Quantum Chemical Designing of Novel Organic Non-Linear Optical Compounds

Mahmood, Asif,Abdullah, Muhammad Imran,Nazar, Muhammad Faizan Korean Chemical Society 2014 Bulletin of the Korean Chemical Society Vol.35 No.5

In the present study, ten metal free non-linear optical (NLO) compounds have been designed. These compounds have designed by structural modification of (2-cyano-5-(4-(phenyl(4-vinylphenyl)amino)phenyl) penta-2,4-dienoic acid (TC4). Density functional theory was used for structure optimization and determination of photo-physical properties. These compounds contain triphenylamine as electron-donor and cyanoacrylic acid as acceptor. Five ${\pi}$-spacers are used to connect the donor and acceptor. Two auxiliary donors are also used to assist the donor. Results of this study indicate that stronger electron-donating auxiliary groups and longer ${\pi}$-conjugation enhance NLO response. Major absorption peaks of all systems were in the visible region. These absorption peaks are associated with the ${\pi}-{\pi}^*$ transitions of the entire molecule. From calculations it is clear that all system will be good NLO material. The present calculations will provide new ways for experimentalists to synthesize high-performance NLO material.

Intermediate-temperature solid oxide electrolysis cell with bi-layered electrolyte structure

( Asif Mahmood ),( Saira Bano ),( Ji Haeng Yu ),이규호 한국공업화학회 2014 한국공업화학회 연구논문 초록집 Vol.2014 No.1

A Ni-GDC supported solid oxide electrolysis cell with bi-layered ScSZ/GDC electrolyte and LSCF oxygen electrode was developed for intermediate-temperature steam and CO₂ electrolysis. The OCV of bi-layered electrolyte cell was significantly improved as compared to cell with single-layered GDC electrolyte structure, but at the cost of an increase in electrolyte resistance (R_e) and electrode polarization resistance (R_p). The formation of (Zr, Ce)O₂ solid solution at the interfaces of ScSZ interlayer during co-sintering caused the increase in Re and Rp. Unlike single-layered GDC electrolyte cell, the bi-layered electrolyte cell did not show a noticeable internal electrical shorting under SOEC conditions and thus exhibited a good electrolysis performance. However, the cell stability test revealed a performance decay at the rate of 5 mV/h, when operated in co-electrolysis (H₂:steam:CO₂ = 20:40:40 vol.%) under -0.5A/㎠ at 650°C over 100h.

Reversible Solid Oxide Fuel Cell for Synthetic Fuel Production from Steam and CO2

( Asif Mahmood ),( Saira Bano ),( Ji Haeng Yu ),이규호 한국공업화학회 2013 한국공업화학회 연구논문 초록집 Vol.2013 No.1

Computational Designing of Triphenylamine Dyes with Broad and Red-shifted Absorption Spectra for Dye-sensitized Solar Cells using Multi-Thiophene Rings in π-Spacer

Asif Mahmood,Mudassir HussainTahir,Ahmad Irfan,Bilal Khalid,Abdullah G. Al-Sehemi 대한화학회 2015 Bulletin of the Korean Chemical Society Vol.36 No.11

In this paper, we present the design of five new derivatives of triphenylamine dyes with variable thiophene rings (0–5) and shed light on their electrooptical and charge-injection properties. Computational techniques are used to study the effect of the thiophene moieties on the properties of interest, i.e., how the number of thiophene rings in π-conjugated systems influence the absorption spectra and electron injection of the dyes. The results show that the absorption spectra gradually became broad and red-shifted (384–542 nm) with the number of thiophene units. The effect of thiophene units on the performance of sensitizers in dye-sensitized solar cells is also determined. During theoretical examination, the electron injection efficiency (Φinject) and light harvesting efficiency (LHE) are determined. Results indicate that the selection of appropriate lengths of conjugated bridges in the dye sensitizer is very important in designing high-efficiency dyes.

Quantum Chemical Designing of Novel Organic Non-Linear Optical Compounds

Asif Mahmood,Muhammad Imran Abdullah,Muhammad Faizan Nazar 대한화학회 2014 Bulletin of the Korean Chemical Society Vol.35 No.5

In the present study, ten metal free non-linear optical (NLO) compounds have been designed. These compounds have designed by structural modification of (2-cyano-5-(4-(phenyl(4-vinylphenyl)amino)phenyl) penta-2,4-dienoic acid (TC4). Density functional theory was used for structure optimization and determination of photo-physical properties. These compounds contain triphenylamine as electron-donor and cyanoacrylic acid as acceptor. Five π-spacers are used to connect the donor and acceptor. Two auxiliary donors are also used to assist the donor. Results of this study indicate that stronger electron-donating auxiliary groups and longer π- conjugation enhance NLO response. Major absorption peaks of all systems were in the visible region. These absorption peaks are associated with the π-π* transitions of the entire molecule. From calculations it is clear that all system will be good NLO material. The present calculations will provide new ways for experimentalists to synthesize high-performance NLO material.

The study of electronic, elastic, magnetic and optical response of Zn1-xTixY (Y=S, Se) through mBJ potential

Q. Mahmood,M. Hassan,M.A. Faridi,B. Sabir,G. Murtaza,Asif Mahmood 한국물리학회 2016 Current Applied Physics Vol.16 No.5

To explore the structural, electronic, magnetic and optical properties of Zn1-xTixY (Y=S, Se) alloys, in the composition range 0 ≤ x ≤ 1, we have applied full-potential linearized augmented plane wave plus local orbital (FP-LAPW + lo) scheme, which is based on the density functional theory (DFT). Structural optimizations have been done in ferromagnetic (FM) and antiferromagnetic (AFM) phase by using Wu eCohen generalized gradient approximation (WC-GGA), whereas recently developed modified Becke and Johnson (mBJ) potential was employed to study electronic and optical properties. The lower value of ground state energy and negative enthalpy of formation confirm stability in the FM phase. Due to the spin polarization of electrons in the Ti-d orbital, origin of half-metallic ferromagnetism has been expressed by the calculated band structures, electronic density of states (DOS) and magnetic moments. We also have calculated the exchange splitting energy Dx (d), crystal field energy (DEcrystal = Et2g Eeg) and exchange constants (N0a and N0b). The negative value of exchange constant (N0b) and large splitting of 3d-states of Ti show that the down spin potential is more effective than up spin. Finally, the results of optical parameters such as complex dielectric constant ε (u), refractive index n (u), normal incident reflectivity R (u), absorption coefficient ɑ (u), optical conductivity s (u) and optical loss factor L (u) are discussed in the energy range 0e14 eV. Moreover, we have verified the Penn's model by showing the inverse relation between the static dielectric constant and the optical band gap. The direct relation between static dielectric constant and static refractive index has been observed by increasing the composition of Ti. The calculated parameters provide valuable theoretical information for optical and spintronics device applications.

Nature of Complex Network of Dengue Epidemic as a Scale-Free Network

Hafiz Abid Mahmood Malik,Faiza Abid,Nadeem Mahmood,Mohamed Ridza Wahiddin,Asif Malik 대한의료정보학회 2019 Healthcare Informatics Research Vol.25 No.3

Objectives: Dengue epidemic is a dynamic and complex phenomenon that has gained considerable attention due to its injurious effects. The focus of this study is to statically analyze the nature of the dengue epidemic network in terms of whether it follows the features of a scale-free network or a random network. Methods: A multifarious network of Aedes aegypti is addressed keeping the viewpoint of a complex system and modelled as a network. The dengue network has been transformed into a one-mode network from a two-mode network by utilizing projection methods. Furthermore, three network features have been analyzed, the power-law, clustering coefficient, and network visualization. In addition, five methods have been applied to calculate the global clustering coefficient. Results: It has been observed that dengue epidemic follows a powerlaw, with the value of its exponent γ = –2.1. The value of the clustering coefficient is high for dengue cases, as weight of links. The minimum method showed the highest value among the methods used to calculate the coefficient. Network visualization showed the main areas. Moreover, the dengue situation did not remain the same throughout the observed period. Conclusions: The results showed that the network topology exhibits the features of a scale-free network instead of a random network. Focal hubs are highlighted and the critical period is found. Outcomes are important for the researchers, health officials, and policy makers who deal with arbovirus epidemic diseases. Zika virus and Chikungunya virus can also be modelled and analyzed in this manner.

Enhancement of catalytic activity of Au/TiO2 by thermal and plasma treatment

우성일,Asif Mahmood 한국화학공학회 2013 Korean Journal of Chemical Engineering Vol.30 No.10

A significant enhancement in the catalytic activity of Au/TiO2 in CO oxidation and preferential oxidation reaction by creating the active sites on the catalyst surface by thermal treatment as well as by producing small gold particles by plasma treatment has been studied. Au/TiO2 catalyst (Au (1 wt%) supported on TiO2) was prepared by conventional deposition-precipitation method with NaOH (DP NaOH) followed by washing, drying and calcination in air at 400 oC for 4 h. Thermal treatment of Au/TiO2 was carried out at 550 oC under 0.05 mTorr. A small amount of Au/TiO2 catalyst was taken from the untreated and thermally treated Au/TiO2 and both kinds of catalysts were treated with plasma sputtering at room temperature. The activity of the catalysts has been examined in the reaction of CO oxidation and preferential oxidation (PROX) at 25-250 oC. Thermally treated Au/TiO2 showed better catalytic activity as compared to the untreated catalyst. There is also an additional enhancement in the catalytic activity due to plasma sputtering on the both kinds of catalysts. Thermally treated Au/TiO2 followed by plasma sputtering Au/TiO2 showed higher conversion rates for CO oxidation reaction compared with untreated, thermally treated and plasma sputtered Au/TiO2 catalysts. It may be concluded that the enhancement of catalytic activity of thermally treated Au/TiO2 followed by plasma sputtering is owing to the generation of active sites such as oxygen vacancies/defects in TiO2 support using thermal treatment as well as by producing small gold particles using plasma treatment.

Detection of BCR/ABL Fusion Gene by Hematological and Cytogenetical Analysis in Chronic Myeloid Leukemia Patients in Quetta, Pakistan

Tahira, Bibi,Asif, Muhammad,Khan, Samiullah,Hussain, Abrar,Shahwani, Muhammad Naeem,Malik, Arif,Inayatullah, Syed,Iqbal, Zafar,Rasool, Mahmood Asian Pacific Journal of Cancer Prevention 2015 Asian Pacific journal of cancer prevention Vol.16 No.9

Background: Chronic myeloid leukemia (CML) is a myeloproliferative disorder of pluripotent stem cells, caused by reciprocal translocation between the long arms of chromosomes 9 and 22, t(9;22)(q34;q11), known as the Philadelphia chromosome. Materials and Methods: A total of 51 CML patients were recruited in this study. Complete blood counts of all CML patients were performed to find out their total leukocytes, hemoglobin and platelets. FISH was performed for the detection of BCR-ABL fusion and cryptogenic tests using bone marrow samples were performed for the conformation of Ph (9;22)(q34;q11) and variant translocation mechanisms. Results: In cytogenetic analysis we observed that out of 51 CML patients 40 (88.9%) were Ph positive and 4 (8.88%) had Ph negative chromosomes. Mean values of WBC 134.5 $10^3/{\mu}l$, hemoglobin 10.44 mg/dl, and platelets 288.6 $10^3/{\mu}l$ were observed in this study. Conclusions: In this study, Ph positive translocation between chromosome (9:22)(q34;q11) were observed in 40 (88.9%) CML patients.

Milling Effects of $Y_2BaCuO_5$ Precursor Powder with $CeO_2$ Addition on the Critical Current Density of Liquid Infiltration Growth Processed $YBa_2Cu_3O_{7-y}$ Bulk Superconductors

아시프 마흐무드,전병혁,김찬중,Asif, Mahmood,Jun, Byung-Hyuk,Kim, Chan-Joong The Korean Superconductivity Society 2010 Progress in superconductivity Vol.12 No.1

The milling effects of a precursor $Y_2BaCuO_5$ (Y211) powder having 1 wt.% $CeO_2$ on the microstructure and critical current density ($J_c$) of liquid infiltration growth (LIG) processed $YBa_2Cu_3O_{7-y}$ (Y-123) bulk superconductors were investigated. The microstructure analysis revealed that the Y211 size in the final Y-123 products decreased with increasing the milling time and a relatively high density and uniform distribution of Y211 inclusions were observed in the sample prepared using 8 h milled powder. However, the unexpected Y211 particles coarsening was observed from the 4 h milled sample which was further increased for 10 h milled sample. Critical current density ($J_c$) of the LIG processed Y-123 bulk superconductors was found to be dependent on the milling time of the Y211 precursor powder. The $J_c$ increased with the increase of milling time and reached up to a maximum at 8 h in the self field while 10 h milled sample showed lower $J_c$ at the same field which might be due to the exaggerated growth and non-uniform distribution of Y211 particles.