Highly stable poly(N-vinyl-2-pyrrolidone) (PVP) protected copper nanoparticles were prepared using a simple chemical reduction route in different solvents {N, N-dimethyl formamide (DMF) and formamide (FA)} under aerated condition. The particles were characterized using TEM, SEM, XRD, and UV−visible spectroscopic techniques. Copper nanostructures of varying shapes and sizes were obtained using hydrazine hydrate as the reducing agent in both DMF and FA. However, reducing by ascorbic acid in FA leads to formation of mostly spherical copper nanoparticles with a narrow size distribution. The Cu nanoparticles serve as effective catalyst for 1,3-dipolar cycloaddition reactions between terminal alkynes and azides to synthesize 1,2,3-triazoles in excellent yields under mild reaction conditions. The nanocatalysts can be recycled and reused several times without significant loss of their catalytic activity.

FTIR, Raman, and surface-enhanced Raman scattering (SERS) of methimazole (MMI) have been investigated. MMI is an important antithyroid drug that inhibits the formation of thyroid hormone. It is widely used clinically in the treatment of hyperthyroidism, and thus it is useful to study its surface adsorption characteristics. The experimental FTIR and Raman data are supported with DFT calculations using B3LYP functional with LANL2DZ basis set. This is the first report on the vibrational analysis of the thiol and thione forms of MMI and their various possible silver complexes. pH-dependent normal Raman spectra have been recorded, which show the abundance of the thione form of MMI in acidic, neutral, and alkaline media. From the SERS spectra as well as theoretical calculations, it has been inferred that in neutral and alkaline media, the thiol form of MMI is chemisorbed to the silver surface through the ring N atom of the imidazole ring with an edge-on orientation and the imidazole ring lying in the plane of the silver surface. In contrast, it has been concluded that in the acidic medium, the thione form of MMI gets adsorbed to the silver surface. Thus, the pH-dependent SERS spectra have shown the preferential existence of thione and thiol tautomeric forms on the silver surface in acidic, neutral, and alkaline media.

The reduction of silver ions in formamide is shown to take place spontaneously at room temperature without addition of any reductant. The growth of Ag particles was found to be dependent on Ag+ ion concentration. In the absence of any stabilizer, deposition of silver film on the glass walls of the container takes place. However, in the presence of poly(N-vinyl-2-pyrrolidone) (PVP) or colloidal silica (SiO2), which are capable of stabilizing silver nanoparticles by complexing and providing support, a clear dispersion was obtained. The formation of the silver nanoparticles under different conditions was investigated through UV-visible absorption spectrophotometry, gas chromatography, and also electron and atomic force microscopic techniques. Atomic force microscopy results for silver films prepared in the absence of any stabilizer showed the formation of polygonal particles with sizes around 100 nm. Transmission electron microscopy results showed that the prepared silver particles in the presence of PVP were around 20 nm. The Ag nanoparticles get oxidized in the presence of chloroform and toluene. Surface modification of silver film was done in the presence of the tetrasodium salt of ethylenediaminetetraaceticacid (Na4EDTA). It was shown that the reactivity of the silver film increased in its presence. The Fermi potential of silver particles in the presence of Na4EDTA seems to lie between -0.33 and -0.446 V vs NHE.

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