Surface-enhanced vibrational microspectroscopy of fulvic acid micelles

被引:28
作者
Alvarez-Puebla, RA [1 ]
Garrido, JJ [1 ]
Aroca, RF [1 ]
机构
[1] Univ Publ Navarra, Dept Appl Chem, E-31006 Pamplona, Spain
关键词
D O I
10.1021/ac049076u
中图分类号
O65 [分析化学];
学科分类号
070302 ; 081704 ;
摘要
Micro-Raman spectroscopy, infrared absorption microspectroscopy, and AFM images of nano- or microsized micelles formed by fulvic acid (FA) solutions, prepared at different pHs, and cast on glass slides or gold island films, are reported. FA films cast on gold islands are characterized by surface-enhanced infrared absorption (SEIRA), surface-enhanced infrared reflection absorption, and surface-enhanced Raman scattering (SERS). Based on spectral evidence, it is expected that the chemisorption of FA on gold island films takes place through thiol groups, which become more active as pH increases. The SEIRA spectra of these films show increased peak intensity, as well as improved band resolution. Microspectroscopy SERS studies show that, at pH 5, FA form small aggregates on gold surfaces. At pH 8, FA tends to expand due to electrostatic repulsion, giving rise to a fractal surface composed of different domains. SERS studies of these domains reveal that the most polar molecules are located on the external faces. At pH 11, fractal conformations are even more pronounced and give rise to radial patterned structures. At this pH, the position of fulvic acid molecules in the fractal micelles is the same as observed at pH 8. In this way, SERS can be viewed as a powerful tool for the analysis of the composition, apparent contribution of the surface functional groups of FA films, and the FA building blocks (i.e., catechol, gallic, salicylic, or ftalic acids) in the structures of these materials.
引用
收藏
页码:7118 / 7125
页数:8
相关论文
共 42 条
[1]   Chemical and spectroscopic characterization of the humic substances from sandstone-derived rock fragments [J].
Agnelli, A ;
Celi, L ;
Degl'Innocenti, A ;
Corti, G ;
Ugolini, FC .
SOIL SCIENCE, 2000, 165 (04) :314-327
[2]   Retention of Co(II), Ni(II), and Cu(II) on a purified brown humic acid. Modeling and characterization of the sorption process [J].
Alvarez-Puebla, RA ;
Valenzuela-Calahorro, C ;
Garrido, JJ .
LANGMUIR, 2004, 20 (09) :3657-3664
[3]   Cu(II) retention on a humic substance [J].
Alvarez-Puebla, RA ;
Valenzuela-Calahorro, C ;
Garrido, JJ .
JOURNAL OF COLLOID AND INTERFACE SCIENCE, 2004, 270 (01) :47-55
[4]   Modeling the adsorption and precipitation processes of Cu(II) on humin [J].
Alvarez-Puebla, RA ;
Valenzuela-Calahorro, C ;
Garrido, JJ .
JOURNAL OF COLLOID AND INTERFACE SCIENCE, 2004, 277 (01) :55-61
[5]  
[Anonymous], 1994, HUMUS CHEM GENESIS C
[6]   Molecular modeling of humic structures [J].
Bruccoleri, AG ;
Sorenson, BT ;
Langford, CH .
HUMIC SUBSTANCES: STRUCTURES, MODELS AND FUNCTIONS, 2001, (273) :193-208
[7]   Spontaneous assembly of marine dissolved organic matter into polymer gels [J].
Chin, WC ;
Orellana, MV ;
Verdugo, P .
NATURE, 1998, 391 (6667) :568-572
[8]   Adsorption and partitioning of organic compounds onto/into fractal sorbents [J].
Dachs, J ;
Eisenreich, SJ .
LANGMUIR, 2001, 17 (08) :2533-2537
[9]   Infrared, Raman, and nuclear magnetic resonance (H-1, C-13, and P-31) spectroscopy in the study of fractions of peat humic acids [J].
Francioso, O ;
SanchezCortes, S ;
Tugnoli, V ;
Ciavatta, C ;
Sitti, L ;
Gessa, C .
APPLIED SPECTROSCOPY, 1996, 50 (09) :1165-1174
[10]   Spectroscopic study of humic acids fractionated by means of tangential ultrafiltration [J].
Francioso, O ;
Sánchez-Cortés, S ;
Casarini, D ;
Garcia-Ramos, JV ;
Ciavatta, C ;
Gessa, C .
JOURNAL OF MOLECULAR STRUCTURE, 2002, 609 (1-3) :137-147