V.N. Karazin Kharkiv National University, Ukraine Materials Chemistry Department http://www-chemo.univer.kharkov.ua/
SILICAS WITH IMMOBILIZED XYLENOL ORANGE AND CALCEIN: PREPARATION, COMPLEXING PROPERTIES AND ANALYTICAL USE Yuriy Kholin, Sergiy Korneev, Inna Khristenko
OUTLINE Features of silica-organics hybrid materials and preparation routes; change of properties of immobilized organic reagent: affecting factors; preparation of hybrid materials wih immobilized xylenol orange and calcein; complexation equilibria and effects of energetic heterogeneity; materials wih immobilized xylenol orange and calcein in test-analysis.
Silica-organics hybrid materials Hybrid is not the sum of silica and organic modifier! Properties - high surface area, regulated capacity, possibility to set up the affinity for target species - rather favorable kinetic characteristics - powder, monolith, film, fibre Preparation routes - silanization of silica surface - post-silanization chemical modification - sol-gel synthesis - non-covalent immobilization Some target applications -sorption - analysis -catalysis - sensors
Non-covalent non-covalent immobilization Sol-gel technology Grafting on silica surface
Sol-gel synthesis: controlled hydrolysis, condensation Non-covalent immobilization Sol Reagent Gel
Main steps of sol-gel process Hydrolysis and polycondensation Initial reagents sol 1 nm 100 nm 1 µm ageing and drying gel xerogel
How immobilization of organic reagents affects their affinity to ligands? Factors: morphology, surface topography, micro-environment of fixed species, energetic heterogeneity and others Possible effects: energetic heterogeneity of reagents, cooperativity effects, uncommon composition or/and stability of immobilized complexes,
Immobilization of complexing dyes HO O O HOOCH C 2 HOOCH C 2 HOOCH C 2 HOOCH C 2 C NH 2 C 2 HO H C 3 NCH 2 2 C H CN SO H COOH 3 O CH 3 CH N CH COOH 2 CH COOH 2 CH 2COOH CH COOH 2 pk a = 2.1; 2.9; 4.1; 5.4; 10.1; 12.0 Procedure 5.0 ml TEOS, 1.5 5.0 ml 0.2-2 mm dye ethanol solution, ethanol (total volume 12 ml), catalyst(nh 4 ) 2 [SiF 6 ], formation of gel (3 4 h), drying: 10 min, power of microvawe radiation 850 W, fraction 250-500 mcm. pk a = 2.1; 2.2; 3.6; 7.3; 9.7; 12.6 Y.Kholin, S. Korneev, I. Khristenko, F. Pissetti, Y. Gushikem, Methods and Objects of Chem. Anal., 2008, V. 3, No 1.
Properties of hybrid materials Surface area Specific concentrations up to 45-90 µmol g -1 700 m 2 g -1 Leaching of dyes 0-3% Attainment of sorption equilibrium: up to 15 min
Xerogel with immobilized xylenol orange
w, % 18 16 14 12 10 8 6 4 2 0 Dependence of xylenol orange leaching (w, %) on the quantity of catalyst (NH 4 ) 2 [SiF 6 ] (n, mmol). 0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 n, mmol
Absorption spectra of immobilized calcein Im aqueous solution with рh 3.2: maxima at 454 and 474 nm F 0,8 0,6 0,4 Calcein concentrations: 0.2-0.7 µmol g -1 0,2 0,0 400 450 500 550 λ, nm
Absorption spectra of immobilized xylenol orange Aqueous solution рh 4.5-6.5: H 3 L 3- и H 4 L 2-, 432-435 nm рн > 6.5 H 2 L 4-570 580 nm F 2,0 1,6 1,2 0,8 0,4 xylenol orange concentrations: 13-27 µmol g -1 0,0 300 350 400 450 500 550 600 650 700 λ, nm
Absorption spectra of metal ion complexes with immobilized xylenol orange Aqueous solutions: at рh 5-7: λ max = 570 580 nm F 3,2 2,8 2,4 2,0 1,6 Cu(II) Pb(II) Zn(II) 1,2 0,8 0,4 0,0 300 350 400 450 500 550 600 650 700 750 800 λ, nm
Distributions of sorption centers in affinity to metal ions Xerogel xylenol orange рh 5.6-5.8 p(log β) 0,6 0,4 0,2 0,0 0,4 0,2 0,0 0,4 0,2 4,48 4,50 4,52 4,54 4,56 4,58 4,60 4,30 4,35 4,40 4,45 4,50 4,55 Adsorption of Pb(II) Adsorption of Cu(II) Adsorption of Zn(II) 0,0 4,20 4,25 4,30 4,50 4,55 4,60 4,65 log β
Visual test detection and semiquantitative determination of metal ions with the aid of xerogel with immobilized xylenol orange Colors of materials after contact with the Cu(NO 3 ) 2 solutions of different concentrations
A Fluorescence quenching of immobilized calcein at Cu(II) concentrations in solutions: 0.1 (a) 1.5 (d) mg l -1. рн = 3.5 a 0,8 b 0,4 c d 0 450 500 550 600 650 700 λ, nm
Performance characteristic curveы for detection of Cu(II) (1) and sum of equal mass concentrations of Cu(II), Zn (II) and Pb(II) (2) P(c) 1,0 ( ( c a )/ ) P( c) = 1 exp 0 b 0,8 0,6 1 P( c) exp( a0 + a1c ) = 1+ exp( a + a c) 0 1 0,4 0,2 2 0,0 0,0 0,2 0,4 0,6 0,8 1,0 1,2 1,4 c, mg l -1 1: xerogel with calcein (0.7 µmol g -1 ), 2: xerogel with xylenol orange (35 µmol g -1 ).
Metrological characteristics for procedures of visual detection of metal ions Material Sorbate Unreliability interval, mg l -1 Detection limit, mg l -1 Cu(II) 0.2 0.7 0.7 Xerogel xylenol orange Xerogel calcein Zn(II) 0.2 0.7 0.7 Pb(II) 1.2 1.9 1.9 Cu(II) + Zn(II)+ + Pb(II) 0.4 1.0 1.0 Cu(II) 0.02 1.0 1.0
Acknowledgements Colleagues in Ukraine Dr Sergiy Myerniy Prof Valentin Tertykh Colleagues in Brazil Prof Yoshitaka Gushikem Mr. Fabio Pissetti
Thank you!