In this study, gold nanoparticles were supported at graphene derivatives (AuNPs@GDs) from chloroauric acid and graphene oxide (GO) by using sodium citrate, L-ascorbic acid, and 4-(2-hydroxyethyl)-1-piperazineethane-sulfonic acid (HEPES) as green reductants to evaluate the catalytic activity in the 4-nitrophenol (4-NP) reduction system. Among the three reductants, HEPES which derived AuNP@GD (3) exhibited up to 8.44-fold higher catalytic activity compared with sodium citrate and L-ascorbic acid. To evaluate the influence of mass ratio between Au and GO on the catalytic activity, we controlled adding amounts of chloroauric acid while the other conditions using HEPES were fixed. Notably, decreasing the mass ratio of Au/GO from 0.59 to 0.10 increased the rate constant in the range of 7.6 × 10−3 to 16.1 × 10−3/s. However, when the turnover frequency (TOF) was considered, the maximum value was obtained when Au/GO was 0.39. It can be concluded that AuNPs@GD (4) synthesized using HEPES significantly improved the catalytic activity in both rate constant (10.4 × 10−3/s) and TOF (8.08 × 10−5 mol/g·s) in 4-NP reduction. These results suggest that the type of reductants used to synthesize AuNPs@GDs is a significant factor on the catalytic activity and that GO can help increase the catalytic activity, but has an effective ratio with Au.

中文翻译：

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使用绿色还原剂合成负载在石墨烯衍生物上的金纳米粒子及其在 4-硝基苯酚还原中的催化活性

在这项研究中，通过使用柠檬酸钠、L-抗坏血酸和 4-(2-羟乙基)-1-哌嗪乙磺酸，金纳米颗粒负载在氯金酸和氧化石墨烯 (GO) 的石墨烯衍生物 (AuNPs@GDs) 上(HEPES) 作为绿色还原剂来评估 4-硝基苯酚 (4-NP) 还原系统中的催化活性。在三种还原剂中，与柠檬酸钠和 L-抗坏血酸相比，衍生出 AuNP@GD (3) 的 HEPES 表现出高达 8.44 倍的催化活性。为了评估 Au 和 GO 质量比对催化活性的影响，我们控制了氯金酸的添加量，而使用 HEPES 的其他条件是固定的。值得注意的是，将 Au/GO 的质量比从 0.59 降低到 0.10 会使速率常数增加到 7.6 × 10-3 到 16.1 × 10-3/s 的范围内。然而，当考虑周转频率（TOF）时，Au/GO 为 0.39 时获得最大值。可以得出结论，使用 HEPES 合成的 AuNPs@GD(4) 显着提高了 4-NP 的速率常数 (10.4 × 10−3/s) 和 TOF (8.08 × 10−5 mol/g·s) 的催化活性减少。这些结果表明，用于合成 AuNPs@GDs 的还原剂类型是影响催化活性的重要因素，GO 可以帮助提高催化活性，但与 Au 有有效比。