Solvent Effect to the Uniformity of Surfactant-Free Salmon-DNA Thin Films.

Jake Richter,Heungman Park,Moses Nnaji

doi:10.3390/polym13101606

Abstract

Fabrication of surfactant-modified DNA thin films with high uniformity, specifically DNA–CTMA, has been well considered via drop-casting and spin-coating techniques. However, the fabrication of thin films with pure DNA has not been sufficiently studied. We characterize the uniformity of thin films from aqueous salmon DNA solutions mixed with ethanol, methanol, isopropanol, and acetone. Measurements of thickness and macroscopic uniformity are made via a focused-beam ellipsometer. We discuss important parameters for optimum uniformity and note what the effects of solvent modifications are. We find that methanol- and ethanol-added solutions provide optimal fabrication methods, which more consistently produce high degrees of uniformity with film thickness ranging from 20 to 200 nm adjusted by DNA concentration and the physical parameters of spin-coating methods.

Highlights

Deoxyribonucleic acid (DNA) has always been an interest in the biological sciences but has recently become an interest to researchers in materials science, physics, and chemistry for applications as a biodegradable component in optical and electronic devices [1,2,3,4,5,6]
DNA films can be used as a matrix and doped with functional materials that can alter the optical and electronic properties of the thin film, which may be useful for different types of organic devices [18,19,20]
Previous research has focused on thin films fabricated from surfactant modifications, primarily with cetyltrimethylammonium (CTMA) modified DNA thin films with consistent results [13,15,16,17,21,22,23,24,25]

Summary

Introduction

Deoxyribonucleic acid (DNA) has always been an interest in the biological sciences but has recently become an interest to researchers in materials science, physics, and chemistry for applications as a biodegradable component in optical and electronic devices [1,2,3,4,5,6]. Research has focused on controlling the electronic and optical properties of surfactant-modified thin films, and applications have relied on characterizing results from DNA–CTMA complexes. Research on surfactant-free thin DNA films has focused on how to affect the physical properties of the films, such as optical dispersion and refractive indices [19,25,27,28,29,30] and not on improving the efficiency of thin-film fabrication or standardizing the production of films with tunable thickness within a controlled range of uniformity. We present a systematic analysis of spin-coating procedures to fabricate DNA thin films from solvent added aqueous solutions with tunable thickness and desired macroscopic uniformity (millimeters to centimeters). We present analysis on quantifying uniformity and it is assumed that a reasonable interpolation of the data between concentration and solvent choice can be made upon data analysis

Aqueous DNA Solution Preparation with Solvents

Thin-Film Fabrication by Spin Coating

Results