Bottom-up synthesis of ultrathin straight platinum nanowires. Electric field impact

We present a study of the electric field effect on electrochemically grown ultrathin, straight platinum nanowires with minimum diameter of 15 nm and length in the micrometer range, synthesized on a silicon oxide substrate between metal electrodes in H2PtCl6 solution. The influence of the concentration of the platinumcontaining acid and the frequency of the applied voltage on the diameter of the nanowires is discussed with a corresponding theoretical analysis. We demonstrate for the first time that the electric field profile, provided by the specific geometry of the metal electrodes, dramatically influences the growth and morphology of the nanowires. Finally, we provide guidelines for the controlled fabrication and contacting of straight, ultrathin metal wires, eliminating branching and dendritic growth, which is one of the main shortcomings of the current bottom-up nanotechnology. The proposed concept of self-assembly of thin nanowires, influenced by the electric field, potentially represents a new route for guided nanocontacting via smart design of the electrode geometry. The possible applications reach from nanoelectronics to gas sensors and biosensors

Dielectrophoretic Growth of Platinum Nanowires: Concentration and Temperature Dependence of the Growth Velocity

The growth velocity of platinum nanowires in an aqueous solution of K₂PtCl₄ is investigated as a function of the metal complex concentration and temperature. The solution is specially prepared to provide mainly the neutral complex <i>cis</i>-[PtCl₂(H₂O)₂] for growing nanowires by dielectrophoresis. The measured growth velocities indicate diffusion-limited nanowire growth at low concentration and high temperature in qualitative agreement with a theoretical analysis that includes the diffusion of metal complexes and the dielectrophoretic force on the complexes. At concentrations greater than 100 μM and low temperature, different behavior is observed, suggesting the growth rate to be limited by the deposition reaction of platinum at the nanowire tip. The enhancement of the K⁺ concentration is found to support nanowire growth. Possible reasons for a rate limitation and for the difference between observed and calculated nanowire growth velocities are discussed

Bimetallic nanowire sensors for extracellular electrochemical hydrogen peroxide detection in HL-1 cell culture

The present study of nanoelectrochemical sensors prepared by directed electrochemical nanowire assembly (DENA) is defined by the requirements of electrochemical analysis, where the transducer function of metallic nanowires is synergetically combined with their electrochemical catalytic activity with respect to a particular analyte. We show for the first time that this technique can be employed for metals (Pd, Au) and their bimetallic compositions to create various multicomponent sensor nanomaterials on a single chip without the use of multistep lithography for the spatially resolved analysis of solutions. The nanostructures of various compositions can be individually addressed when used in liquid media, so that the particular surface properties of the individual nanoarray elements can be used for the electrochemical analysis of specific analytes. The sensor application of these devices in electrolytes and cell culture conditions has been demonstrated for the first time. As an example, the Pd-Au nanowires prepared by DENA were used for a non-enzymatic analysis of H2O2 with a linear concentration interval of 10−6–10−3 M, sensitivity of 18 μA M−1, and detection limit of 3 × 10−7 M at as low absolute value of the detection potential as − 0.05 V. This sensor was also proven for the detection of hydrogen peroxide in HL-1 cell culture, demonstrating good biocompatibility and support for the cell culture conditions. Using various DENA-grown electrochemical compositions on a single chip, a novel multisensor platform is proposed for the determination of various analytes in electrolyte solutions for biocompatible sensor arrays, flexible multianalyte environmental and technological process monitoring, and healthcare areas