Dutta Kaku, Deka Ramesh C, Das Diganta Kumar
Department of Chemistry, Gauhati University, Guwahati 781014, Assam, India.
Department of Chemical Science, Tezpur University, Napaam, Tezpur 784 028, Assam, India.
Spectrochim Acta A Mol Biomol Spectrosc. 2014 Apr 24;124:124-9. doi: 10.1016/j.saa.2013.12.090. Epub 2014 Jan 4.
Single molecule acting as both fluorescent and electrochemical sensor for Zn(2+) ion is rare. The product (L) obtained on condensation between benzil and L-tryptophan has been characterized by H NMR, ESI-MS and FT-IR spectroscopy. L in 1:1 (v/v) CH3OH:H2O solution shows fluorescence emission in the range 300 nm to 600 nm with λmax at 350 nm when is excited with 295 nm photon. Zn(2+) ion could induce a 10-fold enhancement in fluorescent intensity of L. Fluorescence and UV/Visible spectral data analysis shows that the binding ratio between Zn(2+) ion and L is 1:1 with log β=4.55. Binding of Zn(2+) ion disrupts the photoinduced electron transfer (PET) process in L and causes the fluorescence intensity enhancement. When cyclic voltammogram is recorded for L in 1:1 (v/v) CH3OH:H2O using glassy carbon (GC) electrode, two quasi reversible redox couples at redox potential values -0.630±0.005 V and -1.007±0.005 V are obtained (Ag-AgCl as reference, scan rate 0.1 V s(-1)). Interaction with Zn(2+) ion makes the first redox couple irreversible while the second couple undergoes a 0.089 V positive shift in redox potential. Metal ions - Cd(2+), Cu(2+), Co(2+), Hg(2+), Ag(+), Ni(2+), Fe(2+), Mn(2+), Mg(2+), Ca(2+)and Pb(2+), individually or all together, has no effect on the fluorescent as well as electrochemical property of L. DFT calculations showed that Zn(2+) ion binds to L to form a stable complex. The detection limit for both fluorescence as well as electrochemical detection was 10(-6) M.
单分子同时作为Zn(2+)离子的荧光和电化学传感器的情况较为罕见。苯偶酰与L-色氨酸缩合得到的产物（L）已通过1H NMR、ESI-MS和FT-IR光谱进行了表征。L在1:1（v/v）的CH3OH:H2O溶液中，当用295 nm光子激发时，在300 nm至600 nm范围内有荧光发射，λmax为350 nm。Zn(2+)离子可使L的荧光强度增强10倍。荧光和紫外/可见光谱数据分析表明，Zn(2+)离子与L的结合比为1:1，log β = 4.55。Zn(2+)离子的结合破坏了L中的光致电子转移（PET）过程，导致荧光强度增强。当使用玻碳（GC）电极在1:1（v/v）的CH3OH:H2O中记录L的循环伏安图时，得到了两个准可逆氧化还原对，氧化还原电位值分别为-0.630±0.005 V和-1.007±0.005 V（以Ag-AgCl为参比，扫描速率0.1 V s(-1)）。与Zn(2+)离子的相互作用使第一个氧化还原对不可逆，而第二个氧化还原对的氧化还原电位正向移动了0.089 V。金属离子 - Cd(2+)、Cu(2+)、Co(2+)、Hg(2+)、Ag(+)、Ni(2+)、Fe(2+)、Mn(2+)、Mg(2+)、Ca(2+)和Pb(2+)，单独或全部一起，对L的荧光以及电化学性质均无影响。DFT计算表明，Zn(2+)离子与L结合形成稳定的配合物。荧光以及电化学检测的检测限均为10(-6) M。
