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We report a novel and simple one step method for the synthesis of spherical gold nanoparticles (SGNPs) by the reduction of gold (III) chloride trihydrate (HAuCl 4 ) through a surfactant free single step method. High resolution transmission electron microscopy (HRTEM) was evaluated to depict the morphology of SGNPs. TEM images reveal the homogeneous spherical gold nanoparticles formation. The average diameter of single SGNPs was calculated to be ∼2.5 – 5 nm. In addition, the existence of gold nanoparticles was investigated by X-ray photoelectron spectroscopy (XPS) and UV-visible spectroscopy studies. Also, Surface plasmon resonance peak of SGNPs recorded via UV-visible spectroscopy. We expect the method introduced in our work may be more useful for the large-scale synthesis of gold nanomaterials and for multifunctional applications.

In this work, a copolymer (polyaniline(PANI)-copolymer(co)-polydiphenylamine (PDPA)) hybrid impregnated on graphene (Gra) nanosheets was examined. At first, graphene was synthesized by the oxidation of natural graphite employing modified Hummer’s method and subsequently reduced using hydrazine monohydrate. Then, interfacial chemical oxidative polymerization was engaged to synthesize PANI, PDPA, and copolymer (PANI/PDPA) along with graphene nanosheets in liquid–liquid (CHCl3/HCl) interface individually. During the polymerization process, PANI and PDPA chain grown well and dispersed homogeneously on the graphene nanosheets. Morphological and molecular vibrational analyses were confirmed by field emission scanning electron microscopy (FESEM) and Fourier transform infra red spectroscopy (FTIR). In addition, the electrochemically modified Gra-PDPA, Gra-PANI, and Gra-copolymer hybrids show good electrical conductivity ensured via cyclic voltammetry (CV). The enhanced electro-catalytic activity of Gra-PANI-co-PDPA-ME towards glucose with superior sensitivity 0.51 μ A/ μ M at 5 s was achieved. The combined existence and synergistic interaction amid of graphene, aniline and diphenoquinone diamine (DPDI 2 + ) provides enhanced electron transfer for the glucose oxidation. Also, Interference studies ensure that the fabricated sensor is best suitable for glucose sensing performance.

We report on the synthesis of an electrically conductive chitosan nanofibrous scaffold (NFS) by a “simple template free self-assembly method” from biopolymer chitosan in the presence of inorganic acids as dopants and ammonium persulphate (APS) as an initiator. The morphology of the chitosan nanofibers scaffold (CS-NFS) was examined by field emission scanning electron microscopy (FE-SEM). Physiochemical characterizations of the CSNFS were analyzed by Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis. It is found that the morphology and structure of the CS-NFS strongly depend on the kinds of dopant used. Cyclic voltammogram measurement reveals that CS nanofibers have high electrocatalytic activity compared to chitosan powder. The CS nanofibers are expected to be useful in electrical, optical, and electrochemical devices. Open image in new window

To simultaneously remove hydrogen sulfide and ammonia from hot coal gases, the ammonia decomposition abilities of various metal oxide catalysts were tested in the absence/presence of hydrogen sulfide, at 650 °C. Cobalt oxide, molybdenum oxide, and nickel oxide have high ammonia decomposition abilities (>95%) in the absence of hydrogen sulfide, but such abilities rapidly decreased during the reaction in the presence of hydrogen sulfide. To improve the simultaneous removal abilities of metal oxides, Zn-based catal sorbents were prepared via impregnation with various metals, such as cobalt, nickel, and molybdenum, on zinc oxide. The CZ-30 (promoted with 30 wt% cobalt oxide on zinc oxide) and NZ-30 (promoted with 30 wt% nickel oxide on zinc oxide) catal sorbents showed excellent sulfur removal capacities, which, calculated until the breakthrough point, were 0.35 and 0.39 g S/g catal sorbent, respectively, while MZ-30 promoted with molybdenum showed a low sulfur removal capacity of 0.08 g S/g catal sorbent. The ammonia decomposition ability of CZ-30, however, increased more than 18 times compared with Co3O4, whose ammonia decomposition ability was more than 95% until 465 min, even though the ammonia decomposition ability of NZ-30 sharply decreased after 30 min. The CZ catal sorbent is a good candidate for the simultaneous removal of ammonia and hydrogen sulfide.

A modified electrode was fabricated by grafting poly(2,5-dimethoxyaniline) (PDMA) onto multiwalled carbon nanotubes (MWNTs) and used for the electrocatalytic oxidation of ascorbic acid (AA). Cyclic voltammetry was used to fabricate the modified electrode and demonstrate the electroactivity of MWNT-g-PDMA-ME towards AA. Field emission scanning electron microscopy (FESEM) of MWNT-g-PDMA-ME revealed the combined presence of MWNT and PDMA. The MWNT-g-PDMA-ME exhibited excellent performance for AA at 320 mV with a high sensitivity (12.78 μA/mM) and linear concentration range of 1 to 5 mM (correlation coefficient of 0.9991). Differential pulse voltammetry (DPVs) showed that MWNT-g-PDMA-ME experiences negligible interference from other electro-active components.

Multiwalled carbon nanotubes (MWNTs) grafted chitosan (CS) nanowire (NW) was prepared by phase separation method. Glucose oxidase (GOx) was sequentially immobilized into MWNT-CS-NW to obtain MWNT-CS-NW/GOx biosensor. Field emission scanning electron microscopy (FESEM) images of MWNT-CS-NW/GOx reveals the existence of MWNT and CS. Cyclic voltammetry and amperometry were used to evaluate the electrochemical determination of glucose. The MWNT-CS-NW/GOx biosensor shows an excellent performance for glucose at +0.34 V with a high sensitivity (5.03 μA/mM) and lower response time (3 s) in a wide concentration range of 1–10 mM (correlation coefficient of 0.9988). In addition, MWNT-CS-NW/GOx biosensor possesses better reproducibility, storage stability and there is negligible interference from other electroactive components.

Conducting hybrid submicrostructures composed of chitosan (CS and silica-based conducting poly[N-(3-trimethoxysilylpropyl)aniline] (PTMSPA were prepared by graft copolymerization. The spherical and fibrous morphologies of the CS-PTMSPA hybrid submicrostructures could be observed by optical and field emission electron microscopy. Under room temperature conditions, the CS-PTMSPA graft copolymers possessed the uniformly distributed spherical submicroparticles with diameters in the range of ca. 400–1,000 nm. On the other hand, under ice cold conditions (5 °C), CS-PTMSPA showed the development of randomly oriented fiber bundles. The diameter of a single fiber was in the range of ca. 100–500 nm. These CS-PTMSPA fibers were obtained by a temperature-driven template-free self-assembly pathway. Spectroscopic and thermal evaluations confirmed that CS-PTMSPA graft copolymer had been prepared by an oxidative polymerization method. The electrochemical performance of the CS-PTMSPA submicrostructures were compared with CS and PTMSPA by cyclic voltammetry with the Fe(CN)63−/4− system as a redox marker. The CS-PTMSPA submicrostructures showed high electrical conductivity (difference between the anodic and cathodic peaks = 0.24 and 0.29 V for CS-PTMSPA sphere and fiber, respectively compared to those of CS (0.14 V and PTMSPA (0.20 V), which was ascribed to the relatively high surface-to-volume ratios of these submicrostructures. Open image in new window

A new regenerable alumina-modified sorbent was developed for CO2 capture at temperatures below 200 °C. The CO2 capture capacity of a potassium-based sorbent containing Al2O3 (KAlI) decreased during multiple CO2 sorption (60 °C) and regeneration (200 °C) tests due to the formation of the KAl(CO3)(OH)2 phase, which could be converted into the original K2CO3 phase above 300 °C. However, the new regenerable potassium-based sorbent (Re-KAl(I)) maintained its CO2 capture capacity during multiple tests even at a regeneration temperature of 130 °C. In particular, the CO2 capture capacity of the Re-KAl(I)60 sorbent which was prepared by the impregnation of Al2O3 with 60 wt.% K2CO3 was about 128 mg CO2/g sorbent. This excellent CO2 capture capacity and regeneration property were due to the characteristics of the Re-KAl(I) sorbent producing only a KHCO3 phase during CO2 sorption, unlike the KAlI30 sorbent which formed the KHCO3 and KAl(CO3)(OH)2 phases even at 60 °C. This result was explained through the structural effect of the support containing the KAl(CO3)(OH)2 phase which was prepared by impregnation of Al2O3 with K2CO3 in the presence of CO2.

A novel amperometric cholesterol biosensor was fabricated by the immobilization of ChOx (cholesterol oxidase) onto the chitosan nanofibers/gold nanoparticles (designated as CSNFs/AuNPs) composite network (NW). The fabrication involves preparation of chitosan nanofibers (CSNFs) and subsequent electrochemical loading of gold nanoparticles (AuNPs). Field emission scanning electron microscopy (FE-SEM) was used to investigate the morphology of CSNFs (sizes in the range of ∼50–100 nm) and spherical AuNPs. Cyclic voltammetry, hydrodynamic voltammetry and amperometry were used to examine the performance of CSNF–AuNPs/ChOx biosensor. The CSNF–AuNPs/ChOx biosensor exhibited a wide linear response to cholesterol (concentration range of 1–45 μM), good sensitivity (1.02 μA/μM), low response time (∼5 s) and excellent long term stability. The combined existence of AuNPs within CSNFs NW provides the excellent performance of the biosensor towards the electrochemical detection of cholesterol.

Synthesis of nine Task Specific Ionic liquids (TSILs), their characterization using1H NMR spectral studies and other physical properties and potential applications in the removal of certain heavy metals such as Nickel, Iron, Zinc, Copper and Lead has been studied. The removal of these heavy metals from the industrial effluents / contaminated water bodies using these ionic liquids has been proved to be more successful than conventional methods such as precipitation, cementation, reverse osmosis, ion exchange and adsorption.

The preparation and characterization results of a new nanocomposite, polyaniline (PANI) grafted multiwalled carbon nanotube (MWNT) loaded Nafion-silica, (designated as Nafion-silica/MWNT-g-PANI), are reported in this paper. The preparation involves the formation of a silica network in a Nafion membrane and the subsequent loading of polyaniline-grafted multiwalled carbon nanotubes (MWNT-g-PANI) onto the Nafion-silica nanocomposite. The new nanocomposite, Nafion-silica/ MWNT-g-PANI, was characterized as to its morphology, structure and properties. The conductivity and methanol permeability of the nanocomposite membranes were evaluated.

Multiwalled carbon nanotubes (MWNTs) was grafted onto silica network (MWNT–silica-NW) by sol–gel process. MWNT–silica-NW was further electrodeposited with gold nanoparticles (AuNPs). The morphology of the GC/MWNT–silica-NW–AuNPs modified electrode (ME) was analyzed by field emission scanning electron microscopy (FE-SEM). Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were used to evaluate the electrochemical performances of GC/MWNT–silica-NW–AuNPs-ME. Ascorbic acid (AA) was found to be electrocatalytically oxidized at GC/MWNT–silica-NW–AuNPs-ME due to the synergistic influence of MWNTs, silica-NW and AuNPs. The MWNT–silica-NW–AuNPs-ME sensor electrode presents a high sensitivity (8.59 μA/mM) and selectivity for AA in the presence of dopamine (DA). Differential pulse voltammetry revealed that the sensor electrode exhibited excellent selectivity for AA in the presence of large excess of DA with a large potential separation of ∼0.26 V. The effective electrocatalytic activity, excellent peak resolution and ability for independent determination of DA in the presence of AA reveal that MWNT–silica-NW–AuNPs-ME is suitable for simultaneous and selective determination of DA and AA.

A glucose biosensor was fabricated with loading of glucose oxidase (GOx) into a new organic-inorganic hybrid nanocomposite. The preparation involves formation of silica network into a Nafion (perfluorosulfonate ionomer) and subsequent loading of polyaniline grafted multiwalled carbon nanotubes (MWNT-g-PANI) onto Nafion-silica nanocomposite. Field emission scanning electron microscopy (FE-SEM) of Nafion-silica/MWNT-g-PANI composite reveals the presence of spherical silica particles (sizes in the range 250 nm-1 microm) and tubular MWNT-g-PANI particles. Chronoamperometry and cyclic voltammetry were used to evaluate the performance of biosensor towards glucose. The Nafion-silica/MWCNT-g-PANI/GOx biosensor exhibited a linear response to glucose in the concentration range of 1-10 mm with a correlation coefficient of 0.9972, good sensitivity (5.01 microA/mm), a low response time (approximately 6s), repeatability (R.S.D value of 2.2%) and along-term stability. The presence of silica network within Nafion and MWNT-g-PANI synergistically contributes to the performance of the biosensor towards the electrochemical detection of glucose.

Kinetics of Pd (core)–Au (shell) nanoparticles (NPs) catalyzed transformation of dihydronicotinamide adenine dinucleotide (NADH) to NAD + was monitored by UV–vis spectroscopy. Pd (core)–Au (shell) NPs were prepared by microwave irradiation method. High resolution transmission electron microscopy image reveals the core–shell morphology. X-ray diffraction pattern shows the presence of distinct crystalline domains for Pd and Au. The changes in absorbances at 340 nm were followed for various time intervals. Rates of conversion of NADH to NAD + were determined for different conditions. The conversion of NADH to NAD + was to be first order with respect to NADH at lower concentrations (upto 0.04 mM) and pseudo-first-order beyond 0.04 mM. Rate constants for the Pd (core) Au–(shell) NPs catalyzed transformation of NADH to NAD + were deduced.

A layer-by-layer (LbL) film assembly was constructed that comprises alternative layers of poly(diphenylamine) (PDPA) and phosphotungstic acid (PTA). First, a layer of oxidized PDPA (referred to as PDPA(+)) was deposited by electropolymerization. Then, a layer of negatively charged PTA was deposited on the PDPA(+) layer . This processes was repeated several times to obtain multilayer LbL film (PDPA/PTA)n, where n is the number of double layers. The LbLs were characterized by UV-Vis spectroscopy, FT-IR spectroscopy and X- ray diffraction spectroscopy. The process of formation of the LbL assembly was monitored by electrochemical methods. Electrochemical studies revealed that this LbL film possesses a remarkable electrocatalytic activity towards oxidation of ascorbic acid in neutral aqueous medium. The enhanced electrocatalytic activity of (PDPA/PTA)n LbL film is attributed to the existence of tungsten atoms in the interlayers of PDPA.

A novel amperometric biosensor was fabricated based on the immobilization of cholesterol oxidase (ChOx) into a cross-linked matrix of chitosan (Chi)-room-temperature ionic liquid (IL) (1-butyl-3-methylimidazolium tetrafluoroborate). Initially, the surface of bare electrode (indium tin oxide coated glass) was modified with the electrodeposition of Au particles onto thiol (-SH) functionalized multi-walled carbon nanotubes (MWNTs). The biosensor electrode is designated as MWNT(SH)-Au/Chi-IL/ChOx. Scanning electron microscopy image of MWNT(SH)-Au/Chi-IL/ChOx reveals that Chi-IL exists as the interconnected wires covering the Au particles on the surface of MWNT(SH)-Au. Cyclic voltammetry and chronoamperometry were used for the electrochemical determination of cholesterol at the biosensor electrode, MWNT(SH)-Au/Chi-IL/ChOx. The presence of Au particles in the matrix of CNTs provides an environment for the enhanced electrocatalytic activities. The MWNT(SH)-Au/Chi-IL/ChOx biosensor exhibited a linear response to cholesterol in the concentration range of 0.5-5mM with a correlation coefficient of 0.998, good sensitivity (200 microAM(-1)), a low response time ( approximately 7s), repeatability (R.S.D value of 1.9%) and long term stability (20 days with a decrease of 5% response). The synergistic influence of MWNT(SH), Au particles, Chi and IL contributes to the excellent performance for the biosensor.

We report an ingenious approach for the fabrication of a promising glucose sensor, GOx/Au/CS–IL–MWNT(SH), that exploits the synergistic beneficial characteristics of multiwalled-carbon nanotubes (MWNTs), gold nanoparticles (AuNPs), chitosan (CS) and room temperature ionic liquid (RTIL). Direct electron transfer between glucose oxidase (GOx) and electrode was achieved. Scanning electron microscopy and atomic force microscopy images of GOx/Au/CS–IL–MWNT(SH) reveal that MWNTs and AuNPs are dispersed in CS–IL matrix. Cyclic voltammetry, impedance spectroscopy and chronoamperometry were used to evaluate the performance of biosensor. The GOx/Au/CS–IL–MWNT(SH) biosensor exhibits a linear current response to glucose concentration (1–10 mM) at a low potential of 0.10 V and precludes interferences from uric acid and ascorbic acid. The GOx/Au/CS–IL–MWNT(SH) biosensor has superior performances over GOx/CS–IL–MWNT(SH). Keywords: Direct electrochemistry, Chitosan, Glucose oxidase (GOx), Ionic liquid, Glucose sensor

A simple, rapid and efficient route to prepare polyaniline nanostructures (PANI-NS) by “one-step chemical oxidative polymerization” method is described. This method possesses advantages in terms of good yield, short reaction time, neat conditions and cost-effectiveness. The morphology of the PANI-NS was investigated by field-emission scanning electron microscopy (FE-SEM). The average diameter of single PANI-NS was calculated to be ∼376 nm. Results from UV–visible spectroscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis and cyclic voltammetry (CV) reveals the existence of PANI units present in the polymeric nanostructures. Also, electrical conducting property of the PANI-NS was analyzed using four-probe measurement method.

The effects of the SnO2 pore size and metal oxide promoters on the sensing properties of SnO2-based thick film gas sensors were investigated to improve the detection of very low H2S concentrations (

The sensing behavior of SnO(2)-based thick film gas sensors in a flow system in the presence of a very low concentration (ppb level) of chemical agent simulants such as acetonitrile, dipropylene glycol methyl ether (DPGME), dimethyl methylphosphonate (DMMP), and dichloromethane (DCM) was investigated. Commercial SnO(2) [SnO(2)(C)] and nano-SnO(2) prepared by the precipitation method [SnO(2)(P)] were used to prepare the SnO(2) sensor in this study. In the case of DCM and acetonitrile, the SnO(2)(P) sensor showed higher sensor response as compared with the SnO(2)(C) sensors. In the case of DMMP and DPGME, however, the SnO(2)(C) sensor showed higher responses than those of the SnO(2)(P) sensors. In particular, the response of the SnO(2)(P) sensor increased as the calcination temperature increased from 400 °C to 800 °C. These results can be explained by the fact that the response of the SnO(2)-based gas sensor depends on the textural properties of tin oxide and the molecular size of the chemical agent simulant in the detection of the simulant gases (0.1-0.5 ppm).

A sensitive spectrofluorimetric method has been developed for the determination of moxifloxacin (MOX) using europium(III)–MOX complex as a fluorescence probe in the presence of an anionic surfactant, sodium dodecyl benzene sulfonate (SDBS). The fluorescence (FL) intensity of Eu 3+ was enhanced by complexation with MOX at 614 nm after excitation at 373 nm. The FL intensity of the Eu 3+ –MOX complex was significantly intensified in the presence of SDBS. Under the optimum conditions, it was found that the enhanced FL intensity of the system showed a good linear relationship with the concentration of MOX over the range of 1.8 × 10 −11 –7.3 × 10 −9 g mL −1 with a correlation coefficient of 0.9998. The limit of detection of MOX was found to be 2.8 × 10 −12 g mL −1 with relative standard deviation (RSD) of 1.25% for 5 replicate determination of 1.5 × 10 −8 g mL −1 MOX. The proposed method is simple, offers higher sensitivity with wide linear range and can be successfully applied to determine MOX in pharmaceutical and biological samples with good reproducibility. The luminescence mechanism is also discussed in detail with ultraviolet absorption spectra.

We report on the fabrication of polyvinylidenefluoride (PVdF) PVdF/PbS and PVdF/PbS/Au heterogeneous nanostructures by the processes, electrospinning and chemical treatment. Initially electrospinning a solution consisting of PVdF and lead acetate was used to form PVdF nanofibers loaded with Pb ions. Exposure of Pb ions loaded PVdF fibers to H2S resulted in PVdF/PbS nanostructures. The deposition of gold nanoparticles onto PVdF/PbS nanostructures results in PVdF/PbS/Au heterogeneous structure. The existence of PbS particles with an average diameter of 11 nm is evident from field emission transmission electron microscopy (FETEM) image of PVdF/PbS. The results from X-ray diffraction of PVdF/PbS also predict the size of PbS particles as in accordance with FETEM. A blue shift in the optical transition of PbS is noticed in the UV-visible spectrum of PVdF/PbS as a result of quantum confinement effect. The band gap of PbS is influenced by the presence of Au nanoparticles over the PbS particles. An equal atomic weight % of Au and PbS is found in the PVdF/PbS/Au nanostructure as inferred from energy dispersive X-ray spectroscopy (EDX). Photoluminescence (PL) spectra of PVdF/PbS and PVdF/PbS/Au are compared. Emission peaks are noticed at 400 nm and 480 nm for PVdF/PbS and PVdF/PbS/Au nanostructures respectively for an excitation wavelength of 254 nm. The presence of Au nanoclusters in PVdF/PbS/Au diminishes the intensity of photo emission of PbS.