Goutam Manna

Photocatalytic Au–Bi2S3 Heteronanostructures†

Au-Bi2S3 heteronanostructure photocatalysts were designed in which the coupling of a metal plasmon and a semiconductor exciton aids the absorption of solar light, enhances charge separation, and results in improved catalytic activity. Furthermore, these nanostructures show a unique pattern of structural combination, with Au nanoparticles positioned at the center of Bi2S3 nanorods. The chemistry of formation of these nanostructures, their epitaxy at the junction, and their photoconductance were studied, as well as their photoresponse properties.

Mn-Doped Multinary CIZS and AIZS Nanocrystals

Multinary nanocrystals (CuInS2, CIS, and AgInS2, AIS) are widely known for their strong defect state emission. On alloying with Zn (CIZS and AIZS), stable and intense emission tunable in visible and NIR windows has already been achieved. In these nanocrystals, the photogenerated hole efficiently moves to the defect-induced state and recombines with the electron in the conduction band. As a result, the defect state emission is predominantly observed without any band edge excitonic emission. Herein, we report the doping of the transition-metal ion Mn in these nanocrystals, which in certain compositions of the host nanocrystals quenches this strong defect state emission and predominantly shows the spin-flip Mn emission. Though several Mn-doped semiconductor nanocrystals are reported in the literature, these nanocrystals are of its first kind that can be excited in the visible window, do not contain the toxic element Cd, and provide efficient emission. Hence, when Mn emission is required, these multinary nanocrystals can be the ideal versatile materials for widespread technological applications.

Tuning the Emission Colors of Semiconductor Nanocrystals Beyond their Bandgap Tunability: All in the Dope

Adopting the concept of one dopant for one color, all the prominent emitting colors in the visible windows are obtained by doping selective dopants (Ag, Cu, Ni, and Cu) in an appropriate host (alloy of Cdx Zn1-x S) with fixed size/composition and bandgap. Analyzing the origin of these emissions the relative position of respective dopant states are correlated.

Au–Thiol Interaction Chemistry to Influence the Structural Transformation of Semiconductor Nanocrystals and Formation of Giant Nanostructures

Giant nanostructures which are difficult to design by the classical growth process can be fabricated in a facilitated and well programmed surface ligand removal protocol employing the thiol-gold strong interaction chemistry. When thiol capped small ZnSe seed nanocrystals are treated with amine capped gold particles, gold snatches the thiol ligands from ZnSe and forces them to agglomerate leading to the giant crystalline ZnSe nanostructures.