title: One-step, room temperature, colorimetric melamine sensing using an in-situ formation of silver nanoparticles through modified Tollens process.
abstract: We have developed a rapid, sensitive, one-step, and selective colorimetric detection method for melamine (MEL) in milk powder based upon an in-situ formation of silver nanoparticles (AgNPs) through modified Tollens process at room temperature. The triazine ring N atoms of MEL molecule were strategically designed to complex the Ag(+) through electron donor-acceptor interaction. During the AgNPs formation procedure, the MEL molecule, which has been covalently bonded with the Ag(+) ions, was adsorbed to the surface of as-prepared AgNPs, resulting in the aggregation of the adjacent AgNPs with detectable decreases of absorption signal. The concentration of MEL can be determined with the naked eye or a UV-vis spectrometer at which the yellow-to-brown color change associated with aggregate enhancement takes place. This method enables rapid (less than 30 min) and sensitive (limit of detection, LOD, 10 nM) detection, and it was also able to discriminate MEL from sixteen other milk relevant coexisting compounds. This assay does not utilize organic cosolvents, enzymatic reactions, light-sensitive dye molecules, lengthy protocols, or sophisticated instrumentation thereby overcoming some of the limitations of conventional methods.
authors.affiliation: College of Chemical Engineering, Shijiazhuang University, Shijiazhuang 050035, People's Republic of China. Electronic address: wanghuiying@sjzc.edu.cn.
authors.forename: Huiying
authors.initials: H
authors.lastname: Wang
authors.affiliation: College of Chemical Engineering, Shijiazhuang University, Shijiazhuang 050035, People's Republic of China; School of Chemistry and Chemical Engineering, Central South University, Changsha 410083, People's Republic of China. Electronic address: dlchen@csu.edu.cn.
authors.forename: Dinglong
authors.initials: D
authors.lastname: Chen
authors.affiliation: College of Chemical Engineering, Shijiazhuang University, Shijiazhuang 050035, People's Republic of China.
authors.forename: Longquan
authors.initials: L
authors.lastname: Yu
authors.affiliation: College of Chemical Engineering, Shijiazhuang University, Shijiazhuang 050035, People's Republic of China.
authors.forename: Ming
authors.initials: M
authors.lastname: Chang
authors.affiliation: College of Chemical Engineering, Shijiazhuang University, Shijiazhuang 050035, People's Republic of China.
authors.forename: Lijie
authors.initials: L
authors.lastname: Ci
mesh_terms: D000818:Animals; D002138:Calibration; D003124:Colorimetry / Q000379:methods*; D053768:Metal Nanoparticles / Q000737:chemistry*; D008892:Milk / Q000737:chemistry; D012015:Reference Standards; D012834:Silver / Q000737:chemistry*; D013056:Spectrophotometry, Ultraviolet; D013696:Temperature; D014227:Triazines / Q000032:analysis*
chemical_list: D014227:Triazines; D012834:Silver; C011907:melamine
keywords: Colorimetric; Melamine; One-step; Silver nanoparticles; Tollens process