Cationic lipid binding control in DNA based biopolymer and its impacts on optical and thermo-optic properties of thin solid films

Biomaterials based on deoxyribonucleic acid (DNA) have shown notable potential in optoelectronic and photonic devices. In order to further investigate the optical properties of a DNA-based lipid complex such as DNA-cetyltrimethylammonium (CTMA), which is widely used in current DNA thin film research, a new refinement process was developed to minimize the relative bound water content and control binding of CTMA onto the DNA backbone. The water contents and CTMA binding in the DNA-CTMA precipitates were identified by spectrometric measurements to quantify effects of our refinement process. Dissolving these refined DNA-CTMAs in organic solvents, thin solid films were deposited on Si and quartz substrate using the spin coating process. Their refractive indices and absorbance were measured to quantitatively assess the impact of our refinement process on the optical properties of the DNA-CTMA films. In addition, thermo-optic coefficients, dn/dT, were also measured in a temperature range from 30 to 100°C to observe differences among refined DNA-CTMAs. Detailed quantitative spectroscopic analyses and optical measurements are reported.