Catalyst driven optical properties of the self-assembled ZnS nanostructures

In this paper, we present the effect of different catalysts (Mn, Au and Sn) on the room temperature photoluminescence and Raman spectra of VLS grown ZnS nanostructures. The catalysts found to self-dope the ZnS nanostructures during its growth were confirmed by XRD and XPS results. The extent of self-doping, which depended on the type and size of catalysts, was observed strongly to have affected the optical properties of ZnS nanostructures, particularly intrinsic defects like S and Zn vacancies. Intense broad bands in the visible due to intrinsic defects, namely Zn and S vacancies were observed, which were quite different for each catalyst as well as for the size of the catalyst. Au and Mn catalyzed ZnS nanostructures also showed creation of catalyst related defects, which were absent in the case of Sn. From the PL spectra, an estimation of the Zn and S vacancies was made for each type of catalyzed ZnS nanostructures. Surface optic (SO) phonon modes of the ZnS nanostructures were also observed to behave differently for the three catalysts. The dielectric continuum model was applied to determine the correlation length and variation in the surface potential modulations in these nanostructures. It was deduced from optical studies that the location of dopant in self-doped ZnS nanostructures strongly affected the luminescence properties. Finally it was concluded that self-doping using a suitable catalyst can be a simple and controllable way to dope ZnS nanostructures with tailored optical characteristics.

Silver disinfection of Pseudomonas aeruginosa and E. coli in rooftop harvested rainwater for potable purposes

Rainwater harvesting being an alternate source in water scarce areas is becoming a common practice. Catchment contact, however, deteriorates the quality of rainwater making it unfit for potable purposes. To improve the quality of harvested rainwater, silver was used as antimicrobial agent in this study. Rainwater samples were taken from underground storage tank of a rooftop rainwater harvesting system installed in one of the buildings at Seoul National University, Seoul, South Korea. The target microorganisms (MOs) were Pseudomonas aeruginosa and Escherichia coli which were measured by using plate count method and standard MPN method, respectively. The efficiency of silver disinfection was evaluated at concentrations, ranging from 0.01 to 0.1 mg/l; the safe limit approved by WHO. The experiments were performed for 168 h with different time intervals to evaluate the parameters including inactivation rate, residual effect of silver and re-growth in both MOs at lower (i.e. 0.01-0.04 mg/l) as well as the higher concentrations of silver (i.e. 0.08-0.1 mg/l). Results showed the re-growth in both MOs was only in the case of lower concentrations of silver. The possible reason of re-growth at these concentrations of silver may be the halting of bacterial cell replication process for some time without permanent damage. The kinetics of this study suggest that higher inactivation and long term residual effect towards both MOs can be achieved with the application of silver at 0.08 mg/l or higher under safe limit.

The relationship of family income, family size, age and circumferences with blood pressure in the female students of the Bahauddin Zakariya University, Multan, Pakistan

In a randomly selected sample of 600 female students of the Bahauddin Zakariya University, Multan, Pakistan, belonging to different socioeconomic groups, age, family income and family size were recorded and measurements were made of arm, waist, neck and total circumferences, systolic blood pressure (SBP), diastolic blood pressure (DBP) and mean arterial pressure (MAP). The correlation coefficients between different independent (age, family income, family size, arm, waist, neck and total circumference) and dependent variables (SBP, DBP and MAP) showed that age had a strong association (p < 0.001) with all types of blood pressure, whereas the correlation coefficient of family income and family size was significant with SBP (p < 0.05) and non-significant with DBP and MAP. Moreover, all the circumferences had strong relationship (p 0.05 at least) with blood pressure. The regression coefficients of age were highly significant for SBP, DBP and MAP, whereas these were non-significant (p > 0.05) for family income and family size. The regression coefficients for arm and waist were significant (p < 0.05), whereas these were highly significant (p < 0.01 at least) for neck and total circumferences. The neck had a 0.46 mm Hg/cm with SBP, 0.41 mm Hg/cm for DBP and 0.44 Hg/cm for MAP, and these were highest among the circumferences.