Model uv 1900

The physicochemical properties determined in this study were density, polarity, and viscosity. Density measurement was carried out by weighing a known volume of DES dispensed from a micropipette previously calibrated using purified water. The Nile Red dye was added to each DES as a solvatochromic probe to determine λ_max, the wavelength at which the maximum visible light absorption occurred [30 (link)]. A UV-vis spectrophotometer (Model UV-1900, Shimadzu, Kyoto, Japan) was used to scan the DES-dye mixtures in the 400–700 nm range and Equation (1) was used to calculate the Nile Red polar parameter E_NR (in kcal/mol). Viscosity test was performed using a Brookfield viscometer at room temperature with LV spindle no. 1 at 6, 12, and 30 rpm.

Using the Folin–Ciocalteu method and gallic acid as the reference, the total phenolic content of the aqueous leaf extract was determined [26 ]. To 1 mL of extract, 1 mL of Folin–Ciocalteu reagent and 2 mL of Na₂CO₃ (20% w/v) were added, and then distilled water was used to make up a volume of 10 mL. This mixture was then allowed to stand for 8 min and was finally centrifuged at 6000 rpm for 10 min. At 730 nm, using the UV-vis double beam spectrophotometer (Model UV 1900 Shimadzu), the absorbance of the supernatant solution was measured against a blank. Similarly, the blank was prepared but instead of extract, it contained respective solvent.

The UV-Vis absorption spectrum of AgNPs in the wavelength range of 350–550 nm was recorded using a UV-Vis double beam spectrophotometer (Model UV 1900, Shimadzu, Kyoto, Japan). Deionised water was used as control. The hydrodynamic size distributions, zeta potential, and polydispersity index (PDI) of nanoparticles were determined by using Particle Size Analyzer (PSA Microtracnanotrac wave II, Anton Paar, Graz, Austria) instrument. The surface morphology of biosynthesized AgNPs was analyzed with the help of Field emission scanning electron microscopy (FESEM, JSM-7610FPlus, JEOL Ltd., Akishima, Japan) operating at an accelerating voltage of 0.1 to 30 kV equipped with an energy dispersive X-ray spectroscopy (EDX) detector for elemental mapping. On a JEM/2100 PLUS running at 200 kV, High resolution transmission electron microscopy (HRTEM) was successfully performed. A drop of the biosynthesized AgNPs dispersed in ethanol was placed at 400 mesh copper grid coated with a holey carbon film for the HRTEM investigations. The chemical composition of plant extract and AgNPs were studied by using FTIR spectrophotometer (Perkin Elmer, Waltham, MA, USA) and spectra was taken in the 4000–650 cm⁻¹ region.