Multi stimuli-responsive photoluminescent nanocomposite of silver nanoclusters with hyperbranched polyethylenimine derivatives

Abstract

Silver nanoclusters (AgNCs) functionalized with hyperbranched polyethylenimines with a certain number of trimethylacetamide groups (PEI–TMA) were prepared through three steps. The influence of the preparation conditions, including the pH value in the mixture of PEI–TMA and Ag⁺ and the Ag⁺/PEI–TMA feed ratio, on the photoluminescence properties of the obtained nanocomposite of AgNCs and PEI–TMA (AgNC–PEI–TMA) was studied. The obtained AgNC–PEI–TMA nanocomposite was characterized by transmission electron microscopy, dynamic light scattering and zeta potential measurements, verifying the formation of the nanocomposite. AgNC–PEI–TMA in water was not only thermoresponsive, but also responded to other stimuli, including pH, inorganic salts, and loaded organic guest. The cloud point temperature (T_cp) of aqueous solutions of AgNC–PEI–TMA could be modulated through changing the pH, and varying the type and concentration of the inorganic salts and the loaded organic guest. The obtained AgNC–PEI–TMA nanocomposite was photoluminescent, and its maximum emission wavelength was not influenced by outside stimuli. Its emission intensity was influenced negligibly by pH, traditional salting-out anions (Cl⁻ and SO₄²⁻), and the relatively polar aspirin guest. However, the traditional salting-in I⁻ anion could quench its fluorescence a little.