Accessing photoresponsive copper selenide nanomaterials and thin films through tetranuclear Cu(I) pyridylselenolate cluster

Abstract

The development of single-source molecular precursor for the synthesis of nanomaterials with controlled size and morphology has led to important scientific discoveries in past few decades. Herein, we describe the synthesis of air and moisture stable copper cluster complex with 5-methyl-2-pyridylselenolate, [Cu{2-SeC5H3(Me-5)N}]4 as molecular precursor for copper selenide nanomaterials and thin films. The complex was obtained in good yield, and the purity of the complex was evaluated through multi-nuclear NMR spectroscopy. The complex upon recrystallization in chloroform and toluene produces different polymorphs whose molecular structures were unambiguously established from single-crystal X-ray diffraction technique. Thermolysis of the complex in selected high-boiling solvents afforded phase-pure Cu1.8Se nanostructures. Thin films of phase-pure Cu5Se4 were also deposited by AACVD employing [Cu{2-SeC5H3(Me-5)N}]4 on glass and silicon substrates at different temperatures. The effect of higher temperature is perceived in drastic morphology change from nanosheets to a mixture of nanosheets and nanowires of Cu5Se4 on glass substrate. The nanostructures and thin films were characterized by pXRD, EDS, SEM and TEM techniques. The direct band gaps of the nanomaterials as deduced from diffuse reflectance spectroscopy are in the range 2.74–2.86 eV. The profound effect of solvent on phase purity, morphology and band gap of the nanostructures has also been investigated thoroughly. The nanostructures demonstrated prompt photoresponse which make them suitable candidate for non-toxic and low-cost photon absorber material. A tetranuclear Cu(I) complex with 5-methyl-2-pyridylselenolate ligand has been prepared and crystallized in two polymorphic forms, namely monoclinic [Cu{2-SeC5H3(Me-5)N}]4·C6H5CH3 and triclinic [Cu{2-SeC5H3(Me-5)N}]4. The complex was subjected to undergo thermolysis and AACVD to prepare Cu1.8Se nanomaterials and Cu5Se4 thin films, respectively. The nanomaterials and thin films were characterized using pXRD, SEM and TEM techniques to understand the phase purity and morphology. Fast switching characteristics of the nanomaterials have been established by switching characteristics.