Growth of gold nanorods in solution and on ITO and Au substrates using non-peripheral amine functionalized nickel(ii) phthalocyanine capped gold nanoparticles as a seed solution

Abstract

In this paper, we report the synthesis of gold nanorods (GNRs) both in solution and on ITO and Au substrates using non-peripheral amine functionalized nickel(II) phthalocyanine capped gold nanoparticles (4α-Ni^IITAPc-AuNPs) as a seed solution. The GNRs formed in solution show transverse and longitudinal waves at 526 and 761 nm, respectively. The high-resolution transmission electron microscopy (HR-TEM) studies show the presence of GNRs in addition to few spherical AuNPs. The average aspect ratio of GNRs was found to be 4.5 ± 0.3. Further, the GNRs were also grown on the Au and ITO substrates by seed mediated growth method using (3-mercaptopropyl)-trimethoxysilane sol–gel as a linker. The 4α-Ni^IITAPc-AuNPs were first self-assembled on ITO or Au surface modified with MPTS sol–gel film and then immersed in a GNR growth solution, to form surface grown GNRs. The growth of GNRs on the MPTS sol–gel film modified ITO surface was monitored by UV-vis spectroscopy. The 4α-Ni^IITAPc-AuNPs attached on ITO surface shows a surface plasmon resonance band at 550 nm. The intensity of this band increases and an additional shoulder band around 680 nm was observed while increasing the immersion time of the 4α-Ni^IITAPc-AuNPs modified ITO surface into the growth solution. After 24 h, the 4α-Ni^IITAPc-AuNPs modified ITO surface shows a broad wave around 680 nm along with a band at 550 nm. Similarly, Au modified electrode also showed characteristic transverse and longitudinal absorption bands for GNRs which confirm the successful growth of GNRs on Au surface. The surface grown GNRs were characterized by atomic force microscopy, ATR-FT-IR, cyclic voltammetry and impedance spectral studies. Finally, the electrocatalytic activity of GNRs grown Au electrode was examined by studying the oxidation of L-tyrosine.