Vanadium dioxide nanostructures with remarkable surface-enhanced Raman scattering activity.

Structure and size control are always considered to be effective routes to enhance the sensitivity of materials. Herein, rough VO2 (D) nanostars and nanospheres with highly dense and rough surfaces were synthesized. Accompanied by the properties inherited from the rough VO2 nanospheres, i.e., high adsorption and strong plasma resonance, these VO2 (D) nanospheres exhibit highly sensitive activity as a surface enhanced Raman spectrum substrate. The detection limit of Rhodamine 6G on this semiconductor SERS substrate is as low as 10-9 M.

General molten-salt route to three-dimensional porous transition metal nitrides as sensitive and stable Raman substrates.

Transition metal nitrides have been widely studied due to their high electrical conductivity and excellent chemical stability. However, their preparation traditionally requires harsh conditions because of the ultrahigh activation energy barrier they need to cross in nucleation. Herein, we report three-dimensional porous VN, MoN, WN, and TiN with high surface area and porosity that are prepared by a general and mild molten-salt route. Trace water is found to be a key factor for the formation of these porous transition metal nitrides. The porous transition metal nitrides show hydrophobic surface and can adsorb a series of organic compounds with high capacity. Among them, the porous VN shows strong surface plasmon resonance, high conductivity, and a remarkable photothermal conversion efficiency. As a new type of corrosion- and radiation-resistant surface-enhanced Raman scattering substrate, the porous VN exhibits an ultrasensitive detection limit of 10-11 M for polychlorophenol.

Highly Sensitive W18O49 Mesocrystal Raman Scattering Substrate with Large-Area Signal Uniformity.

Although mesocrystals with ordered building units have great potential in many fields because of the large amount of organic molecules used as structure-directing agents during their synthesis process, severe matrix interference makes their surface-enhanced Raman scattering (SERS) properties rarely understood. Herein, a rapid (20 s) and green microwave synthetic route is developed for the 100 g scale preparation of plasmonic W18O49 mesocrystals with no additives. The ultrathin (1.5 nm) and oxygen vacancy-rich W18O49 nanowires as a building unit greatly improve the interface charge transfer, while the periodic mesocrystal structure significantly enhances the localized surface plasmon resonance effect and creates high-density electromagnetic hot spots among the nanowires. An outstanding enhancement factor of 1.2 × 107 and an ultralow detectable limit of 10-11 M are achieved, and the single-molecule imaging is also realized on this mesocrystal-based SERS substrate. Moreover, the relative standard deviation of the fabricated large-area (2.2 cm2) SERS substrate is only 6.8%.

Low temperature synthesis of plasmonic molybdenum nitride nanosheets for surface enhanced Raman scattering.

Molybdenum nitride (δ-MoN) is an important functional material due to its impressive catalytic, energy storage, and superconducting properties. However, the synthesis of δ-MoN usually requires extremely harsh conditions; thus, the insight into δ-MoN is far behind that of oxides and sulfides of molybdenum. Herein, we report that ultrathin δ-MoN nanosheets are prepared at 270 °C and 12 atm. WN, VN, and TiN nanosheets are also synthesized by this method. The δ-MoN nanosheets show strong surface plasmon resonance, high conductivity, excellent thermal and chemical stability as well as a high photothermal conversion efficiency of 61.1%. As a promising surface enhanced Raman scattering substrate, the δ-MoN nanosheets exhibit a 8.16 × 106 enhanced factor and a 10-10 level detection limit for polychlorophenol.