Broadband absorption and enhanced photothermal conversion property of octopod-like Ag@Ag2S core@shell structures with gradually varying shell thickness

Qian Jiang,Wenxia Zeng,Jiawei Wu,Canying Zhang,Haitao Zhu,Zhaoguo Meng,Daxiong Wu,Qunzhi Zhu

doi:10.1038/s41598-017-18220-1

Abstract

Photothermal conversion materials have promising applications in many fields and therefore they have attracted tremendous attention. However, the multi-functionalization of a single nanostructure to meet the requirements of multiple photothermal applications is still a challenge. The difficulty is that most nanostructures have specific absoprtion band and are not flexible to different demands. In the current work, we reported the synthesis and multi-band photothermal conversion of Ag@Ag2S core@shell structures with gradually varying shell thickness. We synthesized the core@shell structures through the sulfidation of Ag nanocubes by taking the advantage of their spatially different reactivity. The resulting core@shell structures show an octopod-like mopgorlogy with a Ag2S bulge sitting at each corner of the Ag nanocubes. The thickness of the Ag2S shell gradually increases from the central surface towards the corners of the structure. The synthesized core@shell structures show a broad band absorption spectrum from 300 to 1100 nm. Enhanced photothermal conversion effect is observed under the illuminations of 635, 808, and 1064 nm lasers. The results indicate that the octopod-like Ag@Ag2S core@shell structures have characteristics of multi-band photothermal conversion. The current work might provide a guidance for the design and synthesis of multifunctional photothermal conversion materials.

Highlights

Photothermal conversion (PTC) materials can absorb incident photons and generate heat
Ag nanocubes with spatially different reactivity were applied as templates, which eventually resulted in gradually varying shell thickness in the synthesized Ag@Ag2S core@shell structures
Energy dispersive X-ray spectroscopy (EDS) analysis reveals that S element is mainly located at the corner positions, while Ag element is concentrated at central part of the core@shell structures (Fig. 1g and h)

Summary

Introduction

Photothermal conversion (PTC) materials can absorb incident photons and generate heat. Wang and his co-workers found that the longitudinal plasmon wavelengths of gold nanorods can be adjusted from 520 nm to 960 nm by changing the aspect ratios of the nanorods[20] Oldenburg reported that the peak absorbance of SiO2@Au core@shell structures (120 nm cores) shifted from 550 nm to 800 nm when the shell thicknesses changed from 20 nm to 33 nm[22]. Broadband absorption can be achieved by mixing core@shell structures with different shell thicknesses. Ag nanocubes with spatially different reactivity were applied as templates, which eventually resulted in gradually varying shell thickness in the synthesized Ag@Ag2S core@shell structures. We demonstrate that Ag nanocubes can evolve into octopod-like Ag@ Ag2S core@shell structures

Methods

Results

Conclusion