title: The pH sensitive properties of carboxymethyl chitosan nanoparticles cross-linked with calcium ions.
abstract: In environmental applications the applied materials are required to be non-toxic and biodegradable. Carboxymethyl chitosan nanoparticles cross-linked with Ca2+ions (CMC-Ca) fulfill these requirements, and they are also renewable. These nanoparticles were applied to oil-spill treatment in our previous study and here we focused on enhancing their properties. It was found that while the divalent Ca2+ions are crucial for the formation of the CMC-Ca, the attractive interaction between NH3+and COO-groups contributed significantly to the formation and stability of the CMC-Ca. The stability decreased as a function of pH due to the deprotonation of the amino groups. Therefore, the nanoparticles were found to be fundamentally pH sensitive in solution, if the pH deviated from the pH (7-9) that was used in the synthesis of the nanoparticles. The pH sensitive CMC-Ca synthesized in pH 7 and 8 were most stable in the studied conditions and could find applications in oil-spill treatment or controlled-release of substances.
authors.affiliation: Lappeenranta University of Technology, Sammonkatu 12, Mikkeli FI-50130, Finland. Electronic address: simo.kalliola@lut.fi.
authors.forename: Simo
authors.initials: S
authors.lastname: Kalliola
authors.affiliation: Lappeenranta University of Technology, Sammonkatu 12, Mikkeli FI-50130, Finland.
authors.forename: Eveliina
authors.initials: E
authors.lastname: Repo
authors.affiliation: Lappeenranta University of Technology, Sammonkatu 12, Mikkeli FI-50130, Finland.
authors.forename: Varsha
authors.initials: V
authors.lastname: Srivastava
authors.affiliation: Research Unit of Sustainable Chemistry, University of Oulu, P.O. Box 3000, FI-90014, Finland.
authors.forename: Juha P
authors.initials: JP
authors.lastname: Heiskanen
authors.affiliation: Fibre and Particle Engineering Research Unit, University of Oulu, P.O. Box 4300, FI-90014, Finland.
authors.forename: Juho Antti
authors.initials: JA
authors.lastname: Sirviö
authors.affiliation: Fibre and Particle Engineering Research Unit, University of Oulu, P.O. Box 4300, FI-90014, Finland.
authors.forename: Henrikki
authors.initials: H
authors.lastname: Liimatainen
authors.affiliation: Lappeenranta University of Technology, Sammonkatu 12, Mikkeli FI-50130, Finland; Department of Civil and Environmental Engineering, Florida International University, Miami, FL-33174, USA.
authors.forename: Mika
authors.initials: M
authors.lastname: Sillanpää
mesh_terms: D002118:Calcium / Q000737:chemistry*; D048271:Chitosan / Q000031:analogs & derivatives* / Q000737:chemistry; D003432:Cross-Linking Reagents / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D007477:Ions / Q000737:chemistry; D053758:Nanoparticles / Q000737:chemistry*; D010316:Particle Size; D013499:Surface Properties
chemical_list: D003432:Cross-Linking Reagents; D007477:Ions; C514968:carboxymethyl-chitosan; D048271:Chitosan; D002118:Calcium
keywords: Calcium; Carboxymethyl chitosan; Nanoparticle; pH sensitive