Browsing by Author "Yadav, Kamlesh"

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BiFeO3/g-C3N4/f-CNF ternary nanocomposite as an efficient photocatalyst for methylene blue dye degradation under solar light irradiation
(Elsevier Ltd, 2023-06-21T00:00:00) Deeksha; Kour, Pawanpreet; Ahmed, Imtiaz; Haldar, Krishna Kanta; Yadav, C.S.; Sharma, Surender Kumar; Yadav, Kamlesh
The development of Perovskite oxide photocatalysts with superior dye degradation efficiency under solar light irradiation has gained attention in recent years, owing to their extraordinary flexibility, chemical composition, and tunability. Herein, we report the facile synthesis of a novel ternary composite composed of BiFeO3 (BFO) perovskite, g-C3N4, and functionalized carbon nanofibers (f-CNF), referred to as BFO/g-C3N4/f-CNF using a simple solution method as a photocatalyst to accelerate the degradation of methylene blue dye. Detailed structural and microstructural features confirm the formation of a ternary composite composed of BFO nanoparticles and f-CNFs mounted on g-C3N4 nanosheets. The photocatalytic activity of the sample for the degradation of methylene blue dye was studied in solar light using UV�visible spectroscopy. The BFO/g-C3N4/f-CNF ternary composite displays excellent photocatalytic activity with a degradation rate of 87 % after illumination for 120 min under solar light than BFO, g-C3N4, and binary composites BFO/g-C3N4 and BFO/f-CNF. The highest rate constant (k = 0.01675 min?1) for BFO/g-C3N4/f-CNF further confirms improved photocatalytic efficiency. The red shift in the UV�visible absorption spectrum of BFO/g-C3N4/f-CNF indicates a reduced band gap (1.9 eV) compared to that of pure BFO (2.28 eV) and g-C3N4 ( 2.72 eV). A decrease in the photoluminescence intensity of the ternary composite compared to that of BFO indicates the inhibition of photoexcited electron recombination which results in the availability of more charge carriers for the photocatalytic process. The enhanced efficiency of BFO/g-C3N4/f-CNF can be explained by the synergistic effect between BFO and g-C3N4 and the incorporation of f-CNF further promotes the migration rate of electrons from BFO to g-C3N4. � 2023 Elsevier B.V.
Effect of Different Ablation Time of ns-pulsed Laser on the Synthesis of Silver Nanoparticles in Liquid
(Springer Science and Business Media Deutschland GmbH, 2022-09-01T00:00:00) Paroha, Prahalad Prasad; Yogesh, Gaurav Kumar; Singh, Birendra; Yadav, Kamlesh; Tewari, Anurag
In the present report, we have studied the effect of nanosecond pulsed laser irradiation time on the particle abundance, morphology, and optical properties of silver nanoparticles (Ag-NPs). High-resolution transmission electron microscopy, selected area diffraction pattern, and UV-visible absorption spectroscopy were used to characterize morphological, structural, and optical properties of the Ag-NPs. The prolonged laser irradiation above 60�min demonstrates the melting and diffusion-induced aggregation of Ag-NPs. The statistical evaluation of various particles under different irradiation durations reveals uniform and monodispersed particle distribution for only 60�min of ablation duration. � 2022, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.
Effect of lattice defects on the structural and optical properties of Ni1 − XAgXO (where X = 0.0, 0.01, 0.03, 0.05, 0.10 and 0.15) nanoparticles
(Springer, 2018) Sharma, Rohit; Yadav, Kamlesh
The Ni1 − XAgXO (where X = 0, 0.01, 0.02, 0.03, 0.05, 0.10, and 0.15) nanoparticles are synthesized by sol–gel technique. The effects of Ag-doping in NiO nanoparticle on the structural and optical properties are studied. XRD analysis confirms that the prepared samples are single phase and oxygen deficient in nature. The unit cell volume decreases with the increase in the Ag-doping content. The crystallite size decreases from 23 to 19 nm with increasing the Ag-doping content up to X = 0.10. The strain increases with increase in Ag-doping concentration. FESEM analysis confirms that the pure sample of NiO is quasi-spherical and this shape is deformed as the Ag content increases in the NiO samples. The increase in the agglomeration of nanoparticles with the increase in doping content is also observed. UV–Visible analysis shows that the calculated optical band gap of the pure NiO sample is 3.70 eV which is less than the reported value 4.42 eV of NiO nanoparticles. The optical band gap increases as the Ag-doping content increases in the host NiO lattice. The change in band gap is increased rapidly for the X = 0.01 sample and then become slow for the rest of the samples. FT–IR analysis gives all the information regarding the functional group present in the samples. The effect of disorder created due to Ag-doping in NiO lattice leads to the formation of lattice defects and affects the structural and optical properties, which have been discussed in this paper in detail.
Effect of oxygen vacancies, lattice distortions and secondary phase on the structural, optical, dielectric and ferroelectric properties in Cd-doped Bi2Ti2O7 nanoparticles
(Elsevier Ltd, 2021-04-27T00:00:00) Anu; Yadav, Kamlesh; Gaur, Anurag; Haldar, Krishna Kanta
(Bi1-xCdx)2Ti2O7 (x = 0.00, 0.02, 0.04, 0.06, 0.08, 0.10 and 0.12) nanoparticles are synthesised using the co-precipitation method. The prepared samples show pyrochlore phase formation except for x = 0.02 and 0.08, where Bi4Ti3O12 appears as a secondary phase. The crystallite size and unit cell volume decrease while the strain and dislocation density increase with an increase in Cd-doping. The vibrational bands corresponding to Cd?O and C[dbnd]O are red-shifted, while the H[sbnd]O[sbnd]H bending band is blue-shifted with increasing Cd-doping. The band gap energy for x = 0.00 is found to be 1.78 eV. It increases with an increase in �x� up to 0.06 and then decreases with a further increase in �x� except for x = 0.02 and x = 0.08. The impedance data show non-Debye type relaxation. The pyrochlore phase is found to be non-ferroelectric. However, the samples with x = 0.02 and x = 0.08 having the secondary phase (Bi4Ti3O12) are ferroelectric. � 2021 Elsevier Ltd
Effects of Dy3+-doping on the band-gap widening and formation of mixed cubic and monoclinic phases of Sm2O3 nanoparticles
(Springer Science and Business Media Deutschland GmbH, 2023-10-30T00:00:00) Sain, Rachana; Roy, Ayan; Kumar, Ajay; Anu; Deeksha; Kour, Pawanpreet; Singh, Ravi Pratap; Yadav, Kamlesh
We synthesized Sm2?xDyxO3 (where X = 0.00, 0.03, 0.06, 0.09, and 0.12) nanoparticles using a co-precipitation method and investigated their structural and optical properties. X-ray diffraction (XRD) results reveal that Dy3+-doping in Sm2O3 nanoparticles leads to the formation of a monoclinic polymorphic phase along with the cubic phase of Sm2O3 and its fraction increases with increasing Dy3+-doping concentration. The substitution of Dy3+ at the Sm3+ site converts the cubic Sm2O3 unit cells into distorted monoclinic Sm2?XDyXO3 unit cells. The average crystallite and nanoparticle sizes decrease with increasing Dy3+-doping concentration. Dy3+-ions act as particle size inhibitors, which is attributed to an increase in the segregation of Dy3+-dopant ions at the surface of the nanoparticles with increasing Dy3+-doping content. The peak appearing at 851�cm?1 in the Fourier transform infrared spectroscopy (FTIR) spectra confirms the formation of Sm2O3. Widening of the band gap (Eg) above the band gap of pure cubic Sm2O3 with Dy3+-doping concentration has been observed for X > 0.06, which is due to the Moss-Burstein and quantum size effects. � 2023, The Author(s), under exclusive licence to Springer-Verlag GmbH, DE part of Springer Nature.
Effects of Interfacial Interactions and Nanoparticle Agglomeration on the Structural, Thermal, Optical, and Dielectric Properties of Polyethylene/Cr2O3 and Polyethylene/Cr2O3/CNTs Nanocomposites
(Springer, 2022-11-22T00:00:00) Gupta, Jaya; Kumar, Ajay; Roy, Ayan; Anu; Deeksha; Kour, Pawanpreet; Singh, Ravi Pratap; Yogesh, Gaurav Kumar; Yadav, Kamlesh
In this report, we have synthesized the binary and ternary phase nanocomposites [(polyethylene (PE)1?X/(Cr2O3)x) and (PE)1?X/(Cr2O3)X/CNTs (where X = 0,�2%, 4%, 6%, 8%, and 10%)] using the melt mixing method and studied the structural, optical, thermal and dielectric properties with an increase in Cr2O3 nanofiller concentration. Our results show an increase in interfacial interactions between Cr2O3 nanofiller and PE matrix with an increase in nanofiller concentration up to X = 6%. After that, the interactions decreased with a further increase in X because of the increase in the size of the Cr2O3 nanoparticle aggregates. Incorporating 2% carbon nanotubes (CNTs) into (PE)1?X/(Cr2O3)X nanocomposites, further decreases the interactions between the Cr2O3 nanofiller and the PE matrix. � 2022, The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.
Effects of interfacial interactions on structural, optical, thermal degradation properties and photocatalytic activity of low-density polyethylene/BaTiO3 nanocomposite
(Elsevier Ltd, 2023-04-10T00:00:00) Roy, Ayan; Panda, Sambit; Gupta, Jaya; Anu; Singh, Ravi Pratap; Deeksha; Kour, Pawanpreet; Sharma, M.P.; Yadav, Kamlesh
Barium titanate (BaTiO3) filled low density polyethylene (LDPE), (LDPE)100?x/(BaTiO3)x (where x = 0, 2, 4, 6 and 10) nanocomposites are prepared via a solvent-free melt-mixing method. The effects of nano-sized BaTiO3 (nBT) on the structural, optical and thermal degradation properties of LDPE are investigated to address the qualitative interfacial interaction effects due to the spatial distribution of nBT particles in the LDPE matrix. X-ray diffraction (XRD) results confirm the uniform dispersion of nBT nano-fillers in the LDPE polymer matrix. The crystallite size of LDPE increases with increasing the nBT content. Fourier transform infrared spectroscopy (FTIR) results indicate the enhancement in interfacial physical interactions between the polymer and nano-fillers with increasing nano-filler content. The band gap energy of the nanocomposites decreases with increasing nano-filler content, which suggests chemical imperfections close to the interfaces. DSC results depict higher Tm values for the composites which is attributed to the heterogeneous nucleating effects of the nBT particles. Thermo-gravimetric analysis (TGA) results indicate an increase in the decomposition temperature (TD), thermal stability and good dispersibility probability of nBT with increasing nBT. The photocatalytic decomposition of MB is highest (73.52%) for the 10% nBT incorporated LDPE nanocomposite sample. These results correlate with the effect of the interfacial interactions between the nBT fillers and the LDPE polymer matrix. � 2023 Elsevier Ltd
Electrochemical performance of mixed-phase 1T/2H MoS2 synthesized by conventional hydrothermal v/s microwave-assisted hydrothermal method for supercapacitor applications
(Elsevier Ltd, 2022-07-05T00:00:00) Kour, Pawanpreet; Deeksha; Yadav, Kamlesh
Mixed-phase 1T/2H MoS2 has been receiving immense attention as an electrode material for supercapacitors due to the synergistic effects of both the phases. Herein, we synthesized mixed-phase 1T/2H MoS2 via two different techniques: conventional hydrothermal (HT) and microwave-assisted hydrothermal (MHT) technique. The formation of MoS2 is confirmed through X-ray diffraction pattern, scanning electron microscopy, energy dispersive X-ray spectroscopy, Raman-spectra, and X-ray photoelectron spectra. The electrochemical performance of the two samples is investigated using cyclic voltammetry (CV), Gravimetric charging-discharging (GCD) and electrochemical impedance spectroscopy (EIS). MoS2 synthesized via MHT method (MS-MW) and HT method (MS-HT) deliver capacitances of 421 F g?1 and 742 F g?1 at 5 mV s?1, respectively. The energy density of MS-HT (57 Wh kg?1) is almost double than that of MS-MW (30 Wh kg?1). MS-HT also exhibited remarkable capacitance retention of 91% over 1200 cycles, compared with MS-MW. The results demonstrate that MoS2 synthesized by the hydrothermal method delivers superior electrochemical performance. � 2022 Elsevier B.V.
LaCoO3Perovskite Nanoparticles Embedded in NiCo2O4Nanoflowers as Electrocatalysts for Oxygen Evolution
(American Chemical Society, 2022-11-08T00:00:00) Kubba, Deeksha; Ahmed, Imtiaz; Kour, Pawanpreet; Biswas, Rathindranath; Kaur, Harpreet; Yadav, Kamlesh; Haldar, Krishna Kanta
It is essential to design high-efficiency, stable, and inexpensive electrocatalysts for the oxygen evolution reaction (OER). We fabricate a hybrid system of perovskite LaCoO3 with spinel NiCo2O4 denoted LaCoO3/NiCo2O4 via an in situ hydrothermal process. In situ incorporation of LaCoO3 nanoparticles on the NiCo2O4 nanoflower surface is confirmed by field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) images. Benefiting from the interface engineering, the obtained LaCoO3/NiCo2O4 hybrid nanoflowers exhibit the lowest overpotential of 353 at a current density of 10 mA/cm2 and a small Tafel slope of 59 mV/dec in alkaline media compared with pristine LaCoO3 (401 mV, 116 mV/dec) and NiCo2O4 (386 mV, 73 mV/dec). The optimized sample possesses a higher electrochemical surface of 111.45 cm2 than LaCoO3 perovskite (35.37 cm2) and NiCo2O4 spinel oxide (61.37 cm2) structures. The enhanced OER performance of the LaCoO3/NiCo2O4 composite structure is due to the accumulation of LaCoO3 nanoparticles over NiCo2O4 petals, which introduces a substantial number of electrochemically active sites for the catalysis process to promote charge and mass transport. In addition to this, LaCoO3/NiCo2O4 exhibits long-term stability over 20 h. Thus, it is believed that the excellent OER activity of the LaCoO3/NiCo2O4 composite structure is associated with strong interaction between LaCoO3 and NiCo2O4 as well as a large surface area and a unique flower structure. � 2022 American Chemical Society.
Mixed-phase MoS2 nanosheets anchored carbon nanofibers for high energy symmetric supercapacitors
(Elsevier Ltd, 2023-03-14T00:00:00) Kour, Pawanpreet; Deeksha; Kour, Simran; Sharma, A.L.; Yadav, Kamlesh
Mixed-phase MoS2 (MS) nanosheets anchored carbon nanofibers (CNFs) have been synthesized via a hydrothermal route. The concentration of CNFs has been varied in the MS/CNF-x composite (where, x = 1, 1.5, 2, and 3 represents the molar concentration of CNFs) to investigate the impact of CNFs on the electrochemical behavior of the material. The incorporation of CNFs offers a conductive path for the diffusion of ions and provides structural support which limits the restacking of the MoS2 layers during the charging/discharging. The MS/CNF-2 composite delivered superior electrochemical performance compared with the other composites owing to the positive synergy between MoS2 and CNFs. The specific capacitance manifested by MS/CNF-2 (626.08 F g?1 at 1 A g?1) is about four times that of pristine MS (159.35 F g?1). It is also observed that MS/CNF-2 exhibited higher electrochemical stability than pristine MS. Furthermore, the symmetric supercapacitor (SSC) device achieved a tremendous energy density of 42.6 Wh kg?1 at 2.4 kW kg?1. To test its practical applicability, LEDs of different color (red, green, and blue) have been illuminated using a series combination of three symmetric electrode cells. The red, green, and blue LEDs lighted up for 15 mins, 7 mins, and 3 mins. The results demonstrate the superiority of the MS/CNF composite for symmetric supercapacitors. � 2023
MoS2-based core-shell nanostructures: Highly efficient materials for energy storage and conversion applications
(Elsevier Ltd, 2023-04-19T00:00:00) Kour, Pawanpreet; Deeksha; Kour, Simran; Sharma, A.L.; Yadav, Kamlesh
Molybdenum disulfide (MoS2) has acquired immense research recognition for various energy applications. The layered structure of MoS2 offers vast surface area and good exposure to active edge sites, thereby, making it a prominent candidate for lithium-ion batteries (LIBs), supercapacitors (SCs), and hydrogen evolution reactions (HERs). However, the limited conductivity, less number of active sites, and structural instability of MoS2 during continuous electrochemical cycling hinder its applications. In this regard, the formation of core-shell structures has been evolving as a prominent approach to uplift the electrochemical/electrocatalytic activity of MoS2 for energy-based applications. The unique core-shell composites of MoS2 with different electro-active materials exhibit superior electrochemical and electrocatalytic properties on account of the synergy of the core and the shell materials. These materials offer huge active area, high conductivity, an easy pathway for charge diffusion, and stable cyclic life leading to their outstanding electrochemical activity. In this review, various core-shell structures of MoS2 with carbon, metal oxides/sulfides, and conducting polymers are discussed for LIBs, SCs, and HERs. The function of core and shell materials in elevating the electrochemical activity of MoS2 based core-shell composites have been explored in detail. The effect of doping of core and shells on the performance of the composite has also been elucidated. The doped MoS2 based core-shell composites manifest tremendous electrochemical performance compared to the un-doped counterpart. Thus, these unique structured core-shell composites are regarded as futuristic candidates for energy storage and conversion systems. � 2023
Optical properties of nanocrystallite films of ?-Fe2O3 and ?-Fe2-xCrxO3 (0.0 ? x ? 0.9) deposited on glass substrates
(Institute of Physics Publishing, 2017) Kumar, Ajay; Yadav, Kamlesh
?-Fe2O3 films are deposited on fluorine-doped tin oxide (FTO) and indium-doped tin oxide (ITO) substrates for 1, 4 and 6 min using a spray pyrolysis technique. We also deposited ?-Fe2-xCrxO3 (x = 0.0, 0.1, 0.2, 0.3, 0.4, 0.7 and 0.9) films on the FTO substrate for a deposition time of 35 s. The structural and optical properties of these films were then studied. The x-ray diffraction (XRD) patterns show that all the films are crystalline in nature with a hexagonal crystal structure. The average grain size and unit cell volume were calculated using XRD data. It is found that the average grain size and unit cell volume increase with an increasing film thickness and Cr-doping concentration. The value of strain decreases with an increasing film thickness and Cr-doping content. It is also found that films with the same deposition time on the ITO substrate are more crystalline than on the FTO substrate. Furthermore, the average grain size is obtained from field emission scanning electron microscopy (FESEM) images. FESEM analysis confirms that the average grain size increases with the film thickness and Cr-doping concentration. The optical absorption spectra of the films show that the absorbance increases with an increasing deposition time and Cr concentration. The energy band gap (Eg) of all the films has been calculated using Tauc's relation. A narrowing of the band gap was observed with an increase in film thickness and Cr-doping content. The reduction of the band gap with the increase in film thickness of the films deposited on the ITO substrate is larger than for the film deposited on the FTO substrate. The refractive index is also obtained from the absorption spectra of the films using the Moss relation: n = 4 (k/Eg), where k =108 eV. The refractive index decreases with an increase in the optical band gap. The band gaps of the films are also calculated from the FTIR spectra. This is in good agreement with the UV data. The correlation between the structural and optical properties of the deposited films has been discussed.
Probing the impact of bismuth-titanate based nanocomposite on the dielectric and electro-optical features of a nematic liquid crystal material
(Elsevier B.V., 2021-12-22T00:00:00) Varshney, Depanshu; Anu; Prakash, Jai; Pratap Singh, Vinay; Yadav, Kamlesh; Singh, Gautam
We report here the concentration and temperature dependent optical, electro-optical and dielectric studies on bismuth titanate (Bi2Ti2O7/Bi4Ti3O12) nanocomposite (BT2/BT4 NC, ?42 nm) doped nematic liquid crystal (NLC, 5CB) mixtures using optical polarising microscope and dielectric spectroscopic techniques. The optical textures confirm the uniform dispersion and miscibility of NCs in 5CB for all concentrations (i.e. 0.1, 0.25, 0.5, 1 and 2 wt%) and mixtures appear to be almost agglomeration free. The dielectric studies demonstrate the maximum changes in the dielectric parameters (dielectric permittivity, dielectric loss, loss factor and dielectric anisotropy) of 5CB sample for the 0.1 wt% mixture. Interestingly, the dielectric anisotropy of 5CB in 0.1 wt% mixture is increased by ? 11%. However, the dielectric memory effect (bias voltage ON-OFF) is observed maximum in the case of 1 wt% mixture. Similarly, the optical memory examined by bias voltage dependent (ON-OFF) optical textures is also significantly enhanced for 1 wt% mixture. The significant changes observed in dielectric properties of 5CB sample could be due to plausible interaction among NLC molecules and ionic impurities with BT2/BT4 NCs. Moreover, the enhanced volatile memory in BT2/BT4 NC-NLC mixture could be attributed to the dipole�dipole coupling between individual permanent dipole moment of anisotropic NLC molecules with the dipole moments generated by the ionic impurities agglomerated on the surface of high dielectric BT2/BT4 NCs. We strongly believe that such NCs-NLC mixtures would be certainly useful in the advancement of wearable devices (such as smart plenoptic cameras, watches etc.) and smart switchable windows. � 2021 Elsevier B.V.
Synergistic improvement in electrochemical performance of Cr-doped MoS2/CuCo2S4 binary composite for hybrid supercapacitors
(Elsevier Ltd, 2023-10-31T00:00:00) Kour, Pawanpreet; Kour, Simran; Deeksha; Sharma, A.L.; Yadav, Kamlesh
The synergistic effect of transition metal doping and composite formation can be imperative to improve the limited conductivity and inferior cyclic stability of MoS2 for supercapacitors. In this work, firstly, the impact of Cr-doping on the electrochemical activity of MoS2 has been discussed. Afterwards, the optimized Cr-doped MoS2 (CrMS-5) sample has been combined with CuCo2S4 (CCS) to further enhance its charge storage ability and cyclic stability. The CrMS-5/CCS composite delivers tremendous electrochemical activity as an electrode with a specific capacity of approximately 1324.08 C g?1 at 4 A g?1. The outstanding performance of the doped binary composite is on account of the synergism between doping and composite formation that results in increased conductivity and numerous redox active sites for charge storage. Furthermore, a symmetric supercapacitor device (SSC) has been fabricated using a CrMS-5/CCS electrode. It attains a high energy density of 46.63 Wh kg?1 corresponding to 1 kW kg?1 of power and exhibits remarkable cyclic stability of 81% for up to 5,000 cycles. The device illuminates a star-shaped LED panel of 12 red LEDs for 30 min. Thus, the above outcomes demonstrate the superiority of the doped MoS2-based composites for high-energy symmetric supercapacitors. � 2023 Elsevier Ltd
Synethesis and charcterization of nanocomposites
(Central University of Punjab, 2016) Thakur, Priya; Yadav, Kamlesh
The Internet is global in scope and rapidly growing. With this growth, internet security threats are also increasing. The Internet is the global information exchange media, which is open and insecure, needs more and better security provision. In the era of computer network virtually all business, government and academic organizations interconnect their local area network with a collection of interconnected networks. Data transmission in a public communication system is not secure because of interception and improper manipulation by an opponent. Therefore, the attractive solution for this problem is steganography, which is the art and science of writing concealed messages in such a way that no one, apart from the sender and intend recipient, can notice the existence of the message. Thus, confidentiality and integrity principle of security can be achieved. There have been wide ranges of algorithms introduced using a text file as cover media. This thesis explains a two layered hiding technique that provides high security than other techniques. The use of local language ensures more security to the information exchange as the awareness of the local language is limited. The proposed approach uses the local language Punjabi as cover text. In proposed approach, the cover media is pre-existing media, not system generated media. Therefore, a user will be free to use the cover media taken from any Punjabi newspaper, magazine or book and the syntax of a sentence and sequence of sentence both will be true grammatically. Even though the opponent has a very good command on the Punjabi language, they will not found any suspicious
Synthesis and characterization of iron oxide nanoparticles
(Central University of Punjab, 2016) Singh, Gurdhir; Yadav, Kamlesh
Chickpea is self pollinated legume crop which was believed firstly originated in South-Eastern Turkey and parts of Syria. Chickpea is the second most important pulse crop in the world. In Northern India, chickpea is grown in winter season. Preconditioning the plant with mild drought stress may trigger the various signaling pathways which will prepare the plants to conquer lethal cold stress. In this study, PBG1, PBG5 and GPF2 variety are more sensitive to the chilling stress, which were preconditioned with mild drought stress and then exposed to lethal cold stress. To see the effect of preconditioning various cell responses were monitored by measuring ELI, Relative Water Content and chlorophyll content at different stages of chickpea. All genotypes generated a variable response. Overall, relative water content and chlorophyll content were significantly higher in preconditioned PBG1, GPF2 and PBG5, which are sensitive to chilling stress. The study showed increase tolerance capacity in preconditioned plant towards chilling temperature and improve tolerance against chickpea.
Thickness-dependent magnetic and transport properties of La0.5Sr0.5MnO3 thin films deposited by DC magnetron sputtering on the LaAlO3 substrate
(Springer Verlag, 2018) Yadav, Kamlesh; Singh, H. K.; Maurya, K. K.; Varma, G. D.; Yadav, K.; Singh, H.K.; Maurya, K.K.; Varma, G.D.
Thickness-dependent structural, magnetic and transport properties of La0.5Sr0.5MnO3 (LSMO) thin films have been studied. A series of the LSMO films with thickness 30, 60, 125 and 300?nm have been deposited on the LaAlO3 substrate using DC magnetron sputtering. The paramagnetic to ferromagnetic transition at TC is followed by antiferromagnetic ordering at TN in all films. It is also found that all LSMO films have TC lower than that of bulk LSMO. A small variation of TC is observed on increasing the film thickness. However, TN is found to rise with increase in the film thickness. The 60?nm-thick film shows a wide insulator to metal transition. The resistivity above 240?K of the films with various thicknesses is consistent with a small polaronic hopping conductivity. The polaronic formation energy EA rises with the increase of the film thickness except for 60?nm thin film, where a small decline in EA is observed. The correlation between observed structural, magnetic and electrical properties with the thickness of the films has been discussed in this paper. ? 2017, Springer-Verlag GmbH Germany, part of Springer Nature.
Transition Metal-based Perovskite Oxides: Emerging Electrocatalysts for Oxygen Evolution Reaction
(John Wiley and Sons Inc, 2023-01-23T00:00:00) Deeksha; Kour, Pawanpreet; Ahmed, Imtiaz; Sunny; Sharma, Surender Kumar; Yadav, Kamlesh; Mishra, Yogendra Kumar
Development of clean and sustainable renewable energy sources is imperative to deal with the future energy crises. Various technologies have been developed in this context, for example, water electrolysis, reversible fuel cell and metal-air batteries etc. However, the sluggish kinetics of oxygen evolution reaction (OER) occurring at the anode of these energy storage/conversion systems becomes a significant hurdle. Recently, researchers utilized noble metals as electrocatalysts to enhance their efficiency still the high cost and scarcity of these materials draw the attention of researchers towards the cost-effective Perovskite oxide nanomaterials due to their extraordinary flexibility. In this review, the importance of perovskite oxide nanomaterials as electrocatalysts for OER is discussed, followed by related reaction mechanisms and series of activity descriptors. Fundamental understanding about the instrumentation, parameters and protocols for the experimental measurements including concerned issues are also summarized. Moreover, various activation strategies adopted in recent years to enhance the electrocatalytic performance of perovskite oxides are also underlined. The article concludes with an outlook of existing challenges and future scope of these materials as electrocatalysts. The challenges and prospects discussed herein may pave the ways to rationally design the highly active and stable perovskites to outperform noble metal-based OER electrocatalysts. � 2023 The Authors. ChemCatChem published by Wiley-VCH GmbH.
Tunable dielectric and memory features of ferroelectric layered perovskite Bi4Ti3O12 nanoparticles doped nematic liquid crystal composite
(Elsevier B.V., 2022-11-24T00:00:00) Anu; Varshney, Depanshu; Yadav, Kamlesh; Prakash, Jai; Meena, Harikesh; Singh, Gautam
Herein, we report the synthesis of ferroelectric layered perovskite Bi4Ti3O12 (BT4) nanoparticles (NPs) and the temperature-dependent dielectric and electro-optical (especially memory effect) properties of 4-pentyl-4?-cyanobiphenyl (5CB) nematic liquid crystal (NLC) doped with 1 wt% BT4 NPs (i.e. 5CB-BT4 composite) using polarising optical microscopy and frequency-dependent dielectric spectroscopy techniques. BT4 NPs were synthesised via a microwave-assisted chemical method and characterised using various instrumental techniques, which confirmed the formation of a non-stoichiometric and oxygen-deficient orthorhombic crystal phase. The agglomeration-free and uniform dispersion of BT4 NPs in the 5CB matrix was confirmed by optical textures. The optical memory studied by bias voltage-dependent (ON-OFF) optical textures is decreased by ? 2.6 times in the 5CB-BT4 composite compared with 5CB. Moreover, dielectric parameters such as dielectric permittivity, dielectric loss, loss tangent, conductivity, and activation energy of 5CB and composite (5CB-BT4) are estimated using dielectric spectroscopy. The dielectric anisotropy is decreased, whereas no shift in the clearing temperature is observed in the 5CB-BT4 composite compared to the 5CB sample. Also, the DC conductivity of 5CB-BT4 composite is found to be increased by approximately four times compared to the 5CB. Our studies clearly demonstrate the tunability of the dielectric and optical memory features of NLC (5CB) matrix by dopant BT4 NPs, without significantly affecting the molecular alignment of the NLC molecules. Such composites would certainly be useful in the fabrication of NLC based tunable devices such as optical memory and conductivity switches. � 2022 Elsevier B.V.
Tuning the Morphology of Lanthanum Cobaltite Using the Surfactant-Assisted Hydrothermal Approach for Enhancing Oxygen Evolution Catalysis
(Springer Science and Business Media Deutschland GmbH, 2022-09-01T00:00:00) Deeksha; Kour, Pawanpreet; Ahmed, Imtiaz; Haldar, Krishna Kanta; Yadav, Kamlesh
The high consumption rate of fossil fuels to meet the global energy demands attracts the progress of innovative energy storage and conversion systems. Among them, water electrolysis shows major concern because of its great potential to produce clean hydrogen energy. The dawdling dynamics of the oxygen evolution reaction (OER) that occurs on the anode results in the low energy efficiency of the process. Perovskite oxide with transition metal on the B site possesses a high intrinsic as well as extrinsic activity toward OER. However, the low specific surface area restricts their catalytic activity. Here, we report on the synthesis of lanthanum cobaltite (LaCoO3) nanoparticles and bundles of nanorods using glycine and PVP surfactants, respectively, via the hydrothermal method. Structural characterizations confirmed the pure phase synthesis of LaCoO3 perovskite nanomaterials and further their electrocatalytic performance is investigated in an alkaline medium (1 M KOH). The results show that randomly oriented bundles of nanorods (average length 515 nm, average diameter 65 nm) exhibit smaller overpotential (? = 420 mV) at j = 10 mA cm?2 and the Tafel slope (99 mV dec?1) compared with nanoparticles (? = 450 mV and Tafel slope ~ 110 mV dec?1). The dramatically improved OER activity and larger electrochemical surface area (ECSA) of nanorods as compared to nanoparticles are because of the interconnected porous architecture of nanorods. Our work not only highlights the surfactant-assisted hydrothermal approach to synthesize the nanorods but also introduces the effect of a change in morphology on electrochemical activity. � 2022, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.