Abstract
The use of gold nanorods (AuNRs) as surface-enhanced Raman scattering (SERS) substrates has gained much attraction due to their remarkably aspect-ratio-dependent plasmonic properties. In this report, we described the development of AuNRs with a high aspect ratio and longitudinal surface plasmon resonance (LSPR) >850 nm through a hydroquinone-based fabrication with minor modifications. The synthesis started with the reduction of chloroauric acid (HAuCl4) by sodium borohydride (NaBH4) to make gold nanoseeds from which AuNRs were grown with the aid of silver nitrate (AgNO3), HAuCl4, cetyltrimethylammonium bromide (CTAB), and hydroquinone (HQ). Scanning electron microscopy coupled with energy-dispersive X-ray (SEM-EDX), Transmission electron microscope (TEM), X-ray diffraction (XRD) and Ultra-violet-Visible spectroscopy (UV-Vis) were performed to study the shape, size, and structural and optical properties of AuNRs, respectively. The results showed that AuNRs with high aspect ratios (AR > 3) were single crystals with a heterogenous size distribution, and that the growth of Au nanoseeds into AuNRs took place along the [001] direction. AuNRs exhibited two plasmon resonance peaks at 520 nm and 903 nm, while gold nanoseeds had only a plasmon resonance peak at 521 nm. The as-synthesized AuNRs also showed SERS effects for thiophanate methyl, a broad-spectrum fungicide, with the limit of detection down to 5 mg/L of the fungicide. AuNR-coated glass can serve as a SERS-based sensing platform for rapid detection of thiophanate methyl with high sensitivity and reproducibility.
Highlights
Nanomaterials have drawn much attention due to their advanced physical and chemical properties over bulk materials, and variety of applications in the biomedical, environmental, industrial, and food agriculture industries [1]
Gold nanoparticles with nontoxicity and high bioactivity are the most stable metal nanoparticles, and they present a wide range of applications in modern medical and biological studies such as drug, deoxyribonucleic acid (DNA), and antigens delivery; biosensorics, genomics, immunoanalysis, and detection of microorganisms and cancer cells; and bioimaging [2,3]
Plasmon resonance properties of AuNRs and Au nanoseeds were studied through Ultra-violet-Visible spectroscopy (UV-Vis) spectroscopy
Summary
Nanomaterials have drawn much attention due to their advanced physical and chemical properties over bulk materials, and variety of applications in the biomedical, environmental, industrial, and food agriculture industries [1]. Gold nanoparticles with nontoxicity and high bioactivity are the most stable metal nanoparticles, and they present a wide range of applications in modern medical and biological studies such as drug, deoxyribonucleic acid (DNA), and antigens delivery; biosensorics, genomics, immunoanalysis, and detection of microorganisms and cancer cells; and bioimaging [2,3] The nanoparticles present their unique physical and chemical properties, optical surface plasmon resonance (SPR), which is related to collective excitations of conductive localized electrons on surface metals under visible and near infra-red (VIS-NIR) irradiation [4,5,6,7]. It has been argued that the shape, size, and structure of gold nanoparticles determine their chemical and physical properties [17,18]
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