usman rana - Academia.edu (original) (raw)
Papers by usman rana
Chemistry Central journal, 2014
Theoretical Chemistry Accounts, 2014
ABSTRACT This study is carried out to design diarylamine-fluorene dyes by incorporating electron‐... more ABSTRACT This study is carried out to design diarylamine-fluorene dyes by incorporating electron‐deficient thiadiazole derivatives. Quantum chemical calculations are performed to study the geometries, electronic structures and absorption spectra of the dyes. Interaction of dyes with TiO2 cluster is also studied. The effects of the electron‐deficient units on the spectra and electrochemical properties have been investigated. Dyes D1–D4 display remarkably enhanced spectral response in the red portion of the solar spectrum as compared with reference compound D0. The newly designed dyes demonstrate desirable energetic and spectroscopic parameters and may lead to efficient metal‐free organic dye sensitizers for DSSCs.
Journal of Computational Electronics, 2014
ABSTRACT Since, the organic dyes that harness sunlight are generally considered as the heart of t... more ABSTRACT Since, the organic dyes that harness sunlight are generally considered as the heart of the dye sensitized solar cells (DSSC), the present study was carried out with the aim to design heterocyclic azo dyes that can be potentially used in DSSC application. Hereby, the analysis based on density functional theory (DFT) and time-dependent DFT calculations of the geometries, electronic structures and absorption spectra of the dyes before and after binding to titanium oxide (TiO2) were carried out and investigated in detail. The data obtained from these analyses were then used to determine the open-circuit photovoltage (VOC), and to measure the important parameters such as the light harvesting efficiency (LHE) and the electron injection efficiency associatedwith the short-circuit photocurrent density (JSC). Our investigation reveals that all dyes showed absorbance in the visible region (469–521 nm) with high oscillator strength ( f ) (1.076–1.564) and LHE (0.9176–0.973). Moreover, we found that the dyes after binding to titanium oxide displayed slightly red-shifted absorption (475–527 nm) with improved oscillator strength ( f ) (1.121–1.664) and LHE (0.921–0.979). In addition, all dyes showed high VOC (1.068–2.232 eV) and high driving force for the electron injection, thus leading to the larger JSC. Our findings indicate that the heterocyclic azo dyes investigated in the current study can display better light to power conversion efficiency if used in the DSSC system, where the origin or their better performance can be attributed to the high JSC and VOC values found for these potential dyes. Based on the detailed study and investigation, we believe that the theoretical criteria used in the present study can be employed as an initial screening tool not merely to assess the properties of other organic dyes, but also to potentially design the organic azo dyes for their potential application in the DSSC systems.
Arabian Journal of Chemistry, 2014
ABSTRACT One of the greatest challenges for the modern world is the ever-increasing demand of ene... more ABSTRACT One of the greatest challenges for the modern world is the ever-increasing demand of energy, which may soon outstrip the amount of natural resources that can be obtained using currently known energy conversion and energy storage technologies such as solar cells, fuel cells, lithium ion batteries, and supercapacitors. It appears that the maximum output efficiencies of these devices have already reached the intrinsic limits of almost all electrocatalyst materials. Hence, it is a high time to think about new material architectures by controlling size, shape, and geometry, as well as composition that can potentially make a significant improvement in the performance of these electrochemical devices. Among several known electrocatalyst materials are nanomaterials and their composites due to their unique electrical, mechanical, physical, chemical, and structural characteristics. These materials have opened a whole new territory of possibilities in designing high performance energy storage and conversion devices. In this chapter, the authors review the recent progress in energy storage and conversion devices that utilize various nanomaterials and their composite materials and identify future directions in which the field is likely to develop.
AAPS PharmSciTech, 2014
Leaching of the internal apolar phase from the biopolymeric microparticles during storage is a gr... more Leaching of the internal apolar phase from the biopolymeric microparticles during storage is a great concern as it undoes the beneficial effects of encapsulation. In this paper, a novel formulation was prepared by encapsulating the sunflower oil-based organogels in alginate microparticles. Salicylic acid and metronidazole were used as the model drugs. The microparticles were prepared by double emulsion methodology. Physico-chemical characterization of the microparticles was done by microscopy, FTIR, XRD, and DSC studies. Oil leaching studies, biocompatibility, mucoadhesivity, in vitro drug release, and the antimicrobial efficiency of the microparticles were also performed. The microparticles were found to be spherical in shape. Gelation of the sunflower oil prevented leaching of the internal phase from the microparticles. Release of drugs from the microparticles followed Fickian kinetics and non-Fickian kinetics in gastric and intestinal environments, respectively. Microparticles showed good antimicrobial activity against both Gram-positive (Bacillus subtilis) and Gram-negative (Escherichia coli) bacteria. The results suggested that the developed formulations hold promise to carry oils without leakage of the internal phase. Encapsulation of organogels within the microparticles has improved the drug entrapment efficiency and improved characteristics for controlled delivery applications.
Asian Pacific Journal of Tropical Disease, 2015
ABSTRACT To evaluate the antimicrobial potential of fraction of the fungus Fusarium sp. and study... more ABSTRACT To evaluate the antimicrobial potential of fraction of the fungus Fusarium sp. and study the tentative identification of their active constituents.
Journal of Asian Natural Products Research, 2014
Phytochemical investigation of the endophytic fungus Coniothyrium sp. resulted in the isolation o... more Phytochemical investigation of the endophytic fungus Coniothyrium sp. resulted in the isolation of a new phenoxyphenyl ether, named coniothyren (1), and two known compounds, coniol (2) and (+)-epoxydon (3). The structure of the new compound was elucidated by detailed spectroscopic analysis, namely, (1)H NMR, (13)C NMR, COSY, HMQC, HMBC, and HR-EI-MS. Preliminary studies demonstrated that (+)-epoxydon (3) displayed good antibacterial and antialgal activities toward Bacillus megaterium and Chlorella fusca, respectively.
Electroanalysis, 2014
ABSTRACT The electrochemical behavior of a biologically important heterocyclic compound, 1,3-diox... more ABSTRACT The electrochemical behavior of a biologically important heterocyclic compound, 1,3-dioxolo[4,5-g]pyrido[2,3-b]quinoxaline was investigated by cyclic, square wave and differential pulse voltammetry in solutions of different pH. Kinetic and thermodynamic parameters like standard rate constant, diffusion coefficient, apparent energy of activation, standard Gibbs free energy and enthalpy and entropy changes were evaluated. Limits of detection and quantification were determined by square wave voltammetry. The redox mechanism of the compound was proposed on the basis of experimental results. Computational chemistry was used as a tool for the verification of experimental outcomes and assessment of different theoretical parameters
Electrochimica Acta, 2014
Journal of King Saud University - Science, 2015
Journal of Saudi Chemical Society, 2014
ABSTRACT The present study reports a convenient approach for the synthesis of thiophene sulfonami... more ABSTRACT The present study reports a convenient approach for the synthesis of thiophene sulfonamide derivatives (3a–3k) via Suzuki cross coupling reaction. This method of synthesis involved the reactions of various aryl boronic acids and esters with 5-bromthiophene-2-sulfonamide (2) under mild and suitable temperature conditions. The compounds synthesized in the present study were subjected to urease inhibition and hemolytic activities. The substitution pattern and the electronic effects of different functional groups (i.e., Cl, CH3, OCH3, F etc.) available on the aromatic ring are found to have significant effect on the overall results. The compound 5-Phenylthiophene-2-sulfonamide 3a showed the highest urease inhibition activity with IC50 value ∼ 30.8 μg/mL compared with the thiourea (used as standard) having IC50 value ∼ 43 μg/mL. Moreover, almost all of the compounds were examined for the hemolytic activity against triton X-100 with positive results obtained in most of the cases. In addition, the antibacterial activities of the derivatives of 5-arylthiophene-2-sulfonamide and 5-bromothiophene-2-acetamide were also investigated during the course of the study.
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2015
A new Schiff base, 1-((4-bromophenylimino) methyl) naphthalen-2-ol (BPIMN) was successfully synth... more A new Schiff base, 1-((4-bromophenylimino) methyl) naphthalen-2-ol (BPIMN) was successfully synthesized and characterized by (1)H NMR, (13)C NMR, FTIR and UV-Vis spectroscopy. The results were compared with a structurally related Schiff base, 1-((4-chlorophenylimino) methyl) naphthalen-2-ol (CPIMN). The photometric and electrochemical fate of BPIMN and CPIMN was investigated in a wide pH range. The experimental findings were supported by quantum mechanical approach. The redox mechanistic pathways were proposed on the basis of results obtained electrochemical techniques. Moreover, pH dependent UV-Vis spectroscopy of BPIMN and CPIMN was carried out and the appearance of isosbestic points indicated the existence of these compounds in different tautomeric forms.
PLoS ONE, 2014
A highly convenient method has been developed for the synthesis of (prop-2-ynyloxy) benzene and i... more A highly convenient method has been developed for the synthesis of (prop-2-ynyloxy) benzene and its derivatives. Differently substituted phenol and aniline derivatives were allowed to react with propargyl bromide in the presence of K2CO3 base and acetone as solvent. The compounds were synthesized in good yields (53-85%). Low cost, high yields and easy availability of compounds helped in the synthesis. Electron withdrawing groups favor the formation of stable phenoxide ion thus in turn favors the formation of product while electron donating groups do not favor the reaction. Phenol derivatives gave good yields as compared to that of aniline. As aprotic polar solvents favor SN2 type reactions so acetone provided best solvation for the reactions. K2CO3 was proved to be good for the synthesis. Antibacterial, Antiurease and NO scavenging activity of synthesized compounds were also examined. 4-bromo-2-chloro-1-(prop-2-ynyloxy)benzene 2a was found most active compound against urease enzyme with a percentage inhibition of 82.00±0.09 at 100 µg/mL with IC50 value of 60.2. 2-bromo-4-methyl-1-(prop-2-ynyloxy)benzene 2d was found potent antibacterial against Bacillus subtillus showing excellent inhibitory action with percentage inhibition of 55.67±0.26 at 100 µg/ml wih IC50 value of 79.9. Based on results, it can be concluded that some of the synthesized compounds may have potential antiurease and antibacterial effects against several harmful substances.
TheScientificWorldJournal, 2014
Journal of Photochemistry and Photobiology B: Biology, 2014
Journal of Food and Nutrition Research, 2014
Chemistry Central journal, 2014
Theoretical Chemistry Accounts, 2014
ABSTRACT This study is carried out to design diarylamine-fluorene dyes by incorporating electron‐... more ABSTRACT This study is carried out to design diarylamine-fluorene dyes by incorporating electron‐deficient thiadiazole derivatives. Quantum chemical calculations are performed to study the geometries, electronic structures and absorption spectra of the dyes. Interaction of dyes with TiO2 cluster is also studied. The effects of the electron‐deficient units on the spectra and electrochemical properties have been investigated. Dyes D1–D4 display remarkably enhanced spectral response in the red portion of the solar spectrum as compared with reference compound D0. The newly designed dyes demonstrate desirable energetic and spectroscopic parameters and may lead to efficient metal‐free organic dye sensitizers for DSSCs.
Journal of Computational Electronics, 2014
ABSTRACT Since, the organic dyes that harness sunlight are generally considered as the heart of t... more ABSTRACT Since, the organic dyes that harness sunlight are generally considered as the heart of the dye sensitized solar cells (DSSC), the present study was carried out with the aim to design heterocyclic azo dyes that can be potentially used in DSSC application. Hereby, the analysis based on density functional theory (DFT) and time-dependent DFT calculations of the geometries, electronic structures and absorption spectra of the dyes before and after binding to titanium oxide (TiO2) were carried out and investigated in detail. The data obtained from these analyses were then used to determine the open-circuit photovoltage (VOC), and to measure the important parameters such as the light harvesting efficiency (LHE) and the electron injection efficiency associatedwith the short-circuit photocurrent density (JSC). Our investigation reveals that all dyes showed absorbance in the visible region (469–521 nm) with high oscillator strength ( f ) (1.076–1.564) and LHE (0.9176–0.973). Moreover, we found that the dyes after binding to titanium oxide displayed slightly red-shifted absorption (475–527 nm) with improved oscillator strength ( f ) (1.121–1.664) and LHE (0.921–0.979). In addition, all dyes showed high VOC (1.068–2.232 eV) and high driving force for the electron injection, thus leading to the larger JSC. Our findings indicate that the heterocyclic azo dyes investigated in the current study can display better light to power conversion efficiency if used in the DSSC system, where the origin or their better performance can be attributed to the high JSC and VOC values found for these potential dyes. Based on the detailed study and investigation, we believe that the theoretical criteria used in the present study can be employed as an initial screening tool not merely to assess the properties of other organic dyes, but also to potentially design the organic azo dyes for their potential application in the DSSC systems.
Arabian Journal of Chemistry, 2014
ABSTRACT One of the greatest challenges for the modern world is the ever-increasing demand of ene... more ABSTRACT One of the greatest challenges for the modern world is the ever-increasing demand of energy, which may soon outstrip the amount of natural resources that can be obtained using currently known energy conversion and energy storage technologies such as solar cells, fuel cells, lithium ion batteries, and supercapacitors. It appears that the maximum output efficiencies of these devices have already reached the intrinsic limits of almost all electrocatalyst materials. Hence, it is a high time to think about new material architectures by controlling size, shape, and geometry, as well as composition that can potentially make a significant improvement in the performance of these electrochemical devices. Among several known electrocatalyst materials are nanomaterials and their composites due to their unique electrical, mechanical, physical, chemical, and structural characteristics. These materials have opened a whole new territory of possibilities in designing high performance energy storage and conversion devices. In this chapter, the authors review the recent progress in energy storage and conversion devices that utilize various nanomaterials and their composite materials and identify future directions in which the field is likely to develop.
AAPS PharmSciTech, 2014
Leaching of the internal apolar phase from the biopolymeric microparticles during storage is a gr... more Leaching of the internal apolar phase from the biopolymeric microparticles during storage is a great concern as it undoes the beneficial effects of encapsulation. In this paper, a novel formulation was prepared by encapsulating the sunflower oil-based organogels in alginate microparticles. Salicylic acid and metronidazole were used as the model drugs. The microparticles were prepared by double emulsion methodology. Physico-chemical characterization of the microparticles was done by microscopy, FTIR, XRD, and DSC studies. Oil leaching studies, biocompatibility, mucoadhesivity, in vitro drug release, and the antimicrobial efficiency of the microparticles were also performed. The microparticles were found to be spherical in shape. Gelation of the sunflower oil prevented leaching of the internal phase from the microparticles. Release of drugs from the microparticles followed Fickian kinetics and non-Fickian kinetics in gastric and intestinal environments, respectively. Microparticles showed good antimicrobial activity against both Gram-positive (Bacillus subtilis) and Gram-negative (Escherichia coli) bacteria. The results suggested that the developed formulations hold promise to carry oils without leakage of the internal phase. Encapsulation of organogels within the microparticles has improved the drug entrapment efficiency and improved characteristics for controlled delivery applications.
Asian Pacific Journal of Tropical Disease, 2015
ABSTRACT To evaluate the antimicrobial potential of fraction of the fungus Fusarium sp. and study... more ABSTRACT To evaluate the antimicrobial potential of fraction of the fungus Fusarium sp. and study the tentative identification of their active constituents.
Journal of Asian Natural Products Research, 2014
Phytochemical investigation of the endophytic fungus Coniothyrium sp. resulted in the isolation o... more Phytochemical investigation of the endophytic fungus Coniothyrium sp. resulted in the isolation of a new phenoxyphenyl ether, named coniothyren (1), and two known compounds, coniol (2) and (+)-epoxydon (3). The structure of the new compound was elucidated by detailed spectroscopic analysis, namely, (1)H NMR, (13)C NMR, COSY, HMQC, HMBC, and HR-EI-MS. Preliminary studies demonstrated that (+)-epoxydon (3) displayed good antibacterial and antialgal activities toward Bacillus megaterium and Chlorella fusca, respectively.
Electroanalysis, 2014
ABSTRACT The electrochemical behavior of a biologically important heterocyclic compound, 1,3-diox... more ABSTRACT The electrochemical behavior of a biologically important heterocyclic compound, 1,3-dioxolo[4,5-g]pyrido[2,3-b]quinoxaline was investigated by cyclic, square wave and differential pulse voltammetry in solutions of different pH. Kinetic and thermodynamic parameters like standard rate constant, diffusion coefficient, apparent energy of activation, standard Gibbs free energy and enthalpy and entropy changes were evaluated. Limits of detection and quantification were determined by square wave voltammetry. The redox mechanism of the compound was proposed on the basis of experimental results. Computational chemistry was used as a tool for the verification of experimental outcomes and assessment of different theoretical parameters
Electrochimica Acta, 2014
Journal of King Saud University - Science, 2015
Journal of Saudi Chemical Society, 2014
ABSTRACT The present study reports a convenient approach for the synthesis of thiophene sulfonami... more ABSTRACT The present study reports a convenient approach for the synthesis of thiophene sulfonamide derivatives (3a–3k) via Suzuki cross coupling reaction. This method of synthesis involved the reactions of various aryl boronic acids and esters with 5-bromthiophene-2-sulfonamide (2) under mild and suitable temperature conditions. The compounds synthesized in the present study were subjected to urease inhibition and hemolytic activities. The substitution pattern and the electronic effects of different functional groups (i.e., Cl, CH3, OCH3, F etc.) available on the aromatic ring are found to have significant effect on the overall results. The compound 5-Phenylthiophene-2-sulfonamide 3a showed the highest urease inhibition activity with IC50 value ∼ 30.8 μg/mL compared with the thiourea (used as standard) having IC50 value ∼ 43 μg/mL. Moreover, almost all of the compounds were examined for the hemolytic activity against triton X-100 with positive results obtained in most of the cases. In addition, the antibacterial activities of the derivatives of 5-arylthiophene-2-sulfonamide and 5-bromothiophene-2-acetamide were also investigated during the course of the study.
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2015
A new Schiff base, 1-((4-bromophenylimino) methyl) naphthalen-2-ol (BPIMN) was successfully synth... more A new Schiff base, 1-((4-bromophenylimino) methyl) naphthalen-2-ol (BPIMN) was successfully synthesized and characterized by (1)H NMR, (13)C NMR, FTIR and UV-Vis spectroscopy. The results were compared with a structurally related Schiff base, 1-((4-chlorophenylimino) methyl) naphthalen-2-ol (CPIMN). The photometric and electrochemical fate of BPIMN and CPIMN was investigated in a wide pH range. The experimental findings were supported by quantum mechanical approach. The redox mechanistic pathways were proposed on the basis of results obtained electrochemical techniques. Moreover, pH dependent UV-Vis spectroscopy of BPIMN and CPIMN was carried out and the appearance of isosbestic points indicated the existence of these compounds in different tautomeric forms.
PLoS ONE, 2014
A highly convenient method has been developed for the synthesis of (prop-2-ynyloxy) benzene and i... more A highly convenient method has been developed for the synthesis of (prop-2-ynyloxy) benzene and its derivatives. Differently substituted phenol and aniline derivatives were allowed to react with propargyl bromide in the presence of K2CO3 base and acetone as solvent. The compounds were synthesized in good yields (53-85%). Low cost, high yields and easy availability of compounds helped in the synthesis. Electron withdrawing groups favor the formation of stable phenoxide ion thus in turn favors the formation of product while electron donating groups do not favor the reaction. Phenol derivatives gave good yields as compared to that of aniline. As aprotic polar solvents favor SN2 type reactions so acetone provided best solvation for the reactions. K2CO3 was proved to be good for the synthesis. Antibacterial, Antiurease and NO scavenging activity of synthesized compounds were also examined. 4-bromo-2-chloro-1-(prop-2-ynyloxy)benzene 2a was found most active compound against urease enzyme with a percentage inhibition of 82.00±0.09 at 100 µg/mL with IC50 value of 60.2. 2-bromo-4-methyl-1-(prop-2-ynyloxy)benzene 2d was found potent antibacterial against Bacillus subtillus showing excellent inhibitory action with percentage inhibition of 55.67±0.26 at 100 µg/ml wih IC50 value of 79.9. Based on results, it can be concluded that some of the synthesized compounds may have potential antiurease and antibacterial effects against several harmful substances.
TheScientificWorldJournal, 2014
Journal of Photochemistry and Photobiology B: Biology, 2014
Journal of Food and Nutrition Research, 2014