## 1 Introduction
On the other hand, recent literature reports involved in the preparation of PNCs with improved optical performance have established that the post-synthetic treatment of nanocrystals is the best option to compensate for the loss of capping agents and favor the passivation of surface defects [42; 43; 44]. This ligand protection has been achieved by adding alkylphosphines such as trioctyl- and triphenylphosphine (TOP and TPP, respectively) [45; 46; 47] or sulfur-based organic compounds such as S-OLA complexes and thionyl chloride [48; 49]. Here, P atoms containing lone-pair electrons from TOP and TPP  
Figure 1: (**a**) Typical absorbance and PL features of CsPbBr\({}_{3}\) PNCs in absence (purple, orange) and presence of DDAB (green, red, named DDDMAB in this work) before and after three weeks of aging. (**b**) Photographs of the corresponding colloidal solutions evidence the stable high luminescence behavior of the nanocrystals after the addition of DDAB. Reproduced with permission [36]. Copyright 2019, American Chemical Society. (**c**) Typical optical features and PLQY of CsPbBr\({}_{3}\) PNCs solutions capped with the 3-(\(N\),\(N\)-dimethyloctadecylammonio)propanesulfonate and OA/OLA after two purification steps with different solvents at day 1 and after 28 days of aging. Reproduced under the terms of the CC-BY license [14]. Copyright 2018, The Authors. American Chemical Society. (**d**) Relative PL intensity of the CsPbBr\({}_{3}\) PNCs capped with OA/OLA (black line) and DDAB (red line) in ethanol medium after 2 h. Reproduced with permission [37]. Copyright 2019, American Chemical Society. (**e**) Normalized PL intensity and corresponding photographs of red-emitting CsPbI\({}_{3}\) PNCs colloidal solutions without (blue line) and with IDA treatment (red line) at day and after 15 days of aging. Reproduced under the terms of the CC-BY license [38]. Copyright 2018, The Authors. American Chemical Society. act as [PERSON]'s base to interact with [PERSON]'s acid Pb\({}^{2+}\) species, promoting electron transfer. In addition, some TOP.PbX\({}_{2}\) and TPP.PbX\({}_{2}\) adducts are formed to facilitate the complete dissolution of the PbX\({}_{2}\) precursor and facilitate the ligand coverage on the final nanocrystal product. Through this modification, high PLQY values can be obtained, with stability in ambient air for up to 1 month. Meanwhile, sulfur functional groups can replace/fill the halide vacancies into the perovskite structure, forming Pb-S bonds. In this context, the PL quenching is mitigated, and the radiative recombination pathway is maximized, providing a PLQY \(\sim\)86% with stability around 3 months. In addition, it has been shown that thioglycolic and thiolactic acid can decrease the electron trap states near the conduction band [50]. Nevertheless, the use of phosphines and some S-based compounds promote critical health issues, such as a compromised heart and depression of the central nervous system to problems in the circulatory functions. Therefore, it is pivotal to find novel and environmentally safe alternatives to reduce the risk of health issues and eventual ecosystem contamination while preserving similar or better efficiency to prepare high-quality PNCs. Fortunately, different kinds of nanoparticles (NPs) have been synthesized using ecofriendly environments, among which plant extracts have been the most outstanding reagents due to their easy handling and low cost. In addition, they do not require complex synthesis procedures involving high temperatures [51; 52]. For instance, [PERSON] and coworkers [52] have synthesized Ag NPs using _Juniperus procera_ (JP) as a bioreductor and stabilizing agent. This extract is obtained from the fresh aerial parts of the plant through a drying process, grounding step, and refluxing at 80 \({}^{\circ}\)C. After the roto evaporation step, a final dark brown extract is reached, being important to synthesize 20 nm spherically shaped JP-Ag NPs.