Differential surface partitioning for an ultrasensitive solid-state SERS sensor and its application to food colorant analysis

Spectroscopic analyses of particle and energy aggregations at the interface of silver nanoparticles and fluorescent carbon nanodots

We study the change in the surface electromagnetic field provided by photoexcited silver nanoparticles as the field is disturbed by fluorescent carbon nanodots. Fluorescent carbon nanodots with an appropriate quantity and quality of surface functional groups are used to mediate the aggregation of silver nanoparticles of matching size and shape to form available nano-size conical structures. Carbon nanodots in the composite absorb and transfer additional photoenergy to the silver surface, resulting in energy aggregation within the cone structure and enhancement of the electromagnetic field in proximity to the silver surface. This elevated energy state is manifested in the strengthening of the SERS signal of the analytical probe 4-aminophenyl disulfide and the mechanism involved is elucidated by additional molecular spectroscopy studies.

High-Performance Au@Ag Nanorods Substrate for SERS Detection of Malachite Green in Aquatic Products

In order to improve the detection performance of surface-enhanced Raman scattering (SERS), a low-cost Au@Ag nanorods (Au@Ag NRs) substrate with a good SERS enhancement effect was developed and applied to the detection of malachite green (MG) in aquaculture water and crayfish. By comparing the SERS signal enhancement effect of five kinds of Au@Ag NRs substrates with different silver layer thickness on 4-mercaptobenzoic acid (4-MBA) solution, it was found that the substrate prepared with 100 µL AgNO3 had the smallest aspect ratio (3.27) and the thickest Ag layer (4.1 nm). However, it showed a good signal enhancement effect, and achieved a detection of 4-MBA as low as 1 × 10-11 M, which was 8.7 times higher than that of the AuNRs substrate. In addition, the Au@Ag NRs substrate developed in this study was used for SRES detection of MG in crayfish; its detection limit was 1.58 × 10-9 M. The developed Au@Ag NRs sensor had the advantages of stable SERS signal, uniform size and low cost, which provided a new tool for SERS signal enhancement and highly sensitive SERS detection method development.

Flexible surface-enhanced Raman scatting substrates: recent advances in their principles, design strategies, diversified material selections and applications

Surface-enhanced Raman scattering (SERS) is widely used as a powerful analytical technology in cutting-edge areas such as food safety, biology, chemistry, and medical diagnosis, providing ultra-fast, ultra-sensitive, nondestructive characterization and achieving ultra-high detection sensitivity even down to the single-molecule level. Development of Raman spectroscopy is strongly dependent on high-performance SERS substrates, which have long evolved from the early days of rough metal electrodes to periodic nanopatterned arrays building on solid supporting substrates. For rigid SERS substrates, however, their applications are restricted by sophisticated pretreatments for detecting solid samples with non-planar surfaces. It is therefore essential to reassert the principles in constructing flexible SERS substrates. Herein, we comprehensively review the state-of-the-art in understanding, preparing and using flexible SERS. The basic mechanisms behind the flexible SERS are briefly outlined, typical design strategies are highlighted and diversified selection of materials in preparing flexible SERS substrates are reviewed. Then the recent achievements of various interdisciplinary applications based on flexible SERS substrates are summarized. Finally, the challenges and perspectives for future evolution of flexible SERS and their applications are demonstrated. We propose new research directions focused on stimulating the real potential of SERS as an advanced analytical technique for commercialization.