Kanchan Saxena - Academia.edu (original) (raw)

Papers by Kanchan Saxena

Efficient white light emission by mixing of red emission from (Ir-BTPA) [bis(2-(2'-benzothienyl) ... more Efficient white light emission by mixing of red emission from (Ir-BTPA) [bis(2-(2'-benzothienyl) pyridinato-N,C 3') (acetyl-acetonate) iridium(III) and greenish blue from (FIrPic) [bis(2-(4,6-difluorophenyl)pyridinato-N,C 2') iridium(III)] has been studied. Ir-BTPA and FIrPic are co-doped into a 4, 4' bis 9 carbozyl (biphenyl) (CPB) host. The device emission colour is controlled by varying dopant concentration. Photoluminescence (PL), electroluminescence (EL) and colour coordinates have been studied as a function of applied voltage. The EL spectra of the devices with the co-doped emissive layer show three emission peaks at 469, 500 and 611 nm. Commission Internationale de l'Eclairage (CIE) coordinates of the devices are 0.27, 0.32 at 18 V and are well within the white region.

Nanotechnology, 2021

We report the fabrication of low cost highly structured silver (Ag) capped aluminium (Al) nanorod... more We report the fabrication of low cost highly structured silver (Ag) capped aluminium (Al) nanorods (NRs) as surface enhanced Raman spectroscopy (SERS) substrate utilising the glancing angle deposition technique. The nano-capping of silver onto the Al NRs can concentrate the local electric field within the minimal volume that can serve as hotspots. The average size of the Ag nanocaps was 50 nm. The newly proposed nanoporous Ag capped Al NRs as SERS substrate could detect the Raman signal of rhodamine 6G (R6G) up to 10−15 molar concentration. The significant enhancement in the Raman signal of 107 was achieved for Ag capped Al NRs considering R6G as a probe molecule. Using the developed SERS substrate, we recorded Raman spectra for Escherichia coli bacteria with its concentration varying from 108 colony forming units per ml (CFU ml−1) up to 102 CFU ml−1. All the reported Raman spectra were acquired by a portable handheld Raman spectrometer. Hence, this newly proposed low cost, effective SERS substrate can be used commercially for the onsite detection of clinical pathogens. The 3D finite difference time domain simulation model was performed for Ag capped Al nanostructure to understand the generation of hotspots. The simulated results show excellent agreement with the experimental results. We fabricated uncapped Ag nanorods of similar dimensions and performed the experimental measurements and simulations for comparison. We found a significant enhancement in Ag capped Al NRs compared to the long Ag NRs. The description of the Raman signal enhancement has been elaborated.

Review of Scientific Instruments, 1988

A method has been devised for studying the spontaneous polarization, dynamics of polarization rev... more A method has been devised for studying the spontaneous polarization, dynamics of polarization reversal, and the molecular reorientation processes that occur in the bulk and surfaces of ferroelectric liquid crystals. These studies have been carried out by analyzing the current response to triangular- and square-wave forms. The current response to a triangular wave yields the spontaneous polarization by conveniently subtracting the background contribution due to the conductive and capacitive currents. Molecular reorientation processes which take place within the bulk and the boundary surface layer can be studied by the appearance of polarization current peaks on the triangular-wave response. The dynamics of polarization reversal between bistable states and of the polarization change between the zero-field relaxed state and either of the saturation remanent polarization states have been studied by applying ‘‘symmetric’’ and ‘‘asymmetric’’ square waves. The technique can also be success...

Physica Status Solidi (a), 1989

The polarization reversal current response for parallel and dntiparallel rubbed samples of a 3 pm... more The polarization reversal current response for parallel and dntiparallel rubbed samples of a 3 pm thick sample of DOBAMBC are studied by applying triangular pulses of varying voltage. The antiparallel rubbed sample shows two peaks and parallel rubbed sample shows three peaks of polarization reversal. The third peak appears before the peak of bulk switching and the zero field point of the applied pulse. It is shown that the selective pretilt angles with tho surface results in tilted or bent smectic layer to give the multipeak response of the polarization reversal current. Das Polarisationsumkehrstromverhalten fur parallel und antiparallel geschliffene Proben einer 3 pin dicken DOBAMBC-Probe werden mit dreieckformig anwachsenden Spannungsimpulsen untersucht. Die antiparallel geschliffene Probe zeigt zwei Maxima. und die parallel geschliffene Probe zeigt drei Maxima von Polarisationsumkehr. Das dritte Maximum erscheint vor dem Maximum des Volumenverhaltens und dem Nullfeldpunkt des angelegten Impulses. Es wird gezeigt, dal3 die ausgewahlten Vorneigungswinkel mit der Oberflache zu einer gekippten oder gebogrnen smektischen Schicht fuhren, die den Mehrfachmaximumrespons des Polarisationsumkehrstroms liefert.

Optical Materials, 2009

We present an organic light emitting diode with a perforated WO 3 hole injection layer to improve... more We present an organic light emitting diode with a perforated WO 3 hole injection layer to improve the light extraction efficiency. The two-dimensionally perforated WO 3 layer was fabricated by use of colloidal lithography. The light extraction efficiency was improved due to Bragg scattering of waveguide modes and surface plasmon polaritons, and the operating voltage was also decreased. As a result, the external quantum efficiency and the power efficiency were increased as compared with those of conventional organic light emitting diodes without WO 3 layer. The angular dependence of emission characteristics was investigated by measuring radiant intensity profiles for emission angles and azimuthal angles.

Journal of Luminescence, 2010

We report the measurement of coherence characteristics of light-emitting diodes (LEDs). Experimen... more We report the measurement of coherence characteristics of light-emitting diodes (LEDs). Experiments were performed using red and green color LEDs directly illuminating the Young&amp;amp;amp;amp;amp;amp;#39;s double slit kept in the far-zone. Fourier transform fringe analysis technique was used for the measurement of the visibility of interference fringes from which the modulus of degree of spectral coherence was determined. Low degree of

Japanese Journal of Applied Physics, 1987

Symmetric colour switching in unaligned and aligned very thin (<1 µm) samples of ferroelectric... more Symmetric colour switching in unaligned and aligned very thin (<1 µm) samples of ferroelectric liquid crystal DOBAMBC has been observed by applying both polarities of a dc electric field. The polarization-change current developed in a very thin FLC cell has been studied by applying symmetric (-5 V–0 V–+5 V) and asymmetric [(+ or -) 10 V–0 V] triangular wave pulses. The dynamics of colour changes amongst the same colours and amongst the multicoloured 0 V favoured state and a coloured state have been studied by applying low-voltage symmetric and asymmetric square pulses. For a symmetric triangular pulse, a single peak of polarization change and for an asymmetric pulse, two peaks of polarization change near the 0 V region for molecular reorientation amongst the same coloured state have been observed. It has been established that it is essentially the presence of an additional field, called a depolarization field, which causes a single peak of polarization-change current in the case ...

Bulletin of Materials Science, 2014

Undoped and aluminium (Al)-doped zinc oxide (ZnO) nanorods have been synthesized by electrochemic... more Undoped and aluminium (Al)-doped zinc oxide (ZnO) nanorods have been synthesized by electrochemical route. The synthesized materials have been characterized by X-ray diffraction, UV-visible spectrometer and scanning electron microscope. The Al-doped ZnO nanorods have been coated with polyvinyl alcohol. Currentvoltage characteristics have been investigated in dark and under UV-light illumination. Aluminium doping in ZnO increase its electrical conductivity and further polyvinyl alcohol coating on Al-doped ZnO increase UV sensitivity of the material. Response and recovery time of Al-doped ZnO and PVA-coated Al-doped ZnO nanorods have been recorded. PVA-coated Al-doped ZnO nanorods shows very fast response and recovery time of 10 s in comparison to uncoated ZnO (20 min) nanorods.

Ferroelectrics, Aug 1, 1997

Temperature dependence of the tilt angle, polarization and capacitance has been studied in three ... more Temperature dependence of the tilt angle, polarization and capacitance has been studied in three different FLC-mixtures and various cell thicknesses and the Landau expansion coefficients α and b have been determined. It has been found that these parameters are considerably affected by the thickness of the samples and smaller values of apparent Landau expansion coefficients have been obtained in the

Organic Electronics, 2018

A new perovskite material based on ethylene-diamine-dichloride and lead iodide as organic and ino... more A new perovskite material based on ethylene-diamine-dichloride and lead iodide as organic and inorganic precursors respectively was synthesized. Thin films of perovskite material were characterized using SEM, UV-Visible spectroscopy, XRD, and FT-IR. Sensing properties of inorganic organic perovskite thin films were studied and it was found to be selective for ammonia detection. Ammonia being one of the most hazardous and volatile chemical becomes necessary to detect. Color change of perovskite film from yellow to orange was observed in the presence of ammonia vapors. Electrical measurements showed decrease in resistance in the presence of ammonia vapors. Low concentration upto 50 ppm can be easily detected in approximately 40 seconds. The present method for detecting ammonia is unique, simple, selective, low cost and can be easily implemented for the field studies.

Optics Communications, 1995

Springer Proceedings in Physics, 2016

Journal of Optics, 2015

ABSTRACT We report significant enhancement in light out-coupling efficiency of organic light-emit... more ABSTRACT We report significant enhancement in light out-coupling efficiency of organic light-emitting devices (OLEDs) using a nano-structured substrate by rapid thermal processing (RTP). On the backside of the indium tin oxide (ITO) coated glass substrate a thin film of magnesium fluoride (MgF2) was coated by thermal evaporation. Nano-structured films of MgF2 and ITO were then produced by RTP on both sides of the glass substrate. Bottom-emitting OLEDs were fabricated on the ITO-coated glass substrate with α-NPD as the hole transport layer, Alq3 as the emissive layer, and LiF and aluminum as the cathode. On the backside of the glass substrate nano-structured MgF2 were fabricated by RTP. Experimental results of enhancement of electroluminescent intensity (EL) with and without nano-structured films are presented. Results of EL intensity of OLED are also compared with the uniform MgF2 film coated on the backside of the substrate. It was found that the enhancement of EL intensity is much higher in the case of nano-porous MgF2 film than in the case of uniform MgF2 coated on the backside of the glass substrate.

Journal of Nanoengineering and Nanomanufacturing, 2013

ZnO nanorods have been grown on F-SnO 2 substrate by electrochemical deposition method from aqueo... more ZnO nanorods have been grown on F-SnO 2 substrate by electrochemical deposition method from aqueous solution with different current densities. From, the study of surface morphology, the film grown with low current density was found to be uniform showing the growth of ZnO nanorods along its length. X-ray diffraction study revealed the nanorods deposited at current densities 1.5 m Amp/cm 2 were mainly orientated along 002 directions. From study of UV-vis spectra, band gap was evaluated to be 3.34 eV representing strong excitonic absorption. The violet emission at 423 nm was attributed to the transition of an electron from a deep donor level of neutral zinc interstitial to the valence band. The antibacterial activity of ZnO nanorods was studied for bacteria Escherichia coli, which shows a zone of inhibition around ZnO nanorods indicating a growth inhibition property of ZnO nanorods.

Liquid Crystals: Physics, Technology, and Applications, 1998

ABSTRACT

Environmental Science and Engineering, 2013

Poly (3, 4-ethylene dioxythiophene)-poly (styrene sulphonate) (PEDOT:PSS) is the most commonly us... more Poly (3, 4-ethylene dioxythiophene)-poly (styrene sulphonate) (PEDOT:PSS) is the most commonly used conducting polymer in organic LEDs, photovoltaics and sensor applications. We studied the humidity sensing properties of this polymer and its nanocomposites. It has been found that chemically treated single walled carbon nanotubes and PEDOT:PSS polymer nanocomposites shows good humidity sensing properties.

Optics Communications, 2006

We report the studies on photoluminescence (PL) and electroluminescence (EL) spectra of organic l... more We report the studies on photoluminescence (PL) and electroluminescence (EL) spectra of organic light emitting diodes (OLED) based on most widely used light emitting material, ie, Tris-(8-hydroxyquinoline) aluminum (Alq 3 ). PL studies from the edges and top surface ...

[ Research paper thumbnail of Studies on the fluorescence properties of conjugated polymer poly[2-methoxy-5-(3′,7′-dimethyloctyloxy)-1,4-phenylenevinylene in presence of nitrogen dioxide gas](https://attachments.academia-assets.com/118069505/thumbnails/1.jpg)

physica status solidi (a), 2009

1 AIARS (Materials and Devices), Amity University, Sector 125, Noida, UP, 201303, India 2 Instrum... more 1 AIARS (Materials and Devices), Amity University, Sector 125, Noida, UP, 201303, India 2 Instrument Design Development Centre, Indian Institute of Technology Delhi, Hauz Khas, New Delhi, 110016, India 3 Center for Organic Electronics, National Physical Laboratory, Dr. KS ...

Optics Communications, 1993

Experimental verification of the theoretical prediction by Mandel [J. Opt. Soc. Am. 51 (1961) 134... more Experimental verification of the theoretical prediction by Mandel [J. Opt. Soc. Am. 51 (1961) 1342] on spectral changes in a superposition experiment has been carried out. It has been shown that when the condition for interference Delta vT 1 Delta v is the band width of the spectral profile and T is the time delay between the two interfering beams)