This article details the study of electrochemical behavior of new carbon electrodes based on pyrolysis of different paper sources to be used in biosensor applications. The resistivity of the pyrolyzed papers was initially used as screening parameters to select the best three paper samples (imaging card paper, multipurpose printing paper, and 3MM chromatography paper) and assemble working electrodes that were further characterized by a combination of microscopy, electrochemistry, and spectroscopy. Although slight differences in performance were observed, all carbon substrates fabricated from pyrolysis of paper allowed the development of competitive biosensors for uric acid. The presented results demonstrate the potential of these electrodes for sensing applications and highlight the potential advantages of 3MM chromatography paper as a substrate to fabricate electrodes by pyrolysis.

A one-step approach for the synthesis and integration of copper nanoparticles (CuNPs) onto paper-based carbon electrodes is herein reported. The method is based on the pyrolysis (1000 °C under a mixture of 95% Ar / 5% H2 for 1 hour) of paper strips modified with a saturated solution of CuSO4 and yields to the formation of abundant CuNPs on the surface of carbonized cellulose fibers. The resulting substrates were characterized by a combination of scanning electron microscopy, EDX, Raman spectroscopy as well as electrical and electrochemical techniques. Their potential application, as working electrodes for nonenzymatic amperometric determination of glucose, was then demonstrated (linear response up to 3 mM and a sensitivity of 460 ± 8 μA·cm−2·mM−1). Besides being a simple and inexpensive process for the development of electrochemically-active substrates, this approach opens new possibilities for the in-situ synthesis of metallic nanoparticles without the traditional requirements of solutions and adjuvants.

The possibility of using pyrolyzed paper as disposable working electrodes for trace metals determination is reported for the first time. A small piece of pyrolyzed paper (0.7×0.7cm) was positioned at the bottom side of the electrochemical cell using a rubber O-ring, which defined the electrode area (0.48cm; 0.18cm). A large number of electrodes can be obtained from a single piece of standard dimensions (2.5cm×7.5cm) of paper, therefore minimizing the cost per unit. The electrochemical performance of the pyrolyzed paper was demonstrated by cyclic voltammetry, electrochemical impedance spectroscopy and by the determination of Zn, Cd, and Pb by square-wave anodic stripping voltammetry. The unmodified pyrolyzed paper showed excellent performance for Pb and Cd detection (LOD =0.19 and 0.16 ppb, respectively). In the presence of Bi(in-situ film formation), the simultaneous determination of Zn, Cd and Pb was also possible (LOD=0.26, 0.25, and 0.39 ppb, respectively).

In the fall of 1996, numerous bacteria capable of degrading JP‐7 jet fuel were isolated from soil collected at Beale Air Force Base in northern California. The most prevalent organism, identified as Nocardioides luteus by16s rRNA sequencing (MIDI Labs, Inc.), was selected for further analysis. Analysis of JP‐7 following inoculation with N. luteus demonstrated degradation of the C11 alkane component of the fuel. Growth rates of N. luteus were determined with alkanes of various lengths as the sole carbon and energy source. The organism grew best on shorter length alkanes (C8 and C10). Growth was measurably slower on C11, and minimal on C12, C13, and C14.

Conventional immunosensors typically rely on passive diffusion dominated transport of analytes for binding reaction and hence, it is limited by low sensitivity and long detection times. We report a simple and efficient impedance sensing method that can be utilized to overcome both sensitivity and diffusion limitations of immunosensors. This method incorporates the structural advantage of nanorod-covered interdigitated electrodes and the microstirring effect of AC electrothermal flow (ACET) with impedance spectroscopy. ACET flow induced by a biased AC electric field can rapidly convect the analyte onto nanorod structured electrodes within a few seconds and enriches the number of binding molecules because of excessive effective surface area. We performed numerical simulations to investigate the effect of ACET flow on the biosensor performance. The results indicated that AC bias to the side electrodes could induce fast convective flow, which facilitates the transport of the target molecules to the binding region located in the middle as a floating electrode. The temperature rise due to the Joule heating effect was measured using a thermoreflectance imaging method to find the optimum device operation conditions. The change of impedance caused by the receptors-target molecules binding at the sample/electrode interface was experimentally measured and quantified in real-time using the impedance spectroscopy technique. We observed that the impedance sensing method exhibited extremely fast response compared with those under no bias conditions. The measured impedance change can reach saturation in a minute. Compared to the conventional incubation method, the ACET flow enhanced method is faster in its reaction time, and the detection limit can be reduced to 1 ng/ml.In this work, we demonstrate that this sensor technology is promising and reliable for rapid, sensitive, and real-time monitoring biomolecules in biologically relevant media such as blood, urine, and saliva.