Biosynthesis belongs to one of the new possibilities of nanoparticles preparation, whereas its main advantage is biocompatibility. In addition, the ability of obtaining the raw material for such synthesis from the soil environment is beneficial and could be useful for remediation. However, the knowledge of mechanisms that are necessary for the biosynthesis or effect on the bio-synthesizing organisms is still insufficient. In this study, we attempted to evaluate the effect of quantum dots (QDs) not only on a model organism of collembolans, but also on another soil organism—earthworm Eisenia fetida—and in also one widespread microorganism such as Escherichia coli. Primarily, we determined 28EC50 as 72.4 μmol L−1 for CdTe QDs in collembolans. Further, we studied the effect of QDs biosynthesis in E. fetida and E. coli. Using determination of QDs, low-molecular thiols and antioxidant activities, we found differences between both organisms and also between ways how they behave in the presence of Cd and/or Cd and Te. The biosynthesis in earthworms can be considered as its own protective mechanism; however, in E. coli, it is probably a by-product of protective mechanisms.
In the photochemical denitrogenation of 1,4‐diaryl‐2,3‐diazabicyclo[2.2.1]heptane ( AZ6 ) bearing sterically hindered substituents, a curious new absorption band at about 450 nm was observed under low‐temperature matrix conditions, together with the previously well‐characterized planar singlet diradical pl‐1 DR6 with λmax=≈580 nm. The 450 nm species was electron paramagnetic resonance (EPR)‐silent. Instead of generating the planar diradical pl‐1 DR6 and the precursor azoalkane AZ6 upon warming, the ring‐closed bicyclo[2.1.0]pentane derivative SB6 , that is, the AZ6 denitrogenation product was identified. Based on product analysis, low‐temperature spectroscopic observations, high‐level quantum‐mechanical computations, viscosity effect, and laser‐flash photolysis, the puckered singlet diradicaloid puc‐1 DR6 was assigned to the new 450 nm absorption. The latter was detected experimentally at the same time as the planar singlet diradical pl‐1 DR6 . Sterically demanding substituents as well as viscosity impediments were essential for the detection of the experimentally hitherto unknown puckered singlet cyclopentane‐1,3‐diyl diradicaloid puc‐1 DR6 , that is, the third isomer in homolysis. The present findings should stimulate future work on the mechanistically fascinating stereoselectivity documented in the formation of bicyclo[2.1.0]pentanes during the 2,3‐diazabicyclo[2.2.1]heptane denitrogenation. 相似文献
A unique class of oligothiophene‐based organogelator bearing two crown ethers at both ends was synthesized. This compound could gelatinize several organic solvents, forming one‐dimensional fibrous aggregates. From the observation of circular dichroism, it was confirmed that the helical handedness of the fibrous assembly is controllable by the chirality of 1,2bisammonium guests, thus suggesting that one guest molecule bridges two gelator molecules through the crown–ammonium interaction. Interestingly, we have found that such chirality is created by thermal gelation, whereas it disappears by thixotropic gelation. The new finding implies that the present organogel system is applicable as a reversible switching memory device, featuring memory creation by a heat mode and memory erasing by a mechanical mode. 相似文献
Electro-optic properties of polymer stabilized ferroelectric liquid crystal (PSFLC) systems are examined as a function of varying concentrations of either a linear or crosslinked thiol-ene polymer. The thiol-ene method of polymer stabilization is a drastic change from previous studies designed to avert the problem of polymer phase separation. FLC rise time and tilt angle measurements were used to determine the effects of the polymer network on the optical properties of the system. The addition of monomer impurities to both systems demonstrated a reduction in tilt angle, which translated into decreased switching speeds in both systems prior to polymerization. The crosslinked thiol-ene system showed increased switching times due to the creation of polymer in the interlayer spacing of the FLC, but exhibited minimal increase in the rotational viscosity of the system. In addition, the crosslinked polymer systems resulted in an increase in the liquid crystalline order, which produced an increase in the contrast ratio of the system. The linear polymer system showed drastically different results as compared with the crosslinked system. The rise time and tilt angle measurements decreased upon polymerization of the linear thiol-ene and the rotational viscosity and contrast ratio values also decreased. We suggest that the linear thiol-ene polymer phase separation from the interlayer spacing leads to a microscopic misalignment of the FLC molecules, causing a decrease in the optical properties of the LC. 相似文献