Department of Chemistry
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Item Designing Donor-Acceptor Small Molecules For Organic Solar Cells With Promising Photovoltaic Parameters(Library Information Services COMSATS University Islamabad Lahore Campus, 2021-02-23) Shahzaib Ijaz; SP19-R06-001; Dr. Sobia Tabassum; LHR TP 7340Cyclopentadithiophene (CPT) is one of the most efficient electron donating unit and has been reliably used in highly efficient optoelectronic applications because of its unique characteristics of excitation of electrons by fused thiophene ring derivatives, the rigidity and the high flatness of its structure. In order to meet the increasing demand of high-efficiency photovoltaic compounds in modern high-performance applications, we have designed and explored new CPT-based donor-acceptor-donor-acceptor-donor based materials with higher efficiency from d-CDT(PTTh2). Three novel isostructural D1-A-D2-A-D1 based low band gap small molecule donors (SMDs) having one-atom replacement (Flourine, Chlorine and Hydrogen) in acceptor unit of benzothiadiazole (BTZ) were designed and investigated by density functional theory (DFT) simulations. The designed molecules are 7,7'(7H-cyclopenta[1,2-b:3,4-b']dithiophene-2,5-diyl)bis(6fluoro4(5'hexyl[2,2’[2,2' bithiophen]-5yl)benzo[c][1,2,5]thiadiazole) (CPT1), its chlorine analogue 7,7'-(7H-cyclopenta[1,2-b:3,4-b']dithiophene-2,5-diyl)bis(6-chloro4-(5'-hexyl-[2,2'-bithiophen]-5yl)benzo[c][1,2,5]thiadiazole) (CPT2) and their hydrogen analogue 7,7'-(7H cyclopenta[1,2-b:3,4-b']dithiophene-2,5diyl)bis(4-(5'-hexyl-[2,2'bithiophen]-5 yl)benzo[c][1,2,5]thiadiazole) (CPT3). All are based on the strong electron rich unit CPT and electron withdrawing BTZ acceptors. The structures of designed compounds were optimized at DFT/B3LYP/6- 311 g(d,p). The new designed donors CPT1, CPT2, CPT3 showed superior absorption range found at the wavelengths of 715nm,674nm and 705nm respectively as compared to 667nm of reference molecule d-CDT(PTTh2) in chloroform solution. DFT calculations revealed that CPT1,CPT2 and CPT3 transfer their charges efficiently with band gaps 2.0 eV,2.21 eV and 2.1 eV respectively. The calculated open circuit voltages range from 0.55 eV to 0.70 eV, while CPT2 have a significantly higher open circuit voltage than the open circuit voltage of 0.62 of reference molecule d-CDT(PTTh2). Charge transfer mobilities of designed molecules are also superior than d-CDT(PTTh2) because of their lower reorganization energies ranging from 0.00114 to 0.038282 for electron and 0.11101 to 0.44505 for hole. This DFT investigation revealed that tuning of organic compounds can further enhance the efficiency of SMDs in bulk hetero-junction (BHJ) organic solar cells (OSC’s). DFT calculations showed that one atom substitution has a slight but notable effect on band gaps of frontier molecular orbital (FMOs) which affects the absorption ranges, reorganization energies, Voc, FF and PCE of SMDs in BHJ OSC. Our investigations suggest that the designed molecules can work as fine SMDs when coupled with PC71BM as an acceptor in BHJ OSC.Item A DFT Study of Dopamine Functionalized Borospherenes for Effective Cancer Treatment(Library Information Services COMSATS University Islamabad Lahore Campus, 2020-02-19) Iqra Karim; SP19-R06-003; Dr. Sobia Tabassum; LHR TP 6507Cancer has become one of the major threats to human life. Cancer therapies also bear the risk to health tissues. An effective approach to safe health cells is the integration of photothermal properties in the targeted chemotherapeutic system. In the present study, the targeted drug-carrying capacity of dopamine functionalized borospherene has been explored with the help of DFT. The results reveal that functionalization has a strong influence on geometrical, electronic, and thermodynamic properties of borospherene. The drug-loaded on functionalized borospherene has reduced the bandgap up to 2.104 eV. The reduction in band gap is fully supported by the density of states. The thermodynamic data confirms the exothermic and spontaneous nature of adsorption. NBO analysis confirms the charge transfer from drug and dopamine towards borospherene. Functionalization of dopamine extraordinarily increases the molecular descriptors parameters. The softness and electrophilicity index values increased for the drug-loaded on functionalized borospherene to 0.48 eV and 7.51 eV respectively. Similarly, the dipole moment also increases from 11.86 Debye to 21.94 Debye increasing the polarity. Moreover, the values of chemical hardness and chemical potential decrease from 1.45 eV to 1.05 eV and -3.71 eV to -3.97 eV respectively. This shows improved stability and reactivity of the functionalized borospherene than the drug load on pristine borospherene. All these are favorable drug delivery capacity of functionalized borospherene system. The SERS-Raman spectrum of functionalized borospherene shows more intense peaks at 1500-2000 cm- 1 and 3000-4000 cm-1 than the drug-loaded on pristine borospherene which has one intense peak at 1500-2000 cm-1. It means that functionalization improves the detection of the drug. Similarly, UV spectrum also shows that the maximum absorption increases from wavelength 501 nm to 581 after functionalization and a weak signal also appears at 703 nm.Item Computational Evaluation of Metal Doped Phosphorene-Nanosheets for Cancer Treatment(Library Information Services COMSATS University Islamabad Lahore Campus, 2020-02-19) Hira Karim; LHR TP 6508; Dr. Sobia Tabassum; LHR TP 6508Cancer is known as one of the leading causes of human mortality. The cancer treatments also damage the healthy tissue. So effective theranostic treatments are required for efficient cancer therapy and safety of healthy tissue. Phosphorene is a great material of interest to develop efficient targeted drug delivery system and imaging guided thermal therapy for cancer curing. Metal doping in a material is offered to tune its properties. In this work, effect of group II A metals on targeted delivery of anti-cancer drug, photoimaging (image guided cancer treatment) and photothermal treatment (thermal killing of cells by employing near infrared (NIR) light of doped phosphorene are evaluated via DFT method. The adsorption energies, quantum molecular properties, Atoms in Molecules (AIM) analysis, and Natural Bond Orbital (NBO) analysis of drug loaded pristine and doped phosphorene complexes were explored to understand the type of events in their interactions. The thermodynamic data confirms the exothermic and spontaneous nature of adsorption. The doped complexes showed better adsorption than pristine complex. The polarity was found to increase in doped complexes which is essential for driving in biological systems. Drug adsorption and doping have decreased the chemical potential and electrophilicity index while increased the softness of pristine phosphorene and doped phosphorene. The NBO data indicated the flow of charge from drug to nanosheet. Doping has made suitable the charge transfer and associated interaction. This interaction is strong in neutral pH. At acidic pH, in cancerous tissue environment drug will be protonated and will lose this interaction. These interactions were further investigated by Quantum Theory of Atoms in Molecules (QTAIM) analysis, revealing strong covalent interactions in all doped complexes except for one Mg-O bond in Mg-doped complex which owns strong electrostatic interactions. TD-DFT study showed lowering of band gap and shifting of λmax towards NIR region which is very useful for photothermal and image guided therapy. The Surface-Enhanced Raman Scattering (SERS) analysis revealed that doped systems effectively enhanced the Raman signals. All these properties supported the potential use of doped phosphorene complexes for photoimaging and photothermal killing of cancer cells.