A novel hydrogen peroxide sensor based on Ag nanoparticles electrodeposited on DNA-networks modified glassy carbon electrode

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Abstract

A novel strategy to fabricate hydrogen peroxide (H2O2) sensor was developed by electrodepositing Ag nanoparticles (NPs) on a glassy carbon electrode modified with three-dimensional DNA networks. The result of electrochemical experiments showed that such constructed sensor had a favorable catalytic ability to reduction of H2O2. The well catalytic activity of the sensor was ascribed to the DNA networks that facilitated the formation and homogenous distribution of small Ag NPs. The resulted sensor achieved 95% of the steady-state current within 2 s and had a 1.7 μM detection limit of H2O2.

Introduction

Over the last decade, there has been a considerable interest in the accurate determination of hydrogen peroxide (H2O2) because it is an essential mediator in food, pharmaceutical, clinical and environmental analysis. Many techniques including titrimetry [1], spectrometry [2] and chemiluminescence [3] have been employed in the determination of H2O2. However, these techniques are obviously time-consuming and expensive. Recently, more attention has been paid to the electrochemistry technique owing to its intrinsic sensitivity, high selectivity and simplicity [4], [5].

Electrochemistry technique based on a simple and low-cost enzyme electrode has been extensively employed for accurate determination of H2O2 because of the intrinsic selectivity and sensitivity of enzymatic reactions [6], [7], [8]. Although, a lot of materials have been used to immobilize enzyme on an electrode for retaining the enzymatic biologic activity and electrically connecting the enzyme with the electrode surface, it was ineluctable that these materials might block the electron transfer and biologic activity of the enzyme [9], [10].

Inorganic materials modified electrode in determination of H2O2 is attracting more and more attention owing to its stability and convenience of electron transfer. Some inorganic materials (such as hexacyanoferrate [11], prussian blue-modified Au nanoparticles (NPs) [12], Pt NPs [13], [14], [15], nickel hexacyanoferrate [16] and perovskite-type oxide [17]), inorganic-organic composite materials [18], [19], [20], and inorganic-incorporated biology complex membranes [21], [22], [23], [24], [25] have been used for the preparation of H2O2 sensor. Recent studies have showed that Ag NPs exhibited catalytic activity for H2O2 [26]. The size and the distribution of Ag NPs played a vital role in the catalytic ability for H2O2. To obtain a good catalytic ability, electrodeposition of Ag+ in a solution containing DNA molecules to produce Ag NPs have been developed. However, the size of Ag NPs was about 50 nm and the packed density of Ag NPs was very high, which were unfavorable for catalytic ability due to the decrease of catalytic sites.

In this manuscript, we have exploited Ag NPs electrodeposited on three-dimensional DNA networks that were directly dropped on the surface of GC electrode as an electrocatalyst to fabricate a H2O2 sensor. Thus formed Ag NPs showed very good catalytic ability for the reduction of H2O2.

Section snippets

Materials

λ-DNA was obtained from Sino-American Biotechnology company (Beijing, China). Other chemicals were purchased from Beijing Chemical Reagent (Beijing, China).

Preparation of the H2O2 sensor

After the GC electrode was polished carefully, 10 μL DNA of different concentration was directly dropped onto the pretreated GC electrode and dried at 4 °C for 4 h. And then the electrode was immersed in 0.1 M KNO3 solution containing 3.0 mM AgNO3 and electrodeposited for different time to obtain Ag NPs modified electrode.

Electrochemical measurements and apparatus

All electrochemical

Electrodeposition of Ag NPs on DNA network

Cyclic voltammetric (CV) was utilized to monitor the redox behaviors of Ag+ at bare and DNA networks modified GC electrode. As shown in Fig. 1a, in the solution of 3.0 mM AgNO3 and 0.1 M KNO3, a bare GC electrode showed a cathodic peak at 0.30 V and a sharp anodic peak at 0.49 V. The cathodic peak was ascribed to the reduction of Ag+ to form Ag NPs and the anodic peak was attributed to the stripping of the electrodeposited Ag NPs. However, when the DNA networks modified electrode was scanned in the

Conclusion

A novel H2O2 sensor based on Ag NPs electrodeposited on DNA-networks modified GC electrode was fabricated. Our experiments confirmed that when the DNA concentration was 100 ng/μL and the electrodeposition time was 120 s, the sensor showed the maximal electrocatalytic ability for the reduction of H2O2. The resulted sensor exhibited extremely fast amperometric response, a low detection limit, and a wide linear range to H2O2.

Acknowledgments

This work was supported by the National Natural Science Foundation of China (20705001) and Foundation of Jiangxi Educational Committee ([2007]127).

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