Highly durable piezoelectric nanogenerators (PENGs) with high conversion efficiency and high power density are of great interest. Here, a foldable, scalable, durable, cost‐effective, sensitive, and high current output PENG developed by the direct integration of van der Waals heteroepitaxial growth of GaN nanowires (NWs) by metal‐organic chemical vapor deposition using a graphene coating on a Cu‐foil is reported where the direct growth of GaN on the metallic substrate plays a key role in achieving the high stability of the PENG. The PENG provides a durable and highly sensitive output compared to the previously reported GaN NW‐based PENGs fabricated by transferring NWs onto a foreign substrate. The reported PENG can harvest energy from a variety of ambient actuation sources such as bending, vibrations, air flow, finger pressing, foot striking, fluid flow, and normal force by weights, with the maximum piezoelectric output voltage and current density recorded as 19.7 V and 1.9 mA cm−2, respectively. Due to its high conversion efficiency, the PENG can power several LEDs and thus can be used to power electronic devices. More importantly, the PENG retains its performance after more than 4 million actuation cycles, demonstrating the potential of the design for practical applications using biomechanical and ambient actuation sources for self‐powered systems.

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Surface enhanced Raman scattering (SERS) is an excellent technique for detecting the trace concentration of targets. However, SERS based detection of fluorescent targets is tricky as the fluorescence signal can severely interfere with the SERS signal upon resonance excitation. This can limit the trace detection capability of SERS. Herein, the authors demonstrate that Au nanostars (NSs) are excellent for fluorescence quenching and trace detection by SERS. The NS based SERS substrate was used to measure the R6G concentrations as low as 10 pM upon laser excitation that are in resonance with the fluorescence absorption. The authors used a simple seed-mediated and surfactant assisted method to synthesize AuNSs in a wide size range. The size of the NSs can be tuned from 55 nm to about 1 μm simply by varying the seed to HAuCl4 ratio in the growth solution.

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