Elucidation of photophysical changes and orientation of acridine orange dye on the surface of borate capped gold nanoparticles using multi-spectroscopic techniques

Abstract

In the present work, we have carried out a detailed investigation on the binding interaction of acridine orange (AO) with borate capped gold nanoparticles (Au NPs) by absorption spectroscopy, steady state emission spectroscopy, time resolved fluorescence spectroscopy, high resolution transmission electron microscopy (HR-TEM), dynamic light scattering (DLS), zeta potential measurements, Fourier transform infrared (FT-IR) and Raman spectroscopy. The phenomena of hypochromism and the appearance of coupled localized surface plasmon resonance (LSPR) bands in the absorption spectral studies of the AO-Au NP system suggested the vital role of electrostatic interactions between AO dye and Au NPs. The results from HR-TEM and DLS measurements confirmed the formation of aggregated clusters of nanoparticles. The zeta potential studies of Au NPs and AO coated Au NPs suggested the occurrence of partial surface charge neutralization of negatively charged Au NPs by cationic AO dye. The interparticle edge to edge separation distance of adjacent Au NPs revealed the presence of AO molecules between the nano-gaps of Au NPs. Emission spectral studies of AO in the presence of increasing concentrations of Au NPs indicated the existence of a static quenching mechanism. Time resolved fluorescence spectroscopic study further validated the findings of steady state emission measurements. The comparison of experimental emission quenching data with the theoretically calculated value suggested the probable multi-layered assembly of AO on the surface of Au NPs. FT-IR and Raman spectral studies further revealed the existence of electrostatic interactions and possible horizontal orientation of AO dye molecules on Au NP surfaces.

Carbon Quantum Dot-Anchored Bismuth Oxide Composites as Potential Electrode for Lithium-Ion Battery and Supercapacitor Applications

“…The negligible difference in the fluorescence lifetimes of the CQD and the CQD–Bi 2 O 3 composite clearly suggests the formation of nonfluorescent ground-state complex and involvement of static quenching mechanism . It is well known that the formation of a ground-state complex between the fluorophore and metal oxide materials cannot induce changes in the fluorescence lifetimes of the fluorophore . Thus, it is believed that the observed emission quenching in the case of the CQD–Bi 2 O 3 composite is primarily due to the static quenching mechanism.…”

“…32 It is well known that the formation of a ground-state complex between the fluorophore and metal oxide materials cannot induce changes in the fluorescence lifetimes of the fluorophore. 33 Thus, it is believed that the observed emission quenching in the case of the CQD–Bi 2 O 3 composite is primarily due to the static quenching mechanism. Moreover, this inference is consistent with the steady-state emission studies.…”

Optimization of Surface-Enhanced Raman Spectroscopy Conditions for Implementation into a Microfluidic Device for Drug Detection

“…This indicates that, for both AgNPs and AuNPs, the real part of the dielectric constant is negative, with minimal intraband losses, suggesting that the imaginary part of the dielectric constant is small. These are necessary conditions for plasmon resonance with high quality factor to occur in the visible portion of the electromagnetic spectrum. − For a multi-nanoparticle system, the location of the plasmon band is affected by several factors, including interparticle distance, surface species adsorbed, dielectric constant of the surrounding medium, onset of interband transitions, density of electrons, and effective electron mass. − The pre-LiCl extinction spectra for AgNPs and AuNPs are observed to broaden (with a shoulder appearing in the 80 nm AgNP) with the absorption maxima red shifting as the nanoparticle size increases. This observation can be attributed to retardation effects, excitation of the higher-order plasmon modes in the nanoparticle, and increasing the polydispersity in the nanoparticle solution. − …”

Comprehensive Multispectroscopic Analysis on the Interaction and Corona Formation of Human Serum Albumin with Gold/Silver Alloy Nanoparticles

“…The increase in hydrodynamic diameter of 7 nm signifies that a densely packed adsorption of HSA has occurred on the surface of Au/Ag NPs. The average particle size calculated from HR-TEM and DLS measurement showed appreciable difference, and this deviation is attributed to the fact that DLS gives a measure of hydrodynamic radii of nanoparticles in solution; however, HR-TEM provides the size of the nanoparticle in dried condition . Owing to its low resolution and lack of robustness relative to cumulants analysis, DLS measurements are often used with other characterization methods for qualitative comparison .…”