Effect of Seed Age on Gold Nanorod Formation: A Microfluidic, Real-Time Investigation

Abstract

We report a real time investigation into the effect of seed age on the growth of gold nanorods using a microfluidic reaction apparatus. Through small-angle X-ray scattering (SAXS) and ultraviolet–visible spectroscopy (UV–vis) analysis, we observe the seeds aging in accordance with Ostwald ripening. A seed solution is then aged in situ and continuously injected into a microfluidic chip to initiate rod growth. We track nanorod formation in real time using in-line ultraviolet–visible and near-infrared (UV–vis–NIR) monitoring and observe a dramatic decrease in yield with increasing seed age. We then demonstrate that, by diluting the gold seed solution immediately following synthesis, the rate of aging can be reduced and nanorods synthesized continuously, in good yield. These findings suggest ultrasmall, catalytically active seeds, which are rapidly lost due to ripening and are critical for the formation of gold nanorods.

Gold Nanorods for LSPR Biosensing: Synthesis, Coating by Silica, and Bioanalytical Applications

“…0.5 mg/min using a millifluidic set-up [ 62 ]. Synthesis of AuNRs using microfluidic reactors (either using a chip reactor [ 44 , 63 ] or micrometric tubings [ 58 ]) have also been reported. However, as mentioned by Lohse et al reaching gram-scale with a microfluidic reactor would require numbering up a large number of reactors [ 62 ].…”

Gold‐Speckled SPION@SiO2 Nanoparticles Decorated with Thiocarbohydrates for ASGPR1 Targeting: Towards HCC Dual Mode Imaging Potential Applications

“…The TEM image reported in Figure A clearly shows the formation of the small Au NPs with an average diameter of (2.1±0.3) nm, as obtained by statistical analysis (Figure S4 A, Supporting Information). The UV/Vis absorption spectrum of the Au seeds shows the presence of a slight shoulder at 508 nm, in a spectral range typically ascribable to the surface plasmon resonance (SPR) of small Au NPs (≥2 nm; Figure B) . Correspondingly, the SPR band is observed in the UV/Vis absorption spectrum of Au‐speckled SPION@SiO 2 NPs, thus proving the successful decoration of silica coated nanostructures with the small Au NPs (Figure S4 C, Supporting Information).…”

High-yield synthesis and fine-tuning aspect ratio of (200) faceted gold nanorods by the pH-adjusting method

“…The GNR growth is initiated by adding gold seeds into a growth solution containing Au 0 , Ag + , CTAB, and reducing agents. The GNR size, AR, and yield are sensitive to (i) the size and nature of the seeds (affected by the aging time and the standing time during and aer the synthesis), 31 (ii) the quantity of the Ag + and CTAB additives, 32 and (iii) the pH value of the growth solution. [33][34][35][36] [100] direction), which is supported by transmission electron microscopy (TEM) and X-ray diffraction (XRD).…”