Tuning SERS for living erythrocytes: Focus on nanoparticle size and plasmon resonance position

Abstract

Surface‐enhanced Raman spectroscopy (SERS) is a unique technique to study submembrane hemoglobin (Hbsm) in erythrocytes. We report the detailed design of SERS experiments on living erythrocytes to estimate dependence of the enhancemen t factor for main Raman bands of Hbsm on silver nanoparticle (AgNP) properties. We demonstrate that the enhancement factor for ν 4/A1g, ν 10/B1g and A2g Raman bands of Hbsm varies from 105 to 107 under proposed experimental conditions with 473 nm laser excitation. For the first time we show that the enhancement of Raman scattering increases with the increase in the relative amount of small NPs in colloids, with the decrease in AgNP size and with plasmon resonance shift to the shorter wavelength region. Obtained results can be explained by the ability of smaller AgNPs to get deeper into nano‐invaginations of the plasma membrane than larger AgNPs. This shortens the distance between small AgNPs and Hbsm and, consequently, leads to the higher enhancement of Raman scattering of Hbsm. The enhancement of higher wavenumber bands ν 10/B1g and A2g is more sensitive to AgNPs’ size and the relative amount of small AgNPs than the enhancement of the lower wavenumber band ν 4/A1g. This can be used for AgNP‐controlled enhancement of the desired Raman bands and should be taken into account in biomedical SERS experiments. Copyright © 2013 John Wiley & Sons, Ltd.

Evaluation of toxicity of silver ions and nanoparticles using model bacteria with luminescent phenotype

“…As was shown previously, the obtained SNP had irregular size distribution with most particles being spherical; however, particles of different shapes were also observed [17]. The size of the obtained SNP was determined using the method of dynamic light scatter-ing (Zetasizer Nano ZS, Malvern, United Kingdom).…”

Revisiting preparation routes of SERS materials

“…Several series of silver nanoparticles and nanostructures were prepared (Table 1) according to known (Series A-C, I) [1-3, 6, 7, 11-17] and new schemes (Series D-H, J). Series C Silver platelets preparation by grain selective regrowth of nuclei [11,14] Series D Direct reduction of fresh water suspension of solid silver (I) oxide with an excess of Series I The Leopold-Lendl method, reduction of silver nitrate with alkali solution of hydroxylamine hydrochloride [6,8,16] Series J Soft thermal pyrolysis of diamminesilver hydroxide [5,12,15] The samples of Series A and B were prepared by simple reduction of silver (I) nitrate in aqueous solution with commonly used organic and inorganic substances as noted in Table 1.…”

“…Silver nanoparticles and nanostructured materials are a common choice for SERS measurements due to their broad plasmon resonance, high stability, facile fabrication methods and the largest enhancement for special molecules [3][4][5]. A complex morphology such as nanoflowers, nanorices, cubes, multipods and nanodendrites, mesocages is achieved by kinetically controlled, aggregation-based, heterogeneously seeded, template-directed growth, selective etching and colloidal system aging; the polyol technique allows one to synthesize silver nanoparticles of a wide variety of shapes and sizes [6][7][8][9][10][11][12][13][14][15][16]. Despite of all possible advantages, the nanoparticles themselves are likely to aggregate uncontrollably in solutions, making it difficult to reproduce SERS results [5,6,11,14]; nanoparticle sols exhibit limited plasmonic tunability as compared to a new class of nanomaterials -colloidosomes composed of a dielectric core and a concentric metal shells with hybridization of plasmon modes supported by an inner cavity and an outer surface of the nanoshell [5,7,9,10].…”

“…A complex morphology such as nanoflowers, nanorices, cubes, multipods and nanodendrites, mesocages is achieved by kinetically controlled, aggregation-based, heterogeneously seeded, template-directed growth, selective etching and colloidal system aging; the polyol technique allows one to synthesize silver nanoparticles of a wide variety of shapes and sizes [6][7][8][9][10][11][12][13][14][15][16]. Despite of all possible advantages, the nanoparticles themselves are likely to aggregate uncontrollably in solutions, making it difficult to reproduce SERS results [5,6,11,14]; nanoparticle sols exhibit limited plasmonic tunability as compared to a new class of nanomaterials -colloidosomes composed of a dielectric core and a concentric metal shells with hybridization of plasmon modes supported by an inner cavity and an outer surface of the nanoshell [5,7,9,10]. However, SERS still suffers a lack of reproducibility due to the masking of SERS signals by surfactants or by-products, gradients of electric fields near the nanoparticles and variations of molecule positions with respect to the nanoparticles; commonly used linkers, surfactants, reducing agents and their oxidized forms, halide ions can change the characteristic properties of nanoparticles because of their aging, recrystallization or random formation of aggregates [5,[11][12][13][14].…”

SERS Nanotags and Their Applications in Biosensing and Bioimaging

“…These plasmonic properties can be tuned by changing the physical properties such as shape [44][45][46][47], size [48][49][50][51] and dimensionality (2D and 3D) [52][53][54] of the plasmonic nanostructures. Over the last 3 decades, researchers have made great progress in the development of SERS plasmonic nanostructures to maximize enhancement factors (EFs).…”