Revisiting the Polyol Synthesis and Plasmonic Properties of Silver Nanocubes

Abstract

Background: Noble-metal nanocrystals have been extensively studied over the past decades because of their unique optical properties. The polyol process is considered an effective method for silver (Ag) nanocrystals’ synthesis in solution even though the reproducibility of its shape controlling is still a challenge. Here, Ag nanowires and nanocubes were synthesized by the polyol process, in which the Ag+ ions are directly reduced by ethylene glycol with a certain amount of Cl− ions added. We present the relationship between the final morphology of the Ag nanostructures with the parameters of reaction, including temperature, growth time, injection rate, and the amount of sodium chloride. The as-synthesized nanowires and nanocubes were characterized by scanning electron microscopy, transmission electron microscopy and X-ray diffraction. The uniformly distributed nanocubes with a mean edge length of 140 nm were obtained. The localized surface plasmon resonance of Ag nanocubes was characterized by laser scanning fluorescence confocal microscopy. The photoluminescence enhancement was observed on the perovskite film coupled with Ag nanocubes. Objective: We aimed to synthesize uniform and controllable silver nanocubes and nanowires through the polyol process and explore the interaction between CsPbBr3 perovskite film and Ag nanocubes antennas. Methods: We synthesized silver nanocubes and nanowires through the polyol process where the silver nitrate (AgNO3) was reduced by Ethylene Glycol (EG) in the presence of a blocking agent polyvinylpyrrolidone (PVP). Results: We successfully synthesized Ag nanocubes with an average edge length of 140 nm and Ag nanowires with a uniform distribution in terms of both shape and size through a polyol process with sodium chloride (NaCl) as the additive. In addition, the local photoluminescence (PL) enhancement was observed in a perovskite film by combining Ag nanocubes, which is attributed to the antennas plasmonic effect of the Ag nanocubes. Conclusion: In summary we studied the parameters in the polyol process such as reaction temperature, growth time, injection rate, kind of halide ion and NaCl amount for the synthesis of Ag nanowires and nanocubes. Our results suggest that the concentration of Cl- and the growth time have the main influence on Ag nanowires and nanocubes formation. The optimum growth time was found to be 60 min and 120 min for the formation of Ag nanowires and nanocubes, respectively. In addition, we revealed that the opportune reaction temperature of Ag nanowires was 140 °C. The injection rate of precursors was also found to play an important role in the final morphology of Ag nanowires and nanocubes. In addition, for the generation of Ag nanocubes, the presence of Cl− ion in the reaction is critical, which can eliminate most of the byproducts. We obtained the Ag nanowires with a uniform distribution in terms of both shape and size, and nanocubes with average lengths of 140 nm by the polyol process with the optimal parameters. Plasmon-coupled emission induced by noble-metal nanocrystals has attracted more attention in recent years. In this work, the PL of a perovskite film was enhanced by the coupling of Ag nanocubes due to the surface plasmonic effect.