Sensitive, Quantitative Naked‐Eye Biodetection with Polyhedral Cu Nanoshells

One of the most heavily used methods in chemical and biological labeling, detection, and imaging is based on silver shell‐based enhancement on Au nanoparticles (AuNPs) that is useful for amplifying Rayleigh scattering, colorimetric signal, surface‐enhanced Raman scattering, and electrical signal, but poor structural controllability and nonspecific growth of silver shells have limited its applications, especially with respect to signal reproducibility and quantification. Here, a highly specific, well‐defined Cu nanopolyhedral shell overgrowth chemistry is developed with the aid of polyethyleneimine (PEI) on AuNPs, and the use of this PEI‐mediated Cu polyhedral nanoshell (CuP) chemistry is shown as a means of light‐scattering signal enhancement for the development of naked‐eye‐based highly sensitive and quantitative detections of DNA and viruses. Remarkably, these CuPs are exclusively formed on AuNPs in a controllable manner, with no noticeable nonspecific CuP growth. The findings enable to acquire clearly visible signals without analytic instrumentation, detectable down to 8 × 10−15m of DNA (anthrax sequence) and 2700 copies of viruses (noroviruses in clinical stool samples) with broad dynamic ranges on archetypal assay platforms. This new method provides a general platform in controlling Cu shell nanostructures and their optical signals, and opens up revenues for highly reliable, quantitative onsite naked‐eye biodetection. A highly specific, but well‐defined, controllable Cu nanopolyhedral shell overgrowth chemistry is developed with the aid of polyethyleneimine (PEI) on Au nanoparticles (AuNPs), and the use of this PEI‐mediated Cu polyhedral nanoshell (CuP) approach is shown as a means of strong, reliable light‐scattering signal enhancement on AuNPs for naked‐eye‐based DNA and virus onsite sensing systems without a need for instrumentation.