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The results from the investigation of optical absorption in TlGaSe 2 layered bulk semiconductor in the wavelength range of 400-900 nm between the temperatures of 19 K and 300 K are presented and discussed. In the results, the layered semiconductor TlGaSe 2 is interpreted as a direct band gap semiconductor with a band gap of about 2.04-2.14 eV at 300 K. Additionally, the optical transmission spectrum of TlGaSe 2 exhibited some peculiarities, which were attributed to indirect allowed interband transitions. It has been explained that the optical absorption edge of TlGaSe 2 can be characterized by the presence of an Urbach-like tail as well as a high-energy Tauc absorption region. The Tauc slope and Tauc energy gap were extracted from the absorption coefficient data by using the Tauc procedure. The results revealed that the 'amorphized' structure of TlGaSe 2 which is prominent in near conduction/valance band energy states, cannot be ignored for the understanding of the optical transition mechanisms in this semiconductor.

p-Aminobenzoic acid (pABA) plays important roles in a wide variety of metabolic processes. Herein we report the synthesis, theoretical calculations, crystallographic investigation, and in vitro determination of the biological activity and phytotoxicity of the pABA salt, 2-hydroxyethylammonium p-aminobenzoate (HEA-pABA). The ability of neutral and anionic forms of pABA to interact with TIR1 pocket was investigated by calculation of molecular electrostatic potential maps on the accessible surface area, docking experiments, Molecular Dynamics and Quantum Mechanics/Molecular Mechanics calculations. The docking study of the folate precursor pABA, its anionic form and natural auxin (indole-3-acetic acid, IAA) with the auxin receptor TIR1 revealed a similar binding mode in the active site. The phytotoxic evaluation of HEA-pABA, pABA and 2-hydroxyethylamine (HEA) was performed on the model plant Arabidopsis thaliana ecotype Col 0 at five different concentrations. HEA-pABA and pABA acted as potential auxin-like regulators of root development in Arabidopsis thaliana (0.1 and 0.2 mM) and displayed an agravitropic root response at high concentration (2 mM). This study suggests that HEA-pABA and pABA might be considered as potential new regulators of plant growth.