In situ application of polyelectrolytes in zinc oxide nanorod synthesis: Understanding the effects on the structural and optical characteristics

Effects of Polyethylenimine and Its Molecular Weight on the Chemical Bath Deposition of ZnO Nanowires

“…It has been suggested that the adsorption of PEI on the sidewalls of ZnO NWs proceeds through the favorable electrostatic interactions between its protonated −NH 2 side groups and the negatively charged m -planes at a high pH above its isoelectric point (IEP) around 10.5, but the present mechanism is still under debate. PEI has typically been used as the only chemical additive ,,− or with the combination of ammonia. ,− Ammonia is often introduced in aqueous solution to increase the pH above 10.5 and to complete the action of PEI by further reducing the homogeneous nucleation. − The role of ammonia is expected to complement the role of PEI to reach an even higher aspect ratio. However, at that high pH, the protonation rate is below 0.1, which directly questions the mechanisms at work for the adsorption of PEI. , The effects of PEI are thus much less pronounced at that high pH, and it is not straightforward to distinguish them from the effects of ammonia.…”

“…Furthermore, the effects of the molecular weight ( M w ) of PEI, especially through its chain length, on the morphology of ZnO NWs, have never been investigated deeply, although it is expected to play a significant role. The use of PEI with the M w of 800, ,, 4000, 4500, , 25 000, 70 000, and 750 000 has been reported, whereas many other reports did not notify it. ,,,,,,, The only investigation was achieved with the M w of 800 and 25 000 using also ammonia, which somehow superimposes its effects and hence limits its impact on that specific aspect . Investigating the CBD of ZnO NWs with the addition of PEI over a broad range of M w would enable to understand in more detail its roles in aqueous solution.…”

High-Quality, Reproducible ZnO Nanowire Arrays Obtained by a Multiparameter Optimization of Chemical Bath Deposition Growth

“…25 Although the effect of adding different concentrations of PEI on the morphology and the properties of ZnO NWs has been amply documented in the literature, the comparison of the influence of the molecular weight keeping all other parameters the same has not yet been explored. A diverse set of PEI molecular weights has been studied, with values ranging from low, i.e., 800, 13,21 4000, 18 4500, 17 to as high as 70 000, 24 or 750 000, 26 whereas, in several other works, the molecular weight is not specified. 12,14,16,20,22,23,25 The brief survey presented above demonstrates that, despite the vast number of attempts to optimize the growth parameter of the CBD, further exploration is still indispensable for improving the physical properties of the ZnO nanowire arrays, including the concurrent control of their aspect ratio, the NW height growth rate, and the density of defects.…”

“…Although the effect of adding different concentrations of PEI on the morphology and the properties of ZnO NWs has been amply documented in the literature, the comparison of the influence of the molecular weight keeping all other parameters the same has not yet been explored. A diverse set of PEI molecular weights has been studied, with values ranging from low, i.e., 800, , 4000, 4500, to as high as 70 000, or 750 000, whereas, in several other works, the molecular weight is not specified. ,,,,,, …”

Chapter 9. Nano dimensional ZnO: new chemical insights from an old material

“…The average diameter and length of the nanorods discretely increased by B15 nm and B1 mm, respectively, for each repeat reaction. Suresh et al 85 have reported a simple hydrothermal approach that involved the in situ introduction of a polyelectrolyte. A protonated polyelectrolyte such as polyethylenimine added to the aqueous growth medium, resulted in that part of the positively charged species binding themselves around the lateral facets of the ZnO nanorods.…”