Patterning and Imaging of Oxides on Glassy Carbon Electrode Surfaces by Scanning Electrochemical Microscopy

The scanning electrochemical microscope is used to form and characterize patterns of oxides on glassy carbon surfaces. Chemically specific imaging of oxides present on these surfaces was demonstrated by taking advantage of differential heterogeneous electrontransfer rates for the Fe(II/III) reaction occurring at unoxidized and oxidized glassy carbon electrodes. Localized generation of surface oxides was demonstrated using both the microreagent and direct modification modes of SECM. The micro-reagent mode was used to perform a chemical oxidation of the surface by generating the strong oxidant Ag(II) at the UME tip while positioned close to the carbon surface, however, this technique was found to have poor reproducibility. Direct mode oxidation was found to be a much more versatile route toward the generation of complex patterns of oxides on carbon surfaces. The reproducibility of the direct mode technique was found to depend heavily on solution resistance. “Charge dose” studies, followed by reaction-rate imaging, qualitatively show that the electron-transfer rate for the Fe(II/III) system scales with the amount of charge “injected” in each oxidation experiment, indicating a correlation between surface oxide density and electron-transfer rate

Degradation of Insulating Glass Units: Thermal Performance, Measurements and Energy Impacts

Insulating glass unit (IGU) degradation has been studied extensively. However, there is limited understanding of how present durability evaluation standards relate to product lifetime. Furthermore, there is debate on how to quantify performance of installed windows over time to better understand degradation processes. More knowledge on these topics is required to link durability evaluation to product lifetime projections based on energy performance. Energy models provide helpful estimations of total annual building energy consumption. However, most models are based on “as installed” performance of envelope components and fail to account for performance degradation. This can lead to an underestimation of building lifetime energy consumption. A better understanding of the relationship between durability and energy performance can inform integration of degradation dynamics into energy modeling software. This will improve lifetime building energy consumption estimations as well as inform appropriate retrofit strategies and timing. This paper reviews current durability literature, various standards for window performance ratings and weathering methods, existing in situ IGU energy performance measurement techniques, and whole-building energy effects. The challenges and disparities among various studies are analyzed and discussed. The authors hope that further work in this area will lead to the development of improved in situ test methods to assess IGU degradation in the field and link this knowledge to improved energy performance modeling approaches

Photoinduced energy and charge transfer in P3HT:SWNT composites

Using steady-state photoluminescence and transient microwave conductivity (TRMC) spectroscopies, photoinduced energy and charge transfer from poly(3-hexylthiophene) (P3HT) to single-walled carbon nanotubes (SWNTs) are reported. Long-lived charge carriers are observed for excitons generated in the polymer due to interfacial electron transfer, while excitation of the SWNTs results in short-lived carriers confined to the nanotubes. The TRMC-measured mobility of electrons injected into the SWNTs exhibits a surprisingly small lower limit of 0.057 cm²/(V s), which we attribute to carrier scattering within the nanotube that inhibits resonance of the microwave electric field with the confined carriers. The observation of charge transfer and the lifetime of the separated carriers suggest that the primary photoinduced carrier generation process does not limit the performance of organic photovoltaic (OPV) devices based on P3HT:SWNT composites. With optimization, blends of P3HT with semiconducting SWNTs (s-SWNTs) may exhibit promise as an OPV active layer and could provide good solar photoconversion power efficiencies.6 page(s

Photoinduced Energy and Charge Transfer in P3HT:SWNT Composites

Using steady-state photoluminescence and transient microwave conductivity (TRMC) spectroscopies, photoinduced energy and charge transfer from poly(3-hexylthiophene) (P3HT) to single-walled carbon nanotubes (SWNTs) are reported. Long-lived charge carriers are observed for excitons generated in the polymer due to interfacial electron transfer, while excitation of the SWNTs results in short-lived carriers confined to the nanotubes. The TRMC-measured mobility of electrons injected into the SWNTs exhibits a surprisingly small lower limit of 0.057 cm²/(V s), which we attribute to carrier scattering within the nanotube that inhibits resonance of the microwave electric field with the confined carriers. The observation of charge transfer and the lifetime of the separated carriers suggest that the primary photoinduced carrier generation process does not limit the performance of organic photovoltaic (OPV) devices based on P3HT:SWNT composites. With optimization, blends of P3HT with semiconducting SWNTs (s-SWNTs) may exhibit promise as an OPV active layer and could provide good solar photoconversion power efficiencies