Probing Localized Surface Plasmons of Trisoctahedral Gold Nanocrystals for Surface Enhanced Raman Scattering

Abstract

ABSTRACT.Trisoctahedral (TOH) shaped gold (Au) nanocrystals (NCs) have emerged as a new class of metal nanoparticles (MNPs) due to its" superior catalytic and surface enhanced Raman scattering (SERS) activities caused by the presence of high density of atomic steps and dangling bonds on their high-index facets. We examine the radiative localized surface plasmon resonance (LSPR) modes of an isolated single TOH Au NC using cathodoluminescence (CL), with high resolution spatial information of the local density of optical states (LDOS) across the visible spectral range.Further, we show pronounced enhancement in the Raman scattering by performing Raman spectroscopic measurements on Rhodamine 6G (R6G) covered TOH Au NPs aggregates on a Si substrate. We believe that the hot spots between two adjacent MNP surfaces ("nanogaps") can be significantly stronger than single particle LSPRs. Such "nanogap" hotspots may have crucial role on the substantial SERS enhancement observed in this report. Consequently, the present study indicates that MNPs aggregates are highly desirable than individual plasmonic nanoparticles for possible applications in SERS based biosensing. 2 INTRODUCTION.

Size-tunable uniform gold octahedra: fast synthesis, characterization, and plasmonic properties

“…[8][9][10][11][12][13][14][15] Au NCs, one of the most important noble metal NCs, have been widely researched owing to their high chemical stability and intensive SPR properties. 7,16 To date, a number of synthetic approaches have been developed to afford anisotropic Au NCs in the shapes of cubes, 17 prisms, 18 plates, 19 decahedra, 20 trisoctahedra, 21 rods, 22,23 wires, 24 dendrites, 25 etc. Among them, the polyol process, which has been frequently used to prepare anisotropic metal nanoparticles, is a versatile and convenient method for the controllable synthesis of Au NCs.…”

A Highly Selective Economical Sensor for 4-Nitrophenol

“…Based on the arguments mentioned earlier, there is a great need for the development of a highly sensitive sensor for 4NP in order to protect the environment, human health, homeland security, and civilian safety [3]. Techniques such as liquid chromatography [8], gas chromatography-mass spectrometry [9], 1 H and 13 C nuclear magnetic resonance [10], energy dispersive X-ray diffraction [11], and surface-enhanced raman spectroscopy [12] have been employed for the detection of 4NP with high sensitivity. However, these methods are often expensive and inconvenient for use outside of the laboratory.…”

“…Simple optical methods have also been applied for nitroaromatic detection. In this regard, numerous studies have been devoted towards examining the photophysical properties of novel fluorescent materials such as Zn (salicylaldimine) complexes [13], N,N'bis(3-pentyl)perylene-3,4,9,10-bis(dicarboximide) [12], quantum dots [5,14,15], etc., for nitroaromatics detection. Synthesis of such optical organic sensors often involves multistep and time-consuming protocols that result in costly materials with low product yields.…”

In Situ Creation of Surface-Enhanced Raman Scattering Active Au–AuOx Nanostructures through Electrochemical Process for Pigment Detection

“…The mechanism of SERS consists of two major components, namely, the electromagnetic (EM) enhancement (approximately 10 4 –10 12 ), resulting from the enhancement of local EM fields at the surface of metal that can offer a surface plasma resonance from electron oscillation (e.g., Ag and Au), and chemical (CHEM) enhancement (up to 10 2 ), associated with a charge transfer between metal and adsorbate at atomic-scale roughness features. − Thus, the major contribution to the SERS enhancement can be attributed to the EM mechanism rather than the CHEM enhancement. Moreover, the distribution of electrochemical field was non-uniform around the plasmonic nanomaterials but highly localized in the relatively small radius of curvature, resulting in hotspots at the sharp edges . Additionally, these hotspots are located within crevices from two closely spaced plasmonic nanoparticles …”

“…Moreover, the distribution of electrochemical field was non-uniform around the plasmonic nanomaterials but highly localized in the relatively small radius of curvature, resulting in hotspots at the sharp edges. 11 Additionally, these hotspots are located within crevices from two closely spaced plasmonic nanoparticles. 10 Recently, numerous methodologies have been investigated for improving SERS performance.…”