Galvanic replacement (GR) is a widely used method to obtain substrates with nanostructure morphologies. However, there are substantial challenges related to the uniformity of the deposited nanostructures, the preparation of large-area nanocomposites, and the alteration of the morphologies deposited on substrates. Graphene was introduced into the surface of the aluminum panels in this study prior to conducting the GR reaction to incorporate graphene advantages of extremely high electrical conductivity and electron mobility. The experimental results revealed that the morphological consistency and particle densities of gold nanoparticles deposited on panels with graphene were much higher than those deposited on panels without graphene. Moreover, gold nanoparticles were deposited on the surfaces with graphene prior to deposition on those without graphene. Ordered large-area gold/graphene/aluminum hybrid nanocomposites can be obtained with desired morphologies by altering the preparation conditions. Finally, the feasibility of using the as-prepared gold hybrid nanocomposites as surface-enhanced Raman scattering (SERS) substrates was examined. The results indicated that the Raman signal enhancement factors of the as prepared substrates were varied as the preparation condition changed due to the difference in the morphologies. Under the optimal condition, a high enhancement factor of approximately 3 × 108 with good reproducibility was found, which demonstrates the potential of utilizing the as-prepared gold hybrid nanocomposites in SERS and other sensing applications.

In this study, Volvariella volvacea (VV) mushroom was utilized as a green carbon precursor to synthesize carbon dots (CDs) and applied as a fluorescent (FL) sensor to detect Fe3+ and Pb2+ ions. The VV-CDs showed a high photostability and FL properties with a quantum yield of about 11.5%. The VV-CDs exhibited an excitation-dependent emission manner, with an optimum emission wavelength at 440 nm excited at 360 nm. The VV-CDs were evaluated and shown to be facile and effective FL sensors for detecting Pb2+ and Fe3+ ions based on the FL quenching efficiency, demonstrating the special complex chelate between the metal ions and effective surface functional groups of VV-CDs. VV-CDs displayed high responses to Fe3+ and Pb2+ ions, with the linear relationship of 1-100 μM and limits of detection (LODs) of 12 and 16 nM for Pb2+ and Fe3+ ions, respectively. Furthermore, the FL sensor was validated with real water samples, showing very good spike recoveries.