Chiral Sensing of Glucose Using Porous Pt-Modified Electrodes Exposing Pt High-Index Planes
Authors: Matsuzawa Takuya , Matsunaga Mariko 
Published: February 2020

The discrimination and detection of chiral molecules, or chiral sensing, is an extremely important technique in organic chemistry, pharmacology and living body-related sciences. Earlier studies have shown that high-index surfaces of metals possess chirality in its atomic arrangements, and that the surfaces are able to discriminate chirality of various organic molecules. Recently, we reported the enantioselectivity of porous platinum electrode with a large number of atomic steps bearing high-index surfaces, for the redox reaction process of 3, 4-dihydroxyphenyl alanine, glucose, and so on (1). However, for medical diagnosis, the chiral sensor is expected to develop to detect target molecules in a wider concentration range. In this study, we performed chiral sensing using various types of porous platinum-modified electrodes to develop the sensitivity of sensing. And, the dependence of concentration of glucose on the sensing signal, or the peak current density in cyclic voltammogram, was investigated to evaluate the performance for the chiral sensing. As electrodes with high-index surfaces, a porous platinum electrode, a platinum black-modified electrode, porous platinum particles-modified electrodes were investigated. Porous platinum electrode was prepared by electrodeposition from the plating bath including a surfactant Brij58(2), and porous platinum particles was prepared using chemical synthesis method(3). The detail preparation methods will be explained at the presentation. The chiral discrimination was investigated by cyclic voltammetry in the acidic glucose solution. Cyclic voltammetry was performed using the three-electrode cell: Ag/AgCl electrode as the reference electrode, platinum wire as the counter electrode and the various electrodes as working electrodes.
We succeeded in discriminating chirality of glucose with all electrodes. The relation between the glucose concentration and the peak current density at around 0.35 V vs Ag/AgCl is shown in Figure. Here, the weight of Pt is standardized to be about 6.8×10-4g for all the samples. For all electrodes, as the glucose concentration increases, the peak current density increase, and the tendency emerged most conspicuously for L-form. In addition, the difference of the peak current densities between L- and D-form become the largest for a porous platinum particles-modified electrode. This is considered to be mainly due to the large specific surface area of high-index surfaces of the electrode. The detail examination and the detection limit of the concentration will be discussed at the presentation.
1　"Chiral Discrimination of 3,4-Dihydroxyphenylalanine by Electrodes Modified with Mesoporous Pt Film with a Large Number of Atomic Steps," Mariko Matsunaga, Kaji Kohei, 64th Annual Meeting of the International Society of Electrochemistry, Santiago de Queretaro, Mexico, Sep. 2013.
2 “Synthesis of Mesoporous Pt Films with Tunable Pore Sizes from Aqueous Surfactant Solutions,” H. J. Wang, L. Wang, T. Sato, Y. Sakamoto, S. Tominaka, K. Miyasaka, N. Miyamto, Y. Nemoto, O. Terasaki and Y. Yamauchi, Chem. Mater., 2012, 24, 1591.
3　“Multimetallic Mesoporous Spheres Through Surfactant-Directed Synthesis,” B. Jiang, C. L. Li, M. Imura, J. Tang and Y. Yamauchi, Adv Sci, 2015, 2.

Figure 1