My Publications

@article{Abrar2025,

title = {Enhanced sensitivity in bromochlorodifluoromethane detection: a comparative study of B12N12 and B12P12 nanocages},

author = {Ayesha Abrar and Qazi Muhammad Ahmed and Farrah Arshad and Nasir Shahzad and Khurshid Ayub and Nadeem S. Sheikh and Tabish Jadoon and Faizan Ullah},

doi = {10.1007/s10450-025-00623-6},

issn = {1572-8757},

year  = {2025},

date = {2025-04-00},

journal = {Adsorption},

volume = {31},

number = {4},

publisher = {Springer Science and Business Media LLC},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Natho2025,

title = {Shifting Lithium Amide Reactivity to the Radical Domain: Regioselective Radical C−H Functionalization of 3‐Iodooxetane for the Synthesis of 1,5‐Dioxaspiro[2.3]hexanes},

author = {Philipp Natho and Marco Colella and Annarita Vicenti and Giuseppe Romanazzi and Faizan Ullah and Nadeem S. Sheikh and Andrew J. P. White and Francesco Pasca and Renzo Luisi},

doi = {10.1002/anie.202424346},

issn = {1521-3773},

year  = {2025},

date = {2025-02-21},

urldate = {2025-02-21},

journal = {Angew Chem Int Ed},

publisher = {Wiley},

abstract = {Strained spiro-heterocycles (SSHs) have gained significant attention within the medicinal chemistry community as promising sp3-rich bioisosteres for their aromatic and non-spirocyclic counterparts. We herein report access to an unprecedented spiro-heterocycle—1,5-dioxaspiro[2.3]hexane. Our synthetic approach leverages a lithium-amide induced single-electron transfer to benzophenones generating an N-centered radical and a ketyl radical anion—reminiscent of a frustrated radical pair. This pair works synergistically to selectively abstract the β-hydrogen from 3-iodooxetane, initiating an exergonic radical-radical coupling reaction. This process enables the formation of the desired bond between the oxetane core and benzophenone derivatives, ultimately yielding the novel 1,5-dioxaspiro[2.3]hexane core. The stability and synthetic utility of the novel 1,5-dioxaspiro[2.3]hexane motif are showcased. An in-depth mechanistic investigation is presented, including cyclic voltammetry studies, as well as computational calculations and experiments to support the mechanism of this new single electron synthetic tactic.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{MAQBOOL2024111686,

title = {Finely tuned energy gaps in host-guest complexes: Insights from belt[14]pyridine and fullerene-based nano-Saturn systems},

author = {Maria Maqbool and Annum Ahsan and Faizan Ullah and Ahmed Lakhani and Nadeem S. Sheikh and Tariq Mahmood and Mazhar Amjad Gilani and Khurshid Ayub},

url = {https://www.sciencedirect.com/science/article/pii/S0925963524008999},

doi = {https://doi.org/10.1016/j.diamond.2024.111686},

issn = {0925-9635},

year  = {2024},

date = {2024-10-29},

urldate = {2024-01-01},

journal = {Diamond and Related Materials},

volume = {150},

pages = {111686},

abstract = {Over the past few decades, doping, physisorption and chemisorption remained some of the commonly utilized methods to modify the energy gaps and electronic properties of materials. Yet, achieving precise control over tuning the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) levels within these systems persisted as a remarkable challenge. Therefore, there is a growing need for systems that facilitate exact adjustments of energy gaps and HOMO/LUMO levels. Here, in this research work, the nano-Saturn host-guest complex systems are designed based on belt[14]pyridine as a host and fullerene nanocages (C20, C32, C34 and C36) as guests. The greater thermodynamic stability of the complexes is revealed by the higher values of interaction energies (Eint) for these complexes, ranging from −45.50 to −56.81 kcal/mol. The frontier molecular orbital (FMO) analysis revealed the contribution of HOMO of fullerenes and LUMO of belt[14]pyridine towards the HOMO and LUMO of the designed complexes, respectively. The energy gaps of the complexes also decrease compared to the constituents, with the least Egap of 0.52 eV observed for C20@N-belt. Moreover, the charge transfer from the host towards the guests is predicted and confirmed via natural bond orbital (NBO) and electron density difference (EDD) analyses. The non-covalent interaction index (NCI) and quantum theory of atoms in molecules (QTAIM) analyses determine the nature and strength of interactions in the host-guest complexes. Moreover, it is noticed through the UV–vis analysis that the bare fullerenes show the maximum absorption in ultraviolet (UV) region, but after complexation, maximum absorption is observed in visible and near infrared (NIR) regions, with highest λmax of 927 nm for C36@N-belt. These findings highlight the successful development of nano-Saturn host-guest complexes with precise control over HOMO-LUMO levels and energy gaps. This work aims to address the challenges in fine-tuning the electronic properties and demonstrates potential applications in optoelectronics, photovoltaics, and NIR-based sensors. Moreover, the ability to tune the electronic properties can guide future material design strategies for advanced energy storage and photonic devices.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Ahmed2024,

title = {Exploring hydrogen storage capabilities of boron nitride nanoring through density functional theory},

author = {Qazi Muhammad Ahmed and Adil Sultan and Ayesha Abrar and Farrah Arshad and Nasir Shahzad and Khurshid Ayub and Tabish Jadoon and Faizan Ullah},

url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/est2.590},

doi = {https://doi.org/10.1002/est2.590},

year  = {2024},

date = {2024-02-28},

urldate = {2024-02-28},

journal = {Energy Storage},

volume = {6},

number = {1},

pages = {e590},

abstract = {This study presents Density Functional Theory (DFT) investigation into the hydrogen storage capabilities of B6N6 nanoring. Utilizing the ωB97XD functional and def2TZVP basis set, this research explores the geometric, energetic, and electronic properties of the B6N6 nanoring, highlighting its potential as an efficient material for hydrogen storage. In-depth analyses of the HOMO-LUMO electronic density, Natural Bond Orbital (NBO) charge, Non-Covalent Interactions (NCI), and Density of States (DOS) are conducted to understand the electronic structure changes during hydrogen adsorption. Furthermore, the desorption temperatures of hydrogen from the B6N6 nanoring, as calculated through the Van't Hoff equation, fall within a range considerably higher than the critical point of hydrogen. This finding indicates the practical feasibility of the B6N6 nanoring in hydrogen storage applications. Notably, the hydrogen storage capacity, measured in terms of gravimetric density, shows a significant increase with the addition of hydrogen molecules, reaching a maximum of 9.77% for 8H2 adsorbed on B6N6. Overall, this study underscores the B6N6 nanoring as a promising candidate for addressing the current challenges in hydrogen storage, particularly in terms of capacity, stability, and operational temperature.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{AETIZAZ2024114469,

title = {Investigating the sensing efficiency of C6O6Li6 for detecting lung cancer-related volatile organic compounds: A computational density functional theory approach},

author = {Muhammad Aetizaz and Faizan Ullah and Tariq Mahmood and Khurshid Ayub},

url = {https://www.sciencedirect.com/science/article/pii/S2210271X24000082},

doi = {https://doi.org/10.1016/j.comptc.2024.114469},

issn = {2210-271X},

year  = {2024},

date = {2024-01-12},

urldate = {2024-01-01},

journal = {Computational and Theoretical Chemistry},

volume = {1232},

pages = {114469},

abstract = {Volatile organic compounds (VOCs), such as acetone (AC), isoprene (IS), 1-hexene (HX), and benzene (BN), are important biomarkers in the exhaled breath of lung cancer patients. This research evaluates the potential of C6O6Li6 as a sensor for detecting these VOCs in the early stages of lung cancer. The adsorption of VOCs on C6O6Li6 was explored using Density Functional Theory (DFT) calculations at ωB97X-D3/def2-TZVP level of theory. Interaction energies for the most stable complexes were observed as −18.08 kcal/mol for AC@C6O6Li6, −14.06 kcal/mol for HX@C6O6Li6, −9.12 kcal/mol for IS@C6O6Li6, and −8.31 kcal/mol for BN@C6O6Li6. These values indicate the physiosorption of VOCs on C6O6Li6. Noncovalent interactions between the VOCs and C6O6Li6 were studied through Quantum Theory of Atom in Molecule (QTAIM) and Non-Covalent Interaction (NCI) analyses. The electronic properties were evaluated through Frontier Molecular Orbital (FMO), Natural Bond Orbital (NBO), Electron Density Difference (EDD), and Density of States (DOS) analyses. FMO analysis shows an increase in the HOMO-LUMO energy gap upon interaction of these VOCs with the C6O6Li6 surface, while NBO analysis indicates charge transfer from the surface to the VOCs. This study significantly enhances our understanding of C6O6Li6′s potential as a sensor material for early lung cancer detection using breath biomarkers.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Ullah_2023,

title = {Potential of first row transition metal decorated graphtriyne quantum dots as single atom catalysts towards hydrogen evolution reaction (HER)},

author = {Faizan Ullah and Mazhar Amjad Gilani and Muhammad Imran and Khurshid Ayub and Tariq Mahmood},

url = {https://dx.doi.org/10.1088/1402-4896/ad01f6},

doi = {10.1088/1402-4896/ad01f6},

year  = {2023},

date = {2023-10-19},

urldate = {2023-10-19},

journal = {Physica Scripta},

volume = {98},

number = {11},

pages = {115308},

publisher = {IOP Publishing},

abstract = {To advance the clean energy systems based on hydrogen, highly efficient and low-cost electrocatalysts for the hydrogen evolution reaction (HER) are of paramount importance. In recent years, single atoms embedded within 2-dimensional (2D) material substrates have emerged as exceptional catalysts for HER. Graphtriyne, a 2D material due to its novel electronic properties is a promising substrate for development of single atom catalysts. In this study, we employed density functional theory (DFT) simulations to investigate the potential of transition metals (Fe, Co, Ni, Cu, and Zn) anchored on graphtriyne quantum dot as single atom catalysts (SACs) for HER. Our results revealed that Zn and Ni SACs anchored on graphtriyne quantum dot exhibit excellent HER performance. Additionally, we calculated total density of states (TDOS), partial density of states (PDOS), HOMO, LUMO energies and HOMO–LUMO energy gap for the proposed SACs. Our work presents a promising approach for the development of HER catalysts, utilizing graphtriyne quantum dot as support material and transition metal atoms (Fe, Co, Ni, Cu, and Zn) as the single atom centers.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{D3RA04019D,

title = {Robust and facile detection of formaldehyde through transition metals doped olympicene sensors: a step forward DFT investigation},

author = {Muhammad Aetizaz and Faizan Ullah and Sehrish Sarfaraz and Tariq Mahmood and Khurshid Ayub},

url = {http://dx.doi.org/10.1039/D3RA04019D},

doi = {10.1039/D3RA04019D},

year  = {2023},

date = {2023-10-05},

urldate = {2023-01-01},

journal = {RSC Advances},

volume = {13},

issue = {42},

pages = {29231-29241},

publisher = {The Royal Society of Chemistry},

abstract = {Formaldehyde, a volatile organic compound (VOC) released by building and decoration materials, has many applications in the chemical feedstock industry. Excessive release of formaldehyde can cause serious health issues, such as chest tightness, cough, cancer, and tissue damage. Therefore, detection of formaldehyde is required. Herein transition metal (Fe, Ni, and Pd) doped olympicene is evaluated as a gas sensor for the detection of formaldehyde. The performance of the designed electrochemical sensor is evaluated through interaction energy, natural bond orbital (NBO) non-covalent interaction (NCI), electron density differences (EDD), electrostatic potential (ESP), quantum theory of atom in molecule (QTAIM), frontier molecular orbital (FMO), and density of states (DOS) analysis. Interaction energies obtained at B3LYP-D3/def-2 TZVP level of theory shows that formaldehyde is physiosorbed over the surface of transition metal doped olympicene. The trend for interaction energy is OLY(Ni)/HCHO > OLY(Fe)/HCHO > OLY(Pd)/HCHO. The presence of non-covalent interactions is confirmed by the QTAIM and NCI analyses, while transfer of charges is confirmed by natural bond orbital analysis. The reduced density gradient (RDG) approach using noncovalent interaction (NCI) analysis demonstrates that electrostatic hydrogen bonding interactions prevail in the complexes. Recovery time is calculated to check the reusability of the sensor. This study may provide a deep insight for the designing of highly efficient electrochemical sensor against formaldehyde with transition metals doped on olympicene.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{molecules28104060,

title = {Transition Metal Sensing with Nitrogenated Holey Graphene: A First-Principles Investigation},

author = {Uroosa Sohail and Faizan Ullah and Nur Hazimah Binti Zainal Arfan and Malai Haniti Sheikh Abdul Hamid and Tariq Mahmood and Nadeem S. Sheikh and Khurshid Ayub},

url = {https://www.mdpi.com/1420-3049/28/10/4060},

doi = {10.3390/molecules28104060},

issn = {1420-3049},

year  = {2023},

date = {2023-05-12},

urldate = {2023-05-12},

journal = {Molecules},

volume = {28},

number = {10},

abstract = {The toxicity of transition metals, including copper(II), manganese(II), iron(II), zinc(II), hexavalent chromium, and cobalt(II), at elevated concentrations presents a significant threat to living organisms. Thus, the development of efficient sensors capable of detecting these metals is of utmost importance. This study explores the utilization of two-dimensional nitrogenated holey graphene (C2N) nanosheet as a sensor for toxic transition metals. The C2N nanosheet’s periodic shape and standard pore size render it well suited for adsorbing transition metals. The interaction energies between transition metals and C2N nanosheets were calculated in both gas and solvent phases and were found to primarily result from physisorption, except for manganese and iron which exhibited chemisorption. To assess the interactions, we employed NCI, SAPT0, and QTAIM analyses, as well as FMO and NBO analysis, to examine the electronic properties of the TM@C2N system. Our results indicated that the adsorption of copper and chromium significantly reduced the HOMO–LUMO energy gap of C2N and significantly increased its electrical conductivity, confirming the high sensitivity of C2N towards copper and chromium. The sensitivity test further confirmed the superior sensitivity and selectivity of C2N towards copper. These findings offer valuable insight into the design and development of sensors for the detection of toxic transition metals.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Kosar2023,

title = {Reversible H2 Storage Capacity of Ni Functionalized Carbyne (C10) Complex},

author = {Naveen Kosar and Maryium Bibi and Faizan Ullah and Mazhar Amjad Gilani and Mohammed Salim Akhter and Khurshid Ayub and Tariq Mahmood},

url = {https://doi.org/10.1007/s10904-022-02516-5},

doi = {10.1007/s10904-022-02516-5},

issn = {1574-1451},

year  = {2022},

date = {2022-12-26},

urldate = {2022-12-26},

journal = {Journal of Inorganic and Organometallic Polymers and Materials},

volume = {33},

number = {2},

pages = {515-528},

abstract = {In this study, we explored the reversible hydrogen storage capacity of Ni functionalized C10 carbyne complex through density functional theory (DFT) and molecular dynamic (MD) calculations. ωB97X-D3/def2-TZVP and DLPNO-CCSD(T)/def2-TZVPP methods are used for the estimation of adsorption energies. NiC10 complex is observed to be more sensitive toward hydrogen adsorption compared to isolated C10 carbyne. The nH2-NiC10 complexes are stable when n ≤ 5, and adsorption energies are in the range of − 0.89 to − 0.22 eV/H2 molecule while the hydrogen storage capacity is about 1.11 to 5.33 wt% for hydrogen molecule. For desorption of H2, molecular dynamic calculations are performed at ωB97X-D3 with def2-TZVP O using RCA ABMD package in which the complexes showed stability to desorption up to 2000 steps. This study illustrates the potential of nickel-doped carbyne C10 complex for the storage of hydrogen and applications in fuel cells.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{SADIA2023113966,

title = {DFT study about capturing of toxic sulfur gases over cyclic tetrapyrrole},

author = {Haleema Sadia and Saif Ullah and Faizan Ullah and Tabish Jadoon},

url = {https://www.sciencedirect.com/science/article/pii/S2210271X22003796},

doi = {https://doi.org/10.1016/j.comptc.2022.113966},

issn = {2210-271X},

year  = {2022},

date = {2022-12-02},

urldate = {2023-01-01},

journal = {Computational and Theoretical Chemistry},

volume = {1219},

pages = {113966},

abstract = {The development of sensors that can detect hazardous analytes selectively and accurately, particularly sulfur based irritants, is quite essential. The infinite-conjugation in cyclic conducting polymers make them highly sensitive to toxic analytes. We implemented B3LYP-D3/6–311 + G (d, p) level to explore the sensing mechanism of cyclic tetrapyrrole (CTPy) for reliable detection of carbonyl sulfide, carbon disulfide, hydrogen sulfide sulfur monoxide, sulfur dioxide and sulfur trioxide using the DFT practice. The interaction energies, Eint ranges from –25.6 to –89.2 kJ mol−1 for sulfur gases over CTPy. Charge transfer interactions in complexes are predicted using natural bond orbital (NBO) and charge decomposition (CDA) analysis. The reduced density gradient (RDG) method supports hydrogen bonding and dispersion interactions in the complexes. The decrease in HOMO-LUMO energy gaps, as well as the red shifting of λmax in UV–Visible spectra, demonstrate sensitivity of CTPy towards sulfur gases. The improved conductivity of complexes is owing to production of numerous energy levels inoccupied and virtual orbitals closer to the Fermi level in DOS spectra. Furthermore, PDOS spectra reveal that CTPy is chiefly contribute to energy of HOMO. The recent findings show CTPy has a significant sensitivity to sulfurirritants. We hope that the above findings and their implications will give valuable suggestions for an experimentalist in designing extremely sensitive hazardous analyte sensors employing CTPy.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Sohail2022,

title = {Adsorption of Industrial Gases (CH4, CO2, and CO) on Olympicene: A DFT and CCSD(T) Investigation},

author = {Uroosa Sohail and Faizan Ullah and Tariq Mahmood and Shabbir Muhammad and Khurshid Ayub},

url = {https://doi.org/10.1021/acsomega.2c01796},

doi = {10.1021/acsomega.2c01796},

year  = {2022},

date = {2022-05-23},

urldate = {2022-05-23},

journal = {ACS Omega},

volume = {7},

number = {22},

pages = {18852-18860},

abstract = {Olympicene C19H12, an organic semiconductor, is investigated as an adsorption material for toxic industrial gas molecules such as CH4, CO2, and CO. A deep insight of complexation of CH4, CO2, and CO with olympicene (analyte@OLY) was obtained by interaction energy, symmetry-adopted perturbation theory (SAPT2+), quantum theory of atoms in molecules (QTAIM), density of states (DOS), noncovalent interaction (NCI), and frontier molecular orbital and natural bond orbital analysis. Domain-based local pair natural orbital coupled cluster theory single-point energy calculations were performed using the cc-pVTZ basis set in combination with corresponding auxiliary cc-pVTZ/JK and cc-pVTZ/C basis sets. For all property calculations of doped olympicene complexes, the ωB97M-V functional was employed. The stability trend for interaction energies is CO2@OLY > CH4@OLY > CO@OLY. QTAIM and NCI analysis confirmed the presence of NCIs, where the dispersion factor (in CH4@OLY) has the highest contribution, as revealed from SAPT2+. The chemical sensitivity of the system was evidenced by the origination of new energy states in DOS spectra. The recovery time for the analyte@OLY complex was calculated at 300 K, and an excellent recovery response was observed. All results evidently indicated weak interactions of the olympicene surface with CH4, CO2, and CO.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Ullah2022,

title = {Inclusive DFT insight into sensing mechanism of cyclotetrapyrole towards lung irritants},

author = {Saif Ullah and Haleema Sadia and Faizan Ullah and Tabish Jadoon},

url = {https://doi.org/10.1007/s00894-022-05100-3},

doi = {10.1007/s00894-022-05100-3},

issn = {0948-5023},

year  = {2022},

date = {2022-04-02},

urldate = {2022-04-02},

journal = {Journal of Molecular Modeling},

volume = {28},

number = {5},

pages = {110},

abstract = {The development of smart sensing devices for toxic analytes detection especially lung irritants is much essential. The cyclic conducting polymers having infinite π-conjugation are proved to be highly sensitive for toxic analytes. Herein, by using the DFT approach, we investigated the sensing mechanism of cyclotetrapyrole (CTPy) for accurate detection of phosgene, diphosgene, chloropicrin and chlorine at the B3LYP-D3/6–31 + G (d, p) level. The calculated interaction energies show the physisorption of analytes over the CTPy surface. Natural bond orbital (NBO) and charge decomposition (CDA) analyses predict charge transfer interactions in the complexes. The reduced density gradient (RDG) approach reveals that hydrogen bonding interactions dominate in the complexes. The sensitivity of CTPy towards lung irritants is further illustrated by the reduction in HOMO–LUMO energy gaps, red shifting of $${lambda }_{mathrm{max}}$$in UV–Visible spectra. Density of state (DOS) analysis affirm that enhanced conductivity upon complexation is due to the origination of new energy states in occupied and virtual orbitals nearer to the Fermi level. Moreover, PDOS spectra show that CTPy primarily contributes to the energy of HOMO. The outcome of the current study depicts appreciable sensitivity of CTPy towards lung irritants. Moreover, the competing role of naturally occurring atmospheric water is also investigated. We believe that the upshot of the current findings and their forecasts will provide useful guidelines for an experimentalist to design highly sensitive sensors for toxic analytes using CTPy.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{SOHAIL2022106620,

title = {Olympicene as a high-performance sensor for lung irritants: A dispersion corrected DFT insight},

author = {Uroosa Sohail and Faizan Ullah and Tariq Mahmood and Khurshid Ayub},

url = {https://www.sciencedirect.com/science/article/pii/S1369800122001639},

doi = {https://doi.org/10.1016/j.mssp.2022.106620},

issn = {1369-8001},

year  = {2022},

date = {2022-03-11},

urldate = {2022-01-01},

journal = {Materials Science in Semiconductor Processing},

volume = {144},

pages = {106620},

abstract = {Surge for the development of sensor for selective and accurate detection of toxic warfare agents especially lung irritants is increasing day by day. Herein, by using the DFT approach, we explored the sensing ability of olympicene C19H12 (OLY) for accurate detection of chlorine, chloropicrin, phosgene, and diphosgene. The computed interaction energies at ωB97M-V/def2-TZVP level of theory show that lung irritants are physiosorbed over the olympicene surface. The charge transfer interactions of all the complexes are predicted by charge decomposition analysis (CDA) and Natural bond orbital (NBO) analysis. The reduced density gradient (RDG) approach indicates the dominance of electrostatic hydrogen bonding interactions in the complexes through non-covalent interaction (NCI) analysis. Moreover, the sensitivity of olympicene towards lung irritants is illustrated by the reduction in HOMO-LUMO energy gaps. The SAPT2+ analysis reveals that the dispersion factor remained dominant for stabilization of analyte@OLY complexes. Recovery time of olympicene is calculated to reveal the reusability of sensor at different temperatures. The upshot of the current study affirms appreciable selectivity of olympicene towards lung irritants. All findings and their prospects will supply effective and practical guidelines for an experimentalist to construct highly sensitive sensors for toxic warfare agents using olympicene.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Wajid2021,

title = {Demonstrating the Potential of Alkali Metal-Doped Cyclic C6O6Li6 Organometallics as Electrides and High-Performance NLO Materials},

author = {Sunaina Wajid and Naveen Kosar and Faizan Ullah and Mazhar Amjad Gilani and Khurshid Ayub and Shabbir Muhammad and Tariq Mahmood},

url = {https://doi.org/10.1021/acsomega.1c04349},

doi = {10.1021/acsomega.1c04349},

year  = {2021},

date = {2021-10-29},

urldate = {2021-01-01},

journal = {ACS Omega},

volume = {6},

number = {44},

pages = {29852-29861},

abstract = {In this report, the geometric and electronic properties and static and dynamic hyperpolarizabilities of alkali metal-doped C6O6Li6 organometallics are analyzed via density functional theory methods. The thermal stability of the considered complexes is examined through interaction energy (Eint) calculations. Doping of alkali metal derives diffuse excess electrons, which generate the electride characteristics in the respective systems (electrons@complexant, e–@M@C6O6Li6, M = Li, Na, and K). The electronic density shifting is also supported by natural bond orbital charge analysis. These electrides are further investigated for their nonlinear optical (NLO) responses through static and dynamic hyperpolarizability analyses. The potassium-doped C6O6Li6 (K@C6O6Li6) complex has high values of second- (βtot = 2.9 × 105 au) and third-order NLO responses (γtot = 1.6 × 108 au) along with a high refractive index at 1064 nm, indicating that the NLO response of the corresponding complex increases at a higher wavelength. UV–vis absorption analysis is used to confirm the electronic excitations, which occur from the metal toward C6O6Li6. We assume that these newly designed organometallic electrides can be used in optical and optoelectronic fields for achieving better second-harmonic-generation-based NLO materials.},

note = {PMID: 34778658},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{ULLAH202137814,

title = {High performance SACs for HER process using late first-row transition metals anchored on graphyne support: A DFT insight},

author = {Faizan Ullah and Khurshid Ayub and Tariq Mahmood},

url = {https://www.sciencedirect.com/science/article/pii/S0360319921035436},

doi = {https://doi.org/10.1016/j.ijhydene.2021.09.063},

issn = {0360-3199},

year  = {2021},

date = {2021-10-20},

urldate = {2021-01-01},

journal = {International Journal of Hydrogen Energy},

volume = {46},

number = {76},

pages = {37814-37823},

abstract = {For ever-growing demand of clean and renewable energy resources, finding a low-cost, earth abundant, and an efficient electrocatalyst to replace platinum-based catalysts for hydrogen evolution reaction (HER) has drawn the interest of scientific community. In present work, first-row transition metal single atom catalysts supported on graphyne surface have been designed and investigated using density functional theory approach. The results indicate that among all considered systems, the highest thermodynamic stability and best HER catalytic performance is computed for Ni single atom catalyst (SAC) anchored on graphyne support with low ΔGH∗ value of 0.08 eV. We have calculated density of states, energies of HOMO, LUMO and HOMO-LUMO gap for our designed single atom catalysts as well as hydrogen adsorption. Our results indicate that Ni anchored on graphyne support can be a promising candidate for noble metal free, earth abundant, and low cost electrocatalyst to efficiently catalyze hydrogen evolution reaction process.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{ULLAH2021113470,

title = {C10F as a potential anode material for alkali-ion batteries; a quantum chemical approach},

author = {Faizan Ullah and Khurshid Ayub and Mazhar Amjad Gilani and Muhammad Imran and Tariq Mahmood},

url = {https://www.sciencedirect.com/science/article/pii/S2210271X21003285},

doi = {https://doi.org/10.1016/j.comptc.2021.113470},

issn = {2210-271X},

year  = {2021},

date = {2021-10-13},

urldate = {2021-01-01},

journal = {Computational and Theoretical Chemistry},

volume = {1206},

pages = {113470},

abstract = {Using DFT and DLPNO-CCSD(T) calculations, we explored electronic and energetic properties of F doped carbyne C10 ring to form C10F complex and its potential application as anode material in alkali-ion batteries. The adsorption of alkali metal (AM/AM+) is investigated on C10F complex. The adsorption free energies of K and K+are –0.75 and –77.34 kcal mol−1, respectively which give rise to cell voltage (Vcell) of 3.32 V. The electrochemical cell volage for Li/Li + and Na/Na + are 3.12 V and 2.80 V, respectively. A large storage capacity of 579 mAh g−1 is achieved for all three studied LIBs, SIBs, and KIBs. These results present C10F complex as a promising anode material for alkali-ion batteries.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{JADOON2021117415,

title = {Adsorption mechanism of p- aminophenol over silver-graphene composite: A first principles study},

author = {Tabish Jadoon and Atazaz Ahsin and Faizan Ullah and Tariq Mahmood and Khurshid Ayub},

url = {https://www.sciencedirect.com/science/article/pii/S0167732221021395},

doi = {https://doi.org/10.1016/j.molliq.2021.117415},

issn = {0167-7322},

year  = {2021},

date = {2021-09-06},

urldate = {2021-01-01},

journal = {Journal of Molecular Liquids},

volume = {341},

pages = {117415},

abstract = {Herein, we report the theoretical insight into the adsorption mechanism of p-Aminophenol on graphene, silver cluster and silver graphene composites. DFT calculations are performed at M06-2X/LANL2DZ level of theory to explore the adsorption mechanism of p-Aminophenol (p-AP) over a bare coronene, a coplanar silver cluster (Ag6), and two isomers of silver-graphene composites (isomer 1 and isomer 2). The highest Eint is found in p-AP@Ag6 (−15.15 kcal mol−1) while the lowest is calculated for isomer 2 (−12.31 kcal mol−1). NCI results show that electrostatic forces have a strong influence on the stability of p-AP@Ag6 and also of isomer 1, which results in their higher stability. Additionally, MD simulations confirmed that the adsorption of p-Aminophenol over silver-graphene composite is stable and efficient at room temperature. The adsorption mechanism in these complexes is further explored through variations in; absorption maximum (λmax), excitation energies, and oscillator strength (fo). The values of Eint and shift of λmax decreases in the order p-AP@Ag6 > isomer 1 > p-AP@coronene ˃ isomer 2. NBO and CDA analysis are performed to gain a deeper insight into the direction and amount of charge transfer between donor and acceptor units. The degree of charge transfer as measured by the NBO charges decreases in the order isomer 1 > p-AP@Ag6 > isomer 2 > p-AP@coronene. The transfer of electron density from the analyte in the complexes is solely due to the contribution of the p-orbital in the HOMO. Orbital hybridization in the complexes results in the generation of new occupied and virtual energy states, and the appearance of new energy states close to the Fermi level causes a reduction in HOMO-LUMO gaps, and hence enhanced conductivity of p-Aminophenol complexes. The outcome of the current study will provide useful guidelines in the development of promising sensing material for p-Aminophenol.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{JADOON2021106023,

title = {Silver cluster decorated graphene nanoflakes for selective and accurate detection of nitroaniline isomers; DFT calculations},

author = {Tabish Jadoon and Faizan Ullah and Tariq Mahmood and Khurshid Ayub},

url = {https://www.sciencedirect.com/science/article/pii/S1369800121003693},

doi = {https://doi.org/10.1016/j.mssp.2021.106023},

issn = {1369-8001},

year  = {2021},

date = {2021-06-22},

urldate = {2021-01-01},

journal = {Materials Science in Semiconductor Processing},

volume = {134},

pages = {106023},

abstract = {DFT study is carried out to explore silver cluster decorated graphene sensors for the selective and accurate detection of poor biodegradable and highly toxic nitroaniline isomers. In current study the most stable structures are evaluated through interaction energies (Eint), NBO charge transfer (QNBO), HOMO-LUMO gap, UV–Visible, NCI and CDA analyses. The stability order of nitroaniline complexes is analyte@Ag6-coronene > analyte@Ag6 > analyte@coronene > analyte@coronene-Ag6. The higher stability of analyte@Ag6-coronene complexes is due to dominating Ag⋯O electrostatic interactions. The higher NBO charge transfer from analyte towards substrate is observed in the complexes where analyte directly interacts with Ag6 surface. Highest QNBO transferred (−1.369 e−) and highest interaction energy (−172.42 kJ/mol) are observed in meta-Nitroaniline@Ag6-coronene complex. DOS spectra reveal that both analyte and Ag6 mainly contribute to energy of highest occupied molecular orbitals. NCI results advocate the presence of electrostatic and van der Waals interactions besides steric clashes in analyte@silver-coronene complexes. The evaluated results authenticate the excellent sensing ability of silver-graphene composites for the selective and accurate detection of nitroaniline isomers. The upshot of the current findings and its prospects will be a smart choice for sensor development in near future.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{ASIF2021113221,

title = {Quantum chemical study on sensing of NH3, NF3, NCl3 and NBr3 by using cyclic tetrapyrrole},

author = {Misbah Asif and Hasnain Sajid and Faizan Ullah and Sidra Khan and Khurshid Ayub and Mazhar Amjad Gilani and Muhammad Arshad and Mohammed Salim Akhter and Tariq Mahmood},

url = {https://www.sciencedirect.com/science/article/pii/S2210271X21000803},

doi = {https://doi.org/10.1016/j.comptc.2021.113221},

issn = {2210-271X},

year  = {2021},

date = {2021-03-26},

urldate = {2021-01-01},

journal = {Computational and Theoretical Chemistry},

volume = {1199},

pages = {113221},

abstract = {Toxic gas sensors with ultrahigh sensitivity are highly desirable and those can be achieved with the help of infinite π-conjugation of cyclic conducting polymers. In this DFT study, we demonstrate the adsorption performance of tetracyclic oligopyrrole (CTPy) towards NH3 and nitrogen halides including NF3, NCl3 and NBr3. The CTPy possesses infinite conjugation and highly active cavity which provides an excellent platform for the adsorption of upcoming gas molecules. Thermodynamically, the observed interaction energies of NH3, NF3, NCl3 and NBr3 analytes with CTPy at ωB97XD/6-31+G(d,p) level of theory are −13.14, −3.00, −6.00 and −7.50 kcal/mol, respectively. In addition, the molecular dynamic simulations are performed at GFN2-xTB method to confirm the stability of CTPy and respective complexes. The SAPT0 and NCI analyses reveal that dispersion forces play a significant role to stablize these complexes. Moreover, the electrostatic component also contributes in stabilizing the NH3@CTPy, NCl3@CTPy and NBr3@CTPy complexes. The variation in the electronic properties including HOMO-LUMO gaps of complexes along with the significant NBO charge transfer indicate the increasing conductivity of CTPy upon complexation with reported analytes. The prominent charge transfer on interaction might be due to the increasing π to π* transition, thus the λmax is shifted to longer wavelength in UV–vis spectra.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{AHMAD2021129854,

title = {Synthesis, single crystal X-ray, spectroscopic and computational (DFT) studies 2,1-benzothiazine based hydrazone derivatives},

author = {Shakeel Ahmad and Tariq Mahmood and Matloob Ahmad and Muhammad Nadeem Arshad and Faizan Ullah and Muhammad Shafiq and Sana Aslam and Abdullah M. Asiri},

url = {https://www.sciencedirect.com/science/article/pii/S0022286020321670},

doi = {https://doi.org/10.1016/j.molstruc.2020.129854},

issn = {0022-2860},

year  = {2021},

date = {2021-01-21},

urldate = {2021-01-01},

journal = {Journal of Molecular Structure},

volume = {1230},

pages = {129854},

abstract = {2,1-Benzothiazine-4(3H)-one 2,2-dioxide was synthesized through a multistep procedure starting with methyl anthranilate. It was reacted with hydrazine monohydrate to form corresponding hydrazine derivative which was subsequently treated with acetone and cyclopentanone respectively to get benzothiazine based hydrazones. Both the molecules were crystalized in monoclinic crystal system with P2 1/n and P2 1/c space groups for first and second molecules, respectively. The thiazine ring in both molecules adopted the envelope shape conformation. Moreover, both the structures were stabilized by hydrogen bonding interactions. DFT calculations were performed for the validation of geometric parameters obtained through X-ray diffraction studies. Moreover, the DFT calculations are also executed for the investigation of reactivities and reactive sites as well.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{D0RA08099C,

title = {Remarkable static and dynamic NLO response of alkali and superalkali doped macrocyclic [hexa-]thiophene complexes; a DFT approach},

author = {Hasnain Sajid and Faizan Ullah and Sidra Khan and Khurshid Ayub and Muhammad Arshad and Tariq Mahmood},

url = {http://dx.doi.org/10.1039/D0RA08099C},

doi = {10.1039/D0RA08099C},

year  = {2021},

date = {2021-01-20},

urldate = {2021-01-01},

journal = {RSC Advances},

volume = {11},

issue = {7},

pages = {4118-4128},

publisher = {The Royal Society of Chemistry},

abstract = {In this study, the nonlinear optical (NLO) response of alkali metal atom (Li, Na and K) and their corresponding superalkali (Li3O, Na3O and K3O) doped six membered cyclic thiophene (6CT) has been explored. The optimized geometries of complexes; Li@6CT, Na@6CT, K@6CT, Li3O@6CT, Na3O@6CT and K3O@6CT depict that the superalkalis and alkali metals interact through the active cavity of 6CT. Interaction energies reveal that superalkalis have higher interaction with 6CT than alkali metals. The nonlinear optical (NLO) response of the reported complexes is estimated via both static and dynamic hyperpolarizabilities which are further rationalized by the HOMO–LUMO gap, natural bond orbital (NBO) charge transfer, dipole moment, polarizabilities and βvec. A remarkably high NLO response is computed for Na3O@6CT among all of the complexes. The static hyperpolarizability of the Na3O@6CT complex is 5 × 104 au along with the highest βvec value (2.5 × 104 au). High charge transfer (1.53e−) and small EH–L gap (2.96 eV) is responsible for such a large NLO response. For dynamic NLO responses, electro-optic Pockel's effect (EOPE) and second-harmonic generation (SHG) are explored. A very large quadratic nonlinear optical response (3.8 × 10−12 au) is observed for the Na3O@6CT complex. Moreover, the absorption spectrum of the Na3O@6CT complex shows ultra-high transparency in the ultraviolet and visible regions unlike any other of its counterparts.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{ULLAH2021109914,

title = {Nonlinear optical response of first-row transition metal doped Al12P12 nanoclusters; a first-principles study},

author = {Faizan Ullah and Sundus Irshad and Saima Khan and Muhammad Ali Hashmi and Ralf Ludwig and Tariq Mahmood and Khurshid Ayub},

url = {https://www.sciencedirect.com/science/article/pii/S0022369720328146},

doi = {https://doi.org/10.1016/j.jpcs.2020.109914},

issn = {0022-3697},

year  = {2020},

date = {2020-12-31},

urldate = {2021-01-01},

journal = {Journal of Physics and Chemistry of Solids},

volume = {151},

pages = {109914},

abstract = {The influence of first-row transition metals on structural, electronic, and nonlinear optical (NLO) properties of aluminum phosphide (Al12P12) inorganic fullerene is investigated through DFT methods. The designed M@Al12P12 composites are thermodynamically quite stable. Frontier orbital analysis revealed that HOMO–LUMO energy gap of Al12P12 nanocluster is fairly reduced in the presence of transition metals which is mainly attributed to the formation of new high HOMO energy levels due to excess electrons. Based on the NBO analysis, the charge is transferred from transition metal to the Al12P12 nanocluster. The calculated polarizability (αo) and the first hyperpolarizability (βo) values indicated that nonlinear optical response is remarkably enhanced under the influence of first-row transition metals. These M@Al12P12 composites possess giant first hyperpolarizabilities in the range of 3.1 × 102–5.9 × 106 au. This study may provide valuable insights for the designing of new high-performance materials for optoelectronic devices.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{IRSHAD2021106570,

title = {First row transition metals decorated boron phosphide nanoclusters as nonlinear optical materials with high thermodynamic stability and enhanced electronic properties; A detailed quantum chemical study},

author = {Sundus Irshad and Faizan Ullah and Saima Khan and Ralf Ludwig and Tariq Mahmood and Khurshid Ayub},

url = {https://www.sciencedirect.com/science/article/pii/S0030399220312032},

doi = {https://doi.org/10.1016/j.optlastec.2020.106570},

issn = {0030-3992},

year  = {2020},

date = {2020-09-15},

urldate = {2021-01-01},

journal = {Optics & Laser Technology},

volume = {134},

pages = {106570},

abstract = {Electronic as well as nonlinear optical properties (first hyperpolarizabilities) of boron phosphide nanoclusters doped with first row transition metals (Sc–Zn) are explored using density functional theory (DFT) calculations. Four different doping sites (b64, b66, r4, and r6) of the B12P12 nanocluster are considered for doping of the transition metals. Computational results revealed that these transition metals doped boron phosphide complexes are highly stable, and their HOMO–LUMO energy gaps are considerably reduced as compared to the pristine B12P12 nanocage. The highest interaction energy (−74.42 kcal mol−1) is observed for Ni@r4-B12P12 complex. The lowest HOMO–LUMO energy gap (1.44 eV) is computed for Sc@b64-B12P12 complex. Moreover, adsorption of the first row transition metals (Sc–Zn) on the surface of B12P12 nanocluster significantly enhanced the nonlinear optical response of the resultant complexes. The highest static first hyperpolarizability value (4.4 × 104 au) is computed for Sc@r4-B12P12 complex. Moreover, frequency dependent hyperpolarizability calculations are also performed to evaluate the practicality of the transition metal doped boron phosphide (M@B12P12) complexes. The highest electro-optical Pockels effect (EOPE) value of 4.4 × 105 au is computed for Sc@r4-B12P12 complex while Sc@r6-B12P12 gives the highest second harmonic generation (SHG) value of 1.1 × 105 au. This study will be advantageous for providing guidance in further designing of new high-performance nonlinear optical (NLO) materials.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{KOSAR2021105437,

title = {Theoretical investigation of halides encapsulated Na@B40 nanocages for potential applications as anodes for sodium ion batteries},

author = {Naveen Kosar and Faizan Ullah and Khurshid Ayub and Umer Rashid and Muhammad Imran and Muhammad Naeem Ahmed and Tariq Mahmood},

url = {https://www.sciencedirect.com/science/article/pii/S136980012031372X},

doi = {https://doi.org/10.1016/j.mssp.2020.105437},

issn = {1369-8001},

year  = {2020},

date = {2020-09-12},

urldate = {2021-01-01},

journal = {Materials Science in Semiconductor Processing},

volume = {121},

pages = {105437},

abstract = {The increasing demand of energy storage materials has attracted considerable attention of scientific community towards the development of rechargeable ion batteries (RIBs). Herein, B40 nanoclusters are theoretically analyzed for their potential application as anode material for sodium-ion batteries. DFT calculations are performed for geometrical and electrochemical properties study of Na or Na+ adsorbed A−@B40 (A− = F-, Cl- and Br-) complexes. Na+ and Na adsorbed preferably on R7 and R6 positions of boron nanocage (B40), respectively, where the interaction of Na+ is stronger in comparison to Na atom. The change in Gibbs free energy (cell potential) values of R7-B40 and R6-B40 complexes (of bare case) are −11.21 kcal mol−1 (0.49 V) and −8.92 kcal mol−1 (0.39 V), respectively. For further improvement of change in ΔG and Vcell values, halides are encapsulated (A = F-, Cl- and Br-) into boron nanocage. The Vcell of Na-ion batteries for R7-A@B40 and R6-A@ B40 (A = F-, Cl- and Br-) increases up to 3.594 V and 3.492 V, respectively. These results illustrate that the electrochemical properties of A@B40 nanocage explicitly depend on the nature of alkali metals and their respective halide ions.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{D0NJ02291H,

title = {Superhalogen doping: a new and effective approach to design materials with excellent static and dynamic NLO responses},

author = {Hasnain Sajid and Faizan Ullah and Muhammad Yar and Khurshid Ayub and Tariq Mahmood},

url = {http://dx.doi.org/10.1039/D0NJ02291H},

doi = {10.1039/D0NJ02291H},

year  = {2020},

date = {2020-08-28},

urldate = {2020-01-01},

journal = {New Journal of Chemistry},

volume = {44},

issue = {38},

pages = {16358-16369},

publisher = {The Royal Society of Chemistry},

abstract = {Excess electron generation through doping with alkali and superalkali metals is well known to enhance NLO responses. On the contrary, superhalogen doping is an unexplored dimension. Herein, we report the first ever examples where superhalogen doping alone is introduced as a new and effective approach to impart large NLO responses. Density functional theory (DFT) calculations illustrate that superhalogen (BeF3 and BeCl3)-doped cyclic oligofurans (nCF) possess exceptionally high NLO responses (first hyperpolarizability (β0), hyper-Rayleigh scattering coefficient (βHRS), electro-optical Pockels effect (EOPE), second harmonic generation (SHG), and nonlinear refractive index (n2)), which are not trivial for organic compounds. Upon doping with superhalogens, the first hyperpolarizability (β0) of nCF increases to 3 × 105 a.u. in the BeF3@6CF complex, whereas the β0 values of the BeF3@5CF, BeCl3@5CF and BeCl3@6CF complexes are 6 × 104, 3 × 104 and 4 × 104 a.u., respectively. An enormously large third order nonlinear optical response coefficient with an electric field-induced second harmonic generation (ESHG) value of 2.1 × 109 a.u. is observed for the BeCl3@6CF complex. The remarkable NLO responses of the superhalogen-doped cyclic oligofuran complexes are due to the electron withdrawing nature of the halogen atoms, which are responsible for withdrawing electrons from the oxygen atoms of nCF to create poles. The significant hyperpolarizability (β0) of the BeF3@6CF complex is due to the most electronegative nature of fluorine. Furthermore, these results are rationalized through a two-level model. Bvec values are calculated for these complexes because they give more meaningful numbers from an experimental point of view. The stability of the complexes is judged through interaction energies, whereas electronic properties are calculated by chemical reactivity descriptors, the HOMO–LUMO gaps (Eg) and NBO charge transfer analysis. TD-DFT calculations reveal that the maximum absorbance for the BeF3@6CF complex is shifted to the longest wavelength.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{D0NJ01670E,

title = {Remarkable second and third order nonlinear optical properties of organometallic C6Li6–M3O electrides},

author = {Faizan Ullah and Khurshid Ayub and Tariq Mahmood},

url = {http://dx.doi.org/10.1039/D0NJ01670E},

doi = {10.1039/D0NJ01670E},

year  = {2020},

date = {2020-05-26},

urldate = {2020-01-01},

journal = {New Journal of Chemistry},

volume = {44},

issue = {23},

pages = {9822-9829},

publisher = {The Royal Society of Chemistry},

abstract = {Electrides are excess electron compounds with excellent nonlinear optical properties. Herein we report the geometric, electronic, and nonlinear optical properties of C6Li6–M3O electrides. These electrides are designed by doping superalkalis (Li3O, Na3O, and K3O) on hexalithiobenzene (C6Li6). Density functional theory results reveal that charge transfer occurs from M3O to hexalithiobenzene (C6Li6). Ab initio molecular dynamics (AIMD) simulations at room temperature reveal that these complexes are quite stable thermodynamically. These electrides possess lower HOMO–LUMO energy gaps and crucial excitation energies than pristine C6Li6. The NLO response of the designed electrides is studied through first hyperpolarizability (βtot), second hyperpolarizability (γtot), frequency-dependent second harmonic generation (SHG), the electro-optic Pockels effect (EOPE), electric field-induced second harmonic generation (ESHG), the electro-optic Kerr effect (EOKO), hyper-Rayleigh scattering coefficient (βHRS) and nonlinear refractive index (n2). A remarkably high frequency induced dc-Kerr effect (up to 3.0 × 1016 a.u.) and ESHG (up to 2.2 × 1015 a.u.) are computed for the designed electrides. Moreover, these electrides also exhibit an enormously high quadratic nonlinear refractive index (up to 2.6 × 10−6 a.u.). This work provides new insights for designing stable organometallic electrides (C6Li6–M3O) with enhanced NLO response.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{ULLAH2020163792,

title = {Design of novel inorganic alkaline earth metal doped aluminum nitride complexes (AEM@Al12N12) with high chemical stability, improved electronic properties and large nonlinear optical response},

author = {Faizan Ullah and Naveen Kosar and Asghar Ali and Maria and Tariq Mahmood and Khurshid Ayub},

url = {https://www.sciencedirect.com/science/article/pii/S0030402619316900},

doi = {https://doi.org/10.1016/j.ijleo.2019.163792},

issn = {0030-4026},

year  = {2020},

date = {2020-03-31},

urldate = {2020-01-01},

journal = {Optik},

volume = {207},

pages = {163792},

abstract = {Aluminum nitride nanocages (Al12N12) doped with alkaline earth metals (Be, Mg, and Ca) are theoretically designed and their geometrical structures, electronic properties, and nonlinear optical responses are explored by using density functional theory (DFT) calculations. The results revealed that the doped complexes are thermodynamically quite stable, and alkaline earth metals effectively narrow the highest occupied molecular orbital (HOMO)–lowest unoccupied molecular orbital (LUMO) energy gaps (EH-L) of the resultant complexes. More importantly, the adsorption of alkaline earth metal significantly increased the first hyperpolarizability (βo) values from 0 au of the pristine aluminum nitride nanocage up to 7769 au for the doped complexes. This study successfully demonstrates that the doping of alkaline earth metal on aluminum nitride nanocage is an effective approach to enhance electronic properties and NLO response of the system. In future these complexes can act as promising candidates to be used as high-performance nonlinear optical (NLO) materials for optoelectronic devices.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{SAJID2020107569,

title = {Cyclic versus straight chain oligofuran as sensor: A detailed DFT study},

author = {Hasnain Sajid and Faizan Ullah and Khurshid Ayub and Tariq Mahmood},

url = {https://www.sciencedirect.com/science/article/pii/S1093326319308794},

doi = {https://doi.org/10.1016/j.jmgm.2020.107569},

issn = {1093-3263},

year  = {2020},

date = {2020-02-28},

urldate = {2020-01-01},

journal = {Journal of Molecular Graphics and Modelling},

volume = {97},

pages = {107569},

abstract = {This study presents a novel approach for exploring the sensitivity and selectivity of cyclic oligofuran (5/6/7CF) toward gaseous analytes and their comparison with straight chain analogues (5/6/7SF). The work is not only vital to understand the superior sensitivity but also for rational design of new sensors based on cyclic ring structures of oligofuran. Interaction of cyclic and straight chain oligofuran with NH3, CO, CO2, N2H4, HCN, H2O2, H2S, CH4, CH3OH, SO2, SO3 and H2O analytes is studied via DFT calculation at B3LYP-D3/6–31++G (d, p) level of theory. The sensitivity and selectivity are illustrated by the thermodynamic parameters (Ebind, SAPT0 energies, NCI analysis), electronic properties (H-L gap, percentage of average energy gap, CHELPG charge transfer, DOS spectra), and UV–Vis analysis. All these properties are simulated at B3LYP/6-31G (d) level of theory while UV–Vis is calculated at TD-DFT method. Cyclic oligofurans have high binding energies with analytes compared to 5/6/7SF which corresponds to higher sensitivity of 5/6/7CF. Furthermore, the cyclization of oligofuran significantly improves the sensitivity and selectivity of the system. Alteration in electronic properties of 5/6/7CF and 5/6/7SF is remarkably high upon complexation with SO2 and SO3. Further the stability of rings (5, 6 and 7 membered cyclic oligofurans) and their SO3 complexes is also confirmed by molecular dynamics calculations. The findings of the work clearly suggest that the cyclic geometry enhances not only sensitivity but also selectivity of conducting polymers (oligofuran).},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{ULLAH2020113906,

title = {Alkaline earth metal decorated phosphide nanoclusters for potential applications as high performance NLO materials; A first principle study},

author = {Faizan Ullah and Naveen Kosar and Asghar Ali and Maria and Tariq Mahmood and Khurshid Ayub},

url = {https://www.sciencedirect.com/science/article/pii/S1386947719315085},

doi = {https://doi.org/10.1016/j.physe.2019.113906},

issn = {1386-9477},

year  = {2019},

date = {2019-12-28},

urldate = {2020-01-01},

journal = {Physica E: Low-dimensional Systems and Nanostructures},

volume = {118},

pages = {113906},

abstract = {With the aid of DFT calculations, novel inorganic complexes of group III phosphide (XY)12 (X = Al, B and Y = P) nanoclusters are theoretically designed and explored through exohedral doping with alkaline earth metals (Be, Mg, and Ca). The HOMO-LUMO gaps of the proposed novel inorganic complexes are narrowed significantly due to the increase in the energies of HOMOs. The results show that doping of alkaline earth metal over phosphide nanocluster causes shifting of excess electrons from the metal atom towards the nanocluster and breaks the centrosymmetry of the nanocluster. The doping profoundly increases the NLO response of the complexes. The first hyperpolarizabilities (βo) up to 7.8 × 104 au are calculated for the complexes as compared to the zero βo value of the pristine nanocage. These interesting results will attract more research interests in alkaline earth metal doped inorganic fullerenes complexes for the potential use in novel opto-electronic and high performance NLO materials and further the experimental research.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{ULLAH2020105855,

title = {Design of novel superalkali doped silicon carbide nanocages with giant nonlinear optical response},

author = {Faizan Ullah and Naveen Kosar and Muhammad Nadeem Arshad and Mazhar Amjad Gilani and Khurshid Ayub and Tariq Mahmood},

url = {https://www.sciencedirect.com/science/article/pii/S0030399219310102},

doi = {https://doi.org/10.1016/j.optlastec.2019.105855},

issn = {0030-3992},

year  = {2019},

date = {2019-09-27},

urldate = {2020-01-01},

journal = {Optics & Laser Technology},

volume = {122},

pages = {105855},

abstract = {In this study, the electronic and nonlinear optical (NLO) properties of a novel class of superalkalis (Li2F, Li3O and Li4N) doped silicon carbide (Si12C12) nanocages are investigated by using density functional theory (DFT) calculations. Computational results reveal that these complexes are quite stable and superalkalis prefer Sitop position of the nanocage energetically to be chemisorbed. The doping of superalkalis effectively reduced the HOMO–LUMO energy gap and transformed Si12C12 nanocage from insulator to n-type semiconductor. More interestingly, these complexes exhibited significantly large first hyperpolarizabilities (βo) in the range of 2141–19864 au. This remarkable increase in first hyperpolarizability (βo) values is due to small transition energies ΔE, which comes from the corresponding charge transfer from superalkali to the nanocage. The NLO response of the superalkali-doped Si12C12 nanocage was much better to those of their alkali-metal-doped analogs. Moreover, frequency dependent hyperpolarizability calculations are performed in the range of 400–1600 nm including 532 and 1064 nm for commonly used lasers. The TD-DFT analysis reveals that these complexes possess enough transparency in the UV region which is required besides large NLO response for practical applications in the field of opto-electronics. This study will provide new insights for designing of novel NLO materials having useful applications in all-optical switching, wavelength conversion and harmonic generation.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{ULLAH20191118,

title = {Superalkalis as a source of diffuse excess electrons in newly designed inorganic electrides with remarkable nonlinear response and deep ultraviolet transparency: A DFT study},

author = {Faizan Ullah and Naveen Kosar and Khurshid Ayub and Tariq Mahmood},

url = {https://www.sciencedirect.com/science/article/pii/S0169433219310347},

doi = {https://doi.org/10.1016/j.apsusc.2019.04.042},

issn = {0169-4332},

year  = {2019},

date = {2019-04-11},

urldate = {2019-01-01},

journal = {Applied Surface Science},

volume = {483},

pages = {1118-1128},

abstract = {Recently, significant progress is observed in the design and synthesis of nonlinear optical materials due to their optoelectronic and biomedical applications. In this report, a series of inorganic electrides (Li2F@Al12P12, Li3O@Al12P12 and Li4N@Al12P12) are designed by doping of Al12P12 nanocluster with superalkalis (Li2F, Li3O and Li4N) and studied through density functional theory (DFT) for their geometrical, electronic and nonlinear optical properties. Computational results indicated that these superalkalis doped complexes possess high stability and low HOMO-LUMO gaps. Interaction energies reveal that adsorption of Li4N on Altop site of Al12P12 results in highly stable structure (isomer J), where superalkali is strongly chemisorbed on the nanocage (Eint. = −105.13 kcal mol−1). Moreover, the lowest HOMO-LUMO gap is also observed for J isomer of Li4N@Al12P12 (0.44 eV), compared to 0.94 eV for alkali metal doped Al12P12 nanocage and 3.36 eV for pure nanocage. Doping of superalkali on aluminum phosphide nanocage can bring considerable increase in first hyperpolarizabilities (βo) response of the nanocage along with deep ultraviolet transparency. The first hyperpolarizability (βo) for isomer J of Li4N@Al12P12 is 6.25 × 104 au. This study may provide an effective strategy to design high performance NLO materials from stable inorganic electrides.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{C9NJ00225A,

title = {Theoretical study on a boron phosphide nanocage doped with superalkalis: novel electrides having significant nonlinear optical response},

author = {Faizan Ullah and Naveen Kosar and Khurshid Ayub and Mazhar Amjad Gilani and Tariq Mahmood},

url = {http://dx.doi.org/10.1039/C9NJ00225A},

doi = {10.1039/C9NJ00225A},

year  = {2019},

date = {2019-03-11},

urldate = {2019-01-01},

journal = {New Journal of Chemistry},

volume = {43},

issue = {15},

pages = {5727-5736},

publisher = {The Royal Society of Chemistry},

abstract = {Three series of compounds Li2F@B12P12, Li3O@B12P12 and Li4N@B12P12 are theoretically designed and investigated for their nonlinear optical response using density functional theory (DFT). Computational results reveal that isomers VIII and X are inorganic electrides whereas the others are excess electron systems. Interaction energies reveal that these systems are quite stable and superalkalis are chemisorbed on the nanocage. Doping of a B12P12 nanocage with superalkali brings a considerable increase in the first hyperpolarizability response of the system. The highest first hyperpolarizability (β0 = 3.48 × 105 a.u.) along with good ultraviolet transparency is observed for isomer III of Li2F@B12P12. Moreover, all three series of compounds are systemically studied for the effect of different superalkalis and different doping positions on the nonlinear optical response. This study will be advantageous for promoting the potential applications of the fullerene-like superalkali doped B12P12 nanostructures in new types of electronic nanodevices and high-performance nonlinear optical materials with good ultraviolet transparency.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}