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Electrochemical reduction and electrodeposition are two effective methods for the preparation of new nanomaterials for electrochemical sensing. In this work, the reduced graphene oxide‐nickel nanoparticles composite (RGO‐NiNPs) was synthesized using both methods mentioned above. The fabrication process was simple and easily performed. Then, the RGO‐NiNPs composite was characterized by SEM, EDS, and XRD. Furthermore, for the strong catalytic ability of the high‐valent oxyhydroxide species (NiOOH) formed in alkaline media, the composite was used as the matrix for nonenzymatic detection of glucose. Comparing with NiNPs modified glassy carbon electrode (NiNPs/GCE), the RGO‐NiNPs/GCE showed better sensitivity and stability. A low detection limit of 0.1 µM with a wide linear range from 2 µM to 2.1 mM (R=0.996) was obtained.

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were purchased from Alfa Aesar. Ammonium peroxydisulfate ((NH 4) 2 S 2 O 8) was purchased from Xilong Chemical Industry Co. Ltd. (Guangdong, China). Concentrated sulfuric acid (H 2 SO 4) and ammonium fluoride (NH 4 F) were obtained from Beijing Chemical Factory (Beijing, China). Unless otherwise stated, other reagents were of analytical grade and were used without further purification. All aqueous solutions were prepared with ultrapure water (>18 MΩ) from an automatic double distillation system (Shanghai, China). 1.2 Apparatus Electronic Supplementary Material (ESI) for Nanoscale.

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This study demonstrates a cocaine sensing method employing graphene oxide (GO), gold nanoparticles and a structure switching aptamer, which can fold into a three-way junction in the presence of cocaine. On the observation of gold nanoparticles (Au NPs) induced graphene oxide fluorescence quenching, a structure switching aptamer of cocaine was introduced as the linker between the two parts. Firstly, two fragments of a cocaine aptamer were immobilized covalently onto GO and Au NPs, respectively. Then when the three-way junction formed, the Au NPs were drawn near to the GO surface and induced a fluorescence intensity decrease. The limit of detection was 0.1 μM for cocaine in purified water, and well defined results were also obtained in biological fluids and the specificity experiment, which expands the feasibility of the as-prepared sensor for practical applications.

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