Tuning gold nanostar morphology for the SERS detection of uranyl

Abstract

The impact of tunable morphologies and plasmonic properties of gold nanostars is evaluated for the surface‐enhanced Raman scattering (SERS) detection of uranyl. To do so, gold nanostars are synthesized with varying concentrations of the Good's buffer reagent, 2‐[4‐(2‐hydroxyethyl)‐1‐piperazinyl]propanesulfonic acid (EPPS). EPPS plays three roles including as a reducing agent for nanostar nucleation and growth, as a nanostar‐stabilizing agent for solution phase stability, and as a coordinating ligand for the capture of uranyl. The resulting nanostructures exhibit localized surface plasmon resonance (LSPR) spectra that contain two visible and one near‐infrared plasmonic modes. All three optical features arise from synergistic coupling between the nanostar core and branches. The tunability of these optical resonances is correlated with nanostar morphology through careful transmission electron microscopy (TEM) analysis. As the EPPS concentration used during synthesis increases, both the length and aspect ratio of the branches increase. This causes the two lower energy extinction features to grow in magnitude and become ideal for the SERS detection of uranyl. Finally, uranyl binds to the gold nanostar surface directly and via sulfonate coordination. Changes in the uranyl signal are directly correlated to the plasmonic properties associated with the nanostar branches. Overall, this work highlights the synergistic importance of nanostar morphology and plasmonic properties for the SERS detection of small molecules.

An excitation wavelength-optimized, stable SERS biosensing nanoplatform for analyzing adenoviral and AstraZeneca COVID-19 vaccination efficacy status using tear samples of vaccinated individuals

“…S6 ). Electromagnetic field (EMF) enhancement of anisotropic nanoparticles was localized near the tip and rod ends by finite element analysis (FEA) models (D. S. Indrasekara et al, 2015 ; Harder et al, 2021 ). Plasmon coupling of FEA models for three nanoplatforms was investigated based on three laser sources ( Fig.…”

Bespoke nanostars: synthetic strategies, tactics, and uses of tailored branched gold nanoparticles

“…In a seedless, one-step reaction AuNS were synthesized by the Good's buffer 4-(2-Hydroxyethyl)-1-piperazinepropanesulfonic acid (EPPS). 156 By increasing the concentration of EPPS constant pH of 7.4 in the presence of a constant HAuCl 4 concentration the resulting morphologies transformed from quasipherical to short thorned particles to elongated-branched AuNS, Fig 12 . EPPS, like many Good's buffers used in the synthesis of anisotropic nanosystems acts as both a reducing agent and shape-directing surfactant primarily through interactions between its piperazine ring and the gold nanocrystals. 157 As these interactions increase between the ligand and the higher energy facets as EPPS concentration rises, the selective deposition of gold is more strictly directed towards lower energy facets resulting in the (111) directional branches.…”

“…The increased presence of a dual reducing and shape-directing agent in EPPS promotes the elongated branching structure by increasing the reduction rate of Au(III) while simultaneously allowing for additional ammine-Au shape-directing interactions. Reprinted with permission from ref 156…”

Preface to the special issue dedicated to Professor Richard P. Van Duyne (1945–2019)

“…Similar effects may be exploited in the future for detection of trace molecules using Au nanostars. [ 24 ]…”

“…Similar effects may be exploited in the future for detection of trace molecules using Au nanostars. [24] Choo et al develop a novel SERS-active MOF-gold nanoparticle (AuNP) substrate for SERS and provide a rapid and sensitive method for the determination of the total iron binding capacity of transferrin (Tf) in human serum for diagnosing iron deficiency. By monitoring variations in the intensity of Raman signals for the MOF-AuNP complexes with the Tf concentration, Tf is quantitatively estimated and the limit of detection is determined to be 0.51 μM in spiked human serum.…”