Tianli Han

Three-dimensional MgSiO3-coated SnO2/C nanostructures for efficient adsorption of heavy metal ions from aqueous solution

Removal of heavy metal ions from aqueous solution for water purification through nanoadsorbents has been of great interest. However, the removal capacity and efficiency are still non-ideal due to some issues such as the agglomeration among adsorbents which severely reduces the adsorption sites. We present a potential strategy for developing adsorbents through surface modification on a specific three-dimensional (3D) nanostructure for adsorbing Pb(II) and As(V). A 3D hierarchical nanostructure which consists of a coral-like SnO2/C base and a dense MgSiO3 nanoflake coating on the surface was prepared through a two-step hydrothermal route. The 3D MgSiO3-coated SnO2/C nanostructure exhibits maximum adsorption capacities of about 185 and 109 mg g−1 to Pb(II) and As(V), respectively. Impressively, the MgSiO3-coated SnO2/C has a higher removal efficiency than the SnO2/C without MgSiO3 coating, MgSiO3 nanostructure, and the commercial active carbon. Good chemical and mechanical stability of the presented nanostructure is also confirmed by the characterization of the post-adsorbing adsorbents. In addition, a common stick coated with the presented nanoadsorbents was proposed and preliminarily used for heavy metal ion adsorption, exhibiting a promisingly simple method for water purification.

Snowflake-Shaped ZnO Nanostructures-Based Gas Sensor for Sensitive Detection of Volatile Organic Compounds

Volatile organic compounds (VOCs) have been considered severe risks to human health. Gas sensors for the sensitive detection of VOCs are highly required. However, the preparation of gas-sensing materials with a high gas diffusion performance remains a great challenge. Here, through a simple hydrothermal method accompanied with a subsequent thermal treatment, a special porous snowflake-shaped ZnO nanostructure was presented for sensitive detection of VOCs including diethyl ether, methylbenzene, and ethanol. The fabricated gas sensors exhibit a good sensing performance including high responses to VOCs and a short response/recovery time. The responses of the ZnO-based gas sensor to 100 ppm ethanol, methylbenzene, and diethyl ether are about 27, 21, and 11, respectively, while the response times to diethyl ether and methylbenzene are less than 10 seconds. The gas adsorption-desorption kinetics is also investigated, which shows that the gas-sensing behaviors to different target gases are remarkably different, making it possible for target recognition in practical applications.

A biomimetic SiO2@chitosan composite as highly-efficient adsorbent for removing heavy metal ions in drinking water

Highly efficient adsorbents for drinking water purification are demanded since the contaminants are generally in a low concentration which makes it difficult for conventional adsorbents. Herein, we present a novel biomimetic SiO2@chitosan composite as adsorbent with a high adsorption capability towards heavy metal ions including As(V) and Hg(II). The hollow leaf-like SiO2 scaffold within the adsorbent has a stable chemical property; while on the surface SiO2, the chitosan nanoparticle provide a large amount of active sites such as amino and hydroxyl groups for adsorbing heavy metal ions. The special SiO2 structure also prevents the agglomeration and loss of chitosan, which enables the efficient contact between the functional groups of chitosan and heavy metal ions. The SiO2@chitosan composite exhibits maximum adsorption capacities of 204.1 and 198.6 mg g-1 towards Hg(II) and As(V), respectively. In addition, the removal efficiency reaches over 60% within 2 min. The adsorption performance enables the presented biomimetic adsorbent suitable for adsorbing low-concentration heavy metal ions, especially possessing a promising potential for drinking water purification.

In situ gold nanoparticle-decorated three-dimensional tin dioxide nanostructures for sensitive and selective gas-sensing detection of volatile organic compounds

Sensitive and selective gas sensors for the detection of volatile organic compounds are highly desired. A composite consisting of a specific structure modified with a noble metal catalyst is considered as a promising sensing material candidate. Herein, we present a three-dimensional tin dioxide (SnO2) nanostructure in situ-decorated with gold nanoparticles (AuNPs) on the surface; this nanostructure exhibited high gas-sensing performance including high response and selectivity towards volatile organic compounds. To achieve high-loading of AuNPs, 3-aminopropyltrimethoxysilane (APTMS) functionalization was conducted on the surface of SnO2/carbonaceous precursors prior to the AuNPs growth. The vapors of volatile organic compounds, such as acetone, methanol, and hexane, were employed as analytes for gas-sensing measurements. The results show that the SnO2 nanostructures decorated with dense AuNPs exhibit remarkably better gas-sensing performance as compared to SnO2 with few AuNPs and pure SnO2. In addition, gas sensors based on three-dimensional AuNP-decorated-SnO2 showed high recognition ability towards different analytes in combination with a principal component analysis method, indicating their promising practical application for gas environment monitoring.