Electroless Deposition of Pd Nanostructures for Multifunctional Applications as Surface-Enhanced Raman Scattering Substrates and Electrochemical Nonenzymatic Sensors

Herein, we report a method to produce surface-enhanced Raman scattering (SERS)-active and excellent nonenzymatic glucose and an ascorbic acid (AA)-sensing substrate by an electroless deposition technique. Palladium (Pd) nanoparticles were deposited on different semiconductor [silicon (Si) and germanium (Ge)] and patterned (pyramidal Si) surfaces without any use of a surfactant. The growth rate and final morphology of the Pd nanostructures are observed to be dependent heavily on the surface energy of the substrate and number of defects present on the substrate surface. The highest SERS enhancement is observed for Pd nanoparticles deposited on a pyramidal Si substrate. Finite-difference time-domain simulation substantiates the experimental observation by showing that the sharp tip and gap between the shafts are the main factors contributing to the large enhancement of the incident electric field. Our result shows a superior SERS enhancement compared to the previously reported literature using pure Pd nanoparticles and also Pd nanoparticles deposited on different substrates. The substrates showed very good sensing properties for glucose and AA detection. The highest sensitivity (18.67 μA mM^-1 cm^-2) for AA is observed for Pd deposited on a Ge substrate for 60 min in the linear range of 20-40 mM, and for glucose, the highest sensitivity (2.658 μA mM^-1 cm^-2) is also observed for the same substrate in the linear range of 1-40 mM. The lowest detection limits for AA and glucose are 2.19 and 7.19 μM, respectively, for the same substrate. Substrates that we prepared are very useful for multifunctional applications like SERS and electrochemical nonenzymatic sensing.