Influence of framework Si/Al ratio and topology on electron transfers in zeolites.

H-ZSM-5 and H-*BEA zeolites were hydrothermally synthesized with different Si/Al ratios (∼12 to ∼40). The physico-chemical properties of the resulting materials were fully characterized by several techniques (NMR, BET, PXRD, and pyridine thermal desorption followed by infrared spectroscopy). To assess the effect of the zeolite type and Si/Al ratio on sample reactivity, the charge separation processes between the zeolite framework and the adsorbed trans-stilbene (t-St) molecule were investigated by UV-visible diffuse reflectance and FT-Raman spectroscopy. The UV-visible absorption spectra obtained after t-St adsorption show a clear difference depending on the zeolite type. It appears that the radical cation resulting from t-St spontaneous ionization is more stabilized in the MFI-type framework than in the *BEA topology. However, the amount and stability of the electron-hole pair resulting from the radical cation evolution to a charge transfer complex are more important in the *BEA zeolite. On the basis of the experimental results and physico-chemical properties of the sample, we found that the radical cation and the electron-hole stabilities are strongly dependent on the amount of hexacoordinated aluminum (Al(VI)) and more precisely on their environment, i.e. the distance between Brønsted sites and strong Lewis sites or Brønsted Strong Lewis Pairs (BSLPs).

Influence of hierarchization on electron transfers in structured MFI-type zeolites.

H-ZSM-5 zeolite (Si/Al = 19.3) was hydrothermally synthesized. Alkaline and/or acid post-synthesis treatments were carried out to give rise to an interconnected mesoporous volume. The desilication treatment parameters have been tuned (temperature, organic base addition) to obtain a series of samples with increasing mesoporous volume and a constant number of acid sites. The physico-chemical properties of the resulting materials were fully characterized by many techniques (NMR, BET, PXRD, and pyridine thermal desorption followed by infrared spectroscopy). To assess the effect of post-treatments on sample reactivity, the charge separation processes between the zeolite framework and adsorbed trans-stilbene (t-St) molecule were investigated by UV-visible diffuse reflectance. The spectra obtained after t-St adsorption show clear differences depending on the applied post-treatments. It appears that the desilication treatments performed without acidic washing highly stabilize the radical cation resulting from the t-St spontaneous ionization. In contrast, by applying acidic washing after desilication, the ionization process becomes significantly weaker. The results show that the proportion of strong Lewis acid sites in the vicinity of Brønsted sites named Brønsted Strong Lewis Pairs (BSLP), are responsible for the amount of radical cations observed in the different samples. More precisely, it exists an optimal proportion of BSLP to achieve a high ionization rate. On the basis of the experimental results a mechanism for the formation of the t-St radical cation and the charge transfer complex (CTC) is proposed.

Antigen heterogeneity of human B and T lymphocytes.

Rhesus monkeys were immunized with normal human lymphoid cells, cultured lymphoid cells, and chronic leukemic lymphocytes. Antisera were analyzed by cytotoxicity and immunofluorescence techniques to study the antigenic characteristics of human lymphocytes. In an attempt to obtain a reagent specifically reactive with T (thymus-derived) lymphocytes, an antispleen antiserum was absorbed with cellf from five B- (bone marrow-derived) cell lines. After absorption, the antiserum killed 60-75% of peripheral blood lymphocytes and 40-50% of tonsil cells, so that there was a relationship between the percentage of killed cells and the proportion of T lymphocytes. However, when cells after cytotoxic treatment were assayed for rosette formation with sheep erythrocytes (a T-cell marker) 5-20% of viable rosette-forming lymphocytes were found. Therefore, this antiserum was cytotoxic for only 75-90% of T cells. From studies performed with antisera prepared against spleen and B-cell lines, we conclude that lymphoblastoid cells are antigenically different and deficient in comparison to normal B lymphocytes. In addition, cultured B-cell lines appear to be antigenically heterogenous, as shown by the cytotoxic activity remaining in antispleen and anti-B-cell lines sera after absorption with various numbers and types of lymphoid cell lines. After absorption with normal lymphocytes, an antiserum produced against chronic lymphatic leukemia cells had specific activity associated with 12 chronic lymphatic leukemia cells tested. Absorption of the same antiserum with leukemic cells from two patients showed that a certain degree of antigenic heterogeneity also exists among chronic leukemic lymphocytes.