Exploration of the growth process of ultrathin silica shells on the surface of gold nanorods by the localized surface plasmon resonance

Abstract

Ultrathin silica coating (UTSC) has emerged as an effective way to improve the compatibility and stability of nanoparticles without attenuating their intrinsic optical properties. Exploration strategies to probe the growth process of ultrathin silica shells on the surface of nanoparticles would represent a valuable innovation that would benefit the development of ultrathin silica coated nanoparticles and their relevant applications. In this work, we report a unique, very effective and straightforward strategy for probing the growth of ultrathin silica shells on the surface of gold nanorods (Au NRs), which exploits the localized surface plasmon resonance (LSPR) as a reporting signal. The thickness of the ultrathin silica shells on the surface of Au NRs can be quantitatively measured and predicted in the range of 0.5-3.5 nm. It is demonstrated that the LSPR shift accurately reflects the real-time change in the thickness of the ultrathin silica shells on Au NRs during the growth process. By using the developed strategy, we further analyze the growth of UTSC on the surface of Au NRs via feeding of Na2SiO3 in a stepwise manner. The responsiveness analysis of LSPR also provides important insight into the shielding effect of UTSC on the surface of Au NRs that is not accessible with conventional strategies. This LSPR-based strategy permits exploration of the surface-mediated sol-gel reactions of silica from a new point of view.

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

“…Later on, Li et al reported on the formation of ultra-thin silica shell (UTSC) on MPTMS-capped AuNRs. The thickness of the silica shell was finely tuned in the 0.8–2.1 nm range by changing the amount of Na 2 SiO 3 [ 69 ]. These authors also investigated the rate of silica-shell growth using LSPR.…”

“… ( A ) CTAB replacement by (3-mercaptopropyl)trimethoxysilane (MPTMS) for the growth of thin layers of silica. ( B ) and ( C ) TEM images obtained for different aspect ratio (AR) from ref [ 67 ] ( B ) and ref [ 69 ] ( C ). ( D ) Kinetics of silica shell thickness for decreasing concentrations of Na 2 SiO 3 from ref [ 69 ].…”

Amplifying the signal of localized surface plasmon resonance sensing for the sensitive detection of Escherichia coli O157:H7

“…Moreover, Huang and co-workers considered that a 2–3 nm silica shell coated on Au NRs induces a highest sensitivity for plasmonic organic photovoltaic devices 30 . The recent theoretical calculation reveals that ultrathin silica coating (within 3.5 nm) would be ideal for improving the sensitivity 31 . Therefore, the aim of our present work is to explore the cut-off thickness in a small size, and further amplify the sensitivity of Au NRs maximally for practical application for detection of E. coli O157:H7.…”

Protection of silver and gold LSPR biosensors in corrosive NaCl environment by short alkanethiol molecules; characterized by extinction spectrum, helium ion microscopy and SERS

“…There have been reports that under some circumstance, a protective layer can enhance the gure of merit when coated with Au and SiO 2 . 65,76,77 Thus, we conclude that the 1-BT treatment not only succeeded in stabilizing the sensor but also lead to improvements in the gure of merit, 208.9 and 170.43 nm per RIU for the 17 and 22 nm thick AgLSPR sensors respectively. Fig.…”