Analysis of temporal evolution of quantum dot surface chemistry by surface-enhanced Raman scattering

Abstract

Temporal evolution of surface chemistry during oxidation of silicon quantum dot (Si-QD) surfaces were probed using surface-enhanced Raman scattering (SERS). A monolayer of hydrogen and chlorine terminated plasma-synthesized Si-QDs were spin-coated on silver oxide thin films. A clearly enhanced signal of surface modes, including Si-Clx and Si-Hx modes were observed from as-synthesized Si-QDs as a result of the plasmonic enhancement of the Raman signal at Si-QD/silver oxide interface. Upon oxidation, a gradual decrease of Si-Clx and Si-Hx modes, and an emergence of Si-Ox and Si-O-Hx modes have been observed. In addition, first, second and third transverse optical modes of Si-QDs were also observed in the SERS spectra, revealing information on the crystalline morphology of Si-QDs. An absence of any of the abovementioned spectral features, but only the first transverse optical mode of Si-QDs from thick Si-QD films validated that the spectral features observed from Si-QDs on silver oxide thin films are originated from the SERS effect. These results indicate that real-time SERS is a powerful diagnostic tool and a novel approach to probe the dynamic surface/interface chemistry of quantum dots, especially when they involve in oxidative, catalytic, and electrochemical surface/interface reactions.

Graphene Dendrimer-stabilized silver nanoparticles for detection of methimazole using Surface-enhanced Raman scattering with computational assignment

“…For example, some organophosphorus compounds, such as methylparathiol and dimethoate, that exist in pesticides were identified at the nanogram level 8 . Because water molecules scatter weakly in Raman experiments, it has made the SERS approach an attractive choice to conduct useful characterization of samples 9 10 11 .…”

Gas‐Phase Plasma Synthesis of Free‐Standing Silicon Nanoparticles for Future Energy Applications

“…For the surface chemistry analysis, Fourier transform infrared spectroscopy (FTIR) is commonly used. In a series of recent publications, we have demonstrated that Raman spectroscopy can be used as a standard diagnostic tool for the analysis of the size distribution and surface chemistry of Si‐NPs. Especially on size distribution analysis, we have shown that, Raman spectroscopy is non‐destructive and time‐efficient, and gives reliable results as the analyses agree well with other size analysis techniques like TEM and PL.…”

“…One of the mostly observed functionalization process of Si‐NPs in plasmas occurs via the coverage of nanoparticle surfaces by the dissociated atoms of the Si‐containing precursor during the synthesis. It was reported that using precursors of SiH 4 , and SiCl 4 leads to the formation of Si‐NPs covered with hydrogen and chlorine, respectively. The research demonstrated that hydrogen terminated Si‐NPs are significantly more robust against oxidation in air than chlorine terminated Si‐NP surfaces, which oxidizes almost instantly …”

Surface-enhanced Raman scattering from semiconductor and graphene quantum dots coupled to metallic-film-on-nanosphere substrates

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