Biosynthesized gold nanoparticles supported on magnetic chitosan matrix as catalyst for reduction of 4-nitrophenol

The design and environmentally-safe synthesis of magnetically recoverable solid-supported metal nanoparticles with remarkable stability and catalytic performance have significant industrial importance. In the present study, we have developed an inexpensive bioinspired approach for assembling gold nanoparticles (AuNPs) in magnetic chitosan network under green, mild and scalable condition. AuNPs were well loaded on the surface of the magnetic support due to the presence of hydroxyl (-OH) and amino (-NH2) groups in chitosan molecules that provided the driving force for the complexation reaction with the Au(III) ions. Reduction of the Au(III) to Au(0) was is achieved by using Melicope ptelefolia aqueous leaf extract. The synthesized magnetic chitosan supported biosynthesized Au nanocatalyst was characterized using Fourier Transform Infrared (FT-IR), Carbon, Hydrogen and Nitrogen (CHN), Transmission Electron Microscopy (TEM), X-Ray Diffraction (XRD) and Atomic Absorption Spectroscopy (AAS) analyses. FTIR spectrum of magnetic chitosan showed peaks at 1570 cm-1, which indicate for N-H bending vibration and at 577 cm-1 which designates the Fe-O bond. CHN analytical data further supported the coating of chitosan onto the magnetite. TEM analysis showed an amorphous layer around the magnetite core, proving the coating of chitosan on the magnetite surface and the average particle size of AuNPs calculated was 7.34 ± 2.19 nm. XRD analysis showed six characteristics peaks for magnetite, corresponding to lattice planes (220), (311), (400), (422), (511) and (440) in both the magnetite and magnetic chitosan samples (JCPDS file, PDF No. 65-3107). Meanwhile, XRD analysis of catalyst showed characteristic peaks of AuNPs at 2 (38.21°, 44.38°, 62.2°, 77.32° and 80.76°), which correspond to (111), (200), (220), (311) and (222) lattice planes (JCPDS file, PDF No.04-0784). AAS analysis showed the loading of AuNPs as 5.4%. The rate constant achieved for the reduction of 4-nitrophenol to 4-aminophenol in the presence of hydrazine hydrate using 10 mg of catalyst was 0.0046 s-1. The magnetic chitosan supported AuNPs is effective as catalyst for the reduction of 4-nitrophenol

Synthesis of hydrogel from sugarcane bagasse extracted cellulose for swelling properties study

Insolubility of cellulose in common solvent had been a challenge in generating cellulose hydrogels. In the present work, hydrogels from sugarcane bagasse extracted cellulose and modify with synthetic polymer, poly (vinyl alcohol) (PVA) and cross-linker, glutaraldehyde (GA) was synthesize. Cellulose was isolated from sugarcane bagasse via pre-treatment with 4 vol% sulphuric acid (H2SO4) and 10 wt% sodium hydroxide (NaOH) solution. The cellulose extracted was dissolved in ZnCl2/CaCl2 solution at 65 ℃ to fabricate self-standing cellulose hydrogel without cross-linker. Another cellulose hydrogel was generated and immersed into 5 wt% GA solution to cross-link the cellulose chains. To improve the stability and swelling properties of cellulose, PVA was introduced into the hydrogel by using GA to cross-link cellulose chains with PVA chains. The resulting hydrogels were characterized with Attenuated Total Reflectance-Fourier Transform Infrared (ATR-FTIR) spectroscopy and solid state 13C Nuclear Magnetic Resonance (NMR) spectroscopy for structural determination. Three self-standing cellulose-based hydrogels, including regenerated cellulose (RC), GA cross-linked cellulose (C-GA), followed by PVA and GA cross-linked cellulose (CGA-PVA) were successfully generated from ZnCl2/CaCl2 dissolution system and each hydrogel possessed different physical aspects. The occurrence of chemical cross-linking reaction between cellulose, GA and PVA was further evidenced by the data analyzed from ATR-FTIR and NMR spectra. The swelling degree of hydrogels generally increase after the addition of PVA and GA into cellulose suspension, showing 52 % (RC), 80 % (C-GA) and 135 % (C-GA-PVA). C-GA-PVA possessed the best swelling capability and potential for possible application as water reservoir in agriculture

Chitosan-based adsorbents for the removal of metal ions from aqueous solutions

Wastewater containing heavy metal ions is one of the most serious environmental concerns. Exposure to elevated levels of heavy metals can adversely affect water resources, endangering the ecosystems and human health. Among the various treatment technologies, adsorption using biopolymer seems a promising alternative method. Chitosan is a natural polymer produced from chitin with excellent properties such as biocompatibility, biodegradability and non-toxicity. Moreover, chitosan is known as an effective sorbent due to the presence of amino and hydroxyl groups in its molecules which can serve as attachment sites towards metal ions. Recently, chitosan derivatives as metal ion sorbents have gained considerable attention. These derivatives are prepared by either physical or chemical modifications or both in order to improve chitosan properties in adsorption. This paper discusses recent developments in the modifications of chitosan and the application of the derived materials in the removal of metal ions from aqueous solutions. The mechanisms of adsorption, metal sorption capacities, effect of pH, isotherm and kinetic models are also described

Removal of copper ions from aqueous solutions using poly (Vinylbenzyl chloride)

Nowadays, contamination of copper (Cu(II)) has become one of the worst environmental problems. Due to its environmental resistance and persistence, the treatment of Cu(II) is crucial. Poly(vinylbenzyl chloride) (PVBC) was synthesised through reversible addition-fragmentation chain transfer (RAFT) polymerisation technique utilising monomer vinylbenzyl chloride (VBC), 4-cyanopentanoic acid dithiobenzoate (CPADB) as RAFT agent and 4,4ʹ-Azobis (4-cyanopentanoic acid) (ACPA) as initiator. This study aims to synthesise PVBC and to test the ability of PVBC to remove Cu(II) ions from aqueous solution. In this study, PVBC was successfully synthesised when reacted for 24 h at 80 °C, and the ability of the PVBC to adsorb and remove Cu(II) ions was investigated. Important adsorption parameters such as adsorbate concentration, adsorption dosage, and contact time were studied. The maximum Cu(II) adsorption capacity (qmax) of PVBC was 263.15 mg/g with a copper removal rate of 95% under optimum initial concentration (160 mg/L), adsorbent dosage (14 mg), and contact time (180 min). The experimental results better fit into the Langmuir adsorption isotherm model than the Freundlich model, and the kinetics experiments were compared with the pseudo-second-order kinetic model. Polymer adsorption efficiency was above 90% after five cycles of adsorption and desorption, but the overall adsorption capability of PVBC for Cu(II) ions began to decrease after another five cycles from 80% to 54%. Given the outcomes acquired, it can be concluded that PVBC can be an efficient and potential adsorbent for the removal of Cu(II) ions from aqueous solution. The adsorption study showed that PVBC has an affinity to Cu(II) ions. The prepared PVBC is potentially useful for wastewater treatment applications

Optimization of synthesis of poly (vinylbenzyl chloride) by RAFT polymerisation

One of the versatile radical polymerisation techniques, the reversible addition fragmentation chain transfer (RAFT) process, was used to synthesize the bifunctional monomer, vinylbenzyl chloride (VBC) into poly(vinylbenzyl chloride) (PVBC). The RAFT polymerisation technique is widely used because of the commercially available RAFT agent. The right choice of the RAFT agent will result in a good polymerisation. Temperature of 60°C and 80°C were chosen in this research study. The other conditions such as the purging and reaction time, the ratio of monomer/initiator for the control of VBC polymerisation were kept constant for all reaction. The reactions were monitored by 1H Nuclear Magnetic Resonance spectroscopy (NMR) in the presence of deuterated chloroform as the internal standard and Attenuated Total Reflection (ATR-FTIR). The highest monomer conversion was 57.7 % at 80°C for 24 hours

A review of the properties and applications of poly (Methyl Methacrylate) (PMMA)

Advances in the use of poly (methyl methacrylate) (PMMA) have opened up a wide range of applications in the field of nanotechnology. The knowledge of the properties of PMMA has contributed a lot to the recent boosts in the synthesis, modification, and applications of the polymer. However, there is a need to condense these developments in the form of an article for better understanding and easy access. This review highlights the fundamental physical properties of PMMA, coupled with experimental evidence of its essential chemistry, such as solubility, hydrolysis, grafting, combustion reactions, reactions with amines, and thermal decomposition. The recent developments in the applications of PMMA in biomedical, optical, solar, sensors, battery electrolytes, nanotechnology, viscosity, pneumatic actuation, molecular separations, and polymer conductivity were also revealed

Grafting of polyacrylonitrile onto sodium alginate using benzoyl peroxide as initiator

In this study, grafting of polyacrylonitrile onto sodium alginate was carried out in aqueous medium using benzoyl peroxide (BPO) as initiator. The graft copolymers were characterized by Fourier tansforms infrared spectroscopy, differential scanning calorimety, thermogravimetric analysis, and scanning electron microscopy. The eff€cts of reaction variables such as the ratio of monomer to sodium alginate, amount of BPO, reaction time and teinperature on the percentage grafting G (%) were studied. The optimum conditions for grafting were achieved at a ratio of sodium alginate to acrylonitrile of 1:3 by weight, 0.1 g of BPO and reaction temperature and time of 80"C and 4 h, respectively. These conditions provided highest percentage of grafting and yield of graft copolymerization of 125.s0% and 4t"g4yo, respectively. The results indicate that benzoyl peroxide could be used as thermal initiator for grafting polyacrylonitrile onto sodium alginate

Polymeric platinum conjugated drug for cancer treatment

This research focuses on the synthesis of new polymeric platinum conjugated drugs which were designed to mimic the classical platinum anticancer drug; cisplatin, for cancer treatment. Cisplatin is a promising and effective chemotherapy drug to treat various types of solid tumours. However, due to severe side-effects, low solubility and low targeting of cisplatin, polymeric carriers are employed to overcome these barriers. Reversible-addition fragmentation chain transfer (RAFT) polymerisation technique was used to generate linear polymers with good controlled and low molecular weight distributions. RAFT polymers with different molecular weights and functionalities were synthesised enabling different kinds of polymer-drug conjugates to be made. Modifications using ‘click’ techniques such as copper catalysed azide-alkyne cycloaddition (CuAAC) and thiol-click prior to conjugation of platinum drugs allow introduction of other moieties onto the polymer backbone such as hydrophiliccompounds, cell targeting moieties and intercalating agents or dyes to increase solubility, improve the cell uptake or just as a marker. The potential of these polymers as a polymer-drug conjugate to function as an anticancer drug for cancer treatment are justify in the biological in vitro studies such as cytotoxicity on cancer cell lines, DNA binding investigation and cell uptake studies

Enhanced drug toxicity by conjugation of platinum drugs to polymers with guanidine containing zwitterionic functional groups that mimic cell-penetrating peptides

Inspired by the Ringsdorf model, statistical copolymers with solubility enhancers, platinum drugs and groove binders were compared. In addition, the polymer was furnished with a cell penetrating moiety using a guanidine containing polymer. A block copolymer based on poly(4-vinylbenzyl chloride) and a block carrying zwitterionic monomer prepared from arginine was obtained using RAFT polymerization. Thiol–chloride reaction was then employed to attach thioglycerol (TG) as the water-soluble functional group, 9-aminoacridine (AA) as groove binder to enhance DNA binding and reactive diamino functionality as the bidentate ligand for the conjugation of platinum drugs. The aim of this work was to create a stable bond between the polymer and the drug to answer the question if it is essential to have degradable linkers to generate high drug activity. Three platinated polymers – having only the solubility enhancer, the solubility enhancer and the groove binder and with all three moieties – were compared in regards to their ability to enter the human ovarian carcinoma A2780 cells. Unsurprisingly, the zwitterionic polymer showed the highest uptake, which also coincided with a higher toxicity of the drug. Conjugated to the zwitterionic polymer, the platinum drug showed a higher toxicity than free cisplatin. In summary, even 40 years after the concepts was first established by Ringsdorf, this design still seems to have high validity highlighting that the suitable polymer design can enhance the activity of the drug

Graft copolymerization of methyl methacrylate onto alginate using benzoyl peroxide initiator

The graft copolymerization was carried out by methyl methacrylate with sodium alginate in which benzoyl peroxide (BPO) was used as initiator. It was found that the percentages of grafting and grafting yield were dependent on the concentration of methyl methacrylate (MMA), sodium alginate (NaAlg), BPO reaction temperature and reaction time. The optimum percentage of grafting was obtained when the concentration of BPO, MMA, and NaAlg were 4.13 × 10-3 mol L-1, 7.99 × 10-1 mol L-1 and 1% w/v, respectively. The optimum reaction temperature and time were 80°C and 2 h, respectively. The graft copolymers were characterized by using FTIR spectroscopy, thermogravimetric analysis, scanning electron microscopy and solid-state 13C-NMR spectroscopy. The plausible reaction mechanism of the graft copolymer formation using BPO initiating system has been proposed