Gold nanomaterial (GNM)-based colorimetric sensors have gained particular attention in the analytical field because of their instrument-free, low-cost, and easy-to-use features. Herein, a universal strategy for improving the sensitivity of colorimetric assays, which is based on GNM etching, was proposed by using additives to shift the chemical equilibrium of the reactions. As a proof-of-concept demonstration, nitrite was detected with high sensitivity using gold nanorod (AuNR) by monitoring the shift of its longitudinal localized surface plasmonic resonance (Δλ) with the use of NH₄Br and HCl. These two additives could change chemical equilibriums and promote the etching of more gold atoms at the AuNR ends. The assay is sensitive and 0.001 μM of nitrite could result in Δλ change by 3 nm. A linear relationship between Δλ and nitrite concentration was established (Δλ =22.8∗C_nitrite +9.7) in the range of 0.016–8.0 μM with a coefficient of 0.999. The reaction time was also accurately controlled by adjusting solution pH with NH₃⋅H₂O to terminate the test. The sensitivity of this colorimetric assay toward nitrite was significantly higher than that of the conventional Griess assay, while it was the highest among the reported GNM-based approaches. This method was successfully applied in determining the nitrite content in food samples, including waters, spinach, and rose petals, with less rigorous sample processing. The proposed strategy of using additives to alter chemical equilibriums to improve sensitivity could be extended to other GNM etching sensors.

基于金纳米材料（GNM）的比色传感器因其无仪器，低成本和易于使用的特性而在分析领域得到了特别的关注。在本文中，提出了一种通过使用添加剂来改变反应的化学平衡的，基于GNM蚀刻的提高比色测定灵敏度的通用策略。作为概念验证，使用金纳米棒（AuNR）通过使用NH ₄监测其纵向局部表面等离子体共振（Δλ）的位移，以高灵敏度检测亚硝酸盐。Br和HCl。这两种添加剂可以改变化学平衡并促进在AuNR末端蚀刻更多的金原子。该测定法灵敏，0.001μM的亚硝酸盐可能导致Δλ变化3 nm。在0.016–8.0μM范围内建立了Δλ与亚硝酸盐浓度之间的线性关系（Δλ= 22.8 * C_亚硝酸盐+9.7），系数为0.999。反应时间也准确地通过调节溶液的pH用NH受控₃ ⋅H ₂O终止测试。该比色测定法对亚硝酸盐的敏感性显着高于常规Griess测定法，同时在已报道的基于GNM的方法中灵敏度最高。该方法成功地用于测定食品样品（包括水，菠菜和玫瑰花瓣）中的亚硝酸盐含量，而样品处理的严格程度较低。所提出的使用添加剂改变化学平衡以提高灵敏度的策略可以扩展到其他GNM蚀刻传感器。