Faculty Profiles - PANDEY Shyam sudhir

Papers - PANDEY Shyam sudhir

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Synthesis and Characterization of Newly Designed and Highly Solvatochromic Double Squaraine Dye for Sensitive and Selective Recognition towards Cu2+ Reviewed

Linjun Tang, Shubham Sharma, Shyam S Pandey

Molecules ( MDPI ) 27 ( 19 ) 6578 2022.10

Authorship：Last author,　Corresponding author Language：English Publishing type：Research paper (scientific journal)

Synthesis and characterization of a novel and zwitterionic double squaraine dye (DSQ) with a unique D-A-A-D structure is being reported. Contrary to the conventional mono and bis-squaraine dyes with D-A-D and D-A-D-A molecular frameworks reported so far, DSQ dye demonstrated strong solvatochromism allowing for the multiple ion sensing using a single probe by judicious selection of the suitable solvent system. The DSQ dye exhibited a large solvatochromic shift of about 200 nm with color changes from the visible to NIR region with metal ion sensitivity. Utilization of a binary solvent consisted of dimethylformamide and acetonitrile (1:99, v/v), highly selective detection of Cu2+ ions with the linearity range from 50 μM to 1 nM and a detection limit of 6.5 × 10−10 M has been successfully demonstrated. Results of the Benesi–Hildebrand and Jobs plot analysis revealed that DSQ and Cu2+ ions interact in the 2:1 molecular stoichiometry with appreciably good association constant of 2.32 × 104 M−1. Considering the allowed limit of Cu2+ ions intake by human body as recommended by WHO to be 30 μM, the proposed dye can be conveniently used for the simple and naked eye colorimetric monitoring of the drinking water quality.

DOI： https://doi.org/10.3390/molecules27196578

Other Link： https://www.mdpi.com/1420-3049/27/19/6578

Electronic versus Ionic Electroactive Polymers (EAPs) Strain Sensors for Wearable Electronics: A Comparative Study Reviewed

Nitin Kumar Singh, Kazuto Takashima, Shyam Sudhir Pandey

Engineering Proceedings ( Multidisciplinary Digital Publishing Institute ) 21 ( 1 ) 2022.08

Authorship：Last author,　Corresponding author Language：English Publishing type：Research paper (international conference proceedings)

Electroactive polymer (EAP) strain sensors have gained appreciable attention as a potential candidate for their application in the area of soft electromechanical devices and have been widely used in soft robotics, healthcare, augmented reality, and wearable devices. In this research, a systematic comparison has been made by fabricating the electronic and ionic types of capacitive EAP strain sensors. To accomplish this, a combination of silicone rubber sandwiched between silver-coated stretchable fabric electrodes is used as an electronic type of EAP sensor, while a conducting and stretchable freestanding film consisting of Styrene-ethylene-butylene-styrene (SEBS) rubber and dedocyl benzene sulfonate acid (DBSA) doped polyaniline composite film sandwiched between carbon grease electrodes is chosen as an ionic type of EAP sensor. Mechanical characterization in terms of the uniaxial tensile testing was …

DOI： https://doi.org/10.3390/engproc2022021001

Other Link： https://www.mdpi.com/2673-4591/21/1/1

Fabrication, characterization and modelling of the fabric electrode-based highly stretchable capacitive strain sensor Reviewed

Nitin Kumar Singh, Kazuto Takashima, Shyam S Pandey

Materials Today Communications ( Elsevier ) 32 104095 2022.07

Authorship：Last author,　Corresponding author Language：English Publishing type：Research paper (scientific journal)

Highly stretchable and capacitance-based strain sensors were fabricated utilizing highly stretchable silicone elastomer as dielectric film sandwiched between the conducting and stretchable cloth-based top and bottom electrodes. Electromechanical characterizations for the proposed sensor after multiple and reversible loading and unloading cycles up to 150% applied strain were conducted followed by the modelling of the sensing performance. It has been shown that the sensor exhibits reproducible electromechanical performance under multiple reversible stretching and relaxation cycles. There was a very small deviation (< 10%) in the observed values of the capacitance upon the applied strain of 150% up to the 1000 loading and unloading cycles. Tensile measurement for the sensor under various applied strains, not only exhibits almost constant force indicating negligible Mullins effect and negligible time-dependent changes at a fixed strain up to 100% suggesting that viscoelastic losses can also be neglected. From uniaxial tensile experiments, constitutive model of the dielectric elastomer sensor was validated. For the fitting of the experimental data obtained from the uniaxial tensile measurement, a variety of strain energy formulations have been compared for predicting the constitutive behaviour of sensor using the Mooney– Rivlin, Neo-Hookean, Yeoh and Ogden models, where 2nd term of the Ogden model was found to explain the experimental tensile data most accurately. To explain some observed losses at 150% of applied strain, the Prony series-based time dependent model was used for predicting stress at any value of time and it was found that experimental data was well fit with 4th order of Prony series.

DOI： https://doi.org/10.1016/j.mtcomm.2022.104095

Other Link： https://www.sciencedirect.com/science/article/pii/S2352492822009473

Fabrication and Characterization of Oriented Thin Films of DPP-based Conjugated Copolymer Prepared by Friction Transfer Method Reviewed

Yuki Kurokawa, Ajendra K Vats, Shuichi Nagarnatsu, Shyam S Pandey

IEEE Explore ( IEEE ) 124 - 127 2022.07

Authorship：Last author,　Corresponding author Language：English Publishing type：Research paper (international conference proceedings)

Japan http://www.amfpd.jp/ 2022.07.05 - 2022.07.08

DOI： 10.23919/AM-FPD54920.2022.9851297

Other Link： http://www.amfpd.jp/

Tear strength estimation of electroactive polymer-based strain sensors Reviewed

Nitin Kumar Singh, Kazuto Takashima, Shyam Sudhir Pandey

Electroactive Polymer Actuators and Devices (EAPAD) XXIIV ( SPIE ) 12042 424 - 428 2022.04

Authorship：Last author,　Corresponding author Language：English Publishing type：Research paper (international conference proceedings)

USA https://www.spiedigitallibrary.org/conference-proceedings-of-spie/12042/1204217/Tear-strength-estimation-of-electroactive-polymer-based-strain-sensors/10.1117/12.2627807.short

Electroactive polymer-based sensors are subjected to repeated loading and unloading cycles under variable applied strains and estimation of the tear strength plays a critical role in determining durability. A trouser type of specimen made from conducting and stretchable freestanding films consisting of SEBS rubber and dodecyl benzenesulfonic acid (DBSA) doped polyaniline composite was used for fabricating the capacitive strain sensor and tear strength estimation. Strain energy density for the composite film was calculated from the tear test data aiming towards the prediction of the life of the specimen. Our results revealed a very high value (150 newton/mm) of tear strength, leading to the sustainability of the film up to millions of cycles.

DOI： https://doi.org/10.1117/12.2627807

Other Link： https://www.spiedigitallibrary.org/conference-proceedings-of-spie/12042/1204217/Tear-strength-estimation-of-electroactive-polymer-based-strain-sensors/10.1117/12.2627807.short

Computational molecular design of NIR dyes with varying anchoring groups for improving the efficiency and stability of dye-sensitized solar cells Reviewed International journal

Pandey S.S., Vats A.K., Tang L., Hayase S.

Japanese Journal of Applied Physics 61 ( SB ) SB1021-1 - SB1021-11- 2022.01

Charge transfer and catalytic properties of various PEDOTs as Pt-free counter electrodes for dye-sensitized solar cells Reviewed International journal

Yuki Kurokawa, Ajendra Kumar Vats, Takehito Kato, Suhaidi Shafie, Shyam S. Pandey

Japanese Journal of Applied Physics 61 ( SB ) SB1010-1 - SB10110-6 2022.01

Recent progress in the macroscopic orientation of semiconducting polymers by floating film transfer method, Reviewed International journal

Manish Pandey, Vipul Singh, Chandan Kumar, Shyam S. Pandey, and Masakazu Nakamura

Japanese Journal of Applied Physics 61 ( SB ) SB0801-1 - SB0801-12 2022.01

Bifacial dye-sensitized solar cells utilizing green colored NIR sensitive unsymmetrical squaraine dye Reviewed International journal

Suraya Shaban, Pritha Roy, Ajendra K. Vats and Shyam S. Pandeyy

Japanese Journal of Applied Physics 61 ( SB ) SB1005-1 - SB1005-6 2022.01

A COMPARATIVE STUDY OF GRAPHENATED-CARBON NANOTUBES COTTON AND CARBON NANOTUBES AS CATALYSTS FOR COUNTER ELECTRODE IN DYE-SENSITIZED SOLAR CELLS Reviewed International journal

Yusnita Yusuf, Suhaidi Shafie, Ismayadi Ismail, Fauzan Ahmad, Mohd Nizar Hamidon, Shyam S Pandey, Nazalea Yazmin Muhammad, Wei Lei

Malaysian Journal of Microscopy 2021.12

Language：English Publishing type：Research paper (scientific journal)

This work reports a comparative study of synthesized graphenated-carbon nanotubes cotton (g-CNTC), standard carbon nanotubes (CNTP), and conventional platinum (Pt) thin layer which are employed as the counter electrodes in dye-sensitized solar cells (DSSC). The g-CNTC was synthesized via the floating-catalyst chemical vapor deposition (FCCVD) method. Subsequently, the g-CNTC was made into a uniform paste and deposited for the counter electrode layer. The results obtained from FESEM/TEM, Raman spectroscopy, CV and I-V measurements respectively exposed the structural, graphitization and I-V characteristics. Briefly, the morphology of g-CNTC showed the growth of graphene foliates out-sidewalls of CNT with a diameter of 40 nm. The graphitization of g-CNTC showed two dominant peaks namely the D (1355 cm-1) and G (1608 cm-1) bands with strong intensities. The g-CNTC counter electrode provided good electrical conductivity (3.66×10-3 to 6.45×10-3 S/cm), which is a significant feature to employ counter electrodes to enhance DSSC performance. In addition, the g-CNTC counter electrode offered an excellent catalytic activity for iodide/triiodide reaction and exhibited 3.49 % of photovoltaic conversion energy, which was much higher compared to CNTP (2.93 %) and platinum (3.12 %), respectively.

Other Link： https://malaysianjournalofmicroscopy.org/ojs/index.php/mjm/index

Highly sensitive organic phototransistors fabricated from PCPDTBT: PCBM blend Reviewed International journal

Yadav N., Kumari N., Ando Y., Pandey S.S., Singh V.

Journal of Physics: Conference Series 2070 ( 1 ) 2021.11

Implication of color of sensitizing dyes on transparency and efficiency of transparent dye-sensitized solar cells Reviewed International journal

Roy P., Vats A.K., Tang L., Pandey S.S.

Solar Energy 225 950 - 960 2021.09

Investigation of Orientation in the Thin Films of Conjugated Polymer and NIR Dye Blends Fabricated by Friction Transfer Method Reviewed

Yuki Kurokawa, Shuichi Nagamatsu, Shyam S Pandey

IEEE Explore ( IEEE ) 2021.08

Language：English Publishing type：Research paper (international conference proceedings)

Japan Conference: 28th International Workshop on Active Matrix, Flatpanel Displays and Devices (AM-FPD21)A 2021.06.29 - 2021.07.02

Improved film's crystallinity and facile charge transport has been well demonstrated by orienting conjugated polymers using solution based thin film fabrication followed by thermal annealing, need for huge halogenated solvents and high temperature annealing are stumbling block for industrially viable large area thin film fabrication. Herein, we report the fabrication of oriented thin films regioregular P3HT by solvent-free friction transfer (FT) technique and enhancement its further enhancement by adding NIR sensitive squaraine dyes. Apart from assisting the molecular orientation of P3HT, it has been demonstrated that dye molecules are also get oriented and a synergistic match between the alkyl chains of the polymer and dye molecule leads to promotion for the extent of the molecular orientation in the dye molecules.

DOI： 10.23919/AM-FPD52126.2021.9499214

Other Link： https://ieeexplore.ieee.org/document/9499214

Extreme Orientational Uniformity in Large-Area Floating Films of Semiconducting Polymers for Their Application in Flexible Electronics Reviewed

Manish Pandey, Heriyanto Syafutra, Nikita Kumari, Shyam S. Pandey, Ryo Abe, Hiroaki Benten, and Masakazu Nakamura

ACS Applied Materials & Interfaces ( American Chemical Society ) 2021.08

Language：English Publishing type：Research paper (scientific journal)

Layer-by-layer fabrication of uniformly oriented thin films over large areas by cost-effective solution-based approaches can open new horizons for the realization of high-performance organic circuits in various applications. In this work, fabrication of a large-area ≈40 cm2 film with uniform orientation is reported for poly(3,3‴-dialkylquaterthiophene) (PQT) using a unidirectional floating film transfer method (UFTM). Orientation characteristics and charge transport anisotropy were analyzed using polarized UV–vis spectral mapping and fabrication of bottom-gated organic field-effect transistors (OFETs) from different regions. Films were found to be highly oriented with an optical dichroic ratio of ca. 15. Orientation characteristics reveal that films were highly oriented along the width of the film, covering >70% of the area, and angle-dependent field-effect mobilities are in good agreement with the orientation of the polymer backbones. These highly oriented films resulted in charge transport anisotropy of 8.9. An array of bottom-gated OFETs fabricated along the length of single large-area (≈15 × 2.5 cm2) thin film demonstrated the average field-effect mobility of 0.0262 cm2/(V s) with a very narrow standard deviation of 12.6%. We also demonstrated that film thickness can be easily tuned from 5.6 to 45 nm by increasing the PQT concentration, and field-effect mobility is highly reproducible even when the film thickness is 10 nm. Microstructural characterization of the thus-prepared large-area thin films revealed the edge-on stacked polymer backbones and surface roughness of <1 nm as probed by grazing incidence X-ray diffraction and atomic force microscopy, respectively. Flexible OFETs with bottom-gate top-contact geometry were also fabricated, having average field-effect mobility of 0.0181 cm2/(V s). There was no considerable change in mobility after bending the flexible devices at different radii.

DOI： 10.1021/acsami.1c09671

Other Link： https://pubs.acs.org/doi/abs/10.1021/acsami.1c09671

Assisted alignment of conjugated polymers in floating film transfer method using polymer blend Reviewed

Heriyanto Syafutra, Manish Pandey, Nikita Kumari, Shyam S Pandey, Hiroaki Benten, Masakazu Nakamura

Thin Solid Films ( Elsevier ) 734 138814(1) - 138814(8 2021.07

Language：English Publishing type：Research paper (scientific journal)

Orientating conjugated polymers (CPs) in thin films is an attractive technique for obtaining anisotropic properties, resulting in improved device performances. Template-assisted alignment using pre-patterned substrates has been widely used to orient various polymers irrespective of their orientation capability. In this work, we report that using the floating film transfer method, the orientation of guest polymers can be in-situ assisted via blending with a host polymer during film fabrication. Dichroic Ratio (DR) of two guest CPs such as poly[2,5-(2-octyldodecyl)-3,6-diketopyrrolopyrrole-alt-5,5-(2,5-di(thien-2-yl)thieno[3,2-b]thiophene)] and poly(9,9-di-n-octylfluorenyl-2,7-diyl) were found to be enhanced when blended with host polymer poly(3,3‴-didodecyl-quaterthiophene) (PQT). DR of the host PQT decreases monotonically with an increase in the guest polymer proportion, suggesting that guest polymers are well mixed in the host matrix. The electronic absorption spectra and atomic force microscopy results revealed that blended polymers were well mixed without any phase separation. DR of the guest polymers in the blend was the same even when the overall blend concentration was increased twice to increase the overall film thickness.

DOI： 10.1016/j.tsf.2021.138814

Other Link： https://www.sciencedirect.com/science/article/pii/S0040609021002972

Development of High-Sensitivity Poly (2, 7-(9, 9-dioctylfluorene)-alt-5, 5-(4', 7'-di-2-thienylbenzo [c][1, 2, 5] thiadiazole)) Thin-Film-Based Phototransistors by the Ribbon-Floating Film Transfer Method Reviewed International journal

Nidhi Yadav, Nikita Kumari, Yoshito Ando, Shyam S. Pandey, and Vipul Singh

Physica Status Solidi (RRL) - Rapid Research Letters ( WILEY-V CH VERLAG GMBH ) 2021.06

Language：English Publishing type：Research paper (scientific journal)

Alignment of polymer chains hold key to development of highly functional polymer based field effect transistors. Our recently developed ribbon-floating film transfer method (ribbon-FTM) has the potential for development of polymer thin films with highly aligned chains which are desirable for fabrication of efficient planar devices. These thin films consisting of well aligned polymer chains exhibit high degree of optical and electronic anisotropies. In this work we report ribbon-FTM processed thin film based organic photosensitive transistors of PFO-DBT. Under optimized fabrication conditions polymer FETs based on PFO-DBT demonstrated a charge carrier mobility of 0.002 cm²/Vs and an on-off ratio of 5 × 10⁴ under dark conditions. The devices have further demonstrated a Photosensitivity of ∽10⁴ and 10³ and a high Responsivity of 8.37 A/W and 4.6 A/W against green and red light illuminations, respectively. The results hold promise for development of conducting polymer based high performance photosensitive OFETs. This article is protected by copyright. All rights reserved.

DOI： 10.1002/pssr.202100185

Other Link： https://onlinelibrary.wiley.com/doi/epdf/10.1002/pssr.202100185

Probing the metal/conducting polymer interface and implications of the metal diffusion in two-terminal sandwich devices Reviewed International journal

Nidhi Yadav, Nikita Kumari, Yoshito Ando, Shyam S Pandey, Vipul Singh

Synthetic Metals ( Synthetic Metals ) 278 116797(1) - 116797(11) 2021.05

Language：English Publishing type：Research paper (scientific journal)

In this article, we have investigated the role of polymer regio-regularity and film fabrication technique in reducing metal diffusion from top electrodes in sandwich type devices. Poly(3-hexyl thiophene)(P3HT) polymer of varying regio-regularity was chosen for investigation and its corresponding thin films were fabricated by spin-coating(SC) and floating film transfer method(FTM). Sandwich devices with a top interface between gold and i) FTM coated regio-regular (rr) P3HT, ii) FTM coated non-regiocontrolled (nr) P3HT, iii) SC nr-P3HT and iv) SC rr-P3HT were fabricated. The current density vs voltage (J-V) characteristics of the devices revealed non-ohmic characteristics. Estimation of interfacial hole barrier heights using Fowler Nordheim tunneling model revealed a small barrier of 1.12 eV for the isotropic spin-coated nr-P3HT film which increased to 1.37 eV with an increase in film anisotropy for the FTM nr-P3HT film. The barrier height also gradually declined from 1.37 eV to 1.05 eV with increase in regioregularity from FTM nr-P3HT to FTM rr-P3HT. These observations were confirmed through optical and structural characterizations along with depth profiling of metal diffusion using XPS. Pronounced Au diffusion to a higher depth was observed in the XPS results for the highly anisotropic FTM film that decreased subsequently with decrease in anisotropy from FTM to spin-coated film. It was thus deduced that a judicious selection of fabrication technique and polymer aids in reducing metal diffusion leading to improved device performance. The results hold crucial significance towards the fabrication of efficient organic photodetectors that have a sandwich type device architecture.

DOI： 10.1016/j.synthmet.2021.116797

Other Link： https://www.sciencedirect.com/science/article/pii/S0379677921001028

Development of PCPDTBT thin film based highly sensitive organic phototransistors Reviewed International journal

Nidhi Yadav, Nikita Kumari, Shyam S Pandey, Vipul Singh

Materials Today' Proceeding ( Elsevier ) 2021.04

Language：English Publishing type：Research paper (international conference proceedings)

In this report, we have proposed a novel ribbon-FTM method to develop highly oriented polymer thin films. A donor–acceptor (D-A) type copolymer, PCPDTBT has been selected as the target material for investigation. The maximally oriented film showcased a DR of 4.1. Highly aligned polymer film was used as the active layer for the development of bottom gate bottom contact (BGBC) type OFETs. An average mobility and an Ion/Ioff of 0.002 cm2/Vs and 5 × 103 were obtained under dark conditions, respectively. Upon illumination with monochromatic green light (λ = 522 nm, Pin = 0.5 mW/cm2), the OPTs showcased a high photosensitivity and responsivity of 103 and 17 A/W, respectively. The obtained values were found to be superior over many of the previously reported similar OPTs which employed other organic polymers. The results thus are of crucial significance with respect to the development of facile, cost effective and highly sensitive single polymer thin film based OPTs.

DOI： 10.1016/j.matpr.2021.03.468

Other Link： https://www.sciencedirect.com/science/article/pii/S2214785321025232?via%3Dihub

Fatigue life prediction of electroactive polymer strain sensor Reviewed

Nitin Kumar Singh, Kazuto Takashima, Shyam Sudhir Pandey

Electroactive Polymer Actuators and Devices (EAPAD) XXIII ( International Society for Optics and Photonics ) 11587 115871Z(1) - 115871Z(7) 2021.03

Language：English Publishing type：Research paper (international conference proceedings)

USA Sandiego, California 2021.03.22 - 2021.03.27

Electroactive polymers strain sensors bear a great potentiality in the area of soft robotics, wearable devices, and fitness industries. A small initial defect present in such sensor may grow to a critical size during contraction and relaxation cycles leading to mechanical failure, therefore, prediction of fatigue life is inevitable. The crack growth approach is one of the amicable ways to estimate the fatigue life considering parameters like tear energy, crack geometry, and power law. In this work, crack growth approach based on power law is being proposed to predict fatigue life utilizing conducting and stretchable freestanding films consisted of SEBS rubber and dodecyl benzenesulfonic acid (DBSA) doped polyaniline composite. Utilizing this crack growth model for the prediction of fatigue life exhibited that such films can sustain more than a million cycles even at a large value of deformation.

DOI： 10.1117/12.2584521

Other Link： https://www.spiedigitallibrary.org/conference-proceedings-of-spie/11587/115871Z/Fatigue-life-prediction-of-electroactive-polymer-strain-sensor/10.1117/12.2584521.short

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Papers - PANDEY Shyam sudhir