Small-reactor-based polymerase chain reaction (PCR) has attracted considerable attention. A significant number of tiny reactors must be prepared in parallel to capture, amplify, and accurately quantify few target genes in clinically relevant large volume, which, however, requires sophisticated microfabrication and longer sample-to-answer time. Here, single plasmonic cavity membrane is reported that not only enriches and captures few nucleic acids by taking advantage of both capillarity and hydrodynamic trapping but also quickly amplifies them for sensitive plasmonic detection. The plasmonic cavity membrane with few nanoliters in a void volume is fabricated by self-assembling gold nanorods with SiO₂ tips. Simulations reveal that hydrodynamic stagnation between the SiO₂ tips is mainly responsible for the trapping of the nucleic acid in the membrane. Finally, it is shown that the plasmonic cavity membrane is capable of enriching severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) genes up to 20 000-fold within 1 min, amplifying within 3 min, and detecting the trace genes as low as a single copy µL^-1. It is anticipated that this work not only expands the utility of PCR but also provides an innovative way of the enrichment and detection of trace biomolecules in a variety of point-of-care testing applications.

Ruthenium (Ru) is the most widely used metal as an electrocatalyst for nitrogen (N₂ ) reduction reaction (NRR) because of the relatively high N₂ adsorption strength for successive reaction. Recently, it has been well reported that the homogeneous Ru-based metal alloys such as RuRh, RuPt, and RuCo significantly enhance the selectivity and formation rate of ammonia (NH₃ ). However, the metal combinations for NRR have been limited to several miscible combinations of metals with Ru, although various immiscible combinations have immense potential to show high NRR performance. In this study, an immiscible combination of Ru and copper (Cu) is first utilized, and homogeneous alloy nanoparticles (RuCu NPs) are fabricated by the carbothermal shock method. The RuCu homogeneous NP alloys on cellulose/carbon nanotube sponge exhibit the highest selectivity and NH₃ formation rate of ≈31% and -73 μmol h^-1 cm^-2 , respectively. These are the highest values of the selectivity and NH₃ formation rates among existing Ru-based alloy metal combinations.