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  1. AU="Nadeem S. Sheikh"
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  1. Article ; Online: An Integrated Experimental and Theoretical Studies on the Corrosion Inhibition of Carbon Steel by Harmal Extracts

    Hassan H. Hammud / Sarah A. Maache / Nasreen Al Otaibi / Nadeem S. Sheikh

    Molecules, Vol 27, Iss 7250, p

    2022  Volume 7250

    Abstract: The corrosion inhibition effect of the three extracts from Harmal roots (HRE), leaves (HLE), and flowers (HFE) were studied for carbon steel corrosion inhibition in 0.25 M H 2 SO 4 solution. The electrochemical impedance study indicated that the three ... ...

    Abstract The corrosion inhibition effect of the three extracts from Harmal roots (HRE), leaves (HLE), and flowers (HFE) were studied for carbon steel corrosion inhibition in 0.25 M H 2 SO 4 solution. The electrochemical impedance study indicated that the three types of extracts decreased corrosion effectively through a charge transfer mechanism. Harmal roots and leaf extracts showed inhibition values of 94.1% and 94.2%, while it was 88.7% for Harmal flower extract at the inhibitor concentration of 82.6 ppm. Potentiodynamic polarization data revealed that Harmal extracts acted through predominant cathodic type inhibition. Both the corrosion current density and corrosion rate decreased significantly in the presence of Harmal extracts compared to blank solution. The corrosion rate (mpy) value was 63.3, 86.1, and 180.7 for HRE, HLE, and HFE, respectively. The adsorption-free energy change Δ G ads (kJ·mol −1 ) values calculated from the Langmuir adsorption isotherm plots were for HRE (−35.08), HLE (−33.17), and HFE (−33.12). Thus, corrosion inhibition occurred due to the adsorption of Harmal extract on the carbon steel surface via the chemisorption mechanism. Moreover, a computational investigation using B3LYP/6-311G++(d,p) basis set in both gaseous and aqueous phases was performed for the major alkaloids (1–8) present in the Harmal extract.
    Keywords harmal extract ; electrochemical studies ; anti-corrosion ; DFT calculations ; Organic chemistry ; QD241-441
    Subject code 669
    Language English
    Publishing date 2022-10-01T00:00:00Z
    Publisher MDPI AG
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  2. Article ; Online: Removal of Malachite Green Using Hydrochar from PALM Leaves

    Hassan H. Hammud / Mohamad H. Hammoud / Aqeel A. Hussein / Youssef B. Fawaz / Malai Haniti Sheikh Abdul Hamid / Nadeem S. Sheikh

    Sustainability, Vol 15, Iss 8939, p

    2023  Volume 8939

    Abstract: Biochar was prepared by the hydrothermal carbonization (HTC) of palm leaves, characterized, and utilized as an adsorbent for Malachite Green dye (MG). The Higher Heating Value (HHV) of biochar depends on the carbonization temperature and has a maximum ... ...

    Abstract Biochar was prepared by the hydrothermal carbonization (HTC) of palm leaves, characterized, and utilized as an adsorbent for Malachite Green dye (MG). The Higher Heating Value (HHV) of biochar depends on the carbonization temperature and has a maximum value of 24.81 MJ/kg. Activation using H 2 O 2 oxidation of HTC biochar prepared at 208 °C produced AHTC with improved capacity. The optimum pH was found to be in the range 7–8. Freundlich, Langmuir, Temkin, and Dubinin–Radushkevich adsorption isotherms were used to study MG adsorption data. The Langmuir isotherm provided the best fit for experimental data. Experiments conducted using activated biochar AHTC at 25 °C resulted in an adsorption capacity of 62.80 mg/g, far greater than what was observed for HTC biochar (45.59 mg/g). The maximum adsorption capacity was 88% when the concentration of MG solution was 66 ppm. The free energy change in adsorption DG° indicated that the adsorption process was spontaneous. Adsorption followed pseudo-second-order kinetics. Fixed-column adsorptions models, namely, Thomas, Yan et al. and Yoon–Nelson models, were investigated for AHTC. The column adsorption capacity determined by the Thomas model was 33.57 mg/g. In addition, a computational investigation has been carried out to determine the structural and electronic features, as well as the quantum chemical parameters of HTC and MG. Moreover, the interaction between the HTC and MG is investigated, which is further elaborated by performing non-covalent interaction (NCI) through the reduced density gradient (RDG) analysis. Thus, the easily prepared hydrochar from abundant waste palm leaves can be used as a high-value biocoal and efficient adsorbent of the cationic dye malachite green.
    Keywords biochar ; hydrothermal ; higher heating value ; adsorption ; activation ; kinetics ; Environmental effects of industries and plants ; TD194-195 ; Renewable energy sources ; TJ807-830 ; Environmental sciences ; GE1-350
    Subject code 660
    Language English
    Publishing date 2023-06-01T00:00:00Z
    Publisher MDPI AG
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  3. Article ; Online: Theoretical Study of Dodecafluorophenylene-Based Superalkalides with Significantly High NLO Response

    Areeg Sajjad / Sehrish Sarfaraz / Annum Ahsan / Imene Bayach / Malai Haniti S. A. Hamid / Nadeem S. Sheikh / Khurshid Ayub

    ACS Omega, Vol 8, Iss 48, Pp 45589-

    2023  Volume 45598

    Keywords Chemistry ; QD1-999
    Language English
    Publishing date 2023-11-01T00:00:00Z
    Publisher American Chemical Society
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  4. Article ; Online: Dynamic Phenomena and Complexation Effects in the α-Lithiation and Asymmetric Functionalization of Azetidines

    Pantaleo Musci / Marco Colella / Angela Altomare / Giuseppe Romanazzi / Nadeem S. Sheikh / Leonardo Degennaro / Renzo Luisi

    Molecules, Vol 27, Iss 2847, p

    2022  Volume 2847

    Abstract: In this work it is demonstrated that enantiomerically enriched N -alkyl 2-oxazolinylazetidines undergo exclusive α-lithiation, and that the resulting lithiated intermediate is chemically stable but configurationally labile under the given experimental ... ...

    Abstract In this work it is demonstrated that enantiomerically enriched N -alkyl 2-oxazolinylazetidines undergo exclusive α-lithiation, and that the resulting lithiated intermediate is chemically stable but configurationally labile under the given experimental conditions that afford enantioenriched N -alkyl-2,2-disubstituted azetidines. Although this study reveals the configurational instability of the diastereomeric lithiated azetidines, it points out an interesting stereoconvergence of such lithiated intermediates towards the thermodynamically stable species, making the overall process highly stereoselective (er > 95:5, dr > 85:15) after trapping with electrophiles. This peculiar behavior has been rationalized by considering the dynamics at the azetidine nitrogen atom, the inversion at the C-Li center supported by in situ FT-IR experiments, and DFT calculations that suggested the presence of η 3 -coordinated species for diastereomeric lithiated azetidines. The described situation contrasted with the demonstrated stability of the smaller lithiated aziridine analogue. The capability of oxazolinylazetidines to undergo different reaction patterns with organolithium bases supports the model termed “dynamic control of reactivity” of relevance in organolithium chemistry. It has been demonstrated that only 2,2-substituted oxazolinylazetidines with suitable stereochemical requirements could undergo C=N addition of organolithiums in non-coordinating solvents, leading to useful precursors of chiral (er > 95:5) ketoazetidines.
    Keywords azetidines ; organolithiums ; nitrogen dynamics ; heterocyclic chemistry ; computational chemistry ; Organic chemistry ; QD241-441
    Subject code 540
    Language English
    Publishing date 2022-04-01T00:00:00Z
    Publisher MDPI AG
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  5. Article ; Online: Remarkable Single Atom Catalyst of Transition Metal (Fe, Co & Ni) Doped on C 2 N Surface for Hydrogen Dissociation Reaction

    Ahmed Bilal Shah / Sehrish Sarfaraz / Muhammad Yar / Nadeem S. Sheikh / Hassan H. Hammud / Khurshid Ayub

    Nanomaterials, Vol 13, Iss 1, p

    2022  Volume 29

    Abstract: Currently, hydrogen is recognized as the best alternative for fossil fuels because of its sustainable nature and environmentally friendly processing. In this study, hydrogen dissociation reaction is studied theoretically on the transition metal doped ... ...

    Abstract Currently, hydrogen is recognized as the best alternative for fossil fuels because of its sustainable nature and environmentally friendly processing. In this study, hydrogen dissociation reaction is studied theoretically on the transition metal doped carbon nitride (C 2 N) surface through single atom catalysis. Each TMs@C 2 N complex is evaluated to obtain the most stable spin state for catalytic reaction. In addition, electronic properties (natural bond orbital NBO & frontier molecular orbital FMO) of the most stable spin state complex are further explored. During dissociation, hydrogen is primarily adsorbed on metal doped C 2 N surface and then dissociated heterolytically between metal and nitrogen atom of C 2 N surface. Results revealed that theFe@C 2 N surface is the most suitable catalyst for H 2 dissociation reaction with activation barrier of 0.36 eV compared with Ni@C 2 N (0.40 eV) and Co@C 2 N (0.45 eV) complexes. The activation barrier for H 2 dissociation reaction is quite low in case of Fe@C 2 N surface, which is comparatively better than already reported noble metal catalysts.
    Keywords hydrogen dissociation reaction ; hydrogen energy ; C 2 N surface ; single atom catalyst ; catalysis ; transition metals ; Chemistry ; QD1-999
    Subject code 540
    Language English
    Publishing date 2022-12-01T00:00:00Z
    Publisher MDPI AG
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  6. Article ; Online: Enhanced nonlinear optical response of alkalides based on stacked Janus all-cis-1,2,3,4,5,6-hexafluorocyclohexane

    Muhammad Sohaib / Hasnain Sajid / Sehrish Sarfaraz / Malai Haniti Sheikh Abdul Hamid / Mazhar Amjad Gilani / Muhammad Ans / Tariq Mahmood / Shabbir Muhammad / Mohammed A. Alkhalifah / Nadeem S. Sheikh / Khurshid Ayub

    Heliyon, Vol 9, Iss 9, Pp e19325- (2023)

    2023  

    Abstract: Significant efforts are continuously exerted by the scientific community to explore new strategies to design materials with high nonlinear optical responses. An effective approach is to design alkalides based on Janus molecules. Herein, we present a new ... ...

    Abstract Significant efforts are continuously exerted by the scientific community to explore new strategies to design materials with high nonlinear optical responses. An effective approach is to design alkalides based on Janus molecules. Herein, we present a new approach to remarkably boost the NLO response of alkalides by stacking the Janus molecules. Alkalides based on stacked Janus molecule, M-n-M' (where n = 2 & 3 while M and M′ are Li/Na/K) are studied for structural, energetic, electrical, and nonlinear optical properties. The thermodynamic stability of the designed complexes is confirmed by the energetic stabilities, which range between -14.07 and -28.77 kcal/mol. The alkalide character of alkali metals-doped complexes is confirmed by the NBO charge transfer and HOMO(s) densities. The HOMO densities are located on the doped alkali metal atoms, indicating their alkalide character. The absorptions in UV–Vis and near IR region confirm the deep ultraviolet transparency of the designed complexes. The maximum first static and dynamic hyperpolarizabilities of 5.13 × 107 and 6.6 × 106 au (at 1339 nm) confirm their high NLO response, especially for K-2-M′ complexes. The NLO response of alkalides based on stacked Janus molecules is 1–2 orders of magnitude higher than the alkalide based on Janus monomer. The high values of dc-Kerr and electric field-induced response e.g., max ∼107 and 108 au, respectively have been obtained. These findings suggest that our designed complexes envision a new insight into the rational design of stable high NLO performance materials.
    Keywords Stacking ; Janus molecule ; NLO response ; Density functional theory ; Alkalides ; Science (General) ; Q1-390 ; Social sciences (General) ; H1-99
    Subject code 535
    Language English
    Publishing date 2023-09-01T00:00:00Z
    Publisher Elsevier
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  7. Article ; Online: Metallofullerenes as Robust Single-Atom Catalysts for Adsorption and Dissociation of Hydrogen Molecules

    Sehrish Sarfaraz / Muhammad Yar / Ajaz Hussain / Ahmed Lakhani / Adnan Gulzar / Muhammad Ans / Umer Rashid / Masroor Hussain / Shabbir Muhammad / Imene Bayach / Nadeem S. Sheikh / Khurshid Ayub

    ACS Omega, Vol 8, Iss 39, Pp 36493-

    A Density Functional Study

    2023  Volume 36505

    Keywords Chemistry ; QD1-999
    Language English
    Publishing date 2023-09-01T00:00:00Z
    Publisher American Chemical Society
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  8. Article ; Online: Sero-prevalence of Hepatitis B Virus infection in Balochistan province of Pakistan

    Nadeem S Sheikh / Azeem S Sheikh / Aqleem A Sheikh / Samira Yahya / Rafi-U-Shan / Majid Lateef

    Saudi Journal of Gastroenterology, Vol 17, Iss 3, Pp 180-

    2011  Volume 184

    Abstract: Background/Aim: The objective was to evaluate the sero-prevalence of hepatitis B surface antigen (HBsAg) and IgM antibodies to hepatitis core antigen in Balochistan Province of Pakistan. Design of the study: A cross-sectional, population-based study. ... ...

    Abstract Background/Aim: The objective was to evaluate the sero-prevalence of hepatitis B surface antigen (HBsAg) and IgM antibodies to hepatitis core antigen in Balochistan Province of Pakistan. Design of the study: A cross-sectional, population-based study. Place and time of the study: The study was conducted in Balochistan from 1 st January 2004 to 31 st December, 2008. The screening areas included Barkhan, Eashani, Khuzdar, Kodi Zikriani, Kohlu, Rakhni and Turbat. Materials and Methods: A total of 15,260 subjects were enrolled; 11,900 (78%) agreed to undergo screening. Fresh serum samples were tested for the presence of hepatitis B surface antigen and IgM antibodies to hepatitis B core antigen. Results: HBsAg was detected in 1166 (9.8%) while anti-HBc IgM was found in 117 (10.0%). HBsAg positivity was seen in 875 (12.7%) males and 291 (5.8%) females. The prevalence of hepatitis B in Balochistan varies from 3.3% in Khuzdar to 17.0% in Kodi Zikriani. Conclusions: It is utmost important to educate the public, to take proper measures to control the spread of infection and vaccination in order to interrupt transmission of this threatening public health problem in Balochistan province of Pakistan.
    Keywords Cirrhosis ; HBsAg ; hepatitis B ; hepatitis ; prevalence ; Diseases of the digestive system. Gastroenterology ; RC799-869 ; Specialties of internal medicine ; RC581-951 ; Internal medicine ; RC31-1245 ; Medicine ; R
    Subject code 570
    Language English
    Publishing date 2011-01-01T00:00:00Z
    Publisher Medknow Publications
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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