No abstract

Absorption and magnetic circular dichroism (m.c.d.) spectra of the tc polymorphic form of a series of phthalocyanines CH2Pc, Cope, NiPc and CuPc have been observed between 12000 and 40 O00 cm-'. Band shape analysis of both the absorption and m.c.d. data reveals Davydov splittings in both the Q and B (Soret) bands and suggests the existence of two T to T* transitions in the latter region. This lends support to previous assignments of the solution spectra of ZnPc. At higher energy no Davydov splittings are observed in the N band leading to a revised n + T* assignment.There is considerable interest in characterization of the electronic structure of phthalocyanines. The absorption spectra of many metallated derivates have been reported in the vapour phase,'. in various solvents 3-5 and in thin film crystals of several different solid p o l y m ~r p h s . ~' ~ Solution n.m.r.'O and m . ~. d . ~* spectra have also been published. While the vapour phase spectra can be attributed to monomeric species,2 there is evidence that in some solutions 11* l 2 and in the concentrated solid 8 p cooperative effects due to polymerization are present. When phthalocyanines are sublimed on to quartz discs, 3 distinct polymorphs can be prepared, the a, p and x These are all polymeric and exhibit spectra that are very different from the species found in solution and vapour phases. The polymorph has been shown to be a dimer.8

The photochemistry of α‐terthienyl (αT) and its mono‐ and dodo derivatives has been examined using nanosecond laser Hash photolysis techniques. The triplet states of these intermediates have been characterized, and show strong triplet‐triplet absorptions with maxima in the 450 to 490 nm region. The triplet lifetimes are normally reduced by efficient triplet‐triplet annihilation and self‐quenching both of which approach diffusion control. Triplet lifetimes in methanol obtained by extrapolation to zero laser dose and zero concentration are 30, 12.5 and 9.4 μs for αT and its mono‐ and dodo derivatives, respectively; the effect of iodo substitution on the lifetimes is attributed to heavy atom effects. The triplet states are efficiently quenched by oxygen and the electron acceptor methyl viologen, while amines tire very poor triplet quenchers. The iodo derivatives are photolabile. undergoing C‐I bond cleavage from the singlet state, a process that was studied in benzene solvent, where the complex between iodine atoms and benzene can be readily characterized. Modification of αT by replacement of the central thiophene ring by an aromatic ring (i.e. DTB) causes drastic changes in the triplet and singlet state kinetic and spectroscopic characteristics.

Commercially available quantum dots (QDs) were characterized using CE. The CE instruments were laboratory-built, each being capable of both electrokinetic and hydrodynamic injection. Modes of detection include UV absorption and LIF. The CE-LIF system was further modified to handle microliter sample volumes during injection. Sodium phosphate (5-25 mM, pH 7.5-11) was found to be a good buffer electrolyte. Sodium mercaptoproprionate CdTe/CdS (ADS620) QDs and carboxylic acid CdSe/ZnS (T2-Evitag) QDs yielded high separation efficiencies of N = 1.5x10(6) plates at t(M) = 10 min and N = 1.0x10(5) plates at t(M) = 3.8 min, respectively. Apparently the EDC/sulfo-NHS bioconjugation chemistry worked well with the neutral T2-Evitag QDs, but not so well with the negatively charged ADS620 QDs. This preliminary knowledge will serve as a basis for new CE immunoassay studies of QD-biomolecule conjugates and their immunocomplexes with target analytes.

No abstract

No abstract

No abstract

Aryl hydrocarbon hydroxylase (AHH) levels were measured in the livers of herring gull (Larus argentatus) embryos to determine if monooxygenase activity in this species could be used as a “bioeffects” monitor of environmental contamination. Herring gull eggs were collected in 1981 from five locations on the Great Lakes Basin and from one clean colony on the Atlantic coast. Microsomal protein determinations and AHH assays were conducted on livers from the embryos at 20 and 25 d of incubation. Organochlorines (DDE, DDT, tetrachlorobenzene, pentachlorobenzene, hexachlorobenzene, heptachlor epoxide, chlordane, dieldrin, mirex, photomirex, polychlorinated biphenyls and 2,3,7,8‐tetrachlorodibenzo‐p‐dioxin) were also measured in egg homogenates from each colony. The 25‐d embryos were found to be the most suitable for AHH analysis, since they had a higher baseline level and a greater response than did the 20‐d embryos. Specimens from two of the Great Lakes colonies had significantly higher AHH activities than was found for the Atlantic coast colony. These levels of AHH activity closely paralleled the concentrations of 2,3,7,8‐tetrachlorodibenzo‐p‐dioxin present in eggs gathered from the colonies in 1980. Further work regarding monooxygenase levels in herring gull embryos is discussed.