Room Temperature Synthesis and Catalytic Properties of Surfactant-Modified Ag Nanoparticles

Well-dispersed Ag nanoparticles with size of 20–30？nm were synthesized in water at room temperature with a self-made novel imidazoline Gemini surfactant quaternary ammonium salt of di (2-heptadecyl-1-formyl aminoethyl imidazoline) hexanediamine. Transmission electron microscopy, X-ray powder diffraction, ultraviolet-visible absorption spectra, and Fourier transform infrared ray were used to characterize the Ag nanoparticles. Results showed that the micellized aggregation of imidazoline Gemini surfactant in water, the growth of Ag initial particles, and the interaction (adsorption and coordination) between surfactant and Ag+/Ag nanoparticles took place simultaneously to form the well-dispersed Ag nanoparticles. Catalytic results show that the surface-modified Ag product was an active metal catalyst for methyl orange reduction reaction due to the effective adsorption between Ag nanoparticles and methyl orange molecules, which was of promising application in environmental protection. 1. Introduction In recent years, metal nanoparticles have been studied extensively due to their noticeable electrical, optical, and catalytic properties [1–4]. As one of the traditional noble metals, Ag nanoparticles have been synthesized for various applications, such as biomedical antibacterial materials [5, 6], catalysis [1, 7, 8], tribology [9], and surface-enhanced Raman scattering (SERS) [10–12]. Different methods have been employed to prepare Ag nanoparticles with various morphologies, such as single-source precursor heat treatment at 550°C for synthesizing Ag nanoparticles [13], microwave-assisted route for Ag nanorods [14] and nanowires [15], microwave-solvothermal synthesis for monodispersed Ag nanoparticles [16], and solvothermal synthesis of chainlike and dendritic Ag nanostructures [17]. Other methods such as photochemical γ-ray reduction [18], ultraviolet [19], sonochemical [20], and ultrasonic synthesis [21], and so forth have also been exploited recently. However, most of these methods are concerning high-temperature treatment, complicated processing procedures, and exposure to sound or light danger. Thus, exploitation of a facile, energy-efficient, and safe route still remains a challenge. Room temperature synthesis routes for the fabrication of Ag nanoparticles have been investigated recently, showing promising application feasibility and reliability for large-scale manufacture with energy saving and safety. Zhang et al. [5] and Huang et al. [6] prepared Ag nanoparticles at room temperature, showing excellent antibacterial properties; Li et al. [22] prepared