Ternary I–III–VI2 semiconductors (where I = Cu, Ag; III = Ga, In, VI = S, Se) have been gaining considerable interest in nanoscale research primarily due to their band structures, which are suitable for light-harvesting and light-emitting applications. While a great deal of attention has been given to the Cu-based systems, there are relatively few reports on their Ag-based counterparts. Much of the studies have been limited to AgInS2 (AIS),which has been known to exist in the tetragonal and orthorhombic form.Meanwhile, AgGaS2 (AGS), an attractive material for optoelectronics and photocatalytic applications, is not as well-explored. Unlike in the case of AIS,the orthorhombic phase has never been previously observed for AGS. Using a simple non-injection colloidal synthetic approach,we present the first successfulsynthesis of AGS nanocrystals that have the wurtzite-derived orthorhombic crystal structure. The synthetic strategy involves the co-thermal decomposition of Ag(I) and Ga(III) dithiocarbamates in suitable coordinating solvents. It was found that the formation of the orthorhombic polymorph of AGS can be promoted with the use of long-chain alkanethiols and primary alkylamines as coordinating solvents.Using the crystallographic data for orthorhombic AIS as reference, we have carried out Rietveld analysis of our diffraction data and determined the lattice parameters for orthorhombic AGS. From optical absorption data, we have determined the band gap of orthorhombic AGS to be ~2.7 eV, which lies in the visible spectrum. The photocatalytic potential of the orthorhombic AGS nanocrystals for organic dye degradation was investigated under visible-light illumination. We have found that 93% of RhB dye molecules could be degraded within 90 min, demonstrating the effectiveness of orthorhombic AGS nanocrystals as a visible-light-responsive photocatalyst. References: Chem. Commun., 2014, 50, 7128−7131.

Colloidal synthesis and photocatalytic properties of orthorhombic AgGaS2 nanocrystals

249th National Meeting (2015)

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