Surface-enhanced Raman scattering substrates of high-density and high-homogeneity hot spots by magneto–metal nanoprobe assembling

Abstract

Binary naoparticles composed of a superparamagnetic Fe(3)O(4) core and an Au nanoshell were prepared via a high-temperature hydrolysis reaction followed by seed-mediated growth. The nanoprobes render simultaneous dual functions of both fast magnetic response and local surface plasmon resonance. Using these nanoprobes, analyte molecules can be easily biologically captured, magnetically concentrated, and analyzed by surface-enhanced Raman scattering (SERS). Particularly, the complex particles were assembled under magnetic force direction into a SERS substrate. It was found to possess both a high enhancement factor (10(6)) and high homogeneity of "hot spot" distribution (fluctuation less than 20% for a 1 μm(2) area) with 4-aminothiophenol as the analyte.

Ultrasensitive and reproducible SERS platform of coupled Ag grating with multibranched Au nanoparticles

“…[1][2][3][4] In particular, in the field of surfaceenhanced Raman spectroscopy (SERS), the application of surface plasmon phenomena represents a unique method for the detection of biomolecules, drugs, explosives, organic pollutants, heavy metals as well as in situ monitoring of chemical reactions. [5][6][7][8][9][10] Taking into account the basic requirements for the analysis of these compounds, an analytical approach must satisfy several requirements: (i) be fast and straightforward, (ii) achieve the detection limits that are as low as possible, and (iii) give reproducible and reliable results. SERS satisfies two of these three requirements: recent progress in this field allows taking measurements using the portable spectrophotometers, 11,12 and with up to one-molecule-level sensitivity, which was implemented in the last millennium.…”

Maximizing surface-enhanced Raman scattering sensitivity of surfactant-free Ag-Fe3O4 nanocomposites through optimization of silver nanoparticle density and magnetic self-assembly

“…[1][2][3][4][5][6] Among a large variety of magnetic nanocomposites comprised of different constitutes, combination of ferromagnetic materials with noble metals in an arrangement of core-shell configuration is of particular interest because of the resulting simultaneous optical and magnetic response as well as their flexible control through an application of external magnetic fields. [7][8][9][10][11][12][13][14][15][16][17][18] These bifunctional structures have demonstrated great potential in biosensing and bioimaging applications. For example, biocompatible crescent-shaped composite nanoparticles (NPs) made of multilayered Au/Fe/ Ag/Au have been used as efficient surface-enhanced Raman scattering (SERS) nanoprobes for biomolecular imaging with magnetically modulated detection of low-concentration molecules.…”

“…A general approach based on using 3-aminopropyltrimethoxysilane as a linker has been proposed to construct diverse multifunctional Fe 3 O 4 /metal hybrid nanostructures displaying magnetization, with example demonstrations of Au/Pt and Au/Ag NPs supported on the surface of Fe 3 O 4 microspheres. 10 Other typical strategies include ultrasonic synthesis method, 11 thermal decomposition, 12 high-temperature hydrolysis 14 and wetchemical method, 15 etc. From a practical point of view, SERS spectroscopy as a high-sensitivity identification technique of molecules usually has a very strict requirement on the cleanness of the enhancing substrates in order to minimize the interference signals from the substrates themselves such as pre-adsorbed surfactant molecules.…”

“…Therefore, controllable growth and distribution of noble metal NPs on Fe 3 O 4 microspheres or on more general magnetic templates is the key to maximizing the SERS sensitivity of such bifunctional composite nanostructures, but has been largely overlooked in previous studies. [7][8][9][10][11][12][13][14][15][16]28,29 This is the second critical problem we are attempting to tackle in the present work.…”

Magnetically Assembled SERS Substrates Composed of Iron–Silver Nanoparticles Obtained by Laser Ablation in Liquid

“…On the other hand, the application of externalm agnetic fields can be used to direct the assembly of magnetic-plasmonic NPs into arrays of SERS substrates. [41][42][43] All of these studies concerned hybrid structures composed of magnetic NPs with an oble-metalm oiety,s uch as heterostructures [27,28,31,35,42] or core-shells, [26,30,38,40,41,[44][45][46][47][48][49][50] whichr equire multiphase synthesis. To this aim, the exploitation of iron-doped silver nanoparticles (NPs) synthesized by laser ablation of abulk bimetallic iron-silver target immersedi ne thanol is described.…”