Surface-enhanced Raman scattering: realization of localized surface plasmon resonance using unique substrates and methods

Abstract

Surface-enhanced Raman scattering (SERS) enhancement and the reproducibility of the SERS signal strongly reflect the quality and nature of the SERS substrates because of diverse localized surface plasmon resonance (LSPR) excitations excited at interstitials or sharp edges. LSPR excitations are the most important ingredients for achieving huge enhancements in the SERS process. In this report, we introduce several gold and silver nanoparticle-based SERS-active substrates developed solely by us and use these substrates to investigate the influence of LSPR excitations on SERS. SERS-active gold substrates were fabricated by immobilizing colloidal gold nanoparticles on glass slides without using any surfactants or electrolytes, whereas most of the SERS-active substrates that use colloidal gold/silver nanoparticles are not free of surfactant. Isolated aggregates, chain-like elongated aggregates and two-dimensional (2D) nanostructures were found to consist mostly of monolayers rather than agglomerations. With reference to correlated LSPR and SERS, combined experiments were carried out on a single platform at the same spatial position. The isolated aggregates mostly show a broadened and shifted SPR peak, whereas a weak blue-shifted peak is observed near 430 nm in addition to broadened peaks centered at 635 and 720 nm in the red spectral region in the chain-like elongated aggregates. In the case of 2D nanostructures, several SPR peaks are observed in diverse frequency regions. The characteristics of LSPR and SERS for the same gold nanoaggregates lead to a good correlation between SPR and SERS images. The elongated gold nanostructures show a higher enhancement of the Raman signal than the the isolated and 2D samples. In the case of SERS-active silver substrates for protein detection, a new approach has been adopted, in contrast to the conventional fabrication method. Colloidal silver nanoparticles are immobilized on the protein functionalized glass slides, and further SERS measurements are carried out based on LSPR excitations. A new strategy for the detection of biomolecules, particularly glutathione, under aqueous conditions is proposed. Finally, supramolecular J-aggregates of ionic dyes incorporated with silver colloidal aggregates are characterized by SERS measurements and correlated to finite-difference time-domain analysis with reference to LSPR excitations.

Surface plasmon-enhanced fluorescence on Au nanohole array for prostate-specific antigen detection

“…1 This phenomenon has been demonstrated by tremendous applications on chemical and biological sensors. [2][3][4][5][6] Highly enhanced local electromagnetic fields created by the resonantly pumped plasmonic nanostructures result in greatly increased incident light absorption and enhanced emitter excitation, supporting surface-enhanced spectroscopies including surface-enhanced Raman scattering, 7,8 surface-enhanced infrared spectroscopy, [9][10][11] and surface plasmon-enhanced fluorescence (SPFS). [12][13][14] Surface plasmons (SPs) with field E SP excited by an incoming light E 0 can enhance fluorophore excitation rate and Raman scattering by factors up to |E sp /E 0 | 2 and |E sp /E 0 | 4 , respectively.…”

The Effect of Laser Power on Photothermoacoustic Imaging of Blood Containing Gold Nanoparticles and Deoxygenation using a Frequency-Domain Phased Array Probe: An In-vitro Assay

“…Surface Plasmon Resonance (SPR)-based nanoparticles, or plasmonic nanoparticles, exhibit unique optical and thermal properties and have been extensively employed in biomedical applications [6][7][8][9][10][11]. Their major advantages are due to the photo physical properties of gold nanoparticles , for example, strong Localized Surface Plasmon Resonance (LSPR), surface-enhanced scattering , non-linear optical properties, tunable resonance across the Vis-NIR due to adjustable nanoparticle size and shape [12][13][14][15], biocompatibility due to their inert surface, nontoxicity, surface conjugation chemistry i.e., they can be linked to specific ligands for tumor targeting, imaging and therapies, lack of photo bleaching or blinking as with quantum dots, and very low oxidation [16,17]. The medical imaging modality employed for detection of malignant tumors in organs such as breast cancer should provide high-specificity to cancer and high resolution for early In situ detection [18].…”

The characteristic AgcoreAushell nanoparticles as SERS substrates in detecting dopamine molecules at various pH ranges

“…16,[21][22][23][24][25] The systematic investigation of the correlation between the aforementioned factors and the SERS activity of core-shell NPs is of great significance for the realization of highly efficient and reliable SERS substrates. Dopamine (DA) is a monoamine neurotransmitter in the catecholamine family, which plays a number of important physiological roles in animals.…”

“…In this regard, SERS measurements using metal colloids are advantageous owing to easy preparation, fast detection, and homogeneous reactions. 22,29 This work mainly focus on the influence of particle size and solution pH on the sensitive detection of DA molecules using Ag core Au shell NPs as SERS substrates. The maximal SERS activity of the core-shell NPs was obtained at an appropriate particle size and pH range (pH 7-9), highlighting the importance of probe-induced clustering of colloidal NPs for their enhanced SERS activity at physiological pH ranges.…”

“…19,22,34 Conversely, the Ag core Au shell NPs (38 nm) exhibit higher SERS activity than Ag core Au shell NPs (53 nm) with a plasmon band that is closer to the excitation wavelength of 633 nm. The SERS activity of the core-shell NPs is also dependent on the particle size, showing the key role of the particle size in the SERS measurements under plasmon resonance-assisted conditions.…”