Preparation, Characterization Of Multi-Functional Nano-composites Based On Prussian Blue And Their Application In Electrochemical Sensors

Prussian blue (PB) or ferric hexacyanoferrate is one of the most ancient coordination materials known. Its exploration was in the beginning of the eighteenth century. However,a quite recent investigation by Neff,that PB forms electroactive layer when deposited onto the electrode surface has opened a new area in a fundamental investigation of this unique inorganic material. PB has been extensively explored as an electron transfer mediator for the construction of first-generation oxidase based electrochemical biosensor due to its excellent electrochemical behavior and good catalytic property. Although, enzymes have been widely employed in the fabrication of H2O2 sensors but their operational potential of redox reaction of H2O2 is relatively high which could oxidize electrochemically active species in the biological samples, thus leads to produce interfering current. Therefore, using PB based sensors which could operate at low potential in the H2O2 reduction could over com this problem. However, instability of PB film in neutral and alkali solutions greatly affects the development of PB based sensors/biosensors, because the optimum operational pH for oxidase enzymes which produce H2O2 is between 6.0 to 7.4. Many approaches have been reported to overcome this problem, including reducing the pH of the buffer solutions,synthesizing PB based nanocomposite, wrapping PB around the organic substances or electrodepositing it with other materials to obtain composites.In this study, we proposed some strategies for preparation,characterization and application of Prussian blue based multifunctional nano composite materials in the electrochemical sensors/biosensors.The first part is about one-pot hydrothermal synthesis of magnetite Prussian blue nano-composites and their application to fabricate glucose biosensor. In this work, we synthesized magnetite PB nano-composites in one pot hydrothermal procedure. Subsequently, we introduced the magnetite PB nano-composites to fabricate electrochemical glucose biosensor via immobilization of GOD-BSA by cross-linking with glutaraldehyde vapor on Fe3O4-PB modified glassy carbon electrode (GCE) surface. The combination of Fe3O4-PB nanocomposite and enzyme significantly enhanced the performance such as pH stability and sensitivity in enzyme biosensor.The second part is about the improved core-shell shape of Fe3O4@PB and their applications in electrochemical system through simple low cost pencil drown on paper as working electrode. In this work, well defined Fe3O4@PB core-shell magnetic nanoparticles were prepared by controlling the reactants ratios and by well purification of both Fe3O4 and Fe3O4@PB nanoparticles. Then, we fabricated a novel pencil drown on paper electrode as a working electrode to catalyze H2O2 via modification of as prepared electrode by synthesized Fe3O4@PB core-shell nanoparticles. Meanwhile, electrochemical performances of the fabricated pencil electrode and catalytic activities of Fe3O4@PB were investigated. Moreover,the fabricated electrode was compared with GCE using CV and amperometric current time to detect H2O2. Such graphite pencil drawn paper-based electrode is inexpensive, flexible,portable, disposable, and less pollution to the environment, and is suitable for practical use under resource-limited conditions. Hence, we think that this approach can be extended to generate other functional paper-based devices. We can conclude that the core-shell structured materials can greatly improve the operational stability of the PB based electrodes.The third part is about preparation and characterization of Prussian blue-Nickel complex enhanced catalytic activity towards amperometric detection of hydrogen peroxide.Here we reporting a simple method for preparation of Prussian blue nickel complex via physical method towards enhancement of its catalytic activity compared to conventional Prussian blue. As reported in the literature, nickel hexacyanoferrate possess relatively high catalytic activity in H2O2 reduction-oxidation compared to cobalt and copper hexacyanoferrates, therefore combination of Prussian blue which possessed the highest catalytic activity to H2O2 with nickel ions would result in a complex with high electrochemical properties than conventional Prussian blue. The modified PB-Ni electrode shows more better catalytic activity than PB modified electrode. The modified electrode is characterized as simplicity, low cost, high sensitivity and low detection limit. The effect of heat treatment on modified electrode properties is significant in terms of conductivity and catalyst activity improvement.The fourth part is about electrochemical synthesis of Prussian blue composite with carbon nanotubes and gold nanoparticles: study the effect of different preparation strategies in the film stably and conductivity. In this work, PB based composites with CNTs and Au nanoparticles were electrochemically synthesized by three ways of electrodeposition on glassy carbon electrode (GCE) surface to investigate the operational stability and conductive proprieties of the composites. Firstly, functionalized CNTs were dispersed in double distilled water then 10 μl of CNTs solution was dropped onto the GCE surface to obtain CNT/GCE(four electrodes were prepared by the same way denoted as CNT/GCE-1, CNT/GCE-2,CNT/GCE-3 and CNT/GCE-4). In the first electrode, PB was deposited by cycling the electrode 30 cycles on CNT/GCE surface from a solution contains K3Fe(CN)6, FeCl3, KCI and HCl, obtained PB-CNT/GCE-1. In the second electrode, PB and Au were electrodeposited onto CNT/GCE-2 surface by sequential deposition of PB from its precursors in acidic solution (30cycles), followed by deposition of Au from a solution of HAuCl4, KCl and HCl (20 cycles), obtained Au-PB-CNT/GCE-2. In the third electrode (CNT/GCE-3), PB-Au composite was deposited using one pot composite electrodeposition method by cycling the electrode 30 cycles in a solution containing K3Fe(CN)6, FeCl3,HAuCl4, KCl and HCl. In the fours electrode (CNT/GCE-4), PB and Au were deposited by repeatable layer by layer of PB (5 cycles) from its precursors followed by deposition of Au (5 cycles) from its precursors,obtained Au-PB layer. This step was repeated three times to obtain three layers of au-PB, the electrode was denoted as ((Au-PB)3-CNT/GCE). Layer by layer electrodeposition of PB and Au layer for three layers (PB-Au)3, highly could improve the pH stability and conductivity of the modified electrode. The method could greatly enhance the electrochemical applications of PB based films even at neutral and lower alkaline solutions.The fifth part is about electrodeposition of PB on Pencil drawn microelectrode on paper(PB/PDP) and its application in two-electrode electrochemical sensors. This work described a simple approach for fabricating inexpensive disposable microelectrode based on graphite pencil drown on paper as a working electrode combined with silver adhesive painted as reference electrode in two electrode system. PB Thin film was electrochemically deposited onto the microelectrode surface then its electrocatalytic activity toward H2O2 detection wastested. The microelectrode showed promising properties for electrochemical detection of H2O2. The PB/PDP microelectrode could be easily transferred as micro-biosensor for glucose detection or other biological spices.