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Controlled Wet Chemical Synthesis of Multifunctional Nanomaterials: Current Status and Future Possibility
Published in Surender Kumar Sharma, Nanohybrids in Environmental & Biomedical Applications, 2019
Navadeep Shrivastava, Surender Kumar Sharma
Synthesis of Ag and/or Pt Nanoparticles: The most fundamental reactions to prepare silver nanoparticles can be divided into two groups where AgNO3 is reduced into products at a high temperature in (i) oleylamine (OAm), that is, cis-1-amino-9-octadecene and (ii) ethylene glycol (EG). These two solvents (reaction media) are helpful in understanding the nucleation and growth of Ag nanoparticles (Sun, 2013). Surfactants can be added to OAm and EG. When AgNO3 is dissolved into OAm/EG (solvents), it releases Ag+ ions which further associates with solvent or surfactant molecules (Deng et al., 2009). The solvent’s capability for reducing silver precursors depends on the reaction temperature; hence, nucleation of Ag nanoparticles can be tuned finally by tuning temperature; there is obviously not only a single factor in preparing Ag nanoparticles. Liz-Marzán and co-workers have successfully synthesized silver nanoplates in boiled N,N-dimethylformamide (DMF) containing AgNO3 and poly vinyl pyrrolidone (PVP) (Pastoriza-Santos & Liz-Marzán, 2002). They could demonstrate that tuning reaction precursor (AgNO3), hence Ag+ ions with respect to PVP has an impact on the morphology of nanoparticles as particles were showing changes from isotropic spheres to anisotropic nanowires and nanoplates on increasing Ag+ ions. The aqueous-based colloidal synthesis using CnTABr, a cationic surfactant, has attracted much attention as a simple and facile method (see Figure 1.12) that fabricates size- and shape-tunable metal nanoparticles (Zheng et al., 2014; Seo et al., 2018). Unlike other surfactants including carbonyl groups, CnTABr binds weakly to metal surfaces making it easy to regulate particle shape and preserve catalytically active sites (Zheng et al., 2014). Recently, a study was published showing a correlation between the surfactant concentration and particle size of synthesized Pt nanoparticles using cationic surfactants (CnTABr), a K2PtCl4 precursor and a NaBH4 reducing agent (Seo et al., 2018). A solution mixture of CnTABr and K2PtCl4 heated to 50˚C in an oil heat bath under stirring was formed cloudy to transparent. This cloudy compound is known as the real precursor formed by coulombic interaction between [CnTA]− and [PtBr4]2− forming [CnTA]2[PtBr4] (Sau & Murphy, 2004). Subsequently, an ice-cooled aqueous solution of NaBH4 was added as a reducing agent (Zhuang et al., 2008). The aqueous solution was kept at 50°C during the reaction for 24 h while releasing hydrogen gas in a controlled way.
The role of ligands in pressure-induced phase transition of gold nanoribbons
Published in Phase Transitions, 2021
Caihong Xing, Xingchen Liu, Li Xiao-Hong, Chang Song, Dongbo Cao, Xiaodong Wen
Experimentally, the 4H NRBs are usually stabilized with oleylamine [32, 38, 39]. Oleylamine is a molecule with an amine functional group and a long aliphatic chain. To account for both types of functional groups in oleylamine, we used methylamine and pentane with a surface coverage of 1/4 to represent the amine functional group and the aliphatic chain of oleylamine, respectively. In addition to methylamine and pentane, the role of thiol functional group to 4H NRBs was considered using a methanethiol molecule. We used a (110) slab to simulate the 4H NRBs. The slab contains five layers of metal atoms, and a vacuum layer of 15 Å in c direction to avoid the interaction between the neighboring slabs. For each molecule, we considered multiple adsorption sites and configurations and selected the structure with the lowest energy as the initial model for the subsequent phase-transition studies. The side (slightly rotated) and top view of the clean and the energetically most preferable surface adsorbed models are shown in Figure 1.
Laboratory development and evaluation of an oleylamine curing Epoxy Asphalt
Published in International Journal of Pavement Engineering, 2022
Fenglei Zhang, Lei Zhang, Xiaoxuan Guo, Dongliang Hu, Zhenyu Cai, Kai Huang
The relative molecular weight of the oleylamine curing agent used in this paper is 267 g/mol, in which the amine group contains two active hydrogen atoms, and the epoxy equivalent of the epoxy resin is 186.2 g/eq. Then taking these data into Eqs. 1 and 2, it can be obtained that the mass ratio of epoxy resin to curing agent is 58:42.