Debjit Ghoshal | Heritage Institute Of Technology,Kolkata (original) (raw)
Papers by Debjit Ghoshal
Bulletin of the American Physical Society, 2019
arXiv: Materials Science, 2020
Bulk chalcogenide perovskite BaZrS3 (BZS), with a direct band gap in visible region, is an import... more Bulk chalcogenide perovskite BaZrS3 (BZS), with a direct band gap in visible region, is an important photovoltaic material, albeit with limited applicability owing to its antiferroelectric (AF) nature. Presently, ferroelectric (FE) perovskite-based photovoltaics are attracting enormous attention for environmental stability and better energy conversion efficiency through enhanced charge separation, owing to loss of center of inversion symmetry. We report on antiferroelectric-ferroelectric (AF-FE) phases of BZS thin film, grown with chemical vapor deposition (CVD), using temperature-dependent Raman investigations and first-principles calculations. The origin of FE phases is established from anomalous behavior of A7g ~ 300 cm-1 and B1g5 ~ 420 cm-1 modes, which involves the vibration of atoms at apical site of ZrS6 octahedra. Additionally, below 60 K, B1g1 and B2g2 ( ~ 85 cm-1) modes appear whereas B12g (~ 60 cm-1) disappears to stabilize the Pnma structure against ferroelectricity by l...
Book Undergraduate Oral Presentations
Biosensors and Bioelectronics, 2021
The rapid, sensitive, and selective detection of target analytes using electrochemical sensors is... more The rapid, sensitive, and selective detection of target analytes using electrochemical sensors is challenging. ESSENCE, a new Electrochemical Sensor that uses a Shear-Enhanced, flow-through Nanoporous Capacitive Electrode, overcomes current electrochemical sensors' response limitations, selectivity, and sensitivity limitations. ESSENCE is a microfluidic channel packed with transducer material sandwiched by a top and bottom microelectrode. The room-temperature instrument less integration process allows the switch of the transducer materials to make up the porous electrode without modifying the electrode architecture or device protocol. ESSENCE can be used to detect both biomolecules and small molecules by simply changing the packed transducer material. Electron microscopy results confirm the high porosity. In conjunction with the non-planar interdigitated electrode, the packed transducer material results in a flow-through porous electrode. Electron microscopy results confirm the high porosity. The enhanced shear forces and increased convective fluxes disrupt the electric double layer's (EDL) diffusive process in ESSENCE. This disruption migrates the EDL to high MHz frequency allowing the capture signal to be measured at around 100 kHz, significantly improving device timing (rapid detection) with a low signal-to-noise ratio. The device's unique architecture allows us multiple configuration modes for measuring the impedance signal. This allows us to use highly conductive materials like carbon nanotubes. We show that by combining single-walled carbon nanotubes as transducer material with appropriate capture probes, NP-μIDE has high selectivity and sensitivity for DNA (fM sensitivity, selective against non-target DNA), breast cancer biomarker proteins (p53, pg/L sensitivity, selective against non-target HER2).
ACS Applied Materials & Interfaces, 2021
Lead iodide (PbI2) as a layered material has emerged as an excellent candidate for optoelectronic... more Lead iodide (PbI2) as a layered material has emerged as an excellent candidate for optoelectronics in the visible and ultraviolet regime. Micrometer-sized flakes synthesized by mechanical exfoliation from bulk crystals or by physical vapor deposition have shown a plethora of applications from low-threshold lasing at room temperature to high-performance photodetectors with large responsivity and faster response. However, large-area centimeter-sized growth of epitaxial thin films of PbI2 with well-controlled orientation has been challenging. Additionally, the nature of grain boundaries in epitaxial thin films of PbI2 remains elusive. Here, we use mica as a model substrate to unravel the growth mechanism of large-area epitaxial PbI2 thin films. The partial growth leading to uncoalesced domains reveals the existence of inversion domain boundaries in epitaxial PbI2 thin films on mica. Combining the experimental results with first-principles calculations, we also develop an understanding of the thermodynamic and kinetic factors that govern the growth mechanism, which paves the way for the synthesis of high-quality large-area PbI2 on other substrates and heterostructures of PbI2 on single-crystalline graphene. The ability to reproducibly synthesize high-quality large-area thin films with precise control over orientation and tunable optical properties could open up unique and hitherto unavailable opportunities for the use of PbI2 and its heterostructures in optoelectronics, twistronics, substrate engineering, and strain engineering.
Physical Review B, 2020
Bulk chalcogenide perovskite BaZrS3 (BZS), with a direct band gap in visible region, is an import... more Bulk chalcogenide perovskite BaZrS3 (BZS), with a direct band gap in visible region, is an important photovoltaic material, albeit with limited applicability owing to its antiferroelectric (AF) nature. Presently, ferroelectric (FE) perovskite-based photovoltaics are attracting enormous attention for environmental stability and better energy conversion efficiency through enhanced charge separation, owing to loss of center of inversion symmetry. We report on antiferroelectric-ferroelectric (AF-FE) phases of BZS thin film, grown with chemical vapor deposition (CVD), using temperaturedependent Raman investigations and first-principles calculations. The origin of FE phases is established from anomalous behavior of 7 g A ~ 300 cm-1 and 5 1g B~ 420 cm-1 modes, which involves the vibration of atoms at apical site of ZrS6 octahedra. Additionally, below 60 K, 1 1g B and 2 2 g B (~ 85 cm-1) modes appear whereas 1 g 2 B (~ 60 cm-1) disappears to stabilize the Pnma structure against ferroelectricity by local distortion. Here, 2 2 g B and 1 g 2 B involve vibrations of Ba atoms in AF manner while 1 1g B involves, in addition, the rotation of octahedra as well. Our first-principles calculations confirm that FE appears as a result of loss of center of inversion symmetry in ZrS6 octahedra due to existence of oxygen (O) impurities placed locally at apical sites of sulfur (S) atom.
Inorganic Chemistry Communications, 2020
Abstract 2D materials have been extensively studied due to their unique optical and electronic pr... more Abstract 2D materials have been extensively studied due to their unique optical and electronic properties. Compositional doping in these materials could further enable useful utilization of these materials in electronics, optoelectronics and energy harvesting. However, scalable one pot synthesis of doped Transition Metal Dichalcogenides (TMDs) has been challenging. Here we develop a facile approach for controlled one step Rhenium (Re) doping in multilayer Molybdenum Disulphide (MoS2) by powder Chemical Vapor Deposition (CVD). Interestingly, we find the morphology of MoS2 is also dependent on the dopant concentrations with a flower like morphology observed at higher doping concentrations.Further we demonstrate a clear correlation between the shift in PL and Raman peaks as a function of Re doping concentrations. A red shift in PL is observed with increased concentration of Re atoms. The ability to controllably dope thin layers of MoS2 could open up unique applications of this material in areas hitherto unexplored.
Advanced Functional Materials, 2020
Organic-inorganic halide perovskites are intrinsically unstable when exposed to moisture and/or l... more Organic-inorganic halide perovskites are intrinsically unstable when exposed to moisture and/or light. Additionally, the presence of lead in many perovskites raises toxicity concerns. Herein is reported a thin film of BaZrS3, a lead-free chalcogenide perovskite. Photoluminescence and X-ray diffraction measurements show that BaZrS3 is far more stable than methylammonium lead iodide (MAPbI3) in moist environments. Moisture-and lightinduced degradations in BaZrS3 and MAPbI3 are compared by using simulations and calculations based on density functional theory. The simulations reveal drastically slower degradation in BaZrS3 due to two factorsweak interaction with water, and very low rates of ion migration. BaZrS3 photo-detecting devices with photo-responsivity of ~46.5 mA W-1 are also reported. The devices retain ~60% of their initial photo-response after 4 weeks in ambient conditions. Similar MAPbI3 devices degrade rapidly and show ~95% decrease in photoresponsivity in just 4 days. The findings establish the superior stability of BaZrS3 and strengthen the case for its use in optoelectronics. New possibilities for thermoelectric energy conversion using these materials are also demonstrated.
Acta Materialia, 2019
This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Advanced Optical Materials, 2019
Advanced Optical Materials, 2019
Advanced Functional Materials, 2017
It is understood that defects of the atomic arrangement of the lattice in 2D molybdenum disulfide... more It is understood that defects of the atomic arrangement of the lattice in 2D molybdenum disulfide (MoS 2) grown by chemical vapor deposition (CVD) can have a profound effect on the electronic and optical properties. Beyond these it is a major prerequisite to also understand the fundamental effect of such defects on phonon transport, to guarantee the successful integration of MoS 2 into the solid-state devices. A comprehensive joint experiment-theory investigation to explore the effect of lattice defects on the thermal transport of the suspended MoS 2 monolayer grown by CVD is presented. The measured room temperature thermal conductivity values are 30 ± 3.3 and 35.5 ± 3 W m −1 K −1 for two samples, which are more than two times smaller than that of their exfoliated counterpart. High-resolution transmission electron microscopy shows that these CVD-grown samples are polycrystalline in nature with low angle grain boundaries, which is primarily responsible for their reduced thermal conductivity. Higher degree of polycrystallinity and aging effects also result in smoother temperature dependency of thermal conductivity (κ) at temperatures below 100 K. First-principles lattice dynamics simulations are carried out to understand the role of defects such as isotopes, vacancies, and grain boundaries on the phonon scattering rates of our CVD-grown samples.
Journal of Materials Science: Materials in Electronics, 2018
Copper nanowires have been synthesized at different pH values through the template assisted elect... more Copper nanowires have been synthesized at different pH values through the template assisted electrodeposition technique using polycarbonate track-etch membranes as scaffolds. The effect of pH (0.8-2.8) of the electrolyte on structure, morphology, composition and deposition rate of copper into the pores of the template, while keeping other electrochemical conditions same, was investigated. X-ray diffraction analysis confirmed the face centered cubic phase of synthesized nanowires. With the change in pH, no shift in peaks was observed except the inclusion of an additional peak of copper oxide in nanowires synthesized at pH 2.8. The nanocrystallite size, strain, lattice stress and energy density were evaluated by X-ray analysis. Field emission scanning electron microscopy images revealed that nanowires obtained at pH 0.8, 1.1 and 1.4 showed incomplete deposition in the pores of the membrane whereas, the nanowires obtained at pH 1.7 were densely stacked, vertically aligned and uniform along the diameter and that obtained from pH 2.0-2.8 had overdeposition on their top. An increase in deposition rate was observed with the increase in pH value. The average diameter of Cu nanowires was found to be ~ 105 nm. The electrical conductivity of as-grown nanowires was observed to decrease 13-fold as the transition from bulk values to the nanosystem. Nanowires prepared at pH of 1.7 were characterized for their field-emission properties. A very large fieldenhancement factor of ~ 10,855 was obtained indicating that Cu nanowires grown by reported technique shows outstanding potential as efficient field-emitters for flat panel displays.
Advanced Functional Materials, 2018
Granulocyte-macrophage colony-stimulation factor plays different crucial roles during embryo impl... more Granulocyte-macrophage colony-stimulation factor plays different crucial roles during embryo implantation and subsequent development. Here we aimed to evaluate the effects of embryo cell culture medium, with the inclusion of granulocyte-macrophage colony-stimulation factor (GM-CSF), on embryo development and pregnancy rate. To this end, we took advantage of our retrospective observational study to correlate the outcomes from two different culture media. We included in this study 25 unselected patient from our IVF Center that underwent heterologous IVF cycle with crypreserved oocytes. We analyze the fertilization rate, pregnancy rate, and embryo quality at different day of transfer obtained from two different media composition. Our results show that the rate of fertilization and the pregnancy rate were increased using medium added with this particular type of cytokines (GM-CSF).
Physical Review Materials, 2018
High-quality heteroepitaxy of CdTe is challenging due to lattice mismatches of CdTe with many sub... more High-quality heteroepitaxy of CdTe is challenging due to lattice mismatches of CdTe with many substrates. Herein, we demonstrate the epitaxial growth of single crystalline CdTe films, in multilevel island format, on mica using metalorganic chemical vapor deposition, regardless of large in-plane lattice mismatch (~13%) between CdTe(111) and mica(001). X-ray and electron diffractions suggest that CdTe is epitaxially aligned with mica: out-of-plane CdTe 111 //mica 001 and in-plane CdTe 1 21 //mica 010. Full-width-at-half-maximum (FWHM) of X-ray rocking curve and FWHM of X-ray azimuthal in-plane angular dispersion of CdTe are shown to be 0.11 ο and 0.38 ο , respectively, better than most CdTe films reported. Electron backscattering diffraction shows that CdTe grains are tens of μm and, if twin boundaries are excluded, in excess of 250 μm in size. In contrast to the belief that overlayer growth on mica is purely through van der Waals interaction, our first-principle calculations uncover that van der Waals interaction only contributes to 20% of the total interfacial energy, and 80% of the interfacial energy comes from chemical interaction. We believe such a strong chemical interaction is accountable for the highquality epitaxy. The demonstration of epitaxial growth of high-quality semiconductor on mica with a large lattice mismatch creates opportunities for flexible optoelectronic devices.
ACS nano, Jan 27, 2018
We report the use of a single layer of two-dimensional hexagonal boron nitride (SL-hBN) as the th... more We report the use of a single layer of two-dimensional hexagonal boron nitride (SL-hBN) as the thinnest insulating barrier to microbial corrosion induced by the sulfate-reducing bacteria Desulfovibrio alaskensis G20. We used electrochemical methods to assess the corrosion resistance of SL-hBN on copper against the effects of both the planktonic and sessile forms of the sulfate-reducing bacteria. Cyclic voltammetry results show that SL-hBN-Cu is effective in suppressing corrosion effects of the planktonic cells at potentials as high as 0.2 V ( vs Ag/AgCl). The peak anodic current for the SL-hBN coatings is ∼36 times lower than that of bare Cu. Linear polarization resistance tests confirm that the SL-hBN coatings serve as a barrier against corrosive effects of the G20 biofilm when compared to bare Cu. The SL-hBN serves as an impermeable barrier to aggressive metabolites and offers ∼91% corrosion inhibition efficiency, which is comparable to much thicker commercial coatings such as pol...
Body: In the last decade, self-limiting growth of large-area and monolayer graphene sheets has be... more Body: In the last decade, self-limiting growth of large-area and monolayer graphene sheets has been demonstrated on Ge (110) substrates.[1,2] Despite the numerous reports focusing on synthesis of graphene/Ge and the amply recognized technological relevance of this materials combination to electronics, there is a limited understanding of charge transport in graphene along the graphene/Ge growth interface. A major challenge in characterizing carrier concentration and mobilities in graphene/Ge is that chemical vapor deposition (CVD) of high-quality graphene on Ge is performed at a temperature, T>900 °C. At this temperature, even intrinsic Ge has been shown to become p-type due to a large concentration of vacancies.[3,4] CVD grown graphene on Ge is thus bonded to a relatively high-conductance substrate, a feature that makes it difficult to characterize and understand the influence of graphene-Ge interactions on charge transport in this 2D system. In this work we quantify lateral char...
Bulletin of the American Physical Society, 2019
arXiv: Materials Science, 2020
Bulk chalcogenide perovskite BaZrS3 (BZS), with a direct band gap in visible region, is an import... more Bulk chalcogenide perovskite BaZrS3 (BZS), with a direct band gap in visible region, is an important photovoltaic material, albeit with limited applicability owing to its antiferroelectric (AF) nature. Presently, ferroelectric (FE) perovskite-based photovoltaics are attracting enormous attention for environmental stability and better energy conversion efficiency through enhanced charge separation, owing to loss of center of inversion symmetry. We report on antiferroelectric-ferroelectric (AF-FE) phases of BZS thin film, grown with chemical vapor deposition (CVD), using temperature-dependent Raman investigations and first-principles calculations. The origin of FE phases is established from anomalous behavior of A7g ~ 300 cm-1 and B1g5 ~ 420 cm-1 modes, which involves the vibration of atoms at apical site of ZrS6 octahedra. Additionally, below 60 K, B1g1 and B2g2 ( ~ 85 cm-1) modes appear whereas B12g (~ 60 cm-1) disappears to stabilize the Pnma structure against ferroelectricity by l...
Book Undergraduate Oral Presentations
Biosensors and Bioelectronics, 2021
The rapid, sensitive, and selective detection of target analytes using electrochemical sensors is... more The rapid, sensitive, and selective detection of target analytes using electrochemical sensors is challenging. ESSENCE, a new Electrochemical Sensor that uses a Shear-Enhanced, flow-through Nanoporous Capacitive Electrode, overcomes current electrochemical sensors' response limitations, selectivity, and sensitivity limitations. ESSENCE is a microfluidic channel packed with transducer material sandwiched by a top and bottom microelectrode. The room-temperature instrument less integration process allows the switch of the transducer materials to make up the porous electrode without modifying the electrode architecture or device protocol. ESSENCE can be used to detect both biomolecules and small molecules by simply changing the packed transducer material. Electron microscopy results confirm the high porosity. In conjunction with the non-planar interdigitated electrode, the packed transducer material results in a flow-through porous electrode. Electron microscopy results confirm the high porosity. The enhanced shear forces and increased convective fluxes disrupt the electric double layer's (EDL) diffusive process in ESSENCE. This disruption migrates the EDL to high MHz frequency allowing the capture signal to be measured at around 100 kHz, significantly improving device timing (rapid detection) with a low signal-to-noise ratio. The device's unique architecture allows us multiple configuration modes for measuring the impedance signal. This allows us to use highly conductive materials like carbon nanotubes. We show that by combining single-walled carbon nanotubes as transducer material with appropriate capture probes, NP-μIDE has high selectivity and sensitivity for DNA (fM sensitivity, selective against non-target DNA), breast cancer biomarker proteins (p53, pg/L sensitivity, selective against non-target HER2).
ACS Applied Materials & Interfaces, 2021
Lead iodide (PbI2) as a layered material has emerged as an excellent candidate for optoelectronic... more Lead iodide (PbI2) as a layered material has emerged as an excellent candidate for optoelectronics in the visible and ultraviolet regime. Micrometer-sized flakes synthesized by mechanical exfoliation from bulk crystals or by physical vapor deposition have shown a plethora of applications from low-threshold lasing at room temperature to high-performance photodetectors with large responsivity and faster response. However, large-area centimeter-sized growth of epitaxial thin films of PbI2 with well-controlled orientation has been challenging. Additionally, the nature of grain boundaries in epitaxial thin films of PbI2 remains elusive. Here, we use mica as a model substrate to unravel the growth mechanism of large-area epitaxial PbI2 thin films. The partial growth leading to uncoalesced domains reveals the existence of inversion domain boundaries in epitaxial PbI2 thin films on mica. Combining the experimental results with first-principles calculations, we also develop an understanding of the thermodynamic and kinetic factors that govern the growth mechanism, which paves the way for the synthesis of high-quality large-area PbI2 on other substrates and heterostructures of PbI2 on single-crystalline graphene. The ability to reproducibly synthesize high-quality large-area thin films with precise control over orientation and tunable optical properties could open up unique and hitherto unavailable opportunities for the use of PbI2 and its heterostructures in optoelectronics, twistronics, substrate engineering, and strain engineering.
Physical Review B, 2020
Bulk chalcogenide perovskite BaZrS3 (BZS), with a direct band gap in visible region, is an import... more Bulk chalcogenide perovskite BaZrS3 (BZS), with a direct band gap in visible region, is an important photovoltaic material, albeit with limited applicability owing to its antiferroelectric (AF) nature. Presently, ferroelectric (FE) perovskite-based photovoltaics are attracting enormous attention for environmental stability and better energy conversion efficiency through enhanced charge separation, owing to loss of center of inversion symmetry. We report on antiferroelectric-ferroelectric (AF-FE) phases of BZS thin film, grown with chemical vapor deposition (CVD), using temperaturedependent Raman investigations and first-principles calculations. The origin of FE phases is established from anomalous behavior of 7 g A ~ 300 cm-1 and 5 1g B~ 420 cm-1 modes, which involves the vibration of atoms at apical site of ZrS6 octahedra. Additionally, below 60 K, 1 1g B and 2 2 g B (~ 85 cm-1) modes appear whereas 1 g 2 B (~ 60 cm-1) disappears to stabilize the Pnma structure against ferroelectricity by local distortion. Here, 2 2 g B and 1 g 2 B involve vibrations of Ba atoms in AF manner while 1 1g B involves, in addition, the rotation of octahedra as well. Our first-principles calculations confirm that FE appears as a result of loss of center of inversion symmetry in ZrS6 octahedra due to existence of oxygen (O) impurities placed locally at apical sites of sulfur (S) atom.
Inorganic Chemistry Communications, 2020
Abstract 2D materials have been extensively studied due to their unique optical and electronic pr... more Abstract 2D materials have been extensively studied due to their unique optical and electronic properties. Compositional doping in these materials could further enable useful utilization of these materials in electronics, optoelectronics and energy harvesting. However, scalable one pot synthesis of doped Transition Metal Dichalcogenides (TMDs) has been challenging. Here we develop a facile approach for controlled one step Rhenium (Re) doping in multilayer Molybdenum Disulphide (MoS2) by powder Chemical Vapor Deposition (CVD). Interestingly, we find the morphology of MoS2 is also dependent on the dopant concentrations with a flower like morphology observed at higher doping concentrations.Further we demonstrate a clear correlation between the shift in PL and Raman peaks as a function of Re doping concentrations. A red shift in PL is observed with increased concentration of Re atoms. The ability to controllably dope thin layers of MoS2 could open up unique applications of this material in areas hitherto unexplored.
Advanced Functional Materials, 2020
Organic-inorganic halide perovskites are intrinsically unstable when exposed to moisture and/or l... more Organic-inorganic halide perovskites are intrinsically unstable when exposed to moisture and/or light. Additionally, the presence of lead in many perovskites raises toxicity concerns. Herein is reported a thin film of BaZrS3, a lead-free chalcogenide perovskite. Photoluminescence and X-ray diffraction measurements show that BaZrS3 is far more stable than methylammonium lead iodide (MAPbI3) in moist environments. Moisture-and lightinduced degradations in BaZrS3 and MAPbI3 are compared by using simulations and calculations based on density functional theory. The simulations reveal drastically slower degradation in BaZrS3 due to two factorsweak interaction with water, and very low rates of ion migration. BaZrS3 photo-detecting devices with photo-responsivity of ~46.5 mA W-1 are also reported. The devices retain ~60% of their initial photo-response after 4 weeks in ambient conditions. Similar MAPbI3 devices degrade rapidly and show ~95% decrease in photoresponsivity in just 4 days. The findings establish the superior stability of BaZrS3 and strengthen the case for its use in optoelectronics. New possibilities for thermoelectric energy conversion using these materials are also demonstrated.
Acta Materialia, 2019
This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Advanced Optical Materials, 2019
Advanced Optical Materials, 2019
Advanced Functional Materials, 2017
It is understood that defects of the atomic arrangement of the lattice in 2D molybdenum disulfide... more It is understood that defects of the atomic arrangement of the lattice in 2D molybdenum disulfide (MoS 2) grown by chemical vapor deposition (CVD) can have a profound effect on the electronic and optical properties. Beyond these it is a major prerequisite to also understand the fundamental effect of such defects on phonon transport, to guarantee the successful integration of MoS 2 into the solid-state devices. A comprehensive joint experiment-theory investigation to explore the effect of lattice defects on the thermal transport of the suspended MoS 2 monolayer grown by CVD is presented. The measured room temperature thermal conductivity values are 30 ± 3.3 and 35.5 ± 3 W m −1 K −1 for two samples, which are more than two times smaller than that of their exfoliated counterpart. High-resolution transmission electron microscopy shows that these CVD-grown samples are polycrystalline in nature with low angle grain boundaries, which is primarily responsible for their reduced thermal conductivity. Higher degree of polycrystallinity and aging effects also result in smoother temperature dependency of thermal conductivity (κ) at temperatures below 100 K. First-principles lattice dynamics simulations are carried out to understand the role of defects such as isotopes, vacancies, and grain boundaries on the phonon scattering rates of our CVD-grown samples.
Journal of Materials Science: Materials in Electronics, 2018
Copper nanowires have been synthesized at different pH values through the template assisted elect... more Copper nanowires have been synthesized at different pH values through the template assisted electrodeposition technique using polycarbonate track-etch membranes as scaffolds. The effect of pH (0.8-2.8) of the electrolyte on structure, morphology, composition and deposition rate of copper into the pores of the template, while keeping other electrochemical conditions same, was investigated. X-ray diffraction analysis confirmed the face centered cubic phase of synthesized nanowires. With the change in pH, no shift in peaks was observed except the inclusion of an additional peak of copper oxide in nanowires synthesized at pH 2.8. The nanocrystallite size, strain, lattice stress and energy density were evaluated by X-ray analysis. Field emission scanning electron microscopy images revealed that nanowires obtained at pH 0.8, 1.1 and 1.4 showed incomplete deposition in the pores of the membrane whereas, the nanowires obtained at pH 1.7 were densely stacked, vertically aligned and uniform along the diameter and that obtained from pH 2.0-2.8 had overdeposition on their top. An increase in deposition rate was observed with the increase in pH value. The average diameter of Cu nanowires was found to be ~ 105 nm. The electrical conductivity of as-grown nanowires was observed to decrease 13-fold as the transition from bulk values to the nanosystem. Nanowires prepared at pH of 1.7 were characterized for their field-emission properties. A very large fieldenhancement factor of ~ 10,855 was obtained indicating that Cu nanowires grown by reported technique shows outstanding potential as efficient field-emitters for flat panel displays.
Advanced Functional Materials, 2018
Granulocyte-macrophage colony-stimulation factor plays different crucial roles during embryo impl... more Granulocyte-macrophage colony-stimulation factor plays different crucial roles during embryo implantation and subsequent development. Here we aimed to evaluate the effects of embryo cell culture medium, with the inclusion of granulocyte-macrophage colony-stimulation factor (GM-CSF), on embryo development and pregnancy rate. To this end, we took advantage of our retrospective observational study to correlate the outcomes from two different culture media. We included in this study 25 unselected patient from our IVF Center that underwent heterologous IVF cycle with crypreserved oocytes. We analyze the fertilization rate, pregnancy rate, and embryo quality at different day of transfer obtained from two different media composition. Our results show that the rate of fertilization and the pregnancy rate were increased using medium added with this particular type of cytokines (GM-CSF).
Physical Review Materials, 2018
High-quality heteroepitaxy of CdTe is challenging due to lattice mismatches of CdTe with many sub... more High-quality heteroepitaxy of CdTe is challenging due to lattice mismatches of CdTe with many substrates. Herein, we demonstrate the epitaxial growth of single crystalline CdTe films, in multilevel island format, on mica using metalorganic chemical vapor deposition, regardless of large in-plane lattice mismatch (~13%) between CdTe(111) and mica(001). X-ray and electron diffractions suggest that CdTe is epitaxially aligned with mica: out-of-plane CdTe 111 //mica 001 and in-plane CdTe 1 21 //mica 010. Full-width-at-half-maximum (FWHM) of X-ray rocking curve and FWHM of X-ray azimuthal in-plane angular dispersion of CdTe are shown to be 0.11 ο and 0.38 ο , respectively, better than most CdTe films reported. Electron backscattering diffraction shows that CdTe grains are tens of μm and, if twin boundaries are excluded, in excess of 250 μm in size. In contrast to the belief that overlayer growth on mica is purely through van der Waals interaction, our first-principle calculations uncover that van der Waals interaction only contributes to 20% of the total interfacial energy, and 80% of the interfacial energy comes from chemical interaction. We believe such a strong chemical interaction is accountable for the highquality epitaxy. The demonstration of epitaxial growth of high-quality semiconductor on mica with a large lattice mismatch creates opportunities for flexible optoelectronic devices.
ACS nano, Jan 27, 2018
We report the use of a single layer of two-dimensional hexagonal boron nitride (SL-hBN) as the th... more We report the use of a single layer of two-dimensional hexagonal boron nitride (SL-hBN) as the thinnest insulating barrier to microbial corrosion induced by the sulfate-reducing bacteria Desulfovibrio alaskensis G20. We used electrochemical methods to assess the corrosion resistance of SL-hBN on copper against the effects of both the planktonic and sessile forms of the sulfate-reducing bacteria. Cyclic voltammetry results show that SL-hBN-Cu is effective in suppressing corrosion effects of the planktonic cells at potentials as high as 0.2 V ( vs Ag/AgCl). The peak anodic current for the SL-hBN coatings is ∼36 times lower than that of bare Cu. Linear polarization resistance tests confirm that the SL-hBN coatings serve as a barrier against corrosive effects of the G20 biofilm when compared to bare Cu. The SL-hBN serves as an impermeable barrier to aggressive metabolites and offers ∼91% corrosion inhibition efficiency, which is comparable to much thicker commercial coatings such as pol...
Body: In the last decade, self-limiting growth of large-area and monolayer graphene sheets has be... more Body: In the last decade, self-limiting growth of large-area and monolayer graphene sheets has been demonstrated on Ge (110) substrates.[1,2] Despite the numerous reports focusing on synthesis of graphene/Ge and the amply recognized technological relevance of this materials combination to electronics, there is a limited understanding of charge transport in graphene along the graphene/Ge growth interface. A major challenge in characterizing carrier concentration and mobilities in graphene/Ge is that chemical vapor deposition (CVD) of high-quality graphene on Ge is performed at a temperature, T>900 °C. At this temperature, even intrinsic Ge has been shown to become p-type due to a large concentration of vacancies.[3,4] CVD grown graphene on Ge is thus bonded to a relatively high-conductance substrate, a feature that makes it difficult to characterize and understand the influence of graphene-Ge interactions on charge transport in this 2D system. In this work we quantify lateral char...