The Fabrication of Au@C Core/Shell Nanoparticles by Laser Ablation in Solutions and Their Enhancements to a Gas Sensor.

Xiaoxia Xu,Lei Gao,Guotao Duan

doi:10.3390/mi9060278

Xiaoxia Xu, Lei Gao + Show 1 more

Open Access

https://doi.org/10.3390/mi9060278

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Abstract

A convenient and flexible route is presented to fabricate gold noble metal nanoparticles wrapped with a controllable ultrathin carbon layer (Au@C) in one step based on laser ablation of the noble metal targets in toluene-ethanol mixed solutions. The obtained metal nanoparticles were <20 nm in size after ablation, and the thickness of the wrapped ultrathin carbon layer was 2 nm in a typical reaction. The size of the inner noble metal nanoparticles could be controlled by adjusting the power of laser ablation, and the thickness of the ultrathin carbon layer can be controlled from 0.6 to 2 nm by laser ablation in different components of organic solution. Then the resultant Au@C core/shell nanoparticles were modified on the surface of In2O3 films through a sol-gel technique, and the hydrogen sulfide (H2S) gas-sensing characteristics of the products were examined. Compared to pure and Au-modified In2O3, the Au@C-modified In2O3 materials exhibited a revertible and reproducible performance with good sensitivity and very low response times (few seconds) for H2S gas with a concentrations of 1 to 5 ppm at room temperature. Evidence proved that the ultrathin carbon layer played an important role in the improved H2S sensor performance. Other noble metals wrapped by the homogeneous carbon shell, such as Ag@C, could also be prepared with this method.

Highlights

Core/shell nanostructure nanocomposites, in which the inner nanoparticle is encapsulated and protected against agglomeration, adsorption, or chemical reaction by an outer shell, have attracted much attention due to their fantastic physical, chemical, biological, and catalytic properties [1,2,3]
The energy spectrum of a controllable ultrathin carbon layer (Au@C) nanoparticles is shown in the Figure S1, and it can be seen that the Au nanoparticles are coated by a carbon layer, which corresponds to the results of high-resolution transmission electron microscopy (HRTEM)
The energy spectrum of Ag nanoparticles (Ag@C) nanoparticles is shown in the Figure S5, which indicates that the Ag@C samples have been prepared successfully by the same method

Summary

Introduction

Core/shell nanostructure nanocomposites, in which the inner nanoparticle is encapsulated and protected against agglomeration, adsorption, or chemical reaction by an outer shell, have attracted much attention due to their fantastic physical, chemical, biological, and catalytic properties [1,2,3]. It is still a challenge to obtain the nanoparticles wrapped with ultrathin and homogeneous outer layers with the above methods, especially for the noble metal nanoparticles. Laser ablation of the metal targets in liquids could and effectively prepare such structure materials in only one step [12,13,14]. By two sequential processes during ablation, i.e., formation of the noble metal nanoparticles and subsequent carbon-deposition, the homogeneous and ultrathin carbon layer-wrapped noble metal nanoparticles will be obtained in one step with this method. The production with a unique structure will be an effective and excellent modifying material for application of a semiconductor metal oxide-based gas sensor. We report that modifying Au and Au@C nanoparticles prepared by laser ablation in liquid onto In2O3 film can lead to a greatly enhanced sensing sensitivity to H2S at room temperature

Experimental Section

The Gas Sensing Measurements and Characterization Methods

Results and Discussion

Conclusions