title: Triplex blue-shifting hydrogen bonds of ClO4(-)···H-C in the nanointerlayer of montmorillonite complexed with cetyltrimethylammonium cation from hydrophilic to hydrophobic properties.
abstract: In this study, molecular interactions of perchlorate (ClO4(-)), an emerging pollutant, with cetyltrimethylammonium(CTMA(+)) complexed in the nanointerlayer of negatively charged montmorillonite were characterized using the zeta potentials, FTIR, Raman, and XRD spectroscopy and quantified using quantum mechanical calculations and sorption experiments. We found that blue-shifting hydrogen bonds assisted in the uptake of ClO4(-) from water into the nanointerlayer spacing of CTMA(+)-montmorillonite and were tunable according to CTMA(+) loading. FTIR spectra presented an obvious 47 cm(-1) blue shift in the C-H vibration coming from the N-terminal methyl group of CTMA(+) when ClO4(-) was absorbed. Quantum mechanical calculations based on density functional theory demonstrated that triplex blue-shifting hydrogen bonds of C-H···O were formed between the three terminal methyl groups of CTMA(+) and three oxygen atoms of ClO4(-). The contribution of blue-shifting hydrogen bonds to perchlorate uptake switched from a ClO4(-)/CTMA(+) ratio of 0.0453 at low CTMA(+) loadings to a ClO4(-)/CTMA(+) ratio of 0.2563 (5.6-fold) at high CTMA(+) loadings, which can be ascribed to the evolution of the nanointerlayer microenvironments from hydrophilic properties to hydrophobic properties. The blue-shifting hydrogen bond of C-H···O that is tunable with the hydrophobic nature of the organic phase should be recognized to elucidate the biochemical behavior of perchlorate in organisms.
authors.affiliation: Department of Environmental Science, Zhejiang University , Hangzhou, Zhejiang 310058, China; Zhejiang Provincial Key Laboratory of Organic Pollutant Process and Control, Zhejiang University , Hangzhou Zhejiang 310058, China.
authors.forename: Qile
authors.initials: Q
authors.lastname: Fang
authors.forename: Baoliang
authors.initials: B
authors.lastname: Chen
authors.forename: Shulin
authors.initials: S
authors.lastname: Zhuang
mesh_terms: D001546:Bentonite / Q000737:chemistry*; D000077286:Cetrimonium; D002593:Cetrimonium Compounds / Q000737:chemistry*; D006860:Hydrogen Bonding; D057927:Hydrophobic and Hydrophilic Interactions; D010472:Perchlorates / Q000737:chemistry*
chemical_list: D002593:Cetrimonium Compounds; D010472:Perchlorates; D001546:Bentonite; C494474:perchlorate; D000077286:Cetrimonium