Pankaj Koinkar

Ordering of fullerene and carbon nanotube thin films under energetic ion impact

We report the ordering of carbon nanostructures under energetic ion irradiation at low fluence (<5×1011ions∕cm2). Fullerene thin films and multiwalled carbon nanotube (MWCNT) films were irradiated with 200MeV Au and 60MeV Ni ions at different ion fluences, respectively. The changes in the irradiated films have been investigated by means of Fourier transform infrared (FTIR) spectroscopy, x-ray diffraction, and Raman spectroscopy. FTIR and Raman spectroscopy show the improvement of vibration strength in low fluence irradiated fullerene and MWCNT films. X-ray diffraction analysis on low fluence irradiated fullerene films revealed the structural order along the (220) atomic planes.

Organization of cubic CeO2 nanoparticles on the edges of self assembled tapered ZnO nanorods via a template free one-pot synthesis: significant cathodoluminescence and field emission properties

The present investigation explores the controlled architecture of a CeO2–ZnO nanocomposite via a template-free, low temperature, facile single step solvothermal approach. This complex architecture depicts cubic single crystalline CeO2 nanoparticles (size ∼15 nm) grown on the edges of tapered ZnO nanorods with definite orientations and alignments. The formation of wurtzite ZnO, cubic CeO2 and the coexistence of Ce3+ and Ce4+ on the surface of the CeO2–ZnO nanocomposites are confirmed using various characterization tools. The finding of such unique nanostructures by a facile method is exemplified by a plausible growth mechanism. Surprisingly, the aqueous mediated ultrasonication reaction conferred the formation of crystalline ZnO nanotubes of diameter ∼50 nm. Spatially resolved cathodoluminescence spectra are obtained by linearly scanning an individual CeO2–ZnO nanorod along its length, which reveals the size-dependent surface effects. Interestingly, such hybrid CeO2–ZnO nanoarchitecture is observed to exhibit enhanced field emission properties, demonstrating better current stability as compared to other ZnO nanostructures. This is attributed mainly to strong surface interactions between the Ce-ionic species and the ZnO nanorods. Herein, a soft-chemical approach is used for the first time to architect a binary oxide nanostructure, which is otherwise accomplished using high temperature techniques, as reported elsewhere. Also, the present work not only gives insight into understanding the hierarchical growth behaviour of the CeO2–ZnO nanocomposite in a solution phase synthetic system, but also provides an efficient route to enhance the field emission performance of ZnO nanostructures, which could be extended to other potential applications, such as chemical sensors, optoelectronic devices and photocatalysts.

Promising Field Emission Characteristics of Polyaniline Nanotubes

Polyaniline (PANI) nanotubes have been synthesized employing chemical polymerization with acetic acid as dopant. The synthesized PANI nanotubes were characterized by Scanning electron microscope (SEM), Transmission electron microscope (TEM), Uv-visible spectroscopy and Fourier transform infrared spectroscopy (FTIR). The SEM and TEM analysis clearly reveals the formation of PANI nanotubes, with outer diameter in the range of 50-150 nm and length in several microns. The Uv-visible and FTIR spectra exhibit characteristic features corresponding to electrically conducting phase of doped PANI. Field emission (FE) studies of the PANI nanotubes were performed in planar diode configuration at a base pressure of ∼1 x 10 ―8 Torr. From the FE results, value of the turn on field required to draw an emission current density of 1 μA/cm 2 was found to be 1.55 V/μm and current density of 1 mA/cm 2 has been drawn at an applied field of 3.8 V/μm. The PANI nanotubes emitter exhibited good emission current stability at pre-set value of 1 μA over duration of more than 3 h. The ease of synthesis route and interesting field emission properties recommend the PANI nanotubes as a promising material for field emission based applications in vacuum micro-nanoelectronic devices.

A fine pointed glucose oxidase immobilized electrode for low-invasive amperometric glucose monitoring

A low invasive type glucose sensor, which has a sensing region at the tip of a fine pointed electrode, was developed for continuous glucose monitoring. Platinum-iridium alloy electrode with a surface area of 0.045mm(2) was settled at the middle of pointed PEEK (Polyetheretherketone) tubing and was employed as sensing electrode. Electrodeposition of glucose oxidase in the presence of surfactant, Triton X-100, was performed for high-density enzyme immobilization followed by the electropolymerization of o-phenylenediamine for the formation of functional entrapping and permselective polymer membrane. Ag/AgCl film was coated on the surface of PEEK tubing as reference electrode. Amperometric responses of the prepared sensors to glucose were measured at a potential of 0.60V (vs. Ag/AgCl). The prepared electrode showed the sensitivity of 2.55μA/cm(2) mM with high linearity of 0.9986, within the glucose concentration range up to 21mM. The detection limit (S/N=3) was determined to be 0.11mM. The glucose sensor properties were evaluated in phosphate buffer solution and in vivo monitoring by the implantation of the sensors in rabbit, while conventional needle type sensors as a reference were used. The results showed that change in output current of the proposed sensor fluctuated similar with one in output current of the conventional needle type sensors, which was also in similar accordance with actual blood sugar level measured by commercially glucose meter. One-point calibration method was used to calibrate the sensor output current.

Poly(O-anisidine) coatings on low carbon steel

Abstract Poly( O -anisidine) (POA) coatings have been synthesized on low carbon steel (LCS) substrate by electrochemical polymerization of O -anisidine monomer in aqueous solution of oxalic acid. These coatings were characterized by cyclic voltammetry (CV), Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD) measurements and scanning electron microscopy (SEM). It is observed that the polarization of the LCS substrate in an aqueous oxalic acid medium results into passivation of its surface via the formation of crystalline iron oxalate (FeC 2 O 4 , 2H 2 O) layer. In the presence of O -anisidine monomer, the electrochemical polymerization of O -anisidine takes place and uniform, strongly adherent dark green POA coating is obtained on the substrate. The molecular structure of the POA coating is similar to that of deposited on SnO 2 :F coated glass substrates.

Chemiresistive sensor based on polythiophene-modified single-walled carbon nanotubes for detection of NO2

In the present investigation, a chemiresistive sensor based on conducting polythiophene-modified single-walled carbon nanotubes (SWNTs) for NO2 detection has been reported. The SWNTs were aligned across 3 μm gap between two gold microelectrodes on Si/SiO2 substrate. Alignment of SWNTs was carried out by using AC dielectrophoretic technique and it was confirmed by current–voltage (I–V) measurement. Aligned SWNTs were modified by conducting polythiophene using charge controlled potentiostatic deposition and it was confirmed by field-effect transistor (FET) and electrochemical measurements. Polythiophene-modified SWNT devices were used for the NO2 detection in chemiresistive modality. This sensor exhibited very good linear response range from 10 ppb to 10 ppm.

Biosynthesis of silver nanoparticles by using Ganoderma-mushroom extract

Present study reports the biochemical synthesis of silver nanoparticles (Ag-NPs) from aqueous medium by using the extract of medicinal mushroom Ganoderma, as a reducing and stabilizing agents. The Ag-NPs are prepared at room temperature by the reduction of Ag+ to Ag in aqueous solution of AgNO3. The resultant particles are characterized by using UV-visible spectroscopy, Fourier transform infrared (FTIR) spectroscopy and transmission electron microscopy (TEM) measurement techniques. The formation of Ag-NPs is confirmed by recording the UV-visible absorption spectra for surface plasmon resonance (SPR) where peak around 427 nm. The prominent changes observed in FTIR spectra supported the reduction of Ag+ to Ag. The morphological features of Ag-NPs are evaluated from HRTEM. The spherical Ag-NPs are observed in transmission electron microscopy (TEM) studies. The particle size distribution is found to be nearly uniform with average particle size of 2 nm. The Ag-NPs aged for 15, 30, 60 and 120 days showed no profound effect on the position of SPR peak in UV-visible studies, indicating the protecting/capping ability of medicinal mushroom Ganoderma in the synthesis of Ag-NPs.

Spin coated unsubstituted copper phthalocyanine thin films for nitrogen dioxide sensors

Copper phthalocyanine (CuPc) is synthesized chemically and used for making CuPc thin films using spin coating technique. Films were prepared from trifluroacetic acid (TFA) and chlorobenzene mixed solution on the glass substrate. Spin coated films of unsubstituted CuPc films were heat annealed at 150°C for 2 h duration and were used to study NO2 gas sensing characteristics. α-phase of CuPc is noted by UV-visible absorption spectra. IR spectra of undoped CuPc films and doped CuPc films with NO2 revealed that, doping of nitrogen dioxide modifies and deletes some of the bands. The effect of NO2 at various concentrations from 50 ppm to 500 ppm in atmospheric air at room temperature on the electrical conductivity of CuPc films was studied. Sensitivity, response time and repeatability of the CuPc sensor were discussed in this paper.

Field electron emission characteristics of plasma treated carbon nanotubes

This paper reports the effect of hydrogen (H2) plasma treatment on field emission property of double walled carbon nanotubes (DWCNTs) synthesized by using chemical vapor deposition method. The hydrogen plasma treatment was carried out for various duration. The DWCNTs films were characterized by using scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Raman spectroscopy. The results showed that the field emission properties of DWCNTs were influenced with increasing plasma treatment duration. The Raman spectra of samples clearly show structural defects after hydrogen plasma treatment. It is observed that the change in the field emission characteristics of DWCNTs is attributed to the structural defects due to the H2 plasma and depends on the plasma treatment duration.

Organic field-effect transistors: predictive control on performance parameters

We report the fabrication and characterization of poly(N-methylpyrrole) nanowires electrode junction based back-gated field-effect transistors under varying dopant atmosphere. Influences of the anionic radius of dopants on electrochemical, morphological, spectroscopic and electrical characteristics of synthesized nanowires have been investigated. The FET measurements have revealed highly efficient gate induced modulation of the channel conduction behaviour for all dopant cases and characteristic FET parameters have been estimated. The best observed device in terms of charge carrier mobility (µ) = 4.54 × 10 −4 cm 2 V −1 s −1 and on-off ratio (Ion/Ioff ) = 8.5 × 10 3 could be characterized with NaOH as dopant. Observed behaviour of the FET devices has been rationally related to the anionic radius of dopants. Plausible interpretation reflects that dopant dimension can be a significant and facile tool for optimized designing of polymeric FETs. (Some figures may appear in colour only in the online journal)