Abstract
Numerous properties from metal nanostructures can be tuned by controlling both their size and shape. In particular, the latter is extremely important because the type of crystalline surface affects the surface electronic density. This paper describes a simple approach to the synthesis of highly-structured, anisotropic palladium nanostructured dendrites. They were obtained using an eco-friendly biomolecule 5-hydroxytryptophan, which acts as both a reducing and stabilizing agent. The growth mechanism is proposed for the evolution of dendrites morphology. It was found that the concentration of 5-hydroxytryptophan played a vital role on the morphology of the nanostructured Pd dendrites. This nanomaterial shows enhanced electrocatalytic performance towards the oxidation of formic acid, and it exhibits surface-enhanced Raman scattering properties towards the prostate specific antigen. These properties may be explored in fuel cells and biosensors, respectively.
Highlights
Both the occupation and the electrostatic repulsion from the modi ed prostate speci c antigen (PSA) Ab on Pd dendritic nanostructures (PdDNs) was the reason for the decreasing surface enhanced Raman scattering (SERS) signal of rhodamine 6G (R6G) molecule
The magnitude of SERS signal of only $26% was obtained for R6G upon modifying PSA Ab1 on the ower-like Pd dendrites nanoparticle surface (Fig. 7A, curve b) in comparison with PSA Ab1 free sample (Fig. 7A, curve a)
The electrostatic repulsion from PSA Ab1 may be smaller, when it binds with PSA protein, which will neutralize part of the positive charges on the PSA Ab1
Summary
Pd nanoparticles are an attractive material for a wide range of applications in catalysis, hydrogen storage and sensing, reduction of automobile pollutants and so forth.[21,22,23,24] Pd nanoparticles have been extensively considered as a better alternative material for polymer electrolyte membrane fuel cells towards the catalytic oxidation of formic acid as well as the oxygen reduction in a proton-exchange membrane (PEM) fuel cell.[25,26,27] Huge efforts have been dedicated to the preparation of Pd nanoparticles of various shapes, such as nanobars, nanorods, nanocubes, octahedra, icosahedra, nanowires and nanoplates.[28,29,30,31] Attempts have been made to develop anisotropic Pd based dendritic-like nanostructures using surfactants and polymers or high temperature reactions in organic media.[24,32,33,34,35,36,37] For instance, Tilley et al reported highly branched Pd nanostructures for the ultrafast catalysis reaction for the hydrogenation of nitrobenzene to aniline though it was prepared in a non-aqueous medium.[32]. We will demonstrate the morpho-dependent electrocatalytic activity of PdDNs towards the oxidation of formic acid and their application as a label for the prostate speci c antigen (PSA) SERS biosensor with the detection limit of 10 ng mLÀ1 for the rst time
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