257 results on '"Gerardo Morell"'
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2. Exploring Lead Zirconate Titanate, the Potential Advancement as an Anode for Li-Ion Batteries
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Mohan K. Bhattarai, Shweta Shweta, Sunny Choudhary, Harry M. Meyer, Bishnu P. Thapaliya, Brad R. Weiner, Ram S. Katiyar, and Gerardo Morell
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Chemistry ,QD1-999 - Published
- 2024
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3. Synthesis and Characterization of Carbon-Based Quantum Dots and Doped Derivatives for Improved Andrographolide’s Hydrophilicity in Drug Delivery Platforms
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Nataniel Medina-Berríos, Wenndy Pantoja-Romero, Alexis Lavín Flores, Sebastián C. Díaz Vélez, Anna C. Martínez Guadalupe, Mariana T. Torres Mulero, Kim Kisslinger, Magaly Martínez-Ferrer, Gerardo Morell, and Brad R. Weiner
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Chemistry ,QD1-999 - Published
- 2024
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4. Hydrogenated graphene systems: A novel growth and hydrogenation process
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Samuel Escobar Veras, Ernesto Espada, Solimar Collazo, Marcel Grau, Rajesh Katiyar, Vladimir I. Makarov, Brad R. Weiner, and Gerardo Morell
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SAMs ,Hydrogenation ,Graphene ,Graphane ,Graphone ,Chemistry ,QD1-999 - Abstract
Octadecylphosphonic acid self-assembled monolayers were used as a combined carbon and hydrogen source to grow graphene films on sapphire substrates via hot filament chemical vapor deposition. The functionalized substrates were sealed with a thin Cu film and heated to 950°C under Ar flow. After synthesis, the Cu was etched away. The graphene samples then underwent a hydrogenation treatment in the same reactor setup, exposed to a CH4/H2 gas mixture at 820°C for 2 hours. The structure and properties of the graphene films before and after hydrogenation were characterized. Raman spectroscopy was employed to probe the defect-related bands and C-H bonding. X-ray diffraction provided insights into the crystalline structure and interlayer spacing. The ferromagnetic response was measured using a PPMS system across a range of temperatures and magnetic fields. XPS was used to assess the chemical composition and bonding. This multi-step process enabled a detailed evaluation of the novel synthesis protocol and its effects on the resulting hydrogenated graphene material.
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- 2024
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5. Effective polysulfide control in lithium–sulfur batteries utilizing BiFeO3 nanoparticles
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Mohan K. Bhattarai, Balram Tripathi, Shweta Shweta, Satyam Kumar, Claudia C. Zuluaga-Gómez, Rajesh K. Katiyar, Brad R. Weiner, Ram S. Katiyar, and Gerardo Morell
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Biotechnology ,TP248.13-248.65 ,Physics ,QC1-999 - Abstract
Lithium–sulfur batteries (LiSBs) offer high energy density, cost-effectiveness, and eco-friendliness, making them promising for future energy storage. This study explores using BiFeO3 (BFO) nanoparticles (NPs) to tackle challenges such as lithium polysulfides (LiPs) and shuttle issues in LiSBs. It employs a solid-state melt diffusion technique, encapsulates sulfur in single-walled carbon nanotubes (SCNTs), and utilizes BFO for effective polysulfide control. Herein, composite cathodes of sulfur (S)/SCNTs (abbr. SCNT) were fabricated, and cells were designed using a BFO-coated separator (SCNT-BFS). In addition, a cathode modification was performed with composite S/SCNTs/BFO (SCNT-BF), and a comparative analysis was conducted to assess the effectiveness of the BFO in the separator and the cathode. Cyclic voltammetry measurements revealed that the increased current peak intensity at lower reduction potential in SCNT-BF and SCNT-BFS indicated control of higher-order LiPs (Li2Sx, where 4 ≤ x ≤ 8), resulting in the generation of more stable lower-order products (Li2S2/Li2S). The charge/discharge analysis revealed controlled LiPs, resulting in high-capacity retention in SCNT-BF (∼75%) and SCNT-BFS (∼88%) over 200 cycles, which yielded capacities of 526 and 700 mAh/g at C/8 (1C = 1675 mA/g). These promising results suggest that incorporating BFO into the cathode and separator can advance the commercialization of durable LiSBs.
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- 2024
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6. Comparative Investigation of Water-Based CMC and LA133 Binders for CuO Anodes in High-Performance Lithium-Ion Batteries
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Nischal Oli, Sunny Choudhary, Brad R. Weiner, Gerardo Morell, and Ram S. Katiyar
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CuO ,sodium carboxymethyl cellulose ,carbon matrix ,lithium-ion batteries ,electrochemical reactions ,Organic chemistry ,QD241-441 - Abstract
Transition metal oxides are considered to be highly promising anode materials for high-energy lithium-ion batteries. While carbon matrices have demonstrated effectiveness in enhancing the electrical conductivity and accommodating the volume expansion of transition metal oxide-based anode materials in lithium-ion batteries (LIBs), achieving an optimized utilization ratio remains a challenging obstacle. In this investigation, we have devised a straightforward synthesis approach to fabricate CuO nano powder integrated with carbon matrix. We found that with the use of a sodium carboxymethyl cellulose (CMC) based binder and fluoroethylene carbonate additives, this anode exhibits enhanced performance compared to acrylonitrile multi-copolymer binder (LA133) based electrodes. CuO@CMC electrodes reveal a notable capacity ~1100 mA h g−1 at 100 mA g−1 following 170 cycles, and exhibit prolonged cycling stability, with a capacity of 450 mA h g−1 at current density 300 mA g−1 over 500 cycles. Furthermore, they demonstrated outstanding rate performance and reduced charge transfer resistance. This study offers a viable approach for fabricating electrode materials for next-generation, high energy storage devices.
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- 2024
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7. Enhanced electrochemical performance of Bi2O3 via facile synthesis as anode material for ultra-long cycle lifespan lithium-ion batteries
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Nischal Oli, Wilber Ortiz Lago, Balram Tripathi, Mohan Bhattarai, Brad R. Weiner, Gerardo Morell, and Ram S. Katiyar
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Bismuth oxide ,Long-lasting ,Carboxymethyl cellulose ,Fluoroethylene carbonate ,Lithium-ion batteries ,Industrial electrochemistry ,TP250-261 ,Chemistry ,QD1-999 - Abstract
The urgent demand for stable electrode materials, especially for the anode, arises in the pursuit of high-energy Li-ion batteries. This research focuses on bismuth oxide (Bi2O3) and uncovers its performance through a straightforward, commercially viable synthesis route, along with the optimization of binders and electrolytes. By employing a sodium carboxymethyl cellulose binder and fluoroethylene carbonate additives, the Bi2O3 anode demonstrates significantly enhanced performance compared to prior studies. It attains an impressive initial capacity of approximately 750 mA h g−1, exhibits excellent rate capability at 1000 mA g−1 and maintains stable cycling performance over 6000 cycles.
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- 2024
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8. Water treatment membranes embedded with a stable and bactericidal nanodiamond material
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Abelardo Colon, Javier Avalos, Brad R. Weiner, Gerardo Morell, and Rafael Ríos
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diamond ,drinking water ,membrane filtration ,nano ,water quality ,Public aspects of medicine ,RA1-1270 - Abstract
Filtration has emerged as a critical technology to reduce waterborne diseases caused by poor water quality. Filtration technology presents key challenges, such as membrane selectivity, permeability and biofouling. Nanomaterials can offer solutions to these challenges by varying the membranes' mechanical and bactericidal properties. This research uses nanodiamond particles with facile surface functionality and biocompatibility properties that are added to membranes used for filtration treatments. Scanning and transmission electron microscopy (SEM and TEM) and Fourier transform infrared spectroscopy (FTIR) were performed to study the membrane surface. FTIR spectra confirms an increase in oxygen functional groups onto the ultradispersed diamond's (UDD) surface following acid treatment. SEM images show particle deagglomeration of functionalized UDD at the membrane surface. Tensile strength tests were done to measure the UDD mechanical properties and Coliscan membrane filtration characterization was performed to determine the filter effectiveness. Polyether sulfone (PES) and polyvinylidene (PVDF) membranes expressed a change in their yield point when UDD was incorporated into the porous matrix. A significant microorganism reduction was obtained and confirmed using t-test analysis at a 95% level of confidence. UDD-embedded membranes exhibit a significant bactericidal reduction compared to commercial membranes suggesting these membranes have the potential to enhance current membrane filtration systems. HIGHLIGHTS Carbon nanoparticles, embedded in organic membranes, are used for microbial removal in filtration treatment.; The removal of pathogenic microbes by these organic membranes are enhanced by the incorporation of carbon nanoparticles on their surface, leading to enhanced water filtration treatment.; The mechanical properties of the organic membranes embedded with carbon nanoparticles are modified, creating a membrane with higher or lower yield point depending on the membrane's symmetrical or asymmetrical structure.; The development of these organic/carbon nanoparticle membranes has the potential to enhance their useful lifetime and reduce microbial biofouling, thereby increasing drinking water quality and quantity while reducing operational costs for filtration treatment.;
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- 2023
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9. Role of ferroelectric nanoparticles coated separator in improvement of capacity retention at high current density on sulfur/SWCNT composite cathodes for Li–S batteries
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Rajesh K. Katiyar, Claudia C. Zuluaga Gómez, Swati Katiyar, Balram Tripathi, Gerardo Morell, Brad R. Weiner, and Ram S. Katiyar
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Biotechnology ,TP248.13-248.65 ,Physics ,QC1-999 - Abstract
In this manuscript, we are reporting the role of ferroelectric nanoparticles (FNPs) coated separators in capacity retention at high current density (200 mA/g) on S/SWCNT composite cathodes. The ferroelectric nanoparticles of Bi0.925Gd.075Fe0.95Ni0.05O3 (BGFNO) of spontaneous polarization 2.5 µC/cm2 were coated on commercial separators (PP) as well as doped in sulfur/SWCNT composite cathodes. Our results show a discharge capacity retention of 72% by using commercial separator polypropylene (PP); however, a capacity retention improvement of more than 100% was obtained for FNPs coated separator, which has been placed on the anode side as well as on the cathode side. It is observed that the FNPs coated separator due to spontaneous polarization on the anode and cathode side acts as a repulsive charge on the separator surface to retard polysulfide migration via electrostatic repulsion and protects the surface of lithium from dendrite formation due to which it gains high capacity retention as well as stability. The coated separator controls the transport of carrier ions and side reactions; however, the FNPs doped cathode acts as an absorption center for polysulfides to enhance the electrochemical performance of the cells. The significance of this study is to design an efficient methodology, which could protect electrodes from dendrite formation via coated separator and modified cathode with the FNPs via suppressing the polysulfide formation to achieve high capacity retention and electrochemical cycle stability.
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- 2023
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10. High Areal Capacity and Sustainable High Energy in Ferroelectric Doped Holey Graphene/Sulfur Composite Cathode for Lithium-Sulfur Batteries
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Claudia C. Zuluaga-Gómez, Balram Tripathi, Christian O. Plaza-Rivera, Rajesh K. Katiyar, Margarita Correa, Dhiren K. Pradhan, Gerardo Morell, and Ram S. Katiyar
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polysulfides ,ferroelectric nanoparticles ,holey graphene ,lithium-sulfur batteries ,Production of electric energy or power. Powerplants. Central stations ,TK1001-1841 ,Industrial electrochemistry ,TP250-261 - Abstract
In this study, we are reporting the impact of the incorporation of ferroelectric nanoparticles (FNPs), such as BaTiO3 (BTO), BiFeO3 (BFO), Bi4NdTi3Fe0.7Ni0.3O15 (BNTFN), and Bi4NdTi3Fe0.5Co0.5O15 (BNTFC), as well as the mass loading of sulfur to fabricated solvent-free sulfur/holey graphene-carbon black/polyvinylidene fluoride (S/FNPs/CBhG/PVDF) composite electrodes to achieve high areal capacity for lithium-sulfur (Li-S) batteries. The dry-press method was adopted to fabricate composite cathodes. The hG, a conductive and lightweight scaffold derived from graphene, served as a matrix to host sulfur and FNPs for the fabrication of solvent-free composites. Raman spectra confirmed the dominant hG framework for all the composites, with strong D, G, and 2D bands. The surface morphology of the fabricated cathode system showed a homogeneous distribution of FNPs throughout the composites, confirmed by the EDAX spectra. The observed Li+ ion diffusion coefficient for the composite cathode started at 2.17 × 10−16 cm2/s (S25(CBhG)65PVDF10) and reached up to the highest value (4.15 × 10−15 cm2/s) for S25BNTFC5(CBhG)60PVDF10. The best discharge capacity values for the S25(CBhG)65PVDF10 and S25BNTFC5(CBhG)60PVDF10 composites started at 1123 mAh/gs and 1509 mAh/gs and dropped to 612 mAh/gs and 572 mAh/gs, respectively, after 100 cycles; similar behavior was exhibited by the other composites that were among the best. These are better values than those previously reported in the literature. The incorporation of ferroelectric nanoparticles in the cathodes of Li-S batteries reduced the rapid formation of polysulfides due to their internal electric fields. The areal capacity for the S25(CBhG)65PVDF10 composites was 4.84 mAh/cm2 with a mass loading of 4.31 mgs/cm2, while that for the S25BNTFC5(CBhG)60PVDF10 composites was 6.74 mAh/cm2 with a mass loading of 4.46 mgs/cm2. It was confirmed that effective FNP incorporation within the S cathode improves the cycling response and stability of cathodes, enabling the high performance of Li-S batteries.
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- 2023
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11. Paramagnetism in Microwave-Synthesized Metal-Free Nitrogen-Doped Graphene Quantum Dots
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Flavia P. N. Inbanathan, Katherine Leslee A. Cimatu, David C. Ingram, Uriel Joseph Erasquin, Kiran Dasari, Muhammad Shehzad Sultan, Muhammad Sajjad, Vladimir Makarov, Brad R. Weiner, Gerardo Morell, Payman Sharifi Abdar, and Wojciech M. Jadwisienczak
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NGQDs ,microwave synthesis ,UV-Vis ,fluorescence ,AFM ,TEM ,Technology ,Electrical engineering. Electronics. Nuclear engineering ,TK1-9971 ,Engineering (General). Civil engineering (General) ,TA1-2040 ,Microscopy ,QH201-278.5 ,Descriptive and experimental mechanics ,QC120-168.85 - Abstract
Nitrogen-doped graphene quantum dots (NGQDs) have gained significant attention due to their various physical and chemical properties; however, there is a gap in the study of NGQDs’ magnetic properties. This work adds to the efforts of bridging the gap by demonstrating the room temperature paramagnetism in GQDs doped with Nitrogen up to 3.26 at.%. The focus of this experimental work was to confirm the paramagnetic behavior of metal free NGQDs resulting from the pyridinic N configuration in the GQDs host. Metal-free nitrogen-doped NGQDs were synthesized using glucose and liquid ammonia as precursors by microwave-assisted synthesis. This was followed by dialysis filtration. The morphology, optical, and magnetic properties of the synthesized NGQDs were characterized carefully through atomic force microscopy (AFM), transmission electron microscopy (TEM)), UV-VIS spectroscopy, fluorescence, X-ray photon spectroscopy (XPS), and vibrating sample magnetometer (VSM). The high-resolution TEM analysis of NGQDs showed that the NGQDs have a hexagonal crystalline structure with a lattice fringe of ~0.24 nm of (1120) graphene plane. The N1s peak using XPS was assigned to pyridinic, pyrrolic, graphitic, and oxygenated NGQDs. The magnetic study showed the room-temperature paramagnetic behavior of NGQDs with pyridinic N configuration, which was found to have a magnetization of 20.8 emu/g.
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- 2023
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12. Magnetic Control of the Manganese Photoluminescence in Fe3O4/l‑Cys ZnS:Mn Nanocomposites
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Shyam Sutariya, Mohammed Bsatee, Olesia Gololobova, Daysi Diaz-Diestra, Bibek Thapa, Brad R. Weiner, Gerardo Morell, Wojciech M. Jadwisienczak, and Juan Beltran-Huarac
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Chemistry ,QD1-999 - Published
- 2021
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13. Block Copolymer-Assisted Synthesis of Iron Oxide Nanoparticles for Effective Removal of Congo Red
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Mohan K. Bhattarai, Moses D. Ashie, Sita Dugu, Kiran Subedi, Bishnu P. Bastakoti, Gerardo Morell, and Ram S. Katiyar
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Rietveld ,vibrational study ,IONPs ,block copolymer ,hydrothermal ,adsorption ,Organic chemistry ,QD241-441 - Abstract
Iron oxide nanoparticles (IONPs) were synthesized via a block copolymer-assisted hydrothermal method and the phase purity and the crystal structure were investigated by X-ray diffraction. The Rietveld analysis of X-ray diffractometer spectra shows the hexagonal phase symmetry of α-Fe2O3. Further, the vibrational study suggests Raman active modes: 2A1g + 5Eg associated with α-Fe2O3, which corroborates the Rietveld analysis and orbital analysis of 2PFe. The superparamagnetic behavior is confirmed by magnetic measurements performed by the physical properties measurement system. The systematic study of the Congo red (CR) interaction with IONPs using a UV-visible spectrophotometer and a liquid chromatography–tandem mass spectrometry system equipped with a triple quadrupole mass analyzer and an electrospray ionization interface shows effective adsorption. In visible light, the Fe2O3 nanoparticles get easily excited and generate electrons and holes. The photogenerated electrons reduce the Fe3+ ions to Fe2+ ions. The Fe2+/H2O2 oxidizes CR by the Fenton mechanism. The strong adsorption ability of prepared nanoparticles towards dyes attributes the potential candidates for wastewater treatment and other catalytic applications.
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- 2023
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14. Graphene Film Growth on Silicon Carbide by Hot Filament Chemical Vapor Deposition
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Sandra Rodríguez-Villanueva, Frank Mendoza, Brad R. Weiner, and Gerardo Morell
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graphene ,hot filament chemical vapor deposition ,methane gas ,Chemistry ,QD1-999 - Abstract
The electrical properties of graphene on dielectric substrates, such as silicon carbide (SiC), have received much attention due to their interesting applications. This work presents a method to grow graphene on a 6H-SiC substrate at a pressure of 35 Torr by using the hot filament chemical vapor deposition (HFCVD) technique. The graphene deposition was conducted in an atmosphere of methane and hydrogen at a temperature of 950 °C. The graphene films were analyzed using Raman spectroscopy, scanning electron microscopy, atomic force microscopy, energy dispersive X-ray, and X-ray photoelectron spectroscopy. Raman mapping and AFM measurements indicated that few-layer and multilayer graphene were deposited from the external carbon source depending on the growth parameter conditions. The compositional analysis confirmed the presence of graphene deposition on SiC substrates and the absence of any metal involved in the growth process.
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- 2022
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15. Controlling the transverse proton relaxivity of magnetic graphene oxide
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Bibek Thapa, Daysi Diaz-Diestra, Dayra Badillo-Diaz, Rohit Kumar Sharma, Kiran Dasari, Shalini Kumari, Mikel B. Holcomb, Juan Beltran-Huarac, Brad R. Weiner, and Gerardo Morell
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Medicine ,Science - Abstract
Abstract The engineering of materials with controlled magnetic properties by means other than a magnetic field is of great interest in nanotechnology. In this study, we report engineered magnetic graphene oxide (MGO) in the nanocomposite form of iron oxide nanoparticles (IO)-graphene oxide (GO) with tunable core magnetism and magnetic resonance transverse relaxivity (r2). These tunable properties are obtained by varying the IO content on GO. The MGO series exhibits r2 values analogous to those observed in conventional single core and cluster forms of IO in different size regimes—motional averaging regime (MAR), static dephasing regime (SDR), and echo-limiting regime (ELR) or slow motion regime (SMR). The maximum r2 of 162 ± 5.703 mM−1s−1 is attained for MGO with 28 weight percent (wt%) content of IO on GO and hydrodynamic diameter of 414 nm, which is associated with the SDR. These findings demonstrate the clear potential of magnetic graphene oxide for magnetic resonance imaging (MRI) applications.
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- 2019
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16. Graphene Growth Directly on SiO2/Si by Hot Filament Chemical Vapor Deposition
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Sandra Rodríguez-Villanueva, Frank Mendoza, Alvaro A. Instan, Ram S. Katiyar, Brad R. Weiner, and Gerardo Morell
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graphene ,hot filament chemical vapor deposition ,copper catalytic effect ,Chemistry ,QD1-999 - Abstract
We report the first direct synthesis of graphene on SiO2/Si by hot-filament chemical vapor deposition. Graphene deposition was conducted at low pressures (35 Torr) with a mixture of methane/hydrogen and a substrate temperature of 970 °C followed by spontaneous cooling to room temperature. A thin copper-strip was deposited in the middle of the SiO2/Si substrate as catalytic material. Raman spectroscopy mapping and atomic force microscopy measurements indicate the growth of few-layers of graphene over the entire SiO2/Si substrate, far beyond the thin copper-strip, while X-ray photoelectron spectroscopy and energy-dispersive X-ray spectroscopy showed negligible amounts of copper next to the initially deposited strip. The scale of the graphene nanocrystal was estimated by Raman spectroscopy and scanning electron microscopy.
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- 2021
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17. BiFeO3 Coupled Polysulfide Trapping in C/S Composite Cathode Material for Li-S Batteries as Large Efficiency and High Rate Performance
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Balram Tripathi, Rajesh K. Katiyar, Gerardo Morell, Ambesh Dixit, and Ram S. Katiyar
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Li-S battery ,C/S composite ,BFO coupling ,polysulfide trapping ,Technology - Abstract
We demonstrated the efficient coupling of BiFeO3 (BFO) ferroelectric material within the carbon–sulfur (C-S) composite cathode, where polysulfides are trapped in BFO mesh, reducing the polysulfide shuttle impact, and thus resulting in an improved cyclic performance and an increase in capacity in Li-S batteries. Here, the built-in internal field due to BFO enhances polysulfide trapping. The observation of a difference in the diffusion behavior of polysulfides in BFO-coupled composites suggests more efficient trapping in BFO-modified C-S electrodes compared to pristine C-S composite cathodes. The X-ray diffraction results of BFO–C-S composite cathodes show an orthorhombic structure, while Raman spectra substantiate efficient coupling of BFO in C-S composites, in agreement with SEM images, showing the interconnected network of submicron-size sulfur composites. Two plateaus were observed at 1.75 V and 2.1 V in the charge/discharge characteristics of BFO–C-S composite cathodes. The observed capacity of ~1600 mAh g−1 in a 1.5–2.5 V operating window for BFO30-C10-S60 composite cathodes, and the high cyclic stability substantiate the superior performance of the designed cathode materials due to the efficient reduction in the polysulfide shuttle effect in these composite cathodes.
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- 2021
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18. Enhanced MRI T 2 Relaxivity in Contrast-Probed Anchor-Free PEGylated Iron Oxide Nanoparticles
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Bibek Thapa, Daysi Diaz-Diestra, Juan Beltran-Huarac, Brad R. Weiner, and Gerardo Morell
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PEGylation ,Magnetic iron oxide nanopaticles ,T 2 relaxivity ,MRI contrast agents ,Materials of engineering and construction. Mechanics of materials ,TA401-492 - Abstract
Abstract Superparamagnetic iron oxide nanoparticles (SPIONs, ~11-nm cores) were PEGylated without anchoring groups and studied as efficient MRI T 2 contrast agents (CAs). The ether group of PEG is efficiently and directly linked to the positively charged surface of SPIONs, and mediated through a dipole-cation covalent interaction. Anchor-free PEG-SPIONs exhibit a spin-spin relaxivity of 123 ± 6 mM−1s−1, which is higher than those of PEG-SPIONs anchored with intermediate biomolecules, iron oxide nanoworms, or Feridex. They do not induce a toxic response for Fe concentrations below 2.5 mM, as tested on four different cell lines with and without an external magnetic field. Magnetic resonance phantom imaging studies show that anchor-free PEG-SPIONs produce a significant contrast in the range of 0.1–0.4 [Fe] mM. Our findings reveal that the PEG molecules attached to the cores immobilize water molecules in large regions of ~85 nm, which would lead to blood half-life of a few tens of minutes. This piece of research represents a step forward in the development of next-generation CAs for nascent-stage cancer detection. Graphical Abstract Contrast-probed anchor-free PEGylated iron oxide contrast agent
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- 2017
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19. A graphene integrated highly transparent resistive switching memory device
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Sita Dugu, Shojan P. Pavunny, Tej B. Limbu, Brad R. Weiner, Gerardo Morell, and Ram S. Katiyar
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Biotechnology ,TP248.13-248.65 ,Physics ,QC1-999 - Abstract
We demonstrate the hybrid fabrication process of a graphene integrated highly transparent resistive random-access memory (TRRAM) device. The indium tin oxide (ITO)/Al2O3/graphene nonvolatile memory device possesses a high transmittance of >82% in the visible region (370-700 nm) and exhibits stable and non-symmetrical bipolar switching characteristics with considerably low set and reset voltages (
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- 2018
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20. Fringe structures and tunable bandgap width of 2D boron nitride nanosheets
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Peter Feng, Muhammad Sajjad, Eric Yiming Li, Hongxin Zhang, Jin Chu, Ali Aldalbahi, and Gerardo Morell
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boron nitride sheets ,fringe patterns ,functionalization ,tunable bandgap width ,Technology ,Chemical technology ,TP1-1185 ,Science ,Physics ,QC1-999 - Abstract
We report studies of the surface fringe structures and tunable bandgap width of atomic-thin boron nitride nanosheets (BNNSs). BNNSs are synthesized by using digitally controlled pulse deposition techniques. The nanoscale morphologies of BNNSs are characterized by using scanning electron microscope (SEM), and transmission electron microscopy (TEM). In general, the BNNSs appear microscopically flat in the case of low temperature synthesis, whereas at high temperature conditions, it yields various curved structures. Experimental data reveal the evolutions of fringe structures. Functionalization of the BNNSs is completed with hydrogen plasma beam source in order to efficiently control bandgap width. The characterizations are based on Raman scattering spectroscopy, X-ray diffraction (XRD), and FTIR transmittance spectra. Red shifts of spectral lines are clearly visible after the functionalization, indicating the bandgap width of the BNNSs has been changed. However, simple treatments with hydrogen gas do not affect the bandgap width of the BNNSs.
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- 2014
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21. Synthesis, Characterization and Fabrication of Graphene/Boron Nitride Nanosheets Heterostructure Tunneling Devices
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Muhammad Sajjad, Vladimir Makarov, Frank Mendoza, Muhammad S. Sultan, Ali Aldalbahi, Peter X. Feng, Wojciech M. Jadwisienczak, Brad R. Weiner, and Gerardo Morell
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graphene ,boron nitride nanosheets ,heterostructures ,tunneling device ,2D materials ,Chemistry ,QD1-999 - Abstract
Various types of 2D/2D prototype devices based on graphene (G) and boron nitride nanosheets (BNNS) were fabricated to study the charge tunneling phenomenon pertinent to vertical transistors for digital and high frequency electronics. Specifically, G/BNNS/metal, G/SiO2, and G/BNNS/SiO2 heterostructures were investigated under direct current (DC-bias) conditions at room temperature. Bilayer graphene and BNNS were grown separately and transferred subsequently onto the substrates to fabricate 2D device architectures. High-resolution transmission electron microscopy confirmed the bilayer graphene structure and few layer BNNS sheets having a hexagonal B3-N3 lattice. The current vs voltage I(V) data for the G/BNNS/Metal devices show Schottky barrier characteristics with very low forward voltage drop, Fowler-Nordheim behavior, and 10−4 Ω/sq. sheet resistance. This result is ascribed to the combination of fast electron transport within graphene grains and out-of-plane tunneling in BNNS that circumvents grain boundary resistance. A theoretical model based on electron tunneling is used to qualitatively describe the behavior of the 2D G/BNNS/metal devices.
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- 2019
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22. Study on the optical and electrical properties of tetracyanoethylene doped bilayer graphene stack for transparent conducting electrodes
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Tej B. Limbu, Frank Mendoza, Danilo Barrionuevo, Jennifer Carpena, Benji Maruyama, Ram S. Katiyar, Brad R. Weiner, and Gerardo Morell
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Physics ,QC1-999 - Abstract
We report the optical and electrical properties of chemically-doped bilayer graphene stack by tetracyanoethylene, a strong electron acceptor. The Tetracyanoethylene doping on the bilayer graphene via charge transfer was confirmed by Raman spectroscopy and Infrared Fourier transform spectroscopy. Doped graphene shows a significant increase in the sheet carrier concentration of up to 1.520 × 1013 cm−2 with a concomitant reduction of the sheet resistance down to 414.1 Ω/sq. The high optical transmittance (ca. 84%) in the visible region in combination with the low sheet resistance of the Tetracyanoethylene-doped bilayer graphene stack opens up the possibility of making transparent conducting electrodes for practical applications.
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- 2016
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23. Graphene Oxide/ZnS:Mn Nanocomposite Functionalized with Folic Acid as a Nontoxic and Effective Theranostic Platform for Breast Cancer Treatment
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Daysi Diaz-Diestra, Bibek Thapa, Dayra Badillo-Diaz, Juan Beltran-Huarac, Gerardo Morell, and Brad R. Weiner
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drug delivery ,quantum dots ,reduced graphene oxide ,chemotherapy ,theranostics ,Chemistry ,QD1-999 - Abstract
Nanoparticle-based cancer theranostic agents generally suffer of poor dispersability in biological media, re-agglomeration over time, and toxicity concerns. To address these challenges, we developed a nanocomposite consisting of chemically-reduced graphene oxide combined with manganese-doped zinc sulfide quantum dots and functionalized with folic acid (FA-rGO/ZnS:Mn). We studied the dispersion stability, Doxorubicin (DOX) loading and release efficiency, target specificity, internalization, and biocompatibility of FA-rGO/ZnS:Mn against folate-rich breast cancer cells, and compared to its uncoated counterpart (rGO/ZnS:Mn). The results indicate that DOX is adsorbed on the graphene surface via π–π stacking and hydrophobic interaction, with enhanced loading (~35%) and entrapment (~60%) efficiency that are associated to the chelation of DOX and surface Zn2+ ions. DOX release is favored under acidic conditions reaching a release of up to 95% after 70 h. Membrane integrity of the cells assessed by Lactate dehydrogenase (LDH) release indicate that the surface passivation caused by folic acid (FA) functionalization decreases the strong hydrophobic interaction between the cell membrane wall and the edges/corners of graphene flakes. Chemotherapeutic effect assays reveal that the cancer cell viability was reduced up to ~50% at 3 µg/mL of DOX-FA-rGO/ZnS:Mn exposure, which is more pronounced than those obtained for free DOX at the same doses. Moreover, DOX-rGO/ZnS:Mn did not show any signs of toxicity. An opposite trend was observed for cells that do not overexpress the folate receptors, indicating that FA functionalization endows rGO/ZnS:Mn with an effective ability to discriminate positive folate receptor cancerous cells, enhancing its drug loading/release efficiency as a compact drug delivery system (DDS). This study paves the way for the potential use of functionalized rGO/ZnS:Mn nanocomposite as a platform for targeted cancer treatment.
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- 2018
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24. La enseñanza del voleibol a través de las situaciones simplificadas de juego en la Educación Física en la enseñanza media
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Pedro Morell Rico, Gerardo Morell Rico, and Marislén Mato González
- Subjects
Sports ,GV557-1198.995 - Abstract
El trabajo es una investigación llevada a cabo en la enseñanza del voleibol a través del modelo basado en las Situaciones Simplificadas de Juego con el objetivo de demostrar que los alumnos aumentan la tasa de aprendizaje, el mismo se realizó en la ESBU “Ricardo Rey González Figueredo” de la ciudad de Ciego de Ávila, con 4 grupos de 9no grado en el sexo masculino, y se comparó los resultados alcanzados con el modelo de enseñanza que se aplica en la actualidad. Para ello se utilizaron test técnicos y técnico tácticos con el objetivo de determinar el desarrollo en el mismo nivel de los alumnos al iniciar y finalizar el período de clase, llegando a la conclusión de que en el aspecto técnico la influencia de ambos modelos en su desarrollo es similar, no comportándose así en el aspecto táctico donde es superior el resultado en los alumnos que recibieron las clases a través del modelo basado en las Situaciones Simplificadas de juego, por lo que se recomienda la aplicación del trabajo por la importancia que reviste, dotando a los docentes de una nueva forma de enfrentar el proceso de enseñanza aprendizaje del voleibol en la Educación Físicaaplicado al contexto, influyendo en la calidad de las clases y en la formación integral de los estudiantes.
- Published
- 2007
25. Unipolar resistive switching in planar Pt/BiFeO3/Pt structure
- Author
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Rajesh K. Katiyar, Yogesh Sharma, Danilo G. Barrionuevo Diestra, Pankaj Misra, Sudheendran Kooriyattil, Shojan P. Pavunny, Gerardo Morell, Brad R. Weiner, J. F. Scott, and Ram S. Katiyar
- Subjects
Physics ,QC1-999 - Abstract
We report unipolar resistive switching suitable for nonvolatile memory applications in polycrystalline BiFeO3 thin films in planar electrode configuration with non-overlapping Set and Reset voltages, On/Off resistance ratio of ∼104 and good data retention (verified for up to 3,000 s). We have also observed photovoltaic response in both high and low resistance states, where the photocurrent density was about three orders of magnitude higher in the low resistance state as compared to the high resistance state at an illumination power density of ∼100 mW/cm2. Resistive switching mechanisms in both resistance states of the planar device can be explained by using the conduction filament (thermo-chemical) model.
- Published
- 2015
- Full Text
- View/download PDF
26. Binder Free SnO2-CNT Composite as Anode Material for Li-Ion Battery
- Author
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Dionne Hernandez, Frank Mendoza, Emmanuel Febus, Brad R. Weiner, and Gerardo Morell
- Subjects
Technology (General) ,T1-995 - Abstract
Tin dioxide-carbon nanotube (SnO2-CNT) composite films were synthesized on copper substrates by a one-step process using hot filament chemical vapor deposition (HFCVD) with methane gas (CH4) as the carbon source. The composite structural properties enhance the surface-to-volume ratio of SnO2 demonstrating a desirable electrochemical performance for a lithium-ion battery anode. The SnO2 and CNT interactions were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared-attenuated total reflectance (ATR-FTIR) spectroscopy. Comprehensive analysis of the structural, chemical, and electrochemical properties reveals that the material consists of self-assembled and highly dispersed SnO2 nanoparticles in CNT matrix. The process employed to develop this SnO2-CNT composite film presents a cost effective and facile way to develop anode materials for Li-ion battery technology.
- Published
- 2014
- Full Text
- View/download PDF
27. Holey Graphene/Ferroelectric/Sulfur Composite Cathodes for High-Capacity Lithium–Sulfur Batteries
- Author
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Claudia C. Zuluaga-Gómez, Christian O. Plaza-Rivera, Balram Tripathi, Rajesh K. Katiyar, Dhiren K. Pradhan, Gerardo Morell, Yi Lin, Margarita Correa, and Ram S. Katiyar
- Published
- 2023
- Full Text
- View/download PDF
28. T1- and T2-weighted Magnetic Resonance Dual Contrast by Single Core Truncated Cubic Iron Oxide Nanoparticles with Abrupt Cellular Internalization and Immune Evasion
- Author
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Bibek Thapa, Daysi Diaz-Diestra, Carlene Santiago-Medina, Nitu Kumar, Kaixiong Tu, Juan Beltran-Huarac, Wojciech M. Jadwisienczak, Brad R. Weiner, and Gerardo Morell
- Published
- 2018
- Full Text
- View/download PDF
29. A Novel Approach to the Layer-Number-Controlled and Grain-Size-Controlled Growth of High Quality Graphene for Nanoelectronics
- Author
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Tej B. Limbu, Jean C. Hernández, Frank Mendoza, Rajesh K. Katiyar, Joshua James Razink, Vladimir I. Makarov, Brad R. Weiner, and Gerardo Morell
- Published
- 2018
- Full Text
- View/download PDF
30. Size Characterization of Graphene‐coated Silver Nanoparticles for Drug Delivery System Design
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Anna C. Martinez Guadalupe, Brad Weiner, Gerardo Morell, Nataniel Medina, Wenndy Pantoja, and Alexis Lavin
- Subjects
Genetics ,Molecular Biology ,Biochemistry ,Biotechnology - Published
- 2022
31. Abstract 1955: Intracellular SERS detection of nanoparticle drug delivery platforms
- Author
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Nataniel Medina, Sebastián Díaz-Vélez, Rafael Villanueva, Alondra Veloz, Brad Weiner, and Gerardo Morell
- Subjects
Cell Biology ,Molecular Biology ,Biochemistry - Published
- 2023
32. Abstract 2010: Graphene Quantum Dots- covered AuAg alloy nanoparticles as Drug Delivery Platforms for Anticancer Applications
- Author
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Alondra Veloz, Gerardo Morell, Brad Weiner, and Nataniel Medina
- Subjects
Cell Biology ,Molecular Biology ,Biochemistry - Published
- 2023
33. Abstract 1801: Graphene Quantum Dots as Drug Delivery Platforms for Anti-Cancer Applications
- Author
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Rafael Villanueva, Nataniel Medina, Alondra Veloz, Tori Cole, Anna Martinez, Brad Weinner, and Gerardo Morell
- Subjects
Cell Biology ,Molecular Biology ,Biochemistry - Published
- 2023
34. Ultrananocrystalline Diamond-Decorated Silicon Nanowire Field Emitters
- Author
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Javier Palomino, Deepak Varshney, Oscar Resto, Brad R. Weiner, and Gerardo Morell
- Published
- 2014
- Full Text
- View/download PDF
35. Solar-blind field-emission diamond ultraviolet detector
- Author
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Frank Mendoza, Vladimir Makarov, Brad R. Weiner, and Gerardo Morell
- Published
- 2015
- Full Text
- View/download PDF
36. Studies of the switchable photovoltaic effect in co-substituted BiFeO3 thin films
- Author
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Rajesh K. Katiyar, Yogesh Sharma, Pankaj Misra, Venkata S. Puli, Satyaprakash Sahoo, Ashok Kumar, James F. Scott, Gerardo Morell, Brad R. Weiner, and Ram S. Katiyar
- Published
- 2014
- Full Text
- View/download PDF
37. Switchable photovoltaic effect in bilayer graphene/BiFeO3/Pt heterostructures
- Author
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Rajesh K. Katiyar, Pankaj Misra, Frank Mendoza, Gerardo Morell, and Ram S. Katiyar
- Published
- 2014
- Full Text
- View/download PDF
38. Advances in 1D Materials
- Author
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Gerardo Morell, Brad R. Weiner, and Javier Palomino
- Subjects
Engineering ,business.industry ,business - Published
- 2020
39. A Novel Approach to the Layer-Number-Controlled and Grain-Size-Controlled Growth of High Quality Graphene for Nanoelectronics
- Author
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Frank Mendoza, Tej B. Limbu, Jean Carlos Hernández, Gerardo Morell, Rajesh K. Katiyar, Brad R. Weiner, Vladimir I. Makarov, and Joshua J. Razink
- Subjects
Materials science ,business.industry ,Graphene ,Field effect ,02 engineering and technology ,Chemical vapor deposition ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Grain size ,0104 chemical sciences ,law.invention ,Nanoelectronics ,law ,Monolayer ,Optoelectronics ,General Materials Science ,Crystallite ,0210 nano-technology ,Bilayer graphene ,business - Abstract
Thermal chemical vapor decomposition of methane on copper is the most widely employed technique for high quality and large area graphene growth. Graphene growth by this technique tends to be limited to a monolayer owing to the surface mediated self-limiting growth mechanism, and hence, it is difficult to obtain continuous bilayers and multilayers. We report the layer-controlled growth of high quality and large area polycrystalline graphene on copper foil in a hot filament chemical vapor deposition (HFCVD) reactor and demonstrate that graphene can be grown with a controlled grain size in the range of 5–16 μm. The field effect hole mobilities of the largest grain monolayer and bilayer graphene and the thickest few-layer graphene are 4310 ± 348, 2745 ± 276, and 2472 ± 185 cm2V–1s–1, respectively, which are comparable to that of high quality polycrystalline graphene and suitable for future nanoelectronics. The results of the systematic parametric study hereby presented indicate that graphene adlayers grow on ...
- Published
- 2018
40. Straightforward Deposition of Uniform Boron Nitride Coatings by Chemical Vapor Deposition
- Author
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J. E. Nocua and Gerardo Morell
- Subjects
Materials science ,Scanning electron microscope ,020502 materials ,Mechanical Engineering ,Electron energy loss spectroscopy ,02 engineering and technology ,Chemical vapor deposition ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,chemistry.chemical_compound ,0205 materials engineering ,Chemical engineering ,X-ray photoelectron spectroscopy ,chemistry ,Mechanics of Materials ,Transmission electron microscopy ,Boron nitride ,Deposition (phase transition) ,General Materials Science ,Fourier transform infrared spectroscopy ,0210 nano-technology - Abstract
Boron nitride (BN) has a very high thermal conductivity and excellent thermal shock resistance. These properties make BN an important material for industrial applications involving surfaces in contact with molten metals. These applications require straightforward deposition methods that produce uniform BN coatings. Using borazine (B3N3H6) as a precursor, we deposited BN coatings on silicon substrates by cold-wall chemical vapor deposition (CVD). The microstructure, composition, and morphology of the coatings were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), and electron energy loss spectroscopy (EELS). These characterizations show that the BN coatings deposited are uniform, predominantly of hexagonal structure, and N-rich.
- Published
- 2018
41. Grain size-dependent thermal conductivity of polycrystalline twisted bilayer graphene
- Author
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Brad R. Weiner, Frank Mendoza, Tej B. Limbu, Gerardo Morell, Konstanze R. Hahn, Joshua J. Razink, Ram S. Katiyar, and Satyaprakash Sahoo
- Subjects
Materials science ,Chemistry(all) ,Bilayer ,Analytical chemistry ,Nanotechnology ,02 engineering and technology ,General Chemistry ,Chemical vapor deposition ,021001 nanoscience & nanotechnology ,01 natural sciences ,Grain size ,Thermal conductivity ,0103 physical sciences ,General Materials Science ,Grain boundary ,Crystallite ,010306 general physics ,0210 nano-technology ,Bilayer graphene ,Single crystal - Abstract
We report the room temperature thermal conductivity of polycrystalline twisted bilayer graphene (tBLG) as a function of grain size measured by employing a noncontact optical technique based on micro-Raman spectroscopy. Polycrystalline tBLG sheets of different grain sizes were synthesized on copper by hot filament chemical vapor deposition. The thermal conductivity values are 1305 ± 122 , 971 ± 73 , and 657 ± 42 W m − 1 K − 1 for polycrystalline tBLG with average grain sizes of 54, 21, and 8 nm, respectively. Based on these thermal conductivity values, we also estimated the grain boundary conductance, 14.43 ± 1.21 × 10 10 W m − 2 K − 1 , and the thermal conductivity for single crystal tBLG, 1510 ± 103 W m − 1 K − 1 . Our results show that the relative degradation of thermal conductivity due to grain boundaries is smaller in bilayer than in monolayer graphene. Molecular dynamics simulations indicate that interlayer interactions play an important role in the heat conductivity of polycrystalline bilayer graphene. The quantitative study of the grain size dependent thermal conductivity of polycrystalline bilayer graphene is valuable in technological applications as well as for fundamental scientific understanding.
- Published
- 2017
- Full Text
- View/download PDF
42. Photovoltaic Effect in ITO/rGO/BFO/Au Heterostructures
- Author
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Frank Mendoza, Radhe Agarwal, Ram S. Katiyar, Gerardo Morell, and Yogesh Sharma
- Subjects
Materials science ,business.industry ,Optoelectronics ,Heterojunction ,Photovoltaic effect ,business ,Algorithm - Abstract
In recent years, BiFeO3 (BFO) thin films showed promising potential towards photovoltaic applications due to its superior ferroelectric properties and optical bandgap lies in the visible region. Among other wide bandgap ferroelectric photovoltaic (Fe-PV) materials (i.e. BaTiO3, LiNbO3 and Pb(Zr,Ti)O3), BFO exhibits large open circuit voltage (VOC), tunable output, and switchable photovoltaic effect. It has been reported that insertion of semiconductor layer to a conventional metal/ferroelectric/metal structure can result into novel heterostructures based photovoltaic cells. However, integration of novel carbon materials in ferroelectric photovoltaic devices has not been very popular. We have studied photovoltaic effect in In2O3-Sn2O3 (ITO)/reduced graphene oxide (rGO)/BiFeO3/Au (metal/semiconductor/ferroelectric/metal heterostructure). We have synthesized graphene oxide using modified hummers method. We spin coated GO solution on ITO substrate and dried overnight at 50oC to achieve thin films. Resultant GO thin films were annealed in NH3:H2 (3:1) atmosphere at 600oC. Electrical measurements confirmed n-type doping in thermally reduced GO (rGO) films. Whereas, BFO act as p-type semiconductor due to charge defects mainly, Oxygen vacancies. BFO films were grown using pulsed laser deposition technique. ITO/rGO/BFO/Au heterostructures shows a reasonable photovoltaic response. Such heterostructure shows short-cicuit current density of 86 µA/cm2. We believe that two built-in fields generated at Au/BFO and BFO/rGO interface are responsible for separation and transport of photo-excited electron-hole pairs. Our work may provide a new way to integrate carbon materials to ferroelectrics to produce heterojunction based solar cells.
- Published
- 2017
43. Observation of the C 2 H radical using (1 + 2) REMPI via theB̃2A′←X̃2Σ+transition
- Author
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Dachun Huang, Kenneth J. Pérez Quintero, Brad R. Weiner, Vladimir I. Makarov, Arturo Hidalgo, Tej B. Limbu, and Gerardo Morell
- Subjects
010304 chemical physics ,Photodissociation ,Buffer gas ,Analytical chemistry ,General Physics and Astronomy ,chemistry.chemical_element ,02 engineering and technology ,021001 nanoscience & nanotechnology ,01 natural sciences ,Nitrogen ,chemistry.chemical_compound ,chemistry ,Acetylene ,Relaxation rate ,0103 physical sciences ,Relaxation (physics) ,Physical and Theoretical Chemistry ,0210 nano-technology ,Spectroscopy - Abstract
We report the detection of the ethynyl (C2H) radical by (1 + 2) REMPI on the B 2 A ′ ( T , K a = 0 , 1 , 2 ) ← X 2 Σ + ( 0 , 3 1 , 0 ) transition. One parallel, B 2 A ′ ( T , K a = 1 ) ← X 2 Σ + ( 0 , 3 1 , 0 ) with E eV = 37 , 946 cm - 1 , and two perpendicular transitions, B 2 A ′ ( T , K a = 0 ) ← X 2 Σ + ( 0 , 3 1 , 0 ) with E eV = 37 , 927 cm - 1 and B 2 A ′ ( T , K a = 2 ) ← X 2 Σ + ( 0 , 3 1 , 0 ) with E eV = 38 , 002 cm - 1 , are observed. The C2H radical was generated by the photodissociation of C2H2 at 193 nm. By employing REMPI spectroscopy, we also studied the collisional induced rotational relaxation of C2H and measured rotational relaxation rate constants for this radical. The measured rotational relaxation rate constants for several values of J″ are ( 0.08 – 0.26 ) × 10 - 9 cm 3 molec - 1 s - 1 and ( 0.75 – 1.92 ) × 10 - 9 cm 3 molec - 1 s - 1 for nitrogen buffer gas and acetylene, respectively.
- Published
- 2016
44. Field emission properties of carbon nanowalls prepared by RF magnetron sputtering
- Author
-
Rodrigo Espinoza-González, F. Guzmán-Olivos, Victor M. Fuenzalida, and Gerardo Morell
- Subjects
010302 applied physics ,Argon ,Materials science ,Hydrogen ,Silicon ,Analytical chemistry ,chemistry.chemical_element ,02 engineering and technology ,General Chemistry ,Substrate (electronics) ,Sputter deposition ,021001 nanoscience & nanotechnology ,01 natural sciences ,Field electron emission ,Carbon film ,chemistry ,Transmission electron microscopy ,0103 physical sciences ,General Materials Science ,0210 nano-technology - Abstract
Carbon nanowalls were prepared on silicon substrates by radio frequency magnetron sputtering under an argon–hydrogen mixture, at different hydrogen fluxes and varying the substrate temperature and deposition times. Scanning and transmission electron microscopy showed that carbon films deposited at 510 °C are nanostructured polycrystalline carbon nanowalls with crystals of about 3 nm inside the flakes. The hydrogen flow induces the growth of nanowalls oriented perpendicularly to the substrate, and the density (amount) of these nanowalls decrease as the hydrogen flow increases. Field emission measurements showed that carbon nanowalls grown in hydrogen have a turn-on voltage of 2.0 V/µm, lower than those grown in pure argon with 4.5 V/µm.
- Published
- 2019
45. Synergistic antibacterial activity of PEGylated silver–graphene quantum dots nanocomposites
- Author
-
Khaled Habiba, Javier A. Avalos, Gerardo Morell, Darinel Ortiz, Carlos I. González, José A. González-Feliciano, Dina P. Bracho-Rincon, Vladimir I. Makarov, Brad R. Weiner, and Juan C. Villalobos-Santos
- Subjects
Antibacterial nanoparticles ,Materials science ,Toxicity ,Graphene quantum dots ,Silver nanocomposites ,General Materials Science ,Nanotechnology ,Nanocomposites - Abstract
The emergence of antibiotic-resistant bacteria is a major threat to world-wide public health. Functionalized nanoparticles could offer novel strategies in this post-antibiotic era. In this study, we developed nanocomposites of silver nanoparticles decorated with graphene quantum dots (Ag-GQDs) using pulsed laser synthesis. The nanocomposites were PEGylated, which increases their biocompatibility and solubility in aqueous solutions. The HR-TEM micrographs of bare GQDs show that their size is in the range of 1.6–4nm, and the lattice spacing is 0.214nm, which corresponds to the (100) lattice fringes of graphene. The antibacterial activity of Ag-GQDs was evaluated and compared to that of bare GQDs and commercial silver nanoparticles (Ag-NPs) against both Gram-negative and Gram-positive bacteria, using Pseudomonas aeruginosa and Staphylococcus aureus as model bacteria, respectively. Concentration values of 25 and 50μg/mL are required for Ag-GQDs to inhibit the growth of S. aureus and P. aeruginosa bacteria, respectively. The fractional inhibitory concentration (FIC) index is below 0.5 indicating that there is a synergistic effect between Ag-NPs and GQDs. Kirby–Bauer tests showed that Ag-GQDs inhibit P. aeruginosa and S. aureus, in contrast to bare GQDs and Ag-NPs alone. Cell viability of normal mammalian cells treated with Ag-GQDs showed that cell viability is maintained at 100% for cells incubated with Ag-GQDs. The decoration of Ag-NPs with GQDs minimizes their cytotoxicity in mammalian cells and increases their biocompatibility. Ag-GQDs have potential applications in the fabrication of antibacterial coatings, self-sterile textiles, and personal care products.
- Published
- 2015
46. Graphene modulated LiMn1.5Ni0.4Cr0.1O4 spinel cathode for lithium ion battery
- Author
-
Balram Tripathi, Gerardo Morell, Rajesh K. Katiyar, Ram S. Katiyar, Shiva Adireddy, Brad R. Weiner, Atul Tiwari, Ambesh Dixit, and Javier Palomino
- Subjects
High energy ,Materials science ,Chemical engineering ,Graphene ,law ,Spinel ,engineering ,engineering.material ,Cathode ,Lithium-ion battery ,law.invention - Abstract
We report the development of a rechargeable lithium ion battery with homogeneous mixing of 10% of graphene oxide in active LiMn1.5Ni0.4Cr0.1O4 cathode material for enhanced electrochemical performance. The redox behavior of the cell, which is normally too slow for practical applications, is accelerated with highly conductive graphene. Intimate mixing of the two materials is achieved by a slurry maker using an organic solution for a cathode paste. The fabricated electrode is repeatedly charged/discharge at C/10 and C/2 rates without any significant degradation in the electrochemical capacity. The gravimetric energy density of the composite cathode material exceeds that of the LiMn1.5Ni0.4Cr0.1O4 oxide electrode in lithium-ion batteries, and the addition of graphene in active material is likely to prove advantageous in applications where weight, rather than volume, is a critical factor.
- Published
- 2020
47. Graphene Oxide/ZnS:Mn Nanocomposite Functionalized with Folic Acid as a Nontoxic and Effective Theranostic Platform for Breast Cancer Treatment
- Author
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Bibek Thapa, Dayra Badillo-Diaz, Daysi Diaz-Diestra, Juan Beltran-Huarac, Gerardo Morell, and Brad R. Weiner
- Subjects
theranostics ,Biocompatibility ,General Chemical Engineering ,Nanoparticle ,quantum dots ,02 engineering and technology ,010402 general chemistry ,chemotherapy ,01 natural sciences ,reduced graphene oxide ,Article ,law.invention ,lcsh:Chemistry ,chemistry.chemical_compound ,law ,General Materials Science ,Chelation ,Chemistry ,Graphene ,021001 nanoscience & nanotechnology ,Zinc sulfide ,0104 chemical sciences ,3. Good health ,lcsh:QD1-999 ,Folate receptor ,Drug delivery ,drug delivery ,Surface modification ,0210 nano-technology ,Nuclear chemistry - Abstract
Nanoparticle-based cancer theranostic agents generally suffer of poor dispersability in biological media, re-agglomeration over time, and toxicity concerns. To address these challenges, we developed a nanocomposite consisting of chemically-reduced graphene oxide combined with manganese-doped zinc sulfide quantum dots and functionalized with folic acid (FA-rGO/ZnS:Mn). We studied the dispersion stability, Doxorubicin (DOX) loading and release efficiency, target specificity, internalization, and biocompatibility of FA-rGO/ZnS:Mn against folate-rich breast cancer cells, and compared to its uncoated counterpart (rGO/ZnS:Mn). The results indicate that DOX is adsorbed on the graphene surface via &pi, &ndash, &pi, stacking and hydrophobic interaction, with enhanced loading (~35%) and entrapment (~60%) efficiency that are associated to the chelation of DOX and surface Zn2+ ions. DOX release is favored under acidic conditions reaching a release of up to 95% after 70 h. Membrane integrity of the cells assessed by Lactate dehydrogenase (LDH) release indicate that the surface passivation caused by folic acid (FA) functionalization decreases the strong hydrophobic interaction between the cell membrane wall and the edges/corners of graphene flakes. Chemotherapeutic effect assays reveal that the cancer cell viability was reduced up to ~50% at 3 µ, g/mL of DOX-FA-rGO/ZnS:Mn exposure, which is more pronounced than those obtained for free DOX at the same doses. Moreover, DOX-rGO/ZnS:Mn did not show any signs of toxicity. An opposite trend was observed for cells that do not overexpress the folate receptors, indicating that FA functionalization endows rGO/ZnS:Mn with an effective ability to discriminate positive folate receptor cancerous cells, enhancing its drug loading/release efficiency as a compact drug delivery system (DDS). This study paves the way for the potential use of functionalized rGO/ZnS:Mn nanocomposite as a platform for targeted cancer treatment.
- Published
- 2018
48. Synthesis, Optical, and Magnetic Properties of Graphene Quantum Dots and Iron Oxide Nanocomposites
- Author
-
M. S. Sultan, M. Sajjad, Brad R. Weiner, Vladimir I. Makarov, Gerardo Morell, and Wojciech M. Jadwisienczak
- Subjects
Photoluminescence ,Materials science ,Article Subject ,business.industry ,Graphene ,General Engineering ,Nanoparticle ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Nanomaterials ,law.invention ,Ferromagnetism ,Quantum dot ,law ,lcsh:TA401-492 ,Optoelectronics ,Magnetic nanoparticles ,General Materials Science ,lcsh:Materials of engineering and construction. Mechanics of materials ,0210 nano-technology ,business ,High-resolution transmission electron microscopy - Abstract
The combination of nanomaterial graphene quantum dots (GQDs) with magnetic nanoparticles offers a unique set of optical and magnetic properties for future energy and medical applications. We report on the synthesis and engineering of GQDs and iron oxide (Fe3O4) nanocomposites (NCs) by using a pulsed laser discharge technique. High-resolution transmission electron microscopy (HRTEM) images showed a high yield of pure GQDs with 2–10 nm diameter. The hexagonal structures and lattice fringes associated with the C–C bond in GQDs were clearly identifiable. The structural and optical changes in GQDs and GQDs-Fe3O4 NC samples induced by UV light were investigated by the absorption and emission spectroscopy over the deep UV–visible spectral range. The photoluminescence spectra have shown subband π→π∗ transitions in GQDs-Fe3O4 NC. Magnetic properties of the GQDs-Fe3O4 NC samples have shown room temperature ferromagnetism induced by pure Fe3O4 nanoparticles and from the substantial spin polarized edges of GQD nanoparticles. It is concluded that the observed optical and magnetic properties could be further tailored in the studied nanocomposites for prospective medical applications.
- Published
- 2018
49. Study of the Structural Changes Undergone by Hybrid Nanostructured Si-CNTs Employed as an Anode Material in a Rechargeable Lithium-Ion Battery
- Author
-
Javier Palomino, Gerardo Morell, Deepak Varshney, and Brad R. Weiner
- Subjects
Thermogravimetric analysis ,Materials science ,Electron energy loss spectroscopy ,chemistry.chemical_element ,Chemical vapor deposition ,Electrochemistry ,Lithium-ion battery ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Anode ,General Energy ,Chemical engineering ,chemistry ,Lithium ,Physical and Theoretical Chemistry ,Cyclic voltammetry - Abstract
Silicon–carbon nanotube (Si-CNT) hybrid structures have been fabricated in a single step on Cu substrate by hot filament chemical vapor deposition (HFCVD). A mixture of straight chain saturated aliphatic polymer and Si nanoparticles was used as the seeding source. The material was analyzed by transmission electron microscopy (TEM) and electron energy loss spectroscopy (EELS), and the Si content in the Si-CNT was estimated to be ∼15% wt % by thermogravimetric analysis (TGA). Thereafter, the films were used for lithium-ion battery (LIB) anodes, whose cyclic voltammetry studies show redox peaks for Si and C consistent with lithium insertion/extraction, indicating good reversibility over extensive cycling. Electrochemical tests showed that Si-CNT electrodes can deliver an initial high discharge capacity of ∼700 mAh/g and a reversible capacity of ∼500 mAh/g over 520 cycles. After electrochemical cycling, the Si-CNTs were analyzed and compared to pristine material. The cycled films showed an increment of Si-CNT...
- Published
- 2015
50. Catalytic effect of ultrananocrystalline Fe3O4on algal bio-crude productionviaHTL process
- Author
-
Juan Beltran-Huarac, Keshav C. Das, Daysi Diaz-Diestra, Gerardo Morell, Brad R. Weiner, Arnulfo Rojas-Pérez, Liz M. Díaz-Vázquez, and Cecilia B. Frias-Flores
- Subjects
Chemistry ,chemistry.chemical_element ,Heterogeneous catalysis ,Nanomaterial-based catalyst ,Catalysis ,Hydrothermal liquefaction ,chemistry.chemical_compound ,Chemical engineering ,Yield (chemistry) ,Phenol ,Organic chemistry ,General Materials Science ,Fourier transform infrared spectroscopy ,Carbon - Abstract
We report a comprehensive quantitative study of the production of refined bio-crudes via a controlled hydrothermal liquefaction (HTL) process using Ulva fasciata macroalgae (UFMA) as biomass and ultrananocrystalline Fe3O4 (UNCFO) as catalyst. X-ray diffraction and electron microscopy were applied to elucidate the formation of the high-quality nanocatalysts. Gas chromatography-mass spectroscopy (GC-MS) and CHNS analyses showed that the bio-crude yield and carbon/oxygen ratios increase as the amount of UNCFO increases, reaching a peak value of 32% at 1.25 wt% (a 9% increase when compared to the catalyst-free yield). The bio-crude is mainly composed of fatty acids, alcohols, ketones, phenol and benzene derivatives, and hydrocarbons. Their relative abundance changes as a function of catalyst concentration. FTIR spectroscopy and vibrating sample magnetometry revealed that the as-produced bio-crudes are free of iron species, which accumulate in the generated bio-chars. Our findings also indicate that the energy recovery values via the HTL process are sensitive to the catalyst loading, with a threshold loading of 1.25 wt%. GC-MS studies show that the UNCFO not only influences the chemical nature of the resulting bio-crudes and bio-chars, but also the amount of fixed carbons in the solid residues. The detailed molecular characterization of the bio-crudes and bio-chars catalyzed by UNCFO represents the first systematic study reported using UFMA. This study brings forth new avenues to advance the highly-pure bio-crude production employing active, heterogeneous catalyst materials that are recoverable and recyclable for continuous thermochemical reactions.
- Published
- 2015
Catalog
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