Jul. 2020: Congratulations! 

Xiaonan and Qingquan received $55,000 NSF INTERN Grant.

Explore the Nano World 

Sep. 2020: Congratulations! 

Dr. Zhang's  group received two  EPA Phase I Awards.

Sep. 2020: Congratulations! 

Dr. Zhang' received an new NSF Grant.

 Wen's Research Group​

Wen Zhang

Principal Investigator
Associate Professor

Phone: (973) 596-5520 
Fax: (973) 596-5790
Email: wen.zhang@njit.edu

Office Location: Colton Hall 211

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UV-induced aggregation of polystyrene nanoplastics: Effects of radicals, surface functional groups and electrolyte
     Researchers from Beijing Normal University and New Jersey Institute of Technology investigated the effect of UV irradiation and salts (NaCl, Na2SO4, CaCl2, and Na3PO4) on the aggregation of three polystyrene nanoparticles (PSNPs) with various surface functional groups. UV irradiation promoted the aggregation of pristine PSNPs in NaCl (> 100 mM) and amino-modified PSNPs (PSNPs-NH2) in NaCl (≥ 100 mM) or Na2SO4 (≥ 100 mM) solutions. Under UV irradiation, hydroxyl radicals (•OH) degraded the sulfate groups of PSNPs and amino groups of PSNPs-NH2 and decreased electrostatic repulsion forces among particles. The carboxyl-modified PSNPs (PSNPs-COOH) were relatively stable in NaCl and Na2SO4 solutions because of their high negative surface charge and hydrophilicity even after UV irradiation. Similarly, because the negative surface charge of PSNPs and PSNPs-NH2 in CaCl2 (1-50 mM) remained high under UV exposure, the strong electrostatic forces retarded the UV effect on the aggregation of PSNPs and PSNPs-NH2. However, UV irradiation accelerated PSNPs-COOH aggregation in CaCl2 (≥ 20 mM), probably because UV irradiation generated more carboxyl groups, which bind with Ca2+ and increase aggregation via a bridging effect. PO43- inhibited •OH photogeneration and stabilized the three types of PSNPs. Our study reveals the intriguing effects of light irradiation and salts on the aggregation behavior of emerging plastic nanoparticles in aquatic environments. 

Xinjie Wang is a PhD student at School of Environment, Beijing Normal University. She conducted this research under Yang Li and Wen Zhang’s supervision and published the results in the journal Environmental Science: Nano.