A major challenge in effectively treating infections is to provide timely diagnosis of a bacterial or viral agent. Current cell culture methods require >24 h to identify the cause of infection. The Toll-like Receptor (TLR) family of proteins can identify classes of pathogens and has been shown to work well in an impedance-based biosensor, where the protein is attached to an electrode via a self-assembled monolayer (SAM). While the sensitivity of these sensors has been good, they contain a high resistance (>1 kΩ) SAM, generating relatively small signals and requiring longer data collection, which is ill-suited to implementation outside of a laboratory. Here, we describe a novel approach to increase the signal magnitude and decrease the measurement time of a TLR-4 biosensor by inserting a redox-active ferrocenyl-terminated alkanethiol into a mixed SAM containing hydroxyl- and carboxyl-terminated alkanethiols. The SAM formation and modification was confirmed via contact angle and X-ray photoelectron spectroscopy measurements, with TLR-4 immobilization demonstrated through a modified immunosorbent assay. It is shown that these TLR-4 biosensors respond selectively to their intended target, Gram-negative bacteria at levels between 1 and 105 lysed cells/mL, while remaining insensitive to Gram-positive bacteria or viral particles at up to 105 particles/mL. Furthermore, the signal enhancement due to the addition of ferrocene decreased the measurement time to less than 1 min and has enabled this sensor to be used with an inexpensive, portable, hand-held potentiostat that could be easily implemented in field settings.

In this study, we determined the Pd(II) chlorocomplex species that has the most favorable interaction with an electropolymerized and protonated polyaniline (PANI) film. This study was completed with the intent to use this species to electrochemically build atomic palladium clusters in the PANI matrix. Varying amounts of NaCl were added to a KPdCl/HClO solution to result in three species studied: PdCl(HO), PdCl(HO), and PdCl. UV-vis spectroscopy was used to confirm the speciation, and Raman spectroscopy, X-ray photoelectron spectroscopy, and cyclic voltammograms were used to probe the interaction between the Pd species and PANI. It was determined that PdCl(HO) most effectively interacts with PANI as a result of the charge balance between the anion and the protonated nitrogen-containing groups in the polymer. It has been also found that some fraction of inserted Pd(II) cannot be reduced to Pd(0).

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A low-cost, thin, graphitized carbon electrode with electrodeposited platinum and polyaniline has been characterized for electrochemical oxidation of aliphatic alcohols in alkaline medium and for possible further incorporation of atomic metals and alloys. Our previously developed atomic metal polyaniline composites used solid platinum as the electrode material. The replacement of this solid platinum with a small amount of electrochemically annealed Pt on a carbon support was optimized for alcohol oxidation. An HPLC procedure for analysis of oxidation products of 1-propanol has also been utilized for the characterization of the composite electrode. © The Author ( The preparation of composite materials that function as electrocatalysts is an active field of research. The in-situ incorporation of metal clusters on an atomic scale, such as Au n and Au n Pd m (1 ≤ n,m ≤ 8), in a polyaniline matrix has been developed [1][2][3][4][5] and their use for oxidation of alcohols in alkaline media has been demonstrated. [6][7][8] It has been shown that the number of atoms, and the order in which they are added, tracks their electrocatalytic activity in excellent agreement with calculated electron affinity. 9,10 In order to generate maximum interaction between the active atomic metal centers embedded in polyaniline (PANI), the close coupling and synergistic effects of the composite components in the support cannot be overlooked. Carbon supported platinum is widely used as a composite electrode due to its known activity toward alcohols, 11 and composites of carbonplatinum-polyaniline have been studied in acidic media.12 Among all the different preparation procedures of Pt clusters -e.g. dispersement in paste and powders, 11 ion exchange, 13 impregnation, 13 colloidal precipitation, 13 vapor deposition, potential-step, 11,14 potential cycling, 13 and chronoamperometric 15 -the potentiostatic electrodeposition method 16,17 remains one of the best due to its high reproducibility and controllability. The forms of carbon that are ideal for potentiostatic deposition include glassy carbon, 18 nanotubes, 16 pyrolytic, 14,17 graphite cloth, fiber, and paper. 15 Platinum is known to have the highest activity for the oxygen reduction reaction (ORR) in alkaline media. 19Size and structural effects have remained the main issue for loading Pt nanoparticles into the different types of carbon support but an indirect influence of the support may also affect the rate of metal dispersion, the accessibility of active sites or even its own catalytic activity. One of the attractive features of composites prepared on atomic scale is dramatic reduction of the amount of precious metals in the composite electrode. In the case of atomic gold, such reduction is estimated to be on the order of 10,000. However, all of our previous preparations have been done on a solid Pt substrate coated with PANI matrix. Thus, the primary goal of this study has been replacement of expensive Pt with a less expensive electroactive material, e.g. carbon. However, a small amo...

Carbon has unique and desirable properties for use in applications such as fuel cells and batteries. The properties can vary widely depending on its structure and surface characteristics. Two types of carbon, a synthetic graphite produced from petroleum coke and an extruded graphite rod, were characterized using Raman spectroscopy and X-ray Photoelectron spectroscopy and the features were correlated with electrochemical properties of the material. The graphite rod was found to have a more disordered structure, greater sp 3 character, and a greater surface oxygen content as compared to the synthetic graphite from coke. Our results show that the characteristics of electrodeposited platinum and polyaniline depend on the type of substrate; the preferable carbon for producing composite materials for catalyst applications is the graphite from petroleum coke. © The Author Carbon used as a support material in fuel cells and batteries can vary in properties depending on the structure and impurities present. Reviews on carbon supports have indicated that graphite is commonly chosen to support catalytic metals due to its inert character and conductivity, and the support itself can affect performance of the fuel cell. [1][2][3][4] Composite electrodes can be produced from potentiostatic depositions of platinum and/or polyaniline (PANI) directly onto the carbon surface. Carbon supported platinum (C/Pt) is widely used for its known activity toward alcohol oxidation, 5-7 and carbon supported PANI (C/PANI), or even carbon-platinum supported PANI (C/Pt-PANI) electrodes are also attractive for the fabrication of composite catalyst materials. 8,9 Previous studies have shown that PANI can be used as a viable matrix for the insertion of catalytically active atomic-sized metal clusters, using platinum as support.10-12 We have focused our recent studies on using carbon as a support due to its benefits of being conductive, lightweight and inexpensive.13 However, in order to choose the appropriate carbon for a support electrode, understanding the effects that the substrate has on the PANI film is necessary. Dinh and Birss have compared the effects of differing types of support materials, such as noble metals and glassy carbon, on PANI properties. Impedance and CV studies on PANI grown by cycling revealed that the growth rate of the films and redox kinetics are affected by the differing supports. Specifically, slower PANI film growth was seen on glassy carbon when cycling between 0 to 1 V, while the films were more capacitive on the Pt and Au supports. However, with a larger cycling window for film deposition, the presence of surface oxygen groups was seen on the metal substrates leading to slower film growth.14 This study focuses specifically on graphitic substrates and how their structure and surface properties effect platinum deposition, as well as the growth of PANI film at constant potential. PANI growth was investigated on the surface of the carbon and on the C/Pt surface.For this study, we are using a novel synthetic graphite prod...