Hamad Khalid

Review on synthesis of ferrocene-based redox polymers and derivatives and their application in glucose sensing

The interest in glucose biosensors persisted over many years and persistent efforts have been made to develop long term stable glucose biosensors with precision, smart analytical performance, good linearity and resistance to communal interferences. In this regard, ferrocene-based polymers and derivatives (FBPDs) for the development of glucose biosensor (GBs) as redox mediators have acquired utmost attention of the scientists, especially in the second generation biosensors, as a large number of innovative molecules have been synthesized. Most of the FBPDs are considered as active components in the development of GBs, due to their ease of modification, biocompatibility, stability, large surface area, good electrical conductivity and especially excellent redox properties. This review provides a brief description of synthesis, analytical performance and glucose sensing application of ferrocene-based dendrimers, polythiophenes, polypyrroles, polyethylenimine, chitosan and carbon nano tubes (CNTs). Moreover, the analytical performance of ferrocene-based glucose biosensors (FBGBs) is summarized and the problems associated with the construction of GBs and the future trends are discussed.

Ferrocene-based polyethyleneimines for burning rate catalysts

Ferrocene-based polymers and their derivatives have the ability to catalyze the burning process of composite solid propellants efficiently. However, the simple and volatile ferrocene migrates to the surface of the solid propellant on prolonged storage, which alters the designed burning parameters and more seriously causes unexpected explosions. To retard migration problems, six novel ferrocene-based polyethyleneimines (PEI-Fcs) were synthesized by the condensation reaction of branched polyethyleneimine (PEI) with ferrocenecarbonyl chloride. The structures of the synthesized PEI-Fcs were characterized using 1H NMR, FT-IR and UV-Vis spectroscopy. The redox properties of the polymers are very important for burning rate catalysts (BRCs). Cyclic voltammetry (CV) revealed that all the PEI-Fcs showed redox properties due to the presence of ferrocene moieties. Migration studies confirmed that the migration of these PEI-Fcs was much slower than that of 2,2-bis(ethylferrocenyl)propane (catocene) and ferrocene. The catalytic effect of PEI-Fcs on the thermal decomposition of ammonium perchlorate (AP) was investigated using thermogravimetry (TG) and differential thermogravimetry (DTG). It was found that in the presence of PEI-Fcs (1–6), the peak decomposition temperature of AP was shifted towards the left (decreased) significantly. The results from the TG and DTG analysis indicated that the novel PEI-Fcs had good catalytic effects of lowering the thermal decomposition temperature of AP and were almost stable up to 220 °C. We expect that these novel PEI-Fcs would have great value as high BRCs for composite solid propellants.

Recent progress in Fe3O4 based magnetic nanoparticles: from synthesis to application

Fe3O4 based magnetic polymer nanoparticles (MPNPs) are densely studied for several decades. These Fe3O4 based MPNPs can be used in wastewater treatment and biological field such as magnetic resonance imaging contrast agents, hyperthermia therapy and protein separation. The Fe3O4 based MPNPs are attractive because they combine the advantages of magnetism and polymers together. In order to obtain the practical application in the above mentioned areas, the bare Fe3O4 needs to be functionalised with different kinds of molecules like organic small molecules and polymers and some inorganic molecules like silica, metals and carbon. In this review, the chemical preparation methods, different modification methods and various applications of the Fe3O4 based MPNPs are introduced.

Synthesis of ferrocene-based polythiophenes and their applications

Individually, ferrocene and thiophenes have incredible properties and important applications. During the last two decades, scientists synthesized polythiophenes containing ferrocene in the main and side chains. Polythiophenes have redox, conducting, and optical properties. Because of these properties, polythiophenes have been used in sensing applications. In addition, ferrocene has reversible redox properties and accordingly has been used in a lot of sensing devices, such as glucose sensing. Ferrocene can have +2 or +3 oxidation state, which can correspond to “0” and “1”, and thus can be used as a memory storage material. When these two moieties are combined together, they show good compatibility. Therefore, the resulting materials/polymers have been used in memory storage and chemical sensing devices. Thus, we carefully selected studies that are only associated with ferrocene-based polythiophenes. In this review, we tried to focus on the synthesis and applications of ferrocene-based polythiophenes. There are many methods for the polymerization of thiophenes. Here, we discussed the electrochemical polymerization, oxidation polymerization, nickel mediated coupling reactions, and Suzuki polycondensation. In addition, polythiophenes can be decorated with ferrocene, pre- or post-polymerization. These materials were examined for important applications, including information storage, DNA sensing, protein sensing, and glucose sensing materials.

Synthesis of Ferrocene-Based Hyperbranched Polyether and Its Catalytic Performance for Thermal Decomposition of Ammonium Perchlorate

A series of ferrocene-based hyperbranched polyethers (HBPE-Fc) with different ferrocene content were synthesized by esterification of ferrocenecarbonyl chloride and hyperbranched polyether (HBPE). 1H NMR and FT-IR were used to confirm the structure of HBPE and HBPE-Fc. GPC was used to calculate the molecular weights. The catalytic performance of the synthesized HBPE-Fc for thermal decomposition of ammonium perchlorate (AP) was investigated by TG and DTG techniques. The results showed that HBPE-Fc exhibited good catalytic activity on the thermal decomposition of AP. The influence factors on catalytic performances, such as substitution degree of ferrocene and mass ratio of AP/HBPE-Fc were discussed as well.

Synthesis of ethylene diamine-based ferrocene terminated dendrimers and their application as burning rate catalysts.

Ferrocene-based derivatives are widely used as ferrocene-based burning rate catalysts (BRCs) for ammonium perchlorate (AP)-based propellant. However, in long storage, small ferrocene-based derivatives migrate to the surface of the propellant, which results in changes in the designed burning parameters and finally causes unstable combustion. To retard the migration of ferrocene-based BRCs in the propellant and to increase the combustion of the solid propellant, zero to third generation ethylene diamine-based ferrocene terminated dendrimers (0G, 1G, 2G and 3G) were synthesized. The synthesis of these dendrimers was confirmed by 1H NMR and FT-IR spectroscopy. The electrochemical behavior of 0G, 1G, 2G and 3G was investigated by cyclic voltammetry (CV) and the burning rate catalytic activity of 0G, 1G, 2G and 3G on thermal disintegration of AP was examined by thermogravimetry (TG) and differential thermogravimetry (DTG) techniques. Anti-migration studies show that 1G, 2G and 3G exhibit improved anti-migration behavior in the AP-based propellant.

Redox and Temperature Dual Responsive Gel Based on Host–Guest Assembly

Stimuli-responsive hydrogels undergo shape transformation in response to change in ambient environment and have potential applications in tissue engineering, robotics, actuator and biosensing. Generally, the Stimuli-responsive hydrogels are controlled by unique external stimuli and the response is also specific. Here, we developed redox-regulated and temperature responsive macroscopic gel assembly system, using polyacrylamide-based hydrogel, which was functionalized with ferrocene (Fc) as a guest hydrogel and poly(N-isopropylacrylamide) (PNIPAAm) gel modified with β-cyclodextrin as a host hydrogel. It was observed that the variations in the redox potential induced reversible assembly/dissociation transition in a bi-gel strip and optimization of βCD contents provided fast bending speed and large bending degree, which can be applied to develop temperature sensitive switch.

Sustained release of hydrophilic drug from polyphosphazenes/poly(methyl methacrylate) based microspheres and their degradation study

Drug delivery system is referred as an approach to deliver the therapeutic agents to the target site safely in order to achieve the maximum therapeutic effects. In this perspective, synthesis of three new polyphosphazenes and their blend fabrication system with poly(methyl methacrylate) is described and characterized with (1)H NMR, (31)P NMR, GPC and DSC. Furthermore, these novel blends were used to fabricate microspheres and evaluated for sustain release of hydrophilic drug (aspirin as model drug). Microspheres of the two blends showed excellent encapsulation efficacy (about 93%), controlled burst release (2.3% to 7.93%) and exhibited sustain in vitro drug release (13.44% to 32.77%) up to 218 h. At physiological conditions, the surface degradation of microspheres and diffusion process controlled the drug release sustainability. Furthermore, it was found that the degree of porosity was increased with degradation and the resulting porous network was responsible for water retention inside the microspheres. The percentage water retention was found to be interrelated with degradation time and percentage drug release.

Synthesis of reductive responsive polyphosphazenes and their fabrication of nanocarriers for drug delivery application

ABSTRACT Reductive responsive nanovehicles have the ability to deliver the anticancer drugs to intracellular compartments. The purpose of this study was to develop reductive sensitive nanocarriers based on polyphosphazenes. Amphiphilic polyphosphazenes with hydrophilic reductive sensitive side group and different molecular weights were synthesized and characterized. The synthesized copolymers show solvent dependent self-aggregation and form spherical micelles by using THF as co-organic solvent in dialysis method with critical micelle concentration value ranging from 5.73 µg/mL to 11.24 µg/mL. Micelles can encapsulate the hydrophobic drugs such as camptothecin (CPT) and indomethacin. In in vitro release experiments, CPT-loaded micelles release 70–80% of the loaded CPT in the presence of reducing agent dithiothreitol within 15 h. The results indicate that these reductive sensitive amphiphilic polyphosphazenes may find an application as anticancer drug carriers for safe drug delivery. GRAPHICAL ABSTRACT

Synthesis of Soluble Ferrocene-Based Polythiophenes and Their Properties

Ferrocene-based polythiophenes are the promising class of the functional materials, but mostly the polythiophenes are insoluble in common solvents except some derivatives of polythiophenes like poly(3-hexylthiophene) (P3HT). Herein, two new ferrocene-based thiophene monomers, 2-(thiophen-3-yl) ethyl ferrocenoate and 2-(thiophen-3-yl) methyl ferrocenoate were synthesized and copolymerized with 3-hexylthiophene (3HT) respectively. The resulting polymers were soluble (in common organic solvents) and processable. The synthesis and the molecular weights were confirmed by the 1H-NMR and GPC studies respectively. Poly (TEF-co-3HT) was subjected to study the electrochemical properties in comparison of respective monomers and ferrocene. It was found that the resulting copolymer had the combined redox properties of its monomers. Also, very interestingly, the copolymer showed improved reversible redox properties which were not only better than its parent monomers but even better than the pure ferrocene. Photoemission spectra of P3HT and Poly (TEF-co-3HT) were also rerecorded and compared with each other.Graphical Abstract