Rapid Catalytic Reduction of 4-Nitrophenol and Clock Reaction of Methylene Blue using Copper Nanowires.

Aina Shasha Hashimi,Sarani Zakaria,Muhammad Amirul Nazhif Mohd Nohan,Chin Hua Chia,Siew Xian Chin

doi:10.3390/nano9070936

Abstract

Copper nanowires (CuNWs) with a high aspect ratio of ~2600 have been successfully synthesized by using a facile hydrothermal method. The reductions of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) and methylene blue (MB) to leucomethylene blue (LMB) by using sodium borohydride (NaBH4) were used as models to test the catalytic activity of CuNWs. We showed that by increasing the CuNWs content, the rate of reduction increased as well. The CuNWs showed an excellent catalytic performance where 99% reduction of 4-NP to 4-AP occurred in just 60 s by using only 0.1 pg of CuNWs after treatment with glacial acetic acid (GAA). The rate constant (kapp) and activity factor (K) of this study is 18 and ~1010 fold in comparison to previous study done with no GAA treatment applied, respectively. The CuNWs showed an outstanding catalytic activity for at least ten consecutive reusability tests with a consistent result in 4-NP reduction. In clock reaction of MB, approximately 99% of reduction of MB into LMB was achieved in ~5 s by using 2 μg CuNWs. Moreover, the addition of NaOH can improve the rate and degree of recolorization of LMB to MB.

Highlights

Metal nanocrystals have attracted the attention of many researchers for the applications such as catalysts, sensors, antibacterial, and flexible and transparent electrodes [1,2,3,4,5,6,7,8]
A recent trend in nanocrystals applications is using them as nanocatalysts to treat toxic substances such as nitroaromatic compounds. 4-nitrophenol (4-NP) is an example of toxic substance that exists in industrial and agricultural wastewaters, and has been classified as a priority toxic pollutant by the U.S Environmental Protection Agency (EPA)
MB is blue when it is in an oxidizing environment and colorless as leucomethylene blue (LMB) when exposed to a reducing agent [28]

Summary

Introduction

Metal nanocrystals have attracted the attention of many researchers for the applications such as catalysts, sensors, antibacterial, and flexible and transparent electrodes [1,2,3,4,5,6,7,8]. The reduction of 4-NP by NaBH4 has become a widely used model reaction to assess catalytic properties of nanostructure materials Metals such as Au [3], Ag [13], Cu [17], and Pt [14] have been used in different shapes and sizes to reduce 4-NP. MB is blue when it is in an oxidizing environment and colorless as leucomethylene blue (LMB) when exposed to a reducing agent [28] These redox properties of MB has several uses: As an analytical indicator [29], in rewritable paper [30], and as an oxygen indicator to ensure quality control in food industries [31,32]. A facile treatment using GAA was conducted on CuNWs immobilized onto cotton cloth to improve the reusability and recoverability of the CuNWs in the catalytic reduction of 4-NP

Materials

Synthesis of CuNWs

Catalytic Reduction of 4-NP and Clock Reaction of MB Using CuNWs Strips

Characterizations

Findings

Conclusions