Effect of 2,4-dinitrophenol dye doping on tristhioureazinc(II) sulfate single crystals: a potential nonlinear optical material

Abstract

Good quality single crystals of 2,4-dinitrophenol (DNP)-doped tristhioureazinc(II) sulfate (ZTS) were successfully grown by employing the simple and cost effective slow-evaporation solution technique. To study the effect of doping on various device properties, the grown single crystals were subjected to powder X-ray diffraction (PXRD), high-resolution XRD, thermogravimetric analysis (TGA), Vickers hardness testing, and UV–visible, photoluminescence (PL) and Fourier transform IR (FTIR) spectroscopy techniques. The crystal structure of DNP-doped ZTS bulk single crystals remained the same as the crystal structure of ZTS. However, the changes in intensities of the diffraction peaks in the PXRD spectra indicated the incorporation of dopants into the crystalline matrix. FTIR studies confirm the incorporation of dopants into the crystalline matrix, shown by the shifting of certain prominent absorption bands towards higher energy. This also indicated the induced useful strain due to doping, leading to charge transfer and the enhancement of nonlinear optical properties. The cut-off wavelength and optical band gap energy of pure ZTS and DNP-doped ZTS crystals were studied by UV–visible absorption spectroscopy, revealing a slight reduction in the optical band gap energy due to doping, which in turn revealed the enhancement of the optical range. PL studies revealed an enhanced optical range of photoluminescence in ZTS crystals. Second harmonic generation (SGH) studies carried out by the Kurtz powder technique revealed the enhancement of SHG value due to DNP doping. To ensure the thermal stability and mechanical strength of the grown crystals with doping (required from the point of view of device applications), TGA and Vicker's hardness studies were performed.