Neetesh Kumar

Fabrication of micro/nanostructured α-Fe2O3 hollow spheres: effect of electric field on the morphological, magnetic and photocatalytic properties

In this paper, we reported the continuous fabrication of α-Fe2O3 hollow spheres with sponge like morphology using an electric field assisted (by applying DC voltage) continuous spray pyrolysis technique. The effect of applied voltage on the morphological, magnetic and photocatalytic properties is systematically studied. The samples prepared under an electric field have shown enhanced magnetic and photocatalytic properties compared to the samples prepared without an electric field (0 kV). It is observed that the sample fabricated at an applied voltage of 2 kV has a remarkably high coercivity (HC) of ∼4.5 kOe and manifested the maximum degradation efficiency of 98% and 95% under visible light for methylene blue and rhodamine B dye, respectively owing to its sponge like morphology, enhanced surface area and pore volume. These α-Fe2O3 samples have potential applications in large memory devices, permanent magnets and efficient adsorbent materials for the removal of organic pollutants from water.

Photoluminescence study of oleic acid capped and hexanoic acid washed CdS quantum dots

The effects of oxygenic versus oxygen-free environment on the excitonic and defect emission of colloidal oleic acid (OA) capped and hexanoic acid washed CdS quantum dots (QDs) were studied using continuous photoluminescence (PL) measurements. In vacuum (∼10−3 mbar) OA capped CdS show 90% and 30% quenching of excitonic and defect emission intensity, respectively, whereas acid washed samples show 80% excitonic and 78% defect emission intensity quenching. It is also observed that the excitonic and defect emission intensities are fully recovered in air on cycling the air/vacuum pressure cycles. Our analysis suggests that due to high non-radiative recombination, both excitonic as well as defect emission intensity quenches. The low temperature PL study clearly shows that the enhancement in defect emission intensity for acid washed QDs is about three times higher than that of OA capped QDs, which is due to suppression of non-radiative recombination. Our work shows that emission can be controlled by modulating the degree of passivation ether by acid washing process or controlling the air/vacuum environment or both.