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Nguyen DK, Vargheese V, Liao V, Dimitrakellis P, Sourav S, Zheng W, Vlachos DG. Plasma-Enabled Ligand Removal for Improved Catalysis: Furfural Conversion on Pd/SiO 2. ACS Nano 2023; 17:21480-21492. [PMID: 37906709 DOI: 10.1021/acsnano.3c06310] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/02/2023]
Abstract
A nonthermal, atmospheric He/O2 plasma (NTAP) successfully removed polyvinylpyrrolidone (PVP) from Pd cubic nanoparticles supported on SiO2 quickly and controllably. Transmission electron microscopy (TEM) revealed that the shape and size of Pd nanoparticles remain intact during plasma treatment, unlike mild calcination, which causes sintering and polycrystallinity. Using Fourier transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS), we demonstrate the quantitative estimation of the PVP plasma removal rate and control of the nanoparticle synthesis. First-principles calculations of the XPS and CO FTIR spectra elucidate electron transfer from the ligand to the metal and allow for estimates of ligand coverages. Reactivity testing indicated that PVP surface crowding inhibits furfural conversion but does not alter furfural selectivity. Overall, the data demonstrate NTAP as a more efficient method than traditional calcination for organic ligand removal in nanoparticle synthesis.
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Affiliation(s)
- Darien K Nguyen
- Department of Chemical and Biomolecular Engineering, University of Delaware, 150 Academy Street, Newark, Delaware 19716, United States
- RAPID Manufacturing Institute, Delaware Energy Institute (DEI), Newark, Delaware 19716, United States
| | - Vibin Vargheese
- Department of Chemical and Biomolecular Engineering, University of Delaware, 150 Academy Street, Newark, Delaware 19716, United States
- RAPID Manufacturing Institute, Delaware Energy Institute (DEI), Newark, Delaware 19716, United States
| | - Vinson Liao
- Department of Chemical and Biomolecular Engineering, University of Delaware, 150 Academy Street, Newark, Delaware 19716, United States
- RAPID Manufacturing Institute, Delaware Energy Institute (DEI), Newark, Delaware 19716, United States
| | - Panagiotis Dimitrakellis
- Department of Chemical and Biomolecular Engineering, University of Delaware, 150 Academy Street, Newark, Delaware 19716, United States
- RAPID Manufacturing Institute, Delaware Energy Institute (DEI), Newark, Delaware 19716, United States
| | - Sagar Sourav
- Department of Chemical and Biomolecular Engineering, University of Delaware, 150 Academy Street, Newark, Delaware 19716, United States
- RAPID Manufacturing Institute, Delaware Energy Institute (DEI), Newark, Delaware 19716, United States
| | - Weiqing Zheng
- Catalysis Center for Energy Innovation, University of Delaware, 150 Academy Street, Newark, Delaware 19716, United States
- RAPID Manufacturing Institute, Delaware Energy Institute (DEI), Newark, Delaware 19716, United States
| | - Dionisios G Vlachos
- Department of Chemical and Biomolecular Engineering, University of Delaware, 150 Academy Street, Newark, Delaware 19716, United States
- Catalysis Center for Energy Innovation, University of Delaware, 150 Academy Street, Newark, Delaware 19716, United States
- RAPID Manufacturing Institute, Delaware Energy Institute (DEI), Newark, Delaware 19716, United States
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Yalcin O, Sourav S, Wachs IE. Design of Cr-Free Promoted Copper-Iron Oxide-Based High-Temperature Water-Gas Shift Catalysts. ACS Catal 2023; 13:12681-12691. [PMID: 37822859 PMCID: PMC10563126 DOI: 10.1021/acscatal.3c02474] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2023] [Revised: 08/19/2023] [Indexed: 10/13/2023]
Abstract
The effect of Ce addition to the Cr-free Al-promoted Cu-Fe oxide-based catalysts is investigated. Catalyst characterization (X-ray diffraction (XRD), in situ Raman spectroscopy, high-sensitivity low-energy ion scattering (HS-LEIS), Brunauer-Emmett-Teller (BET) analysis), CO-temperature-programmed reduction chemical probing, and steady-state WGS activity reveal that (i) in the absence of Al, Ce addition via coprecipitation has a detrimental effect on the catalytic activity related to the poor thermostability and formation of less active Ce-Cu-O NPs, (ii) the addition of Ce via coprecipitation also does not improve the performance of the CuAlFe catalyst because of the formation of a thick CeOx overlayer on the active Cu-FeOx interface, and (iii) impregnation of Ce onto the CuAlFe catalyst exhibits significant improvement in catalytic performance due to the formation of a highly active CeOx-FeOx-Cu interfacial area. In summary, Al does not surface-segregate and serves as a structural promoter, while Ce and Cu surface-segregate and act as functional promoters in Ce/CuAlFe mixed oxide catalysts.
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Affiliation(s)
- Ozgen Yalcin
- College
of Engineering and Technology, American
University of the Middle East, Egaila 54200, Kuwait
| | - Sagar Sourav
- Operando
Molecular Spectroscopy & Catalysis Laboratory, Department of Chemical
and Biomolecular Engineering, Lehigh University, Bethlehem, Pennsylvania 18015, United States
| | - Israel E. Wachs
- Operando
Molecular Spectroscopy & Catalysis Laboratory, Department of Chemical
and Biomolecular Engineering, Lehigh University, Bethlehem, Pennsylvania 18015, United States
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3
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Feucht M, Sourav S, Kekunnaya R, Röder B. P-120 EEG biomarkers based on task-related and resting state oscillatory activity for classifying sight restored individuals. Clin Neurophysiol 2023. [DOI: 10.1016/j.clinph.2023.02.137] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/08/2023]
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4
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Sourav S, Kekunnaya R, Bottari D, Shareef I, Pitchaimuthu K, Röder B. P-114 Sound alters earliest visual cortical processing in sight-restored humans. Clin Neurophysiol 2023. [DOI: 10.1016/j.clinph.2023.02.131] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/08/2023]
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5
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Wang Y, Sourav S, Malizia JP, Thompson B, Wang B, Kunz MR, Nikolla E, Fushimi R. Deciphering the Mechanistic Role of Individual Oxide Phases and Their Combinations in Supported Mn–Na 2WO 4 Catalysts for Oxidative Coupling of Methane. ACS Catal 2022. [DOI: 10.1021/acscatal.2c03725] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Yixiao Wang
- Catalysis and Transient Kinetics Group, Idaho National Laboratory, Idaho Falls, Idaho 83415, United States
| | - Sagar Sourav
- Catalysis and Transient Kinetics Group, Idaho National Laboratory, Idaho Falls, Idaho 83415, United States
- Department of Chemical and Biomolecular Engineering, Lehigh University, Bethlehem, Pennsylvania 18015, United States
| | - Jason P. Malizia
- Catalysis and Transient Kinetics Group, Idaho National Laboratory, Idaho Falls, Idaho 83415, United States
- Department of Chemistry and Biochemistry, Montana State University, Bozeman, Montana 59717, United States
| | - Brooklyne Thompson
- Catalysis and Transient Kinetics Group, Idaho National Laboratory, Idaho Falls, Idaho 83415, United States
- Chemical, Biological, and Environmental Engineering, Oregon State University, Corvallis, Oregon 97331, United States
| | - Bingwen Wang
- Department of Chemical Engineering and Materials Science, Wayne State University, Detroit, Michigan 48202, United States
| | - M. Ross Kunz
- Catalysis and Transient Kinetics Group, Idaho National Laboratory, Idaho Falls, Idaho 83415, United States
| | - Eranda Nikolla
- Department of Chemical Engineering and Materials Science, Wayne State University, Detroit, Michigan 48202, United States
- Department of Chemical Engineering, University of Michigan, Ann Arbor, Michigan, 48109, United States
| | - Rebecca Fushimi
- Catalysis and Transient Kinetics Group, Idaho National Laboratory, Idaho Falls, Idaho 83415, United States
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6
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Sourav S, Kiani D, Wang Y, Baltrusaitis J, Fushimi RR, Wachs IE. Molecular structure and catalytic promotional effect of Mn on supported Na2WO4/SiO2 catalysts for oxidative coupling of methane (OCM) reaction. Catal Today 2022. [DOI: 10.1016/j.cattod.2022.07.005] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
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7
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Wang Y, Wang B, Sourav S, Batchu R, Fang Z, Kunz MR, Yablonsky G, Nikolla E, Fushimi R. Mechanistic pathways and role of oxygen in oxidative coupling of methane derived from transient kinetic studies. Catal Today 2022. [DOI: 10.1016/j.cattod.2022.05.004] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
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8
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Kiani D, Sourav S, Wachs IE, Baltrusaitis J. A combined computational and experimental study of methane activation during oxidative coupling of methane (OCM) by surface metal oxide catalysts. Chem Sci 2021; 12:14143-14158. [PMID: 34760199 PMCID: PMC8565385 DOI: 10.1039/d1sc02174e] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2021] [Accepted: 10/04/2021] [Indexed: 11/21/2022] Open
Abstract
The experimentally validated computational models developed herein, for the first time, show that Mn-promotion does not enhance the activity of the surface Na2WO4 catalytic active sites for CH4 heterolytic dissociation during OCM. Contrary to previous understanding, it is demonstrated that Mn-promotion poisons the surface WO4 catalytic active sites resulting in surface WO5 sites with retarded kinetics for C-H scission. On the other hand, dimeric Mn2O5 surface sites, identified and studied via ab initio molecular dynamics and thermodynamics, were found to be more efficient in activating CH4 than the poisoned surface WO5 sites or the original WO4 sites. However, the surface reaction intermediates formed from CH4 activation over the Mn2O5 surface sites are more stable than those formed over the Na2WO4 surface sites. The higher stability of the surface intermediates makes their desorption unfavorable, increasing the likelihood of over-oxidation to CO x , in agreement with the experimental findings in the literature on Mn-promoted catalysts. Consequently, the Mn-promoter does not appear to have an essential positive role in synergistically tuning the structure of the Na2WO4 surface sites towards CH4 activation but can yield MnO x surface sites that activate CH4 faster than Na2WO4 surface sites, but unselectively.
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Affiliation(s)
- Daniyal Kiani
- Department of Chemical and Biomolecular Engineering, Lehigh University B336 Iacocca Hall, 111 Research Drive Bethlehem PA 18015 USA
| | - Sagar Sourav
- Department of Chemical and Biomolecular Engineering, Lehigh University B336 Iacocca Hall, 111 Research Drive Bethlehem PA 18015 USA
| | - Israel E Wachs
- Department of Chemical and Biomolecular Engineering, Lehigh University B336 Iacocca Hall, 111 Research Drive Bethlehem PA 18015 USA
| | - Jonas Baltrusaitis
- Department of Chemical and Biomolecular Engineering, Lehigh University B336 Iacocca Hall, 111 Research Drive Bethlehem PA 18015 USA
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Sourav S, Wang Y, Kiani D, Baltrusaitis J, Fushimi RR, Wachs IE. New Mechanistic and Reaction Pathway Insights for Oxidative Coupling of Methane (OCM) over Supported Na
2
WO
4
/SiO
2
Catalysts. Angew Chem Int Ed Engl 2021. [DOI: 10.1002/ange.202108201] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Sagar Sourav
- Biological and Chemical Science and Engineering Energy Environment Science & Technology Idaho National Laboratory Idaho Falls ID 83415 USA
- Department of Chemical and Biomolecular Engineering Lehigh University Bethlehem PA 18015 USA
| | - Yixiao Wang
- Biological and Chemical Science and Engineering Energy Environment Science & Technology Idaho National Laboratory Idaho Falls ID 83415 USA
| | - Daniyal Kiani
- Department of Chemical and Biomolecular Engineering Lehigh University Bethlehem PA 18015 USA
| | - Jonas Baltrusaitis
- Department of Chemical and Biomolecular Engineering Lehigh University Bethlehem PA 18015 USA
| | - Rebecca R. Fushimi
- Biological and Chemical Science and Engineering Energy Environment Science & Technology Idaho National Laboratory Idaho Falls ID 83415 USA
| | - Israel E. Wachs
- Department of Chemical and Biomolecular Engineering Lehigh University Bethlehem PA 18015 USA
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10
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Sourav S, Wang Y, Kiani D, Baltrusaitis J, Fushimi RR, Wachs IE. New Mechanistic and Reaction Pathway Insights for Oxidative Coupling of Methane (OCM) over Supported Na 2 WO 4 /SiO 2 Catalysts. Angew Chem Int Ed Engl 2021; 60:21502-21511. [PMID: 34339591 DOI: 10.1002/anie.202108201] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2021] [Indexed: 12/14/2022]
Abstract
The complex structure of the catalytic active phase, and surface-gas reaction networks have hindered understanding of the oxidative coupling of methane (OCM) reaction mechanism by supported Na2 WO4 /SiO2 catalysts. The present study demonstrates, with the aid of in situ Raman spectroscopy and chemical probe (H2 -TPR, TAP and steady-state kinetics) experiments, that the long speculated crystalline Na2 WO4 active phase is unstable and melts under OCM reaction conditions, partially transforming to thermally stable surface Na-WOx sites. Kinetic analysis via temporal analysis of products (TAP) and steady-state OCM reaction studies demonstrate that (i) surface Na-WOx sites are responsible for selectively activating CH4 to C2 Hx and over-oxidizing CHy to CO and (ii) molten Na2 WO4 phase is mainly responsible for over-oxidation of CH4 to CO2 and also assists in oxidative dehydrogenation of C2 H6 to C2 H4 . These new insights reveal the nature of catalytic active sites and resolve the OCM reaction mechanism over supported Na2 WO4 /SiO2 catalysts.
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Affiliation(s)
- Sagar Sourav
- Biological and Chemical Science and Engineering, Energy Environment Science & Technology, Idaho National Laboratory, Idaho Falls, ID, 83415, USA.,Department of Chemical and Biomolecular Engineering, Lehigh University, Bethlehem, PA, 18015, USA
| | - Yixiao Wang
- Biological and Chemical Science and Engineering, Energy Environment Science & Technology, Idaho National Laboratory, Idaho Falls, ID, 83415, USA
| | - Daniyal Kiani
- Department of Chemical and Biomolecular Engineering, Lehigh University, Bethlehem, PA, 18015, USA
| | - Jonas Baltrusaitis
- Department of Chemical and Biomolecular Engineering, Lehigh University, Bethlehem, PA, 18015, USA
| | - Rebecca R Fushimi
- Biological and Chemical Science and Engineering, Energy Environment Science & Technology, Idaho National Laboratory, Idaho Falls, ID, 83415, USA
| | - Israel E Wachs
- Department of Chemical and Biomolecular Engineering, Lehigh University, Bethlehem, PA, 18015, USA
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11
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Sourav S, Wang Y, Kiani D, Baltrusaitis J, Fushimi RR, Wachs IE. Resolving the Types and Origin of Active Oxygen Species Present in Supported Mn-Na 2WO 4/SiO 2 Catalysts for Oxidative Coupling of Methane. ACS Catal 2021. [DOI: 10.1021/acscatal.1c02315] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Affiliation(s)
- Sagar Sourav
- Biological and Chemical Science and Engineering, Energy Environment Science & Technology, Idaho National Laboratory, Idaho Falls, Idaho 83415, United States
- Department of Chemical and Biomolecular Engineering, Lehigh University, Bethlehem, Pennsylvania 18015, United States
| | - Yixiao Wang
- Biological and Chemical Science and Engineering, Energy Environment Science & Technology, Idaho National Laboratory, Idaho Falls, Idaho 83415, United States
| | - Daniyal Kiani
- Department of Chemical and Biomolecular Engineering, Lehigh University, Bethlehem, Pennsylvania 18015, United States
| | - Jonas Baltrusaitis
- Department of Chemical and Biomolecular Engineering, Lehigh University, Bethlehem, Pennsylvania 18015, United States
| | - Rebecca R. Fushimi
- Biological and Chemical Science and Engineering, Energy Environment Science & Technology, Idaho National Laboratory, Idaho Falls, Idaho 83415, United States
| | - Israel E. Wachs
- Department of Chemical and Biomolecular Engineering, Lehigh University, Bethlehem, Pennsylvania 18015, United States
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12
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Kiani D, Sourav S, Baltrusaitis J, Wachs IE. Elucidating the Effects of Mn Promotion on SiO 2-Supported Na-Promoted Tungsten Oxide Catalysts for Oxidative Coupling of Methane (OCM). ACS Catal 2021. [DOI: 10.1021/acscatal.1c01392] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Affiliation(s)
- Daniyal Kiani
- Department of Chemical and Biomolecular Engineering, Lehigh University, B336 Iacocca Hall, 111 Research Drive, Bethlehem, Pennsylvania 18015, United States
| | - Sagar Sourav
- Department of Chemical and Biomolecular Engineering, Lehigh University, B336 Iacocca Hall, 111 Research Drive, Bethlehem, Pennsylvania 18015, United States
| | - Jonas Baltrusaitis
- Department of Chemical and Biomolecular Engineering, Lehigh University, B336 Iacocca Hall, 111 Research Drive, Bethlehem, Pennsylvania 18015, United States
| | - Israel E. Wachs
- Department of Chemical and Biomolecular Engineering, Lehigh University, B336 Iacocca Hall, 111 Research Drive, Bethlehem, Pennsylvania 18015, United States
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Abstract
This review focuses on recent fundamental insights about methane dehydroaromatization (MDA) to benzene over ZSM-5-supported transition metal oxide-based catalysts (MOx/ZSM-5, where M = V, Cr, Mo, W, Re, Fe). Benzene is an important organic intermediate, used for the synthesis of chemicals like ethylbenzene, cumene, cyclohexane, nitrobenzene and alkylbenzene. Current production of benzene is primarily from crude oil processing, but due to the abundant availability of natural gas, there is much recent interest in developing direct processes to convert CH4 to liquid chemicals. Among the various gas-to-liquid methods, the thermodynamically-limited Methane DehydroAromatization (MDA) to benzene under non-oxidative conditions appears very promising as it circumvents deep oxidation of CH4 to CO2 and does not require the use of a co-reactant. The findings from the MDA catalysis literature is critically analyzed with emphasis on in situ and operando spectroscopic characterization to understand the molecular level details regarding the catalytic sites before and during the MDA reaction. Specifically, this review discusses the anchoring sites of the supported MOx species on the ZSM-5 support, molecular structures of the initial dispersed surface MOx sites, nature of the active sites during MDA, reaction mechanisms, rate-determining step, kinetics and catalyst activity of the MDA reaction. Finally, suggestions are given regarding future experimental investigations to fill the information gaps currently found in the literature.
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Affiliation(s)
- Daniyal Kiani
- Department of Chemical and Biomolecular Engineering, Lehigh University, Bethlehem, PA 18015, USA.
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14
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Kiani D, Sourav S, Taifan W, Calatayud M, Tielens F, Wachs IE, Baltrusaitis J. Existence and Properties of Isolated Catalytic Sites on the Surface of β-Cristobalite-Supported, Doped Tungsten Oxide Catalysts (WOx/β-SiO2, Na-WOx/β-SiO2, Mn-WOx/β-SiO2) for Oxidative Coupling of Methane (OCM): A Combined Periodic DFT and Experimental Study. ACS Catal 2020. [DOI: 10.1021/acscatal.9b05591] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Daniyal Kiani
- Department of Chemical and Biomolecular Engineering, Lehigh University, B336 Iacocca
Hall, 111 Research Drive, Bethlehem, Pennsylvania 18015, United States
| | - Sagar Sourav
- Department of Chemical and Biomolecular Engineering, Lehigh University, B336 Iacocca
Hall, 111 Research Drive, Bethlehem, Pennsylvania 18015, United States
| | - William Taifan
- Department of Chemical and Biomolecular Engineering, Lehigh University, B336 Iacocca
Hall, 111 Research Drive, Bethlehem, Pennsylvania 18015, United States
| | - Monica Calatayud
- Sorbonne Université, CNRS, Laboratoire de Chimie Théorique, LCT, F-75005 Paris, France
| | - Frederik Tielens
- General Chemistry (ALGC)-Materials Modelling Group, Vrije Universiteit Brussel (Free University Brussels-VUB), Pleinlaan 2, 1050 Brussel, Belgium
| | - Israel E. Wachs
- Department of Chemical and Biomolecular Engineering, Lehigh University, B336 Iacocca
Hall, 111 Research Drive, Bethlehem, Pennsylvania 18015, United States
| | - Jonas Baltrusaitis
- Department of Chemical and Biomolecular Engineering, Lehigh University, B336 Iacocca
Hall, 111 Research Drive, Bethlehem, Pennsylvania 18015, United States
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15
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Kiani D, Sourav S, Wachs IE, Baltrusaitis J. Synthesis and molecular structure of model silica-supported tungsten oxide catalysts for oxidative coupling of methane (OCM). Catal Sci Technol 2020. [DOI: 10.1039/d0cy00289e] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Catalysts with only dispersed phase Na–WO4 sites where Na/W < 2 are slightly less active but significantly more C2 selective than the traditional Na2WO4/SiO2 catalysts that contain a crystalline phase where Na/W = 2.
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Affiliation(s)
- Daniyal Kiani
- Department of Chemical and Biomolecular Engineering
- Lehigh University
- Bethlehem
- USA
| | - Sagar Sourav
- Department of Chemical and Biomolecular Engineering
- Lehigh University
- Bethlehem
- USA
| | - Israel E. Wachs
- Department of Chemical and Biomolecular Engineering
- Lehigh University
- Bethlehem
- USA
| | - Jonas Baltrusaitis
- Department of Chemical and Biomolecular Engineering
- Lehigh University
- Bethlehem
- USA
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16
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Kiani D, Sourav S, Baltrusaitis J, Wachs IE. Oxidative Coupling of Methane (OCM) by SiO2-Supported Tungsten Oxide Catalysts Promoted with Mn and Na. ACS Catal 2019. [DOI: 10.1021/acscatal.9b01585] [Citation(s) in RCA: 94] [Impact Index Per Article: 18.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Daniyal Kiani
- Department of Chemical & Biomolecular Engineering, Lehigh University, Bethlehem, Pennsylvania 18015, United States
| | - Sagar Sourav
- Department of Chemical & Biomolecular Engineering, Lehigh University, Bethlehem, Pennsylvania 18015, United States
| | - Jonas Baltrusaitis
- Department of Chemical & Biomolecular Engineering, Lehigh University, Bethlehem, Pennsylvania 18015, United States
| | - Israel E. Wachs
- Department of Chemical & Biomolecular Engineering, Lehigh University, Bethlehem, Pennsylvania 18015, United States
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17
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Sourav S, Patricia A, Sharma S, Kanungo R, Jayachandran S, Prashanth K. Detection of pneumolysin and autolysin genes among antibiotic resistant Streptococcus pneumoniae in invasive infections. Indian J Med Microbiol 2010; 28:34-9. [PMID: 20061761 DOI: 10.4103/0255-0857.58726] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
PURPOSE To detect the presence of autolysin and pneumolysin genes among Streptococcus pneumoniae strains isolated from different disease entities among Indian patients. The study also attempted to determine antimicrobial susceptibility of the isolates. MATERIALS AND METHODS A total of 24 S. pneumoniae isolates were checked for the presence of lytA gene coding for autolysin and ply gene coding for pneumolysin using polymerase chain reaction (PCR). All the isolates were subjected to susceptibility testing by disc diffusion method for 10 different therapeutically relevant antibiotics. Minimum inhibition concentration (MIC) was determined using broth dilution method for ampicillin, penicillin and ciprofloxacin. RESULTS Eleven isolates from ocular infections and 13 isolates from different invasive diseases showed susceptibility to most of the antibiotics tested except chloramphenicol and ciprofloxacin. Fifty percentage of the isolates showed resistance to chloramphenicol and ciprofloxacin. A moderate level of resistance of 18% was noted for cefepime and ceftriaxone. Only 6% of resistance was observed for amoxicillin and ceftazidime. MIC levels ranged from 0.015 to 1 microg/mL for ampicillin and only one isolate had an MIC of 1 microg/mL. The MIC levels for penicillin ranged from 0.062 to 4 microg/mL, wherein nine isolates showed high levels of MICs ranging from 2 to 4 microg/mL. Six isolates had a very high resistance levels for ciprofloxacin with MIC ranging from 32-128 microg/mL. The presence of lytA was observed in 23 out of 24 isolates tested whereas only 17 isolates were positive for pneumolysin. Four ocular isolates and one isolate from ear infection were negative for pneumolysin. CONCLUSION Emerging resistance observed for cefepime and ceftriaxone might be due their increased and frequent usage nowadays. Presence of pneumolysin appears to be more critical for pathogenesis of invasive infections than the ocular infections. However, presence of lytA gene in all the isolates signifies that irrespective of site of isolation, kind of infection caused, autolysin is an obligate necessity for this organism.
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Affiliation(s)
- S Sourav
- Department of Biotechnology, School of Life Sciences, Pondicherry University, R. Venkataraman Nagar, Kalapet, India
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Sourav S, Manchanda R. EFFECTS OF VARIATION IN INTERCELLULAR ELECTRICAL COUPLING ON SYNAPTIC POTENTIALS IN SMOOTH MUSCLE: A COMPUTATIONAL STUDY. ACTA ACUST UNITED AC 2001. [DOI: 10.1081/jbc-100104143] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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19
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Abstract
The effect of the size of syncytial bundles of cells on the passive synaptic potentials generated within them has been explored. Computer simulations have been performed of neuronally produced spontaneous excitatory junction potentials (SEJPs) generated in cubical 'bidomain' model of syncytial tissue. It is found that indical properties of SEJPs vary conspicuously in syncytium sizes smaller than about 15-17-cube, but change very little in syncytium sizes greater than this. At the centroid of the cube, the peak amplitude Vp of the SEJP declines from 14.32 mV to 11.70 mV as syncytium size increases from 7-cube to 15-cube, i.e. a decrease of approximately 18%, while between system sizes 15-cube (Vp = 11.70 mV) and 29-cube (Vp = 11.67 mV), the reduction is only approximately 0.3%. Similar trends are observed for the time to peak of SEJPs. These observations indicate a minimum bundle size in smooth muscle below which syncytial function is modified; the implications of this are discussed.
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Affiliation(s)
- S Sourav
- Interdisciplinary Programme in Biomedical Engineering, Indian Institute of Technology-Bombay, Powai, India
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