Unicam uv 300 spectrophotometer

Silver nanoparticles (AgNPs) were prepared by the well-known Turkevich method, using citrate as a reducing and capping agent [27 (link)]. Briefly, 10 mL of a 1 mM AgNO₃ (Sigma) solution in deionized water was heated until it started to boil. After that, 10 mL of an aqueous solution of 5 mM sodium citrate (Sigma) was dropwise to the silver nitrate solution. The heating was continued for 10 min, and then cooled to room temperature. The solution was filtered using a 0.22 µm Sartorius filter prior to use. An absorption spectrum was recorded with the Unicam UV 300 spectrophotometer to observe the plasmon absorbance of Ag colloids.
Diameter of the particles was determined by electron microscopy. High-resolution Transmission electron microscopy (HR-TEM) images were recorded with a 300 kV FEI TITAN G2 60–300 microscope (Thermo Fisher Scientific, Waltham, MA, USA) of the Centre for Scientific Instrumentation, University of Granada (CIC-UGR, Granada, Spain). AgNPs were also imaged by Scanning transmission electron microscopy (STEM) using a high-angle annular dark field (HAADF) detector. AgNPs diameter distribution (histogram) was estimated by measuring the diameter of 100 nanoparticles with ImageJ software (version 1.48v; NIH, Bethesda, MD, USA).

Boron trifluoride diethyl etherate (BF₃O(C₂H₅)₂) and 2,4-dimetylpyrrole were freshly distilled under reduced pressure before use. The solvents employed in the reaction were purified by distillation in the presence of drying reagents (metallic sodium for THF or CaH₂ for dichloromethane). All the synthetic procedures were carried out under an argon atmosphere. The purification of the products was performed by column chromatography in silica gel and the elution was checked by thin layer chromatography (TLC). All intermediates and final compounds were characterized by ¹H NMR and ¹³C NMR spectroscopies and MALDI-TOF mass spectrometry. NMR spectra were carried out on a Bruker Avance 400 MHz, operating at 400 MHz and 100 MHz for ¹H and ¹³C, respectively. Samples were dissolved in deuterated chloroform. MALDI-TOF mass spectra were recorded using dithranol as matrix on a Bruker Daltonics Flex Analysis. UV-Visible (UV-Vis) spectra were carried out on a Unicam UV300 spectrophotometer using quartz cells with a width of 1 cm and THF (HPLC grade) as the solvent. Fluorescence spectra were recorded on a Fluorolog 3 spectrophotometer from Horiba with a xenon lamp as light source. The slit width for excitation and emission were defined to 1 nm.

The butylparaben decay rate was monitored by high pressure liquid chromatography (HPLC) coupled with UV detection using a Waters apparatus. Analysis was performed with a Waters Nova-Pak C18 column (3.9 mm × 150 mm) using a mobile phase consisting of a degassed mixture (70/30, v/v %) of methanol and acidified water (0.01% orthophosphoric acid) at a constant flow of 1 mL min⁻¹. The detailed description of this analysis of BP is reported elsewhere [19 (link),23 (link)]. The spectrophotometric analysis was performed on a Unicam UV 300 spectrophotometer. The dissolved organic carbon measurements were performed on a HACH IL 550TOC-TN apparatus. The ion concentrations were determined by an ion chromatograph (Dionex model ICS) on an IonPac CS18 (for cations) and an IonPac AS18 (for anions).
The performed experiments allowed us to estimate the extent of direct reaction of butylparaben with hydrogen peroxide in the absence of radiation, (“dark reaction”).
Results indicated an insignificant role of the direct reaction of studied compounds with H₂O₂. The blank reaction was carried out to investigate the hydrolysis of BP. The experiments showed no decomposition of the investigated compound in the dark after 12 h, much longer time than used during the photodegradation.
Experiments were performed in duplicate to assure accurate data acquisition.