Papers by manorama Sunkara
Materials Science And Engineering: B, Mar 1, 2021
Chemical routes for synthesizing semiconductor heterostructures (SHs) from viewpoints of improved... more Chemical routes for synthesizing semiconductor heterostructures (SHs) from viewpoints of improved band energetics in an optoelectronic device continue to be a lucrative area. Here we report on the experimental and theoretical band alignment correlated by XPS and UV-DRS analysis at the n-n nanointerfaces of CaO-ZnO heterostructure. A wet synthesis route was utilized to obtain SHs by zinc hydroxide carbonate (Zn 5 (CO 3) 2 (OH) 6) conversion to ZnO using Ca(OH) 2 at near room temperature and by calcination method. The heterostructures achieved by reacting Zn 5 (CO 3) 2 (OH) 6 with Ca(OH) 2 at near room temperature and by calcination method are referred to as Ca-ZMS and CaO-ZnO, respectively. The band gaps of individual components namely, CaO and ZnO were found to be 4.67 and 3.32 eV, respectively. In each case, band alignment was found to be of type II (staggered) in contrast to what is reported in the literature as type I (straddled). This change was attributed to the presence of nanostructured CaO. An interfacial valence band and conduction band offset of − 1.37 and 2.72 eV was observed in Ca-ZMS, while CaO-ZnO demonstrated valence band and conduction band offset of − 0.67 and 2.02 eV, respectively.
Journal of materials chemistry. A, Materials for energy and sustainability, 2016
The improved performance of the potentiometric CO2sensor was attributed to the high crystallinity... more The improved performance of the potentiometric CO2sensor was attributed to the high crystallinity and tailored morphologies of the sensing and reference electrode nanomaterials.
ACS applied nano materials, Jun 29, 2018
This work details novel insights on the role of energetics, that is, energy band bending and buil... more This work details novel insights on the role of energetics, that is, energy band bending and built-in potential at the nanointerface of CuO/BaTiO3 forming type I p/n heterostructures, evaluated by correlating X-ray photoelectron spectroscopy and ultraviolet diffuse reflectance spectroscopy studies. Cetyltrimethylammonium bromide (CTAB) assisted hydrothermal route was used to synthesize BaTiO3 cuboids with six active {100} facets, and its CuO based heterostructures were tested for bifunctional applications in environmental nanoremediation. Straddled CuO/BaTiO3 heterostructures reported herein showcased exceptional flexibility as a ultraviolet (UV) active photocatalyst for methyl orange (MO) degradation and chemo-resistive CO2 gas sensor. CuO/BaTiO3 heterostructures in equimole ratio could degrade 99% MO in 50 min with rate constant (κ) of a first-order reaction observed to be 10 and 100-fold greater in comparison with BaTiO3 and CuO samples, respectively. Subsequently, in a parallel application, trials wer...
Journal of Materials Chemistry B, 2017
Fig.S1: Cell death of SK-OV-3 cells in the presence of Lactoferrin nanoparticles (without Ce6) an... more Fig.S1: Cell death of SK-OV-3 cells in the presence of Lactoferrin nanoparticles (without Ce6) and upon light treatment. Cell viability was estimated by MTT assay after light treatment.
Journal of Magnetism and Magnetic Materials, Feb 1, 2018
Исследуются перспективы развития уголовного процесса в условиях цифровизации. Сделан вывод, что с... more Исследуются перспективы развития уголовного процесса в условиях цифровизации. Сделан вывод, что следственная правовая система формирования доказательств, равно как и принятия процессуальных решений, в условиях цифровизации технологически устарела. Предложена модель состязательного уголовного процесса, гарантирующая защиту прав и свобод его участников, в процедуре производства и выработки решений которого задействованы цифровые технологии, сохранен стандарт допустимости доказательств. Ключевые слова: доказательственное право; уголовное преследование; баланс частных и публичных интересов; состязательное судопроизводство; цифровизация.
Heterojunction nanocomposites were realized between p-type CuO and n-type SnO2 by simple hydrothe... more Heterojunction nanocomposites were realized between p-type CuO and n-type SnO2 by simple hydrothermal route, further incorporation with 0.5wt.% silver showed an efficient sensor response of 72.02% towards carbon dioxide at a comparably low operating temperature of 300°C. The synthesized samples were characterized extensively by XRD and UV-DRS. Morphological evaluations carried out using transmission electron microscope not only provided information on the size and shape of the materials but also revealed that the hierarchical assembly remained intact for CuO-SnO2 nanocomposite. Furthermore, carbon dioxide gas sensing properties (sensitivity, sensor response, and recovery time) of the as-synthesized nanocomposites were investigated to demonstrate the ability of p-n heterojunction. Owing to the porous structure and large surface area, the nanocomposite exhibited superior sensitivity with short response/recovery times at concentrations of 10,000 ppm of CO2 gas balanced in air. Finally, it was concluded that embellishing 0.5wt.% silver on the surface activated these nanocomposites. This surface activation reduced the operating temperature and also promoted excellent sensitivity, selectivity, recovery time towards carbon dioxide. A detailed insight into sensing mechanism based on UV-DRS spectroscopy studies was presented.
ACS Sustainable Chemistry & Engineering, Feb 14, 2018
Globally recognized for its role as an occupational hazard, carbon dioxide (CO2) detection and mo... more Globally recognized for its role as an occupational hazard, carbon dioxide (CO2) detection and monitoring is essential in agriculture, chemical manufacturing, and healthcare/clinical-oriented applications. Although, optical and chemical gas sensors are available commercially, current gas sensing technologies involving selective monitoring of CO2 at lower detection limits specifically for industrial conditions still remains a formidable challenge. Herein, we present a simple strategy for highly selective CO2 detection using an inexpensive transducer platform based on reversible chemisorbed carbonation between CO2 and CaO-BaTiO3 heterostructures. Microsensors showed an optimum sensitivity of 65% toward 1000 ppm of CO2 gas and superior selectivity when operated at 160 °C. Such a remarkable sensing performance originates from the discretely created n-n nanointerfaces and conveniently actualized staggered energy band positions that promote favorable charge transfer upon exposure to CO2 gas molecules even at pa...
ChemistrySelect, Feb 22, 2019
The highlight of this study is a successful attempt to obtain a visible light active photo cataly... more The highlight of this study is a successful attempt to obtain a visible light active photo catalyst by a single step synthesis procedure. The photocatalytic performance of Cu2O, a p‐type semiconducting oxide with a band gap in the visible region of the solar spectrum is improved by the presence of TiO2 on its surface. Nanocomposites of Cu2O@TiO2 were synthesized by a facile one pot synthesis route. X‐ray diffraction (XRD) studies confirmed the face centred cubic structure of Cu2O but was inconclusive about the TiO2 presence. Field Emission Scanning Electron Microscopy (FE‐SEM) images confirmed the octahedral morphology of the Cu2O particles and the presence of Ti and O on the surface. High Resolution Transmission Electron Microscopy (HR‐TEM) and Selected Area Electron Diffraction (SAED) studies established the presence of nanocrystalline anatase TiO2 on the Cu2O interfaces. The specific role of the nanoparticles of n‐type TiO2 positioned on the p‐type Cu2O in improving photo‐activity and making it visible light active was demonstrated. The photocatalytic activity of the composite was demonstrated by the degradation of a model dye Rhodamine B using visible light. It is observed that the photocatalytic activity is dependent on density of heterojunctions formed in the photo‐system which the nano‐crystalline TiO2 , has very effectively created on the Cu2O surface, which are responsible for the improved photocatalytic response. This work establishes that the in‐situ creation of Cu2O@TiO2 is effective in creating p‐n heterojunctions at the Cu2O@TiO2 interface, which result in arresting the recombination processes, leading to improved photocatalytic performance.
ACS omega, Oct 7, 2019
A highly porous architecture of graphitic carbon nitride g-C 3 N 4 /Cu 2 O nanocomposite in the f... more A highly porous architecture of graphitic carbon nitride g-C 3 N 4 /Cu 2 O nanocomposite in the form of cubes with a side length of ≈ 1 μm, large pores of 1.5 nm, and a high surface area of 9.12 m 2 /g was realized by an optimized in situ synthesis protocol. The synthesis protocol involves dispersing a suitable "Cu" precursor into a highly exfoliated g-C 3 N 4 suspension and initiating the reaction for the formation of Cu 2 O. Systematic optimization of the conditions and compositions resulted in a highly crystalline g-C 3 N 4 /Cu 2 O composite. In the absence of g-C 3 N 4 , the Cu 2 O particles assemble into cubes with a size of around 300 nm and are devoid of pores. Detailed structural and morphological evaluations by powder X-ray diffraction and field emission scanning electron microscopy revealed the presence of highly exfoliated g-C 3 N 4 , which is responsible for the formation of the porous architecture in the cube like assembly of the composite. The micrographs clearly reveal the porous structure of the composite that retains the cubic shape of Cu 2 O, and the energy-dispersive spectroscopy supports the presence of g-C 3 N 4 within the cubic morphology. Among the different g-C 3 N 4 /Cu 2 O compositions, CN/Cu-5 with 10% of g-C 3 N 4 , which is also the optimum composition resulting in a porous cubic morphology, shows the best visible light photocatalytic performance. This has been supported by the ultraviolet diffuse reflectance spectroscopy (UV-DRS) studies of the composite which shows a band gap of around 2.05 eV. The improved photocatalytic performance of the composite could be attributed to the highly porous morphology along with the suitable optical band gap in the visible region of the solar spectrum. The optimized composite, CN/ Cu-5, demonstrates a visible light degradation of 81% for Methylene Blue (MB) and 85.3% for Rhodamine-B (RhB) in 120 min. The decrease in the catalyst performance even after three repeated cycles is less than 5% for both MB and RhB dyes. The rate constant for MB and RhB degradation is six and eight times higher with CN/Cu-5 when compared with the pure Cu 2 O catalyst. To validate our claim that the dye degradation is not merely decolorization, liquid chromatography−mass spectroscopy studies were carried out, and the end products of the degraded dyes were identified.
ACS Applied Materials & Interfaces, Aug 7, 2017
Tetragonal BaTiO3 spheroids synthesized by a facile hydrothermal route using Tween 80 were observ... more Tetragonal BaTiO3 spheroids synthesized by a facile hydrothermal route using Tween 80 were observed to be polydispersed with a diameter in the range of ∼15-75 nm. Thereon, BaTiO3 spheroids were decorated with different percentages of Ag@CuO by wet impregnation, and their affinity toward carbon dioxide (CO2) gas when employed as sensitive layers in a microsensor was investigated. The results revealed that the metal nanocomposite-based sensor had an exceptional stability and sensitivity toward CO2 gas (6-fold higher response), with appreciable response and recovery times (&lt;10 s) and higher repeatability (98%) and accuracy (96%) at a low operating temperature of 120 °C, compared to those of pure BaTiO3 and CuO. Such improved gas-sensing performances even at a very low concentration (∼700 ppm) is attributable to both the chemical and electrical contributions of Ag@CuO forming intermittent nanointerfaces with BaTiO3 spheroids, exhibiting unique structural stability. The CO2-sensing mechanism of CuO/BaTiO3 nanocomposite was studied by the diffuse reflectance infrared Fourier transform spectroscopy technique that established the reaction of CO2 with BaO and CuO to form the respective carbonate species that is correlated with the change in material resistance consequently monitored as sensor response.
Inorganic chemistry frontiers, 2017
Efficient CO2gas detection and visible light photocatalysis performance shown by interleaved CuO/... more Efficient CO2gas detection and visible light photocatalysis performance shown by interleaved CuO/ZnO heterostructures ascribed primarily to the high surface area, p/n nano-interfaces and catalytic role of Ag.
Sensors and Actuators B: Chemical, 2022
La presente invention concerne des compositions electrolytiques a conductivite ionique elevee. L&... more La presente invention concerne des compositions electrolytiques a conductivite ionique elevee. L'invention concerne en particulier des compositions electrolytiques a conductivite ionique elevee de reseaux polymeres semi-interpenetrants et leurs nanocomposites formant une matrice electrolytique quasi-solide/solide pour la production d'energie, des dispositifs de stockage et de distribution, en particulier pour des cellules solaires hybrides, des batteries rechargeables, des condensateurs, des systemes electrochimiques et des dispositifs flexibles. La composition electrolytique a reseau polymere semi-interpenetrant a composants binaires ou tertiaires comprend: a) un reseau polymere a squelette polyether (composant I); b) un polymere hyper-ramifie, ramifie, lineaire de faible poids moleculaire ou n'importe quelle combinaison binaire desdits polymeres avec des groupes d'extremite non reactive (composant II et/ou composant III, pour la formation d'un systeme semi-IPN ...
2017 IEEE 12th International Conference on Nano/Micro Engineered and Molecular Systems (NEMS), 2017
3D hierarchical hollow ZnO microspheres were impregnated with CuO microleaves to form p-n heteroj... more 3D hierarchical hollow ZnO microspheres were impregnated with CuO microleaves to form p-n heterojunctions. The synthesized p-type CuO/n-type ZnO composite was characterized for its composition and morphology. X-ray diffractograms confirmed formation of phase pure ZnO along with CuO in equimole ratio by a solution precipitation technique. FE-SEM micrographs revealed 3D ZnO hollow microspheres in the size range 3–8 µm formed of interleaved sheets, 10–20 nm thick as the primary building blocks. The results indicated an improved sensor response (S) of 44% at 320oC for a CO2 gas concentration of 10,000 ppm for the developed CuO/ZnO mixed metal oxide based sensor. The improved sensor response observed here, when compared with commercial ZnO powder decorated with CuO microleaves was attributed to the specific role of CuO in the sensing mechanism, formation of p-CuO/n-ZnO heterojunction and nanostructured sensitive layer, thus presenting CuO/ZnO composite as a candidate material for CO2 gas sensing.
Journal of Colloid and Interface Science, 2019
Tailored synthesis of heterostructures for low temperature (sub 200 °C) CO2 sensing continues to ... more Tailored synthesis of heterostructures for low temperature (sub 200 °C) CO2 sensing continues to be a challenging task. The present study demonstrates CO2 sensing characteristics of CaO-ZnO heterostructures achieved by zinc hydroxide carbonate (Zn5(CO3)2(OH)6) conversion to ZnO using Ca(OH)2 at 50 °C. Control samples namely, Zn5(CO3)2(OH)6, Ca(OH)2, ZnO, and CaO integrated microsensors exhibited low sensitivity towards CO2 gas. However, CaO-ZnO heterostructures demonstrated significant sensitivity (26 to 91%) at 150 °C for gas concentration ranging from 100 to 10000 ppm, respectively. In this study, zinc hydroxide carbonate sensitized with 25 wt% Ca(OH)2 to form CaO-ZnO heterostructures (25CaZMS) displayed a promising sensitivity (77%) and selectivity (98%) towards 500 ppm CO2 gas. Moreover, the selectivity studies were conducted in the presence of 10 commonly found gases and their sensing performance was compared against CO2 gas in dry and humid conditions. The developed CaO-ZnO sensor exhibited faster kinetics in comparison to the control samples. Improved sensing performance observed here is attributed to the low-temperature synthesis route which resulted in a large number of active pores and high surface area morphology. Additionally, the high CO2 adsorption capacity of CaO combined with compatible n-type semiconductors in forming highly dynamic nano-interfaced heterostructure is a promising step towards developing a precise CO2 gas microsensor.
RSC Adv., 2016
Correction for ‘Probing high temperature ferromagnetism and its paramagnetic phase change due to ... more Correction for ‘Probing high temperature ferromagnetism and its paramagnetic phase change due to Eu3+ incorporation in ZnO nanophosphors’ by K. Jayanthi Rajan et al., RSC Adv., 2016, 6, 75669–75680.
The Journal of Physical Chemistry C, 2007
Silver nanoparticles of particle size around 15 nm were synthesized by following a simple and gre... more Silver nanoparticles of particle size around 15 nm were synthesized by following a simple and green methodology of photoreduction of silver nitrate (AgNO 3) using bare titania and polyvinyl alcohol (PVA)capped colloidal titanium dioxide nanoparticles/nanotubes under UV-vis light (λ) 365 nm). The synthesized pure TiO 2 nanoparticles/tubes, Ag-TiO 2 nanocomposites and PVA-capped colloidal Ag-TiO 2 nanocomposites are characterized for their structure and morphology by X-ray diffraction (XRD) and transmission electron microscopy (TEM) and for their electronic structure by X-ray photoelectron spectroscopy (XPS). The antibacterial efficiency of all nanocomposites were investigated on Escherichia coli using standard procedures. The synthesized metal-metal oxide nanocomposites are shown to be very efficient toward destroying Gram negative bacteria Escherichia coli.
Journal of Molecular Catalysis A: Chemical, 2012
Chemoselective hydrogenation of olefinic double bonds in the presence of various functional group... more Chemoselective hydrogenation of olefinic double bonds in the presence of various functional groups using layered double hydroxides supported nanopalladium (LDH-Pd 0) catalyst is described. LDH-Pd 0 was recovered quantitatively by simple filtration and reused several times with consistent activity and selectivity.
Journal of Applied Physics, 2007
Control on the conductivity behaviors has been achieved in nanoparticles of NiFe2O4, synthesized ... more Control on the conductivity behaviors has been achieved in nanoparticles of NiFe2O4, synthesized by the hydrothermal route at a fixed temperature of 225°C by varying the pH of the starting solution. Particles synthesized at pH 7 and 8 behave as n-type semiconductors, while those synthesized at pH 9 and above behave as p-type semiconductors. The observed conductivity behavior has been confirmed by gas sensing and thermo-emf studies, and the mechanism has been established by x-ray photoelectron spectroscopic studies. Complete physicochemical characterizations of their phase and morphology have been carried out by x-ray diffraction and transmission electron microscopy. The thermal and electrical characteristics, elemental composition, and magnetic properties have been evaluated by thermogravimetry and differential thermogravimetry, dc conductivity, ac impedance studies, atomic absorption spectroscopy, and vibrating sample magnetometry. Gas sensing studies reveal that the resistance acr...
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Papers by manorama Sunkara