Fluorescence-based techniques are the cornerstone of modern biomedical optics with applications ranging from bioimaging at various scales (organelle to organism) to detection and quantification of a wide variety of biological species of interest. However, feeble fluorescence signal remains a persistent challenge in meeting the ever-increasing demand to image, detect and quantify biological species of low abundance. Disclosed herein are simple and universal methods based on a flexible and conformal elastomeric film adsorbed with plasmonic nanostructures, referred to as “plasmonic skin” or “plasmonic patch”, that provide large and uniform enhancement of fluorescence on a variety of surfaces, through an “add-on-top” process. The novel fluorescence enhancement approach presented here represents a disease-, biomarker-, and application-agnostic ubiquitously-applicable fundamental and enabling technology to improve the sensitivity of existing analytical methodologies in an easy-to-handle and cost-effective manner, without changing and/or minimally altering the original procedures of the existing techniques.