Dye-sensitized solar cells (DSSC) have attracted considerable attention in recent years as they offer the possibility of low-cost conversion of photovoltaic energy This Review focuses on recent advances in molecular design and technological aspects of metal-free organic dyes for applications in dye-sensitized solar cells Special attention has been paid to the design principles of these dyes and on the effect of various electrolyte systems Cosensitization, an emerging technique to extend the absorption range, is also discussed as a way to improve the performance of the device In addition, we report on inverted dyes for photocathodes, which constitutes a relatively new approach for the production of tandem cells Special consideration has been paid to the correlation between the molecular structure and physical properties to their performance in DSSCs

Metal-Free Organic Dyes for Dye-Sensitized Solar Cells: From Structure: Property Relationships to Design Rules

J-aggregates are of significant interest for organic materials conceived by supramolecular approaches. Their discovery in the 1930s represents one of the most important milestones in dye chemistry as well as the germination of supramolecular chemistry. The intriguing optical properties of J-aggregates (in particular, very narrow red-shifted absorption bands with respect to those of the monomer and their ability to delocalize and migrate excitons) as well as their prospect for applications have motivated scientists to become involved in this field, and numerous contributions have been published. This Review provides an overview on the J-aggregates of a broad variety of dyes (including cyanines, porphyrins, phthalocyanines, and perylene bisimides) created by using supramolecular construction principles, and discusses their optical and photophysical properties as well as their potential applications. Thus, this Review is intended to be of interest to the supramolecular, photochemistry, and materials science communities.

J-aggregates: from serendipitous discovery to supramolecular engineering of functional dye materials.

The nonradiative conversion of light energy into heat (photothermal therapy, PTT) or sound energy (photoacoustic imaging, PAI) has been intensively investigated for the treatment and diagnosis of cancer, respectively. By taking advantage of nanocarriers, both imaging and therapeutic functions together with enhanced tumour accumulation have been thoroughly studied to improve the pre-clinical efficiency of PAI and PTT. In this review, we first summarize the development of inorganic and organic nano photothermal transduction agents (PTAs) and strategies for improving the PTT outcomes, including applying appropriate laser dosage, guiding the treatment via imaging techniques, developing PTAs with absorption in the second NIR window, increasing photothermal conversion efficiency (PCE), and also increasing the accumulation of PTAs in tumours. Second, we introduce the advantages of combining PTT with other therapies in cancer treatment. Third, the emerging applications of PAI in cancer-related research are exemplified. Finally, the perspectives and challenges of PTT and PAI for combating cancer, especially regarding their clinical translation, are discussed. We believe that PTT and PAI having noteworthy features would become promising next-generation non-invasive cancer theranostic techniques and improve our ability to combat cancers.

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Photothermal therapy and photoacoustic imaging via nanotheranostics in fighting cancer

The long wavelength (far-red to NIR) analyte-responsive fluorescent probes are advantageous for in vivo bioimaging because of minimum photo-damage to biological samples, deep tissue penetration, and minimum interference from background auto-fluorescence by biomolecules in the living systems. Thus, great interest in the development of new long wavelength analyte-responsive fluorescent probes has emerged in recent years. This review highlights the advances in the development of far-red to NIR fluorescent probes since 2000, and the probes are classified according to their organic dye platforms into various categories, including cyanines, rhodamine analogues, BODIPYs, squaraines, and other types (240 references).

Far-red to near infrared analyte-responsive fluorescent probes based on organic fluorophore platforms for fluorescence imaging

Cyanines during the 1990s: A Review

Several isolates of Trichoderma viride, isolated from different region of Allahabad district were
selected for antagonistic screening against fungal pathogens such as Rhizoctonia solani,
Sclerotium rolfsii, Macrophomina phaseolina, Alternaria alternata, Fusarium solani and
Colletotrichum capsici of Moong bean (Vigna radiata). The isolate Tr 8 showed 70%, 68.2%,
70%, 73.3%, 69.3% and 70.1% growth inhibition against R. solani, S. rolfsii, M. phaseolina, A.
alternata, F. solani and C. capsici respectively. The cell free culture filtrate of T. viride Tr 8
showed 61.5, 58.32, 63.45, 62.62% radial growth at 10% concentration against R. solani, S.
rolfsii, M. phaseolina, C. capsici respectively. While, 20% concentration observed 100%
mycelial growth inhibition. Thus, the Trichoderma viride isolate Tr 8 could be further exploited
for commercial scale up under localized climatic conditions.

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Biocontrol efficacy of Trichoderma viride isolates against fungal plant pathogens causing disease in Vigna radiata L.

Cationic dyes are known to interact with membranes and, therefore, are used as membrane probes. The alkyl chains of the dyes play a role in modifying the environment of the chromophore and affect the nature of interaction with the micelle. A number of cationic dyes with varying alkyl chains (C 1 to C 18 ) have been synthesized and their interaction with sodium dodecyl sulfate (SDS) is reported. From the absorption, fluorescence spectra and binding constant values it has been proposed that: (a) C 1 –C 8 dyes solubilize in the micelle and the chromophore occupies a methanolic/ethanolic environment, (b) C 10 –C 14 dyes exist both as an extended monomer and as folded species in presence of SDS, which is reflected in two Gaussian peaks, (c) the experimentally obtained absorption spectra for C 16 and C 18 dyes can be explained by three Gaussian peaks due to monomer ⇋ dimer in the absence of surfactant and two such peaks due to monomer and folded monomer in the presence of surfactants. The binding constant and fluorescence intensity values support this proposition.

Dye–surfactant interaction: chain folding during solubilization of styryl pyridinium dyes in sodium dodecyl sulfate aggregates

The cyanine dyes came to the limelight in 1856 [1] for their application to impart light sensitivity to silver halide emulsions in a region of the spectrum to which the silver halide is normally not sensitive Numerous applications in various areas are being published every year on this subject Now it has gained importance for their use in photodynamic therapy and in various biological activities The generic cyanine dyes consist of two nitrogen centers, one of which are positively charged and are linked by a conjugated chain of an odd number of carbon atoms to the other nitrogen ( 1 ) This has been studied as ?Push-pull? alkenes and forms the basis of the polymethine dyes, which contain the streptopolymethine unit as the chromophore These dyes are classified as cationic streptopolymethines and hemicyanines ( 1 ), anionic streptopolymethine oxonols ( 2 ), neutral streptopolymethine merocyanines ( 3 ) and zwitterionic squaraine-based cyanines ( 4 ) depending upon the charge of the streptomethine unit Generally these dyes have an all-trans geometry in their stable form These dyes undergo photo-isomerization, which can be studied by using various techniques such as flash photolysis, transient absorption, picosecond time-resolved spectroscopy, etc [2-5] The cyanines, merocyanines and squaraine dyes are substances with a variety of colors, but are not widely used for dyeing purposes, as they are decolorized by light and acid

Cyanine Dyes: Self Aggregation and Behaviour in Surfactants

The interaction of a number of cationic dyes (I) with a varying number of methylene groups (Cn) in the alkyl chain attached to pyridyl nitrogen with a cationic surfactant (CTAB) assembly is reported. The binding constant of the dyes (C5 to C18) with the micelle have been calculated, and are found to increase with increasing carbon chain. A plot of the binding constant vs. the chain length shows a curve with a maximum for C16, which is attributed to a compatibility factor. From studies of the electronic and emission spectra it is proposed that a micelle has a hydrophobic force field and that the dyes are localized in various pockets of the field.

Dye–Surfactant Interaction: Role of an Alkyl Chain in the Localization of Styrylpyridinium Dyes in a Hydrophobic Force Field of a Cationic Surfactant (CTAB)

B. K. Mishra

Papers

Cyanines during the 1990s: A Review

Biocontrol efficacy of Trichoderma viride isolates against fungal plant pathogens causing disease in Vigna radiata L.

Dye–surfactant interaction: chain folding during solubilization of styryl pyridinium dyes in sodium dodecyl sulfate aggregates

Cyanine Dyes: Self Aggregation and Behaviour in Surfactants

Dye–Surfactant Interaction: Role of an Alkyl Chain in the Localization of Styrylpyridinium Dyes in a Hydrophobic Force Field of a Cationic Surfactant (CTAB)