Brevet Julien, Claret Francis, Reiller Pascal E
Université d'Evry Val d'Essonne, Laboratoire Analyse et Environnement pour la Biologie et l'Environnement, CNRS UMR 8587, Bâtiment Maupertuis, F-91025 Evry Cedex, France.
Spectrochim Acta A Mol Biomol Spectrosc. 2009 Oct 1;74(2):446-53. doi: 10.1016/j.saa.2009.06.042. Epub 2009 Jun 25.
Although a high heterogeneity of composition is awaited for humic substances, their complexation properties do not seem to greatly depend on their origins. The information on the difference in the structure of these complexes is scarce. To participate in the filling of this lack, a study of the spectral and temporal evolution of the Eu(III) luminescence implied in humic substance (HS) complexes is presented. Seven different extracts, namely Suwannee River fulvic acid (SRFA) and humic acid (SRHA), and Leonardite HA (LHA) from the International Humic Substances Society (USA), humic acid from Gorleben (GohyHA), and from the Kleiner Kranichsee bog (KFA, KHA) from Germany, and purified commercial Aldrich HA (PAHA), were made to contact with Eu(III). Eu(III)-HS time-resolved luminescence properties were compared with aqueous Eu(3+) at pH 5. Using an excitation wavelength of 394 nm, the typical bi-exponential luminescence decay for Eu(III)-HS complexes is common to all the samples. The components tau(1) and tau(2) are in the same order of magnitude for all the samples, i.e., 40 <or= tau(1) (micros) <or= 60, and 145 <or= tau(2) (micros) <or= 190, but significantly different. It is shown that different spectra are obtained from the different groups of samples. Terrestrial extract on the one hand, i.e. LHA/GohyHA, plus PAHA, and purely aquatic extracts on the other hand, i.e., SRFA/SRHA/KFA/KHA, induce inner coherent luminescent properties of Eu(III) within each group. The (5)D(0) --> (7)F(2) transition exhibits the most striking differences. A slight blue shift is observed compared to aqueous Eu(3+) (lambda(max) = 615.4 nm), and the humic samples share almost the same lambda(max) approximately 614.5 nm. The main differences between the samples reside in a shoulder around lambda approximately 612.5 nm, modelled by a mixed Gaussian-Lorentzian band around lambda approximately 612 nm. SRFA shows the most intense shoulder with an intensity ratio of I(612.5)/I(614.7) = 1.1, KFA/KHA/SRHA share almost the same ratio I(612.5)/I(614.7) = 1.2-1.3, whilst the LHA/GohyHA/PAHA group has a I(612.5)/I(614.5) = 1.5-1.6. This shows that for the two groups of complexes, despite comparable complexing properties, slightly different symmetries are awaited.
尽管腐殖质的组成具有高度异质性，但它们的络合特性似乎并不很大程度上取决于其来源。关于这些络合物结构差异的信息很少。为了填补这一空白，本文对腐殖质（HS）络合物中铕（III）发光的光谱和时间演化进行了研究。制备了七种不同的提取物，即来自美国国际腐殖质协会的苏万尼河富里酸（SRFA）和腐殖酸（SRHA）、勒拿河腐殖酸（LHA）、来自德国戈勒本的腐殖酸（GohyHA）、来自德国克莱纳克兰尼希湖沼泽的腐殖酸（KFA、KHA）以及纯化的商业Aldrich腐殖酸（PAHA），使其与铕（III）接触。将铕（III）-HS的时间分辨发光特性与pH值为5的水溶液中铕（3+）的特性进行了比较。使用394nm的激发波长，铕（III）-HS络合物典型的双指数发光衰减在所有样品中都很常见。所有样品的组分τ1和τ2处于相同的数量级，即40≤τ1（微秒）≤60，145≤τ2（微秒）≤190，但有显著差异。结果表明，不同组的样品获得了不同的光谱。一方面是陆地提取物，即LHA/GohyHA加上PAHA，另一方面是纯水生提取物，即SRFA/SRHA/KFA/KHA，每组内铕（III）呈现出内在一致的发光特性。（5）D0→（7）F2跃迁表现出最显著的差异。与水溶液中铕（3+）（λmax=615.4nm）相比，观察到轻微的蓝移，腐殖质样品的λmax几乎相同，约为614.5nm。样品之间的主要差异在于约612.5nm处的一个肩峰，由约612nm处的混合高斯-洛伦兹带模拟。SRFA的肩峰最强，强度比I（612.5）/I（614.7）=1.1，KFA/KHA/SRHA的强度比几乎相同，I（612.5）/I（614.7）=1.2 - 1.3，而LHA/GohyHA/PAHA组的I（612.5）/I（614.5）=1.5 - 1.6。这表明对于这两组络合物，尽管络合特性相当，但预计对称性会略有不同。
