Manipulation of the Geometry and Modulation of the Optical Response of Surfactant-Free Gold Nanostars: A Systematic Bottom-Up Synthesis

Abstract

Among plasmonic nanoparticles, surfactant-free branched gold nanoparticles have exhibited exceptional properties as a nanoplatform for a wide variety of applications ranging from surface-enhanced Raman scattering sensing and imaging applications to photothermal treatment and photoimmunotherapy for cancer treatments. The effectiveness and reliability of branched gold nanoparticles in biomedical applications strongly rely on the consistency and reproducibility of physical, chemical, optical, and therapeutic properties of nanoparticles, which are mainly governed by their morphological features. Herein, we present an optimized bottom-up synthesis that improves the reproducibility and homogeneity of the gold-branched nanoparticles with desired morphological features and optical properties. We identified that the order of reagent addition is crucial for improved homogeneity of the branched nature of nanoparticles that enable a high batch-to-batch reproducibility and reliability. In addition, a different combination of the synthesis parameters, in particular, additive halides and concentration ratios of reactive Au to Ag and Au to Au seeds, which yield branched nanoparticle of similar localized surface plasmon resonances but with distinguishable changes in the dimensions of the branches, was realized. Overall, our study introduces the design parameters for the purpose-tailored manufacturing of surfactant-free gold nanostars in a reliable manner.

A novel cell transfection platform based on laser optoporation mediated by Au nanostar layers

“…Instead, one has to use a statistical averaging over nanorod aspect ratio [53] or more sophisticated treatment that takes into account the nanorod length and width distributions, the surface scattering of conductive electrons, and fine deviations of the particle shape from an ideal nanorod cigar-like model [54]. In summary, the value σ a (800) = 1.0 × 10 −10 cm 2 can be considered a reasonable estimation for the absorption properties of typical AuNSs fabricated with 15-nm seeds by surfactant-less protocols [39,40,55]. This estimation is in good agreement with FEM simulations reported by Vo-Dinh group [39] for a close AuNS model (S20), σ a (800) = 1.14 × 10 −10 cm 2 .…”

Recent Advancement in the Surface-Enhanced Raman Spectroscopy-Based Biosensors for Infectious Disease Diagnosis

“…It will help eliminating non-specific biological interactions hence reducing SERS spectral interference and ensuring colloidal stability for stable SERS signal acquisition. An appreciable amount of effort is currently being invested by the research community to investigate these fundamental aspects of the nanoparticle-based SERS diagnostic assays [7,17,70,73,125,126]. Combining the current exponential improvement in both fundamental chemistry and device engineering, the widespread use of SERS-based diagnostics for infectious diseases at the POC and clinical setting is only a very few years away from us.…”

“…In SERS, this intense localized electromagnetic field of the plasmonic substrate is exploited to amplify the intrinsically weak Raman scattering cross-section of analytes when they are either on or in close proximity to a plasmonic substrate [14]. The LSPR and the magnitude of SERS enhancement can be modulated by changing the size, composition, shape, and the local environment of the NP [17][18][19][20][21][22][23][24][25]. In the context of SERS, plasmonic nanomaterial are referred to as SERS substrates and their effectiveness as a SERS substrate is evaluated by the SERS enhancement factor [26][27][28][29].…”

Anisotropic Gold Nanoparticles in Biomedical Applications

“…The procedure afforded multibranched AuNUs by adding AgNO 3 and ascorbic acid to a mixture of AuNP seeds and HAuCl 4 , but the nanoparticles obtained were not homogenous. Confirming the importance of a surfactant-free procedure, the protocol was very recently modified [ 50 ], pointing out the crucial steps which could be responsible for the polydispersion and poor reproducibility. First of all, the addition of silver nitrate was anticipated respect to ascorbic acid, ensuring a major homogeneity of the final sample.…”