Hydrothermal synthesis of ZnO nanorods: a statistical determination of the significant parameters in view of reducing the diameter

Cytotoxicity of PLGA-zinc oxide nanocomposite on human gingival fibroblasts

Background

Polylactic-co-glycolic acid and zinc oxide (PLGA-ZnO) nanocomposite has been investigated for its antibacterial properties, which could be beneficial for adding to wound dressings after periodontal surgery. However, its cytotoxicity against human gingival fibroblasts (HGFs) remains unclear and should be evaluated.

Methods

ZnO nanoparticles were synthesized using the hydrothermal method. These metallic nanoparticles were incorporated into the PLGA matrix by the solvent/non-solvent process. The nanomaterial was evaluated by field emission scanning electron microscopy (FESEM), Fourier transform infrared (FTIR), thermogravimetric analysis (TGA), and x-ray diffraction (XRD) analyses. HGF cells were acquired from the National Cell Bank and categorized into four groups: ZnO, PLGA, ZnO-PLGA, and control. The cells were exposed to different ZnO (1, 20, 40, 60, 80, and 100 µg/mL) and PLGA (0.2, 4, 8, 12, 16, and 20 µg/mL) concentrations for 24 and 48 hours. The cytotoxicity was tested using the MTT assay. The data were analyzed using SPSS 25, and P<0.05 was considered statistically significant.

Results

ZnO nanoparticles exhibited significant toxicity at≥40 µg/mL concentrations after 24 hours. Cell viability decreased significantly at all the tested concentrations after 48 hours of exposure. PLGA-ZnO cell viability in 24 hours was similar to the control group for all the concentrations up to 80 µg/mL.

Conclusion

ZnO nanoparticles could be toxic against HGF in high concentrations and with prolonged exposure. Therefore, incorporating ZnO nanoparticles into a biocompatible polymer such as PLGA could be a beneficial strategy for reducing their toxicity.

Forced Convective Heat Transfer Coefficient Measurement of Low Concentration Nanorods ZnO–Ethylene Glycol Nanofluids in Laminar Flow

This paper presents the experimental forced convective heat transfer coefficient (HTC) of nanorods (NRs) zinc oxide–ethylene glycol nanofluids (ZnO–EG NFs) in laminar flow. First, ZnO NRs were synthesized using a hydrothermal method that uses zinc acetate dihydrate [Zn(CH₃COO)₂·2H₂O] as a precursor, sodium hydroxide as a reducing agent, and polyvinylpyrrolidone (PVP) as a surfactant. The hydrothermal reaction was performed at 170 °C for 6 h in a Teflon-lined stainless-steel tube autoclave. The sample’s X-ray diffraction (XRD) pattern confirmed the formation of the hexagonal wurtzite phase of ZnO, and transmission electron microscopy (TEM) analysis revealed the NRs of the products with an average aspect ratio (length/diameter) of 2.25. Then, 0.1, 0.2, and 0.3 vol% of ZnO–EG NFs were prepared by adding the required ZnO NRs to 100 mL of EG. After that, time-lapse sedimentation observation, zeta potential (ζ), and ultraviolet-visible (UV–vis) spectroscopy was used to assess the stability of the NFs. Furthermore, the viscosity (μ) and density (ρ) of NFs were measured experimentally as a function of vol% from ambient temperature to 60 °C. Finally, the HTC of NFs was evaluated utilizing a vertical shell and tube heat transfer apparatus and a computer-based data recorder to quantify the forced convective HTC of NFs in laminar flow at Reynolds numbers (Re) of 400, 500, and 600. The obtained results indicate that adding only small amounts of ZnO NRs to EG can significantly increase the HTC, encouraging industrial and other heat management applications.

(Bio)polymer/ZnO Nanocomposites for Packaging Applications: A Review of Gas Barrier and Mechanical Properties

Nanotechnology is playing a pivotal role in improving quality of life due to its versatile applications in many areas of research. In this regard, nanoparticles have gained significant importance. Zinc oxide nanoparticles (ZnO NPs) amongst other nanoparticles are being used in producing nanocomposites. Methods like solvent casting, solution casting, solvent volatilization, twin-screw extrusion, melt compounding and extrusion blow molding have been applied to produce ZnO NPs based (bio)polymer composites. These composites are of great interest in the research area of food packaging materials due to their improved multifunctional characteristics like their mechanical, barrier and antimicrobial properties. This paper gives an overview of the main methods to synthesize ZnO NPs, methods to incorporate ZnO NPs in (bio)polymers, and finally, the gas barrier and mechanical properties of the nanocomposites. As a conclusion, a maximum decline in oxygen, carbon dioxide and water vapor permeability was reported as 66%, 17% and 38% respectively, while tensile strength and young's modulus were observed to increase by 32% and 57% respectively, for different (bio)polymer/ZnO nanocomposites.

Influence of ultrasonication times on the tunable colour emission of ZnO nanophosphors for lighting applications

This paper reports on the sonochemical synthesis of zinc oxide (ZnO) nanophosphors (NPr) at different ultrasonication times (5 min, 30 min, 1h, 5h, 10h and 15 h) for near white light emission applications. X-ray photoelectron spectroscopy indicated that the O1s peak consists of two components. These were O1 (ZnO) and O2 (deficient oxygen; OH groups) centred at 529.7±0.3 eV and 531.1±0.3 eV, respectively. All samples showed UV and defect level emission (DLE). The DLE enhancement was due to the increase in oxygen related defects such as oxygen vacancies/interstitials. Due to the combination of near UV and DLE near white light emission in ZnO NPr was obtained. The emission could be tuned with different ultrasonic times. It was found that the ultrasonication time influenced the growth mechanism and luminescence properties of the ZnO NPr.

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.