National Institute Of Technology Silchar

The self-assembly of small molecules with a suitable metal ion is a critical bottom-up approach for preparing solution-processable metallo-supramolecular polymers and to realize their potential as a photocatalyst. Herein, we report the design, synthesis, self-assembly, and gelation behavior of a low-molecular-weight gelator (LMWG) based on a pyrene core connected to four terpyridine units (TPY-PY) through amide linkages. TPY-PY forms an organogel (OG) in the DMSO/H2O mixed solvent with a nanofibrillar morphology. In contrast, the introduction of RuII with the LMWG resulted in a Ru-TPY-PY coordination polymer gel (CPG) with a cross-linked fibrillar nanostructure with a length of several micrometers. The Ru-TPY-PY CPG exhibited highly efficient photoreduction of CO2 to CO (yield: 10.79 mmol g–1, rate: 899.17 μmol g–1 h–1) with 90% selectivity, under visible light irradiation, and in the presence of triethylamine (TEA) as a sacrificial electron donor. Moreover, metallo-supramolecular polymers with diverse nanomorphologies, formed at different RuII to TPY-PY ratios, showed different efficiencies in the photo reduction of CO2 to CO. Among these nanostructures, 1D nanofibers exhibited enhanced photocatalytic activity compared to the nanospheres for CO2 reduction, attributed to the abundance of catalytically active sites on their surface with facile CO2 diffusion capabilities. Furthermore, femtosecond transient absorption spectroscopy, in situ DRIFTS analysis, and DFT calculation help to understand the feasibility of the electron transfer pathway, and reaction mechanism in the overall process. The “soft” processable hybrid metal–organic supramolecular polymers that integrate both the catalytic site and the light-absorbing units are a class of catalysts showing efficient CO2 photoreduction to CO.

In this study, a detailed comparison between flat and inclined Ti-6Al-4V alloy plates under nanosecond fiber laser machining is presented, focusing on the combined effects of laser parameters and surface inclination on machining outcomes. The results demonstrate a strong interaction between laser power, beam inclination, and workpiece angle, significantly influencing the width, depth, and heat-affected zone (HAZ) of the machined surfaces. The width of the laser-treated region is highly sensitive to average laser power, exhibiting the greatest impact at the focal position (84.63%) and a similarly substantial effect near the nozzle (+15 mm defocus, 73.92%), while beam angle also contributes to width variations, though to a lesser extent. Groove depth is primarily governed by average power at focus (77.85%), with its influence decreasing at off-focus positions (−15 mm, 30.06%), whereas beam angle plays a more prominent role at defocused positions (42.76% at −15 mm). The HAZ is affected by both average power (64.65% at focus and 61.50% at −15 mm) and beam angle (7.42% at focus and 5.44% at −15 mm). Inclinations of 10° or higher result in increased spatter formation and a higher likelihood of micro-fracture, particularly at focal and +15 mm positions. This work highlights the importance of prioritizing width in laser machining, while depth can be adjusted according to other response requirements. The findings provide valuable insights for optimizing laser parameters to achieve superior surface quality in precision-critical industries such as aerospace, automotive, and medical device manufacturing.