Real‐Time Probing Nanopore‐in‐Nanogap Plasmonic Coupling Effect on Silver Supercrystals with Surface‐Enhanced Raman Spectroscopy

Nanopore structures have displayed attractive prospects in diverse important applications such as nanopore‐based biosensors and enhanced spectroscopy. However, on the one hand, the fabrication techniques to obtain sub‐10 nm sized nanopores so far is very limited. On the other hand, the electromagnetic enhancement of nanopores is still relatively low. In this work, using a facile chemical etching strategy on 2D plasmonic Ag nanoparticle supercrystals, fine nanopore arrays with sub‐10 nm pore size have been successfully fabricated and a “nanopore‐in‐nanogap” hybrid plasmon mode has been investigated. An in situ etching and surface‐enhanced Raman spectroscopy (SERS) detection indicate that novel hybrid plasmon structure may create an enhanced electromagnetic coupling and increase SERS signal at ≈10× magnification. The breaking of plasmon bonding dipolar mode and generation of antibonding‐like plasmon mode contribute to this enhanced electromagnetic coupling. The facile etching strategy, as a common approach, may open the doors for the fabrication of nanopores in various compositions for numerous applications.     

Gold Nanoparticles and g‐C3N4‐Intercalated Graphene Oxide Membrane for Recyclable Surface Enhanced Raman Scattering

Toxic organic pollutants in the aquatic environment cause severe threats to both humans and the global environment. Thus, the development of robust strategies for detection and removal of these organic pollutants is essential. For this purpose, a multifunctional and recyclable membrane by intercalating gold nanoparticles and graphitic carbon nitride into graphene oxide (GNPs/g‐C₃N₄/GO) is fabricated. The membranes exhibit not only superior surface enhanced Raman scattering (SERS) activity attributed to high preconcentration ability to analytes through π–π and electrostatic interactions, but also excellent catalytic activity due to the enhanced electron–hole separation efficiency. These outstanding properties allow the membrane to be used for highly sensitive detection of rhodamine 6G with a limit of detection of 5.0 × 10^?14m and self‐cleaning by photocatalytic degradation of the adsorbed analytes into inorganic small molecules, thus achieving recyclable SERS application. Furthermore, the excellent SERS activity of the membrane is demonstrated by detection of 4‐chlorophenol at less than nanomolar level and no significant SERS or catalytic activity loss was observed when reusability is tested. These results suggest that the GNPs/g‐C₃N₄/GO membrane provides a new strategy for eliminating traditional, single‐use SERS substrates, and expands practical SERS application to simultaneous detection and removal of environmental pollutants.     

Plasmonic Core–Shell–Satellites with Abundant Electromagnetic Hotspots for Highly Sensitive and Reproducible SERS Detection

In this work, we develop a Ag@Al₂O₃@Ag plasmonic core–shell–satellite (PCSS) to achieve highly sensitive and reproducible surface-enhanced Raman spectroscopy (SERS) detection of probe molecules. To fabricate PCSS nanostructures, we employ a simple hierarchical dewetting process of Ag films coupled with an atomic layer deposition (ALD) method for the Al₂O₃ shell. Compared to bare Ag nanoparticles, several advantages of fabricating PCSS nanostructures are discovered, including high surface roughness, high density of nanogaps between Ag core and Ag satellites, and nanogaps between adjacent Ag satellites. Finite-difference time-domain (FDTD) simulations of the PCSS nanostructure confirm an enhancement in the electromagnetic field intensity (hotspots) in the nanogap between the Ag core and the satellite generated by the Al₂O₃ shell, due to the strong core–satellite plasmonic coupling. The as-prepared PCSS-based SERS substrate demonstrates an enhancement factor (EF) of 1.7 × 10⁷ and relative standard deviation (RSD) of ~7%, endowing our SERS platform with highly sensitive and reproducible detection of R6G molecules. We think that this method provides a simple approach for the fabrication of PCSS by a solid-state technique and a basis for developing a highly SERS-active substrate for practical applications.     

基于金、银溶胶的表面增强拉曼光谱法测定苹果中马拉硫磷含量对比研究

使用共焦显微拉曼光谱仪,结合表面增强拉曼散射技术,将含有农药马拉硫磷的苹果汁样本进行一定的前处理后,分别采集其基于金、银溶胶的表面增强拉曼光谱,结合逐步多元线性回归方法对两种光谱分别进行数学建模分析。结果表明,在0.01～0.5 mg/kg的线性范围内,基于金溶胶所建立的模型相关系数（R2）为0.999 6,校正标准差为0.001 86 mg/kg,真实值与拟合值差异最大不超过0.003 mg/kg,而基于银溶胶所建立的模型相关系数（R2）为1,校正标准差为0.000 78 mg/kg,真实值与拟合值差异最大不超过0.001 2 mg/kg,预测标准差分别为0.213 mg/kg和0.146 mg/kg,银溶胶效果优于金溶胶。     

Feasibility of colloidal silver SERS for rapid bacterial screening

This study reports the feasibility of citrate-reduced colloidal silver surface-enhanced Raman scattering (SERS) for differentiating three important food borne pathogens, E. coli, Listeria, and Salmonella. FT-Raman and SERS spectra of both silver colloids and colloid-K₃PO₄ mixtures were collected and analyzed to evaluate the reproducibility and stability of silver colloids fabricated in a batch-production process. The results suggest that the reproducibility of the colloids over the batch process is high and that their binding effectiveness remains consistent over a 60-day storage period. Two specific SERS bands at 712 and 390 cm⁻¹ were identified and used to develop simple 2-band ratios for differentiating E. coli-, Listeria-, and Salmonella-colloid mixtures with a 100% success. These results indicate that colloidal silver SERS technique may be a practical alternative method suitable for routine and rapid screening of E. coli, Listeria, and Salmonella bacteria.     

在银胶体系中罗丹明B单分子水平上拉曼光谱研究

采用表面增强托曼散射（SERS）技术,比较了单分子水平上银胶纳米体系中罗丹明B（RhB）浓度为10^-11mol／L以下的拉曼光谱和通常单分子水平上罗丹明6G（Rh6G）浓度在10^-11mol／L的拉曼光谱,无论自由沉积在玻璃表面还是在液体环境下的结果显示,单分子水平上Rh B的拉曼光谱灵敏度是Rh 6G的2倍多。因此,利用RhB作为探测试剂将能够提供更加丰富的信息,这对单分子的光谱研究以及高灵敏度探测试剂的应用研究具有重要的意义。     

Au/Si-NPA复合纳米体系的SERS增强能力研究

利用具有准周期结构的硅纳米孔柱阵列(silicon nanoprous pillar array,Si-NPA)为衬底使用浸渍法制备优化Au/Si-NPA活性基底。并利用最优化制备的Au/Si-NPA活性基底对罗丹明6G(Rhoda-mine 6G,R6G)进行探测,研究其表面增强拉曼散射(surface enhanced Raman scattering,SERS)光谱并对其增强原理进行解释。     

Effects of nitrogen doping on surface-enhanced Raman scattering (SERS) performance of bicrystalline TiO2 nanofibres

In this work, we successfully synthesized bicrystalline anatase/TiO_2(B) nanofibre and used it as active substrate for surface-enhanced Raman scattering(SERS) applications. The bicrystalline structured TiO_2 substrates provide additional charge transfer across the anatase-TiO_2(B) interface and thus enhanced activity compared to the pure single crystalline phase. With an effort to further increase the sensitivity of SERS, nitrogen element was doped into bicrystalline anatase/TiO_2(B) nanofibres(N-TiO_2) and higher SERS enhancement was achieved. The nitrogen content was controlled by tuning the calcination temperature of titanate precursor at 500, 600 and 700 °C,respectively. The sample calcined at 600 °C(NT600) acquires the highest percentage of nitrogen element due to its open pore structure that facilitates the diffusion of nitrogen during calcination. Raman intensity depends on the amount of nitrogen doping, thus NT600 exhibited the best SERS activity. The doped nitrogen in TiO_2 facilitates the charge transfer between TiO_2 and probing molecules and thus suppresses the electron–hole recombination. This work provides a new perspective on the design of efficient TiO_2 SERS active substrate and is expected to be valuable for adsorbate detection on semiconductor surface.     

表面增强拉曼散射法检测联苯胺

利用水热法合成聚乙烯吡咯烷酮包金(Au@PVP)核壳纳米粒子,通过氢键的作用使联苯胺吸附在Au@PVP核壳纳米粒子表面增强拉曼基底上,优化激发光波长、选择合适的pH值条件,利用其内核金纳米粒子的等离子共振效应实现了对联苯胺分子的高灵敏度表面增强拉曼检测,检测限达到10~(-9)mol/L。此值与GB 3838—2002《地表水环境质量标准》中用气相色谱法检测集中式生活饮用地表水源的特定分析方法检测联苯胺的检测限相比,降低了接近3个数量级。