Characterisation of the ZnS quantum dots and chitosan capping agent UV–vis spectroscopy measurements were conducted using PerkinElmer equipment (Lambda EZ-210, Waltham, MA, USA) in transmission mode with samples in a quartz cuvette over a wavelength range of 600 to 190 nm. All experiments were conducted in triplicate (n = 3) unless specifically noted, and data was presented as mean ± standard deviation. Photoluminescence (PL) characterisation of the ZnS-chitosan (CHI) conjugates was conducted based on spectra acquired at room temperature using the Nanodrop AZD4547 mouse 3300 fluoro-spectrometer (Thermo Scientific, UV LED with λ excitation = 365 ± 10 nm). The relative activity was calculated by
subtracting the backgrounds of the samples without QDs. All tests were performed using a minimum of four repetitions (n ≥ 4). In addition, QD colloidal media were placed inside a ‘darkroom chamber’ , where they were illuminated by a UV radiation emission bulb (λ excitation = 365 nm, 6 W, Boitton Instruments, Porto Alegre, Brazil). Digital colour images were collected of the fluorescence of the QDs in the visible range of the spectrum. X-ray diffraction (XRD) patterns were recorded using a PANalytical X’Pert diffractometer (Cu-Kα radiation with λ = 1.5406 Å, Almelo, The Netherlands). Measurements were see more performed
in the 2θ range of 15° to 75° with steps of 0.06°. Nanostructural characterisations of the QD bioconjugates, based on the images and selected area electron diffraction (SAED) patterns, were obtained using a Tecnai G2-20-FEI transmission electron microscope (TEM; Hillsboro, OR, USA) at an accelerating voltage of 200 kV. Energy-dispersive X-ray (EDX) spectra were collected using the TEM for element chemical learn more analysis. In all the TEM analyses, the samples were prepared by dropping the colloidal dispersion onto a porous carbon grid. The QD size and size distribution data were obtained based on the TEM images Amino acid by measuring at least 100 randomly selected nanoparticles using an image processing program (ImageJ, version 1.44, public
domain, National Institutes of Health). ZnS-CHI quantum dots were analysed by diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) method (Thermo Fischer, Nicolet 6700, Waltham, MA, USA) over the range of 400 to 4,000 cm-1 using 64 scans and a 2-cm-1 resolution. These samples were prepared by placing a droplet of the chitosan solution or ZnS-chitosan dispersions onto KBr powder and drying at the temperature of 60°C ± 2°C for 24 h. For potentiometric titration studies, dried chitosan (0.20 g) was dissolved in 20 mL of 0.10 mol.L-1 HCl with gentle stirring overnight and diluted with 20 mL of DI-water. Under continuous stirring, 100 μL of 0.10 mol.L-1 sodium hydroxide solution was added, then allowed to equilibrate, and the pH recorded using a pH meter with a glass electrode (Quimis, Diadema, Brazil). This sequence was repeated until neutralisation of the HCl, and deprotonation of amine groups occurred.