Designing of banana shaped chromophores via molecular engineering of terminal groups to probe photovoltaic behavior of organic solar cell materials.

To meet the rising requirement of photovoltaic compounds for modernized hi-tech purpose, we designed six new molecules (DTPD1-DTPD6) from banana shaped small fullerene free chromophore (DTPR) by structural tailoring at terminal acceptors. Frontier molecular orbitals (FMOs), density of states (DOS), open circuit voltage (Voc), transition density matrix (TDM) analysis, optical properties, reorganization energy value of hole and electron were determined utilizing density function theory (DFT) and time-dependent density function theory (TD-DFT) approaches, to analyze photovoltaic properties of said compounds. Band gap contraction (∆E = 2.717-2.167 eV) accompanied by larger bathochromic shift (λmax = 585.490-709.693 nm) was observed in derivatives contrary to DTPR. The FMOs, DOS and TDMs investigations explored that central acceptor moiety played significant role for charge transformation. The minimum binding energy values for DTPD1-DTPD6 demonstrated the higher exciton dissociation rate with greater charge transferal rate than DTPR, which was further endorsed by TDM and DOS analyses. A comparable Voc (1.49-2.535 V) with respect to the HOMOPBDBT-LUMOacceptor for entitled compounds was investigated. In a nutshell, all the tailored chromophores can be considered as highly efficient compounds for promising OSCs with a good Voc response.

First theoretical probe for efficient enhancement of optical nonlinearity via structural modifications into phenylene based D-π-A configured molecules.

The design of nonlinear optical (NLO) materials using conjugated molecules via different techniques is reported in the literature to boost the use of these systems in NLO. Therefore, in the current study, designed phenylene based non-fullerene organic compounds with a D-π-A framework were selected for NLO investigation. The initial compound (PMD-1) was taken as a reference and its seven derivatives (PMDC2-PMDC8) were made by introducing different acceptor moieties into the chemical structure of PMD-1. To explain the NLO findings, frontier molecular orbital (FMO), transition density matrix (TDM), density of states (DOS), natural bond orbital (NBO) and UV-Vis study of the title compounds was executed by applying the PBE1PBE functional with the 6-311G(d,p) basis set. The descending order of band gaps (E gap) was reported as PMDC7 (2.656) > PMDC8 (2.485) > PMD-1 (2.131) > PMDC3 (2.103) > PMDC2 (2.079) > PMDC4 (2.065) > PMDC5 (2.059) > PMDC6 (2.004), in eV. Global reactivity parameters (GRPs) were associated with E gap values as PMDC6 with the lowest band gap showed less hardness (0.0368 E h) and high softness (13.5785 E h). The UV-Vis investigation revealed that the maximum λ max (739.542 nm) was exhibited by PMDC6 in dichloromethane (DCM) as compared to other derivatives. Additionally, natural bond orbital (NBO) based findings revealed that PMDC6 exhibited the highest stability value (34.98 kcal mol-1) because of prolonged hyper-conjugation. The dipole moment (µ), average linear polarizability 〈α〉, first hyperpolarizability (ß tot) and second hyperpolarizability (γ tot) were evaluated for the reference and its derivatives. Consequently, among the designed compounds, the highest ß tot (4.469 × 10-27 esu) and γ tot (5.600 × 10-32 esu) values were shown by PMDC6. Hence, it's concluded from said results that these structural modifications proved PMDC6 as the best second and third order NLO candidate for various applications like fiber optics, signal processing and data storage.

A comparative analysis of coronary adventitial T-lymphocytes--an autopsy study.

BACKGROUND: Recent clinical and histopathologic data suggests that inflammation plays a key role in coronary artery plaque instability and subsequent occlusive thrombosis. The intima has received much attention as a site of inflammation, while the adventitia has remained relatively unexplored. The aim of the present study was to investigate the frequency of inflammatory activity in the cap and shoulder region of unruptured, atherosclerotic lesions in coronary arteries and to correlate these findings with distribution of inflammatory cells in adventitia. METHODS: The study was carried out in Histopathology Department, Army Medical College, Rawalpindi and National University of Sciences & Technology (NUST), from August 2008 to July 2009. Sixty-seven autopsy cases performed at Military Hospital Rawalpindi, Pakistan were selected. The cases were divided into study group and control group. Case group (n = 35) included those where cause of death was ischemic heart disease. Those coronary arteries were taken as control (n = 32) where atherosclerotic changes were found by chance (death without history of ischemic heart disease). Plaques in each group were assessed by light microscopy and by immunohistochemistry. RESULTS: The ages of the deceased ranged from 38 to 49 years. Within study group, adventitial lymphocytes exhibited strong correlation with erosion, thrombus formation in culprit plaque (p = 0.001). No correlation was found between adventitial T-lymphocytes and erosion of plaque (p = 0.700) in control group. In 72% of culprit plaques moderate staining for T-lymphocytes was observed in adventitia as well as intima. In control group, most of the cases contained scattered cells. Few cases of stable plaques revealed lymphocytes as clusters, both in adventitia and in intima. CONCLUSION: Adventitial inflammation may play a pivotal role for atherosclerotic lesion histology and atheroma instability. With the help of these autopsy findings, we hope to be able to reduce the incidence of culprit plaques related to inflammatory reaction in patients of ischemic heart disease.

Diagnostic accuracy of fine needle aspiration of thyroid nodule versus biopsy in thyroid lesions.

BACKGROUND: FNA biopsy of thyroid is a rapid, minimally invasive, and cost effective first line procedure in the evaluation of thyroid nodule. This study was conducted to evaluate the cytological accuracy, sensitivity and specificity of fine needle aspiration (FNA) of solitary thyroid nodules in correlation with post-surgical histological findings. METHODS: This retrospective study was carried out at Department of Pathology, Abbottabad International Medical College, Abbottabad from January 2009 to December 2010. A total of 81 patients with clinically palpable solitary thyroid nodule were included in the study. Thyroid function tests were initially performed followed by FNA of thyroid nodules later operated and histopathological examination was conducted on the excised nodules. FNA diagnoses were correlated with the histological findings. The accuracy, sensitivity and specificity of the procedure were determined. RESULTS: Out of 81 cases, 5 (6.2%) were unsatisfactory and 76 cases were satisfactory for cytological evaluation. Cyto-histopathological correlation was carried out for these cases. The study showed a diagnostic accuracy of 93% with sensitivity and specificity rates of 75% and 96% respectively. Positive predictive value is 81% and negative predictive value is 95%. CONCLUSION: Fine needle aspiration (FNA) has evolved as an accurate and sensitive diagnostic tool for the initial screening of patients with thyroid nodules, and has reduced the need for unnecessary surgery.