Physical and chemical studies of chlorophyll in microemulsions. Progress report

Technical Report · Sun Jan 01 04:00:00 EST 1978

OSTI ID:6460021

Mackay, R A

Initial studies have been designed to provide fundamental information on both the nature of photoreactions in microemulsions and the utility of these media as solvents for absorbers of solar energy. We have investigated the photoreduction of absorbed dye (methyl red and crystal violet) sensitized by chlorophyll a in an anionic mineral oil in water microemulsion. Using ascorbate as the water soluble reducing agent and pigment concentrations of less than one per drop (less than or equal to 10 ..mu..M), the reaction is found to exhibit a pseudo first order dependence on crystal violet, but a pseudo zero order dependence on methyl red. The effect of sensitizer, ascorbate concentration and light intensity on the quantum yield has also been examined. A reaction mechanism is proposed which involves the formation of a chlorophyll-dye triplet exciplex rather than any direct intermediacy of an oxidized or reduced pigment species. Based on this scheme, a number of rate constants have been estimated. Some limited photodegradation studies, as well as extension of the work to other chlorins and microemulsion systems of different charge type, have been initiated. The results show that chlorophyll a is protected from degradation by the redox couple, and that chlorophyll b and pheophytin a produce similar quantum yields. It has been found that the quantum yield increases when a drop contains two or more chlorophyll molecules, and approaches unity above three pigment molecules per drop. In summary, the available data are consistent with a mechanism which permits use of absorbers other than chlorophyll.

• Research Organization: Drexel Univ., Philadelphia, PA (USA). Dept. of Chemistry
• OSTI ID: 6460021
• Report Number(s): TID-29075
• Country of Publication: United States
• Language: English

Related Subjects

09 BIOMASS FUELS
140504 -- Solar Energy Conversion-- Biomass Production & Conversion-- (-1989)
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400500* -- Photochemistry
AMINES
AMINO ACIDS
AZO COMPOUNDS
AZO DYES
CARBOXYLIC ACIDS
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
CHLOROPHYLL
COLLOIDS
CONVERSION
DISPERSIONS
DYES
EMULSIONS
ENERGY CONVERSION
HETEROCYCLIC ACIDS
HETEROCYCLIC COMPOUNDS
INDICATORS
KINETICS
METHYL RED
METHYL VIOLET
MICROEMULSIONS
MINERAL OILS
OILS
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
OTHER ORGANIC COMPOUNDS
PHOTOCHEMICAL REACTIONS
PHYTOCHROMES
PIGMENTS
PORPHYRINS
REACTION KINETICS
REDOX REACTIONS
SOLAR ENERGY CONVERSION
TRIPHENYLMETHANE DYES