Subscriber access provided by BUFFALO STATE
C: Physical Processes in Nanomaterials and Nanostructures
ZnO Nanocrystal Coated Zinc Particles Degrade Dyes in Dark by Constantly Releasing .O and HO 2-
2
2
Guangshun Yi, Gunjan Agarwal, and Yugen Zhang J. Phys. Chem. C, Just Accepted Manuscript • DOI: 10.1021/acs.jpcc.9b05393 • Publication Date (Web): 15 Jul 2019 Downloaded from pubs.acs.org on July 20, 2019
Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.
is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.
Page 1 of 7 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
The Journal of Physical Chemistry
ZnO Nanocrystal Coated Zinc Particles Degrade Dyes in Dark by Constantly Releasing .O2- and H2O2 Guangshun Yi*, Gunjan Agarwal and Yugen Zhang* Institute of Bioengineering and Nanotechnology, 31 Biopolis Way, The Nanos, Singapore 138669, Singapore ABSTRACT: Photoactive semiconductors as dye degradation catalysts play an important role in various industries. These materials rely on external stimulus of photo irradiation to generate reactive oxygen species (ROS), which limit the practical application in real environments. Herein, a simple ZnO nanocrystal coated zinc particles is proven to continuously generate ROS in the absence of external energy input (in dark). The core/shell structured Zn/ZnO showed excellent dye degradation capability, which can degrade a series of dyes (cresol purple, methylene blue, methyl orange, rhodamine B, phenol red, and alizarin red) in water. Further study showed that Zn/ZnO constantly generates .O2- radicals and H2O2 which degrade dyes. The mechanism for the generation of ROS in the dark was proposed through zinc corrosion and electron transfer process. This new material provides a potential solution to general waste water treatment and drinking water purification.
INTRODUCTION The degradation or mineralization of organic pollutant in water is a major challenge worldwide. For example, organic dyes, which are extensively used in industries such as textile, leather, paper, paint, printing inks, plastics, food, drugs, automobile, furniture, and cosmetics, are released into water bodies, resulting in high level of Chemical Oxygen Demand (COD) even after treatment. More than 79105 metric tonnes of dye stuffs are produced worldwide annually, with 10-50% of this amount being released into wastewater.1 Fenton degradation using H2O2 to generate .OH radicals via iron catalyst is a clean and efficient organic waste degradation method.2, 3 However, large amount of H2O2 will be consumed which are costly and have transportation and storage issues.4 Photo-degradation with semiconductor-based photo-catalysts is another promising solution, where reactive oxygen species (ROS) are generated under photoexcitation.5-9 For example, as typical wide-band-gap semiconductors, wurtzite ZnO and anatase TiO2 have been widely used as photo-catalysts under ultraviolet (UV) irradiation.1 Artificial UV light sources tend to be expensive, and the UV light component in sunlight reaching the surface of the earth is a relatively small (ca. 35%). Recent efforts have been focused on exploring means to utilize the inexpensive visible light for treating polluted waters.10-17 Many research groups have attempted to reduce the band gap of wide band gap semiconductors from UV region to visible region in order to harvest maximum region of solar spectrum.18 Such attempts include doping/co-doping with metal/non-metal ions,17, 19 compositing with activated carbon/CNT/fullerenes/graphene20-22 and coupling with narrow band gap semiconductors.23,24 Compared to photo-catalytic dye degradation, catalytic dye degradation without light irritation was rare. 24, 25 For example, Rajagopalan et al recently reported a new nanocomposite of ZnO2/polypyrrole (ppy), which can degrade methylene blue and rhodamine B in the dark.24 This degradation process is driven by consumption of zinc peroxide (ZnO2). In fact, the degradation of organic contamination in dark has urgent
demand for point-of-use (POU) drinking water and field applications, especially in developing countries.26 Metals can donate electrons to metal oxide semiconductors by a self-corrosive process.27-30 Recently we have reported a simple antibacterial Zn/ZnO core/shell composite which release ROS in dark. In this system, the involved zeta potentials over NHE are: Zn/Zn2+ = -0.76 V,31 O2/.O2- = +0.07 V,32 .O2-/H2O2 = +0.36 eV,32 ECB (ZnO) = -0.15 eV.5 Electrons are donated from Zn to ZnO (CB) and reducing oxygen molecules to generate radicals.5, 33, 34 The whole system does not rely on external stimulus. We have found that this composite has much better antibacterial property as compared to Zn and ZnO, respectively, which is due to the releasing of ROS (.O2- and H2O2).30 Beside bacteria contamination, organic waste is another major pollutant in water. Herein, ZnO nanocrystal coated zinc particle has been prepared and used for various dye degradation in dark and superior dye degradation capability for a wide range of dyes was demonstrated. MATERIALS AND METHODS Materials. Zinc powders (
