Culture experiments with the estuarine diatom Thalassiosira pseudonana (clone 3H) in highly chelated seawater media demonstrate that growth rate inhibition and copper content of cells are related to cupric ion activity, and not to total copper concentration. Cupric ion activity was altered independently of total copper concentration by varying the chelator concentration, and the pH. Cellular copper content (moles/ cell) of 3 to 4 day old cultures followed a hyperbolic relation with cupric ion activity: 4.8 X 10• Gou Cu/cell = acu + 10 0.2 where a ou is the cupric ion activity. Copper inhibited growth rate at activities above 3 X 10-u M and growth ceased at values above 5 X 10--0 M; however, the relation between growth rate inhibition and cupric ion activity was not a simple hyperbolic function. In experiments with the estuarine green alga Nannochloris atomus (clone GSB nanno), growth rate inhibition also was related to cupric ion activity with partial growth rate inhibition occuring in the activity range 4 X 10-u to 2 X 10--0 M. Calculated estimates of cupric ion activity in seawater indicate that natural activity levels can be inhibitory to these phytoplankton depending on pH and the degree of copper complexation by natural organic ligands.

The relationship between cupric ion activity and the toxicity of copper to phytoplankton [Thalassiosira pseudonana, Nannochloris atomus, Algae]

Photolysis of Fe (III)-hydroxy complexes as sources of OH radicals in clouds, fog and rain

A π-conjugated Lewis base is introduced into perovskite solar cells, namely, indacenodithiophene end-capped with 1.1-dicyanomethylene-3-indanone (IDIC), as a multifunctional interlayer, which combines efficient trap-passivation and electron-extraction. Perovskite solar cells with IDIC layers yield higher photovoltages and photocurrents, and 45% enhanced efficiency compared with control devices without IDIC.

π-Conjugated Lewis Base: Efficient Trap-Passivation and Charge-Extraction for Hybrid Perovskite Solar Cells

Manganese porphyrin complexes

The role of transition metal complexes is overviewed for the iron, copper and chromium compounds, for which photoreactivity is of crucial environmental importance. Attention is paid to these complex systems, in which metal centres are photoreduced by organic matter under solar irradiation and re-oxidized by molecular oxygen, i.e. to the systems, that play a part in the environmental photocatalysis. The photoreduction is accompanied by simultaneous oxidation of organic matter, which plays a role of ligand and/or sacrificial electron donor. Under favourable conditions a complete photodegradation of the organic pollutants can be achieved. The general mechanisms are analysed and examples of different photocatalytic behaviours are presented in some details. The systems are more sophisticated due to concurrent generation of active oxygen species, such as the O 2 − , HO 2 , OH , H 2 O 2 , and HO 2 − , which are involved in the redox reactions of the photocatalytic cycling and influence the pollutant degradation. Beside the monometallic cycles, the mixed metal systems can function in nature. The cooperation between the photocatalytic cycles of two metals can abate diverse environmental pollutants, but their efficiency can be either higher or lower in comparison with that of the sum of single cycles.

Donald W. Watts

Papers

Photochemistry of transition-metal coordination compounds