Surface‐enhanced Raman scattering study of Ag@PPy nanoparticles

Abstract

Surface-enhanced Raman scattering (SERS) spectra of Ag@polypyrrole (PPy) nanoparticles with both 488 and 1064 nm excitation were investigated. Experimental results as well as theoretical analysis demonstrated that electromagnetic (EM) enhancement and charge transfer (CT) both rebounded to the SERS effect of Ag@PPy nanoparticles. When near-IR excitation (1064 nm) was used for the SERS measurements, the contribution from CT was amplified relative to that from EM because the energy of the near-IR excitation is far from the surface plasmon resonance of the nanosized Ag particles. The increased doping level of PPy, leading to optimal energy matching between the Fermi levels of the Ag nanoparticles and the energy levels in PPy molecules, could obviouslyenhance the SERS signal. These results suggested that the SERStechnique wasan effective tool for investigating the doping effect and interface interaction in metal-conductingpolymer composite nanoparticles. In particular, the SERS technique with near-IR excitation could give more information regarding the contribution of the charge-transfer mechanism to the spectral enhancement of this kind of system.

SERS Research Applied to Polymer Based Nanocomposites

“…In this methodology, metallic nanofillers are produced by chemical reduction of a metal precursor using reducing agents such as sodium citrate or sodium borohydride, in the presence of a polymer. This strategy generates nanocomposites whose morphology can vary, such as in a polymeric shell and a metal core [60,61,77,96,102], a polymeric core and a metal shell [95] or a polymeric matrix having dispersed metallic fillers [68,69,97]. In particular cases, the polymer can act as reducing agent due to specific functional groups, avoiding the use of an external reducing agent [61,73].…”

“…Synthetic Poly(amide) Ag Biomolecular detection [87] Poly(vinyl alcohol) Ag Biomolecular detection [95,101] Substrate characterization [97] Au Biomolecular detection [126] Medical diagnosis and target detection [126] Au@Ag Biomolecular detection [128] Cu@Ag Biomolecular detection [103] Poly(styrene) Ag Biomolecular detection [98] Substrate characterization [104] Medical diagnosis and target detection [98,117] Poly(vinylpyrrolidone) Ag Biomolecular detection [99,102,105] Poly(aniline) Ag Biomolecular detection [100] Poly(t-butylacrylate) Ag Biomolecular detection [113,114] Au Biomolecular detection [107] Poly(methyl methacrylate) Ag Biomolecular detection [115] Poly(acrylamide) Ag Biomolecular detection [118] Poly(acryloyl) Hydrazine Ag Biomolecular detection [162] Poly(ethylene glycol) Au Medical diagnosis and target detection [11,163] Heavy metal detection [122] Au@Ag SERS mapping and imaging [93] Poly(pyrrole) Ag Substrate characterization [96] poly(ethylene glycol) diacrylate…”

“…In this context, an important objective in the application of SERS substrates has been the analysis of vestigial amounts of the target analyte for which minimal specimen preparation is required [69,70,72,73,107,114,115]. This is relevant to implement analytical protocols as many SERS applications are foreseen, such as environmental monitoring [48,74], SERS mapping and imaging [67,68,93], medical diagnosis [109,124,126,151,160,161] and substrate characterization [71,96,107]. Table 2 lists polymer based composites mentioned in this chapter with the corresponding SERS applications by taking into account the type of polymer and the metal nanofillers employed.…”

Surface-Enhanced Raman Spectroscopy Study of 4-ATP on Gold Nanoparticles for Basal Cell Carcinoma Fingerprint Detection

“…Without selective detector, the Raman spectra only selected the lipid-and nucleotide-condensed regions from the others, which might lead to the misinterpretation if the healthy cells also have condensed organic organism; such as in the skin hole-close region shown in our experiment. Besides, no specific peaks would be applicable for a selective discrimination of BCC tissue from healthy tissue, which lead to long acquisition time for intraoperative diagnostic (5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20) h/mm 2 ) [7]. From all the results described above, only regions marked by A2, B2, C2 and D2 can be surely considered as the cancer areas, while A1, B1, C1 and D1 regions may assigned as the position of a hair-hole where the cell concentration also higher than others parts.…”

“…Since the discovery of this surface-enhanced Raman (SER) scattering in 1974 [9], SER scattering has been recognized as a powerful technique for biomedical applications. The application of SER scattering has been studied in cancer detection [10][11][12], widely in molecular structure analysis [13][14][15][16]. For non-labeling agent probes, the Raman spectra were analyzed by measuring the intrinsic signals to distinguish between healthy and diseased regions [10,11].…”