In contemporary circumstances, the ecosystem suffers numerous deficiencies such as energy crisis and environmental destruction . Moreover, the speedy germination of dye industries drives precarious pollutants without treating properly consequently it causes environmental pollution . Among the industrial dye, Amaranth employed principally in the generation of consumer products including paints, textile, printing inks, papers and plastics [3, 4]. But, Amaranth dye has been not entirely degraded and professes contradictory influences on living organisms such as persistent and consumptive toxicity . On the other hand, the conventional light sources such as incandescent lamp, fluorescent lamp, halogen lamp and so forth consuming more energy for illumination as well as emitting heat radiation during the illumination causes negative risk to growing the global warming [5, 6]. Conversely, the opto-electronic devices specifically in light emitting diode (LED) could need minimum energy, limits CO2 discharge, huge illuminating enforcement and extended lifespan . Consequently, exploration for peculiar and effective material with large photocatalysis efficacy and extraordinary luminescent character is a dominant attention to the today's researchers.
In modern times, inorganic nano-structured samples have become increasingly popular in energy crisis based research groups . Among them the simple metal oxides such as ZnO, CuO, MgO, NiO, BaO and etc., these are extensively applicable in numerous inherent areas due to their remarkable physicochemical characteristics . Specifically, zinc oxide (ZnO) is a crucial constituent of the inorganic group and applied in diverse distinctive applications such as photonics, spintronics, sensors, energy conversion, opto-electronics, photocatalytic and other fields on account of its phase pure wurtzite hexagonal structure, high thermal conductivity, sophisticated band gap (3.3 eV), high exciton binding energy (60 meV), huge chemical invariability, abundant and non-toxicity . In general, the crystallinity, surface morphology, defects in crystal and optical band gap are directly correlated to the activity of photocatalysis and photoluminescence . Hence, many researches have progressed distinctive techniques for the fabrication of ZnO such as hydrothermal , sonochemical , solid state , surfactant-assisted  and thermal spreading  preparation technique. Among these, the thermal spreading synthesis method is one of the economical and easy to prepare the material. Besides the above-mentioned preparation methods, thermal spreading synthesis is one of the inexpensive and straightforward to prepare the material. Furthermore, the initiation of a foreign element into the semiconductor matrix, notably in the transition element is an active approach to achieve intensified photocatalytic and luminescence property. Among the transition metals, the divalent Cu2+ is the essential candidate because it is a prominent luminescence candidate which can enhance the luminescence of ZnO by creating localized impurity levels . Likewise, the physical and chemical properties of copper are more similar to zinc which can modify the microstructure and the optical properties of the ZnO crystal system . Recently, Alatawi et al.,  reported on various dopant concentration of Cu2+ in ZnO using the hydrothermal method for the efficient photodegradation of methyl orange (MO) under solar irradiation. The enhanced photocatalytic activity of Cu doped ZnO nanorods via the vapour transport method for the degradation of resazurin (Rz) dye exposure by UV irradiation, reported by Rajneesh et al. . Moreover, the strong green emission spectrum was attained by systematically Cu doped ZnO materials which are potentially important for photocatalytic and solar cell devices suggested by Sajjad et al., . Raji et al.,  suggest that the Cu2+ doped ZnO nanoparticles synthesized by co-precipitation technique can give the strong blue and green emissions which is a potential for use in white light emitting diodes.
We inspired by the preceding cases, tried an attempt to fabricate using the thermal spreading technique with a different dopant concentration of Cu2+ and study their photoluminescence and photocatalytic property. To fashionable our ability, this article is an open doorway of energy and environmental application of Cu2+ doped ZnO fabricated through the thermal spreading technique for intense blue-green emission as well as photodegradation of Amaranth.