REEL Pigment Research Project

Laura Cook, Sarah Hetterscheidt, Kelli Mohr, Aroh Pandit

The Ohio State University Chemistry 123 June 1st, 2012

• The goal of the REEL research is to synthesize and characterize potential non-toxic inorganic pigments, by using XRD and UV-Vis spectroscopy.

• Our project goal was to alter the color of the pigment by varying the amount of dopant added to the ZnWO4 structure.

• It was hypothesized that the increased amount of the dopant within the structure would produce a more vibrant color in comparison to the Phase I compounds.

• The increased amount of dopant provides an increase in atoms able to absorb wavelengths in the visible light spectrum, reflecting a more vibrant color. • The more dopant added, more d-to-d transitions will occur

corresponding to the each dopant metal’s UV-Vis spectrum.(higher peaks)

• The structure of the compound was predicted to remain unchanged with the increased amount of dopant added. The dopant should merely take the place of Zinc, retaining the same structure.

Hypotheses

• In Phase I, a small amount of the dopant was added to each compound, between 5 and 10 percent of the compound.

• In Phase II, a larger amount of the dopant was added to each compound, 20 percent of the compound.

Phase I vs. Phase II

• All reactions were carried out using traditional solid state synthesis for 12 hours at 1100°C

• .95ZnO(s)+.05MnO(s)+WO3(s)Zn.95Mn.05WO4(s)

• .9ZnO(s)+.1CoO(s)+WO3(s)Zn.9Co.1WO4(s)

• .95ZnO(s) +.05NiO(s) +WO3(s) Zn.95Ni.05WO4(s)

• .95ZnO(s)+.05CuO(s)+WO3(s)Zn.95Cu.05WO4(s)

Phase I Synthesis

• All reactions were carried out using traditional solid state synthesis for 12 hours at 1100°C.

• .8ZnO(s) + .2MnO(s) + WO3(s) Zn.8Mn.2WO4(s)

• .8ZnO(s) + .2CoO(s) +WO3(s)Zn.8Co.2WO4(s)

• .8ZnO(s) + .2NiO(s) +WO3(s) Zn.8Ni.2WO4(s)

• .8ZnO(s) + .2CuO(s) + WO3(s)Zn.8Cu.2WO4(s)

Phase II Synthesis

Percent Yields

Phase II Zn.80Mn.20WO4(s)= 85.92%

Zn.80Co.20WO4(s)=98.99%

Zn.80Ni.20WO4(s)= 99.45%

Zn.80Cu.20WO4(s)= 97.97%

Phase I• Zn.95Mn.05WO4(s)= 99.72%

• Zn.90Co.10WO4(s)=93.62%

• Zn.95Ni.05WO4(s)= 92.07%

• Zn.95Cu.05WO4(s)= 95.51%

XRD Pattern Phase I

XRD Patterns Phase II

Comparison of XRD Patterns• All the peaks were accounted for by using the Jade program to compare the

patterns to known XRD patterns. • The one exception occurred with 20% Nickel doping in Phase II. There

was an error in the computer system and Zinc was unable to be identified. Based on the validity of the other substances, the doping should not have caused an error.

• Zn.8Ni.2WO4 should have shown a pattern where all the Nickel was incorporated into the existing structure.

• When doping was increased in all of the other compounds, the peaks remained accounted for. From this information, one can conclude that the dopants were integrated into the existing structure, without alteration.

• The known structure of ZnWO4 is octahedral, remaining unchanged with the dopants added.

Diffuse Reflectance UV-Vis Phase I

300 350 400 450 500 550 600 650 700 750 8000

10

20

30

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80

90

100

Phase 1 Reflectance5-10% Doping

ZnMnWO4ZnCoWO4ZnNiWO4ZnCuWO4

Wavelength (nm)

% R

efle

ctan

ce

Diffuse Reflectance UV-Vis Phase II

300 350 400 450 500 550 600 650 700 750 8000

10

20

30

40

50

60

70

80

90

100

Phase 2 Reflectance20% Doping

ZnMnWO4ZnCoWO4ZnNiWO4ZnCuWO4

Wavelength (nm)

% R

efle

ctan

ce

Comparison of Diffuse Reflectance UV-Vis

• The position of the peaks on each of the graphs remained the same between the two phases. However, the peaks shifted upward. This indicates that the color did not change, but merely the intensity of the color. • An inconsistency in data was present with the Copper dopant. This

may have been due to a failure to combine well with Tungsten Oxide. Copper has a significantly larger melting point compared to the other dopants added.

• The d-to-d transitions occurred at the same wavelengths. This is seen in the Diffuse Reflectance UV-Vis spectra as there is no horizontal shift observed.

Conclusions from the Research• The projected hypothesis was proved to be correct. The physical appearance

of each of the substances as well as the Diffuse Reflectance UV-Vis spectra point to the validity.

• Each of the appearances were brighter and more vibrant with the increased amount of the dopants. This trend was paralleled as the peaks shifted upwards in each of the Diffuse Reflectance UV-Vis spectra.

• The XRD patterns showed the peaks were accounted for, and no unaccounted phases were present. This information allows a conclusion to be drawn that the dopants were incorporated into the existing crystal structure rather than altering it.

• Two inconsistencies were observed. Firstly, an error occurred with the Jade program when producing the XRD pattern for Zn.8Ni.2WO4. Secondly, Copper produced an error in the trend of the upward shifting of the Diffuse Reflectance UV-Vis spectrum.

• In the procedure of the research, 20% dopant was added. The XRD patterns showed the dopant was able to be integrated into the existing structure. However, there is a point where too much dopant can cause an alteration of the octahedral structure.

Conclusions from the Research

ZnWO4 structure