Porous carbon film/WO3-x nanosheets based SERS substrate combined with deep learning technique for molecule detection.

The Surface-enhanced Raman scattering (SERS) is an attractive optical detecting method with high sensitivity and detectivity, however challenges on large-area signal uniformity and complex spectra analysis methods always retards its wide application. Herein, a highly sensitive and uniform SERS detection strategy supported by porous carbon film/WO3-x nanosheets (PorC/WO3-x) based noble-metal-free SERS substrate and deep learning algorithm are reported. Experimentally, the PorC/WO3-x substrate was prepared by high-temperature annealing the PorC/WO3 films under the argon atmosphere. The defect density of the WO3 was controlled by tuning the reducing reaction time during the annealing process. The SERS performance was evaluated by using R6G as the Raman reporter, it showed that the SERS intensity obtained on the substrate with the optimal annealing time of 3 h was about 8 times as high as that obtained on the PorC/WO3 substrate without annealing treatment. And detection limit of 10-7 M and Raman enhancement factor of 106 could be achieved. Moreover, the above optimal SERS substrate was utilized to detect flavonoids of quercetin, 3-hydroxyflavone and flavone, and a deep learning algorithms was incorporated to identify the quercetin. It revealed that quercetin can be accurately detected within the above flavonoids, and lowest detectable concentration of 10-5 M can be achieved.

A hybrid SERS sensing platform constructed by porous carbon/Ag nanoparticles for efficient imatinib detection in bio-environment.

Surface enhanced Raman scattering (SERS) is a rapid and non-destructive spectral detection technique, and has been widely implemented on trace-level molecule detection. In this work, a hybrid SERS substrate constructed by porous carbon film and silver nanoparticles (PCs/Ag NPs) was developed and then used for imatinib (IMT) detection in bio-environment. The PCs/Ag NPs was prepared by direct carbonizing the gelatin-AgNO3 film in the air atmosphere, and an enhancement factor (EF) of 106 was achieved with R6G as the Raman reporter. Hereafter, this SERS substrate was used as the label-free sensing platform to detect the IMT in the serum, and the experimental results indicate that the substrate is conducive to eliminating the interference from the complex biological molecules in the serum, and the characteristic Raman peaks belonging to IMT (10-4 M) are accurately resolved. Furthermore, the SERS substrate was used to trace the IMT in the whole blood, the trace of ultra-low concertation of IMT is rapidly discovered without any pretreatment. Thus, this work finally suggests that the proposed sensing platform provides a rapid and reliable method for IMT detection in the bio-environment and offers a potential for its application in therapeutic drug monitoring.

Constructing the Mo2C@MoOx Heterostructure for Improved SERS Application.

Surface-enhanced Raman scattering (SERS) is a non-destructive spectra analysis technique. It has the virtues of high detectivity and sensitivity, and has been extensively studied for low-trace molecule detection. Presently, a non-noble-metal-based SERS substrate with excellent enhancement capabilities and environmental stability is available for performing advanced biomolecule detection. Herein, a type of molybdenum carbide/molybdenum oxide (Mo2C@MoOx) heterostructure is constructed, and attractive SERS performance is achieved through the promotion of the charge transfer. Experimentally, Mo2C was first prepared by calcinating the ammonium molybdate tetrahydrate and gelatin mixture in an argon atmosphere. Then, the obtained Mo2C was further annealed in the air to obtain the Mo2C@MoOx heterostructure. The SERS performance was evaluated by using a 532 nm laser as an excitation source and a rhodamine 6G (R6G) molecule as the Raman reporter. This process demonstrates that attractive SERS performance with a Raman enhancement factor (EF) of 1.445 × 108 (R6G@10-8 M) and a limit of detection of 10-8 M can be achieved. Furthermore, the mechanism of SERS performance improvement with the Mo2C@MoOx is also investigated. HRTEM detection and XPS spectra reveal that part of the Mo2C is oxidized into MoOx during the air-annealing process, and generates metal-semiconductor mixing energy bands in the heterojunction. Under the Raman laser irradiation, considerable hole-electron pairs are generated in the heterojunction, and then the hot electrons move towards MoOx and subsequently transfer to the molecules, which ultimately boosts the Raman signal intensity.