl‐doped polyaniline exposed to ammonia. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 79: 1994–1998, 2001     

Treatment of Fenton‐refractory olive oil mill wastes by electrochemical oxidation with boron‐doped diamond anodes

In this work, the electrochemical oxidation of an actual industrial waste with conductive diamond anodes has been studied. The wastewater is the effluent of a wastewater treatment plant consisting of a Fenton reactor followed by a settler and a sand filter, in which the wastes generated in an olive oil mill are treated. These wastes contain a residual chemical oxygen demand of nearly 700 mg dm^?3 which cannot be further oxidized with the Fenton process. The electrolyses were carried out under galvanostatic conditions, using a bench‐scale plant equipped with a single‐compartment electrochemical flow cell. Boron‐doped diamond (BDD) and stainless steel (AISI 304) were use as anode and cathode of the cell, respectively. The complete mineralization of the waste was obtained with high current efficiencies limited only by mass transport processes. This confirms that besides the hydroxyl radical‐mediated oxidation that occurs in the Fenton process, the electrochemical oxidation with conductive diamond electrodes combines other important oxidation processes such as direct electro‐oxidation on the BDD surface and oxidation mediated by other electrochemically formed compounds generated in this electrode. Copyright © 2006 Society of Chemical Industry     

A comparison of silver‐ and copper‐charged polypropylene feed spacers for biofouling control

Implementation of nanofiltration (NF) and reverse osmosis (RO) processes in treating traditional water sources can provide a steady‐state level of removal that eliminates the need for regeneration of ion exchange resins or granular activated carbon. Moreover, RO can help meet future potable water demands through desalination of seawater and brackish waters. The productivity of membrane filtration is severely lowered by fouling, which is caused by the accumulation of foreign substances on the surface and/or within pores of membranes. Microbial fouling, or biofouling, is the growth of microorganisms on the membrane surface and on the feed spacer as present between the envelopes. The fouling of membranes has demanded and continues to demand considerable attention from industry and research communities. Many of these applications use membranes in a spiral wound configuration that contains a feed spacer. The goal of this project was to develop low‐biofouling polypropylene (PP) spacers through the functionalization of PP by a spacer arm with metal chelating ligands charged with biocidal metal ions, investigate the use of this metal‐charged polypropylene (PP) feed spacers that target biofouling control, and to use some traditional and one novel techniques to autopsy the membranes after filtration to gain a better understanding of the biofouling mechanism and how the modified spacers are affecting it. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

3D‐foam‐structured nitrogen‐doped graphene‐Ni catalyst for highly efficient nitrobenzene reduction

We report the preparation of a porous 3D‐foam‐structured nitrogen‐doped graphene‐Ni (NG/NF) catalyst and the evaluation of its performance in the reduction of nitrobenzene (NB) through detailed studies of the kinetics. The NG/NF catalyst showed a significantly higher reaction rate than pure Ni foam (NF). Moreover, the separation of the 3D‐foam‐structured catalyst from the products was more convenient than that of NG powdered catalysts. The obtained kinetics data fit well to the Langmuir‐Hinshelwood model, with an error ratio below 10%. Density functional theory (DFT) calculations indicated that the adsorption of sodium borohydride (NaBH₄) on the NG/NF surface was stronger than that of NB, which strongly agreed with the kinetic parameters determined from the Langmuir‐Hinshelwood model. The excellent catalytic efficiency of the 3D‐foam‐structured catalyst combined with the knowledge of the kinetics data make this catalyst promising for application in larger scale nitrobenzene reduction. © 2017 American Institute of Chemical Engineers AIChE J, 64: 1330–1338, 2018     

Synthesis,Characterization, and Catalytic Activity of Mn‐doped Perovskite Oxides for Three‐Way Catalysis

Mn‐doped La_0.8Sr_0.2CoO₃ perovskite oxides (La_0.8Sr_0.2Co_1–xMn_xO₃; x = 0, 0.1, 0.3, 0.5) were synthesized by a modified sol‐gel method. The phase‐pure oxides were obtained. CoO and carbonates were formed on the surface of La_0.8Sr_0.2CoO₃. With increasing doping content, these impurities were reduced while the stability of the perovskite structure was improved. The valence state of B‐site ions and the amount of absorbed oxygen were influenced by Mn doping. The catalytic activity of the perovskite catalysts was investigated for CO oxidation and simultaneous removal of CO, C₃H₈, and NO. For CO and NO removal, La_0.8Sr_0.2Co_0.9Mn_0.1O₃ exhibited the best performance. For C₃H₈ removal, the reactivity was promoted linearly with the doping content. The structure‐activity relationship is also discussed.     

Design,synthesis and characterization of a novel self‐doped polyaniline derivative

A type of self‐doped polyaniline derivative was successfully synthesized using an oxidative coupling polymerization approach. The structure of the electroactive polymer was investigated using Fourier transform infrared and ¹H NMR spectroscopy and gel permeation chromatography. Its thermal and spectral properties were characterized using thermogravimetric analysis and UV‐visible spectroscopy. The electrochemical activity of the polymer was studied using cyclic voltammetry (CV) in 1.0 mol L^?1 H₂SO₄ solution with various scan rates. The peak current increases linearly with scan rate from 10 to 120 mV s^?1, which indicates that the electrode reaction is controlled by a surface process. In addition, the self‐doped characteristic was investigated using CV in 1.0 mol L^?1 KCl solution with pH value changing from 1 to 12, and the results indicate that the polymer has excellent electrochemical activity even in neutral and alkaline environments. Copyright © 2010 Society of Chemical Industry     

Electrochemical incineration of dyes using a boron‐doped diamond anode

The electrochemical oxidation of a synthetic wastewater containing the model dyes alizarin red (an anthraquinone) and Eriochrome black T (an azoic compound) has been studied on a boron‐doped diamond electrode (BDD) by both cyclic voltammetry and bulk electrolysis. The influence of the current density and dye concentration were investigated. The results obtained show that complete chemical oxygen demand (COD) and colour removal was obtained for both wastewaters. However, the nature of the pollutant, and specially the presence of functional groups (such as the azoic group) seems to strongly influence the performance and efficiency of the electrochemical process. The electro‐oxidation of alizarin red behaves as a mass‐transfer‐controlled process. In such a system, an increase in the current density leads to a decrease in the current efficiency. This can be explained by direct or hydroxyl radical mediated oxidation. The contrary tendency has been observed in Eriochrome black T electro‐oxidation. In this case, higher efficiencies were obtained working at high current densities. This may indicate that the mediated oxidation by electrogenerated reagent (such as peroxodisulphate) is the main oxidation mechanism involved in Eriochrome black T treatment. These compounds have a longer average lifetime than hydroxyl radicals, and it allows the reaction to be extended to the whole wastewater volume. This study has shown the suitability of the electrochemical process for completely removing the COD and total organic carbon and effectively decolourising of wastewaters containing synthetic dyes. Copyright © 2007 Society of Chemical Industry     

Electrical properties of dye‐doped colour tunable organic light emitting diode

In this work, we report on the electrical properties of dye‐doped colour tunable organic light‐emitting diode (OLED). The device structure is glass substrate/indium tin oxide/N,N′‐di(naphthalen‐1‐yl)‐N,N′‐diphenyl‐benzidine (NPB) 30 nm/Alq₃:DCM 50 nm/Aluminum (Al) 150 nm where NPB is the hole transport layer. Alq₃:DCM is the emitting layer which made of tris(8‐hydroxyquinoline) aluminium (Alq₃) doped with 4‐(Dicyanomethylene)‐2‐methyl‐6‐(4‐dimethyl‐aminostyryl)‐4H‐pyran (DCM) organic dye. The influence of doping concentration has been investigated by current density–voltage measurement, luminance intensity–voltage characteristic, electroluminescence (EL) and impedance spectroscopy, respectively. The EL spectrum exhibits the shifted of peak position from green to red region. The threshold voltage of the device decreased at the low DCM doping concentration (1 wt.%), in contrast, when the increase in the doping concentrations then the threshold voltage will be increased. The highest luminance intensity and lowest turn‐on voltage of OLED can be observed at doping concentration about of 1 wt.% of DCM. The impedance characteristics of the dye‐doped OLED can be modelled by simply adopting the conventional equivalent circuit with the simple combination of resistors and capacitors network. © 2012 Canadian Society for Chemical Engineering     

Hierarchical N‐doped carbons from designed N‐rich polymer: Adsorbents with a record‐high capacity for desulfurization

The removal of 4,6‐dimethyldibenzothiophene is quite challenging in petroleum refining process. Adsorptive desulfurization is an efficient technique but the capacities and/or poor stability of current adsorbents need to be improved. Here, the fabrication of hierarchical N‐doped carbons (NCs) derived from carbonizing the polymerization of 2,4,6‐tris(chloromethyl)mesitylene and p‐phenylenediamine is reported. The results show that the NCs have developed micropores (0.34–0.93 cm³ g^?1) and mesopores (0.15–0.47 cm³ g^?1), and their surfaces have abundant pyrrole‐like/graphitic N and topological defects and vacancies, and high cycle stability (6 cycles). The typical adsorbent NC‐700 shows a record‐high capacity of 2.91 mmol g^?1 under ambient conditions. The computational results show that the doped N is capable of promoting adsorptive strength by 0.055–0.178 eV. In conclusion, the obtained materials exhibit excellent performance for deep desulfurization, and this work may open up new avenues for the development of efficient adsorbents. © 2018 American Institute of Chemical Engineers AIChE J, 64: 3786–3793, 2018     

Hydrogen storage properties of B‐ and N‐doped microporous carbon

A B‐ and N‐doped microporous carbon has been synthesized via a substitution reaction. The obtained carbon exhibited much higher surface area than the previously reported B‐ and N‐doped carbon. The hydrogen storage measurements indicated that the B‐ and N‐doped microporous carbon had a 53% higher storage capacity than the carbon materials with similar surface areas. Furthermore, hydrogen storage via spillover was studied on Ru‐supported B‐ and N‐doped microporous carbon and a storage capacity of 1.2 wt % at 298 K and 10 MPa was obtained, showing an enhancement factor of 2.2. Ab initio molecular orbital calculations were also performed for the binding energies between the spiltover hydrogen atom and various sites on the doped carbon. The theoretical calculations can explain the experimental results well, which also shed light on the most favorable and possible sites with which the spiltover hydrogen atoms bind. © 2009 American Institute of Chemical Engineers AIChE J, 2009     

Adsorption of iodine on hydrogen‐reduced silver‐exchanged mordenite: Experiments and modeling

The adsorption process of iodine, a major volatile radionuclide in the off‐gas streams of spent nuclear fuel reprocessing, on hydrogen‐reduced silver‐exchanged mordenite (Ag⁰Z) was studied at the micro‐scale. The gas‐solid mass transfer and reaction involved in the adsorption process were investigated and evaluated with appropriate models. Optimal conditions for reducing the silver‐exchanged mordenite (AgZ) in a hydrogen stream were determined. Kinetic and equilibrium data of iodine adsorption on Ag⁰Z were obtained by performing single‐layer adsorption experiments with experimental systems of high precision at 373–473 K over various iodine concentrations. Results indicate approximately 91% to 97% of the iodine adsorption was through the silver‐iodine reaction. The effect of temperature on the iodine loading capacity of Ag⁰Z was discussed. The Shrinking Core model describes the data well, and the primary rate controlling mechanisms were macro‐pore diffusion and silver‐iodine reaction. © 2016 American Institute of Chemical Engineers AIChE J, 63: 1024–1035, 2017     

Formulation and characterization of compatibilized poly(lactic acid)‐based blends and their nanocomposites with silver‐loaded kaolinite

Biodegradable polymer nanocomposites have been developed in this study as materials for use in the packaging of moisture‐sensitive products. Poly(lactic acid) (PLA) was the main component of the nanocomposites with poly(butylene adipate‐co‐terephthalate) (PBAT) as flexibility enhancer. Tetrabutyl titanate was also added as a compatibilizer to enhance the interfacial affinity between PLA and PBAT by inducing the formation of some PLA/PBAT via transesterification during the melt blending process, thereby improving the mechanical properties of the blends. Silver‐loaded kaolinite synthesized via chemical reduction was also incorporated into the compatibilized blends for further property improvement. Herein, we report a novel biodegradable quaternary nanocomposite system with intercalated‐exfoliated clay dispersion that was uniquely achieved by increasing the interlamellar space between kaolinite layers through silver nanoparticle insertion. The resultant nanocomposites containing as little as 4 phr modified clay reduced the elongation at break from 213.0 ± 5.85% to 53.8 ± 1.81%, enhanced thermal stability (initial decomposition temperature increased from 378 °C to 399 °C) and exhibited a water vapor permeability reduction of 41.85%. On the basis of these properties, the developed nanocomposites are considered to be promising candidates for use in bio‐packaging applications to replace non‐biodegradable and petro‐based plastics. © 2014 Society of Chemical Industry