Department of Chemistry
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Item Design of Novel Alkali Metals (Li, Na, K) Doped [6] Cycloparaphenylenes with High Nonlinear Optical Response(Library Information Services COMSATS University Islamabad Lahore Campus, 2021-02-26) Ruqiya Rasul; SP20/R06/011; Dr. Mazhar Amjad Gilani; LHR TP 7565Nonlinear optical (NLO) materials have gained tremendous attention because of their vast applications in different fields such as optoelectronics, telecommunication and data storage etc. In this work, geometric, electronic, linear and nonlinear optical properties of alkali metals (Li, Na and K) doped cyclic organic systems i.e., [6] cycloparaphenylene ([6]CPP) and methylene bridged [6] cycloparaphenylene (MB[6]CPP) are investigated via density functional theory (DFT). The diffuse excess electrons generated by alkali metals have significantly tuned their electro-optical properties. The alkali metals doped CPP based complexes have exhibited a large thermodynamic stability up to -32.1 kcal/mol. Moreover, reduction in HOMO-LUMO (H-L) energy gap has been observed up to 2.92 eV because of the generation of new HOMO which is further confirmed by density of state (DOS) analysis. The NBO analysis has revealed the charge transfer from metals to the CPPs. In addition, NCI and QTAIM analyses have exploited the nature of intramolecular interactions. Doping of alkali metal atoms significantly has increased the first hyperpolarizability (βₒ) of all the complexes. The K@r6-[6]CPP has exhibited the highest hyperpolarizability value of 1.10 x 107 au. Moreover, the absorption spectra have revealed the bathochromic shift for the alkali metals doped complexes. Furthermore, the frequency dependent first hyperpolarizability calculations have been done for M@r6 doped [6]CPP and MB[6]CPP at two routinely used frequencies (532 nm and 1064 nm). The results have shown that the highest response of both SHG (2.25 × 107 au) and EOPE (2.81 × 106 au) are obtained for K@r6-[6]CPP at 1064 nm. These fascinating results will be helpful to utilize the designed [6]CPP and MB[6]CPP based complexes for the generation of advanced optoelectronic devices and high performance NLO materials.Item Covalent Organic Framework Supported Single Atom Catalyst for Hydrogen Evolution Reaction: A Theoretical Investigation(Library Information Services COMSATS University Islamabad Lahore Campus, 2021-02-26) Maria Younas; SP20/R06/025; Dr. Mazhar Amjad Gilani; LHR TP 7579Global environmental considerations are being raised as a result of excessive fossil fuel consumption and excessive carbon dioxide (CO2) emission. Regrettably, fossil fuel reserves are decreasing, and energy generation from them is unsustainable, non-renewable, and unaffordable. Due to these concerns, there is an imperative demand for sustainable and eco-friendly energy conversion electrochemical systems. Hydrogen (H2) is ubiquitously regarded as a future sustainable energy source and an attractive alternative to conventional fossil fuels. Production of hydrogen must be sustainable in order for a hydrogen economy to thrive in the future. Water electrolysis powered by renewable resources is being considered as a sustainable approach to produce hydrogen. In attempt to implement the process of water splitting efficiently, cost-effective, and non-precious metal based electrocatalysts for hydrogen evolution reaction (HER) are required. The development of effective single-atom catalysts (SACs) for electrochemical water splitting is a viable technique. High energy barrier of the HER and a catalyst with low stability continue to pose difficulties for the entire process of water splitting. To address this issue, electrocatalysts with single metal atoms supported on a covalent organic framework (TM@COF SACs) have been proposed for HER. The catalytic performance of these catalysts for HER is determined by the change in the Gibbs free energy of adsorbed atomic hydrogen (ΔGH*) on the catalyst's surface. Density functional theory (DFT) findings suggest that the Zn single atom doped on the surface of the covalent organic framework has a significant impact on the HER performance. This study paves the way for the development and use of highly efficient, stable, and non-precious single atom HER catalysts.Item Theoretical Design of Alkali and Alkaline Earth Metals Doped Cubanes (C8H8) as Novel Nonlinear Optical Materials(Library Information Services COMSATS University Islamabad Lahore Campus, 2021-02-25) Javaria Naeem; SP20/R06/013; Dr. Mazhar Amjad Gilani; LHR TP 7567Novel organic materials have spark the attention of many scientists to design the high performance NLO materials. In the current study, the effect of alkali and alkaline earth metals doped cubanes have been studied by using density functional theory. The strong influence of doped metal atoms on structural, electronic and nonlinear optical prosperities have been investigated. The results have revealed thermodynamic stability of the doped complexes. The HOMO-LUMO energy gap is reduced upto 4.43 eV. Density of state analysis confirmed the formation of new highest occupied molecular orbital that contributes in the reduction of energy gap. The NBO analysis is performed to evaluate the charge transfer between metal atoms and the cubane ring. The NCI and QTAIM studies also validated the nature of the intramolecular interaction. Doping of metal atoms significantly boosts the hyperpolarizability of the complexes. The first hyperpolarizability (βₒ) of 3.01×104 au is observed for K@Cubane. Moreover, second hyperpolarizability (γtot), second harmonic generation (SHG), electro-optic Pockel’s effect (EOPE), electric field-induced second harmonic generation (EFISHG), electro-optic Kerr effect (EOKE), hyper-Rayleigh scattering coefficient (βHRS) and nonlinear refractive indices (n2) are also calculated for the designed complexes. The highest dc-Kerr of 2.03 × 1011 au and EFISHG of 2.06 × 1012 au are observed at ω= 0.0856 au along with large refractive index (1.15 × 10-5 au ). These remarkable findings offer new perspectives for designing new materials for their future applications in optoelectronics.