*Article* **Oxygen-Resistant Electrochemiluminescence System with Polyhedral Oligomeric Silsesquioxane**

#### **Ryota Nakamura, Hayato Narikiyo, Masayuki Gon, Kazuo Tanaka \* and Yoshiki Chujo**

Department of Polymer Chemistry, Graduate School of Engineering, Kyoto University, Katsura, Nishikyo-ku, Kyoto 615-8510, Japan

**\*** Correspondence: tanaka@poly.synchem.kyoto-u.ac.jp

Received: 19 June 2019; Accepted: 7 July 2019; Published: 10 July 2019

**Abstract:** We report the oxygen-resistant electrochemiluminescence (ECL) system from the polyhedral oligomeric silsesquioxane (POSS)-modified tris(2,2-bipyridyl)ruthenium(II) complex (Ru-POSS). In electrochemical measurements, including cyclic voltammetry (CV), it is shown that electric current and ECL intensity increase in the mixture system containing Ru-POSS and tripropylamine (TPrA) on the indium tin oxide (ITO) working electrode. The lower onset potential (*E*onset) in CV is observed with Ru-POSS compared to tris(2,2-bipyridyl)ruthenium(II) complex (Ru(bpy)3<sup>2</sup>+). From the series of mechanistic studies, it was shown that adsorption of Ru-POSS onto the ITO electrode enhances TPrA oxidation and subsequently the efficiency of ECL with lower voltage. Moreover, oxygen quenching of ECL was suppressed, and it is proposed that the enhancement to the production of the TPrA radical could contribute to improving oxygen resistance. Finally, the ECL-based detection for water pollutant is demonstrated without the degassing treatment. The commodity system with Ru(bpy)3<sup>2</sup>+ is not applicable in the absence of degassing with the sample solutions due to critical signal suppression, meanwhile the present system based on Ru-POSS was feasible for estimating the amount of the target even under aerobic conditions by fitting the ECL intensity to the standard curve. One of critical disadvantages of ECL can be solved by the hybrid formation with POSS.

**Keywords:** electrochemiluminescence; POSS; ruthenium(II) complex; oxygen resistance
