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Papers by Shafqat Ullah
Pakistan journal of pharmaceutical sciences, 2017
The aim of the study was to investigate the effects of effects of storage and temperature on the ... more The aim of the study was to investigate the effects of effects of storage and temperature on the antioxidant potential, vitamin-C contents, total as well as selected individual phenolic acids and flavonoids of fresh aqueous leaves extract of Azadirachta Indica. The antioxidant activity of Azadirachta Indica leaves aqueous extract was determined by scavenging of DPPH free radical, while the phenolic compounds and vitamin-C contents by HPLC method. The analyses were carried out on crude extract of fresh leaves and after storage time of 1, 2 and 3 month at temperature of 20, 30 and 50°C. Storage for longer duration and rise in temperature caused decreasing the phenolic acids and vitamin C contents as well as antioxidant potential. Vitamin C contents were decreased up to 91% upon storage for 3 months at 50°C, while the anti-oxidant potential was decreased 29 %. The effect of storage time and temperature on individual phenolic acid and flavonoids were also remarkable, except ferulic acid...
A series of SrAl 2 O 4 : Eu 2+ , Dy 3+ long-afterglow (LAG) phosphors with varying concentration ... more A series of SrAl 2 O 4 : Eu 2+ , Dy 3+ long-afterglow (LAG) phosphors with varying concentration of Li + , Na + and K + , has been synthesized. The increased concentration of the three types of alkaline ions does not decrease the quantity of the total luminescent phases (SrAl 2 O 4 plus Sr 4 Al 14 O 25), but a different set of secondary phases has been evoluted for the K +-added series due to the failure of the incorporation of relatively large K + (1.38 Å) to the Sr 2+ (1.18 Å) site in the hosts, unlike the cases of smaller Li + (0.76 Å) and Na + (1.02 Å) ions. PL excitation, PL emission, and LAG luminescence, are decreased by all investigated alkaline ions, which would be due to the diminished incorporation of Eu 2+ and Dy 3+ activators into the luminescent hosts by the alkaline ions. For the cases of the Li + and Na +-added series, the incorporated Li + or Na + to the luminescent hosts would also limit the activation of Eu 2+ and charge trapping/detrapping of Dy 3+ to yield the diminished PL properties and LAG luminescence. The type of defect complex formed by the addition of Li + and Na + ions has been deduced and compared with that formed when no alkaline ion is added. * The starting composition in the current work (Sr 0.96 Al 1.96 O 4 : 0.04Eu, 0.04Dy) can also be regarded as 0.96(SrAl 2 O 4) + 0.02Al 2 O 3 + 0.04Eu 2 O 3 + 0.04Dy 2 O 3 + 0.3B 2 O 3 .
Pakistan journal of pharmaceutical sciences, 2017
The aim of the study was to investigate the effects of effects of storage and temperature on the ... more The aim of the study was to investigate the effects of effects of storage and temperature on the antioxidant potential, vitamin-C contents, total as well as selected individual phenolic acids and flavonoids of fresh aqueous leaves extract of Azadirachta Indica. The antioxidant activity of Azadirachta Indica leaves aqueous extract was determined by scavenging of DPPH free radical, while the phenolic compounds and vitamin-C contents by HPLC method. The analyses were carried out on crude extract of fresh leaves and after storage time of 1, 2 and 3 month at temperature of 20, 30 and 50°C. Storage for longer duration and rise in temperature caused decreasing the phenolic acids and vitamin C contents as well as antioxidant potential. Vitamin C contents were decreased up to 91% upon storage for 3 months at 50°C, while the anti-oxidant potential was decreased 29 %. The effect of storage time and temperature on individual phenolic acid and flavonoids were also remarkable, except ferulic acid...
A series of SrAl 2 O 4 : Eu 2+ , Dy 3+ long-afterglow (LAG) phosphors with varying concentration ... more A series of SrAl 2 O 4 : Eu 2+ , Dy 3+ long-afterglow (LAG) phosphors with varying concentration of Li + , Na + and K + , has been synthesized. The increased concentration of the three types of alkaline ions does not decrease the quantity of the total luminescent phases (SrAl 2 O 4 plus Sr 4 Al 14 O 25), but a different set of secondary phases has been evoluted for the K +-added series due to the failure of the incorporation of relatively large K + (1.38 Å) to the Sr 2+ (1.18 Å) site in the hosts, unlike the cases of smaller Li + (0.76 Å) and Na + (1.02 Å) ions. PL excitation, PL emission, and LAG luminescence, are decreased by all investigated alkaline ions, which would be due to the diminished incorporation of Eu 2+ and Dy 3+ activators into the luminescent hosts by the alkaline ions. For the cases of the Li + and Na +-added series, the incorporated Li + or Na + to the luminescent hosts would also limit the activation of Eu 2+ and charge trapping/detrapping of Dy 3+ to yield the diminished PL properties and LAG luminescence. The type of defect complex formed by the addition of Li + and Na + ions has been deduced and compared with that formed when no alkaline ion is added. * The starting composition in the current work (Sr 0.96 Al 1.96 O 4 : 0.04Eu, 0.04Dy) can also be regarded as 0.96(SrAl 2 O 4) + 0.02Al 2 O 3 + 0.04Eu 2 O 3 + 0.04Dy 2 O 3 + 0.3B 2 O 3 .