Implications of sample aging on the formation of internally etched silica coated gold nanoparticles

Volkert, Anna A.; Pierre, Marie Carmelle S.; Shrestha, Binaya Kumar; Haes, Amanda J.

doi:10.1039/c4ra15443f

Cited by 10 publications

(19 citation statements)

References 43 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…An intermediate case is observed for GNR-Si23, with approximately half of them well-isolated and the other half showing some degree of degradation. Interestingly, it has been reported that silica shell etching is not homogeneous, occurring preferentially in the inner layers of silica, while outer layers are more resistant to etching. , This selective etching was also observed in GNR-Si23 and GNR-Si35 (Supporting Information, Figure S3), and it would explain why, even if silica shells are partially degraded, they do not lose their capacity to confer steric hindrance to GNRs.…”

Section: Resultsmentioning

confidence: 67%

Preventing Plasmon Coupling between Gold Nanorods Improves the Sensitivity of Photoacoustic Detection of Labeled Stem Cells in Vivo

et al. 2016

View full text Add to dashboard Cite

Gold nanorods are excellent contrast agents for imaging technologies which rely on near-infrared absorption such as photoacoustic imaging. For cell tracking applications, the cells of interest are labeled with the contrast agent prior to injection. However, after uptake into cells by endocytosis, the confinement and high concentration in endosomes leads to plasmon band broadening and reduced absorbance. This would limit the potential of multispectral optoacoustic tomography in terms of spectral processing and, consequently, sensitivity. Here, we show that steric hindrance provided by silica coating of the nanorods leads to the preservation of their spectral properties and improved photoacoustic sensitivity. This strategy allowed the detection and monitoring of as few as 2 × 10(4) mesenchymal stem cells in mice over a period of 15 days with a high spatial resolution. Importantly, the silica-coated nanorods did not affect the viability or differentiation potential of the transplanted mesenchymal stem cells.

show abstract

Section: Resultsmentioning

confidence: 67%

Preventing Plasmon Coupling between Gold Nanorods Improves the Sensitivity of Photoacoustic Detection of Labeled Stem Cells in Vivo

et al. 2016

View full text Add to dashboard Cite

show abstract

“…The 1/e decay length is approximated as ~4 nm, which is reasonable assuming each branch can be treated as a nanorod [34]. The effective refractive index of the SAM can be estimated from where these lines cross [50]. As a result, the effective refractive index of the SAM is 1.43 7 .…”

Section: Resultsmentioning

confidence: 99%

How to accurately predict solution-phase gold nanostar stability

Phan

Haes

2018

Anal Bioanal Chem

Self Cite

View full text Add to dashboard Cite

Unwanted nanoparticle aggregation and/or agglomeration may occur when anisotropic nanoparticles are dispersed in various solvents and matrices. While extended Derjaguin-Landau-Verwey-Overbeek (DLVO) theory has been successfully applied to predict nanoparticle stability in solution, this model fails to accurately predict the physical stability of anisotropic nanostructures; thus limiting its applicability in practice. Herein, DLVO theory was used to accurately predict gold nanostar stability in solution by investigating how the choice of the nanostar dimension considered in calculations influences the calculated attractive and repulsive interactions between nanostructures. The use of the average radius of curvature of the nanostar tips instead of the average radius as the nanostar dimension of interest increases the accuracy with which experimentally observed nanoparticle behavior can be modeled theoretically. This prediction was validated by measuring time-dependent localized surface plasmon resonance (LSPR) spectra of gold nanostars suspended in solutions with different ionic strengths. Minimum energy barriers calculated from collision theory as a function of nanoparticle concentration were utilized to make kinetic predictions. All in all, these studies suggest that choosing the appropriate gold nanostar dimension is crucial to fully understanding and accurately predicting the stability of anisotropic nanostructures such as gold nanostars; i.e., whether the nanostructures remain stable and can be used reproducibly, or whether they aggregate and exhibit inconsistent results. Thus, the present work provides a deeper understanding of internanoparticle interactions in solution and is expected to lead to more consistent and efficient analytical and bioanalytical applications of these important materials in the future. Graphical abstract ᅟ.

show abstract

“…The characteristic electromagnetic field decay length ( l d ) for Ag@Au nanoparticles was determined using LSPR and the following model: where Δλ max is the LSPR wavelength shift, m 1 is the linear refractive index sensitivity, m 2 is a nonlinear refractive index sensitivity term that accounts for nonlinearity in the local electric field, n silica and n water are the effective refractive indices of silica and the bulk solution, respectively, and t is the silica membrane thickness. To determine these values, Ag@Au and Ag@Au@SiO 2 nanoparticles were incubated in 0–60% (w/v) sucrose solutions, and LSPR spectra were collected.…”

Section: Methodsmentioning

confidence: 99%

Impacts of pH and Intermolecular Interactions on Surface-Enhanced Raman Scattering Chemical Enhancements

Phan

Haes

2018

J. Phys. Chem. C

Self Cite

View full text Add to dashboard Cite

Surface-enhanced Raman scattering (SERS) is a surface sensitive technique that reveals information regarding molecular adsorption driving forces at nanoparticles surfaces. While the plasmonic properties of SERS substrates provide the largest signal enhancements, chemical enhancement mechanisms are more sensitive to molecular adsorption and intermolecular interactions. Herein, gold coated silver nanoparticles that are stabilized inside microporous silica membranes are used for monitoring short-range chemical enhancement effects. First, the silica membrane provides plasmonic stability while also facilitating kinetic measurements so that impacts of molecular protonation, molecule–molecule interactions, molecule–silica interactions, and molecule–Au interactions can be identified. To do this, the vibrational frequencies of 4-mercaptobenzoic acid (4-MBA) are monitored as a function of time and pH. Applying Fick’s second law to time-dependent responses reveals that molecular flux decreases with increasing pH. SERS spectra suggest that the kinetics of this phenomenon depend on the protonation state of 4-MBA and, hence, the energy required for the molecules to pass through the negatively charged silica membrane. Namely, repulsive electrostatic interactions between deprotonated molecules (R-COO–) and the silica shell increase the energy required for transport, which subsequently decreases the flux of molecules through the silica shell and subsequent adsorption to the metal surface. As pH approaches neutral conditions, the fraction of deprotonated 4-MBA increases. These molecules, which have a higher electron density in the aromatic rings versus protonated ones, favor selective chemical enhancement of the asymmetric versus symmetric C–C stretching modes. In addition, increasing intermolecular interactions between adsorbed molecules promote electron delocalization from aromatic rings to the carboxylate groups of 4-MBA. This response causes the pK a of the carboxylate to gradually increase from 4.8 (in solution) to 7.7 (on nanoparticle surfaces). Consequently, SERS signals for this molecule can be understood with respect to molecular protonation state, flux, and intermolecular interactions using these electromagnetically stable plasmonic nanostructures.

show abstract

Implications of sample aging on the formation of internally etched silica coated gold nanoparticles

Abstract: Local refractive index sensitivity modelling using the plasmonic properties of gold nanospheres assists in the elucidation of the nanoparticle-rattle formation as a function of sample age and storage conditions.

Cited by 10 publications

References 43 publications

Preventing Plasmon Coupling between Gold Nanorods Improves the Sensitivity of Photoacoustic Detection of Labeled Stem Cells in Vivo

Preventing Plasmon Coupling between Gold Nanorods Improves the Sensitivity of Photoacoustic Detection of Labeled Stem Cells in Vivo

How to accurately predict solution-phase gold nanostar stability

Impacts of pH and Intermolecular Interactions on Surface-Enhanced Raman Scattering Chemical Enhancements

Contact Info

Product

Resources

About