Metal–Organic Frameworks as Surface Enhanced Raman Scattering Substrates with High Tailorability

Abstract

Surface enhanced Raman scattering (SERS) is a widely used analytical technique for detecting trace-level molecules based on an indispensable SERS substrate. SERS substrates with high tailorability are assumed to be attractive and desirable for SERS detection, because the substrates match the need for the selective detection of different species. Nevertheless, the rational design of such SERS substrates is rather challenging for both noblemetal and semiconductor substrates. Herein, expanding beyond conventional SERS substrates, we demonstrate that metal−organic framework (MOF) materials can serve as a type of SERS substrate with molecular selectivity, which are rarely realized for SERS detection without any special pretreatment. A salient structural characteristic of MOF-based SERS substrates benefiting the SERS selectivity is their high tailorability. By controlling the metal centers, organic ligands, and framework topologies of our MOF-based SERS substrates, we show that the electronic band structures of MOF-based SERS substrate can be purposively manipulated to match those of the target analytes, thus resulting in different detectable species. Going further, the SERS enhancement factors (EFs) of the MOF-based SERS substrates can be greatly enhanced to as high as 10 6 with a low detection limit of 10 −8 M by pore-structure optimization and surface modification, which is comparable to the EFs of noble metals without "hot spots" and recently reported semiconductors. This selective enhancement is interpreted as being due to the controllable combination of several resonances, such as the charge-transfer, interband and molecule resonances, together with the ground-state charge-transfer interactions. Our study opens a new venue for the development of SERS substrates with high-design flexibility, which is especially important for selective SERS detection toward specific analytes.

Remarkable surface-enhanced Raman scattering of highly crystalline monolayer Ti3C2 nanosheets

“…Although the EM-based noble-metal substrates show superior enhancement factors (EFs) of 10 6 or higher, they inevitably suffer from poor biocompatibility, nearly immobilized band structure, excessive cost and so on. In addition to noble-metals, SERS has also been found in semiconductors [18][19][20][21][22], metal-organic frameworks (MOFs) [23] and amorphous materials [24,25], in which Raman enhancement is thought to be the chemical mechanism (CM) caused by the charge-transfer between the analytes and the substrates. Particularly interesting is the recent discovery of SERS activity in conductive polymer films [26].…”

Understanding the Role of Metal–Organic Frameworks in Surface‐Enhanced Raman Scattering Application

“…Wang and co‐workers synthesized a core–shell SERS substrate, gold superparticles (GSPs)@ZIF‐8 particles consisting of a GSPs core, and ZIF‐8 shell (Figure 3B). [ 12b ] The PVP play an important role in maintaining the stability of preformed GSPs in organic solvents and facilitating the synthesis of an MOF shell. Additionally, the ionic surfactant, dodecyltrimethylammonium bromide (DTAB), is also introduced to moderate superparticles surface, thus depressing homogeneous crystallization of ZIF‐8 and generating one‐in‐one structure (Figure 3C,D).…”

“…MOFs have been used to address some challenges that traditional metal substrates cannot implement in SERS detection, and some researchers have noted the important roles of MOFs in MOF‐SERS systems. [ 12 ] Herein, we highlight the MOFs roles in MOF‐SERS platform, i.e., they actively interact with/enrich targets molecules, block interfering molecules, synergistically boost the Raman signal and even act as CM substrates, based on their versatile characteristics. MOF materials in SERS‐active substrates can change speed/intensity, specificity, and mode of interaction with analysts in real sample in both space and time.…”

Dynamic covalent chemistry steers synchronizing nanoparticle self-assembly with interfacial polymerization

“…The Raman bands at 1165, 1561, 1589 cm −1 are originated from TAPB-PDA. The bands at 1311 cm −1 are the most intense assigned to R6G and selected as featured band to study Raman signal enhancement [57][58][59] . First of all, let us compare the peak intensities for Au/ (Amor-TAPB-PDA) at 15 and 30°C, which are denoted as Au30/ (Amor-TAPB-PDA) and Au15/(Amor-TAPB-PDA), respectively.…”