Metal Nanoparticles Regulated By Biothiols And Their Catalytic Performance

The combination of biotechnology and nanotechnology is an emerging research hotspot in the field of nanomaterials.Biomolecules have intriguing prospects in the regulation of the growth,the physicochemical properties and the catalytic performance of metal nanomaterials.In this study,four biothiols were employed as the nucleation templates to synthesize Pd and Pt NPs.It is the frst report to comparatively study the physicochemical properties of NPs synthesized by biothiols with different chemical structures.Their applications in coupling reaction and biological detection were also deeply investigated.Firstly,a series of biothiols involving N-acetyl-L-cysteine(NAC),penicillamine(PEN),homocysteine(Hcys)and cysteine(Cys),were chosen as the nucleation templates to synthesize Pd nanocatalysts for Suzuki coupling reaction.Through the characterizations of UV–vis and FT-IR,it is demonstrated that Pd(II)can coordinate with biothiols mainly through thiol,amino/amido and carboxyl groups.NAC molecules are capable of generating uniform Pd NPs with the size distribution from 2.2 to 3.3 nm.At the[Na₂Pd Cl₄]/[biothiol]of 6,NAC-and Hcys-stabilized Pd displays spherical particles with the average size of 3.3 and 3.6 nm respectively,whereas Cys-and PEN-capped Pd exhibit worm-like morphology with poor dispersion.NAC-capped Pd NPs with the mean diameter of 3.3 nm and the Pd⁰ proportion of 63%,show highly active in Suzuki cross-coupling between iodobenzene and phenylboronic acid,with the turn over frequency(TOF)of 38625 mol biphenyl(mol Pd×h)^-1 in Et OH/water=1:2 at60°C.Next,NAC was employed as the nucleation template to synthesize a series of peroxidase-like Pt NPs with distinct physicochemical properties.Through the characterizations of UV-vis spectroscopy,HRTEM,XPS and enzyme kinetics,it is demonstrated that the particle size and the charge state of NAC-Pt NPs are highly dependent upon the molar ratio of[K₂Pt Cl₄]/[NAC],contributing to different peroxidase mimicking activities.The most active Pt nanozyme(?1.7 nm),composed of59.5%metallic Pt⁰,exhibits the K_m of 0.132 m M toward 3,3',5,5'-tetramethylbenzidine(TMB)and 35 m M toward H₂O₂.Based on the heparin-enhanced enzymatic activity of NAC-Pt at p H 6,an ultrasensitive test was established for quantitative determination of heparin,giving the linear response of 0.5?20?g/m L as well as the limit of detection of2×10^-3?g/m L.This quantitative method is also applicable in biological fluid for practical applications.Such a colorimetric method possesses several advantages involving high sensitivity,short response,eco-friendly synthesis,low consumption of material and energy,free of expensive instrument as well as simple operation.