z Materials Science inc. Nanomaterials & Polymers A Simple Chemical Route toward High Surface Area CeO 2 Nanoparticles Displaying Remarkable Radical Scavenging Activity Himadri Saikia, [a] Kumar Kashyap Hazarika, [a] Bhugendra Chutia, [a] Biswajit Choudhury, [b] and Pankaj Bharali* [a] This work reports a simple chemical route to synthesize high surface area ceria (CeO 2 ) nanoparticles which exhibit remark- able radical scavenging activity. Synthesized CeO 2 nanoparticles are characterized by thermogravimetric analysis (TGA), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR) and Raman spectroscopy, scanning electron microscopy (SEM), energy-dispersive X-ray analysis (EDX), transmission electron microscopy (TEM), and Brunauer-Emmett-Teller surface area (BET surface area) analyses. The characterization results reveal the formation of cubic phase of CeO 2 with particles sizes of 10 nm and a remarkably high specific surface area of 236.8 m 2 / g. The nanoparticles are explored for 1,1-diphenyl-2-picrylhy- drazyl (DPPH) and hydroxyl radical scavenging activity that is to assess the antioxidant property of nanoceria by in-vitro spectrophotometric approach. The extensive use of cerium oxide nanoparticles (NPs), more commonly nanoceria is a well explored catalytic material used for various engineering and biological applications. [1–11] Owing to their unique redox property, cerium can exists in various oxidation states in its compounds, the + 4 state being the most common and thus cerium (IV) oxide (CeO 2 ). [12] The presence of oxygen vacancies or crystal defects in the Ce 4 + population leads to the formation of Ce 3 + state, cerium(III) oxide (Ce 2 O 3 ) i. e. there exists a cycle between Ce 4 + and Ce 3 + . This redox couple has been the main focus of researchers in the past era. [1–11] The significance of this unique and biocompatible Ce 4 + /Ce 3 + redox couple in catalysis is significant in a diverse way. [13– 16] This multifunctional well-known rare earth material with prevalent applications in the fields of catalysis, [17] electro- chemistry, [18] fuel cells, [19] energy conversion, [20] and optics, [21] have received major consideration due to their repeatable Ce 4 + /Ce 3 + redox cycles depending on the conditions and the environment. The high oxygen storage capacity (OSC) and low redox potential between Ce 4 + and Ce 3 + leads CeO 2 to promote as three-way catalyst (TWC) for simultaneous conversion of NOx, un-burnt hydrocarbons (HC) and CO to the less harmful emissions. [22–24] It is also employed for hydrogen production via two-step thermochemical water splitting. [25–26] Recently, CeO 2 NPs have been tested for their ability to serve as free-radical scavengers because of their unique redox properties and excellent biocompatibility nature to provide protection against biological and chemical harms that promote the production of free radicals. Nevertheless, nanoceria is of particular interest because, due to their high surface to volume ratio there are abundant surface cerium atoms that can participate in various redox reactions. The scavenging property of cerium ions is also recognized due to the high thermodynamic affinity for oxygen and the relative ease to undergo reversible redox reactions. [27, 28] When CeO 2 NPs enter the cells, its unique structure with respect to valence state and oxygen defects, it promotes cell longevity and decreases toxic effect. [29] The antioxidant proper- ties of CeO 2 NPs are pH-dependent. It is important that a high concentration of H + interferes with the regeneration of Ce 3 + , resulting in a loss of effectiveness of the antioxidant. [30] It is also reported that nanoceria is a regenerative radical scavenger. This makes CeO 2 unique from other nanomaterials based antiox- idant systems such as water-soluble and hydroxylated C-60 with the ability to regenerate the active Ce 3 + state for radical scavenging. [31] Superoxide, hydroxyl, peroxide, hypochlorite radicals are some common free radicals that occur in our body. There have been a good number of literature reports on the superoxide scavenging activity of CeO 2 NPs. [28, 29] However, besides superoxide other free radicals also found to play key role in various physiological processes of living organisms. [30, 31] The highly reactive hydroxyl radical ( * OH) virtually damage all types of macromolecules such as carbohydrates, lipids, nucleic acids, amino acids, etc. in the human body. This destructive exploit of * OH radical has been concerned with several health problems including neurological diseases and other chronic inflammations. [32–34] Hydroxyl radicals cannot be eliminated through enzymatic reaction, which is in contrast to superoxide [a] H. Saikia, K. K. Hazarika, B. Chutia, Dr. P. Bharali Department of Chemical Sciences Tezpur University Napaam 784 028, India Tel.: + 91 3712 275064 Fax: + 91 3712 267005 E-mail: pankajb@tezu.ernet.in [b] Dr. B. Choudhury Physical Sciences Division, Institute of Advanced Study in Science and Technology, Paschim Boragaon, Garchuk, Guwahati 781 035, India Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/slct.201700354 Full Papers DOI: 10.1002/slct.201700354 3369 ChemistrySelect 2017, 2, 3369 – 3375 # 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim