Self‐assembly at Liquid‐Liquid Interface: A New SERS Substrate for Analytical Sensing^†

Abstract

Comprehensive Summary As a highly powerful and sensitive tool, surface enhanced Raman scattering (SERS) has attracted extensive attention in quantification analysis. However, the strong dependence of SERS signal on the detailed local nanostructure makes quantitative SERS analysis suffer from difficulties in controlling the uniformity of nanoscale hot spots and the inefficiency of placing the targeted molecules in prefabricated hot spots. Thus, the development of uniform SERS substrates is becoming an urgent demand to impulse SERS technique for the application in practical systems. The self‐assembly of nanoparticles (NPs) at the liquid‐liquid interface (LLI) provides a molecular sharp and defect‐free focal plane, in which the stable controlling of nanogap sizes and the feasible location of analytes can be virtually guaranteed, leading to greatly enhanced sensitivity and reproducibility of detections. On the other hand, the benefit of liquid/liquid systems allows for either hydrophilic, hydrophobic molecules to be captured and detected individually or simultaneously. Based on these advantages of the new SERS substrate, a variety of self‐assembled NP arrays at the LLI have been developed for multiphase analyte detection. Herein, we review recently developed strategies to induce NPs self‐assembly at the LLI and discuss the latest research progress on sensitive and reliable SERS analysis in practical applications. Finally, some perspectives are highlighted in the further development of the efficient methods to enhance the plasmonic properties and more practical SERS sensors for practical applications.

Recent Research Progress of Surface‐Enhanced Raman Scattering Dominated Analysis Strategies in Early Diagnosis of Diseases

“…Besides, the homogeneity and reproducibility of SERS substrates are crucial for accurate measurement of disease markers. Recently, the microfluidic synthesis system, [238] nanoimprinting technique, [239] and self‐assembly at liquid‐liquid interface approach [240] have been reported in succession, which may be expected to solve the above problems. Lack of comprehensive and in‐depth research on the biosafety of SERS tags. Currently, although some proposed SERS tags have been applied to in vivo diagnosis, the biological toxicity, biocompatibility, and long‐term metabolic issues need to be further researched [241–243] .…”

“…Besides, the homogeneity and reproducibility of SERS substrates are crucial for accurate measurement of disease markers. Recently, the microfluidic synthesis system, [238] nanoimprinting technique, [239] and self‐assembly at liquid‐liquid interface approach [240] have been reported in succession, which may be expected to solve the above problems.…”

Separation and Identification of Nanoplastics via a Two-Phase System Combined with Surface-Enhanced Raman Spectroscopy

“…The "hot spots" can increase the intensity of the Raman signal of nanoplastics that is measured on the surface of Ag NPs. 12,25,26 To investigate the behavior of nanoplastics in the two-phase system, WCA and OCA tests were performed for PS and PET nanoplastics. As shown in Figure 2, the WCAs of PS and PET nanoplastics are 149.3 ± 0.15 and 139.4 ± 0.36°, respectively.…”

Ag Nanoparticle/Au@Ag Nanorod Sandwich Structures for SERS-Based Detection of Perfluoroalkyl Substances

“…However, the vast majority of these methods require expensive instruments and stringent environmental conditions, e.g., atomic layer deposition (ALD) and molecular beam epitaxy (MBE). By comparison, the solution-based interface self-assembly method offers a cost-effective and efficient route to nanofilm assembly. , In particular, self-assembly at the oil–water interface requires only a beaker and syringe to produce a monolayer and is ready to transfer it to the silicon substrate in a short time. Moreover, the densely packed self-assembly metal monolayer can not only produce highly reproducible Raman signals but also generate enormous EM enhancement due to the coupling effect of the adjacent nanoparticle units.…”