Study of photoelectric and optical properties of new purple membrane-based composite materials and chips and the applications

• Main Authors: Kai-Ru Jheng, 鄭凱如
• Other Authors: Hsiu-Mei Chen
• Format: Others
• Language: zh-TW
• Published: 2018
• Online Access: http://ndltd.ncl.edu.tw/handle/7b7n9r

博士 === 國立臺灣科技大學 === 化學工程系 === 106 === Bacteriorhodopsin (BR) in purple membranes (PM) is a protein with photoelectric conversion property, and can be applied in various photoelectric devices. In this study, β-alanine amino acid, bio-recognition molecules and inorganic nanoparticles were each assembled with PM to form new composite materials or chips, followed by the studies of their photoelectric and optical properties as well as material analysis. First, a single crystal was prepared by mixing β-alanine and PM together and the resultant composite crystal was found to carry photoelectric and nonlinear-optical properties. Secondly, antibodies against Escherichia coli were immobilized on an ITO electrode layered by a uniformly oriented PM layer via avidin-biotin bioaffinity interaction, and then E. coli was captured and detected. The reduction of photocurrent generated by PM was observed due to cell attachment；therefore, the E. coli concentrations were quantified. The same detection principle was further applied to the detection of general gram-negative bacteria. Thirdly, gold nanoparticles (AuNPs) coated on the same unidirectionally immobilized PM layer on ITO also caused PM photocurrent reduction, with the reduction effect of 80 nm AuNPs more significant than that of 10 nm AuNPs. When coated with 1 μM 10 nm AuNPs, the transient photocurrent of the PM chip decreased slower and the chemical capacitance effect of PM increased, possibly due to the SPR effect by AuNPs. Finally, green quantum dots (QDs) were attached to unidirectional PM layer immobilized on ITO. When blue light excited the PM-QDs composite chip, a continuous photocurrent of 179.6±0.3 nA/cm2 was produced. The replacement of the ITO electrode with a gold one further increased the continuous photocurrent density was to 5.7 μA/cm2. The decay time constant of the M state of BR was decreased when QDs were present or attached to. Therefore, it was interpreted that green fluorescence emitted from QDs excited by a blue light drove BR into its photocycle；and meanwhile, the illuminating blue light accelerated the decay of the BR M state, driving BR to quickly return to its ground state. This caused an accumulation of protons on PM surface, resulting in the production of a continuous photocurrent. TEM analysis revealed the arrangement of QDs binding on PM patches and a 67 % efficiency of Förster resonance energy transfer (FRET) between QDs and PM was estimated. Moreover, the second-order nonlinear susceptibilities of the PM-ITO chip were estimated as χ33(2) = 1.9×10-9 esu andχ31(2) = 1×10-9 esu using the Maker fringes method, demonstrating a high uniformity of PM orientation on ITO. The χ33(2) and χ31(2) parameters of the PM-QDs composite chip could not be determined due to the interference of QDs. In conclusion, the revealed photoelectric and optical properties of PM-based composite materials and chips can be applied to the development of new biosensors and biological solar cells.