The Synthesis Of Hemin-based Composites And Their Application In Electrichemistry

With the development of biotechnology, the application of biomimetic materials has reached a new height and the synthesis of biological composites has also been a widespread concern. As a typical representative of biomimetic materials’family, hemin is a porphyrin-based compound, which consists of four pyrrole ring through a ring of four alkyne group linked to the formation of methyl. Fe2+ is located in center of the ring. Fe2+ can form six coordination bonds and four of the bonds can form a pyrrole ring with the nitrogen atom. This structure grows up a natural coenzyme. Using this property of hemin, we introduce some other nanomaterials onto hemin matrix so that some biocomposite can be obtained with both biocompatibility and solubility, which will overcome some of the disadvantages of heme itself. The newly synthesized composites can be perfectly applied in glucose and plant hormone’s detection.In this study, three kinds of composites were synthesized based on hemin:zinc-doped hemin composite; hemin-reduced graphene oxide and hemin-boron nitride composites. They were studied to detect glucose and plant hormone indole acetic acid.1. The synthesis and characterization of zinc-doped hemin composite and its application in glucose detection.This part of work explores the electrochemical response of glucose oxidase (GOD) on the composite material. The study shows the new zinc-doped hemin composite has better stability and can provide a more favorable microenvironment for electron transfer between the protein and the electrode surface. The immobilized GOD maintained a good biological activity. The modified electrode showed a good affinity to glucose. The linear range of novel glucose biosensor for glucose detection was 5.0 μM to 0.5 mM with a detection limit of 0.5 μM (S/N=3) and the correlation coefficient R equals to 0.998. The results showed that zinc-doped hemin composite improved selectivity and sensitivity of GOD to glucose and the results of actual sample were also satisfactory.2. The synthesis and characterization of hemin-reduced graphene oxide composite and its application in IAA detection.A novel electrochemical amperometric sensor, intended for indole-3-acetic acid (IAA) detection at low potential, was established based hemin/reduced graphene oxide (Hemin/rGO) nanocomposite. The hemin/rGO nanocomposite was prepared by a facile one-pot hydrothermal method which combined the reduction and functionalizaiton of graphene oxide with hemin together without other reaction steps. IAA was oxidized aerobically by the newly synthesized nanocomposite. The consumption of oxygen has a linear relationship with the amount of IAA in the concentration range from 0.1 μM to 0.185 mM with a detection limit of 0.05μM (S/N=3) and the correlation coefficient R equals to 0.999. This work broadened the application of hemin/rGO in electrochemical sensor areas. Hence, the novel IAA sensor showed great potential in the determination of IAA in practical fruit and vegetable samples.3. The synthesis and characterization of hemin-boron nitride composite and its application in IAA detection.This work focused on the synthesis of hemin-boron nitride composite (Hemin/BN) and its application in plant hormone detection measured in electrochemical sensors. The newly prepared hemin/BN composite was modified on glassy carbon electrode.In a phosphate buffer solution system, current-time curve method was used by monitoring the current signal of IAA, based on the suppression catalytic current to indole acetic acid and oxygen. This realized the determination of IAA. The concentration of IAA measured was between 0.5μM to 0.08 mM and the correlation coefficient was 0.997 with the detection limit of 0.15 μM. The results brought about by the newly built sensor for measuring indole acetic acid in fruit and vegetable were satisfactory. Indicating this new electrochemical biosensor has a great potential in the detection of IAA.