Multifunctional Silver‐Embedded Magnetic Nanoparticles as SERS Nanoprobes and Their Applications

In this study, surface‐enhanced Raman spectroscopy (SERS)‐encoded magnetic nanoparticles (NPs) are prepared and utilized as a multifunctional tagging material for cancer‐cell targeting and separation. First, silver‐embedded magnetic NPs are prepared, composed of an 18‐nm magnetic core and a 16‐nm‐thick silica shell with silver NPs formed on the surface. After simple aromatic compounds are adsorbed on the silver‐embedded magnetic NPs, they are coated with silica to provide them with chemical and physical stability. The resulting silica‐encapsulated magnetic NPs (M‐SERS dots) produce strong SERS signals and have magnetic properties. In a model application as a tagging material, the M‐SERS dots are successfully utilized for targeting breast‐cancer cells (SKBR3) and floating leukemia cells (SP2/O). The targeted cancer cells can be easily separated from the untargeted cells using an external magnetic field. The separated targeted cancer cells exhibit a Raman signal originating from the M‐SERS dots. This system proves to be an efficient tool for separating targeted cells. Additionally, the magnetic‐field‐induced hot spots, which can provide a 1000‐times‐stronger SERS intensity due to aggregation of the NPs, are studied.     

Controlled Assembly of Highly Raman‐Enhancing Silver Nanocap Arrays Templated by Porous Anodic Alumina Membranes

A convenient nanoscale technique is reported for the fabrication of highly ordered hemispherical silver nanocap arrays templated by porous anodic alumina (PAA) membranes as robust and cost‐efficient surface‐enhanced Raman scattering (SERS) substrates. This geometry produces a high Raman signal due to its periodic hexagonal arrangements and control of the gap between the nanostructures in the sub‐10‐nm regime. The surface structure can be tuned further to optimize the enhancement factor according to optional PAA fabrication and silver deposition parameters. Finite‐difference time‐domain calculations indicate that the structure may possess excellent SERS characteristics due to the high density and abundance of hot spots.     

Nanostructured surfaces and assemblies as SERS media

Metallic nanostructures attract much interest as an efficient media for surface-enhanced Raman scattering (SERS). Significant progress has been made on the synthesis of metal nanoparticles with various shapes, composition, and controlled plasmonic properties, all critical for an efficient SERS response. For practical applications, efficient strategies of assembling metal nanoparticles into organized nanostructures are paramount for the fabrication of reproducible, stable, and highly active SERS substrates. Recent progress in the synthesis of novel plasmonic nanoparticles, fabrication of highly ordered one-, two-, and three-dimensional SERS substrates, and some applications of corresponding SERS effects are discussed.     

Ultrasensitive Telomerase Activity Detection by Telomeric Elongation Controlled Surface Enhanced Raman Scattering

Telomerase is now considered to be a valuable biomarker and therapeutic target in the diagnosis and treatment of cancerous diseases, which brings an urgent need in the development of fast and efficient telomerase detection strategies. Here, a new surface enhanced Raman scattering (SERS) based protocol using telomeric elongation controlled SERS (TEC‐SERS) effect for the ultrasensitive telomerase detection is presented. The TEC‐SERS protocol not only provides an unprecedented high sensitivity but also avoids laborious PCR procedures. The detection limit is ≈2–3 orders of magnitude lower than those of previously reported methods. This highly sensitive and straightforward TEC‐SERS protocol can be developed as a routine telomerase detection method, which would greatly facilitate the telomerase based ultra‐early diagnosis of malignant tumors and the fast screening of anti‐cancer drugs.     

M‐shaped Grating by Nanoimprinting: A Replicable,Large‐Area,Highly Active Plasmonic Surface‐Enhanced Raman Scattering Substrate with Nanogaps

Plasmonic nanostructures separated by nanogaps enable strong electromagnetic‐field confinement on the nanoscale for enhancing light‐matter interactions, which are in great demand in many applications such as surface‐enhanced Raman scattering (SERS). A simple M‐shaped nanograting with narrow V‐shaped grooves is proposed. Both theoretical and experimental studies reveal that the electromagnetic field on the surface of the M grating can be pronouncedly enhanced over that of a grating without such grooves, due to field localization in the nanogaps formed by the narrow V grooves. A technique based on room‐temperature nanoimprinting lithography and anisotropic reactive‐ion etching is developed to fabricate this device, which is cost‐effective, reliable, and suitable for fabricating large‐area nanostructures. As a demonstration of the potential application of this device, the M grating is used as a SERS substrate for probing Rhodamine 6G molecules. Experimentally, an average SERS enhancement factor as high as 5×10⁸ has been achieved, which verifies the greatly enhanced light–matter interaction on the surface of the M grating over that of traditional SERS surfaces.     

DNA‐Mediated Morphological Control of Silver Nanoparticles

It is demonstrated that DNA can be used to control the synthesis of silver nanoplates with different morphologies using spherical silver seeds. UV–vis spectroscopy, transmission electron microscopy, scanning electron microscopy, X‐ray photoelectron spectroscopy, and Raman spectroscopy are used to characterize the synthesized nanoparticles. Silver nanoprisms are encoded by poly C and poly G, while silver flower bouquets and silver nanodiscs are synthesized using poly A and poly T, respectively. The length of DNA is found to have little effect on the morphology of silver nanoparticles. Moreover, the synthesized silver nanoplates are found to have high surface enhanced Raman scattering enhancement ability, good antibacterial activity, and good biocompatibility. These discoveries will broaden the application of DNA in nanoscience and will provide a new platform to investigate the interaction between DNA sequences and silver nanoparticles.     

负载银簇的硅基杂化纳米颗粒制备及其SERS性能

本研究发展了一种简便的"原位还原"策略构建负载银簇的硅基杂化纳米颗粒(Ag@SHNPs)。首先利用两亲性嵌段共聚物PS₈₉-b-PAA₁₆自组装行为和3-巯基丙基三甲氧基硅烷(MPTMS)在亲水链段PAA区域的水解缩聚反应形成有机硅胶束杂化纳米结构,再利用有机硅骨架中丰富的巯基作为还原位点,原位将银盐转化为银簇,最终得到负载银簇的硅基杂化纳米颗粒,并对该杂化纳米颗粒的形貌、结构以及成分组成作了分析。通过测试材料对不同细胞系的毒性验证了其良好的生物相容性。最后以4-巯基苯甲酸(4-MBA)为探针分子,对硅基杂化颗粒基底的表面增强拉曼散射(SERS)活性进行检测。在532 nm波长的激光激发下, 4-MBA标记的硅基杂化纳米颗粒展示出明显的拉曼信号增强特性,增强因子约为10⁵。因此,该硅基杂化基底材料在SERS生物成像和高灵敏检测方面具有潜在的应用前景。     

Localized Surface Plasmon Induced Position‐Sensitive Photodetection in Silicon‐Nanowire‐Modified Ag/Si

Surface plasmon‐based approaches are widely applied to improve the efficiency of photoelectric devices such as photosensors and photocells. In order to promote the light absorption and electron–hole pair generation in devices, metallodielectric nanostructures are used to boost the growth of surface plasmons. Here, silicon nanowires (SiNWs) are used to modify a metal–semiconductor structure; thus, Ag/SiNWs/Si is manufactured. In this system, a large increased lateral photovoltaic effect (LPE) is detected with a maximum positional sensitivity of 65.35 mV mm^?1, which is ≈53‐fold and 1000‐fold compared to the conventional Ag/Si (1.24 mV mm^?1) and SiNWs/Si (0.06 mV mm^?1), respectively. It is demonstrated that localized surface plasmons (LSPs) contribute a lot to the increment of LPE. Furthermore, through the surface‐enhanced Raman scattering spectra of rhodamine‐6G and finite‐difference time‐domain simulation, it is illustrated that silver‐coated SiNWs support strong LSPs. The results propose an enhancement mechanism based on LSPs to facilitate the photoelectric conversion in LPE and offer an effective way to improve the sensitivity of photodetectors.