In this study, ultrafine silver (Ag) nanoparticles were synthesised in Orthosiphon stamineus (OS) extract via facile electrochemical method. Different pre–synthesis extraction methods, namely ultrasonic assisted extraction hydro–distillation (UAE–HD) and classical aqueous extraction (AE) were used and compared. UAE–HD attained the highest total phenolic compounds at 8563.90 mg/kg. The Ag nanoparticles prepared via pre–synthesis extraction of UAE–HD (Ag_UAE-HD) and classical AE (Ag_AE) gave ultrafine sizes of 2 nm and 15 nm, respectively. It was suggested from the characterisation results that the phenolic compounds present in the OS extract had a significant role in the capping and stabilisation of Ag nanoparticles. Moreover, it was also demonstrated that the size of the Ag nanoparticles could simply be altered by varying the amount of total phenolic content (TPC) using different pre–synthesis extraction methods prior to the synthesis of Ag. Next, the photocatalytic activity of the Ag nanoparticles was tested towards the degradation of 2, 4–dicholorophenoxyacetic acid (2,4–D) herbicide. The synthesised Ag nanoparticles also showed outstanding photocatalytic activity with maximum degradation efficiency of up to 99.78% at pH 3, 0.01 g L⁻¹ of catalyst dosage and 10 mg L⁻¹ of 2, 4-D concentration. High amount of TPC contributed to the low energy band–gap (E_g) of Ag_UAE-HD catalyst and significantly inhibited the electron-hole recombination as well as enhanced the photocatalytic activity. The figures of merit based on electric energy consumption (E_EO) indicate that less energy was consumed during the degradation of 2,4–D in the presence of Ag_UAE-HD compared with other catalysts. Therefore, it could be concluded that Ag_UAE-HD is a promising material for high photocatalytic degradation efficiency of 2,4–D under optimal condition.

在这项研究中，通过简便的电化学方法在邻位虹吸稻草（OS）提取物中合成了超细银（Ag）纳米颗粒。并比较了不同的合成前萃取方法，即超声辅助萃取水蒸馏（UAE–HD）和经典水萃取（AE）。阿联酋–HD的酚类化合物总量最高，为8563.90 mg / kg。通过预先合成的UAE-HD（Ag _UAE-HD）和经典AE（Ag _AE）制备的Ag纳米颗粒）分别产生2 nm和15 nm的超细尺寸。从表征结果表明，OS提取物中存在的酚类化合物在Ag纳米颗粒的封端和稳定中起着重要作用。此外，还表明，在合成Ag之前，可以使用不同的预合成萃取方法，通过改变总酚含量（TPC）的数量，简单地改变Ag纳米粒子的大小。接下来，测试了Ag纳米粒子对2，4-二氯苯氧苯乙酸（2,4-D）除草剂降解的光催化活性。合成的Ag纳米颗粒还表现出出色的光催化活性，在pH 3、0.01 g L ^-1的催化剂用量和10 mg L ^-1的最大降解效率下高达99.78％。2，4-D浓度。大量的TPC导致Ag _UAE-HD催化剂的低能带隙（E _g），并显着抑制了电子-空穴复合并增强了光催化活性。基于电能消耗（E _EO）的品质因数表明，与其他催化剂相比，在Ag _UAE-HD存在下，在2,4--D降解过程中消耗的能量更少。因此，可以得出结论，Ag _UAE-HD是在最佳条件下具有较高的光催化降解2,4–D效率的有前途的材料。