Hydrophilic NPs Research Articles

A non-classical route of efficient plant uptake verified with fluorescent nanoparticles and root adhesion forces investigated using AFM

Classical plant uptake is limited to hydrophilic or water-dispersible material. Therefore, in order to test the uptake behaviour of hydrophobic particles, here, we tested the fate of hydrophobic particles (oleylamine coated Cu2-xSe NPs (CS@OA)) in comparison to hydrophilic particles (chitosan-coated Cu2-xSe NPs (CS@CH)) by treatment on the plant roots. Surprisingly, hydrophobic CS@OA NPs have been found to be ~ 1.3 times more efficient than hydrophilic CS@CH NPs in tomato plant root penetration. An atomic force microscopy (AFM) adhesion force experiment confirms that hydrophobic NPs experience non-spontaneous yet energetically favorable root trapping and penetration. Further, a relative difference in the hydrophobic vs. hydrophilic NPs movement from roots to shoots has been observed and found related to the change in protein corona as identified by two dimensional-polyacrylamide gel electrophoresis (2D-PAGE) analysis. Finally, the toxicity assays at the give concentration showed that Cu2-xSe NPs lead to non-significant toxicity as compared to control. This technology may find an advantage in fertilizer application.

Fast coating of hydrophobic upconversion nanoparticles by NaIO4-induced polymerization of dopamine: Positively charged surfaces and in situ deposition of Au nanoparticles

In this work, hydrophobic upconversion nanoparticles (UCNPs) were transformed into hydrophilic NPs via the rapid oxidative polymerization of dopamine (DA) induced by NaIO4 in a water-in-oil microemulsion system. The polydopamine (PDA)-coated UCNPs synthesized using NaIO4 as the oxidant exhibited a positive charge (+26.4 mV) at pH 7.0. Those prepared using ambient O2 as the oxidant had a negative charge (–15.4 mV). The difference in the composition between PDA-coated UCNPs using NaIO4 (UCNPs@PDA-NaIO4) and those using ambient O2 (UCNPs@PDA-O2) as oxidants was supported by the XPS and FTIR results. The difference in the surface charges may be due to variation in the composition, which probably attributed to the different oxidants used. A series of controlled experiments were carried out to infer the origination of the positive charges of UCNPs@PDA-NaIO4. Furthermore, Au nanoparticles (Au NPs) were deposited on UCNPs@PDA-NaIO4 where PDA served as both the reductant and the stabilizer so that additional reagents and thermal treatments were not necessary. The effect of pH on the deposition of Au NPs was also studied. In addition, the load density of Au NPs on the surface of the PDA-coated UCNPs could be adjusted by changing the dosage of HAuCl4, which could effectively enhance the upconversion luminescence (UCL) intensity. This work provides a method to regulate the surface charge of the PDA coating, and the nanocomposites with unique properties synthesized by this method may be employed in biological imaging, diagnostic analysis, and other biological fields.

Synergic effects of hydrophilic and hydrophobic nanoparticles on performance of nanocomposite distillation membranes: An experimental and numerical study

Abstract Supported flat sheet nanocomposite polyvinylidenefluoride (PVDF) membranes embedded with hydrophilic TiO2, hydrophobic TiO2, or the combination of them were fabricated via phase inversion process. The membranes were characterized by scanning electron microscopy, energy dispersive X-ray spectroscopy, atomic force spectroscopy, and the measurement of water contact angle and liquid entry pressure of water and subjected to tests on vacuum membrane distillation (VMD) performance. Addition of appropriate amounts of either hydrophilic or hydrophobic NPs was found to enhance VMD flux but hydrophilic NPs caused significant decrease of liquid entrance pressure of water (LEPw) while hydrophobic particles did not show significant impacts on LEPw. Addition of both hydrophilic and hydrophobic NPs demonstrated synergistic effects in terms of both enhanced flux and LEPw due to their different but complimentary effects on membrane structures. At feed temperature of 27.5 °C, the VMD pure water permeate flux of the composite membrane embedded with 5 wt% hydrophilic TiO2 NPs and 2 wt% of hydrophobic TiO2 NPs (total 7 wt% NPs) was 4.26 kg/m2h with a LEPw of 28 psi, while those of neat PVDF membrane, the membrane embedded with 7 wt% of hydrophilic NP, and the membrane with 7 wt% hydrophobic nanoparticles were 0.335, 3.57, and 1.25 kg/m2 h, respectively, and the LEPw of these membranes were 51, 24 and 47 psi, respectively. It is noted that at 5 wt% addition, the flux of M-L5 (hydrophilic NPs) is 3 times higher than the M-B5 (hydrophobic NPs). Furthermore, by adding another 2 wt% of NPs, flux increment by M-L5-B2 (hydrophobic NPs) is 3.5 times higher than M-L7 (hydrophilic NPs). Therefore, in both the effects combined, the highest flux was achieved by M-L5-B2 indicating synergistic effect of hydrophilic and hydrophobic NPs on the membrane flux. The salt rejection of above 99% could be maintained for 3 h by the membrane in which both hydrophilic and hydrophobic NPs were loaded. Numerical analyses of heat and mass transfer were also carried out to study the impact of hydrophilic and hydrophobic NPs on membrane characteristics.