Experimental study and Ab-initio calculations on the molecular structure, infrared and Raman spectral properties of dinitroimidazoles

Surface-enhanced Raman scattering of flexible cotton fiber-Ag for rapid adsorption and detection of malachite green in fish

The residual of malachite green (MG) in fish is one of the major food safety concerns for consumers. It is important to develop simple and instant analytical methods to identify MG residues in fish. We fabricated flexible cotton surface-enhanced Raman scattering substrate, which offers good flexibility, uniformity and excellent adsorption capability. The UV-vis DRS spectra, transmission electron microscopy and scanning electron elemental mapping images shown that the Ag NPs were closely packed on the surface of cotton fiber. The adsorption feature of cotton fiber could adsorb MG from solution and surface of fish. The Quick Easy Cheap Effective Rugged and Safe (QuEChERS) sample preparation method was used to adsorb MG in fish for SERS sensing. The limit of detection of MG in fish using this developed method was as low as 0.05 ppm. The QuEChERS-SERS analysis method exhibits the capability for multiplex detecting mixture of MG and Dimetridazole at different ratios (5 ppm, 1/400 and 1/4000) from fish. The results indicated that the cotton fiber-Ag composite was suitable employed as SERS substrate for simple and instant detecting trace contaminants in food.

Layer-by-Layer Assembly of Polystyrene/Ag for a Highly Reproducible SERS Substrate and Its Use for the Detection of Food Contaminants

Polystyrene (PS) spheres were prepared through an emulsifier-free emulsion polymerization method, in which the reaction time, ionic strength, concentrations of copolymer were studied in detail. The resulting PS microspheres and Ag nanoparticles were used to construct a surface enhanced Raman scattering (SERS) substrate by a layer-by-layer assembly method. A relatively uniform distribution of PS/Ag in the films was obtained, and the multilayer substrate presented excellent SERS reproducibility and a tunable enhancement effect. The SERS substrate was used for detecting harmful pesticides (malachite green and dimetridazole) in food samples, with a limit of detection as low as 3.5 ppb. The obtained plasmonic composite has a promising future in the field of SERS sensing.

Thermal stability and detonation character of nitro-substituted derivatives of imidazole

A series of nitro-imidazole derivatives were designed by replacing hydrogen atoms on imidazole ring with nitro group one by one. In order to investigate the thermodynamic stability, heat of formation (HOF), and bond dissociation energy (BDE) are calculated at the B3PW91/6-311+G(d,p) level. In order to investigate the impact sensitivity and detonation property, the drop height (H₅₀), free space per molecule in crystal lattice (ΔV), detonation velocity (D), and detonation pressure (P) are calculated by using the empirical Kamlet-Jacobs (K-J) equation. The results show that the thermal stabilities of title molecules are determined by whether nitro group is associated to 1-position or not and accompanied with the steric hindrance between nitro groups and the charge population on the carbon atoms of imidazole ring. The excellent impact sensitivity and detonation performance of title molecules are also evaluated. On the consideration both of stability and detonation characters, 2,4,5-trinitro-1H-imidazole (D = 8.98 km/s, P = 36.70 GPa) is screened out as the potential high-energy-density molecule for further research.