Highly Uniform DNA Monolayers Generated by Freezing‐Directed Assembly on Gold Surfaces Enable Robust Electrochemical Sensing in Whole Blood

Assembling DNA on solid surfaces is fundamental to surface‐based DNA technology. However, precise control over DNA conformation and organization at solid–liquid interfaces remains a challenge, resulting in limited stability and sensitivity in biosensing applications. We herein communicate a simple and robust method for creating highly uniform DNA monolayers on gold surfaces by a freeze‐thawing process. Using Raman spectroscopy, fluorescent imaging, and square wave voltammetry, we demonstrate that thiolated DNA is concentrated and immobilized on gold surfaces with an upright conformation. Moreover, our results reveal that the freezing‐induced DNA surfaces are more uniform, leading to improved DNA stability and target recognition. Lastly, we demonstrate the successful detection of a model drug in undiluted whole blood while mitigating the effects of biofouling. Our work not only provides a simple approach to tailor the DNA‐gold surface for biosensors but also sheds light on the unique behavior of DNA oligonucleotides upon freezing on the liquid‐solid interface.