Explosive vapour/particles detection using SERS substrates and a hand-held Raman detector

Plasmonic nanoparticle sensors: current progress, challenges, and future prospects

Plasmonic nanoparticles (NPs) have played a significant role in the evolution of modern nanoscience and nanotechnology in terms of colloidal synthesis, general understanding of nanocrystal growth mechanisms, and their impact in a wide range of applications. They exhibit strong visible colors due to localized surface plasmon resonance (LSPR) that depends on their size, shape, composition, and the surrounding dielectric environment. Under resonant excitation, the LSPR of plasmonic NPs leads to a strong field enhancement near their surfaces and thus enhances various light-matter interactions. These unique optical properties of plasmonic NPs have been used to design chemical and biological sensors. Over the last few decades, colloidal plasmonic NPs have been greatly exploited in sensing applications through LSPR shifts (colorimetry), surface-enhanced Raman scattering, surface-enhanced fluorescence, and chiroptical activity. Although colloidal plasmonic NPs have emerged at the forefront of nanobiosensors, there are still several important challenges to be addressed for the realization of plasmonic NP-based sensor kits for routine use in daily life. In this comprehensive review, researchers of different disciplines (colloidal and analytical chemistry, biology, physics, and medicine) have joined together to summarize the past, present, and future of plasmonic NP-based sensors in terms of different sensing platforms, understanding of the sensing mechanisms, different chemical and biological analytes, and the expected future technologies. This review is expected to guide the researchers currently working in this field and inspire future generations of scientists to join this compelling research field and its branches.

Selective SERS Detection of TATB Explosives Based on Hydroxy-Terminal Nanodiamond-Multilayer Graphene Substrate

Selective surface-enhanced Raman scattering (SERS) detection of target explosives with good reproducibility is very important for monitoring soldiers' health and ecological environment. Here, the specific charge transfer pathway was constructed between a stable nanodiamond-multilayer graphene (MGD) film substrate and the target explosives. Two-step wet chemical oxidation methods of H2O2 (30%) and HNO3 (65%) solutions were used to regulate the terminal structure of MGD films. The experimental results showed that the hydroxyl (-OH) functional groups are successfully modified on the surface of MGD thin films, and the MGD-OH substrates having good selectivity for 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) explosive in mixed solutions of the TATB, 2,2-dinitroethene-1,1-diamine, 2,4,6-trinitrotoluene, and 1,3,5-trinitroperhydro-1,3,5-triazine explosives compared with MGD substrates were demonstrated. Finally, first-principles density functional theory simulations revealed that the SERS enhancement of the MGD-OH substrate is mainly attributed to the transferred electrons between the -NO2 groups of TATB and the -OH groups of the MGD-OH substrate.

Vapor phase detection of explosives by surface enhanced Raman scattering under ambient conditions with metal nanogap structures

Non-invasive and passive detection of explosives in the vapor phase is advantageous for military, counter-terrorism, and homeland security applications. Detection of explosives using SERS has been an active research topic. However, the vapor pressures of most explosives are low at room temperature, and consequently, the vapor phase detection by SERS is highly challenging without intentionally heating explosive powder to increase the vapor pressure. In this work, we report the rapid and sensitive detection of 2,4,6-trinitrotoluene (TNT) and 2,4-dinitrotoluene (2,4-DNT) in the vapor phase, using a gold nanogap (AuNG) SERS substrate. The AuNG SERS substrate was fabricated with electron beam evaporation, rapid thermal annealing, and wet etching. SERS measurements were carried out with an incident power as low as 0.56 mW at 785 nm. To prevent the condensation effect, the TNT and 2,4-DNT powders inside the cuvette were taken out before inserting the nanogap substrate. Our SERS results demonstrate the feasibility of the non-invasive detection of vapor phase explosives under ambient conditions.

Novel exploration of Raman microscopy and non-linear optical imaging in adenomyosis

Background

Adenomyosis is a common gynecological disease in women. A relevant literature search found that approximately 82% of patients with adenomyosis chose to undergo hysterectomy. However, women of childbearing age are more likely to undergo surgery to preserve the uterus. Because it is difficult to determine the extent of adenomyosis, it is almost impossible to resect adenomyotic tissue and retain the uterus at the same time.

Materials and methods

Following ethics approval and patient consent, tissue samples were resected and prepared to create frozen slices for analysis. One slice was subjected to H&E staining while the remaining slices were photographed with Coherent Anti-Stokes Raman Scattering (CARS), Second-Harmonic Generation (SHG) microscopy, and Raman spectroscopy. Comparative observations and analyses at the same positions were carried out to explore the diagnostic ability of CARS, SHG, and Raman spectroscopy for adenomyosis.

Results

In adenomyotic tissue, we found two characteristic peaks at 1,155 and 1,519 cm^–1 in the Raman spectrum, which were significantly different from normal tissue. The substances shown in the CARS spectrum were represented by peaks of 1,519 cm^–1. SHG microscopy showed a distribution of collagen at the focus of the adenomyosis.

Conclusion

This study represents a novel analysis of Raman microscopy, CARS, and SHG in the analysis of adenomyotic lesions. We found the diffraction spectrum useful in determining the focal boundary and the diagnosis of adenomyosis in the tested samples.