Abstract
The viscoelastic properties of colloidal nanoparticles (NPs) make opportunities to construct novel compounds in many different fields. The interparticle forces of inorganic particles on colloidal NPs are important for forming a mechanically stable particulate network especially the NP-based soft matter in the self-assembly process. Here, by capping with the same surface ligand L-glutathione (GSH), two semiconductor NP (CdS and PbS) controlled biomimetic nanoparticle hydrogels were obtained, namely, CdS@GSH and PbS@GSH. The dependence of viscoelasticity of colloidal suspensions on NP sizes, concentrations, and pH value has been investigated. The results show that viscoelastic properties of CdS@GSH are stronger than those of PbS@GSH because of stronger surface bonding ability of inorganic particles and GSH. The hydrogels formed by the smaller NPs demonstrate the higher stiffness due to the drastic change of GSH configurations. Unlike the CdS@GSH hydrogel system, the changes of NP concentrations and pH value had great influence on the PbS@GSH hydrogel system. The higher the proportion of water in the small particle size PbS@GSH hydrogel system, the greater the mechanical properties. The stronger the alkalinity in the large particle size PbS@GSH hydrogel system, the greater the hardness and storage modulus. Solution˗state nuclear magnetic resonance (NMR) indicated that the ligand GSH forms surface layers with different thickness varying from different coordination modes which are induced by different semiconductor NPs. Moreover, increasing the pH value of the PbS@GSH hydrogel system will dissociate the surface GSH molecules to form Pb2+ and GSH complexes which could enhance the viscoelastic properties.
Highlights
Because of the charming performance exhibited by materials as they progress from the atomic to the molecular scale and approach extended solids, soft matter fabricated from various metal and semiconductor NPs in colloidal suspensions has gained considerable attention in recent decades (Boles et al, 2016; Li et al, 2021; Mao et al, 2016; Scalise et al, 2018; Al→Johani et al, 2017; Algar et al, 2019; Love et al, 2015; Gu et al, 2021)
NPs with different inorganic core diameters (2.7 and 3.7 nm) were made by regulating the refluxing temperature and time. (After refluxing for 3 h under 105°C, CdS@GSH NPs of 2.7 nm were obtained, and CdS@GSH NPs of 3.7 nm were obtained after refluxing for 10 h under 105°C; PbS@GSH NPs of 2.7 nm were obtained after reflux for 1.5 h under 50°C, and PbS@GSH NPs of 3.7 nm were obtained after refluxing for 7.5 h under 50°C.) Aqueous dispersions of CdS and PbS NPs with sizes about 2.7 and 3.7 nm could remain stable for 24 months under −4°C
A series of NP hydrogels induced by different semiconductor NPs (CdS and PbS) capped with the same surface peptide layer of glutathione (GSH) were obtained to investigate the mechanical behavior of their corresponding gels
Summary
Because of the charming performance exhibited by materials as they progress from the atomic to the molecular scale and approach extended solids, soft matter fabricated from various metal and semiconductor NPs in colloidal suspensions has gained considerable attention in recent decades (Boles et al, 2016; Li et al, 2021; Mao et al, 2016; Scalise et al, 2018; Al→Johani et al, 2017; Algar et al, 2019; Love et al, 2015; Gu et al, 2021). The interaction between inorganic metal NP cores and surfaces is central to a broad spectrum of biological, chemical, and physical phenomena (Shavel et al, 2006; Min et al, 2008; Hens and Martins, 2013; Batista-Silvera et al, 2015; Zhou et al, 2016; Rechberger and Niederberger, 2017; Chu et al, 2018; Piveteau et al, 2018) Insight into these interactions is very important for technology realization of nanoscale synthesis and engineering the supermolecular structure of self-assembly NPs with different dimensions, collective characteristics at the nanoscale, and predictive biological responses to NPs. The viscoelasticity of gels composed of NPs with short organic ligands exhibited significant differences from that of other gels, as their mechanical behavior involves the interaction of both the surface ligands and the NP core while preserving their reconfigurability, and the relevant research and a universal model for the surface coordination of colloidal NPs were given by Zhou’s group (Zhou et al, 2018; Zhang et al, 2019). Increasing the pH value will dissociate the surface species of the PbS@GSH hydrogel system to form Pb2+ and GSH complexes which could enhance the viscoelastic properties
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