Electrochemical aptamer-based sensors enable realtime molecular measurements in the living body. The spatial resolution of these measurements and ability to perform measurements in targeted locations, however, is limited by the length and width of the device's working electrode. Historically, achieving good signal to noise in the complex, noisy in vivo environment has required working electrode lengths of 3−6 mm. To enable sensor miniaturization, here we have enhanced the signaling current obtained for a sensor of given macroscopic dimensions by increasing its surface area. Specifically, we produced nanoporous gold via an electrochemical alloying/dealloying technique to increase the microscopic surface area of our working electrodes by up to 100-fold. Using this approach, we have miniaturized in vivo electrochemical aptamer-based (EAB) sensors (here using sensors against the antibiotic, vancomycin) by a factor of 6 while retaining sensor signal and response times. Conveniently, the fabrication of nanoporous gold is simple, parallelizable, and compatible with both two-and three-dimensional electrode architectures, suggesting that it may be of value to a range of electrochemical biosensor applications.

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The electrochemical reduction of CO2 to useful chemicals and fuels has garnered a keen and broad interest. Herein, we report a unique nanocomposite consisting of Cu nanoparticles (NPs) and reduced graphene oxide (rGO) supported on a Cu substrate with a high catalytic activity for CO2 reduction. The nanocomposite was optimized in terms of the composition of Cu NPs and rGO as well as the overall amount. A gas chromatograph was employed to analyze the gaseous products, whereas a chemical oxygen demand (COD) method was proposed and utilized to quantify the overall liquid products. The optimized nanocomposite could effectively reduce CO2 to CO, HCOOH and CH4 with a Faradaic efficiency (FE) of 76.6% at −0.4 V (vs. RHE) in a CO2 saturated NaHCO3 solution. The remarkable catalytic activity, high FE, and excellent stability make this Cu-rGO nanocomposite promising for the electrochemical reduction of CO2 to value-added products to address the pressing environmental and energy challenges.

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