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Diss Factsheets

Physical & Chemical properties

Nanomaterial radical formation potential

Administrative data

nanomaterial radical formation potential
Type of information:
experimental study
Adequacy of study:
key study
4 (not assignable)
Rationale for reliability incl. deficiencies:
other: Limited documentation of the full study report was available. Based on the provided data no further conclusion could be achieved.

Data source

Reference Type:
study report
Report date:

Materials and methods

Test guideline
no guideline followed
Principles of method if other than guideline:
The photocatalytic activity of materials refers to their ability to create electron-hole pairs under light irradiation, which then generate reactive oxygen species (ROS) such as free radicals (e.g. superoxide radicals, hydroxyl radicals, etc.), hydrogen peroxide, singlet oxygen, etc.
GLP compliance:
Details on methods and data evaluation:
- Irradiation was performed on groups of 40 microcentrifuge tubes. The tubes were placed vertically under the centre of the lamp of the solar simulator, on an in-house made polystyrene holder, their cups having been removed.
- The samples were subjected to 10min periods of irradiation, followed by 5min period of non-irradiation to reduce sample overheating.
- After each 10 min period, 1x3 samples for each NP/media combination and controls were removed from the irradiations.
- Samples irradiated for 0 min, 10 min, 20 min, 30 min, 40 min and 60 min were collected for each NP/media combination and controls.
- The samples containing NPs

Test material

Constituent 1
Chemical structure
Reference substance name:
Zinc oxide
EC Number:
EC Name:
Zinc oxide
Cas Number:
Molecular formula:
Test material form:
solid: nanoform

Data gathering

1kW Solar Simulator (Newport Corporation, Stratford, CT)
Lambda 850 UV-Vis spectrometer
Plate-reader Victor 1420 multilabel counter (Perkin Elmer)
The instrument wavelength calibration was checked using Holmium glass standards (Serial # 9393,Starna Scientific,
Hainault, Uk)

Results and discussion

Any other information on results incl. tables

Absorbance readings at 352 nm after being irradiated with solar simulator at 1000 W/m2, for 60 minutes.

Applicant's summary and conclusion

Executive summary:

NPL, 2010 investigated the radical formation potential. The test items were dispersed in four different media in the presence of KI (deionized water, seawater, daphnia and fish media) and the dispersions were exposed for 60 minutes, under 1000 W/m2 white light irradiation. Anatase (TiO2) was used as positive control. Results showed that there was a certain level of tri-iodide (I3-) measured in the irradiated sample. Tri-iodide was suppressed in seawater and may be attributed to a higher concentration of ions in this media. Results for Anatase (TiO2), being the most active photocatalytic material, show a much higher rate of tri-iodide formation than the corresponding zinc oxide NMs. In particular, the absorbance signal was highest in deionized water, lower in daphnia and fish media and when in seawater, the absorbance signal was reduced (as in the corresponding blank i.e. seawater with no Anatase). It was shown that the absorbance signal of NM 111 is much higher in seawater than when dispersed in the other three media. In the course of the present study no explanation was found. In general, for the ZnO nanomaterials the absorbance signals were within a similar range to that of the corresponding irradiated blank (Samples that were kept in the dark exhibited no absorption peak at 352 nm) indicating no differences Radical formation potential between bulk and nano ZnO.