Polyethylenimine-interlayered core–shell–satellite 3D magnetic microspheres as versatile SERS substrates

Abstract

Precise fabrication of subtle nanogaps amid individual nanoparticles or between adjacent ones to obtain the highest SERS enhancement is still a challenge. Here, we reported a novel approach for fabricating core-shell-satellite 3D magnetic microspheres (CSSM), that easily form a porous 1.5 nm PEI interlayer to accommodate molecules and create sufficient hotspots between the inner Fe3O4@Ag core and outer assembled Au@Ag satellites. Experiments and finite-difference time-domain (FDTD) simulation demonstrated that the enhancement factor (EF) was about 2.03 × 10(8) and 6.25 × 10(6), respectively. In addition, the micro-scale magnetic core endowed the CSSM with a superior magnetic nature, which enabled easy separation and further enhanced Raman signals due to enrichment of targeted analytes and abundant interparticle hotspots created by magnetism-induced aggregation. Our results further demonstrated that the CSSM is expected to be a versatile SERS substrate, which has been verified by the detection of the adsorbed pesticide thiram and the non-adsorbed pesticide paraquat with a detection limit as low as 5 × 10(-12) M and 1 × 10(-10) M, respectively. The novel CSSM can overcome the long-standing limitations of SERS for the trace characterization of various analytes in different solutions and promises to transform SERS into a practical analytical technique.

SERS detection of heterogeneous reactions at catalytic interfaces using bifunctional metal nanoparticles

“…图 2 Au-PtFe"核-卫星"结构静电吸附组装示意图(a)以及 SEM、TEM图(b) [28] ; Fe 3 O 4 @Ag-Au@Ag结构组装示意图(c) 以及SEM图(d) [26] (网络版彩图) 图 3 (a, b) Au-Pt-Au合成示意图和TEM图 [35] ; (c~e) Ag-AgPd纳米方块的合成示意图、TEM图以及元素分布图 [31] ; (f, g) Pd沉积到Au shell的示意图以及SEM图 [42] (网络版 彩图) 原子层 [37] . 当基底的电子结构发生改变时, 吸附分子 38~40] , 基于此, Wu等 [41] 通过在体系中加入2,6-二甲基苯异腈分子, 从 .…”

Polyethyleneimine-mediated seed growth approach for synthesis of silver-shell silica-core nanocomposites and their application as a versatile SERS platform

“…Basing on our previous studies, [19][20][21] we proposed a polyethyleneimine (PEI)-mediated seed growth method to achieve highly reproducible and controllable coating silica spheres with complete Ag shells in this study. PEI was used to form a bifunctional thin interlayer to achieve the absorption of dense Au NPs as seeds and keep the nanostructure stable during shell growth.…”

Surface enhanced Raman spectroscopy (SERS) for in vitro diagnostic testing at the point of care

“…When functionalized with sensing ligands, this allows for faster, more automated washing steps while also preventing sample sedimentation often seen with repeated centrifugation [29,163]. Magnetic nanoparticles can also provide a plasmonic response when coated in gold or silver [164], therefore improving SERS enhancement capabilities [165][166][167]. Many groups have facilitated this technique for improving clinical chemistry techniques recently, such as Wang et al who used aptamers immobilized onto silvercoated magnetic nanoparticles along with a secondary SERS active gold nanoprobe coated with another aptamer to capture and quantify bacterial cells down to 10 cells/ml [168].…”