Ultraviolet visible spectrophotometer

The magnetic nanoparticles and nanocomposite were characterized by Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction, thermogravimetric analysis, and magnetization measurements. The FTIR spectra were recorded over the range of 400–4,000 cm⁻¹ on a Thermo Nicolet Nexus, Smart Orbit spectrometer using the KBr disk method. X-ray diffraction spectra were obtained in the range of 20–70 degrees using an XRD-6000 diffractometer (Shimadzu, Tokyo, Japan) with CuK_α radiation (λ 1.5406 Å) at 30 kV and 30 mA. Thermogravimetric analysis was carried out using a Metter-Toledo 851e instrument (Greifensee, Switzerland) with a heating rate of 10°C per minute in 150 μL alumina crucibles and in the range of 30°C–900°C. A scanning electron microscope (Nova™ NanoSEM 230; FEI, Hillsboro, OR, USA) was used to observe the surface morphology of the samples. Magnetic properties were evaluated using a 7404 vibrating sample magnetometer Lake Shore Cryotronics Inc (Westerville, OH, USA). Ultraviolet-visible spectra were measured to determine the controlled release which was performed using an ultraviolet-visible spectrophotometer (Perkin Elmer, Waltham, MA, USA).

To quantitatively measure the solubility data, the weight of water was measured by a METTLER TOLEDO analytical microbalance before and after supercritical carbon dioxide dissolving. Moreover, a series of standard Acid Red 138 solutions were freshly prepared in water solution. Standard curve of the relationship between the absorbance of Acid Red 138 and its concentration was generated using a PerkinElmer ultraviolet-visible spectrophotometer at the maximum absorbance peak (λ_max = 517 nm), as shown in Fig. 2. The absorption intensity of the absorbing solution was then tested by the ultraviolet-visible spectrophotometer after bring to volume by water in volumetric flask, and the dye concentration can be obtained accordingly.
The solubilities of water and Acid Red 138 under various supercritical carbon dioxide dyeing conditions were determined in terms of the mole fraction (y₂) according to eqn (1) and (2) after the equilibrium was achieved: where m_CO2 and m_i are the weight of carbon dioxide and solute; n_CO2 and n_i are the mole number of carbon dioxide and solute; M_CO2 and M_i are the mole mass of carbon dioxide and solute. ρ is the density of carbon dioxide, which can be obtained from the NIST fluid property database.²⁸ V are the volume of carbon dioxide.

Evaluation of the size and zeta-potential of EGCG-pNG, and the EGCG ratio in EGCG-pNG is described in our previous report.22 (link) Briefly, nanoparticle size of EGCG-pNG (in the ratio of EGCG:pNG:12.5:1.25, 25:1.25, 50:1.25, 100:1.25, 12.5:2.5, 25:2.5, 50:2.5 and 100:2.5 [all μM:ppm]) was characterized by photon correlation spectroscopy (Zetasizer Nano ZS; Malvern Instruments, Malvern, Worcestershire, UK) under 633 nm wavelength at room temperature with 173° detection angle. Mean hydrodynamic sizes were subsequently calculated through cumulant analysis (Z-average mean) from the raw data. Zeta potentials of all nanoparticles were analyzed via laser Doppler anemometry (Zetasizer Nano ZS). The free EGCG was determined via a high-performance liquid chromatography (HPLC) (Waters Corporation, Milford, MA, USA) system equipped with an automated gradient controller, 510 pumps, U6K injector, 481 detector, 746 data module, and Waters μBondapak C18 column (3.9×300 mm). The concentration of pNG was calculated based on ultraviolet-visible spectrophotometer (PerkinElmer Inc., Waltham, MA, USA) analysis via the standard curve of acknowledged pNG concentrations at 520 nm. The fraction of EGCG contained in the EGCG-pNG was calculated by dividing the total EGCG amount by the sum of the total pNG and EGCG amounts.

Total phenolic content of blackberry extract was performed employing the literature methods involving Folin-Ciocalteu reagent and gallic acid as standard.[31 ] The extract samples (0.5 mL of different dilutions) were mixed with 2.5 mL of 0.2 N Folin-Ciocalteau reagent (Sigma-Aldrich) for 5 min and 2.0 mL of 75 g/L sodium carbonate were then added. The mixture was allowed to stand for 2 h at room temperature. The absorbance was measured at 760 nm with a double beam PerkinElmer ultraviolet/visible spectrophotometer (USA). The standard curve was prepared using 50-250 mg/mL solutions of gallic acid in methanol-water (1:1, v/v).
Total phenol values are expressed in terms of gallic acid equivalent (mg/g of dry mass) which is a common reference phenolic compound.