Addition Of Ammonium Persulfate Research Articles

Ultrafast Self-Healing, Superstretchable, and Ultra-Strong Polymer Cluster-Based Adhesive Based on Aromatic Acid Cross-Linkers for Excellent Hydrogel Strain Sensors.

Synthetic hydrogel strain sensors rarely exhibit a comprehensive combination of mechanical properties such as ultra-stretchability, ultrafast self-healing, and high sensitivity. Herein, seven small molecule enhanced mechanical behaviors of polymer-cluster based hydrogels are demonstrated. The oxidized polyethyleneimine/polymeric acrylic acid (ohPEI/PAA) hydrogels with aromatic formic acids as supramolecular cross-linkers are prepared by simultaneous formation of ohPEI polymer clusters and PAA upon the addition of ammonium persulfate. The optimized hydrogel adhesive exhibits comprehensive excellent properties, such as high extensibility (up to 12298%), real-time mechanical self-healing capability (<1s, 93% efficiency), high uniformity, underwater adhesivity, and water-sealing ability. The proper binding strength of hydrogel and skin (47kPa) allows the hydrogel to be utilized as highly sensitive (gauge factor:16.08), highly conductive (2.58mScm-1), and underwater strain sensors. Specially, the adhesive strength of the adhesive to wood after dehydration is extremely high, reaching up to 29.59MPa. Additionally, when glycerol is introduced, the obtained gel maintains the physical properties even at harsh-temperature conditions (-40to 80 °C). It presents that multiple and hierarchical non-covalent interactions including multiple hydrogen bonding interactions, π-π stacking, electrostatic interactions, and dipole-dipole interactions of polymer clusters, allow for the energy dissipation and contribute to the excellent performance of the hydrogel.

Fluorescence “turn-off–on” approach for the detection of niflumic acid and ammonium persulfate using 2,3-dialdehyde starch-cysteine-molybdenum nanoclusters as a nanosensor

Herein, fluorescent molybdenum nanoclusters are synthesized by using Schiff base 2,3-dialdehyde starch-cysteine derivative as a ligand and 2,3-dialdehyde starch-cysteine Schiff base (DCSB) protected molybdenum nanoclusters (MoNCs) are named as “DCSB-MoNCs”. The as-synthesized fluorescent DCSB-MoNCs were stable and exhibited blue fluorescence under excitation at 365 nm. The as-prepared DCSB-MoNCs were narrowly and homogeneously distributed with a mean size of 2.80 ± 1.10 nm. The fluorescence of DCSB-MoNCs is significantly quenched by niflumic acid through non-covalent interactions DC Schiff derivative. Upon the addition of ammonium persulfate (APS) to MoNCs, the non-covalent interactions are cleaved between DCSB-MoNCs and niflumic acid, resulting in restoration the fluorescence of DCSB-MoNCs. In this, niflumic acid acts as both analyte and quencher by using DCSB-MoNCs as a nanosensor, showing a good linear response in the range of 0.005–10 µM with a limit of detection (LOD) of 2.2 nM. Then, “turn off–on” mechanism was established for sensing of APS, exhibiting a wider linear response in the range of 25–55 µM. The developed nanoclusters were successfully applied to detect niflumic acid drug in biological samples (blood plasma and urine) and industrial wastewater.

Highly ordered polyaniline: synthesis, characterization and electrochemical properties

Crystallization of semi-crystalline polyaniline has been attempted by altering conditions such as nature of dopant acid and nature of oxidant by a one-pot chemical polymerization method. The samples were characterized by an array of analytical techniques. Highly ordered arrangement with sharp peaks was present in the X-ray powder diffraction pattern when ultrasonication of monomer solution was performed for 2 h before the addition of ammonium persulfate. The emeraldine salt form of PANI was confirmed for this sample from FTIR and Raman spectroscopy measurements. Thermal stability of this sample has been evaluated. Aggregation of ordered chains of PANI was evident in the SEM image. As the sample showed a BET surface area of 24.31 m2/g, its electrochemical behavior was determined by performing cyclic voltammetry and galvanostatic charge/discharge experiments. It was found to possess excellent electrochemical performances with a specific capacitance of 912.5 F g−1 m−1.

Polyaniline nanotubes prepared by one-step synergistic polymerization of aniline and acrylic acid

The electrochemical property of electrode materials greatly depends on their morphologies. This report introduces a novel and facile synthesis method for polyaniline (PANI) nanotubes from one-step synergistic polymerization of aniline and acrylic acid in an aqueous solution induced by the addition of ammonium persulfate (APS). The molar ratio of aniline to AA (Xani/AA) is found to have great influence on the morphology of the produced PANI. Hollow PANI nanotubes with an average inner diameter of 80 nm and outer diameter of 180 nm can be mainly produced when Xani/AA is not higher than 1. The electrochemical properties of the prepared PANI nanotubes have been investigated using a three-electrode system. The specific capacitance of PANI nanotubes can reach 436 F/g at a current density of 0.5 A/g in 1 mol/L H2SO4 solution. Furthermore, the specific capacitance of the PANI nanotube maintains 89.2% after 500 charging/discharging cycles at a current density of 0.5 A/g, indicating a good cycling stability.

Preparation of water-compatible molecular imprinted conductive polyaniline nanoparticles using polymeric micelle as nanoreactor for enhanced paracetamol detection

This paper reports the design and synthesis of a novel molecular imprinted conductive polyaniline (PANI) nanoparticles (NPs) using polymeric micelle as nanoreactor. In our strategy, an amphiphilic acrylic copolymer was firstly synthesized which self-assemble into micelles in aqueous solution. The aniline monomer and template molecules (paracetamol, PCM) were then immobilized into polymeric micelle owing to their interactions. The subsequent polymerization of aniline occurred within the micelle with the addition of ammonium persulfate (APS), leading to the formation of molecular imprinted PANI NPs. The resulting PANI NPs were characterized by various techniques, including Fourier transform infrared spectroscopy (FT-IR), thermal gravimetric analysis (TGA), and transmission electron microscopy (TEM). A highly sensitive and selective electrochemical sensor for detecting PCM was developed using the obtained molecular imprinted PANI NPs as recognition element. The obtained imprinted PANI sensor revealed not only high selectivity toward paracetamol, but also a wider linear range over paracetamol concentration from 0.4–100μM and 200–1000μM with a significantly lower detection limit of 50nM, compared to previously reported PCM electrochemical sensors. The wide linear range was attributed to numerous effective recognition sites among the PANI matrix due to the large specific surface area of PANI NPs, whereas the low detection limit should be attributed to the electrical conductivity of PANI which provides a direct path for the conduction of electrons from the imprinting sites to the electrode surface. In addition, good stability and repeatability have also been demonstrated. This work not only provides a new type of paracetamol sensor with good performance, more importantly it develops a novel imprinting strategy to prepare molecular imprinted conductive nanoparticles in aqueous solution. In addition, considering the versatility of the amphiphilic copolymers, this strategy can be extended to imprint other molecules and thus prepare advanced MIP sensors for a wide range of templates.

Chemical polymerization of pyrrole in the presence of l‐serine or l‐glutamic acid: Electrically controlled amoxicillin release from composite hydrogel

ABSTRACTPolypyrrole (PPy) was chemically prepared from aqueous solutions individually containing l‐serine or l‐glutamic acid, with the addition of ammonium persulfate as the oxidant. The electrical, XPS and FTIR characterizations indicated that the amino acids co‐doped the PPy backbone. TEM revealed that PPy presented a quasi‐spherical morphology with diameters in nanometric scale. The nanostructures of PPy‐glutamic acid efficiently adsorbed therapeutic doses of amoxicillin. Composite hydrogels were obtained by the entrapment of amoxicillin‐loaded PPy in polyacrylamide network. The antibiotic molecules can be subsequently released (or sustained) from composite hydrogel in response to application (or removal) of electrical stimulation. This tuning release profile can lead to promising drug delivery applications such as implantable devices and iontophoretic systems. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41804.

Research on increasing silicon etch rate in deep wet etching with tetramethyl ammonium hydroxide etchant

The etching characteristics of Si (1 0 0) in silicon deep wet etching with tetramethyl ammonium hydroxide solution, containing silicic acid and ammonium persulfate, were studied in this article. The phenomena associated with the addition of ammonium persulfate at intervals in tetramethyl ammonium hydroxide solution were analyzed, and the mechanism of interplay between ammonium persulfate and silicic acid for increasing etch rate was proposed. The influence of these phenomena on the etch rate and roughness of Si (1 0 0) was discussed. The addition of ammonium persulfate at a periodic interval of time to a tetramethyl ammonium hydroxide solution, especially at the temperature of 80 °C, resulted in remarkable ascending of silicon etch rate. The etch rate of Si (1 0 0) in tetramethyl ammonium hydroxide solution with adding ammonium persulfate at intervals was superior to the etch rate in tetramethyl ammonium hydroxide solution without adding ammonium persulfate at intervals. The highest etch rate of Si (1 0 0) (0.83 µm/min), calculated with the help of profiler, was achieved after etching in tetramethyl ammonium hydroxide solution with adding ammonium persulfate at an interval of 120 min. This method appears to be a good candidate in applications where high and stable etch rate is required in long-time etching.

Morphological studies of polyaniline nanocomposite based mesostructured TiO2 nanowires as conductive packaging materials

Polyaniline (PAni) nanocomposites were prepared via in situ emulsion polymerization using dodecylbenzene sulfonic acid (DBSA) as an emulsifier and doping agent in the presence of titanium dioxide nanowires (TiO2-NWs). Firstly, TiO2 nanoparticles (P25) were converted to TiO2 nanowires through a hydrothermal process using 10% NaOH, subsequently the TiO2-NWs were dispersed in a DBSA solution. After, the aniline monomer was added and the polymerization occurred on the addition of ammonium persulfate as an initiator in the absence of any added acid. The ratio of TiO2-NWs in the nanocomposites varied from 5 to 15 wt%. The tubular morphology and crystalline structure of the prepared PAni/TiO2 nanocomposites were analysed using scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD). Furthermore, the prepared nanocomposites have been characterized using different spectroscopic methods such as UV-visible spectroscopy and gel permeation chromatography (GPC). The thermal stability of the nanocomposites was characterized using thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC). In addition, the AC-conductivity of the prepared PAni/TiO2 nanocomposites was evaluated. The prepared nanocomposites can be used as conductive packaging materials.

Preparation of polyaniline submicro/nanostructures using l-glutamic acid: Loading and releasing studies of amoxicillin

Hybrid submicro/nanostructures of polyaniline (PANI) and l-glutamic acid (GA) were chemically prepared with the addition of ammonium persulfate (APS) as the oxidant. Different GA and APS concentrations were investigated in order to obtain the optimal conditions for the formation of high aspect ratio structures. TEM, electrical and XPS characterizations revealed that at monomer:amino acid:oxidant molar ratio of 1:0.25:1, the PANI presented a fibrillar morphology with diameters in submicro and nanometric scale, the structures were coating with the GA and the GA doped the PANI backbone. The fibrillar structures of GA coated-PANI efficiently adsorbed therapeutic doses of amoxicillin and controlled release of the drug can be achieved in function of pH environment, with a maximum cumulative release of 98% at pH 9 within 48h.

Synthesis and characterization of polyaniline‐multiwalled carbon nanotube nanocomposites in the presence of sodium dodecyl sulfate

AbstractPolyaniline‐carboxylic acid functionalized multi‐walled carbon nanotube (PAni/c‐MWNT) nanocomposites were prepared in sodium dodecyl sulfate (SDS) emulsion. First, the c‐MWNTs were dispersed in SDS emulsion then the aniline was polymerized by the addition of ammonium persulfate in the absence of any added acid. SDS forms the functionalized counterion in the resulting nanocomposites. The content of c‐MWNTs in the nanocomposites varied from 0 to 20 wt%. A uniform coating of PAni was observed on the c‐MWNTs by field‐emission scanning electron microscopy (FESEM). The PAni/c‐MWNT nanocomposites have been characterized by different spectroscopic methods such as UV‐Visible, FT‐Raman, and FT‐IR. The UV‐Visible spectra of the PAni/c‐MWNT nanocomposites exhibited an additional band at around 460 nm, which implies the induced doping of the MWNTs by the carboxyl group. The FT‐IR spectra of the PAni/c‐MWNT nanocomposites showed an inverse intensity ratio of the bands at 1562 and 1480 cm−1 as compared to that of pure PAni, which reveals that the PAni in the nanocomposites is richer in quinoid units than the pure PAni. The increase in the thermal stability of conductivity of the nanocomposites was due to the network structure of nanotubes and the charge transfer between the quinoid rings of the PAni and the c‐MWNTs. Copyright © 2008 John Wiley &amp; Sons, Ltd.

Characterization of Polyaniline Nanotubes Formed in the Presence of Amino Acids

AbstractSelf‐assembled nanotubular structures of polyaniline were chemically synthesized from solutions containing different amino acids with the addition of ammonium persulfate as the oxidant. The materials were characterized by SEM and a range of spectroscopic methods. Spectroscopic characterizations revealed that the synthesized materials had many features typical of chemically synthesized PANI. Some additional features were also found and have been ascribed to non‐conducting material formed in the initial stages of the reaction at a higher solution pH. However, UV‐vis and 13C NMR spectra point toward a conductive material as the final product of the reaction. Cyclic voltammetry results also indicate an electroactive final product that closely resembles regular PANI in its electrochemical characteristics.magnified image

Structure and Dynamics of Micelle-bound Human α-Synuclein

Misfolding of the protein alpha-synuclein (aS), which associates with presynaptic vesicles, has been implicated in the molecular chain of events leading to Parkinson's disease. Here, the structure and dynamics of micelle-bound aS are reported. Val3-Val37 and Lys45-Thr92 form curved alpha-helices, connected by a well ordered, extended linker in an unexpected anti-parallel arrangement, followed by another short extended region (Gly93-Lys97), overlapping the recently identified chaperone-mediated autophagy recognition motif and a highly mobile tail (Asp98-Ala140). Helix curvature is significantly less than predicted based on the native micelle shape, indicating a deformation of the micelle by aS. Structural and dynamic parameters show a reduced helical content for Ala30-Val37. A dynamic variation in interhelical distance on the microsecond timescale is complemented by enhanced sub-nanosecond timescale dynamics, particularly in the remarkably glycine-rich segments of the helices. These unusually rich dynamics may serve to mitigate the effect of aS binding on membrane fluidity. The well ordered conformation of the helix-helix connector indicates a defined interaction with lipidic surfaces, suggesting that, when bound to larger diameter synaptic vesicles, it can act as a switch between this structure and a previously proposed uninterrupted helix.

The Effect of Acid Washing and Fermentation Gravity on Mechanical Shear Resistance in Brewing Yeast

The effects of fermentation gravity and acid washing procedures on a brewing yeast strain's ability to resist mechanical shear in turbulent flow were investigated. Reynolds numbers of approximately 50,000 were calculated for experimental conditions with a specially developed pumping system. Higher-gravity fermentations lead to marginally increased, but statistically insignificant, cell rupture compared with lower-gravity fermentations. Cell populations remaining after shear application displayed marginally higher viability in higher-gravity fermentations. Acid washing procedures lead to an approximately sixfold decrease in cell viability compared with the controls. Cell wash water acidified with phosphoric acid lead to larger drops in viability than water alone. The addition of ammonium persulfate to an acid wash solution lead to increased viability losses when exposed to mechanical shear. β-(1→3)-Glucan in the cell wall was identified as contributing significantly to mechanical shear resistance.

Identification of Ungulate Hemoglobins for Law Enforcement

Identification of Ungulate Hemoglobins for Law Enforcement

Spectral Characteristics and Interconversions of the Reduced, Oxidized, and Oxygenated Forms of Purified Cytochrome o

Abstract Cytochrome o can be chemically reduced by excess dithionite and oxidized by ferricyanide and ammonium persulfate. The latter reagent is colorless and allows spectral observations in the Soret region. The spectrum of the form of the reduced cytochrome, which has absorption maxima at 576, 543, and 414 nm, is elicited in aerobic solution by enzymatic reduction with NADH, and when formed in this way the oxygenated form is very stable. When the solution is made anaerobic, the spectrum of the reduced (non-oxygenated) form appeared. The reduced form becomes spectrophotometrically detectable when the dissolved oxygen falls below 14 µm and is at half-maximal concentration at 6 µm oxygen. The reintroduction of oxygen results in reappearance of the spectrum of the oxygenated form. The addition of ammonium persulfate or sodium dithionite to the oxygenated form produced the oxidized or reduced cytochrome, respectively. Bubbling carbon monoxide through solutions of the oxygenated form shifted the absorption maxima to 566, 535, and 419 nm, which are the absorption maxima characteristic of the reduced cytochrome-carbon monoxide complex. Cyanide, which can bind to the oxidized form of cytochrome o, had no effect on the spectrum of the oxygenated form, but the formation of this form from oxidized cytochrome o and NADH was inhibited in the presence of cyanide. Hydrogen peroxide forms a complex with cytochrome o that has a spectrum similar to the spectrum of the oxygenated form.

Possible role of histones in regulation of nucleic acid synthesis

ALTHOUGH this paper will be concerned principally with our studies on the possible role of histones in regulation of nucleic acid synthesis, it seems pertinent to comment first upon the gel electrophoresis of histones. Butler has stated that the most satisfactory way of characterizing histones is the application of starch gel electrophoresis [S, 10, 111. We have found [ 121 that polyacrylamide gels are superior to starch gels in the separation of histones, and Reisfeld et al. [ 131 have reported success with this gel system in the electrophoresis of other cationic proteins. The gels are formed by mixing buffered tetramethy-ethylenediamine catalyst with 60 per cent acrylamide and 0.4 per cent N,N’-methylenebisacrylamide followed by addition of ammonium persulfate. The gels are formed in glass tubes and have a pH of 3 after polymerization. Samples are applied directly upon the gels in a density-stabilized layer, and electrophoresis is conducted in a glycine buffer at pH 4 for 4.5 hr at 15 ma. per tube. The gels are stained in amido black, and excess stain is removed electrically. Patterns obtained by electrophoresis of calf thymus histones are shown diagrammatically in Fig. 1 in comparison with patterns obtained by electrophoresis in starch gels. The bands shown in Fig. 1 C were found consistently by electrophoresis in polyacrylamide gels, and the bands are designated by Roman numerals. Bands II and IV, found in all calf thymus histone preparations examined in this laboratory, stained more heavily than the other bands and provided easily recognized and very reproducible reference points. The inclusion of a sample of unfractionated histone in each electrophoretic run of 6 samples facilitated the assignment of band identities in preparations of histone fractions. Band II was arbitrarily assigned a relative mobility (1~‘)