Preparation and Characterization of Activated Carbon from Microwave and Conventional Heated Almond Shells Using Phosphoric Acid Activation

Activated carbon production from almond shells using phosphoric acid activation agent was achieved by applying both conventional heating and microwave heating in succession. The morphology and surface properties of activated carbon were studied using thermogravimetric and differential gravimetric analysis, Fourier-transform infrared spectroscopy, scanning electron microscopy, and Brunauer–Emmett–Teller analysis. A surface area of 1128 m²/g was achieved by optimizing the microwave power (500?W), microwave application time (15?minutes), conventional heating time (45?minutes), conventional heating temperature (500?°C), and the phosphoric acid:sample ratio (0.7:1). An adsorption capacity of methylene blue of 148?mg/g and an iodine value of 791?mg/g was obtained for the prepared activated carbon.     

Poly(2-(dimethylamino)ethyl methacrylate) brushes fabricated by surface-mediated RAFT polymerization and their response to pH

In this study, well-defined, high density poly(2-(dimethylamino)ethyl methacrylate) [poly(DMAEMA)] brushes were fabricated by the combination of the self-assembly of a monolayer of RAFT agent and surface-mediated RAFT polymerization. The whole fabrication process of the poly(DMAEMA) was followed by water contact angles, grazing angle-Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and atomic force microscopy. Kinetic studies revealed a linear increase in poly(DMAEMA) film thickness with polymerization time, indicating that the chain growth from the surface was a controlled process. Characterization of the poly(DMAEMA) brushes, such as molecular weight and thickness determination, were measured by gel permeation chromatography, and ellipsometry, and the grafting density was estimated. The pH response of the poly(DMAEMA) brushes was further investigated and the results verified the “brush-like” to “mushroom-like” transition of the poly(DMAEMA) chains due to the reversible protonation/deprotonation upon changing the solution pH.     

Enamines of 1,3-dimethylbarbiturates and their symmetrical palladium(II) complexes: synthesis,characterization and biological activity

Transition Metal Chemistry - Three 1,3-dimethylbarbiturate-enamine derivatives and their symmetrical palladium(II) complexes were prepared and characterized by spectroscopic methods. In addition,...     

A Grafting Study on Partially Dehydrochlorinated Poly(vinyl chloride) by Atom Transfer Radical Polymerization

HCl elimination in low ratio was first carried out from poly(vinyl chloride) to increase allylic chlorines. Partially dehydrochlorinated poly(vinyl chloride), having a macroinitiator effect, was grafted with tert‐butyl methacrylate via atom transfer radical polymerization in the presence of CuBr/2,2′‐bipyridine at 64°C in tetrahydrofuran. Original poly(vinyl chloride) was also grafted with tert‐butyl methacrylate under the same conditions to compare with that of partially dehydrochlorinated poly(vinyl chloride). The graft copolymers were characterized by elemental analysis, FTIR, ¹H and ¹³C‐NMR, differential scanning calorimetry, and gel permeation chromatography (GPC). Thermal stabilities of the graft copolymers were investigated by thermogravimetric analysis as compared with those of the macroinitiators.     

Chemical modification of silica gel with synthesized Schiff base hydrazone derivative and application for preconcentration and separation of U(VI) ions from aqueous solutions

Schiff base hydrazone derivative (HL) sorbent was synthesized according to the literature to be used in the adsorption and preconcentration of U(VI) ions from aqueous solution and it was exposed to immobilization, and new solid support material was obtained. For this purpose, Schiff base hydrazone derivative (HL) was chemically bonded to silica gel surface immobilized 3-aminopropyl trimethoxysilane, then analyzed by Fourier transform infrared, Brunauer–Emmett–Teller, scanning electron microscopy and elemental analysis. The influence of the solution pH, amount of sorbent, contact time, temperature, foreign ion effect and initial U(VI) concentration was investigated. The maximum U(VI) uptake capacity was found to be 8.46 mg/g.     

Nafion-graphene composite film modified glassy carbon electrode for voltammetric determination of p-aminophenol

A Nafion-graphene (Nafion-GR) nanocomposite film modified glassy carbon electrode was fabricated by a simple drop-casting method, and used in the electrochemical detection of p-aminophenol (4-AP). Owing to the large surface area, good conductivity of GR and good affinity of Nafion, the sensor exhibited excellent electrocatalytic activity for the oxidation of 4-AP. The electrochemical behaviors of 4-AP on Nafion/GR film modified glassy carbon electrodes were investigated by cyclic voltammetry and differential pulse voltammetry. A calibration curve is constructed in the same matrix, urine, as the unknown samples to be analyzed. The Nafion-GR film modified electrode was linearly dependent on the 4-AP concentration and the linear analytical curve was obtained in the ranges of 0.5–200 μM with differential pulse voltammetry (DPV) and the detection limit was 0.051 μM. The Nafion-graphene nanocomposite modified electrode exhibited good reusability than pure graphene modified GCE. This procedure can be used for the determination of p-aminophenol in the presence of its degradation products and paracetamol. Finally, the proposed method was successfully used to determine p-aminophenol in local tap water samples in urine samples and pharmaceutical preparations.     

Thermo‐ and pH‐induced phase transitions and network parameters of poly(N‐isopropylacrylamide‐ co‐2‐acrylamido‐2‐methyl‐propanosulfonic acid) hydrogels

Dual temperature‐ and pH‐sensitive hydrogels composed of N‐isopropylacrylamide (NIPAM) and 2‐acrylamido‐2‐methyl‐propanosulfonic acid (AMPS) were prepared by free‐radical crosslinking copolymerization in aqueous solution at 22 °C. The mole percent of AMPS in the comonomer feed was varied between 0.0 and 7.5, while the crosslinker ratio was fixed at 5.0/100. The effect of AMPS content on thermo‐ and pH‐ induced phase transitions as well as equilibrium swelling/deswelling, interior morphology and network structure was investigated. The volume phase transition temperature (VPT‐T) was determined by both swelling/deswelling measurements and differential scanning calorimetry (DSC) technique. In addition, the volume phase transition pH (VPT‐pH) was detected from the derivative of the curves of the swelling ratio (dQ_v/dpH) versus pH. The polymer‐solvent interaction parameter (χ) and the average molecular mass between crosslinks ( ) of hydrogels were calculated from swelling ratios in buffer solutions at various pHs. The enthalpy (ΔH) and entropy (ΔS) changes appearing in the χ parameter of hydrogels were also determined by using the modified Flory–Rehner equation. The negative values for ΔH and ΔS indicated that the hydrogels had a negative temperature‐sensitive property in water, that is, swelling at a lower temperature and shrinking at a higher temperature. It was observed that the experimental swelling data of hydrogels at different temperature agreed with the modified Flory‐Rehner approach based on the affine network model. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1713–1724, 2008     

Building an Iron Chromophore Incorporating Prussian Blue Analogue for Photoelectrochemical Water Oxidation

The replacement of traditional ruthenium-based photosensitizers with low-cost and abundant iron analogs is a key step for the advancement of scalable and sustainable dye-sensitized water splitting cells. In this proof-of-concept study, a pyridinium ligand coordinated pentacyanoferrate(II) chromophore is used to construct a cyanide-based CoFe extended bulk framework, in which the iron photosensitizer units are connected to cobalt water oxidation catalytic sites through cyanide linkers. The iron-sensitized photoanode exhibits exceptional stability for at least 5 h at pH 7 and features its photosensitizing ability with an incident photon-to-current conversion capacity up to 500 nm with nanosecond scale excited state lifetime. Ultrafast transient absorption and computational studies reveal that iron and cobalt sites mutually support each other for charge separation via short bridging cyanide groups and for injection to the semiconductor in our proof-of-concept photoelectrochemical device. The reorganization of the excited states due to the mixing of electronic states of metal-based orbitals subsequently tailor the electron transfer cascade during the photoelectrochemical process. This breakthrough in chromophore-catalyst assemblies will spark interest in dye-sensitization with robust bulk systems for photoconversion applications.     

High density cationic polymer brushes from combined “click chemistry” and RAFT‐mediated polymerization

A simple method for preparing cationic poly[(ar‐vinylbenzyl)trimethylammonium chloride)] [poly(VBTAC)] brushes was used by combined technology of “click chemistry” and reversible addition‐fragmentation chain transfer (RAFT) polymerization. Initially, silicon surfaces were modified with RAFT chain transfer agent by using a click reaction involving an azide‐modified silicon wafer and alkyne‐terminated 4‐cyanopentanoic acid dithiobenzoate (CPAD). A series of poly(VBTAC) brushes on silicon surface with different molecular weights, thicknesses, and grafting densities were then synthesized by RAFT‐mediated polymerization from the surface immobilized CPAD. The immobilization of CPAD on the silicon wafer and the subsequent polymer formation were characterized by X‐ray photoelectron spectroscopy, water contact angle measurements, grazing angle‐Fourier transform infrared spectroscopy, atomic force microscopy, and ellipsometry analysis. The addition of free CPAD was required for the formation of well‐defined polymer brushes, which subsequently resulted in the presence of free polymer chains in solution. The free polymer chains were isolated and used to estimate the molecular weights and polydispersity index of chains attached to the surface. In addition, by varying the polymerization time, we were able to obtain poly(VBTAC) brushes with grafting density up to 0.78 chains/nm² with homogeneous distributions of apparent needle‐like structures. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012