A Cooperative Effect of Bifunctionalized Nanoparticles on Recognition: Sensing Alkali Ions by Crown and Carboxylate Moieties in Aqueous Media
作者:Shu-Yi Lin、Chun-hsien Chen、Meng-Chieh Lin、Hsiu-Fu Hsu
DOI:10.1021/ac050443r
日期:2005.8.1
Reported here is a cooperative effect that the sensing efficiency of the active group on gold nanoparticles (GNPs) can be significantly influenced by another proximal functional group. We previously developed a visual sensing scheme for K+ by 15-crown-5-CH2O(CH2)12SH functionalized GNPs in aqueous matrix. Upon adding K+, the GNP solution changes from red to blue. Such a transform is triggered by a 2-to-1 sandwich complexation of crown to K+, resulting in the red shift of surface plasmon absorption due to GNP aggregation. Herein, we discover that introducing a second functionality, thioctic acid (TA), onto GNPs significantly affects the sensing efficiency of crown moieties (15-crown-5-CH2O(CH2)nSH and 12-crown-4-CH2O(CH2)nSH, where n = 4, 8, and 12). The rate constant of K+ recognition by TA- and 15-crown-5-CH2O(CH2)4S-bifunctionalized GNPs is more than 4 orders of magnitude faster than the others containing longer methylene chains. The same chain-length dependence is also found in the case of Na+ sensing by 12-crown-4 functionalized GNPs. The discrepancy in sensing performance is attributed to a cooperative effect that the negatively charged carboxylate of TA may preorganize the crown moiety for K+ recognition. This method is applied to measure K+ and Na+ in human urine by UV−visible spectrometry. By adjusting the concentrations of GNPs, the dynamic ranges tuned for K+ and Na+ are, respectively, 6.25 μM−1.12 mM and 0.156−4.00 mM, suitable for real samples pretreated simply by 10-fold dilution. The results ([K+] = 20.3 mM, [Na+] = 45.1 mM) agree with those obtained from ICP-AES ([K+] = 19.8 mM, [Na+] = 43.8 mM).
本文报道了一种协同效应,即金纳米粒子(GNPs)活性组分的传感效率可以显著受到另一个邻近功能基团的影响。我们之前开发了一种通过15-冠-5-CH2O(CH2)12SH功能化的GNPs在水相中对K+的可视化传感方案。加入K+后,GNP溶液从红色变为蓝色。这种转变是由冠醚与K+形成2比1的夹心配合物引发的,导致由于GNP聚集而引起的表面等离子体吸收红移。在此,我们发现将第二种功能基团硫辛酸(TA)引入GNPs会显著影响冠醚部分的传感效率(15-冠-5-CH2O(CH2)nSH和12-冠-4-CH2O(CH2)nSH,其中n = 4、8和12)。TA和15-冠-5-CH2O(CH2)4S双功能化GNPs对K+识别的速率常数比含有较长亚甲基链的其他纳米粒子快4个数量级以上。在12-冠-4功能化的GNPs对Na+的传感中也发现了相同的长链依赖性。传感性能的差异归因于一种协同效应,即TA的负电性羧酸盐可能预组织冠醚部分以进行K+识别。这种方法通过紫外−可见光谱法应用于测量人尿中的K+和Na+。通过调整GNPs的浓度,K+和Na+的动态范围分别调整为6.25 μM−1.12 mM和0.156−4.00 mM,适用于通过简单地10倍稀释预处理的实际样品。结果([K+] = 20.3 mM,[Na+] = 45.1 mM)与电感耦合等离子体−原子发射光谱法获得的结果([K+] = 19.8 mM,[Na+] = 43.8 mM)一致。