Pankaj B. Agarwal

Silver Nanoparticles in Comparison with Ionic Liquid and rGO as Gate Dopant for Paper–Pencil-Based Flexible Field-Effect Transistors

Nanoparticle-based flexible field-effect transistors (FETs) containing carbon nanotubes (CNTs) and silicon nanowires (SiNWs) have attracted tremendous attention, since their interesting device performance can be utilized for integrated nanoscale electronics. However, use of CNTs and SiNWs on polymer substrates poses serious limitations in terms of their fabrication procedure, repeatability, and biodegradability. In this article, we report for the first time the fabrication and characteristics of solution-processed FETs on a paper substrate doped with easily prepared silver nanoparticles (AgNPs). To compare the FET performance, we fabricated two other FETs on paper containing ionic liquid (IL, 1-butyl-3-methylimidazolium octyl sulfate) and reduced graphene oxide (rGO) as dopants. We observe that the AgNP-based dopant generated good FET characteristics in terms of linear transconductance variations and higher carrier concentration values, showing negligible changes after bending and aging. In comparison with the AgNP-FET, the rGO- and IL-based dopants yielded high carrier mobilities, but the rGO-based FET is more susceptible to aging and bending. The excellent linearity of the IDS–VG curve found for the AgNP-FET ensures its applicability for devices requiring linear transfer characteristics such as linear amplifiers.

Ammonia Sensing by PANI-DBSA Based Gas Sensor Exploiting Kelvin Probe Technique

Dodecyl benzene sulfonic acid (DBSA) doped polyaniline (PANI-DBSA) has been synthesized by chemical oxidative polymerization of aniline monomer in the presence of DBSA. The UV-visible spectroscopy and X-ray diffraction measurements confirm the formation of PANI and its doping by DBSA. SEM images show the formation of submicron size rod shaped PANI particles. A vibrating capacitor based ammonia gas sensor was prepared by spin coating PANI-DBSA film over copper (Cu) substrate. The sensor exploited Kelvin probe technique to monitor contact potential difference between PANI and Cu as a function of time and ammonia concentration. Upon exposure to 30 ppm ammonia, the sensor displays response time of 329 s, recovery time of 3600 s, and sensitivity value of 1.54 along with good repeatability.

Two Input Multiplexer Based on Single-Electronics

The design of capacitive single-electron transistors (C-SETs) based two-input multiplexer is reported in this paper. Voltage state logic is employed to design the circuit and SIMON 2.0 was used for simulation. Truth table of the designed two input multiplexer was verified for all the possible input vectors. Additionally, the stability of the circuit was checked by plotting stability and free energy history diagrams. The average power consumtion of the designed circuit is ~31.4 PicoWatts.

Comparative Study of SWNTs Dispersion in Organic Solvent and Surfactant Along with Observation of Multilayer Graphene

Organic solvents and surfactants both are used to disperse Carbon Nanotubes (CNTs), but the efficiency of both are different. Surfactant much efficiently disperse CNTs in comparison to organic solvent. As opposed to aqueous solutions, hydrophobic Single Wall Nanotubes (SWNTs) are easily wetted by organic solvent Di-Methyl Formamide (DMF) and therefore, to reduce self assembling of bundles and ropes of CNTs. Surfactants are effective at concentration 1 wt % for dispersion of SWNTs. Sodium Dodecyl Benzene Sulfonate (SDBS) effectively disperse aqueous solution of SWNTs at 0.5 mg/ml and further solution is diluted to concentration 0.3 mg/ml. Probe type sonication is used to make homogeneous solution and for initial exfoliation of CNTs. Small bundles and single SWNTs can be separated from bundles and amorphous carbon by using centrifugation. Atomic Force Microscopy (AFM) is employed to image the dispersed state of SWNTs by using organic solvent and aqueous solution of surfactant. Graphene presence and density difference of these are also observed at different concentration of SWNTs.

Large area nano-patterning /writing on gold substrate using dip – pen nanolithography (DPN)

Dip Pen Nanolithography (DPN) is utilized to pattern large area (50μmX50μm) gold substrate for application in fabricating Nano-gratings. For Nano-writing 16-MHA ink coated AFM tip was prepared using double dipping procedure. Gold substrate is fabricated on thermally grown SiO2 substrate by depositing ∼5 nm titanium layer followed by ∼30nm gold using DC pulse sputtering. The gratings were designed using period of 800nm and 25% duty cycle. Acquired AFM images indicate that as the AFM tip proceeds for nano-writing, line width decreases from 190nm to 100nm. This occurs probably due to depreciation of 16-MHA molecules in AFM tip as writing proceeds.

Positioning of CNTs over the gold substrate via self-assembled monolayer functionalization using dip-pen nanowriting

The most important aspect of fabrication of Carbon Nanotubes (CNTs) based devices/sensors is the selective and controlled positioning of CNTs, which is a challenging issue for the researchers now a days. Here, we have presented a simple and efficient methodology for positioning of CNTs using 16-MHA self-assembled monolayers (SAMs), written over the gold substrate using Dip-pen Nanowriting (DPN). The analysis of the obtained AFM images clearly shows significant height increment of nanopatterns, which corresponds to the attachment of carbonaceous material over the written nanopatterns. Carbon Nanotubes (CNTs), Dip-pen Nanowriting (DPN), 16-MHA, 1-ODT and Self-assembled Monolayer (SAM).