Effect of PEO molecular weight on sunlight induced photocatalytic activity of ZnO/PEO composites

Significance Statement

Markovic and colleagues (2016) have used the method of heterogeneous photocatalysis, as an efficient method for degradation and mineralization of pollutants present in water bodies and did some modifications. The materials used to initiate photocatalysis are the semiconductor oxides like TiO2 and ZnO. Researchers modified these semiconductor oxides so that they can become suitable for visible light photocatalysis as these oxides (TiO2 and ZnO) can absorb only UV light from the sunlight which is present in very minute percentage (~3-5%). So, they used Microwave processing (MW) method to introduce lattice defects to modify the absorption properties and visible photocatalytic activity.

The study investigated the influence of PEO molecular weight on the photocatalytic activity of ZnO/PEO nano-structured composites. ZnO nanoparticles of wurtzite structure were synthesized using MW method which generated fast crystallization of spheroidal nano-structured particles with high density of intrinsic crystal defects (oxygen vacancies and zinc interstitials). These defects helped in the absorption of visible light and enhanced the photocatalytic efficiency under direct sunlight irradiation. Further, ZnO nanoparticles composites with polyethylene oxide (PEO,  –[CH2CH2O]n–) were prepared, thus creating oxygen interstitials at the composite’s (ZnO/PEO) surface that enhanced the photocatalytic activity of MW processed ZnO.

Researchers used the PEO with molecular weight of 200,000, 600,000 and 900,000 g/mol respectively, to study its influence on photolytic efficiency of ZnO/PEO nano-composites by using the method of de-colorization of methylene blue, under direct sunlight irradiation. They found ZnO/PEO 600,000 was the most efficient composite to enhance the photolytic efficiency because by further increase in the molecular weight particles would get gelled in water suspension.

Further, the researchers investigated the phase purity and crystal structure of the composites by X-ray diffraction and Raman spectroscopy. They also studied the composite’s particles morphology and size distributions by FE-SEM and laser diffraction particle size analyzer, respectively. The optical properties were also analyzed by using UV–Vis diffuse reflectance and photoluminescence spectroscopy. They found that the ZnO and ZnO/PEO composites absorb about 50% of the incident light intensity in the wavelength range 550–800 nm. They also determine the red-shift of band gap energy (0.12–0.15 eV) compared to bulk ZnO.

Calculations based on density functional theory were performed, in order to confirm and further clarify their results. The researchers calculations confirmed that the visible light photolytic efficiency can be enhanced due to the presence of intrinsic defects that caused the band gap narrowing.

 

Effect of PEO molecular weight on sunlight induced photocatalytic activity of ZnO/PEO composites

About the author

Dr. Smilja Markovic: senior research associate at Institute of Technical Sciences of SASA, Belgrade, Serbia ([email protected] 

Smilja Markovic joined Institute of Technical Sciences of SASA, Belgrade, Serbia in 2001. She received PhD in material science from Faculty of Physical Chemistry, University of Belgrade, Serbia in 2008. For more than 15 years she developed research activity on the BaTi1-xSnxO3 functionally graded materials. Her current research interest is focused on correlation of point defects in the crystal structure of oxide ceramics such are perovskites (BaTi1-xSnxO3 and CaCu3Ti4-xRuxO12) and zinc oxide based materials (ZnO, ZnO substituted with 3d ions) with their electrical and optical properties.

Markovic is interested in testing of a biomass as a sorbent for wastewater treatment (S. Markovic, et al., Application of raw peach shell particles for removal of methylene blue, Journal of Environmental Chemical Engineering 3 (2015) 716-724). She is a highly skilled in materials characterization techniques including XRD, FTIR and Raman spectroscopy, impedance spectroscopy, particle size distribution based on laser diffraction, and DTA/DSC/TG-MS.

S. Markovic has published over 50 papers in peer-reviewed ISI journals, with citation over 460 and h-index 13, also, presented more than 100 papers at conferences. She is co-inventor of one patent registered in the Register of the Intellectual Property Office of the Republic of Serbia. 

About the author

Prof. Dr. Dragan Uskokovic was born on April 3, 1944, in Cetinje, Montenegro. He finished his studies at the Faculty of Technology and Metallurgy in 1967 in Belgrade, and in 1974 his doctoral dissertation named Study of Basic Processes Occurring during Sintering of Crystalline Materials. He started his research work at the Institute for Nuclear Sciences Vinca in 1968. In July of 1974, just before finishing his doctoral dissertation, he transferred to the Institute of Technical Sciences of the SASA. He was elected in all scientific and university titles.

He was the director of the Institute between 2001 and 2011. He is a President of Materials Research Society of Serbia (previously then 2007 known as Yugoslav Materials Research Society), which held 18 Conferences in Herceg Novi, between 1995 and 2016.

He published more than 250 articles in international periodicals, many of which in high-ranking journals, held more than 100 lectures worldwide, out of which 50 Plenary Lectures at different international conferences or world-leading research centers. Under his guidance more than 20 Master theses and the same number of Ph.D. dissertations were done. According to Scopus, his articles published in ISI publications were cited about 3300 times (h-index = 29).

About the author

Dr. Ana Stankovic, Research associate at Institute of Technical Sciences of SASA, Belgrade, Serbia ([email protected] 

Ana Stankovic joined Institute of Technical Sciences of SASA, Belgrade, Serbia in 2005. She received PhD in material science from Faculty of Physical Chemistry, University of Belgrade, Serbia in 2014.

Her research interests are: ZnO nanostructures, materials chemistry, biomaterials, biotechnology, drug delivery and physical chemistry.

 

 

Journal Reference

Smilja Marković1 , Vladimir Rajić1, Ana Stanković1, Ljiljana Veselinović1, Jelena Belošević-Čavor2, Katarina Batalović2, Nadica Abazović2, Srečo Davor Škapin3, Dragan Uskoković1. Effect of PEO molecular weight on sunlight induced photocatalytic activity of ZnO/PEO composites.  Solar Energy, Volume 127, 2016, Pages 124–135.

Show Affiliations
  1.  Institute of Technical Sciences of SASA, Knez Mihailova 35/IV, 11000 Belgrade, Serbia
  2.  The Vinča Institute of Nuclear Sciences, University of Belgrade, 11001 Belgrade, Serbia
  3.  Jožef Stefan Institute, Jamova 39, 1000 Ljubljana, Slovenia

 

 

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