Optical features of nanosize iron and molybdenum sulfide clusters

Conference · Sun Jan 01 04:00:00 EST 1995

OSTI ID:10116611

Wilcoxon, J P; Samara, G; Newcomer, P

In the bulk state FeS{sub 2} and MoS{sub 2} are optically opaque, narrow bandgap semiconductors and MoS{sub 2} have bandgaps that with no optical applications. We demonstrate that nanosize FeS{sub 2} can be adjusted to the visible and even UV region of the spectrum by control of the cluster size. This opens up a host of applications of these materials as inexpensive solar photocatalysts. We demonstrate that the band-gap of both materials shifts to the blue with decreasing size but ceases shifting when a size of {approximately}3 nm (in the case of MoS{sub 2}) is attained. We interpret this observation as a change from bulk quantum confinement of the hole-electron pair of a tiny semiconductor to a set of discrete molecular-like transitions more characteristic of a whopper molecule. Room temperature photoemission studies of these clusters demonstrate that, while photoemission shifts to the blue with increasing bandgap for large clusters, small clusters have photoemission exclusively from trapped sub-bandgap surface states. Chemical modification of the surface to introduce hole or electron traps can result in either an enhancement or a decrease in the photoluminescence. In addition, we report our results concerning chemical purification and preliminary surface characterization of MoS{sub 2} clusters by chromatography.

• Research Organization: Sandia National Labs., Albuquerque, NM (United States)
• Sponsoring Organization: USDOE, Washington, DC (United States)
• DOE Contract Number: AC04-94AL85000
• OSTI ID: 10116611
• Report Number(s): SAND--94-3001C; CONF-941144--49; ON: DE95005417
• Country of Publication: United States
• Language: English

Related Subjects

14 SOLAR ENERGY
140505
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400500
CHEMICAL PREPARATION
GRADED BAND GAPS
HOLES
IRON SULFIDES
MOLYBDENUM SULFIDES
OPTICAL PROPERTIES
PHOTOCHEMICAL, PHOTOBIOLOGICAL, AND THERMOCHEMICAL CONVERSION
PHOTOCHEMISTRY
PHOTOEMISSION
PHOTOLUMINESCENCE
SEMICONDUCTOR MATERIALS
SOLAR ABSORBERS
SPECTRALLY SELECTIVE SURFACES
SURFACE PROPERTIES
TRAPS