Optoplasmonic MOFs film for SERS detection

A Review on the Recent Progress of Metal-Organic Frameworks Based Surface Enhanced Raman Scattering Sensors

Surface enhanced Raman scattering (SERS) has evolved into a significant fingerprint spectroscopic technique for rapidly and nonintrusively tracing target analytes through effective SERS substrates. Metal-organic frameworks (MOFs), as a boom crystalline porous material, serve as promising SERS substrates by accommodating noble metal nanoparticles (NPs) to produce MOFs-based SERS-active materials. Recently, MOFs-based SERS materials (MNPs/MOFs) have gained significant attention due to their enhanced sensing performance. The unique porous nature of MOFs provides an efficient capture capability for analytes, while their shells prevent NPs from oxidization and corrosion, thereby enhancing the consistency of SERS substrates. So far, numerous MNPs/MOFs sensors have been documented. This review outlines the research progress of MNPs/MOFs composites, focusing on the classification, synthesis strategies, and applications in environment analysis, real-time monitoring, food safety, etc.

Facile synthesis of novel Ni-BDC-NH2/Au NPs SERS substrates with synergistic enhancement effects for high-performance detection

Substrate materials with high sensitivity and good reproducibility are highly desirable for the practical applications of surface-enhanced Raman scattering (SERS) techniques. In this study, a novel gold nanoparticle-loaded Ni-based metal-organic framework (Ni-BDC-NH2/Au NPs) SERS substrate was successfully synthesized via an electrostatic self-assembly method. The enhancement of the SERS signal is achieved owing to the synergy between the chemical enhancement (CM) effect of Ni-BDC-NH2 and the electromagnetic enhancement (EM) of Au NPs, and the enriching of the analyte near the SERS "hot spots" through the strong adsorption capacity of Ni-BDC-NH2. The Ni-BDC-NH2/Au NPs exhibited a high enhancement factor (EF) of 1.10 × 107 and a low detection limit of 5 × 10-9 mol L-1. Besides, the substrate material showed exceptional stability for up to 45 days at room temperature. The Ni-BDC-NH2/Au NPs was used to detect methylene blue (MB), displaying a wide linear range (5 × 10-7 to 5 × 10-5 mol L-1) and high recoveries (86.82-104.46%). These results indicate that the Ni-BDC-NH2/Au NPs hybrid substrate has great potential for the detection of environmental pollution in practical applications.

Metalation of metal-organic frameworks: fundamentals and applications

Metalation of metal-organic frameworks (MOFs) has been developed as a prominent strategy for materials functionalization for pore chemistry modulation and property optimization. By introducing exotic metal ions/complexes/nanoparticles onto/into the parent framework, many metallized MOFs have exhibited significantly improved performance in a wide range of applications. In this review, we focus on the research progress in the metalation of metal-organic frameworks during the last five years, spanning the design principles, synthetic strategies, and potential applications. Based on the crystal engineering principles, a minor change in the MOF composition through metalation would lead to leveraged variation of properties. This review starts from the general strategies established for the incorporation of metal species within MOFs, followed by the design principles to graft the desired functionality while maintaining the porosity of frameworks. Facile metalation has contributed a great number of bespoke materials with excellent performance, and we summarize their applications in gas adsorption and separation, heterogeneous catalysis, detection and sensing, and energy storage and conversion. The underlying mechanisms are also investigated by state-of-the-art techniques and analyzed for gaining insight into the structure-property relationships, which would in turn facilitate the further development of design principles. Finally, the current challenges and opportunities in MOF metalation have been discussed, and the promising future directions for customizing the next-generation advanced materials have been outlined as well.

Preparation of SERS base membrane with cellulose compound dopamine and determination of hypochlorite

Flexible silver substrates were made by in situ reduction of silver nanoparticles in bacterial cellulose membranes using the unique advantage of dopamine. Subsequently, we modified the substrate with 4-mercaptophenol (4-MP), a molecule capable of specifically recognizing ClO-, and its corresponding SERS signal changes with the concentration of hypochlorite, thus allowing the quantitative detection of ClO- content. The method showed a negative linear correlation (R2 = 0.9567) with the SERS intensity at 1077 cm-1 over the concentration range 0.5-100 µM, and the detection limit was 0.15 µM. The RSD of the SERS intensity at 1077 cm-1 under five batches was 4.2%, which proved the good reproducibility of P-BCM-Ag NP-MP. Finally, the P-BCM-Ag NPs were used for the detection of hypochlorite in cell contents, artificial urine, and clinical serum samples, utilizing spike experiments in all three environments. The recoveries were in the range 90-110% indicating the accuracy of the method for the detection of hypochlorite and validating the promising application of this assay for practical detection in intricate biological samples.

Fabrication of MIL-101(Cr)/silver nanocomposites as SERS substrate for sensitive determination of malachite green and crystal violet in tilapia

Nanocomposites with multiple functions have attracted much attention in designing novel SERS substrates. In this report, the enrichment ability of MIL-101(Cr) and the local surface plasma resonance (LSPR) of silver nanoparticles are combined to fabricate a SERS substrate denoted as MIL-101-MA@Ag, which can simultaneously produce high-density and uniformly distributed hot spots. Moreover, the enrichment ability of MIL-101(Cr) can further improve the sensitivity by concentrating and transferring the analytes in the vicinity of hot spots. Under optimal conditions, MIL-101-MA@Ag showed good SERS activity for malachite green (MG) and crystal violet (CV), with detection limits as low as 9.5×10-11 M and 9.2×10-12 M at 1616 cm-1, respectively. The prepared substrate has been successfully applied to detect MG and CV in tilapia, the recovery rate of fish tissue extract was 86.4~102%, and the relative standard deviation (RSD) was 8.9~15%. The results demonstrate that MOF-based nanocomposites are expected to be useful SERS substrates and have a universal applicability for the detection of other hazardous molecules.