The anionic cyanine dye Merocyanine 540 (MC540) dissolved in Aerosol-OT (AOT) solutions of heptane and toluene possesses a significantly higher fluorescence quantum yield and excited singlet lifetime than the acetonitrile solutions of the dye. The difference in the photophysical properties observed upon incorporation of the dye into the AOT micelles is attributed to the decrease in the photoisomerization efficiency. The presence of AOT also controls the aggregation and photosensitization behavior of MC540 adsorbed onto TiO2 semiconductor nanoparticles. MC540 adsorbed onto nanostructured TiO2 films from acetonitrile solutions contains both the aggregated and monomeric forms of the sensitizer, while the dye-modified films obtained from AOT/heptane solutions contain mainly the monomeric form of the sensitizer. Significant enhancement in the photocurrent generation efficiency has been achieved in photoelectrochemical cells using the AOT encapsulated dye films. An electroactive polymer (poly(4-vinylpyridine)) film cast on the dye-modified TiO2 electrode has been found to be effective in promoting charge mediation and minimizing dye desorption from the electrode surface. The incident photon-to-photocurrent generation efficiency (IPCE) exhibited by the monomeric form (∼40%) is nearly five times greater than the corresponding efficiency of the aggregate form (∼8%). The beneficial aspects of incorporating dyes in organized assemblies for the purpose of suppressing nonradiative decay of the excited-state sensitizer and minimizing the aggregation effects on semiconductor surfaces are discussed.

The optical properties of π-conjugated organic molecules in their solid state are critically important in determining performance efficiencies of optoelectronic devices such as organic light-emitting diodes and organic thin-film transistors. This Perspective discusses some recent systematic explorations aimed toward arriving at an understanding of the role that molecular packing plays in determining these properties.

Exhaled human breath analysis is a very promising field of research work having great potential for diagnosis of diseases in non-invasive way. Breath analysis has attracted huge attention in the field of medical diagnosis and disease monitoring in the last two decades. VOCs/gases (Volatile Organic Compounds) in exhaled breath bear the finger-prints of metabolic and biophysical processes going on in human body. It’s a non-invasive, fast, non-hazardous, cost effective, and point of care process for disease state monitoring and environmental exposure assessment in human beings. Some VOCs/gases in exhaled breath are bio-markers of different diseases and their presence in excess amount is indicative of un-healthiness. Breath analysis has the potential for early detection of diseases. However, it is still underused and commercial device is yet not available owing to multiferrious challenges. This review is intended to provide an overview of major biomarkers (VOCs/gases) present in exhaled breath, importance of their analysis towards disease monitoring, analytical techniques involved, promising materials for breath analysis etc. Finally, related challenges and limitations along with future scope will be touched upon.

A detailed study on the photophysical properties of a series of alkoxy substituted diphenylbutadienes in solution and in the solid state providing a molecular level understanding of the factors controlling their solid-state luminescence behavior is reported. Our studies provide clear evidence for exciton splitting in the solid state resulting in red-shifted emission for this class of materials. The role of the number of alkoxy substituents and the alkyl chain length in controlling the nature of the molecular packing and consequently their fluorescence properties has been elucidated. Whereas in the di-and tri-alkoxy substituted derivatives, the solid-state fluorescence was independent of the length of the alkyl chains, in the monoalkoxy substituted derivatives, increasing the length of the alkyl chain resulted in a visual change in fluorescence from green to blue. On the basis of the analysis of the molecular packing in the single crystals, this difference could be attributed to fluorescence arising from aggregates with an edge-to-face alignment in the molecules possessing short alkyl chains (methyl and butyl) to monomer fluorescence in the long alkyl chain containing derivatives.