Synthesis of Graphene Quantum Dots Decorated With Se, Eu and Ag As Photosensitizer and Study of Their Potential to Use in Photodynamic Therapy

GQDs decorated with europium (Eu), silver (Ag) and selenium (Se) at molar ratios of 0.1%, 0.3% and 0.5% were produced for the first time at different temperatures of 180 °C, 200 °C and 220 °C. Surface passivation was carried out with polyethylene glycol (PEG) to increase the intensity of photoluminescence (PL) of the produced samples. The prepared quantum dots were characterized by X-Ray diffraction (XRD), Fourier transformed infrared spectroscopy (FTIR), transmission electron microscopy (TEM), PL and ultraviolet-visible spectroscopy. GQDs synthesized at 180 °C and decorated with Se (0.3%) had maximum PL intensity along with long lasted afterglow over 90 min compared with other samples. Excitation wavelength at 360 nm produced maximum emission at 600-900 nm and resulted in high singlet oxygen (¹O ₂) generation which makes it a good candidate for photodynamic therapy applications.

Sonochemical synthesis of hierarchical ZnO nanostructures

This work is about fabrication of ZnO nanostructures (ZnO-NS) via a simple sonochemical method. The chemicals used for the synthesis of various shaped ZnO are Zn salt, sodium hydroxide and ammonia solution without other structure directing agent or surfactant needed. This method is feasible and green, as it does not require high temperature and/or highly toxic chemicals. The shape of the ZnO-NS can be tuned by adjusting the ultrasound energy dissipated via varying the ultrasonication time from 5 to 60 min. It was found that uniform ZnO nanorods with diameter around 50 nm were formed after 15 min of ultrasonication while flowerlike ZnO-NS was formed after 30 min. This method produces high quality ZnO-NS with controllable shapes, uniformity, and purity.

Theoretical and experimental approach on dielectric properties of ZnO nanoparticles and polyurethane/ZnO nanocomposites

ZnO nanoparticles (ZnO-NPs) were synthesized by a new, simple sol-gel method in gelatin media (particle size of ZnO ≈ 30 to 60 nm). Polyurethane/ZnO nanocomposites thin films (PU/ZnO-NPs) were prepared by mixing the ZnO-NPs into PU prepolymer. The nanocomposites were structurally characterized using Fourier transmission infrared (FTIR) spectroscopy. The interaction between ZnO-NPs and PU matrix is studied by analyzing the differences in C=O region and N-H region of FTIR spectra. The morphology of ZnO and PU/ZnO nanocomposites were assessed using transmission electron micrograph, TEM, and field emission scanning electron microscope, FESEM, respectively. The dielectric properties of ZnO-NPs were attributed to the interfacial and orientation polarization. Measurement is reported for the real and imaginary parts of the ac conductivity of ZnO-NPs in the frequency range of 10 to 106 Hz in the temperature range 298–478 K. The experimental results are interpreted in terms of the classical correlated-barrier hopping theory. In addition, the dielectric properties of PU/ZnO nanocomposites (0–15 vol. % filler concentration) were analyzed with respect to frequency. Quantitative analysis based on mixing laws for two-phase spherical dispersion system such as Lichtenecker, Maxwell, Jayasundere and Smith, and Yamada equations was used to predict the effective permittivity accurately up to 15 vol. % of ZnO in PU matrix.

Synthesis and characterization of a narrow size distribution of zinc oxide nanoparticles

Zinc oxide nanoparticles (ZnO-NPs) were synthesized via a solvothermal method in triethanolamine (TEA) media. TEA was utilized as a polymer agent to terminate the growth of ZnO-NPs. The ZnO-NPs were characterized by a number of techniques, including X-ray diffraction analysis, transition electron microscopy, and field emission electron microscopy. The ZnO-NPs prepared by the solvothermal process at 150°C for 18 hours exhibited a hexagonal (wurtzite) structure, with a crystalline size of 33 ± 2 nm, and particle size of 48 ± 7 nm. The results confirm that TEA is a suitable polymer agent to prepare homogenous ZnO-NPs.

Time-dependent effect in green synthesis of silver nanoparticles

The application of “green” chemistry rules to nanoscience and nanotechnology is very important in the preparation of various nanomaterials. In this work, we successfully developed an eco-friendly chemistry method for preparing silver nanoparticles (Ag-NPs) in natural polymeric media. The colloidal Ag-NPs were synthesized in an aqueous solution using silver nitrate, gelatin, and glucose as a silver precursor, stabilizer, and reducing agent, respectively. The properties of synthesized colloidal Ag-NPs were studied at different reaction times. The ultraviolet-visible (UV-vis) spectra were in excellent agreement with the obtained nanostructure studies performed by transmission electron microscopy (TEM) and their size distributions. The prepared samples were also characterized by X-ray diffraction (XRD) and atomic force microscopy (AFM). The use of eco-friendly reagents, such as gelatin and glucose, provides green and economic attributes to this work.