Semiconducting bacterial biofilm based on graphene-MoS2 template and component dependent gating behavior

In this paper, we report for the first time, the synthesis of a semiconducting biofilm. Photosynthetic bacterial biofilm has been used to weave together MoS2 nanosheets into an adherent film grown on interdigitated electrodes. Liquid-phase exfoliation of bulk MoS2 powder was used to obtain MoS2 nanosheets. A synchronous-fluorescence scan revealed the presence of two emission maxima at 682nm and 715nm for the MoS2 suspension. Such maxima with bandgap energy 1.82 and 1.73 eV corresponded to the single and double layer of MoS2. The presence of such single and multi-layered structures was confirmed by Raman spectroscopy, FTIR studies, and electron microscopy. The current-voltage (I-V) studies of such a bio-nano hybrid revealed the emergence of the gated nature of the current flow. This Schottky diode like behavior, reported earlier for Graphene-biofilm junctions, is also observed in this case. Gating voltage depended on the composition of the biofilm. The semiconductor biofilms, when studied using electrochemical impedance spectroscopy, revealed characteristic Nyquist and Bode plots, suggesting special circuit-equivalence for each film. While Mos2 was marked with stability with respect to variations in RMS voltage and bias voltage, the graphene biofilm was unique by the absence of any Warburg element.

Stability and Dynamic Response of Analog and Digital Control loops of Bidirectional buck-boost Converter for Renewable Energy Applications

This article presents the stability and dynamic response of open loop and closed loop control of Bidirectional buck-boost converter(BBC) using PID and PIDN controllers through transfer function model implemented in MATLAB code. In order to ensure the stability of switch mode power supplies the control loop behaviors need to be characterized. Improvement of stability of BBC using PID/PIDN compensators is demonstrated in both analog and digital domains by plotting bode plots. Step response of BBC using PID /PIDN controllers are plotted that defines the dynamic behavior of the system.PIDN compensator is proposed to maintain a healthy balance between the stability and transient behavior since both are indirectly proportional.

Electrochemical Study of Calcareous Deposit Formation in Simulated Soil Solution under Cathodic Protection

Cathodic protection induces the formation of a calcareous layer has been shown to improve metal protection against corrosion by reducing the oxygen diffusion on the metal surface. The present study focuses on the electrochemical scaling induced by the application of cathodic polarisation. A combination of non-invasive in-situ electrochemical techniques and electrochemical impedance spectroscopy was used. Metal/electrolyte interface behaviour was studied using voltammetry to determine the controlling anodic and cathodic reactions. One-week long experiments were conducted. Applied potential –1.2 VSCE was shown to enable the formation of CaCO3 allotropes calcite and aragonite, and brucite due to increased interfacial pH which resulted in the formation of hydrogen at the electrode surface. Time constants from bode plots for applied potential –1.2 VSCE also illustrated the inhomogeneity of the calcareous layer. Modelling of polarisation curves illustrated a “passivation” phenomenon which resulted from formation of hydroxyl cations. This was further validated by bode plots with the added information on the diffusion reaction process. High frequency behaviour showed a steady increase in the electrolyte resistance which may be attributed to the formation of the calcareous layer. Evidence of the initial Mg-gel porous layer, which precedes the formation of brucite, was found.

Stability and Dynamic Response of Analog and Digital Control loops of Bidirectional buck-boost Converter for Renewable Energy Applications

This article presents the stability and dynamic response of open loop and closed loop control of Bidirectional buck-boost converter(BBC) using PID and PIDN controllers through transfer function model implemented in MATLAB code. In order to ensure the stability of switch mode power supplies the control loop behaviors need to be characterized. Improvement of stability of BBC using PID/PIDN compensators is demonstrated in both analog and digital domains by plotting bode plots. Step response of BBC using PID /PIDN controllers are plotted that defines the dynamic behavior of the system.PIDN compensator is proposed to maintain a healthy balance between the stability and transient behavior since both are indirectly proportional.