Electrochimica Acta 85 (2012) 256–262 Contents lists available at SciVerse ScienceDirect Electrochimica Acta jou rn al h om epa ge: www.elsevier.com/locate/electacta Porous nickel oxide microflowers synthesized by calcination of coordination microflowers and their applications as glutathione electrochemical sensor and supercapacitors Huan Pang a,b,c,∗ , Yunfeng Shi a , Jimin Du a , Yahui Ma a , Guochang Li a , Jing Chen a , Jiangshan Zhang a , Honghe Zheng b,∗ , Baiqing Yuan a,∗ a College of Chemistry and Chemical Engineering, Anyang Normal University, Anyang, 455000, Henan, PR China b School of Energy, Soochow University, Suzhou, 215006, Jiangsu, PR China c State Key Laboratory of Coordination Chemistry, Nanjing University, Nanjing, 210093, Jiangsu, PR China a r t i c l e i n f o Article history: Received 26 June 2012 Received in revised form 10 August 2012 Accepted 15 August 2012 Available online 23 August 2012 Keywords: Porous NiO microflowers Glutathione electrochemical sensor Electrochemical supercapacitors a b s t r a c t Porous nickel oxide (NiO) microflowers have been successfully synthesized by calcining a coordina- tion microflower without any hard template, seed or using soft template. More importantly, porous NiO microflowers have been applied as effective electrochemical sensor of the tripeptide glutathione (GSH) and electrochemical supercapacitors. The effectively electrochemical GSH sensor of porous NiO microflowers in 0.1 M HAc–NaAc (pH 5.0) solution was the first time evaluated. Moreover, the specific capacitance of porous NiO microflower was up to 1678.4 F g -1 at current density of 0.625 A g -1 , and maintained about 99.7% at 6.25 A g -1 after 1000 cycles. © 2012 Elsevier Ltd. All rights reserved. 1. Introduction Thiols are very important to living organisms as they provide regulatory intracellular and extracellular functions. The tripeptide glutathione (Glu-Cys-Gly, GSH) is pivotal for reducing oxidative stress in cells and maintaining redox homeostasis that is cru- cial for cell growth [1–3]. Electrochemical methods have proven as very useful for determination of thiols as they are sensitive, selective, with very good linear range and rapid response times. The oxidation of thiols on carbon based electrodes exhibits rela- tively low heterogeneous electron transfer rates. In the past, the electrode materials used for the determination of thiols consisted of mercury, edge plane pyrolytic graphite, boron doped diamond electrode, fullerenes and carbon nanotubes [4–9]. The electro- catalytic enhancement of biologically related thiol detection was sought and PtFeNi [10] or PtNiCo [11] catalysts were employed. Recently, Martin Pumera have successfully discovered that NiO nanoparticles significantly enhance the signal of glutathione dur- ing cyclic voltammetry measurements [12,13]. As the development of nanoscience, precisely control of the morphology of NiO ∗ Corresponding authors at: College of Chemistry and Chemical Engineering, Anyang Normal University, Anyang, 455000, Henan, PR China. E-mail addresses: huanpangchem@hotmail.com (H. Pang), hhzheng@suda.edu.cn (H. Zheng), baiqingyuan1981@126.com (B. Yuan). nanomaterials would serve to maximize the performance of using inexpensive NiO for enhanced detection of regulatory peptides glu- tathione. Transition metal oxides such as ruthenium oxide, manganese oxide, cobalt oxide, and nickel oxide are qualified to be electro- chemical capacitor materials. Among these materials, NiO is of great significance, and the theoretical capacitance of NiO can be ca. 2573 F g -1 within 0.5 V. With the development of nanoscience, many groups found that nanomaterials generally exhibit many size and shape dependent properties, and the specific capacitance of NiO nanomaterials is depended on the synthesis method and morphology [14–27]. In particular, there have been considerable research efforts devoted to the use of nickel oxide for super- capacitors, due to its good pseudocapacitive behavior, practical availability, environmentally begin nature and low cost compared to the state-of-the-art supercapacitor material RuO 2 [16–24]. The interaction between metal ions and ligands has been widely investigated in materials science and chemistry during the past few decades [28,29]. Recently, a growing number of studies are now dedicated to the synthesis of nanostructured metal–organic complexes [30]. Coordination complexes have been used as a nanostructured precursor to prepare mesoporous metal oxides in our previous work [31–33]. The coordination complex precursor always has a micro or nanostructure due to the growth mechanism of the polymer complex precursor, and such unique nanostruc- ture may bring on an exciting performance of utility in many 0013-4686/$ – see front matter © 2012 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.electacta.2012.08.057