Metal nanoparticles decorated on 2-D and 3-D phospholipid templates for biochemical analytic detection and energy conversion

Abstract

Among the global industrial markets in the future, the bio-medical market is one of the most promising industries to develop, and among them, bio-phenomenon measuring devices and implantable medical devices for human body are attracting global attention. Phospholipid molecules, one of the various biomolecules, consist of a head group with hydrophilicity and a tail group with hydrophobicity. Phospholipid molecules with these amphiphilic properties can form various structures such as vesicles, micelles, monolayer, bilayers, and multilayers depending on the concentration or physical conditions of the solvent. In addition, phospholipids are the fundamental components that make up the bio-membrane and can be used as catalyst support materials with high biocompatibility and applied to various applications. In this study, 2-D and 3-D structures were synthesized using a biocompatible material, lipid molecule, and biosensors and biofuel cells were developed using the size and distribution of metal nanoparticles coated on the surface as catalysts and their structure and properties were characterized by atomic force microscopy (AFM), transmission electron microscopy (TEM), scanning electron microscopy (SEM), cyclic voltammetry (CV), amperometry, and polarization curve, and applicability to nano and bio technologies was confirmed. First, the 2-D structure of the DiynePC monolayer can be applied as a catalyst support for electrochemical sensor electrodes using novel metal nanoparticles as catalysts. The surface of the DiynePC monolayer formed by the Langmuir-Blodgett method was irradiated with ultraviolet rays to cause polymerization to increase the durability of the monolayer, and Au nanoparticles were deposited using a thermal evaporation process to manufacture an electrode. The AuNP-modified lipid sensor showed a strong catalytic reaction to the electrochemical reduction reaction of hydrogen peroxide (H2O2), and the DiynePC monolayer also showed excellent catalytic support material. Since the deposition of Au nanoparticles was carried out by thermal evaporation, various types of metal nanoparticle sensors can be manufactured by depositing metals with relatively low melting points (e.g., Ag or Bi). Therefore, the DiynePC monolayer showed a catalyst support with excellent biocompatibility applicable to biomolecular sensors using various metal nanoparticle catalysts. Second, the DiynePC monolayer can serve as an effective catalyst support for glucose oxidation electrodes. Phospholipid electrodes deposited with Au nanoparticles can act as a substitute for Pt or Pt alloy catalyst electrodes that are expensive to materials and prone to poisoning intermediates caused by glucose oxidation reactions. The membrane-less fuel cell manufactured with a AuNP-modified lipid anode and an activated carbon cathode showed a power density of 1.39 mW cm-2 and developed a thin film fuel cell anode that can be bent using a flexible substrate. Lastly, the 3-D structure, lipid nanotubes (LNTs), can serve as a catalyst support for glucose fuel cell electrodes. LNTs formed using the DiynePC solubility gap between water and ethanol can be used as an effective electrode catalyst support because they are easy to control the length and thickness of the tube, maintain structural stability even in acidic and basic solutions, and have high biocompatibility. In addition, the distribution of metal nanoparticle catalysts was expanded from a two-dimensional planar structure to three-dimensional, increasing the surface area per unit area of the electrode to increase the power density of the fuel cell. The H2PdCl4 solution was reduced to the surface of the LNTs and Pd nanoparticles were coated on the surface of the LNTs to prepare a glucose oxidation electrode. PdNT-LNTs electrode fuel cells coated on the surface of phospholipid nanotubes showed a power density of up to 1.9 mW cm-2 and the highest value among membrane-less glucose fuel cells using Pd catalysts. Moreover, the manufactured glucose fuel cell showed high power density by connecting small kits manufactured by a 3D printer in series. As mentioned above, various structures using phospholipids (e.g., monolayer films, nanotubes, etc.) have high biocompatibility, so they can be applied to various biomedical materials and biofunctional devices as well as fuel cells and sensor electrodes in the future.